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Diffstat (limited to 'gnu/gcc2/lib/loop.c')
| -rw-r--r-- | gnu/gcc2/lib/loop.c | 6508 |
1 files changed, 0 insertions, 6508 deletions
diff --git a/gnu/gcc2/lib/loop.c b/gnu/gcc2/lib/loop.c deleted file mode 100644 index ad82384c148f..000000000000 --- a/gnu/gcc2/lib/loop.c +++ /dev/null @@ -1,6508 +0,0 @@ -/* Move constant computations out of loops. - Copyright (C) 1987, 1988, 1989, 1991, 1992 Free Software Foundation, Inc. - -This file is part of GNU CC. - -GNU CC is free software; you can redistribute it and/or modify -it under the terms of the GNU General Public License as published by -the Free Software Foundation; either version 2, or (at your option) -any later version. - -GNU CC is distributed in the hope that it will be useful, -but WITHOUT ANY WARRANTY; without even the implied warranty of -MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the -GNU General Public License for more details. - -You should have received a copy of the GNU General Public License -along with GNU CC; see the file COPYING. If not, write to -the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */ - - -/* This is the loop optimization pass of the compiler. - It finds invariant computations within loops and moves them - to the beginning of the loop. Then it identifies basic and - general induction variables. Strength reduction is applied to the general - induction variables, and induction variable elimination is applied to - the basic induction variables. - - It also finds cases where - a register is set within the loop by zero-extending a narrower value - and changes these to zero the entire register once before the loop - and merely copy the low part within the loop. - - Most of the complexity is in heuristics to decide when it is worth - while to do these things. */ - -#include <stdio.h> -#include "config.h" -#include "rtl.h" -#include "obstack.h" -#include "expr.h" -#include "insn-config.h" -#include "insn-flags.h" -#include "regs.h" -#include "hard-reg-set.h" -#include "recog.h" -#include "flags.h" -#include "real.h" -#include "loop.h" - -/* Vector mapping INSN_UIDs to luids. - The luids are like uids but increase monotonically always. - We use them to see whether a jump comes from outside a given loop. */ - -int *uid_luid; - -/* Indexed by INSN_UID, contains the ordinal giving the (innermost) loop - number the insn is contained in. */ - -int *uid_loop_num; - -/* 1 + largest uid of any insn. */ - -int max_uid_for_loop; - -/* 1 + luid of last insn. */ - -static int max_luid; - -/* Number of loops detected in current function. Used as index to the - next few tables. */ - -static int max_loop_num; - -/* Indexed by loop number, contains the first and last insn of each loop. */ - -static rtx *loop_number_loop_starts, *loop_number_loop_ends; - -/* For each loop, gives the containing loop number, -1 if none. */ - -int *loop_outer_loop; - -/* Indexed by loop number, contains a nonzero value if the "loop" isn't - really a loop (an insn outside the loop branches into it). */ - -static char *loop_invalid; - -/* Indexed by loop number, links together all LABEL_REFs which refer to - code labels outside the loop. Used by routines that need to know all - loop exits, such as final_biv_value and final_giv_value. - - This does not include loop exits due to return instructions. This is - because all bivs and givs are pseudos, and hence must be dead after a - return, so the presense of a return does not affect any of the - optimizations that use this info. It is simpler to just not include return - instructions on this list. */ - -rtx *loop_number_exit_labels; - -/* Holds the number of loop iterations. It is zero if the number could not be - calculated. Must be unsigned since the number of iterations can - be as high as 2^wordsize-1. For loops with a wider iterator, this number - will will be zero if the number of loop iterations is too large for an - unsigned integer to hold. */ - -unsigned HOST_WIDE_INT loop_n_iterations; - -/* Nonzero if there is a subroutine call in the current loop. - (unknown_address_altered is also nonzero in this case.) */ - -static int loop_has_call; - -/* Nonzero if there is a volatile memory reference in the current - loop. */ - -static int loop_has_volatile; - -/* Added loop_continue which is the NOTE_INSN_LOOP_CONT of the - current loop. A continue statement will generate a branch to - NEXT_INSN (loop_continue). */ - -static rtx loop_continue; - -/* Indexed by register number, contains the number of times the reg - is set during the loop being scanned. - During code motion, a negative value indicates a reg that has been - made a candidate; in particular -2 means that it is an candidate that - we know is equal to a constant and -1 means that it is an candidate - not known equal to a constant. - After code motion, regs moved have 0 (which is accurate now) - while the failed candidates have the original number of times set. - - Therefore, at all times, == 0 indicates an invariant register; - < 0 a conditionally invariant one. */ - -static short *n_times_set; - -/* Original value of n_times_set; same except that this value - is not set negative for a reg whose sets have been made candidates - and not set to 0 for a reg that is moved. */ - -static short *n_times_used; - -/* Index by register number, 1 indicates that the register - cannot be moved or strength reduced. */ - -static char *may_not_optimize; - -/* Nonzero means reg N has already been moved out of one loop. - This reduces the desire to move it out of another. */ - -static char *moved_once; - -/* Array of MEMs that are stored in this loop. If there are too many to fit - here, we just turn on unknown_address_altered. */ - -#define NUM_STORES 20 -static rtx loop_store_mems[NUM_STORES]; - -/* Index of first available slot in above array. */ -static int loop_store_mems_idx; - -/* Nonzero if we don't know what MEMs were changed in the current loop. - This happens if the loop contains a call (in which case `loop_has_call' - will also be set) or if we store into more than NUM_STORES MEMs. */ - -static int unknown_address_altered; - -/* Count of movable (i.e. invariant) instructions discovered in the loop. */ -static int num_movables; - -/* Count of memory write instructions discovered in the loop. */ -static int num_mem_sets; - -/* Number of loops contained within the current one, including itself. */ -static int loops_enclosed; - -/* Bound on pseudo register number before loop optimization. - A pseudo has valid regscan info if its number is < max_reg_before_loop. */ -int max_reg_before_loop; - -/* This obstack is used in product_cheap_p to allocate its rtl. It - may call gen_reg_rtx which, in turn, may reallocate regno_reg_rtx. - If we used the same obstack that it did, we would be deallocating - that array. */ - -static struct obstack temp_obstack; - -/* This is where the pointer to the obstack being used for RTL is stored. */ - -extern struct obstack *rtl_obstack; - -#define obstack_chunk_alloc xmalloc -#define obstack_chunk_free free - -extern char *oballoc (); - -/* During the analysis of a loop, a chain of `struct movable's - is made to record all the movable insns found. - Then the entire chain can be scanned to decide which to move. */ - -struct movable -{ - rtx insn; /* A movable insn */ - rtx set_src; /* The expression this reg is set from. */ - rtx set_dest; /* The destination of this SET. */ - rtx dependencies; /* When INSN is libcall, this is an EXPR_LIST - of any registers used within the LIBCALL. */ - int consec; /* Number of consecutive following insns - that must be moved with this one. */ - int regno; /* The register it sets */ - short lifetime; /* lifetime of that register; - may be adjusted when matching movables - that load the same value are found. */ - short savings; /* Number of insns we can move for this reg, - including other movables that force this - or match this one. */ - unsigned int cond : 1; /* 1 if only conditionally movable */ - unsigned int force : 1; /* 1 means MUST move this insn */ - unsigned int global : 1; /* 1 means reg is live outside this loop */ - /* If PARTIAL is 1, GLOBAL means something different: - that the reg is live outside the range from where it is set - to the following label. */ - unsigned int done : 1; /* 1 inhibits further processing of this */ - - unsigned int partial : 1; /* 1 means this reg is used for zero-extending. - In particular, moving it does not make it - invariant. */ - unsigned int move_insn : 1; /* 1 means that we call emit_move_insn to - load SRC, rather than copying INSN. */ - unsigned int is_equiv : 1; /* 1 means a REG_EQUIV is present on INSN. */ - enum machine_mode savemode; /* Nonzero means it is a mode for a low part - that we should avoid changing when clearing - the rest of the reg. */ - struct movable *match; /* First entry for same value */ - struct movable *forces; /* An insn that must be moved if this is */ - struct movable *next; -}; - -FILE *loop_dump_stream; - -/* Forward declarations. */ - -static void find_and_verify_loops (); -static void mark_loop_jump (); -static void prescan_loop (); -static int reg_in_basic_block_p (); -static int consec_sets_invariant_p (); -static rtx libcall_other_reg (); -static int labels_in_range_p (); -static void count_loop_regs_set (); -static void note_addr_stored (); -static int loop_reg_used_before_p (); -static void scan_loop (); -static void replace_call_address (); -static rtx skip_consec_insns (); -static int libcall_benefit (); -static void ignore_some_movables (); -static void force_movables (); -static void combine_movables (); -static int rtx_equal_for_loop_p (); -static void move_movables (); -static void strength_reduce (); -static int valid_initial_value_p (); -static void find_mem_givs (); -static void record_biv (); -static void check_final_value (); -static void record_giv (); -static void update_giv_derive (); -static int basic_induction_var (); -static rtx simplify_giv_expr (); -static int general_induction_var (); -static int consec_sets_giv (); -static int check_dbra_loop (); -static rtx express_from (); -static int combine_givs_p (); -static void combine_givs (); -static int product_cheap_p (); -static int maybe_eliminate_biv (); -static int maybe_eliminate_biv_1 (); -static int last_use_this_basic_block (); -static void record_initial (); -static void update_reg_last_use (); - -/* Relative gain of eliminating various kinds of operations. */ -int add_cost; -#if 0 -int shift_cost; -int mult_cost; -#endif - -/* Benefit penalty, if a giv is not replaceable, i.e. must emit an insn to - copy the value of the strength reduced giv to its original register. */ -int copy_cost; - -void -init_loop () -{ - char *free_point = (char *) oballoc (1); - rtx reg = gen_rtx (REG, word_mode, 0); - rtx pow2 = GEN_INT (32); - rtx lea; - int i; - - add_cost = rtx_cost (gen_rtx (PLUS, word_mode, reg, reg), SET); - - /* We multiply by 2 to reconcile the difference in scale between - these two ways of computing costs. Otherwise the cost of a copy - will be far less than the cost of an add. */ - - copy_cost = 2 * 2; - - /* Free the objects we just allocated. */ - obfree (free_point); - - /* Initialize the obstack used for rtl in product_cheap_p. */ - gcc_obstack_init (&temp_obstack); -} - -/* Entry point of this file. Perform loop optimization - on the current function. F is the first insn of the function - and DUMPFILE is a stream for output of a trace of actions taken - (or 0 if none should be output). */ - -void -loop_optimize (f, dumpfile) - /* f is the first instruction of a chain of insns for one function */ - rtx f; - FILE *dumpfile; -{ - register rtx insn; - register int i; - rtx end; - rtx last_insn; - - loop_dump_stream = dumpfile; - - init_recog_no_volatile (); - init_alias_analysis (); - - max_reg_before_loop = max_reg_num (); - - moved_once = (char *) alloca (max_reg_before_loop); - bzero (moved_once, max_reg_before_loop); - - regs_may_share = 0; - - /* Count the number of loops. */ - - max_loop_num = 0; - for (insn = f; insn; insn = NEXT_INSN (insn)) - { - if (GET_CODE (insn) == NOTE - && NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG) - max_loop_num++; - } - - /* Don't waste time if no loops. */ - if (max_loop_num == 0) - return; - - /* Get size to use for tables indexed by uids. - Leave some space for labels allocated by find_and_verify_loops. */ - max_uid_for_loop = get_max_uid () + 1 + max_loop_num * 32; - - uid_luid = (int *) alloca (max_uid_for_loop * sizeof (int)); - uid_loop_num = (int *) alloca (max_uid_for_loop * sizeof (int)); - - bzero (uid_luid, max_uid_for_loop * sizeof (int)); - bzero (uid_loop_num, max_uid_for_loop * sizeof (int)); - - /* Allocate tables for recording each loop. We set each entry, so they need - not be zeroed. */ - loop_number_loop_starts = (rtx *) alloca (max_loop_num * sizeof (rtx)); - loop_number_loop_ends = (rtx *) alloca (max_loop_num * sizeof (rtx)); - loop_outer_loop = (int *) alloca (max_loop_num * sizeof (int)); - loop_invalid = (char *) alloca (max_loop_num * sizeof (char)); - loop_number_exit_labels = (rtx *) alloca (max_loop_num * sizeof (rtx)); - - /* Find and process each loop. - First, find them, and record them in order of their beginnings. */ - find_and_verify_loops (f); - - /* Now find all register lifetimes. This must be done after - find_and_verify_loops, because it might reorder the insns in the - function. */ - reg_scan (f, max_reg_num (), 1); - - /* See if we went too far. */ - if (get_max_uid () > max_uid_for_loop) - abort (); - - /* Compute the mapping from uids to luids. - LUIDs are numbers assigned to insns, like uids, - except that luids increase monotonically through the code. - Don't assign luids to line-number NOTEs, so that the distance in luids - between two insns is not affected by -g. */ - - for (insn = f, i = 0; insn; insn = NEXT_INSN (insn)) - { - last_insn = insn; - if (GET_CODE (insn) != NOTE - || NOTE_LINE_NUMBER (insn) <= 0) - uid_luid[INSN_UID (insn)] = ++i; - else - /* Give a line number note the same luid as preceding insn. */ - uid_luid[INSN_UID (insn)] = i; - } - - max_luid = i + 1; - - /* Don't leave gaps in uid_luid for insns that have been - deleted. It is possible that the first or last insn - using some register has been deleted by cross-jumping. - Make sure that uid_luid for that former insn's uid - points to the general area where that insn used to be. */ - for (i = 0; i < max_uid_for_loop; i++) - { - uid_luid[0] = uid_luid[i]; - if (uid_luid[0] != 0) - break; - } - for (i = 0; i < max_uid_for_loop; i++) - if (uid_luid[i] == 0) - uid_luid[i] = uid_luid[i - 1]; - - /* Create a mapping from loops to BLOCK tree nodes. */ - if (flag_unroll_loops && write_symbols != NO_DEBUG) - find_loop_tree_blocks (); - - /* Now scan the loops, last ones first, since this means inner ones are done - before outer ones. */ - for (i = max_loop_num-1; i >= 0; i--) - if (! loop_invalid[i] && loop_number_loop_ends[i]) - scan_loop (loop_number_loop_starts[i], loop_number_loop_ends[i], - max_reg_num ()); - - /* If debugging and unrolling loops, we must replicate the tree nodes - corresponding to the blocks inside the loop, so that the original one - to one mapping will remain. */ - if (flag_unroll_loops && write_symbols != NO_DEBUG) - unroll_block_trees (); -} - -/* Optimize one loop whose start is LOOP_START and end is END. - LOOP_START is the NOTE_INSN_LOOP_BEG and END is the matching - NOTE_INSN_LOOP_END. */ - -/* ??? Could also move memory writes out of loops if the destination address - is invariant, the source is invariant, the memory write is not volatile, - and if we can prove that no read inside the loop can read this address - before the write occurs. If there is a read of this address after the - write, then we can also mark the memory read as invariant. */ - -static void -scan_loop (loop_start, end, nregs) - rtx loop_start, end; - int nregs; -{ - register int i; - register rtx p; - /* 1 if we are scanning insns that could be executed zero times. */ - int maybe_never = 0; - /* 1 if we are scanning insns that might never be executed - due to a subroutine call which might exit before they are reached. */ - int call_passed = 0; - /* For a rotated loop that is entered near the bottom, - this is the label at the top. Otherwise it is zero. */ - rtx loop_top = 0; - /* Jump insn that enters the loop, or 0 if control drops in. */ - rtx loop_entry_jump = 0; - /* Place in the loop where control enters. */ - rtx scan_start; - /* Number of insns in the loop. */ - int insn_count; - int in_libcall = 0; - int tem; - rtx temp; - /* The SET from an insn, if it is the only SET in the insn. */ - rtx set, set1; - /* Chain describing insns movable in current loop. */ - struct movable *movables = 0; - /* Last element in `movables' -- so we can add elements at the end. */ - struct movable *last_movable = 0; - /* Ratio of extra register life span we can justify - for saving an instruction. More if loop doesn't call subroutines - since in that case saving an insn makes more difference - and more registers are available. */ - int threshold; - /* If we have calls, contains the insn in which a register was used - if it was used exactly once; contains const0_rtx if it was used more - than once. */ - rtx *reg_single_usage = 0; - - n_times_set = (short *) alloca (nregs * sizeof (short)); - n_times_used = (short *) alloca (nregs * sizeof (short)); - may_not_optimize = (char *) alloca (nregs); - - /* Determine whether this loop starts with a jump down to a test at - the end. This will occur for a small number of loops with a test - that is too complex to duplicate in front of the loop. - - We search for the first insn or label in the loop, skipping NOTEs. - However, we must be careful not to skip past a NOTE_INSN_LOOP_BEG - (because we might have a loop executed only once that contains a - loop which starts with a jump to its exit test) or a NOTE_INSN_LOOP_END - (in case we have a degenerate loop). - - Note that if we mistakenly think that a loop is entered at the top - when, in fact, it is entered at the exit test, the only effect will be - slightly poorer optimization. Making the opposite error can generate - incorrect code. Since very few loops now start with a jump to the - exit test, the code here to detect that case is very conservative. */ - - for (p = NEXT_INSN (loop_start); - p != end - && GET_CODE (p) != CODE_LABEL && GET_RTX_CLASS (GET_CODE (p)) != 'i' - && (GET_CODE (p) != NOTE - || (NOTE_LINE_NUMBER (p) != NOTE_INSN_LOOP_BEG - && NOTE_LINE_NUMBER (p) != NOTE_INSN_LOOP_END)); - p = NEXT_INSN (p)) - ; - - scan_start = p; - - /* Set up variables describing this loop. */ - prescan_loop (loop_start, end); - threshold = (loop_has_call ? 1 : 2) * (1 + n_non_fixed_regs); - - /* If loop has a jump before the first label, - the true entry is the target of that jump. - Start scan from there. - But record in LOOP_TOP the place where the end-test jumps - back to so we can scan that after the end of the loop. */ - if (GET_CODE (p) == JUMP_INSN) - { - loop_entry_jump = p; - - /* Loop entry must be unconditional jump (and not a RETURN) */ - if (simplejump_p (p) - && JUMP_LABEL (p) != 0 - /* Check to see whether the jump actually - jumps out of the loop (meaning it's no loop). - This case can happen for things like - do {..} while (0). If this label was generated previously - by loop, we can't tell anything about it and have to reject - the loop. */ - && INSN_UID (JUMP_LABEL (p)) < max_uid_for_loop - && INSN_LUID (JUMP_LABEL (p)) >= INSN_LUID (loop_start) - && INSN_LUID (JUMP_LABEL (p)) < INSN_LUID (end)) - { - loop_top = next_label (scan_start); - scan_start = JUMP_LABEL (p); - } - } - - /* If SCAN_START was an insn created by loop, we don't know its luid - as required by loop_reg_used_before_p. So skip such loops. (This - test may never be true, but it's best to play it safe.) - - Also, skip loops where we do not start scanning at a label. This - test also rejects loops starting with a JUMP_INSN that failed the - test above. */ - - if (INSN_UID (scan_start) >= max_uid_for_loop - || GET_CODE (scan_start) != CODE_LABEL) - { - if (loop_dump_stream) - fprintf (loop_dump_stream, "\nLoop from %d to %d is phony.\n\n", - INSN_UID (loop_start), INSN_UID (end)); - return; - } - - /* Count number of times each reg is set during this loop. - Set may_not_optimize[I] if it is not safe to move out - the setting of register I. If this loop has calls, set - reg_single_usage[I]. */ - - bzero (n_times_set, nregs * sizeof (short)); - bzero (may_not_optimize, nregs); - - if (loop_has_call) - { - reg_single_usage = (rtx *) alloca (nregs * sizeof (rtx)); - bzero (reg_single_usage, nregs * sizeof (rtx)); - } - - count_loop_regs_set (loop_top ? loop_top : loop_start, end, - may_not_optimize, reg_single_usage, &insn_count, nregs); - - for (i = 0; i < FIRST_PSEUDO_REGISTER; i++) - may_not_optimize[i] = 1, n_times_set[i] = 1; - bcopy (n_times_set, n_times_used, nregs * sizeof (short)); - - if (loop_dump_stream) - { - fprintf (loop_dump_stream, "\nLoop from %d to %d: %d real insns.\n", - INSN_UID (loop_start), INSN_UID (end), insn_count); - if (loop_continue) - fprintf (loop_dump_stream, "Continue at insn %d.\n", - INSN_UID (loop_continue)); - } - - /* Scan through the loop finding insns that are safe to move. - Set n_times_set negative for the reg being set, so that - this reg will be considered invariant for subsequent insns. - We consider whether subsequent insns use the reg - in deciding whether it is worth actually moving. - - MAYBE_NEVER is nonzero if we have passed a conditional jump insn - and therefore it is possible that the insns we are scanning - would never be executed. At such times, we must make sure - that it is safe to execute the insn once instead of zero times. - When MAYBE_NEVER is 0, all insns will be executed at least once - so that is not a problem. */ - - p = scan_start; - while (1) - { - p = NEXT_INSN (p); - /* At end of a straight-in loop, we are done. - At end of a loop entered at the bottom, scan the top. */ - if (p == scan_start) - break; - if (p == end) - { - if (loop_top != 0) - p = NEXT_INSN (loop_top); - else - break; - if (p == scan_start) - break; - } - - if (GET_RTX_CLASS (GET_CODE (p)) == 'i' - && find_reg_note (p, REG_LIBCALL, NULL_RTX)) - in_libcall = 1; - else if (GET_RTX_CLASS (GET_CODE (p)) == 'i' - && find_reg_note (p, REG_RETVAL, NULL_RTX)) - in_libcall = 0; - - if (GET_CODE (p) == INSN - && (set = single_set (p)) - && GET_CODE (SET_DEST (set)) == REG - && ! may_not_optimize[REGNO (SET_DEST (set))]) - { - int tem1 = 0; - int tem2 = 0; - int move_insn = 0; - rtx src = SET_SRC (set); - rtx dependencies = 0; - - /* Figure out what to use as a source of this insn. If a REG_EQUIV - note is given or if a REG_EQUAL note with a constant operand is - specified, use it as the source and mark that we should move - this insn by calling emit_move_insn rather that duplicating the - insn. - - Otherwise, only use the REG_EQUAL contents if a REG_RETVAL note - is present. */ - temp = find_reg_note (p, REG_EQUIV, NULL_RTX); - if (temp) - src = XEXP (temp, 0), move_insn = 1; - else - { - temp = find_reg_note (p, REG_EQUAL, NULL_RTX); - if (temp && CONSTANT_P (XEXP (temp, 0))) - src = XEXP (temp, 0), move_insn = 1; - if (temp && find_reg_note (p, REG_RETVAL, NULL_RTX)) - { - src = XEXP (temp, 0); - /* A libcall block can use regs that don't appear in - the equivalent expression. To move the libcall, - we must move those regs too. */ - dependencies = libcall_other_reg (p, src); - } - } - - /* Don't try to optimize a register that was made - by loop-optimization for an inner loop. - We don't know its life-span, so we can't compute the benefit. */ - if (REGNO (SET_DEST (set)) >= max_reg_before_loop) - ; - /* In order to move a register, we need to have one of three cases: - (1) it is used only in the same basic block as the set - (2) it is not a user variable and it is not used in the - exit test (this can cause the variable to be used - before it is set just like a user-variable). - (3) the set is guaranteed to be executed once the loop starts, - and the reg is not used until after that. */ - else if (! ((! maybe_never - && ! loop_reg_used_before_p (set, p, loop_start, - scan_start, end)) - || (! REG_USERVAR_P (SET_DEST (PATTERN (p))) - && ! REG_LOOP_TEST_P (SET_DEST (PATTERN (p)))) - || reg_in_basic_block_p (p, SET_DEST (PATTERN (p))))) - ; - else if ((tem = invariant_p (src)) - && (dependencies == 0 - || (tem2 = invariant_p (dependencies)) != 0) - && (n_times_set[REGNO (SET_DEST (set))] == 1 - || (tem1 - = consec_sets_invariant_p (SET_DEST (set), - n_times_set[REGNO (SET_DEST (set))], - p))) - /* If the insn can cause a trap (such as divide by zero), - can't move it unless it's guaranteed to be executed - once loop is entered. Even a function call might - prevent the trap insn from being reached - (since it might exit!) */ - && ! ((maybe_never || call_passed) - && may_trap_p (src))) - { - register struct movable *m; - register int regno = REGNO (SET_DEST (set)); - - /* A potential lossage is where we have a case where two insns - can be combined as long as they are both in the loop, but - we move one of them outside the loop. For large loops, - this can lose. The most common case of this is the address - of a function being called. - - Therefore, if this register is marked as being used exactly - once if we are in a loop with calls (a "large loop"), see if - we can replace the usage of this register with the source - of this SET. If we can, delete this insn. - - Don't do this if P has a REG_RETVAL note or if we have - SMALL_REGISTER_CLASSES and SET_SRC is a hard register. */ - - if (reg_single_usage && reg_single_usage[regno] != 0 - && reg_single_usage[regno] != const0_rtx - && regno_first_uid[regno] == INSN_UID (p) - && (regno_last_uid[regno] - == INSN_UID (reg_single_usage[regno])) - && n_times_set[REGNO (SET_DEST (set))] == 1 - && ! side_effects_p (SET_SRC (set)) - && ! find_reg_note (p, REG_RETVAL, NULL_RTX) -#ifdef SMALL_REGISTER_CLASSES - && ! (GET_CODE (SET_SRC (set)) == REG - && REGNO (SET_SRC (set)) < FIRST_PSEUDO_REGISTER) -#endif - /* This test is not redundant; SET_SRC (set) might be - a call-clobbered register and the life of REGNO - might span a call. */ - && ! modified_between_p (SET_SRC (set), p, - reg_single_usage[regno]) - && validate_replace_rtx (SET_DEST (set), SET_SRC (set), - reg_single_usage[regno])) - { - /* Replace any usage in a REG_EQUAL note. */ - REG_NOTES (reg_single_usage[regno]) - = replace_rtx (REG_NOTES (reg_single_usage[regno]), - SET_DEST (set), SET_SRC (set)); - - PUT_CODE (p, NOTE); - NOTE_LINE_NUMBER (p) = NOTE_INSN_DELETED; - NOTE_SOURCE_FILE (p) = 0; - n_times_set[regno] = 0; - continue; - } - - m = (struct movable *) alloca (sizeof (struct movable)); - m->next = 0; - m->insn = p; - m->set_src = src; - m->dependencies = dependencies; - m->set_dest = SET_DEST (set); - m->force = 0; - m->consec = n_times_set[REGNO (SET_DEST (set))] - 1; - m->done = 0; - m->forces = 0; - m->partial = 0; - m->move_insn = move_insn; - m->is_equiv = (find_reg_note (p, REG_EQUIV, NULL_RTX) != 0); - m->savemode = VOIDmode; - m->regno = regno; - /* Set M->cond if either invariant_p or consec_sets_invariant_p - returned 2 (only conditionally invariant). */ - m->cond = ((tem | tem1 | tem2) > 1); - m->global = (uid_luid[regno_last_uid[regno]] > INSN_LUID (end) - || uid_luid[regno_first_uid[regno]] < INSN_LUID (loop_start)); - m->match = 0; - m->lifetime = (uid_luid[regno_last_uid[regno]] - - uid_luid[regno_first_uid[regno]]); - m->savings = n_times_used[regno]; - if (find_reg_note (p, REG_RETVAL, NULL_RTX)) - m->savings += libcall_benefit (p); - n_times_set[regno] = move_insn ? -2 : -1; - /* Add M to the end of the chain MOVABLES. */ - if (movables == 0) - movables = m; - else - last_movable->next = m; - last_movable = m; - - if (m->consec > 0) - { - /* Skip this insn, not checking REG_LIBCALL notes. */ - p = NEXT_INSN (p); - /* Skip the consecutive insns, if there are any. */ - p = skip_consec_insns (p, m->consec); - /* Back up to the last insn of the consecutive group. */ - p = prev_nonnote_insn (p); - - /* We must now reset m->move_insn, m->is_equiv, and possibly - m->set_src to correspond to the effects of all the - insns. */ - temp = find_reg_note (p, REG_EQUIV, NULL_RTX); - if (temp) - m->set_src = XEXP (temp, 0), m->move_insn = 1; - else - { - temp = find_reg_note (p, REG_EQUAL, NULL_RTX); - if (temp && CONSTANT_P (XEXP (temp, 0))) - m->set_src = XEXP (temp, 0), m->move_insn = 1; - else - m->move_insn = 0; - - } - m->is_equiv = (find_reg_note (p, REG_EQUIV, NULL_RTX) != 0); - } - } - /* If this register is always set within a STRICT_LOW_PART - or set to zero, then its high bytes are constant. - So clear them outside the loop and within the loop - just load the low bytes. - We must check that the machine has an instruction to do so. - Also, if the value loaded into the register - depends on the same register, this cannot be done. */ - else if (SET_SRC (set) == const0_rtx - && GET_CODE (NEXT_INSN (p)) == INSN - && (set1 = single_set (NEXT_INSN (p))) - && GET_CODE (set1) == SET - && (GET_CODE (SET_DEST (set1)) == STRICT_LOW_PART) - && (GET_CODE (XEXP (SET_DEST (set1), 0)) == SUBREG) - && (SUBREG_REG (XEXP (SET_DEST (set1), 0)) - == SET_DEST (set)) - && !reg_mentioned_p (SET_DEST (set), SET_SRC (set1))) - { - register int regno = REGNO (SET_DEST (set)); - if (n_times_set[regno] == 2) - { - register struct movable *m; - m = (struct movable *) alloca (sizeof (struct movable)); - m->next = 0; - m->insn = p; - m->set_dest = SET_DEST (set); - m->dependencies = 0; - m->force = 0; - m->consec = 0; - m->done = 0; - m->forces = 0; - m->move_insn = 0; - m->partial = 1; - /* If the insn may not be executed on some cycles, - we can't clear the whole reg; clear just high part. - Not even if the reg is used only within this loop. - Consider this: - while (1) - while (s != t) { - if (foo ()) x = *s; - use (x); - } - Clearing x before the inner loop could clobber a value - being saved from the last time around the outer loop. - However, if the reg is not used outside this loop - and all uses of the register are in the same - basic block as the store, there is no problem. - - If this insn was made by loop, we don't know its - INSN_LUID and hence must make a conservative - assumption. */ - m->global = (INSN_UID (p) >= max_uid_for_loop - || (uid_luid[regno_last_uid[regno]] - > INSN_LUID (end)) - || (uid_luid[regno_first_uid[regno]] - < INSN_LUID (p)) - || (labels_in_range_p - (p, uid_luid[regno_first_uid[regno]]))); - if (maybe_never && m->global) - m->savemode = GET_MODE (SET_SRC (set1)); - else - m->savemode = VOIDmode; - m->regno = regno; - m->cond = 0; - m->match = 0; - m->lifetime = (uid_luid[regno_last_uid[regno]] - - uid_luid[regno_first_uid[regno]]); - m->savings = 1; - n_times_set[regno] = -1; - /* Add M to the end of the chain MOVABLES. */ - if (movables == 0) - movables = m; - else - last_movable->next = m; - last_movable = m; - } - } - } - /* Past a call insn, we get to insns which might not be executed - because the call might exit. This matters for insns that trap. - Call insns inside a REG_LIBCALL/REG_RETVAL block always return, - so they don't count. */ - else if (GET_CODE (p) == CALL_INSN && ! in_libcall) - call_passed = 1; - /* Past a label or a jump, we get to insns for which we - can't count on whether or how many times they will be - executed during each iteration. Therefore, we can - only move out sets of trivial variables - (those not used after the loop). */ - /* This code appears in three places, once in scan_loop, and twice - in strength_reduce. */ - else if ((GET_CODE (p) == CODE_LABEL || GET_CODE (p) == JUMP_INSN) - /* If we enter the loop in the middle, and scan around to the - beginning, don't set maybe_never for that. This must be an - unconditional jump, otherwise the code at the top of the - loop might never be executed. Unconditional jumps are - followed a by barrier then loop end. */ - && ! (GET_CODE (p) == JUMP_INSN && JUMP_LABEL (p) == loop_top - && NEXT_INSN (NEXT_INSN (p)) == end - && simplejump_p (p))) - maybe_never = 1; - /* At the virtual top of a converted loop, insns are again known to - be executed: logically, the loop begins here even though the exit - code has been duplicated. */ - else if (GET_CODE (p) == NOTE - && NOTE_LINE_NUMBER (p) == NOTE_INSN_LOOP_VTOP) - maybe_never = call_passed = 0; - } - - /* If one movable subsumes another, ignore that other. */ - - ignore_some_movables (movables); - - /* For each movable insn, see if the reg that it loads - leads when it dies right into another conditionally movable insn. - If so, record that the second insn "forces" the first one, - since the second can be moved only if the first is. */ - - force_movables (movables); - - /* See if there are multiple movable insns that load the same value. - If there are, make all but the first point at the first one - through the `match' field, and add the priorities of them - all together as the priority of the first. */ - - combine_movables (movables, nregs); - - /* Now consider each movable insn to decide whether it is worth moving. - Store 0 in n_times_set for each reg that is moved. */ - - move_movables (movables, threshold, - insn_count, loop_start, end, nregs); - - /* Now candidates that still are negative are those not moved. - Change n_times_set to indicate that those are not actually invariant. */ - for (i = 0; i < nregs; i++) - if (n_times_set[i] < 0) - n_times_set[i] = n_times_used[i]; - - if (flag_strength_reduce) - strength_reduce (scan_start, end, loop_top, - insn_count, loop_start, end); -} - -/* Add elements to *OUTPUT to record all the pseudo-regs - mentioned in IN_THIS but not mentioned in NOT_IN_THIS. */ - -void -record_excess_regs (in_this, not_in_this, output) - rtx in_this, not_in_this; - rtx *output; -{ - enum rtx_code code; - char *fmt; - int i; - - code = GET_CODE (in_this); - - switch (code) - { - case PC: - case CC0: - case CONST_INT: - case CONST_DOUBLE: - case CONST: - case SYMBOL_REF: - case LABEL_REF: - return; - - case REG: - if (REGNO (in_this) >= FIRST_PSEUDO_REGISTER - && ! reg_mentioned_p (in_this, not_in_this)) - *output = gen_rtx (EXPR_LIST, VOIDmode, in_this, *output); - return; - } - - fmt = GET_RTX_FORMAT (code); - for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--) - { - int j; - - switch (fmt[i]) - { - case 'E': - for (j = 0; j < XVECLEN (in_this, i); j++) - record_excess_regs (XVECEXP (in_this, i, j), not_in_this, output); - break; - - case 'e': - record_excess_regs (XEXP (in_this, i), not_in_this, output); - break; - } - } -} - -/* Check what regs are referred to in the libcall block ending with INSN, - aside from those mentioned in the equivalent value. - If there are none, return 0. - If there are one or more, return an EXPR_LIST containing all of them. */ - -static rtx -libcall_other_reg (insn, equiv) - rtx insn, equiv; -{ - rtx note = find_reg_note (insn, REG_RETVAL, NULL_RTX); - rtx p = XEXP (note, 0); - rtx output = 0; - - /* First, find all the regs used in the libcall block - that are not mentioned as inputs to the result. */ - - while (p != insn) - { - if (GET_CODE (p) == INSN || GET_CODE (p) == JUMP_INSN - || GET_CODE (p) == CALL_INSN) - record_excess_regs (PATTERN (p), equiv, &output); - p = NEXT_INSN (p); - } - - return output; -} - -/* Return 1 if all uses of REG - are between INSN and the end of the basic block. */ - -static int -reg_in_basic_block_p (insn, reg) - rtx insn, reg; -{ - int regno = REGNO (reg); - rtx p; - - if (regno_first_uid[regno] != INSN_UID (insn)) - return 0; - - /* Search this basic block for the already recorded last use of the reg. */ - for (p = insn; p; p = NEXT_INSN (p)) - { - switch (GET_CODE (p)) - { - case NOTE: - break; - - case INSN: - case CALL_INSN: - /* Ordinary insn: if this is the last use, we win. */ - if (regno_last_uid[regno] == INSN_UID (p)) - return 1; - break; - - case JUMP_INSN: - /* Jump insn: if this is the last use, we win. */ - if (regno_last_uid[regno] == INSN_UID (p)) - return 1; - /* Otherwise, it's the end of the basic block, so we lose. */ - return 0; - - case CODE_LABEL: - case BARRIER: - /* It's the end of the basic block, so we lose. */ - return 0; - } - } - - /* The "last use" doesn't follow the "first use"?? */ - abort (); -} - -/* Compute the benefit of eliminating the insns in the block whose - last insn is LAST. This may be a group of insns used to compute a - value directly or can contain a library call. */ - -static int -libcall_benefit (last) - rtx last; -{ - rtx insn; - int benefit = 0; - - for (insn = XEXP (find_reg_note (last, REG_RETVAL, NULL_RTX), 0); - insn != last; insn = NEXT_INSN (insn)) - { - if (GET_CODE (insn) == CALL_INSN) - benefit += 10; /* Assume at least this many insns in a library - routine. */ - else if (GET_CODE (insn) == INSN - && GET_CODE (PATTERN (insn)) != USE - && GET_CODE (PATTERN (insn)) != CLOBBER) - benefit++; - } - - return benefit; -} - -/* Skip COUNT insns from INSN, counting library calls as 1 insn. */ - -static rtx -skip_consec_insns (insn, count) - rtx insn; - int count; -{ - for (; count > 0; count--) - { - rtx temp; - - /* If first insn of libcall sequence, skip to end. */ - /* Do this at start of loop, since INSN is guaranteed to - be an insn here. */ - if (GET_CODE (insn) != NOTE - && (temp = find_reg_note (insn, REG_LIBCALL, NULL_RTX))) - insn = XEXP (temp, 0); - - do insn = NEXT_INSN (insn); - while (GET_CODE (insn) == NOTE); - } - - return insn; -} - -/* Ignore any movable whose insn falls within a libcall - which is part of another movable. - We make use of the fact that the movable for the libcall value - was made later and so appears later on the chain. */ - -static void -ignore_some_movables (movables) - struct movable *movables; -{ - register struct movable *m, *m1; - - for (m = movables; m; m = m->next) - { - /* Is this a movable for the value of a libcall? */ - rtx note = find_reg_note (m->insn, REG_RETVAL, NULL_RTX); - if (note) - { - rtx insn; - /* Check for earlier movables inside that range, - and mark them invalid. We cannot use LUIDs here because - insns created by loop.c for prior loops don't have LUIDs. - Rather than reject all such insns from movables, we just - explicitly check each insn in the libcall (since invariant - libcalls aren't that common). */ - for (insn = XEXP (note, 0); insn != m->insn; insn = NEXT_INSN (insn)) - for (m1 = movables; m1 != m; m1 = m1->next) - if (m1->insn == insn) - m1->done = 1; - } - } -} - -/* For each movable insn, see if the reg that it loads - leads when it dies right into another conditionally movable insn. - If so, record that the second insn "forces" the first one, - since the second can be moved only if the first is. */ - -static void -force_movables (movables) - struct movable *movables; -{ - register struct movable *m, *m1; - for (m1 = movables; m1; m1 = m1->next) - /* Omit this if moving just the (SET (REG) 0) of a zero-extend. */ - if (!m1->partial && !m1->done) - { - int regno = m1->regno; - for (m = m1->next; m; m = m->next) - /* ??? Could this be a bug? What if CSE caused the - register of M1 to be used after this insn? - Since CSE does not update regno_last_uid, - this insn M->insn might not be where it dies. - But very likely this doesn't matter; what matters is - that M's reg is computed from M1's reg. */ - if (INSN_UID (m->insn) == regno_last_uid[regno] - && !m->done) - break; - if (m != 0 && m->set_src == m1->set_dest - /* If m->consec, m->set_src isn't valid. */ - && m->consec == 0) - m = 0; - - /* Increase the priority of the moving the first insn - since it permits the second to be moved as well. */ - if (m != 0) - { - m->forces = m1; - m1->lifetime += m->lifetime; - m1->savings += m1->savings; - } - } -} - -/* Find invariant expressions that are equal and can be combined into - one register. */ - -static void -combine_movables (movables, nregs) - struct movable *movables; - int nregs; -{ - register struct movable *m; - char *matched_regs = (char *) alloca (nregs); - enum machine_mode mode; - - /* Regs that are set more than once are not allowed to match - or be matched. I'm no longer sure why not. */ - /* Perhaps testing m->consec_sets would be more appropriate here? */ - - for (m = movables; m; m = m->next) - if (m->match == 0 && n_times_used[m->regno] == 1 && !m->partial) - { - register struct movable *m1; - int regno = m->regno; - rtx reg_note, reg_note1; - - bzero (matched_regs, nregs); - matched_regs[regno] = 1; - - for (m1 = movables; m1; m1 = m1->next) - if (m != m1 && m1->match == 0 && n_times_used[m1->regno] == 1 - /* A reg used outside the loop mustn't be eliminated. */ - && !m1->global - /* A reg used for zero-extending mustn't be eliminated. */ - && !m1->partial - && (matched_regs[m1->regno] - || - ( - /* Can combine regs with different modes loaded from the - same constant only if the modes are the same or - if both are integer modes with M wider or the same - width as M1. The check for integer is redundant, but - safe, since the only case of differing destination - modes with equal sources is when both sources are - VOIDmode, i.e., CONST_INT. */ - (GET_MODE (m->set_dest) == GET_MODE (m1->set_dest) - || (GET_MODE_CLASS (GET_MODE (m->set_dest)) == MODE_INT - && GET_MODE_CLASS (GET_MODE (m1->set_dest)) == MODE_INT - && (GET_MODE_BITSIZE (GET_MODE (m->set_dest)) - >= GET_MODE_BITSIZE (GET_MODE (m1->set_dest))))) - /* See if the source of M1 says it matches M. */ - && ((GET_CODE (m1->set_src) == REG - && matched_regs[REGNO (m1->set_src)]) - || rtx_equal_for_loop_p (m->set_src, m1->set_src, - movables)))) - && ((m->dependencies == m1->dependencies) - || rtx_equal_p (m->dependencies, m1->dependencies))) - { - m->lifetime += m1->lifetime; - m->savings += m1->savings; - m1->done = 1; - m1->match = m; - matched_regs[m1->regno] = 1; - } - } - - /* Now combine the regs used for zero-extension. - This can be done for those not marked `global' - provided their lives don't overlap. */ - - for (mode = GET_CLASS_NARROWEST_MODE (MODE_INT); mode != VOIDmode; - mode = GET_MODE_WIDER_MODE (mode)) - { - register struct movable *m0 = 0; - - /* Combine all the registers for extension from mode MODE. - Don't combine any that are used outside this loop. */ - for (m = movables; m; m = m->next) - if (m->partial && ! m->global - && mode == GET_MODE (SET_SRC (PATTERN (NEXT_INSN (m->insn))))) - { - register struct movable *m1; - int first = uid_luid[regno_first_uid[m->regno]]; - int last = uid_luid[regno_last_uid[m->regno]]; - - if (m0 == 0) - { - /* First one: don't check for overlap, just record it. */ - m0 = m; - continue; - } - - /* Make sure they extend to the same mode. - (Almost always true.) */ - if (GET_MODE (m->set_dest) != GET_MODE (m0->set_dest)) - continue; - - /* We already have one: check for overlap with those - already combined together. */ - for (m1 = movables; m1 != m; m1 = m1->next) - if (m1 == m0 || (m1->partial && m1->match == m0)) - if (! (uid_luid[regno_first_uid[m1->regno]] > last - || uid_luid[regno_last_uid[m1->regno]] < first)) - goto overlap; - - /* No overlap: we can combine this with the others. */ - m0->lifetime += m->lifetime; - m0->savings += m->savings; - m->done = 1; - m->match = m0; - - overlap: ; - } - } -} - -/* Return 1 if regs X and Y will become the same if moved. */ - -static int -regs_match_p (x, y, movables) - rtx x, y; - struct movable *movables; -{ - int xn = REGNO (x); - int yn = REGNO (y); - struct movable *mx, *my; - - for (mx = movables; mx; mx = mx->next) - if (mx->regno == xn) - break; - - for (my = movables; my; my = my->next) - if (my->regno == yn) - break; - - return (mx && my - && ((mx->match == my->match && mx->match != 0) - || mx->match == my - || mx == my->match)); -} - -/* Return 1 if X and Y are identical-looking rtx's. - This is the Lisp function EQUAL for rtx arguments. - - If two registers are matching movables or a movable register and an - equivalent constant, consider them equal. */ - -static int -rtx_equal_for_loop_p (x, y, movables) - rtx x, y; - struct movable *movables; -{ - register int i; - register int j; - register struct movable *m; - register enum rtx_code code; - register char *fmt; - - if (x == y) - return 1; - if (x == 0 || y == 0) - return 0; - - code = GET_CODE (x); - - /* If we have a register and a constant, they may sometimes be - equal. */ - if (GET_CODE (x) == REG && n_times_set[REGNO (x)] == -2 - && CONSTANT_P (y)) - for (m = movables; m; m = m->next) - if (m->move_insn && m->regno == REGNO (x) - && rtx_equal_p (m->set_src, y)) - return 1; - - else if (GET_CODE (y) == REG && n_times_set[REGNO (y)] == -2 - && CONSTANT_P (x)) - for (m = movables; m; m = m->next) - if (m->move_insn && m->regno == REGNO (y) - && rtx_equal_p (m->set_src, x)) - return 1; - - /* Otherwise, rtx's of different codes cannot be equal. */ - if (code != GET_CODE (y)) - return 0; - - /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent. - (REG:SI x) and (REG:HI x) are NOT equivalent. */ - - if (GET_MODE (x) != GET_MODE (y)) - return 0; - - /* These three types of rtx's can be compared nonrecursively. */ - if (code == REG) - return (REGNO (x) == REGNO (y) || regs_match_p (x, y, movables)); - - if (code == LABEL_REF) - return XEXP (x, 0) == XEXP (y, 0); - if (code == SYMBOL_REF) - return XSTR (x, 0) == XSTR (y, 0); - - /* Compare the elements. If any pair of corresponding elements - fail to match, return 0 for the whole things. */ - - fmt = GET_RTX_FORMAT (code); - for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--) - { - switch (fmt[i]) - { - case 'w': - if (XWINT (x, i) != XWINT (y, i)) - return 0; - break; - - case 'i': - if (XINT (x, i) != XINT (y, i)) - return 0; - break; - - case 'E': - /* Two vectors must have the same length. */ - if (XVECLEN (x, i) != XVECLEN (y, i)) - return 0; - - /* And the corresponding elements must match. */ - for (j = 0; j < XVECLEN (x, i); j++) - if (rtx_equal_for_loop_p (XVECEXP (x, i, j), XVECEXP (y, i, j), movables) == 0) - return 0; - break; - - case 'e': - if (rtx_equal_for_loop_p (XEXP (x, i), XEXP (y, i), movables) == 0) - return 0; - break; - - case 's': - if (strcmp (XSTR (x, i), XSTR (y, i))) - return 0; - break; - - case 'u': - /* These are just backpointers, so they don't matter. */ - break; - - case '0': - break; - - /* It is believed that rtx's at this level will never - contain anything but integers and other rtx's, - except for within LABEL_REFs and SYMBOL_REFs. */ - default: - abort (); - } - } - return 1; -} - -/* If X contains any LABEL_REF's, add REG_LABEL notes for them to all - insns in INSNS which use thet reference. */ - -static void -add_label_notes (x, insns) - rtx x; - rtx insns; -{ - enum rtx_code code = GET_CODE (x); - int i, j; - char *fmt; - rtx insn; - - if (code == LABEL_REF && !LABEL_REF_NONLOCAL_P (x)) - { - rtx next = next_real_insn (XEXP (x, 0)); - - /* Don't record labels that refer to dispatch tables. - This is not necessary, since the tablejump references the same label. - And if we did record them, flow.c would make worse code. */ - if (next == 0 - || ! (GET_CODE (next) == JUMP_INSN - && (GET_CODE (PATTERN (next)) == ADDR_VEC - || GET_CODE (PATTERN (next)) == ADDR_DIFF_VEC))) - { - for (insn = insns; insn; insn = NEXT_INSN (insn)) - if (reg_mentioned_p (XEXP (x, 0), insn)) - REG_NOTES (insn) = gen_rtx (EXPR_LIST, REG_LABEL, XEXP (x, 0), - REG_NOTES (insn)); - } - return; - } - - fmt = GET_RTX_FORMAT (code); - for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--) - { - if (fmt[i] == 'e') - add_label_notes (XEXP (x, i), insns); - else if (fmt[i] == 'E') - for (j = XVECLEN (x, i) - 1; j >= 0; j--) - add_label_notes (XVECEXP (x, i, j), insns); - } -} - -/* Scan MOVABLES, and move the insns that deserve to be moved. - If two matching movables are combined, replace one reg with the - other throughout. */ - -static void -move_movables (movables, threshold, insn_count, loop_start, end, nregs) - struct movable *movables; - int threshold; - int insn_count; - rtx loop_start; - rtx end; - int nregs; -{ - rtx new_start = 0; - register struct movable *m; - register rtx p; - /* Map of pseudo-register replacements to handle combining - when we move several insns that load the same value - into different pseudo-registers. */ - rtx *reg_map = (rtx *) alloca (nregs * sizeof (rtx)); - char *already_moved = (char *) alloca (nregs); - - bzero (already_moved, nregs); - bzero (reg_map, nregs * sizeof (rtx)); - - num_movables = 0; - - for (m = movables; m; m = m->next) - { - /* Describe this movable insn. */ - - if (loop_dump_stream) - { - fprintf (loop_dump_stream, "Insn %d: regno %d (life %d), ", - INSN_UID (m->insn), m->regno, m->lifetime); - if (m->consec > 0) - fprintf (loop_dump_stream, "consec %d, ", m->consec); - if (m->cond) - fprintf (loop_dump_stream, "cond "); - if (m->force) - fprintf (loop_dump_stream, "force "); - if (m->global) - fprintf (loop_dump_stream, "global "); - if (m->done) - fprintf (loop_dump_stream, "done "); - if (m->move_insn) - fprintf (loop_dump_stream, "move-insn "); - if (m->match) - fprintf (loop_dump_stream, "matches %d ", - INSN_UID (m->match->insn)); - if (m->forces) - fprintf (loop_dump_stream, "forces %d ", - INSN_UID (m->forces->insn)); - } - - /* Count movables. Value used in heuristics in strength_reduce. */ - num_movables++; - - /* Ignore the insn if it's already done (it matched something else). - Otherwise, see if it is now safe to move. */ - - if (!m->done - && (! m->cond - || (1 == invariant_p (m->set_src) - && (m->dependencies == 0 - || 1 == invariant_p (m->dependencies)) - && (m->consec == 0 - || 1 == consec_sets_invariant_p (m->set_dest, - m->consec + 1, - m->insn)))) - && (! m->forces || m->forces->done)) - { - register int regno; - register rtx p; - int savings = m->savings; - - /* We have an insn that is safe to move. - Compute its desirability. */ - - p = m->insn; - regno = m->regno; - - if (loop_dump_stream) - fprintf (loop_dump_stream, "savings %d ", savings); - - if (moved_once[regno]) - { - insn_count *= 2; - - if (loop_dump_stream) - fprintf (loop_dump_stream, "halved since already moved "); - } - - /* An insn MUST be moved if we already moved something else - which is safe only if this one is moved too: that is, - if already_moved[REGNO] is nonzero. */ - - /* An insn is desirable to move if the new lifetime of the - register is no more than THRESHOLD times the old lifetime. - If it's not desirable, it means the loop is so big - that moving won't speed things up much, - and it is liable to make register usage worse. */ - - /* It is also desirable to move if it can be moved at no - extra cost because something else was already moved. */ - - if (already_moved[regno] - || (threshold * savings * m->lifetime) >= insn_count - || (m->forces && m->forces->done - && n_times_used[m->forces->regno] == 1)) - { - int count; - register struct movable *m1; - rtx first; - - /* Now move the insns that set the reg. */ - - if (m->partial && m->match) - { - rtx newpat, i1; - rtx r1, r2; - /* Find the end of this chain of matching regs. - Thus, we load each reg in the chain from that one reg. - And that reg is loaded with 0 directly, - since it has ->match == 0. */ - for (m1 = m; m1->match; m1 = m1->match); - newpat = gen_move_insn (SET_DEST (PATTERN (m->insn)), - SET_DEST (PATTERN (m1->insn))); - i1 = emit_insn_before (newpat, loop_start); - - /* Mark the moved, invariant reg as being allowed to - share a hard reg with the other matching invariant. */ - REG_NOTES (i1) = REG_NOTES (m->insn); - r1 = SET_DEST (PATTERN (m->insn)); - r2 = SET_DEST (PATTERN (m1->insn)); - regs_may_share = gen_rtx (EXPR_LIST, VOIDmode, r1, - gen_rtx (EXPR_LIST, VOIDmode, r2, - regs_may_share)); - delete_insn (m->insn); - - if (new_start == 0) - new_start = i1; - - if (loop_dump_stream) - fprintf (loop_dump_stream, " moved to %d", INSN_UID (i1)); - } - /* If we are to re-generate the item being moved with a - new move insn, first delete what we have and then emit - the move insn before the loop. */ - else if (m->move_insn) - { - rtx i1, temp; - - for (count = m->consec; count >= 0; count--) - { - /* If this is the first insn of a library call sequence, - skip to the end. */ - if (GET_CODE (p) != NOTE - && (temp = find_reg_note (p, REG_LIBCALL, NULL_RTX))) - p = XEXP (temp, 0); - - /* If this is the last insn of a libcall sequence, then - delete every insn in the sequence except the last. - The last insn is handled in the normal manner. */ - if (GET_CODE (p) != NOTE - && (temp = find_reg_note (p, REG_RETVAL, NULL_RTX))) - { - temp = XEXP (temp, 0); - while (temp != p) - temp = delete_insn (temp); - } - - p = delete_insn (p); - } - - start_sequence (); - emit_move_insn (m->set_dest, m->set_src); - temp = get_insns (); - end_sequence (); - - add_label_notes (m->set_src, temp); - - i1 = emit_insns_before (temp, loop_start); - if (! find_reg_note (i1, REG_EQUAL, NULL_RTX)) - REG_NOTES (i1) - = gen_rtx (EXPR_LIST, - m->is_equiv ? REG_EQUIV : REG_EQUAL, - m->set_src, REG_NOTES (i1)); - - if (loop_dump_stream) - fprintf (loop_dump_stream, " moved to %d", INSN_UID (i1)); - - /* The more regs we move, the less we like moving them. */ - threshold -= 3; - } - else - { - for (count = m->consec; count >= 0; count--) - { - rtx i1, temp; - - /* If first insn of libcall sequence, skip to end. */ - /* Do this at start of loop, since p is guaranteed to - be an insn here. */ - if (GET_CODE (p) != NOTE - && (temp = find_reg_note (p, REG_LIBCALL, NULL_RTX))) - p = XEXP (temp, 0); - - /* If last insn of libcall sequence, move all - insns except the last before the loop. The last - insn is handled in the normal manner. */ - if (GET_CODE (p) != NOTE - && (temp = find_reg_note (p, REG_RETVAL, NULL_RTX))) - { - rtx fn_address = 0; - rtx fn_reg = 0; - rtx fn_address_insn = 0; - - first = 0; - for (temp = XEXP (temp, 0); temp != p; - temp = NEXT_INSN (temp)) - { - rtx body; - rtx n; - rtx next; - - if (GET_CODE (temp) == NOTE) - continue; - - body = PATTERN (temp); - - /* Find the next insn after TEMP, - not counting USE or NOTE insns. */ - for (next = NEXT_INSN (temp); next != p; - next = NEXT_INSN (next)) - if (! (GET_CODE (next) == INSN - && GET_CODE (PATTERN (next)) == USE) - && GET_CODE (next) != NOTE) - break; - - /* If that is the call, this may be the insn - that loads the function address. - - Extract the function address from the insn - that loads it into a register. - If this insn was cse'd, we get incorrect code. - - So emit a new move insn that copies the - function address into the register that the - call insn will use. flow.c will delete any - redundant stores that we have created. */ - if (GET_CODE (next) == CALL_INSN - && GET_CODE (body) == SET - && GET_CODE (SET_DEST (body)) == REG - && (n = find_reg_note (temp, REG_EQUAL, - NULL_RTX))) - { - fn_reg = SET_SRC (body); - if (GET_CODE (fn_reg) != REG) - fn_reg = SET_DEST (body); - fn_address = XEXP (n, 0); - fn_address_insn = temp; - } - /* We have the call insn. - If it uses the register we suspect it might, - load it with the correct address directly. */ - if (GET_CODE (temp) == CALL_INSN - && fn_address != 0 - && reg_referenced_p (fn_reg, body)) - emit_insn_after (gen_move_insn (fn_reg, - fn_address), - fn_address_insn); - - if (GET_CODE (temp) == CALL_INSN) - i1 = emit_call_insn_before (body, loop_start); - else - i1 = emit_insn_before (body, loop_start); - if (first == 0) - first = i1; - if (temp == fn_address_insn) - fn_address_insn = i1; - REG_NOTES (i1) = REG_NOTES (temp); - delete_insn (temp); - } - } - if (m->savemode != VOIDmode) - { - /* P sets REG to zero; but we should clear only - the bits that are not covered by the mode - m->savemode. */ - rtx reg = m->set_dest; - rtx sequence; - rtx tem; - - start_sequence (); - tem = expand_binop - (GET_MODE (reg), and_optab, reg, - GEN_INT ((((HOST_WIDE_INT) 1 - << GET_MODE_BITSIZE (m->savemode))) - - 1), - reg, 1, OPTAB_LIB_WIDEN); - if (tem == 0) - abort (); - if (tem != reg) - emit_move_insn (reg, tem); - sequence = gen_sequence (); - end_sequence (); - i1 = emit_insn_before (sequence, loop_start); - } - else if (GET_CODE (p) == CALL_INSN) - i1 = emit_call_insn_before (PATTERN (p), loop_start); - else - i1 = emit_insn_before (PATTERN (p), loop_start); - - REG_NOTES (i1) = REG_NOTES (p); - - /* If there is a REG_EQUAL note present whose value is - not loop invariant, then delete it, since it may - cause problems with later optimization passes. - It is possible for cse to create such notes - like this as a result of record_jump_cond. */ - - if ((temp = find_reg_note (i1, REG_EQUAL, NULL_RTX)) - && ! invariant_p (XEXP (temp, 0))) - remove_note (i1, temp); - - if (new_start == 0) - new_start = i1; - - if (loop_dump_stream) - fprintf (loop_dump_stream, " moved to %d", - INSN_UID (i1)); - -#if 0 - /* This isn't needed because REG_NOTES is copied - below and is wrong since P might be a PARALLEL. */ - if (REG_NOTES (i1) == 0 - && ! m->partial /* But not if it's a zero-extend clr. */ - && ! m->global /* and not if used outside the loop - (since it might get set outside). */ - && CONSTANT_P (SET_SRC (PATTERN (p)))) - REG_NOTES (i1) - = gen_rtx (EXPR_LIST, REG_EQUAL, - SET_SRC (PATTERN (p)), REG_NOTES (i1)); -#endif - - /* If library call, now fix the REG_NOTES that contain - insn pointers, namely REG_LIBCALL on FIRST - and REG_RETVAL on I1. */ - if (temp = find_reg_note (i1, REG_RETVAL, NULL_RTX)) - { - XEXP (temp, 0) = first; - temp = find_reg_note (first, REG_LIBCALL, NULL_RTX); - XEXP (temp, 0) = i1; - } - - delete_insn (p); - do p = NEXT_INSN (p); - while (p && GET_CODE (p) == NOTE); - } - - /* The more regs we move, the less we like moving them. */ - threshold -= 3; - } - - /* Any other movable that loads the same register - MUST be moved. */ - already_moved[regno] = 1; - - /* This reg has been moved out of one loop. */ - moved_once[regno] = 1; - - /* The reg set here is now invariant. */ - if (! m->partial) - n_times_set[regno] = 0; - - m->done = 1; - - /* Change the length-of-life info for the register - to say it lives at least the full length of this loop. - This will help guide optimizations in outer loops. */ - - if (uid_luid[regno_first_uid[regno]] > INSN_LUID (loop_start)) - /* This is the old insn before all the moved insns. - We can't use the moved insn because it is out of range - in uid_luid. Only the old insns have luids. */ - regno_first_uid[regno] = INSN_UID (loop_start); - if (uid_luid[regno_last_uid[regno]] < INSN_LUID (end)) - regno_last_uid[regno] = INSN_UID (end); - - /* Combine with this moved insn any other matching movables. */ - - if (! m->partial) - for (m1 = movables; m1; m1 = m1->next) - if (m1->match == m) - { - rtx temp; - - /* Schedule the reg loaded by M1 - for replacement so that shares the reg of M. - If the modes differ (only possible in restricted - circumstances, make a SUBREG. */ - if (GET_MODE (m->set_dest) == GET_MODE (m1->set_dest)) - reg_map[m1->regno] = m->set_dest; - else - reg_map[m1->regno] - = gen_lowpart_common (GET_MODE (m1->set_dest), - m->set_dest); - - /* Get rid of the matching insn - and prevent further processing of it. */ - m1->done = 1; - - /* if library call, delete all insn except last, which - is deleted below */ - if (temp = find_reg_note (m1->insn, REG_RETVAL, - NULL_RTX)) - { - for (temp = XEXP (temp, 0); temp != m1->insn; - temp = NEXT_INSN (temp)) - delete_insn (temp); - } - delete_insn (m1->insn); - - /* Any other movable that loads the same register - MUST be moved. */ - already_moved[m1->regno] = 1; - - /* The reg merged here is now invariant, - if the reg it matches is invariant. */ - if (! m->partial) - n_times_set[m1->regno] = 0; - } - } - else if (loop_dump_stream) - fprintf (loop_dump_stream, "not desirable"); - } - else if (loop_dump_stream && !m->match) - fprintf (loop_dump_stream, "not safe"); - - if (loop_dump_stream) - fprintf (loop_dump_stream, "\n"); - } - - if (new_start == 0) - new_start = loop_start; - - /* Go through all the instructions in the loop, making - all the register substitutions scheduled in REG_MAP. */ - for (p = new_start; p != end; p = NEXT_INSN (p)) - if (GET_CODE (p) == INSN || GET_CODE (p) == JUMP_INSN - || GET_CODE (p) == CALL_INSN) - { - replace_regs (PATTERN (p), reg_map, nregs, 0); - replace_regs (REG_NOTES (p), reg_map, nregs, 0); - INSN_CODE (p) = -1; - } -} - -#if 0 -/* Scan X and replace the address of any MEM in it with ADDR. - REG is the address that MEM should have before the replacement. */ - -static void -replace_call_address (x, reg, addr) - rtx x, reg, addr; -{ - register enum rtx_code code; - register int i; - register char *fmt; - - if (x == 0) - return; - code = GET_CODE (x); - switch (code) - { - case PC: - case CC0: - case CONST_INT: - case CONST_DOUBLE: - case CONST: - case SYMBOL_REF: - case LABEL_REF: - case REG: - return; - - case SET: - /* Short cut for very common case. */ - replace_call_address (XEXP (x, 1), reg, addr); - return; - - case CALL: - /* Short cut for very common case. */ - replace_call_address (XEXP (x, 0), reg, addr); - return; - - case MEM: - /* If this MEM uses a reg other than the one we expected, - something is wrong. */ - if (XEXP (x, 0) != reg) - abort (); - XEXP (x, 0) = addr; - return; - } - - fmt = GET_RTX_FORMAT (code); - for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--) - { - if (fmt[i] == 'e') - replace_call_address (XEXP (x, i), reg, addr); - if (fmt[i] == 'E') - { - register int j; - for (j = 0; j < XVECLEN (x, i); j++) - replace_call_address (XVECEXP (x, i, j), reg, addr); - } - } -} -#endif - -/* Return the number of memory refs to addresses that vary - in the rtx X. */ - -static int -count_nonfixed_reads (x) - rtx x; -{ - register enum rtx_code code; - register int i; - register char *fmt; - int value; - - if (x == 0) - return 0; - - code = GET_CODE (x); - switch (code) - { - case PC: - case CC0: - case CONST_INT: - case CONST_DOUBLE: - case CONST: - case SYMBOL_REF: - case LABEL_REF: - case REG: - return 0; - - case MEM: - return ((invariant_p (XEXP (x, 0)) != 1) - + count_nonfixed_reads (XEXP (x, 0))); - } - - value = 0; - fmt = GET_RTX_FORMAT (code); - for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--) - { - if (fmt[i] == 'e') - value += count_nonfixed_reads (XEXP (x, i)); - if (fmt[i] == 'E') - { - register int j; - for (j = 0; j < XVECLEN (x, i); j++) - value += count_nonfixed_reads (XVECEXP (x, i, j)); - } - } - return value; -} - - -#if 0 -/* P is an instruction that sets a register to the result of a ZERO_EXTEND. - Replace it with an instruction to load just the low bytes - if the machine supports such an instruction, - and insert above LOOP_START an instruction to clear the register. */ - -static void -constant_high_bytes (p, loop_start) - rtx p, loop_start; -{ - register rtx new; - register int insn_code_number; - - /* Try to change (SET (REG ...) (ZERO_EXTEND (..:B ...))) - to (SET (STRICT_LOW_PART (SUBREG:B (REG...))) ...). */ - - new = gen_rtx (SET, VOIDmode, - gen_rtx (STRICT_LOW_PART, VOIDmode, - gen_rtx (SUBREG, GET_MODE (XEXP (SET_SRC (PATTERN (p)), 0)), - SET_DEST (PATTERN (p)), - 0)), - XEXP (SET_SRC (PATTERN (p)), 0)); - insn_code_number = recog (new, p); - - if (insn_code_number) - { - register int i; - - /* Clear destination register before the loop. */ - emit_insn_before (gen_rtx (SET, VOIDmode, - SET_DEST (PATTERN (p)), - const0_rtx), - loop_start); - - /* Inside the loop, just load the low part. */ - PATTERN (p) = new; - } -} -#endif - -/* Scan a loop setting the variables `unknown_address_altered', - `num_mem_sets', `loop_continue', loops_enclosed', `loop_has_call', - and `loop_has_volatile'. - Also, fill in the array `loop_store_mems'. */ - -static void -prescan_loop (start, end) - rtx start, end; -{ - register int level = 1; - register rtx insn; - - unknown_address_altered = 0; - loop_has_call = 0; - loop_has_volatile = 0; - loop_store_mems_idx = 0; - - num_mem_sets = 0; - loops_enclosed = 1; - loop_continue = 0; - - for (insn = NEXT_INSN (start); insn != NEXT_INSN (end); - insn = NEXT_INSN (insn)) - { - if (GET_CODE (insn) == NOTE) - { - if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG) - { - ++level; - /* Count number of loops contained in this one. */ - loops_enclosed++; - } - else if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_END) - { - --level; - if (level == 0) - { - end = insn; - break; - } - } - else if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_CONT) - { - if (level == 1) - loop_continue = insn; - } - } - else if (GET_CODE (insn) == CALL_INSN) - { - unknown_address_altered = 1; - loop_has_call = 1; - } - else - { - if (GET_CODE (insn) == INSN || GET_CODE (insn) == JUMP_INSN) - { - if (volatile_refs_p (PATTERN (insn))) - loop_has_volatile = 1; - - note_stores (PATTERN (insn), note_addr_stored); - } - } - } -} - -/* Scan the function looking for loops. Record the start and end of each loop. - Also mark as invalid loops any loops that contain a setjmp or are branched - to from outside the loop. */ - -static void -find_and_verify_loops (f) - rtx f; -{ - rtx insn, label; - int current_loop = -1; - int next_loop = -1; - int loop; - - /* If there are jumps to undefined labels, - treat them as jumps out of any/all loops. - This also avoids writing past end of tables when there are no loops. */ - uid_loop_num[0] = -1; - - /* Find boundaries of loops, mark which loops are contained within - loops, and invalidate loops that have setjmp. */ - - for (insn = f; insn; insn = NEXT_INSN (insn)) - { - if (GET_CODE (insn) == NOTE) - switch (NOTE_LINE_NUMBER (insn)) - { - case NOTE_INSN_LOOP_BEG: - loop_number_loop_starts[++next_loop] = insn; - loop_number_loop_ends[next_loop] = 0; - loop_outer_loop[next_loop] = current_loop; - loop_invalid[next_loop] = 0; - loop_number_exit_labels[next_loop] = 0; - current_loop = next_loop; - break; - - case NOTE_INSN_SETJMP: - /* In this case, we must invalidate our current loop and any - enclosing loop. */ - for (loop = current_loop; loop != -1; loop = loop_outer_loop[loop]) - { - loop_invalid[loop] = 1; - if (loop_dump_stream) - fprintf (loop_dump_stream, - "\nLoop at %d ignored due to setjmp.\n", - INSN_UID (loop_number_loop_starts[loop])); - } - break; - - case NOTE_INSN_LOOP_END: - if (current_loop == -1) - abort (); - - loop_number_loop_ends[current_loop] = insn; - current_loop = loop_outer_loop[current_loop]; - break; - - } - - /* Note that this will mark the NOTE_INSN_LOOP_END note as being in the - enclosing loop, but this doesn't matter. */ - uid_loop_num[INSN_UID (insn)] = current_loop; - } - - /* Any loop containing a label used in an initializer must be invalidated, - because it can be jumped into from anywhere. */ - - for (label = forced_labels; label; label = XEXP (label, 1)) - { - int loop_num; - - for (loop_num = uid_loop_num[INSN_UID (XEXP (label, 0))]; - loop_num != -1; - loop_num = loop_outer_loop[loop_num]) - loop_invalid[loop_num] = 1; - } - - /* Now scan all insn's in the function. If any JUMP_INSN branches into a - loop that it is not contained within, that loop is marked invalid. - If any INSN or CALL_INSN uses a label's address, then the loop containing - that label is marked invalid, because it could be jumped into from - anywhere. - - Also look for blocks of code ending in an unconditional branch that - exits the loop. If such a block is surrounded by a conditional - branch around the block, move the block elsewhere (see below) and - invert the jump to point to the code block. This may eliminate a - label in our loop and will simplify processing by both us and a - possible second cse pass. */ - - for (insn = f; insn; insn = NEXT_INSN (insn)) - if (GET_RTX_CLASS (GET_CODE (insn)) == 'i') - { - int this_loop_num = uid_loop_num[INSN_UID (insn)]; - - if (GET_CODE (insn) == INSN || GET_CODE (insn) == CALL_INSN) - { - rtx note = find_reg_note (insn, REG_LABEL, NULL_RTX); - if (note) - { - int loop_num; - - for (loop_num = uid_loop_num[INSN_UID (XEXP (note, 0))]; - loop_num != -1; - loop_num = loop_outer_loop[loop_num]) - loop_invalid[loop_num] = 1; - } - } - - if (GET_CODE (insn) != JUMP_INSN) - continue; - - mark_loop_jump (PATTERN (insn), this_loop_num); - - /* See if this is an unconditional branch outside the loop. */ - if (this_loop_num != -1 - && (GET_CODE (PATTERN (insn)) == RETURN - || (simplejump_p (insn) - && (uid_loop_num[INSN_UID (JUMP_LABEL (insn))] - != this_loop_num))) - && get_max_uid () < max_uid_for_loop) - { - rtx p; - rtx our_next = next_real_insn (insn); - - /* Go backwards until we reach the start of the loop, a label, - or a JUMP_INSN. */ - for (p = PREV_INSN (insn); - GET_CODE (p) != CODE_LABEL - && ! (GET_CODE (p) == NOTE - && NOTE_LINE_NUMBER (p) == NOTE_INSN_LOOP_BEG) - && GET_CODE (p) != JUMP_INSN; - p = PREV_INSN (p)) - ; - - /* If we stopped on a JUMP_INSN to the next insn after INSN, - we have a block of code to try to move. - - We look backward and then forward from the target of INSN - to find a BARRIER at the same loop depth as the target. - If we find such a BARRIER, we make a new label for the start - of the block, invert the jump in P and point it to that label, - and move the block of code to the spot we found. */ - - if (GET_CODE (p) == JUMP_INSN - && JUMP_LABEL (p) != 0 - /* Just ignore jumps to labels that were never emitted. - These always indicate compilation errors. */ - && INSN_UID (JUMP_LABEL (p)) != 0 - && condjump_p (p) - && ! simplejump_p (p) - && next_real_insn (JUMP_LABEL (p)) == our_next) - { - rtx target - = JUMP_LABEL (insn) ? JUMP_LABEL (insn) : get_last_insn (); - int target_loop_num = uid_loop_num[INSN_UID (target)]; - rtx loc; - - for (loc = target; loc; loc = PREV_INSN (loc)) - if (GET_CODE (loc) == BARRIER - && uid_loop_num[INSN_UID (loc)] == target_loop_num) - break; - - if (loc == 0) - for (loc = target; loc; loc = NEXT_INSN (loc)) - if (GET_CODE (loc) == BARRIER - && uid_loop_num[INSN_UID (loc)] == target_loop_num) - break; - - if (loc) - { - rtx cond_label = JUMP_LABEL (p); - rtx new_label = get_label_after (p); - - /* Ensure our label doesn't go away. */ - LABEL_NUSES (cond_label)++; - - /* Verify that uid_loop_num is large enough and that - we can invert P. */ - if (invert_jump (p, new_label)) - { - rtx q, r; - - /* Include the BARRIER after INSN and copy the - block after LOC. */ - new_label = squeeze_notes (new_label, NEXT_INSN (insn)); - reorder_insns (new_label, NEXT_INSN (insn), loc); - - /* All those insns are now in TARGET_LOOP_NUM. */ - for (q = new_label; q != NEXT_INSN (NEXT_INSN (insn)); - q = NEXT_INSN (q)) - uid_loop_num[INSN_UID (q)] = target_loop_num; - - /* The label jumped to by INSN is no longer a loop exit. - Unless INSN does not have a label (e.g., it is a - RETURN insn), search loop_number_exit_labels to find - its label_ref, and remove it. Also turn off - LABEL_OUTSIDE_LOOP_P bit. */ - if (JUMP_LABEL (insn)) - { - for (q = 0, - r = loop_number_exit_labels[this_loop_num]; - r; q = r, r = LABEL_NEXTREF (r)) - if (XEXP (r, 0) == JUMP_LABEL (insn)) - { - LABEL_OUTSIDE_LOOP_P (r) = 0; - if (q) - LABEL_NEXTREF (q) = LABEL_NEXTREF (r); - else - loop_number_exit_labels[this_loop_num] - = LABEL_NEXTREF (r); - break; - } - - /* If we didn't find it, then something is wrong. */ - if (! r) - abort (); - } - - /* P is now a jump outside the loop, so it must be put - in loop_number_exit_labels, and marked as such. - The easiest way to do this is to just call - mark_loop_jump again for P. */ - mark_loop_jump (PATTERN (p), this_loop_num); - - /* If INSN now jumps to the insn after it, - delete INSN. */ - if (JUMP_LABEL (insn) != 0 - && (next_real_insn (JUMP_LABEL (insn)) - == next_real_insn (insn))) - delete_insn (insn); - } - - /* Continue the loop after where the conditional - branch used to jump, since the only branch insn - in the block (if it still remains) is an inter-loop - branch and hence needs no processing. */ - insn = NEXT_INSN (cond_label); - - if (--LABEL_NUSES (cond_label) == 0) - delete_insn (cond_label); - } - } - } - } -} - -/* If any label in X jumps to a loop different from LOOP_NUM and any of the - loops it is contained in, mark the target loop invalid. - - For speed, we assume that X is part of a pattern of a JUMP_INSN. */ - -static void -mark_loop_jump (x, loop_num) - rtx x; - int loop_num; -{ - int dest_loop; - int outer_loop; - int i; - - switch (GET_CODE (x)) - { - case PC: - case USE: - case CLOBBER: - case REG: - case MEM: - case CONST_INT: - case CONST_DOUBLE: - case RETURN: - return; - - case CONST: - /* There could be a label reference in here. */ - mark_loop_jump (XEXP (x, 0), loop_num); - return; - - case PLUS: - case MINUS: - case MULT: - case LSHIFT: - mark_loop_jump (XEXP (x, 0), loop_num); - mark_loop_jump (XEXP (x, 1), loop_num); - return; - - case SIGN_EXTEND: - case ZERO_EXTEND: - mark_loop_jump (XEXP (x, 0), loop_num); - return; - - case LABEL_REF: - dest_loop = uid_loop_num[INSN_UID (XEXP (x, 0))]; - - /* Link together all labels that branch outside the loop. This - is used by final_[bg]iv_value and the loop unrolling code. Also - mark this LABEL_REF so we know that this branch should predict - false. */ - - if (dest_loop != loop_num && loop_num != -1) - { - LABEL_OUTSIDE_LOOP_P (x) = 1; - LABEL_NEXTREF (x) = loop_number_exit_labels[loop_num]; - loop_number_exit_labels[loop_num] = x; - } - - /* If this is inside a loop, but not in the current loop or one enclosed - by it, it invalidates at least one loop. */ - - if (dest_loop == -1) - return; - - /* We must invalidate every nested loop containing the target of this - label, except those that also contain the jump insn. */ - - for (; dest_loop != -1; dest_loop = loop_outer_loop[dest_loop]) - { - /* Stop when we reach a loop that also contains the jump insn. */ - for (outer_loop = loop_num; outer_loop != -1; - outer_loop = loop_outer_loop[outer_loop]) - if (dest_loop == outer_loop) - return; - - /* If we get here, we know we need to invalidate a loop. */ - if (loop_dump_stream && ! loop_invalid[dest_loop]) - fprintf (loop_dump_stream, - "\nLoop at %d ignored due to multiple entry points.\n", - INSN_UID (loop_number_loop_starts[dest_loop])); - - loop_invalid[dest_loop] = 1; - } - return; - - case SET: - /* If this is not setting pc, ignore. */ - if (SET_DEST (x) == pc_rtx) - mark_loop_jump (SET_SRC (x), loop_num); - return; - - case IF_THEN_ELSE: - mark_loop_jump (XEXP (x, 1), loop_num); - mark_loop_jump (XEXP (x, 2), loop_num); - return; - - case PARALLEL: - case ADDR_VEC: - for (i = 0; i < XVECLEN (x, 0); i++) - mark_loop_jump (XVECEXP (x, 0, i), loop_num); - return; - - case ADDR_DIFF_VEC: - for (i = 0; i < XVECLEN (x, 1); i++) - mark_loop_jump (XVECEXP (x, 1, i), loop_num); - return; - - default: - /* Nothing else should occur in a JUMP_INSN. */ - abort (); - } -} - -/* Return nonzero if there is a label in the range from - insn INSN to and including the insn whose luid is END - INSN must have an assigned luid (i.e., it must not have - been previously created by loop.c). */ - -static int -labels_in_range_p (insn, end) - rtx insn; - int end; -{ - while (insn && INSN_LUID (insn) <= end) - { - if (GET_CODE (insn) == CODE_LABEL) - return 1; - insn = NEXT_INSN (insn); - } - - return 0; -} - -/* Record that a memory reference X is being set. */ - -static void -note_addr_stored (x) - rtx x; -{ - register int i; - - if (x == 0 || GET_CODE (x) != MEM) - return; - - /* Count number of memory writes. - This affects heuristics in strength_reduce. */ - num_mem_sets++; - - if (unknown_address_altered) - return; - - for (i = 0; i < loop_store_mems_idx; i++) - if (rtx_equal_p (XEXP (loop_store_mems[i], 0), XEXP (x, 0)) - && MEM_IN_STRUCT_P (x) == MEM_IN_STRUCT_P (loop_store_mems[i])) - { - /* We are storing at the same address as previously noted. Save the - wider reference, treating BLKmode as wider. */ - if (GET_MODE (x) == BLKmode - || (GET_MODE_SIZE (GET_MODE (x)) - > GET_MODE_SIZE (GET_MODE (loop_store_mems[i])))) - loop_store_mems[i] = x; - break; - } - - if (i == NUM_STORES) - unknown_address_altered = 1; - - else if (i == loop_store_mems_idx) - loop_store_mems[loop_store_mems_idx++] = x; -} - -/* Return nonzero if the rtx X is invariant over the current loop. - - The value is 2 if we refer to something only conditionally invariant. - - If `unknown_address_altered' is nonzero, no memory ref is invariant. - Otherwise, a memory ref is invariant if it does not conflict with - anything stored in `loop_store_mems'. */ - -int -invariant_p (x) - register rtx x; -{ - register int i; - register enum rtx_code code; - register char *fmt; - int conditional = 0; - - if (x == 0) - return 1; - code = GET_CODE (x); - switch (code) - { - case CONST_INT: - case CONST_DOUBLE: - case SYMBOL_REF: - case CONST: - return 1; - - case LABEL_REF: - /* A LABEL_REF is normally invariant, however, if we are unrolling - loops, and this label is inside the loop, then it isn't invariant. - This is because each unrolled copy of the loop body will have - a copy of this label. If this was invariant, then an insn loading - the address of this label into a register might get moved outside - the loop, and then each loop body would end up using the same label. - - We don't know the loop bounds here though, so just fail for all - labels. */ - if (flag_unroll_loops) - return 0; - else - return 1; - - case PC: - case CC0: - case UNSPEC_VOLATILE: - return 0; - - case REG: - /* We used to check RTX_UNCHANGING_P (x) here, but that is invalid - since the reg might be set by initialization within the loop. */ - if (x == frame_pointer_rtx || x == arg_pointer_rtx) - return 1; - if (loop_has_call - && REGNO (x) < FIRST_PSEUDO_REGISTER && call_used_regs[REGNO (x)]) - return 0; - if (n_times_set[REGNO (x)] < 0) - return 2; - return n_times_set[REGNO (x)] == 0; - - case MEM: - /* Read-only items (such as constants in a constant pool) are - invariant if their address is. */ - if (RTX_UNCHANGING_P (x)) - break; - - /* If we filled the table (or had a subroutine call), any location - in memory could have been clobbered. */ - if (unknown_address_altered - /* Don't mess with volatile memory references. */ - || MEM_VOLATILE_P (x)) - return 0; - - /* See if there is any dependence between a store and this load. */ - for (i = loop_store_mems_idx - 1; i >= 0; i--) - if (true_dependence (loop_store_mems[i], x)) - return 0; - - /* It's not invalidated by a store in memory - but we must still verify the address is invariant. */ - break; - - case ASM_OPERANDS: - /* Don't mess with insns declared volatile. */ - if (MEM_VOLATILE_P (x)) - return 0; - } - - fmt = GET_RTX_FORMAT (code); - for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--) - { - if (fmt[i] == 'e') - { - int tem = invariant_p (XEXP (x, i)); - if (tem == 0) - return 0; - if (tem == 2) - conditional = 1; - } - else if (fmt[i] == 'E') - { - register int j; - for (j = 0; j < XVECLEN (x, i); j++) - { - int tem = invariant_p (XVECEXP (x, i, j)); - if (tem == 0) - return 0; - if (tem == 2) - conditional = 1; - } - - } - } - - return 1 + conditional; -} - - -/* Return nonzero if all the insns in the loop that set REG - are INSN and the immediately following insns, - and if each of those insns sets REG in an invariant way - (not counting uses of REG in them). - - The value is 2 if some of these insns are only conditionally invariant. - - We assume that INSN itself is the first set of REG - and that its source is invariant. */ - -static int -consec_sets_invariant_p (reg, n_sets, insn) - int n_sets; - rtx reg, insn; -{ - register rtx p = insn; - register int regno = REGNO (reg); - rtx temp; - /* Number of sets we have to insist on finding after INSN. */ - int count = n_sets - 1; - int old = n_times_set[regno]; - int value = 0; - int this; - - /* If N_SETS hit the limit, we can't rely on its value. */ - if (n_sets == 127) - return 0; - - n_times_set[regno] = 0; - - while (count > 0) - { - register enum rtx_code code; - rtx set; - - p = NEXT_INSN (p); - code = GET_CODE (p); - - /* If library call, skip to end of of it. */ - if (code == INSN && (temp = find_reg_note (p, REG_LIBCALL, NULL_RTX))) - p = XEXP (temp, 0); - - this = 0; - if (code == INSN - && (set = single_set (p)) - && GET_CODE (SET_DEST (set)) == REG - && REGNO (SET_DEST (set)) == regno) - { - this = invariant_p (SET_SRC (set)); - if (this != 0) - value |= this; - else if (temp = find_reg_note (p, REG_EQUAL, NULL_RTX)) - { - /* If this is a libcall, then any invariant REG_EQUAL note is OK. - If this is an ordinary insn, then only CONSTANT_P REG_EQUAL - notes are OK. */ - this = (CONSTANT_P (XEXP (temp, 0)) - || (find_reg_note (p, REG_RETVAL, NULL_RTX) - && invariant_p (XEXP (temp, 0)))); - if (this != 0) - value |= this; - } - } - if (this != 0) - count--; - else if (code != NOTE) - { - n_times_set[regno] = old; - return 0; - } - } - - n_times_set[regno] = old; - /* If invariant_p ever returned 2, we return 2. */ - return 1 + (value & 2); -} - -#if 0 -/* I don't think this condition is sufficient to allow INSN - to be moved, so we no longer test it. */ - -/* Return 1 if all insns in the basic block of INSN and following INSN - that set REG are invariant according to TABLE. */ - -static int -all_sets_invariant_p (reg, insn, table) - rtx reg, insn; - short *table; -{ - register rtx p = insn; - register int regno = REGNO (reg); - - while (1) - { - register enum rtx_code code; - p = NEXT_INSN (p); - code = GET_CODE (p); - if (code == CODE_LABEL || code == JUMP_INSN) - return 1; - if (code == INSN && GET_CODE (PATTERN (p)) == SET - && GET_CODE (SET_DEST (PATTERN (p))) == REG - && REGNO (SET_DEST (PATTERN (p))) == regno) - { - if (!invariant_p (SET_SRC (PATTERN (p)), table)) - return 0; - } - } -} -#endif /* 0 */ - -/* Look at all uses (not sets) of registers in X. For each, if it is - the single use, set USAGE[REGNO] to INSN; if there was a previous use in - a different insn, set USAGE[REGNO] to const0_rtx. */ - -static void -find_single_use_in_loop (insn, x, usage) - rtx insn; - rtx x; - rtx *usage; -{ - enum rtx_code code = GET_CODE (x); - char *fmt = GET_RTX_FORMAT (code); - int i, j; - - if (code == REG) - usage[REGNO (x)] - = (usage[REGNO (x)] != 0 && usage[REGNO (x)] != insn) - ? const0_rtx : insn; - - else if (code == SET) - { - /* Don't count SET_DEST if it is a REG; otherwise count things - in SET_DEST because if a register is partially modified, it won't - show up as a potential movable so we don't care how USAGE is set - for it. */ - if (GET_CODE (SET_DEST (x)) != REG) - find_single_use_in_loop (insn, SET_DEST (x), usage); - find_single_use_in_loop (insn, SET_SRC (x), usage); - } - else - for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--) - { - if (fmt[i] == 'e' && XEXP (x, i) != 0) - find_single_use_in_loop (insn, XEXP (x, i), usage); - else if (fmt[i] == 'E') - for (j = XVECLEN (x, i) - 1; j >= 0; j--) - find_single_use_in_loop (insn, XVECEXP (x, i, j), usage); - } -} - -/* Increment N_TIMES_SET at the index of each register - that is modified by an insn between FROM and TO. - If the value of an element of N_TIMES_SET becomes 127 or more, - stop incrementing it, to avoid overflow. - - Store in SINGLE_USAGE[I] the single insn in which register I is - used, if it is only used once. Otherwise, it is set to 0 (for no - uses) or const0_rtx for more than one use. This parameter may be zero, - in which case this processing is not done. - - Store in *COUNT_PTR the number of actual instruction - in the loop. We use this to decide what is worth moving out. */ - -/* last_set[n] is nonzero iff reg n has been set in the current basic block. - In that case, it is the insn that last set reg n. */ - -static void -count_loop_regs_set (from, to, may_not_move, single_usage, count_ptr, nregs) - register rtx from, to; - char *may_not_move; - rtx *single_usage; - int *count_ptr; - int nregs; -{ - register rtx *last_set = (rtx *) alloca (nregs * sizeof (rtx)); - register rtx insn; - register int count = 0; - register rtx dest; - - bzero (last_set, nregs * sizeof (rtx)); - for (insn = from; insn != to; insn = NEXT_INSN (insn)) - { - if (GET_RTX_CLASS (GET_CODE (insn)) == 'i') - { - ++count; - - /* If requested, record registers that have exactly one use. */ - if (single_usage) - { - find_single_use_in_loop (insn, PATTERN (insn), single_usage); - - /* Include uses in REG_EQUAL notes. */ - if (REG_NOTES (insn)) - find_single_use_in_loop (insn, REG_NOTES (insn), single_usage); - } - - if (GET_CODE (PATTERN (insn)) == CLOBBER - && GET_CODE (XEXP (PATTERN (insn), 0)) == REG) - /* Don't move a reg that has an explicit clobber. - We might do so sometimes, but it's not worth the pain. */ - may_not_move[REGNO (XEXP (PATTERN (insn), 0))] = 1; - - if (GET_CODE (PATTERN (insn)) == SET - || GET_CODE (PATTERN (insn)) == CLOBBER) - { - dest = SET_DEST (PATTERN (insn)); - while (GET_CODE (dest) == SUBREG - || GET_CODE (dest) == ZERO_EXTRACT - || GET_CODE (dest) == SIGN_EXTRACT - || GET_CODE (dest) == STRICT_LOW_PART) - dest = XEXP (dest, 0); - if (GET_CODE (dest) == REG) - { - register int regno = REGNO (dest); - /* If this is the first setting of this reg - in current basic block, and it was set before, - it must be set in two basic blocks, so it cannot - be moved out of the loop. */ - if (n_times_set[regno] > 0 && last_set[regno] == 0) - may_not_move[regno] = 1; - /* If this is not first setting in current basic block, - see if reg was used in between previous one and this. - If so, neither one can be moved. */ - if (last_set[regno] != 0 - && reg_used_between_p (dest, last_set[regno], insn)) - may_not_move[regno] = 1; - if (n_times_set[regno] < 127) - ++n_times_set[regno]; - last_set[regno] = insn; - } - } - else if (GET_CODE (PATTERN (insn)) == PARALLEL) - { - register int i; - for (i = XVECLEN (PATTERN (insn), 0) - 1; i >= 0; i--) - { - register rtx x = XVECEXP (PATTERN (insn), 0, i); - if (GET_CODE (x) == CLOBBER && GET_CODE (XEXP (x, 0)) == REG) - /* Don't move a reg that has an explicit clobber. - It's not worth the pain to try to do it correctly. */ - may_not_move[REGNO (XEXP (x, 0))] = 1; - - if (GET_CODE (x) == SET || GET_CODE (x) == CLOBBER) - { - dest = SET_DEST (x); - while (GET_CODE (dest) == SUBREG - || GET_CODE (dest) == ZERO_EXTRACT - || GET_CODE (dest) == SIGN_EXTRACT - || GET_CODE (dest) == STRICT_LOW_PART) - dest = XEXP (dest, 0); - if (GET_CODE (dest) == REG) - { - register int regno = REGNO (dest); - if (n_times_set[regno] > 0 && last_set[regno] == 0) - may_not_move[regno] = 1; - if (last_set[regno] != 0 - && reg_used_between_p (dest, last_set[regno], insn)) - may_not_move[regno] = 1; - if (n_times_set[regno] < 127) - ++n_times_set[regno]; - last_set[regno] = insn; - } - } - } - } - } - if (GET_CODE (insn) == CODE_LABEL || GET_CODE (insn) == JUMP_INSN) - bzero (last_set, nregs * sizeof (rtx)); - } - *count_ptr = count; -} - -/* Given a loop that is bounded by LOOP_START and LOOP_END - and that is entered at SCAN_START, - return 1 if the register set in SET contained in insn INSN is used by - any insn that precedes INSN in cyclic order starting - from the loop entry point. - - We don't want to use INSN_LUID here because if we restrict INSN to those - that have a valid INSN_LUID, it means we cannot move an invariant out - from an inner loop past two loops. */ - -static int -loop_reg_used_before_p (set, insn, loop_start, scan_start, loop_end) - rtx set, insn, loop_start, scan_start, loop_end; -{ - rtx reg = SET_DEST (set); - rtx p; - - /* Scan forward checking for register usage. If we hit INSN, we - are done. Otherwise, if we hit LOOP_END, wrap around to LOOP_START. */ - for (p = scan_start; p != insn; p = NEXT_INSN (p)) - { - if (GET_RTX_CLASS (GET_CODE (p)) == 'i' - && reg_overlap_mentioned_p (reg, PATTERN (p))) - return 1; - - if (p == loop_end) - p = loop_start; - } - - return 0; -} - -/* A "basic induction variable" or biv is a pseudo reg that is set - (within this loop) only by incrementing or decrementing it. */ -/* A "general induction variable" or giv is a pseudo reg whose - value is a linear function of a biv. */ - -/* Bivs are recognized by `basic_induction_var'; - Givs by `general_induct_var'. */ - -/* Indexed by register number, indicates whether or not register is an - induction variable, and if so what type. */ - -enum iv_mode *reg_iv_type; - -/* Indexed by register number, contains pointer to `struct induction' - if register is an induction variable. This holds general info for - all induction variables. */ - -struct induction **reg_iv_info; - -/* Indexed by register number, contains pointer to `struct iv_class' - if register is a basic induction variable. This holds info describing - the class (a related group) of induction variables that the biv belongs - to. */ - -struct iv_class **reg_biv_class; - -/* The head of a list which links together (via the next field) - every iv class for the current loop. */ - -struct iv_class *loop_iv_list; - -/* Communication with routines called via `note_stores'. */ - -static rtx note_insn; - -/* Dummy register to have non-zero DEST_REG for DEST_ADDR type givs. */ - -static rtx addr_placeholder; - -/* ??? Unfinished optimizations, and possible future optimizations, - for the strength reduction code. */ - -/* ??? There is one more optimization you might be interested in doing: to - allocate pseudo registers for frequently-accessed memory locations. - If the same memory location is referenced each time around, it might - be possible to copy it into a register before and out after. - This is especially useful when the memory location is a variable which - is in a stack slot because somewhere its address is taken. If the - loop doesn't contain a function call and the variable isn't volatile, - it is safe to keep the value in a register for the duration of the - loop. One tricky thing is that the copying of the value back from the - register has to be done on all exits from the loop. You need to check that - all the exits from the loop go to the same place. */ - -/* ??? The interaction of biv elimination, and recognition of 'constant' - bivs, may cause problems. */ - -/* ??? Add heuristics so that DEST_ADDR strength reduction does not cause - performance problems. - - Perhaps don't eliminate things that can be combined with an addressing - mode. Find all givs that have the same biv, mult_val, and add_val; - then for each giv, check to see if its only use dies in a following - memory address. If so, generate a new memory address and check to see - if it is valid. If it is valid, then store the modified memory address, - otherwise, mark the giv as not done so that it will get its own iv. */ - -/* ??? Could try to optimize branches when it is known that a biv is always - positive. */ - -/* ??? When replace a biv in a compare insn, we should replace with closest - giv so that an optimized branch can still be recognized by the combiner, - e.g. the VAX acb insn. */ - -/* ??? Many of the checks involving uid_luid could be simplified if regscan - was rerun in loop_optimize whenever a register was added or moved. - Also, some of the optimizations could be a little less conservative. */ - -/* Perform strength reduction and induction variable elimination. */ - -/* Pseudo registers created during this function will be beyond the last - valid index in several tables including n_times_set and regno_last_uid. - This does not cause a problem here, because the added registers cannot be - givs outside of their loop, and hence will never be reconsidered. - But scan_loop must check regnos to make sure they are in bounds. */ - -static void -strength_reduce (scan_start, end, loop_top, insn_count, - loop_start, loop_end) - rtx scan_start; - rtx end; - rtx loop_top; - int insn_count; - rtx loop_start; - rtx loop_end; -{ - rtx p; - rtx set; - rtx inc_val; - rtx mult_val; - rtx dest_reg; - /* This is 1 if current insn is not executed at least once for every loop - iteration. */ - int not_every_iteration = 0; - /* This is 1 if current insn may be executed more than once for every - loop iteration. */ - int maybe_multiple = 0; - /* Temporary list pointers for traversing loop_iv_list. */ - struct iv_class *bl, **backbl; - /* Ratio of extra register life span we can justify - for saving an instruction. More if loop doesn't call subroutines - since in that case saving an insn makes more difference - and more registers are available. */ - /* ??? could set this to last value of threshold in move_movables */ - int threshold = (loop_has_call ? 1 : 2) * (3 + n_non_fixed_regs); - /* Map of pseudo-register replacements. */ - rtx *reg_map; - int call_seen; - rtx test; - rtx end_insert_before; - - reg_iv_type = (enum iv_mode *) alloca (max_reg_before_loop - * sizeof (enum iv_mode *)); - bzero ((char *) reg_iv_type, max_reg_before_loop * sizeof (enum iv_mode *)); - reg_iv_info = (struct induction **) - alloca (max_reg_before_loop * sizeof (struct induction *)); - bzero ((char *) reg_iv_info, (max_reg_before_loop - * sizeof (struct induction *))); - reg_biv_class = (struct iv_class **) - alloca (max_reg_before_loop * sizeof (struct iv_class *)); - bzero ((char *) reg_biv_class, (max_reg_before_loop - * sizeof (struct iv_class *))); - - loop_iv_list = 0; - addr_placeholder = gen_reg_rtx (Pmode); - - /* Save insn immediately after the loop_end. Insns inserted after loop_end - must be put before this insn, so that they will appear in the right - order (i.e. loop order). - - If loop_end is the end of the current function, then emit a - NOTE_INSN_DELETED after loop_end and set end_insert_before to the - dummy note insn. */ - if (NEXT_INSN (loop_end) != 0) - end_insert_before = NEXT_INSN (loop_end); - else - end_insert_before = emit_note_after (NOTE_INSN_DELETED, loop_end); - - /* Scan through loop to find all possible bivs. */ - - p = scan_start; - while (1) - { - p = NEXT_INSN (p); - /* At end of a straight-in loop, we are done. - At end of a loop entered at the bottom, scan the top. */ - if (p == scan_start) - break; - if (p == end) - { - if (loop_top != 0) - p = NEXT_INSN (loop_top); - else - break; - if (p == scan_start) - break; - } - - if (GET_CODE (p) == INSN - && (set = single_set (p)) - && GET_CODE (SET_DEST (set)) == REG) - { - dest_reg = SET_DEST (set); - if (REGNO (dest_reg) < max_reg_before_loop - && REGNO (dest_reg) >= FIRST_PSEUDO_REGISTER - && reg_iv_type[REGNO (dest_reg)] != NOT_BASIC_INDUCT) - { - if (basic_induction_var (SET_SRC (set), dest_reg, p, - &inc_val, &mult_val)) - { - /* It is a possible basic induction variable. - Create and initialize an induction structure for it. */ - - struct induction *v - = (struct induction *) alloca (sizeof (struct induction)); - - record_biv (v, p, dest_reg, inc_val, mult_val, - not_every_iteration, maybe_multiple); - reg_iv_type[REGNO (dest_reg)] = BASIC_INDUCT; - } - else if (REGNO (dest_reg) < max_reg_before_loop) - reg_iv_type[REGNO (dest_reg)] = NOT_BASIC_INDUCT; - } - } - - /* Past CODE_LABEL, we get to insns that may be executed multiple - times. The only way we can be sure that they can't is if every - every jump insn between here and the end of the loop either - returns, exits the loop, or is a forward jump. */ - - if (GET_CODE (p) == CODE_LABEL) - { - rtx insn = p; - - maybe_multiple = 0; - - while (1) - { - insn = NEXT_INSN (insn); - if (insn == scan_start) - break; - if (insn == end) - { - if (loop_top != 0) - insn = NEXT_INSN (loop_top); - else - break; - if (insn == scan_start) - break; - } - - if (GET_CODE (insn) == JUMP_INSN - && GET_CODE (PATTERN (insn)) != RETURN - && (! condjump_p (insn) - || (JUMP_LABEL (insn) != 0 - && (INSN_UID (JUMP_LABEL (insn)) >= max_uid_for_loop - || INSN_UID (insn) >= max_uid_for_loop - || (INSN_LUID (JUMP_LABEL (insn)) - < INSN_LUID (insn)))))) - { - maybe_multiple = 1; - break; - } - } - } - - /* Past a label or a jump, we get to insns for which we can't count - on whether or how many times they will be executed during each - iteration. */ - /* This code appears in three places, once in scan_loop, and twice - in strength_reduce. */ - if ((GET_CODE (p) == CODE_LABEL || GET_CODE (p) == JUMP_INSN) - /* If we enter the loop in the middle, and scan around to the - beginning, don't set not_every_iteration for that. - This can be any kind of jump, since we want to know if insns - will be executed if the loop is executed. */ - && ! (GET_CODE (p) == JUMP_INSN && JUMP_LABEL (p) == loop_top - && ((NEXT_INSN (NEXT_INSN (p)) == loop_end && simplejump_p (p)) - || (NEXT_INSN (p) == loop_end && condjump_p (p))))) - not_every_iteration = 1; - - /* At the virtual top of a converted loop, insns are again known to - be executed each iteration: logically, the loop begins here - even though the exit code has been duplicated. */ - - else if (GET_CODE (p) == NOTE - && NOTE_LINE_NUMBER (p) == NOTE_INSN_LOOP_VTOP) - not_every_iteration = 0; - - /* Unlike in the code motion pass where MAYBE_NEVER indicates that - an insn may never be executed, NOT_EVERY_ITERATION indicates whether - or not an insn is known to be executed each iteration of the - loop, whether or not any iterations are known to occur. - - Therefore, if we have just passed a label and have no more labels - between here and the test insn of the loop, we know these insns - will be executed each iteration. This can also happen if we - have just passed a jump, for example, when there are nested loops. */ - - if (not_every_iteration && GET_CODE (p) == CODE_LABEL - && no_labels_between_p (p, loop_end)) - not_every_iteration = 0; - } - - /* Scan loop_iv_list to remove all regs that proved not to be bivs. - Make a sanity check against n_times_set. */ - for (backbl = &loop_iv_list, bl = *backbl; bl; bl = bl->next) - { - if (reg_iv_type[bl->regno] != BASIC_INDUCT - /* Above happens if register modified by subreg, etc. */ - /* Make sure it is not recognized as a basic induction var: */ - || n_times_set[bl->regno] != bl->biv_count - /* If never incremented, it is invariant that we decided not to - move. So leave it alone. */ - || ! bl->incremented) - { - if (loop_dump_stream) - fprintf (loop_dump_stream, "Reg %d: biv discarded, %s\n", - bl->regno, - (reg_iv_type[bl->regno] != BASIC_INDUCT - ? "not induction variable" - : (! bl->incremented ? "never incremented" - : "count error"))); - - reg_iv_type[bl->regno] = NOT_BASIC_INDUCT; - *backbl = bl->next; - } - else - { - backbl = &bl->next; - - if (loop_dump_stream) - fprintf (loop_dump_stream, "Reg %d: biv verified\n", bl->regno); - } - } - - /* Exit if there are no bivs. */ - if (! loop_iv_list) - { - /* Can still unroll the loop anyways, but indicate that there is no - strength reduction info available. */ - if (flag_unroll_loops) - unroll_loop (loop_end, insn_count, loop_start, end_insert_before, 0); - - return; - } - - /* Find initial value for each biv by searching backwards from loop_start, - halting at first label. Also record any test condition. */ - - call_seen = 0; - for (p = loop_start; p && GET_CODE (p) != CODE_LABEL; p = PREV_INSN (p)) - { - note_insn = p; - - if (GET_CODE (p) == CALL_INSN) - call_seen = 1; - - if (GET_CODE (p) == INSN || GET_CODE (p) == JUMP_INSN - || GET_CODE (p) == CALL_INSN) - note_stores (PATTERN (p), record_initial); - - /* Record any test of a biv that branches around the loop if no store - between it and the start of loop. We only care about tests with - constants and registers and only certain of those. */ - if (GET_CODE (p) == JUMP_INSN - && JUMP_LABEL (p) != 0 - && next_real_insn (JUMP_LABEL (p)) == next_real_insn (loop_end) - && (test = get_condition_for_loop (p)) != 0 - && GET_CODE (XEXP (test, 0)) == REG - && REGNO (XEXP (test, 0)) < max_reg_before_loop - && (bl = reg_biv_class[REGNO (XEXP (test, 0))]) != 0 - && valid_initial_value_p (XEXP (test, 1), p, call_seen, loop_start) - && bl->init_insn == 0) - { - /* If an NE test, we have an initial value! */ - if (GET_CODE (test) == NE) - { - bl->init_insn = p; - bl->init_set = gen_rtx (SET, VOIDmode, - XEXP (test, 0), XEXP (test, 1)); - } - else - bl->initial_test = test; - } - } - - /* Look at the each biv and see if we can say anything better about its - initial value from any initializing insns set up above. (This is done - in two passes to avoid missing SETs in a PARALLEL.) */ - for (bl = loop_iv_list; bl; bl = bl->next) - { - rtx src; - - if (! bl->init_insn) - continue; - - src = SET_SRC (bl->init_set); - - if (loop_dump_stream) - fprintf (loop_dump_stream, - "Biv %d initialized at insn %d: initial value ", - bl->regno, INSN_UID (bl->init_insn)); - - if (valid_initial_value_p (src, bl->init_insn, call_seen, loop_start)) - { - bl->initial_value = src; - - if (loop_dump_stream) - { - if (GET_CODE (src) == CONST_INT) - fprintf (loop_dump_stream, "%d\n", INTVAL (src)); - else - { - print_rtl (loop_dump_stream, src); - fprintf (loop_dump_stream, "\n"); - } - } - } - else - { - /* Biv initial value is not simple move, - so let it keep initial value of "itself". */ - - if (loop_dump_stream) - fprintf (loop_dump_stream, "is complex\n"); - } - } - - /* Search the loop for general induction variables. */ - - /* A register is a giv if: it is only set once, it is a function of a - biv and a constant (or invariant), and it is not a biv. */ - - not_every_iteration = 0; - p = scan_start; - while (1) - { - p = NEXT_INSN (p); - /* At end of a straight-in loop, we are done. - At end of a loop entered at the bottom, scan the top. */ - if (p == scan_start) - break; - if (p == end) - { - if (loop_top != 0) - p = NEXT_INSN (loop_top); - else - break; - if (p == scan_start) - break; - } - - /* Look for a general induction variable in a register. */ - if (GET_CODE (p) == INSN - && (set = single_set (p)) - && GET_CODE (SET_DEST (set)) == REG - && ! may_not_optimize[REGNO (SET_DEST (set))]) - { - rtx src_reg; - rtx add_val; - rtx mult_val; - int benefit; - rtx regnote = 0; - - dest_reg = SET_DEST (set); - if (REGNO (dest_reg) < FIRST_PSEUDO_REGISTER) - continue; - - if (/* SET_SRC is a giv. */ - ((benefit = general_induction_var (SET_SRC (set), - &src_reg, &add_val, - &mult_val)) - /* Equivalent expression is a giv. */ - || ((regnote = find_reg_note (p, REG_EQUAL, NULL_RTX)) - && (benefit = general_induction_var (XEXP (regnote, 0), - &src_reg, - &add_val, &mult_val)))) - /* Don't try to handle any regs made by loop optimization. - We have nothing on them in regno_first_uid, etc. */ - && REGNO (dest_reg) < max_reg_before_loop - /* Don't recognize a BASIC_INDUCT_VAR here. */ - && dest_reg != src_reg - /* This must be the only place where the register is set. */ - && (n_times_set[REGNO (dest_reg)] == 1 - /* or all sets must be consecutive and make a giv. */ - || (benefit = consec_sets_giv (benefit, p, - src_reg, dest_reg, - &add_val, &mult_val)))) - { - int count; - struct induction *v - = (struct induction *) alloca (sizeof (struct induction)); - rtx temp; - - /* If this is a library call, increase benefit. */ - if (find_reg_note (p, REG_RETVAL, NULL_RTX)) - benefit += libcall_benefit (p); - - /* Skip the consecutive insns, if there are any. */ - for (count = n_times_set[REGNO (dest_reg)] - 1; - count > 0; count--) - { - /* If first insn of libcall sequence, skip to end. - Do this at start of loop, since INSN is guaranteed to - be an insn here. */ - if (GET_CODE (p) != NOTE - && (temp = find_reg_note (p, REG_LIBCALL, NULL_RTX))) - p = XEXP (temp, 0); - - do p = NEXT_INSN (p); - while (GET_CODE (p) == NOTE); - } - - record_giv (v, p, src_reg, dest_reg, mult_val, add_val, benefit, - DEST_REG, not_every_iteration, NULL_PTR, loop_start, - loop_end); - - } - } - -#ifndef DONT_REDUCE_ADDR - /* Look for givs which are memory addresses. */ - /* This resulted in worse code on a VAX 8600. I wonder if it - still does. */ - if (GET_CODE (p) == INSN) - find_mem_givs (PATTERN (p), p, not_every_iteration, loop_start, - loop_end); -#endif - - /* Update the status of whether giv can derive other givs. This can - change when we pass a label or an insn that updates a biv. */ - if (GET_CODE (p) == INSN || GET_CODE (p) == JUMP_INSN - || GET_CODE (p) == CODE_LABEL) - update_giv_derive (p); - - /* Past a label or a jump, we get to insns for which we can't count - on whether or how many times they will be executed during each - iteration. */ - /* This code appears in three places, once in scan_loop, and twice - in strength_reduce. */ - if ((GET_CODE (p) == CODE_LABEL || GET_CODE (p) == JUMP_INSN) - /* If we enter the loop in the middle, and scan around - to the beginning, don't set not_every_iteration for that. - This can be any kind of jump, since we want to know if insns - will be executed if the loop is executed. */ - && ! (GET_CODE (p) == JUMP_INSN && JUMP_LABEL (p) == loop_top - && ((NEXT_INSN (NEXT_INSN (p)) == loop_end && simplejump_p (p)) - || (NEXT_INSN (p) == loop_end && condjump_p (p))))) - not_every_iteration = 1; - - /* At the virtual top of a converted loop, insns are again known to - be executed each iteration: logically, the loop begins here - even though the exit code has been duplicated. */ - - else if (GET_CODE (p) == NOTE - && NOTE_LINE_NUMBER (p) == NOTE_INSN_LOOP_VTOP) - not_every_iteration = 0; - - /* Unlike in the code motion pass where MAYBE_NEVER indicates that - an insn may never be executed, NOT_EVERY_ITERATION indicates whether - or not an insn is known to be executed each iteration of the - loop, whether or not any iterations are known to occur. - - Therefore, if we have just passed a label and have no more labels - between here and the test insn of the loop, we know these insns - will be executed each iteration. */ - - if (not_every_iteration && GET_CODE (p) == CODE_LABEL - && no_labels_between_p (p, loop_end)) - not_every_iteration = 0; - } - - /* Try to calculate and save the number of loop iterations. This is - set to zero if the actual number can not be calculated. This must - be called after all giv's have been identified, since otherwise it may - fail if the iteration variable is a giv. */ - - loop_n_iterations = loop_iterations (loop_start, loop_end); - - /* Now for each giv for which we still don't know whether or not it is - replaceable, check to see if it is replaceable because its final value - can be calculated. This must be done after loop_iterations is called, - so that final_giv_value will work correctly. */ - - for (bl = loop_iv_list; bl; bl = bl->next) - { - struct induction *v; - - for (v = bl->giv; v; v = v->next_iv) - if (! v->replaceable && ! v->not_replaceable) - check_final_value (v, loop_start, loop_end); - } - - /* Try to prove that the loop counter variable (if any) is always - nonnegative; if so, record that fact with a REG_NONNEG note - so that "decrement and branch until zero" insn can be used. */ - check_dbra_loop (loop_end, insn_count, loop_start); - - /* Create reg_map to hold substitutions for replaceable giv regs. */ - reg_map = (rtx *) alloca (max_reg_before_loop * sizeof (rtx)); - bzero ((char *) reg_map, max_reg_before_loop * sizeof (rtx)); - - /* Examine each iv class for feasibility of strength reduction/induction - variable elimination. */ - - for (bl = loop_iv_list; bl; bl = bl->next) - { - struct induction *v; - int benefit; - int all_reduced; - rtx final_value = 0; - - /* Test whether it will be possible to eliminate this biv - provided all givs are reduced. This is possible if either - the reg is not used outside the loop, or we can compute - what its final value will be. - - For architectures with a decrement_and_branch_until_zero insn, - don't do this if we put a REG_NONNEG note on the endtest for - this biv. */ - - /* Compare against bl->init_insn rather than loop_start. - We aren't concerned with any uses of the biv between - init_insn and loop_start since these won't be affected - by the value of the biv elsewhere in the function, so - long as init_insn doesn't use the biv itself. - March 14, 1989 -- self@bayes.arc.nasa.gov */ - - if ((uid_luid[regno_last_uid[bl->regno]] < INSN_LUID (loop_end) - && bl->init_insn - && INSN_UID (bl->init_insn) < max_uid_for_loop - && uid_luid[regno_first_uid[bl->regno]] >= INSN_LUID (bl->init_insn) -#ifdef HAVE_decrement_and_branch_until_zero - && ! bl->nonneg -#endif - && ! reg_mentioned_p (bl->biv->dest_reg, SET_SRC (bl->init_set))) - || ((final_value = final_biv_value (bl, loop_start, loop_end)) -#ifdef HAVE_decrement_and_branch_until_zero - && ! bl->nonneg -#endif - )) - bl->eliminable = maybe_eliminate_biv (bl, loop_start, end, 0, - threshold, insn_count); - else - { - if (loop_dump_stream) - { - fprintf (loop_dump_stream, - "Cannot eliminate biv %d.\n", - bl->regno); - fprintf (loop_dump_stream, - "First use: insn %d, last use: insn %d.\n", - regno_first_uid[bl->regno], - regno_last_uid[bl->regno]); - } - } - - /* Combine all giv's for this iv_class. */ - combine_givs (bl); - - /* This will be true at the end, if all givs which depend on this - biv have been strength reduced. - We can't (currently) eliminate the biv unless this is so. */ - all_reduced = 1; - - /* Check each giv in this class to see if we will benefit by reducing - it. Skip giv's combined with others. */ - for (v = bl->giv; v; v = v->next_iv) - { - struct induction *tv; - - if (v->ignore || v->same) - continue; - - benefit = v->benefit; - - /* Reduce benefit if not replaceable, since we will insert - a move-insn to replace the insn that calculates this giv. - Don't do this unless the giv is a user variable, since it - will often be marked non-replaceable because of the duplication - of the exit code outside the loop. In such a case, the copies - we insert are dead and will be deleted. So they don't have - a cost. Similar situations exist. */ - /* ??? The new final_[bg]iv_value code does a much better job - of finding replaceable giv's, and hence this code may no longer - be necessary. */ - if (! v->replaceable && ! bl->eliminable - && REG_USERVAR_P (v->dest_reg)) - benefit -= copy_cost; - - /* Decrease the benefit to count the add-insns that we will - insert to increment the reduced reg for the giv. */ - benefit -= add_cost * bl->biv_count; - - /* Decide whether to strength-reduce this giv or to leave the code - unchanged (recompute it from the biv each time it is used). - This decision can be made independently for each giv. */ - - /* ??? Perhaps attempt to guess whether autoincrement will handle - some of the new add insns; if so, can increase BENEFIT - (undo the subtraction of add_cost that was done above). */ - - /* If an insn is not to be strength reduced, then set its ignore - flag, and clear all_reduced. */ - - if (v->lifetime * threshold * benefit < insn_count) - { - if (loop_dump_stream) - fprintf (loop_dump_stream, - "giv of insn %d not worth while, %d vs %d.\n", - INSN_UID (v->insn), - v->lifetime * threshold * benefit, insn_count); - v->ignore = 1; - all_reduced = 0; - } - else - { - /* Check that we can increment the reduced giv without a - multiply insn. If not, reject it. */ - - for (tv = bl->biv; tv; tv = tv->next_iv) - if (tv->mult_val == const1_rtx - && ! product_cheap_p (tv->add_val, v->mult_val)) - { - if (loop_dump_stream) - fprintf (loop_dump_stream, - "giv of insn %d: would need a multiply.\n", - INSN_UID (v->insn)); - v->ignore = 1; - all_reduced = 0; - break; - } - } - } - - /* Reduce each giv that we decided to reduce. */ - - for (v = bl->giv; v; v = v->next_iv) - { - struct induction *tv; - if (! v->ignore && v->same == 0) - { - v->new_reg = gen_reg_rtx (v->mode); - - /* For each place where the biv is incremented, - add an insn to increment the new, reduced reg for the giv. */ - for (tv = bl->biv; tv; tv = tv->next_iv) - { - if (tv->mult_val == const1_rtx) - emit_iv_add_mult (tv->add_val, v->mult_val, - v->new_reg, v->new_reg, tv->insn); - else /* tv->mult_val == const0_rtx */ - /* A multiply is acceptable here - since this is presumed to be seldom executed. */ - emit_iv_add_mult (tv->add_val, v->mult_val, - v->add_val, v->new_reg, tv->insn); - } - - /* Add code at loop start to initialize giv's reduced reg. */ - - emit_iv_add_mult (bl->initial_value, v->mult_val, - v->add_val, v->new_reg, loop_start); - } - } - - /* Rescan all givs. If a giv is the same as a giv not reduced, mark it - as not reduced. - - For each giv register that can be reduced now: if replaceable, - substitute reduced reg wherever the old giv occurs; - else add new move insn "giv_reg = reduced_reg". - - Also check for givs whose first use is their definition and whose - last use is the definition of another giv. If so, it is likely - dead and should not be used to eliminate a biv. */ - for (v = bl->giv; v; v = v->next_iv) - { - if (v->same && v->same->ignore) - v->ignore = 1; - - if (v->ignore) - continue; - - if (v->giv_type == DEST_REG - && regno_first_uid[REGNO (v->dest_reg)] == INSN_UID (v->insn)) - { - struct induction *v1; - - for (v1 = bl->giv; v1; v1 = v1->next_iv) - if (regno_last_uid[REGNO (v->dest_reg)] == INSN_UID (v1->insn)) - v->maybe_dead = 1; - } - - /* Update expression if this was combined, in case other giv was - replaced. */ - if (v->same) - v->new_reg = replace_rtx (v->new_reg, - v->same->dest_reg, v->same->new_reg); - - if (v->giv_type == DEST_ADDR) - /* Store reduced reg as the address in the memref where we found - this giv. */ - *v->location = v->new_reg; - else if (v->replaceable) - { - reg_map[REGNO (v->dest_reg)] = v->new_reg; - -#if 0 - /* I can no longer duplicate the original problem. Perhaps - this is unnecessary now? */ - - /* Replaceable; it isn't strictly necessary to delete the old - insn and emit a new one, because v->dest_reg is now dead. - - However, especially when unrolling loops, the special - handling for (set REG0 REG1) in the second cse pass may - make v->dest_reg live again. To avoid this problem, emit - an insn to set the original giv reg from the reduced giv. - We can not delete the original insn, since it may be part - of a LIBCALL, and the code in flow that eliminates dead - libcalls will fail if it is deleted. */ - emit_insn_after (gen_move_insn (v->dest_reg, v->new_reg), - v->insn); -#endif - } - else - { - /* Not replaceable; emit an insn to set the original giv reg from - the reduced giv, same as above. */ - emit_insn_after (gen_move_insn (v->dest_reg, v->new_reg), - v->insn); - } - - /* When a loop is reversed, givs which depend on the reversed - biv, and which are live outside the loop, must be set to their - correct final value. This insn is only needed if the giv is - not replaceable. The correct final value is the same as the - value that the giv starts the reversed loop with. */ - if (bl->reversed && ! v->replaceable) - emit_iv_add_mult (bl->initial_value, v->mult_val, - v->add_val, v->dest_reg, end_insert_before); - else if (v->final_value) - { - rtx insert_before; - - /* If the loop has multiple exits, emit the insn before the - loop to ensure that it will always be executed no matter - how the loop exits. Otherwise, emit the insn after the loop, - since this is slightly more efficient. */ - if (loop_number_exit_labels[uid_loop_num[INSN_UID (loop_start)]]) - insert_before = loop_start; - else - insert_before = end_insert_before; - emit_insn_before (gen_move_insn (v->dest_reg, v->final_value), - insert_before); - -#if 0 - /* If the insn to set the final value of the giv was emitted - before the loop, then we must delete the insn inside the loop - that sets it. If this is a LIBCALL, then we must delete - every insn in the libcall. Note, however, that - final_giv_value will only succeed when there are multiple - exits if the giv is dead at each exit, hence it does not - matter that the original insn remains because it is dead - anyways. */ - /* Delete the insn inside the loop that sets the giv since - the giv is now set before (or after) the loop. */ - delete_insn (v->insn); -#endif - } - - if (loop_dump_stream) - { - fprintf (loop_dump_stream, "giv at %d reduced to ", - INSN_UID (v->insn)); - print_rtl (loop_dump_stream, v->new_reg); - fprintf (loop_dump_stream, "\n"); - } - } - - /* All the givs based on the biv bl have been reduced if they - merit it. */ - - /* For each giv not marked as maybe dead that has been combined with a - second giv, clear any "maybe dead" mark on that second giv. - v->new_reg will either be or refer to the register of the giv it - combined with. - - Doing this clearing avoids problems in biv elimination where a - giv's new_reg is a complex value that can't be put in the insn but - the giv combined with (with a reg as new_reg) is marked maybe_dead. - Since the register will be used in either case, we'd prefer it be - used from the simpler giv. */ - - for (v = bl->giv; v; v = v->next_iv) - if (! v->maybe_dead && v->same) - v->same->maybe_dead = 0; - - /* Try to eliminate the biv, if it is a candidate. - This won't work if ! all_reduced, - since the givs we planned to use might not have been reduced. - - We have to be careful that we didn't initially think we could eliminate - this biv because of a giv that we now think may be dead and shouldn't - be used as a biv replacement. - - Also, there is the possibility that we may have a giv that looks - like it can be used to eliminate a biv, but the resulting insn - isn't valid. This can happen, for example, on the 88k, where a - JUMP_INSN can compare a register only with zero. Attempts to - replace it with a compare with a constant will fail. - - Note that in cases where this call fails, we may have replaced some - of the occurrences of the biv with a giv, but no harm was done in - doing so in the rare cases where it can occur. */ - - if (all_reduced == 1 && bl->eliminable - && maybe_eliminate_biv (bl, loop_start, end, 1, - threshold, insn_count)) - - { - /* ?? If we created a new test to bypass the loop entirely, - or otherwise drop straight in, based on this test, then - we might want to rewrite it also. This way some later - pass has more hope of removing the initialization of this - biv entirely. */ - - /* If final_value != 0, then the biv may be used after loop end - and we must emit an insn to set it just in case. - - Reversed bivs already have an insn after the loop setting their - value, so we don't need another one. We can't calculate the - proper final value for such a biv here anyways. */ - if (final_value != 0 && ! bl->reversed) - { - rtx insert_before; - - /* If the loop has multiple exits, emit the insn before the - loop to ensure that it will always be executed no matter - how the loop exits. Otherwise, emit the insn after the - loop, since this is slightly more efficient. */ - if (loop_number_exit_labels[uid_loop_num[INSN_UID (loop_start)]]) - insert_before = loop_start; - else - insert_before = end_insert_before; - - emit_insn_before (gen_move_insn (bl->biv->dest_reg, final_value), - end_insert_before); - } - -#if 0 - /* Delete all of the instructions inside the loop which set - the biv, as they are all dead. If is safe to delete them, - because an insn setting a biv will never be part of a libcall. */ - /* However, deleting them will invalidate the regno_last_uid info, - so keeping them around is more convenient. Final_biv_value - will only succeed when there are multiple exits if the biv - is dead at each exit, hence it does not matter that the original - insn remains, because it is dead anyways. */ - for (v = bl->biv; v; v = v->next_iv) - delete_insn (v->insn); -#endif - - if (loop_dump_stream) - fprintf (loop_dump_stream, "Reg %d: biv eliminated\n", - bl->regno); - } - } - - /* Go through all the instructions in the loop, making all the - register substitutions scheduled in REG_MAP. */ - - for (p = loop_start; p != end; p = NEXT_INSN (p)) - if (GET_CODE (p) == INSN || GET_CODE (p) == JUMP_INSN - || GET_CODE (p) == CALL_INSN) - { - replace_regs (PATTERN (p), reg_map, max_reg_before_loop, 0); - replace_regs (REG_NOTES (p), reg_map, max_reg_before_loop, 0); - INSN_CODE (p) = -1; - } - - /* Unroll loops from within strength reduction so that we can use the - induction variable information that strength_reduce has already - collected. */ - - if (flag_unroll_loops) - unroll_loop (loop_end, insn_count, loop_start, end_insert_before, 1); - - if (loop_dump_stream) - fprintf (loop_dump_stream, "\n"); -} - -/* Return 1 if X is a valid source for an initial value (or as value being - compared against in an initial test). - - X must be either a register or constant and must not be clobbered between - the current insn and the start of the loop. - - INSN is the insn containing X. */ - -static int -valid_initial_value_p (x, insn, call_seen, loop_start) - rtx x; - rtx insn; - int call_seen; - rtx loop_start; -{ - if (CONSTANT_P (x)) - return 1; - - /* Only consider pseudos we know about initialized in insns whose luids - we know. */ - if (GET_CODE (x) != REG - || REGNO (x) >= max_reg_before_loop) - return 0; - - /* Don't use call-clobbered registers across a call which clobbers it. On - some machines, don't use any hard registers at all. */ - if (REGNO (x) < FIRST_PSEUDO_REGISTER -#ifndef SMALL_REGISTER_CLASSES - && call_used_regs[REGNO (x)] && call_seen -#endif - ) - return 0; - - /* Don't use registers that have been clobbered before the start of the - loop. */ - if (reg_set_between_p (x, insn, loop_start)) - return 0; - - return 1; -} - -/* Scan X for memory refs and check each memory address - as a possible giv. INSN is the insn whose pattern X comes from. - NOT_EVERY_ITERATION is 1 if the insn might not be executed during - every loop iteration. */ - -static void -find_mem_givs (x, insn, not_every_iteration, loop_start, loop_end) - rtx x; - rtx insn; - int not_every_iteration; - rtx loop_start, loop_end; -{ - register int i, j; - register enum rtx_code code; - register char *fmt; - - if (x == 0) - return; - - code = GET_CODE (x); - switch (code) - { - case REG: - case CONST_INT: - case CONST: - case CONST_DOUBLE: - case SYMBOL_REF: - case LABEL_REF: - case PC: - case CC0: - case ADDR_VEC: - case ADDR_DIFF_VEC: - case USE: - case CLOBBER: - return; - - case MEM: - { - rtx src_reg; - rtx add_val; - rtx mult_val; - int benefit; - - benefit = general_induction_var (XEXP (x, 0), - &src_reg, &add_val, &mult_val); - - /* Don't make a DEST_ADDR giv with mult_val == 1 && add_val == 0. - Such a giv isn't useful. */ - if (benefit > 0 && (mult_val != const1_rtx || add_val != const0_rtx)) - { - /* Found one; record it. */ - struct induction *v - = (struct induction *) oballoc (sizeof (struct induction)); - - record_giv (v, insn, src_reg, addr_placeholder, mult_val, - add_val, benefit, DEST_ADDR, not_every_iteration, - &XEXP (x, 0), loop_start, loop_end); - - v->mem_mode = GET_MODE (x); - } - return; - } - } - - /* Recursively scan the subexpressions for other mem refs. */ - - fmt = GET_RTX_FORMAT (code); - for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--) - if (fmt[i] == 'e') - find_mem_givs (XEXP (x, i), insn, not_every_iteration, loop_start, - loop_end); - else if (fmt[i] == 'E') - for (j = 0; j < XVECLEN (x, i); j++) - find_mem_givs (XVECEXP (x, i, j), insn, not_every_iteration, - loop_start, loop_end); -} - -/* Fill in the data about one biv update. - V is the `struct induction' in which we record the biv. (It is - allocated by the caller, with alloca.) - INSN is the insn that sets it. - DEST_REG is the biv's reg. - - MULT_VAL is const1_rtx if the biv is being incremented here, in which case - INC_VAL is the increment. Otherwise, MULT_VAL is const0_rtx and the biv is - being set to INC_VAL. - - NOT_EVERY_ITERATION is nonzero if this biv update is not know to be - executed every iteration; MAYBE_MULTIPLE is nonzero if this biv update - can be executed more than once per iteration. If MAYBE_MULTIPLE - and NOT_EVERY_ITERATION are both zero, we know that the biv update is - executed exactly once per iteration. */ - -static void -record_biv (v, insn, dest_reg, inc_val, mult_val, - not_every_iteration, maybe_multiple) - struct induction *v; - rtx insn; - rtx dest_reg; - rtx inc_val; - rtx mult_val; - int not_every_iteration; - int maybe_multiple; -{ - struct iv_class *bl; - - v->insn = insn; - v->src_reg = dest_reg; - v->dest_reg = dest_reg; - v->mult_val = mult_val; - v->add_val = inc_val; - v->mode = GET_MODE (dest_reg); - v->always_computable = ! not_every_iteration; - v->maybe_multiple = maybe_multiple; - - /* Add this to the reg's iv_class, creating a class - if this is the first incrementation of the reg. */ - - bl = reg_biv_class[REGNO (dest_reg)]; - if (bl == 0) - { - /* Create and initialize new iv_class. */ - - bl = (struct iv_class *) oballoc (sizeof (struct iv_class)); - - bl->regno = REGNO (dest_reg); - bl->biv = 0; - bl->giv = 0; - bl->biv_count = 0; - bl->giv_count = 0; - - /* Set initial value to the reg itself. */ - bl->initial_value = dest_reg; - /* We haven't seen the initializing insn yet */ - bl->init_insn = 0; - bl->init_set = 0; - bl->initial_test = 0; - bl->incremented = 0; - bl->eliminable = 0; - bl->nonneg = 0; - bl->reversed = 0; - bl->total_benefit = 0; - - /* Add this class to loop_iv_list. */ - bl->next = loop_iv_list; - loop_iv_list = bl; - - /* Put it in the array of biv register classes. */ - reg_biv_class[REGNO (dest_reg)] = bl; - } - - /* Update IV_CLASS entry for this biv. */ - v->next_iv = bl->biv; - bl->biv = v; - bl->biv_count++; - if (mult_val == const1_rtx) - bl->incremented = 1; - - if (loop_dump_stream) - { - fprintf (loop_dump_stream, - "Insn %d: possible biv, reg %d,", - INSN_UID (insn), REGNO (dest_reg)); - if (GET_CODE (inc_val) == CONST_INT) - fprintf (loop_dump_stream, " const = %d\n", - INTVAL (inc_val)); - else - { - fprintf (loop_dump_stream, " const = "); - print_rtl (loop_dump_stream, inc_val); - fprintf (loop_dump_stream, "\n"); - } - } -} - -/* Fill in the data about one giv. - V is the `struct induction' in which we record the giv. (It is - allocated by the caller, with alloca.) - INSN is the insn that sets it. - BENEFIT estimates the savings from deleting this insn. - TYPE is DEST_REG or DEST_ADDR; it says whether the giv is computed - into a register or is used as a memory address. - - SRC_REG is the biv reg which the giv is computed from. - DEST_REG is the giv's reg (if the giv is stored in a reg). - MULT_VAL and ADD_VAL are the coefficients used to compute the giv. - LOCATION points to the place where this giv's value appears in INSN. */ - -static void -record_giv (v, insn, src_reg, dest_reg, mult_val, add_val, benefit, - type, not_every_iteration, location, loop_start, loop_end) - struct induction *v; - rtx insn; - rtx src_reg; - rtx dest_reg; - rtx mult_val, add_val; - int benefit; - enum g_types type; - int not_every_iteration; - rtx *location; - rtx loop_start, loop_end; -{ - struct induction *b; - struct iv_class *bl; - rtx set = single_set (insn); - rtx p; - - v->insn = insn; - v->src_reg = src_reg; - v->giv_type = type; - v->dest_reg = dest_reg; - v->mult_val = mult_val; - v->add_val = add_val; - v->benefit = benefit; - v->location = location; - v->cant_derive = 0; - v->combined_with = 0; - v->maybe_multiple = 0; - v->maybe_dead = 0; - v->derive_adjustment = 0; - v->same = 0; - v->ignore = 0; - v->new_reg = 0; - v->final_value = 0; - - /* The v->always_computable field is used in update_giv_derive, to - determine whether a giv can be used to derive another giv. For a - DEST_REG giv, INSN computes a new value for the giv, so its value - isn't computable if INSN insn't executed every iteration. - However, for a DEST_ADDR giv, INSN merely uses the value of the giv; - it does not compute a new value. Hence the value is always computable - regardless of whether INSN is executed each iteration. */ - - if (type == DEST_ADDR) - v->always_computable = 1; - else - v->always_computable = ! not_every_iteration; - - if (type == DEST_ADDR) - { - v->mode = GET_MODE (*location); - v->lifetime = 1; - v->times_used = 1; - } - else /* type == DEST_REG */ - { - v->mode = GET_MODE (SET_DEST (set)); - - v->lifetime = (uid_luid[regno_last_uid[REGNO (dest_reg)]] - - uid_luid[regno_first_uid[REGNO (dest_reg)]]); - - v->times_used = n_times_used[REGNO (dest_reg)]; - - /* If the lifetime is zero, it means that this register is - really a dead store. So mark this as a giv that can be - ignored. This will not prevent the biv from being eliminated. */ - if (v->lifetime == 0) - v->ignore = 1; - - reg_iv_type[REGNO (dest_reg)] = GENERAL_INDUCT; - reg_iv_info[REGNO (dest_reg)] = v; - } - - /* Add the giv to the class of givs computed from one biv. */ - - bl = reg_biv_class[REGNO (src_reg)]; - if (bl) - { - v->next_iv = bl->giv; - bl->giv = v; - /* Don't count DEST_ADDR. This is supposed to count the number of - insns that calculate givs. */ - if (type == DEST_REG) - bl->giv_count++; - bl->total_benefit += benefit; - } - else - /* Fatal error, biv missing for this giv? */ - abort (); - - if (type == DEST_ADDR) - v->replaceable = 1; - else - { - /* The giv can be replaced outright by the reduced register only if all - of the following conditions are true: - - the insn that sets the giv is always executed on any iteration - on which the giv is used at all - (there are two ways to deduce this: - either the insn is executed on every iteration, - or all uses follow that insn in the same basic block), - - the giv is not used outside the loop - - no assignments to the biv occur during the giv's lifetime. */ - - if (regno_first_uid[REGNO (dest_reg)] == INSN_UID (insn) - /* Previous line always fails if INSN was moved by loop opt. */ - && uid_luid[regno_last_uid[REGNO (dest_reg)]] < INSN_LUID (loop_end) - && (! not_every_iteration - || last_use_this_basic_block (dest_reg, insn))) - { - /* Now check that there are no assignments to the biv within the - giv's lifetime. This requires two separate checks. */ - - /* Check each biv update, and fail if any are between the first - and last use of the giv. - - If this loop contains an inner loop that was unrolled, then - the insn modifying the biv may have been emitted by the loop - unrolling code, and hence does not have a valid luid. Just - mark the biv as not replaceable in this case. It is not very - useful as a biv, because it is used in two different loops. - It is very unlikely that we would be able to optimize the giv - using this biv anyways. */ - - v->replaceable = 1; - for (b = bl->biv; b; b = b->next_iv) - { - if (INSN_UID (b->insn) >= max_uid_for_loop - || ((uid_luid[INSN_UID (b->insn)] - >= uid_luid[regno_first_uid[REGNO (dest_reg)]]) - && (uid_luid[INSN_UID (b->insn)] - <= uid_luid[regno_last_uid[REGNO (dest_reg)]]))) - { - v->replaceable = 0; - v->not_replaceable = 1; - break; - } - } - - /* Check each insn between the first and last use of the giv, - and fail if any of them are branches that jump to a named label - outside this range, but still inside the loop. This catches - cases of spaghetti code where the execution order of insns - is not linear, and hence the above test fails. For example, - in the following code, j is not replaceable: - for (i = 0; i < 100; ) { - L0: j = 4*i; goto L1; - L2: k = j; goto L3; - L1: i++; goto L2; - L3: ; } - printf ("k = %d\n", k); } - This test is conservative, but this test succeeds rarely enough - that it isn't a problem. See also check_final_value below. */ - - if (v->replaceable) - for (p = insn; - INSN_UID (p) >= max_uid_for_loop - || INSN_LUID (p) < uid_luid[regno_last_uid[REGNO (dest_reg)]]; - p = NEXT_INSN (p)) - { - if (GET_CODE (p) == JUMP_INSN && JUMP_LABEL (p) - && LABEL_NAME (JUMP_LABEL (p)) - && ((INSN_LUID (JUMP_LABEL (p)) > INSN_LUID (loop_start) - && (INSN_LUID (JUMP_LABEL (p)) - < uid_luid[regno_first_uid[REGNO (dest_reg)]])) - || (INSN_LUID (JUMP_LABEL (p)) < INSN_LUID (loop_end) - && (INSN_LUID (JUMP_LABEL (p)) - > uid_luid[regno_last_uid[REGNO (dest_reg)]])))) - { - v->replaceable = 0; - v->not_replaceable = 1; - - if (loop_dump_stream) - fprintf (loop_dump_stream, - "Found branch outside giv lifetime.\n"); - - break; - } - } - } - else - { - /* May still be replaceable, we don't have enough info here to - decide. */ - v->replaceable = 0; - v->not_replaceable = 0; - } - } - - if (loop_dump_stream) - { - if (type == DEST_REG) - fprintf (loop_dump_stream, "Insn %d: giv reg %d", - INSN_UID (insn), REGNO (dest_reg)); - else - fprintf (loop_dump_stream, "Insn %d: dest address", - INSN_UID (insn)); - - fprintf (loop_dump_stream, " src reg %d benefit %d", - REGNO (src_reg), v->benefit); - fprintf (loop_dump_stream, " used %d lifetime %d", - v->times_used, v->lifetime); - - if (v->replaceable) - fprintf (loop_dump_stream, " replaceable"); - - if (GET_CODE (mult_val) == CONST_INT) - fprintf (loop_dump_stream, " mult %d", - INTVAL (mult_val)); - else - { - fprintf (loop_dump_stream, " mult "); - print_rtl (loop_dump_stream, mult_val); - } - - if (GET_CODE (add_val) == CONST_INT) - fprintf (loop_dump_stream, " add %d", - INTVAL (add_val)); - else - { - fprintf (loop_dump_stream, " add "); - print_rtl (loop_dump_stream, add_val); - } - } - - if (loop_dump_stream) - fprintf (loop_dump_stream, "\n"); - -} - - -/* All this does is determine whether a giv can be made replaceable because - its final value can be calculated. This code can not be part of record_giv - above, because final_giv_value requires that the number of loop iterations - be known, and that can not be accurately calculated until after all givs - have been identified. */ - -static void -check_final_value (v, loop_start, loop_end) - struct induction *v; - rtx loop_start, loop_end; -{ - struct iv_class *bl; - rtx final_value = 0; - rtx tem; - - bl = reg_biv_class[REGNO (v->src_reg)]; - - /* DEST_ADDR givs will never reach here, because they are always marked - replaceable above in record_giv. */ - - /* The giv can be replaced outright by the reduced register only if all - of the following conditions are true: - - the insn that sets the giv is always executed on any iteration - on which the giv is used at all - (there are two ways to deduce this: - either the insn is executed on every iteration, - or all uses follow that insn in the same basic block), - - its final value can be calculated (this condition is different - than the one above in record_giv) - - no assignments to the biv occur during the giv's lifetime. */ - -#if 0 - /* This is only called now when replaceable is known to be false. */ - /* Clear replaceable, so that it won't confuse final_giv_value. */ - v->replaceable = 0; -#endif - - if ((final_value = final_giv_value (v, loop_start, loop_end)) - && (v->always_computable || last_use_this_basic_block (v->dest_reg, v->insn))) - { - int biv_increment_seen = 0; - rtx p = v->insn; - rtx last_giv_use; - - v->replaceable = 1; - - /* When trying to determine whether or not a biv increment occurs - during the lifetime of the giv, we can ignore uses of the variable - outside the loop because final_value is true. Hence we can not - use regno_last_uid and regno_first_uid as above in record_giv. */ - - /* Search the loop to determine whether any assignments to the - biv occur during the giv's lifetime. Start with the insn - that sets the giv, and search around the loop until we come - back to that insn again. - - Also fail if there is a jump within the giv's lifetime that jumps - to somewhere outside the lifetime but still within the loop. This - catches spaghetti code where the execution order is not linear, and - hence the above test fails. Here we assume that the giv lifetime - does not extend from one iteration of the loop to the next, so as - to make the test easier. Since the lifetime isn't known yet, - this requires two loops. See also record_giv above. */ - - last_giv_use = v->insn; - - while (1) - { - p = NEXT_INSN (p); - if (p == loop_end) - p = NEXT_INSN (loop_start); - if (p == v->insn) - break; - - if (GET_CODE (p) == INSN || GET_CODE (p) == JUMP_INSN - || GET_CODE (p) == CALL_INSN) - { - if (biv_increment_seen) - { - if (reg_mentioned_p (v->dest_reg, PATTERN (p))) - { - v->replaceable = 0; - v->not_replaceable = 1; - break; - } - } - else if (GET_CODE (PATTERN (p)) == SET - && SET_DEST (PATTERN (p)) == v->src_reg) - biv_increment_seen = 1; - else if (reg_mentioned_p (v->dest_reg, PATTERN (p))) - last_giv_use = p; - } - } - - /* Now that the lifetime of the giv is known, check for branches - from within the lifetime to outside the lifetime if it is still - replaceable. */ - - if (v->replaceable) - { - p = v->insn; - while (1) - { - p = NEXT_INSN (p); - if (p == loop_end) - p = NEXT_INSN (loop_start); - if (p == last_giv_use) - break; - - if (GET_CODE (p) == JUMP_INSN && JUMP_LABEL (p) - && LABEL_NAME (JUMP_LABEL (p)) - && ((INSN_LUID (JUMP_LABEL (p)) < INSN_LUID (v->insn) - && INSN_LUID (JUMP_LABEL (p)) > INSN_LUID (loop_start)) - || (INSN_LUID (JUMP_LABEL (p)) > INSN_LUID (last_giv_use) - && INSN_LUID (JUMP_LABEL (p)) < INSN_LUID (loop_end)))) - { - v->replaceable = 0; - v->not_replaceable = 1; - - if (loop_dump_stream) - fprintf (loop_dump_stream, - "Found branch outside giv lifetime.\n"); - - break; - } - } - } - - /* If it is replaceable, then save the final value. */ - if (v->replaceable) - v->final_value = final_value; - } - - if (loop_dump_stream && v->replaceable) - fprintf (loop_dump_stream, "Insn %d: giv reg %d final_value replaceable\n", - INSN_UID (v->insn), REGNO (v->dest_reg)); -} - -/* Update the status of whether a giv can derive other givs. - - We need to do something special if there is or may be an update to the biv - between the time the giv is defined and the time it is used to derive - another giv. - - In addition, a giv that is only conditionally set is not allowed to - derive another giv once a label has been passed. - - The cases we look at are when a label or an update to a biv is passed. */ - -static void -update_giv_derive (p) - rtx p; -{ - struct iv_class *bl; - struct induction *biv, *giv; - rtx tem; - int dummy; - - /* Search all IV classes, then all bivs, and finally all givs. - - There are three cases we are concerned with. First we have the situation - of a giv that is only updated conditionally. In that case, it may not - derive any givs after a label is passed. - - The second case is when a biv update occurs, or may occur, after the - definition of a giv. For certain biv updates (see below) that are - known to occur between the giv definition and use, we can adjust the - giv definition. For others, or when the biv update is conditional, - we must prevent the giv from deriving any other givs. There are two - sub-cases within this case. - - If this is a label, we are concerned with any biv update that is done - conditionally, since it may be done after the giv is defined followed by - a branch here (actually, we need to pass both a jump and a label, but - this extra tracking doesn't seem worth it). - - If this is a jump, we are concerned about any biv update that may be - executed multiple times. We are actually only concerned about - backward jumps, but it is probably not worth performing the test - on the jump again here. - - If this is a biv update, we must adjust the giv status to show that a - subsequent biv update was performed. If this adjustment cannot be done, - the giv cannot derive further givs. */ - - for (bl = loop_iv_list; bl; bl = bl->next) - for (biv = bl->biv; biv; biv = biv->next_iv) - if (GET_CODE (p) == CODE_LABEL || GET_CODE (p) == JUMP_INSN - || biv->insn == p) - { - for (giv = bl->giv; giv; giv = giv->next_iv) - { - /* If cant_derive is already true, there is no point in - checking all of these conditions again. */ - if (giv->cant_derive) - continue; - - /* If this giv is conditionally set and we have passed a label, - it cannot derive anything. */ - if (GET_CODE (p) == CODE_LABEL && ! giv->always_computable) - giv->cant_derive = 1; - - /* Skip givs that have mult_val == 0, since - they are really invariants. Also skip those that are - replaceable, since we know their lifetime doesn't contain - any biv update. */ - else if (giv->mult_val == const0_rtx || giv->replaceable) - continue; - - /* The only way we can allow this giv to derive another - is if this is a biv increment and we can form the product - of biv->add_val and giv->mult_val. In this case, we will - be able to compute a compensation. */ - else if (biv->insn == p) - { - tem = 0; - - if (biv->mult_val == const1_rtx) - tem = simplify_giv_expr (gen_rtx (MULT, giv->mode, - biv->add_val, - giv->mult_val), - &dummy); - - if (tem && giv->derive_adjustment) - tem = simplify_giv_expr (gen_rtx (PLUS, giv->mode, tem, - giv->derive_adjustment), - &dummy); - if (tem) - giv->derive_adjustment = tem; - else - giv->cant_derive = 1; - } - else if ((GET_CODE (p) == CODE_LABEL && ! biv->always_computable) - || (GET_CODE (p) == JUMP_INSN && biv->maybe_multiple)) - giv->cant_derive = 1; - } - } -} - -/* Check whether an insn is an increment legitimate for a basic induction var. - X is the source of insn P. - DEST_REG is the putative biv, also the destination of the insn. - We accept patterns of these forms: - REG = REG + INVARIANT (includes REG = REG - CONSTANT) - REG = INVARIANT + REG - - If X is suitable, we return 1, set *MULT_VAL to CONST1_RTX, - and store the additive term into *INC_VAL. - - If X is an assignment of an invariant into DEST_REG, we set - *MULT_VAL to CONST0_RTX, and store the invariant into *INC_VAL. - - We also want to detect a BIV when it corresponds to a variable - whose mode was promoted via PROMOTED_MODE. In that case, an increment - of the variable may be a PLUS that adds a SUBREG of that variable to - an invariant and then sign- or zero-extends the result of the PLUS - into the variable. - - Most GIVs in such cases will be in the promoted mode, since that is the - probably the natural computation mode (and almost certainly the mode - used for addresses) on the machine. So we view the pseudo-reg containing - the variable as the BIV, as if it were simply incremented. - - Note that treating the entire pseudo as a BIV will result in making - simple increments to any GIVs based on it. However, if the variable - overflows in its declared mode but not its promoted mode, the result will - be incorrect. This is acceptable if the variable is signed, since - overflows in such cases are undefined, but not if it is unsigned, since - those overflows are defined. So we only check for SIGN_EXTEND and - not ZERO_EXTEND. - - If we cannot find a biv, we return 0. */ - -static int -basic_induction_var (x, dest_reg, p, inc_val, mult_val) - register rtx x; - rtx p; - rtx dest_reg; - rtx *inc_val; - rtx *mult_val; -{ - register enum rtx_code code; - rtx arg; - rtx insn, set = 0; - - code = GET_CODE (x); - switch (code) - { - case PLUS: - if (XEXP (x, 0) == dest_reg - || (GET_CODE (XEXP (x, 0)) == SUBREG - && SUBREG_PROMOTED_VAR_P (XEXP (x, 0)) - && SUBREG_REG (XEXP (x, 0)) == dest_reg)) - arg = XEXP (x, 1); - else if (XEXP (x, 1) == dest_reg - || (GET_CODE (XEXP (x, 1)) == SUBREG - && SUBREG_PROMOTED_VAR_P (XEXP (x, 1)) - && SUBREG_REG (XEXP (x, 1)) == dest_reg)) - arg = XEXP (x, 0); - else - return 0; - - if (invariant_p (arg) != 1) - return 0; - - *inc_val = convert_to_mode (GET_MODE (dest_reg), arg, 0);; - *mult_val = const1_rtx; - return 1; - - case SUBREG: - /* If this is a SUBREG for a promoted variable, check the inner - value. */ - if (SUBREG_PROMOTED_VAR_P (x)) - return basic_induction_var (SUBREG_REG (x), dest_reg, p, - inc_val, mult_val); - - case REG: - /* If this register is assigned in the previous insn, look at its - source, but don't go outside the loop or past a label. */ - - for (insn = PREV_INSN (p); - (insn && GET_CODE (insn) == NOTE - && NOTE_LINE_NUMBER (insn) != NOTE_INSN_LOOP_BEG); - insn = PREV_INSN (insn)) - ; - - if (insn) - set = single_set (insn); - - if (set != 0 && SET_DEST (set) == x) - return basic_induction_var (SET_SRC (set), dest_reg, insn, - inc_val, mult_val); - /* ... fall through ... */ - - /* Can accept constant setting of biv only when inside inner most loop. - Otherwise, a biv of an inner loop may be incorrectly recognized - as a biv of the outer loop, - causing code to be moved INTO the inner loop. */ - case MEM: - if (invariant_p (x) != 1) - return 0; - case CONST_INT: - case SYMBOL_REF: - case CONST: - if (loops_enclosed == 1) - { - *inc_val = convert_to_mode (GET_MODE (dest_reg), x, 0);; - *mult_val = const0_rtx; - return 1; - } - else - return 0; - - case SIGN_EXTEND: - return basic_induction_var (XEXP (x, 0), dest_reg, p, - inc_val, mult_val); - case ASHIFTRT: - /* Similar, since this can be a sign extension. */ - for (insn = PREV_INSN (p); - (insn && GET_CODE (insn) == NOTE - && NOTE_LINE_NUMBER (insn) != NOTE_INSN_LOOP_BEG); - insn = PREV_INSN (insn)) - ; - - if (insn) - set = single_set (insn); - - if (set && SET_DEST (set) == XEXP (x, 0) - && GET_CODE (XEXP (x, 1)) == CONST_INT - && INTVAL (XEXP (x, 1)) >= 0 - && GET_CODE (SET_SRC (set)) == ASHIFT - && XEXP (x, 1) == XEXP (SET_SRC (set), 1)) - return basic_induction_var (XEXP (SET_SRC (set), 0), dest_reg, insn, - inc_val, mult_val); - return 0; - - default: - return 0; - } -} - -/* A general induction variable (giv) is any quantity that is a linear - function of a basic induction variable, - i.e. giv = biv * mult_val + add_val. - The coefficients can be any loop invariant quantity. - A giv need not be computed directly from the biv; - it can be computed by way of other givs. */ - -/* Determine whether X computes a giv. - If it does, return a nonzero value - which is the benefit from eliminating the computation of X; - set *SRC_REG to the register of the biv that it is computed from; - set *ADD_VAL and *MULT_VAL to the coefficients, - such that the value of X is biv * mult + add; */ - -static int -general_induction_var (x, src_reg, add_val, mult_val) - rtx x; - rtx *src_reg; - rtx *add_val; - rtx *mult_val; -{ - rtx orig_x = x; - int benefit = 0; - char *storage; - - /* If this is an invariant, forget it, it isn't a giv. */ - if (invariant_p (x) == 1) - return 0; - - /* See if the expression could be a giv and get its form. - Mark our place on the obstack in case we don't find a giv. */ - storage = (char *) oballoc (0); - x = simplify_giv_expr (x, &benefit); - if (x == 0) - { - obfree (storage); - return 0; - } - - switch (GET_CODE (x)) - { - case USE: - case CONST_INT: - /* Since this is now an invariant and wasn't before, it must be a giv - with MULT_VAL == 0. It doesn't matter which BIV we associate this - with. */ - *src_reg = loop_iv_list->biv->dest_reg; - *mult_val = const0_rtx; - *add_val = x; - break; - - case REG: - /* This is equivalent to a BIV. */ - *src_reg = x; - *mult_val = const1_rtx; - *add_val = const0_rtx; - break; - - case PLUS: - /* Either (plus (biv) (invar)) or - (plus (mult (biv) (invar_1)) (invar_2)). */ - if (GET_CODE (XEXP (x, 0)) == MULT) - { - *src_reg = XEXP (XEXP (x, 0), 0); - *mult_val = XEXP (XEXP (x, 0), 1); - } - else - { - *src_reg = XEXP (x, 0); - *mult_val = const1_rtx; - } - *add_val = XEXP (x, 1); - break; - - case MULT: - /* ADD_VAL is zero. */ - *src_reg = XEXP (x, 0); - *mult_val = XEXP (x, 1); - *add_val = const0_rtx; - break; - - default: - abort (); - } - - /* Remove any enclosing USE from ADD_VAL and MULT_VAL (there will be - unless they are CONST_INT). */ - if (GET_CODE (*add_val) == USE) - *add_val = XEXP (*add_val, 0); - if (GET_CODE (*mult_val) == USE) - *mult_val = XEXP (*mult_val, 0); - - benefit += rtx_cost (orig_x, SET); - - /* Always return some benefit if this is a giv so it will be detected - as such. This allows elimination of bivs that might otherwise - not be eliminated. */ - return benefit == 0 ? 1 : benefit; -} - -/* Given an expression, X, try to form it as a linear function of a biv. - We will canonicalize it to be of the form - (plus (mult (BIV) (invar_1)) - (invar_2)) - with possible degeneracies. - - The invariant expressions must each be of a form that can be used as a - machine operand. We surround then with a USE rtx (a hack, but localized - and certainly unambiguous!) if not a CONST_INT for simplicity in this - routine; it is the caller's responsibility to strip them. - - If no such canonicalization is possible (i.e., two biv's are used or an - expression that is neither invariant nor a biv or giv), this routine - returns 0. - - For a non-zero return, the result will have a code of CONST_INT, USE, - REG (for a BIV), PLUS, or MULT. No other codes will occur. - - *BENEFIT will be incremented by the benefit of any sub-giv encountered. */ - -static rtx -simplify_giv_expr (x, benefit) - rtx x; - int *benefit; -{ - enum machine_mode mode = GET_MODE (x); - rtx arg0, arg1; - rtx tem; - - /* If this is not an integer mode, or if we cannot do arithmetic in this - mode, this can't be a giv. */ - if (mode != VOIDmode - && (GET_MODE_CLASS (mode) != MODE_INT - || GET_MODE_BITSIZE (mode) > HOST_BITS_PER_WIDE_INT)) - return 0; - - switch (GET_CODE (x)) - { - case PLUS: - arg0 = simplify_giv_expr (XEXP (x, 0), benefit); - arg1 = simplify_giv_expr (XEXP (x, 1), benefit); - if (arg0 == 0 || arg1 == 0) - return 0; - - /* Put constant last, CONST_INT last if both constant. */ - if ((GET_CODE (arg0) == USE - || GET_CODE (arg0) == CONST_INT) - && GET_CODE (arg1) != CONST_INT) - tem = arg0, arg0 = arg1, arg1 = tem; - - /* Handle addition of zero, then addition of an invariant. */ - if (arg1 == const0_rtx) - return arg0; - else if (GET_CODE (arg1) == CONST_INT || GET_CODE (arg1) == USE) - switch (GET_CODE (arg0)) - { - case CONST_INT: - case USE: - /* Both invariant. Only valid if sum is machine operand. - First strip off possible USE on first operand. */ - if (GET_CODE (arg0) == USE) - arg0 = XEXP (arg0, 0); - - tem = 0; - if (CONSTANT_P (arg0) && GET_CODE (arg1) == CONST_INT) - { - tem = plus_constant (arg0, INTVAL (arg1)); - if (GET_CODE (tem) != CONST_INT) - tem = gen_rtx (USE, mode, tem); - } - - return tem; - - case REG: - case MULT: - /* biv + invar or mult + invar. Return sum. */ - return gen_rtx (PLUS, mode, arg0, arg1); - - case PLUS: - /* (a + invar_1) + invar_2. Associate. */ - return simplify_giv_expr (gen_rtx (PLUS, mode, - XEXP (arg0, 0), - gen_rtx (PLUS, mode, - XEXP (arg0, 1), arg1)), - benefit); - - default: - abort (); - } - - /* Each argument must be either REG, PLUS, or MULT. Convert REG to - MULT to reduce cases. */ - if (GET_CODE (arg0) == REG) - arg0 = gen_rtx (MULT, mode, arg0, const1_rtx); - if (GET_CODE (arg1) == REG) - arg1 = gen_rtx (MULT, mode, arg1, const1_rtx); - - /* Now have PLUS + PLUS, PLUS + MULT, MULT + PLUS, or MULT + MULT. - Put a MULT first, leaving PLUS + PLUS, MULT + PLUS, or MULT + MULT. - Recurse to associate the second PLUS. */ - if (GET_CODE (arg1) == MULT) - tem = arg0, arg0 = arg1, arg1 = tem; - - if (GET_CODE (arg1) == PLUS) - return simplify_giv_expr (gen_rtx (PLUS, mode, - gen_rtx (PLUS, mode, - arg0, XEXP (arg1, 0)), - XEXP (arg1, 1)), - benefit); - - /* Now must have MULT + MULT. Distribute if same biv, else not giv. */ - if (GET_CODE (arg0) != MULT || GET_CODE (arg1) != MULT) - abort (); - - if (XEXP (arg0, 0) != XEXP (arg1, 0)) - return 0; - - return simplify_giv_expr (gen_rtx (MULT, mode, - XEXP (arg0, 0), - gen_rtx (PLUS, mode, - XEXP (arg0, 1), - XEXP (arg1, 1))), - benefit); - - case MINUS: - /* Handle "a - b" as "a + b * (-1)". */ - return simplify_giv_expr (gen_rtx (PLUS, mode, - XEXP (x, 0), - gen_rtx (MULT, mode, - XEXP (x, 1), constm1_rtx)), - benefit); - - case MULT: - arg0 = simplify_giv_expr (XEXP (x, 0), benefit); - arg1 = simplify_giv_expr (XEXP (x, 1), benefit); - if (arg0 == 0 || arg1 == 0) - return 0; - - /* Put constant last, CONST_INT last if both constant. */ - if ((GET_CODE (arg0) == USE || GET_CODE (arg0) == CONST_INT) - && GET_CODE (arg1) != CONST_INT) - tem = arg0, arg0 = arg1, arg1 = tem; - - /* If second argument is not now constant, not giv. */ - if (GET_CODE (arg1) != USE && GET_CODE (arg1) != CONST_INT) - return 0; - - /* Handle multiply by 0 or 1. */ - if (arg1 == const0_rtx) - return const0_rtx; - - else if (arg1 == const1_rtx) - return arg0; - - switch (GET_CODE (arg0)) - { - case REG: - /* biv * invar. Done. */ - return gen_rtx (MULT, mode, arg0, arg1); - - case CONST_INT: - /* Product of two constants. */ - return GEN_INT (INTVAL (arg0) * INTVAL (arg1)); - - case USE: - /* invar * invar. Not giv. */ - return 0; - - case MULT: - /* (a * invar_1) * invar_2. Associate. */ - return simplify_giv_expr (gen_rtx (MULT, mode, - XEXP (arg0, 0), - gen_rtx (MULT, mode, - XEXP (arg0, 1), arg1)), - benefit); - - case PLUS: - /* (a + invar_1) * invar_2. Distribute. */ - return simplify_giv_expr (gen_rtx (PLUS, mode, - gen_rtx (MULT, mode, - XEXP (arg0, 0), arg1), - gen_rtx (MULT, mode, - XEXP (arg0, 1), arg1)), - benefit); - - default: - abort (); - } - - case ASHIFT: - case LSHIFT: - /* Shift by constant is multiply by power of two. */ - if (GET_CODE (XEXP (x, 1)) != CONST_INT) - return 0; - - return simplify_giv_expr (gen_rtx (MULT, mode, - XEXP (x, 0), - GEN_INT ((HOST_WIDE_INT) 1 - << INTVAL (XEXP (x, 1)))), - benefit); - - case NEG: - /* "-a" is "a * (-1)" */ - return simplify_giv_expr (gen_rtx (MULT, mode, XEXP (x, 0), constm1_rtx), - benefit); - - case NOT: - /* "~a" is "-a - 1". Silly, but easy. */ - return simplify_giv_expr (gen_rtx (MINUS, mode, - gen_rtx (NEG, mode, XEXP (x, 0)), - const1_rtx), - benefit); - - case USE: - /* Already in proper form for invariant. */ - return x; - - case REG: - /* If this is a new register, we can't deal with it. */ - if (REGNO (x) >= max_reg_before_loop) - return 0; - - /* Check for biv or giv. */ - switch (reg_iv_type[REGNO (x)]) - { - case BASIC_INDUCT: - return x; - case GENERAL_INDUCT: - { - struct induction *v = reg_iv_info[REGNO (x)]; - - /* Form expression from giv and add benefit. Ensure this giv - can derive another and subtract any needed adjustment if so. */ - *benefit += v->benefit; - if (v->cant_derive) - return 0; - - tem = gen_rtx (PLUS, mode, gen_rtx (MULT, mode, - v->src_reg, v->mult_val), - v->add_val); - if (v->derive_adjustment) - tem = gen_rtx (MINUS, mode, tem, v->derive_adjustment); - return simplify_giv_expr (tem, benefit); - } - } - - /* Fall through to general case. */ - default: - /* If invariant, return as USE (unless CONST_INT). - Otherwise, not giv. */ - if (GET_CODE (x) == USE) - x = XEXP (x, 0); - - if (invariant_p (x) == 1) - { - if (GET_CODE (x) == CONST_INT) - return x; - else - return gen_rtx (USE, mode, x); - } - else - return 0; - } -} - -/* Help detect a giv that is calculated by several consecutive insns; - for example, - giv = biv * M - giv = giv + A - The caller has already identified the first insn P as having a giv as dest; - we check that all other insns that set the same register follow - immediately after P, that they alter nothing else, - and that the result of the last is still a giv. - - The value is 0 if the reg set in P is not really a giv. - Otherwise, the value is the amount gained by eliminating - all the consecutive insns that compute the value. - - FIRST_BENEFIT is the amount gained by eliminating the first insn, P. - SRC_REG is the reg of the biv; DEST_REG is the reg of the giv. - - The coefficients of the ultimate giv value are stored in - *MULT_VAL and *ADD_VAL. */ - -static int -consec_sets_giv (first_benefit, p, src_reg, dest_reg, - add_val, mult_val) - int first_benefit; - rtx p; - rtx src_reg; - rtx dest_reg; - rtx *add_val; - rtx *mult_val; -{ - int count; - enum rtx_code code; - int benefit; - rtx temp; - rtx set; - - /* Indicate that this is a giv so that we can update the value produced in - each insn of the multi-insn sequence. - - This induction structure will be used only by the call to - general_induction_var below, so we can allocate it on our stack. - If this is a giv, our caller will replace the induct var entry with - a new induction structure. */ - struct induction *v - = (struct induction *) alloca (sizeof (struct induction)); - v->src_reg = src_reg; - v->mult_val = *mult_val; - v->add_val = *add_val; - v->benefit = first_benefit; - v->cant_derive = 0; - v->derive_adjustment = 0; - - reg_iv_type[REGNO (dest_reg)] = GENERAL_INDUCT; - reg_iv_info[REGNO (dest_reg)] = v; - - count = n_times_set[REGNO (dest_reg)] - 1; - - while (count > 0) - { - p = NEXT_INSN (p); - code = GET_CODE (p); - - /* If libcall, skip to end of call sequence. */ - if (code == INSN && (temp = find_reg_note (p, REG_LIBCALL, NULL_RTX))) - p = XEXP (temp, 0); - - if (code == INSN - && (set = single_set (p)) - && GET_CODE (SET_DEST (set)) == REG - && SET_DEST (set) == dest_reg - && ((benefit = general_induction_var (SET_SRC (set), &src_reg, - add_val, mult_val)) - /* Giv created by equivalent expression. */ - || ((temp = find_reg_note (p, REG_EQUAL, NULL_RTX)) - && (benefit = general_induction_var (XEXP (temp, 0), &src_reg, - add_val, mult_val)))) - && src_reg == v->src_reg) - { - if (find_reg_note (p, REG_RETVAL, NULL_RTX)) - benefit += libcall_benefit (p); - - count--; - v->mult_val = *mult_val; - v->add_val = *add_val; - v->benefit = benefit; - } - else if (code != NOTE) - { - /* Allow insns that set something other than this giv to a - constant. Such insns are needed on machines which cannot - include long constants and should not disqualify a giv. */ - if (code == INSN - && (set = single_set (p)) - && SET_DEST (set) != dest_reg - && CONSTANT_P (SET_SRC (set))) - continue; - - reg_iv_type[REGNO (dest_reg)] = UNKNOWN_INDUCT; - return 0; - } - } - - return v->benefit; -} - -/* Return an rtx, if any, that expresses giv G2 as a function of the register - represented by G1. If no such expression can be found, or it is clear that - it cannot possibly be a valid address, 0 is returned. - - To perform the computation, we note that - G1 = a * v + b and - G2 = c * v + d - where `v' is the biv. - - So G2 = (c/a) * G1 + (d - b*c/a) */ - -#ifdef ADDRESS_COST -static rtx -express_from (g1, g2) - struct induction *g1, *g2; -{ - rtx mult, add; - - /* The value that G1 will be multiplied by must be a constant integer. Also, - the only chance we have of getting a valid address is if b*c/a (see above - for notation) is also an integer. */ - if (GET_CODE (g1->mult_val) != CONST_INT - || GET_CODE (g2->mult_val) != CONST_INT - || GET_CODE (g1->add_val) != CONST_INT - || g1->mult_val == const0_rtx - || INTVAL (g2->mult_val) % INTVAL (g1->mult_val) != 0) - return 0; - - mult = GEN_INT (INTVAL (g2->mult_val) / INTVAL (g1->mult_val)); - add = plus_constant (g2->add_val, - INTVAL (g1->add_val) * INTVAL (mult)); - - /* Form simplified final result. */ - if (mult == const0_rtx) - return add; - else if (mult == const1_rtx) - mult = g1->dest_reg; - else - mult = gen_rtx (MULT, g2->mode, g1->dest_reg, mult); - - if (add == const0_rtx) - return mult; - else - return gen_rtx (PLUS, g2->mode, mult, add); -} -#endif - -/* Return 1 if giv G2 can be combined with G1. This means that G2 can use - (either directly or via an address expression) a register used to represent - G1. Set g2->new_reg to a represtation of G1 (normally just - g1->dest_reg). */ - -static int -combine_givs_p (g1, g2) - struct induction *g1, *g2; -{ - rtx tem; - - /* If these givs are identical, they can be combined. */ - if (rtx_equal_p (g1->mult_val, g2->mult_val) - && rtx_equal_p (g1->add_val, g2->add_val)) - { - g2->new_reg = g1->dest_reg; - return 1; - } - -#ifdef ADDRESS_COST - /* If G2 can be expressed as a function of G1 and that function is valid - as an address and no more expensive than using a register for G2, - the expression of G2 in terms of G1 can be used. */ - if (g2->giv_type == DEST_ADDR - && (tem = express_from (g1, g2)) != 0 - && memory_address_p (g2->mem_mode, tem) - && ADDRESS_COST (tem) <= ADDRESS_COST (*g2->location)) - { - g2->new_reg = tem; - return 1; - } -#endif - - return 0; -} - -/* Check all pairs of givs for iv_class BL and see if any can be combined with - any other. If so, point SAME to the giv combined with and set NEW_REG to - be an expression (in terms of the other giv's DEST_REG) equivalent to the - giv. Also, update BENEFIT and related fields for cost/benefit analysis. */ - -static void -combine_givs (bl) - struct iv_class *bl; -{ - struct induction *g1, *g2; - int pass; - - for (g1 = bl->giv; g1; g1 = g1->next_iv) - for (pass = 0; pass <= 1; pass++) - for (g2 = bl->giv; g2; g2 = g2->next_iv) - if (g1 != g2 - /* First try to combine with replaceable givs, then all givs. */ - && (g1->replaceable || pass == 1) - /* If either has already been combined or is to be ignored, can't - combine. */ - && ! g1->ignore && ! g2->ignore && ! g1->same && ! g2->same - /* If something has been based on G2, G2 cannot itself be based - on something else. */ - && ! g2->combined_with - && combine_givs_p (g1, g2)) - { - /* g2->new_reg set by `combine_givs_p' */ - g2->same = g1; - g1->combined_with = 1; - g1->benefit += g2->benefit; - /* ??? The new final_[bg]iv_value code does a much better job - of finding replaceable giv's, and hence this code may no - longer be necessary. */ - if (! g2->replaceable && REG_USERVAR_P (g2->dest_reg)) - g1->benefit -= copy_cost; - g1->lifetime += g2->lifetime; - g1->times_used += g2->times_used; - - if (loop_dump_stream) - fprintf (loop_dump_stream, "giv at %d combined with giv at %d\n", - INSN_UID (g2->insn), INSN_UID (g1->insn)); - } -} - -/* EMIT code before INSERT_BEFORE to set REG = B * M + A. */ - -void -emit_iv_add_mult (b, m, a, reg, insert_before) - rtx b; /* initial value of basic induction variable */ - rtx m; /* multiplicative constant */ - rtx a; /* additive constant */ - rtx reg; /* destination register */ - rtx insert_before; -{ - rtx seq; - rtx result; - - /* Prevent unexpected sharing of these rtx. */ - a = copy_rtx (a); - b = copy_rtx (b); - - /* Increase the lifetime of any invariants moved further in code. */ - update_reg_last_use (a, insert_before); - update_reg_last_use (b, insert_before); - update_reg_last_use (m, insert_before); - - start_sequence (); - result = expand_mult_add (b, reg, m, a, GET_MODE (reg), 0); - if (reg != result) - emit_move_insn (reg, result); - seq = gen_sequence (); - end_sequence (); - - emit_insn_before (seq, insert_before); -} - -/* Test whether A * B can be computed without - an actual multiply insn. Value is 1 if so. */ - -static int -product_cheap_p (a, b) - rtx a; - rtx b; -{ - int i; - rtx tmp; - struct obstack *old_rtl_obstack = rtl_obstack; - char *storage = (char *) obstack_alloc (&temp_obstack, 0); - int win = 1; - - /* If only one is constant, make it B. */ - if (GET_CODE (a) == CONST_INT) - tmp = a, a = b, b = tmp; - - /* If first constant, both constant, so don't need multiply. */ - if (GET_CODE (a) == CONST_INT) - return 1; - - /* If second not constant, neither is constant, so would need multiply. */ - if (GET_CODE (b) != CONST_INT) - return 0; - - /* One operand is constant, so might not need multiply insn. Generate the - code for the multiply and see if a call or multiply, or long sequence - of insns is generated. */ - - rtl_obstack = &temp_obstack; - start_sequence (); - expand_mult (GET_MODE (a), a, b, NULL_RTX, 0); - tmp = gen_sequence (); - end_sequence (); - - if (GET_CODE (tmp) == SEQUENCE) - { - if (XVEC (tmp, 0) == 0) - win = 1; - else if (XVECLEN (tmp, 0) > 3) - win = 0; - else - for (i = 0; i < XVECLEN (tmp, 0); i++) - { - rtx insn = XVECEXP (tmp, 0, i); - - if (GET_CODE (insn) != INSN - || (GET_CODE (PATTERN (insn)) == SET - && GET_CODE (SET_SRC (PATTERN (insn))) == MULT) - || (GET_CODE (PATTERN (insn)) == PARALLEL - && GET_CODE (XVECEXP (PATTERN (insn), 0, 0)) == SET - && GET_CODE (SET_SRC (XVECEXP (PATTERN (insn), 0, 0))) == MULT)) - { - win = 0; - break; - } - } - } - else if (GET_CODE (tmp) == SET - && GET_CODE (SET_SRC (tmp)) == MULT) - win = 0; - else if (GET_CODE (tmp) == PARALLEL - && GET_CODE (XVECEXP (tmp, 0, 0)) == SET - && GET_CODE (SET_SRC (XVECEXP (tmp, 0, 0))) == MULT) - win = 0; - - /* Free any storage we obtained in generating this multiply and restore rtl - allocation to its normal obstack. */ - obstack_free (&temp_obstack, storage); - rtl_obstack = old_rtl_obstack; - - return win; -} - -/* Check to see if loop can be terminated by a "decrement and branch until - zero" instruction. If so, add a REG_NONNEG note to the branch insn if so. - Also try reversing an increment loop to a decrement loop - to see if the optimization can be performed. - Value is nonzero if optimization was performed. */ - -/* This is useful even if the architecture doesn't have such an insn, - because it might change a loops which increments from 0 to n to a loop - which decrements from n to 0. A loop that decrements to zero is usually - faster than one that increments from zero. */ - -/* ??? This could be rewritten to use some of the loop unrolling procedures, - such as approx_final_value, biv_total_increment, loop_iterations, and - final_[bg]iv_value. */ - -static int -check_dbra_loop (loop_end, insn_count, loop_start) - rtx loop_end; - int insn_count; - rtx loop_start; -{ - struct iv_class *bl; - rtx reg; - rtx jump_label; - rtx final_value; - rtx start_value; - enum rtx_code branch_code; - rtx new_add_val; - rtx comparison; - rtx before_comparison; - rtx p; - - /* If last insn is a conditional branch, and the insn before tests a - register value, try to optimize it. Otherwise, we can't do anything. */ - - comparison = get_condition_for_loop (PREV_INSN (loop_end)); - if (comparison == 0) - return 0; - - /* Check all of the bivs to see if the compare uses one of them. - Skip biv's set more than once because we can't guarantee that - it will be zero on the last iteration. Also skip if the biv is - used between its update and the test insn. */ - - for (bl = loop_iv_list; bl; bl = bl->next) - { - if (bl->biv_count == 1 - && bl->biv->dest_reg == XEXP (comparison, 0) - && ! reg_used_between_p (regno_reg_rtx[bl->regno], bl->biv->insn, - PREV_INSN (PREV_INSN (loop_end)))) - break; - } - - if (! bl) - return 0; - - /* Look for the case where the basic induction variable is always - nonnegative, and equals zero on the last iteration. - In this case, add a reg_note REG_NONNEG, which allows the - m68k DBRA instruction to be used. */ - - if (((GET_CODE (comparison) == GT - && GET_CODE (XEXP (comparison, 1)) == CONST_INT - && INTVAL (XEXP (comparison, 1)) == -1) - || (GET_CODE (comparison) == NE && XEXP (comparison, 1) == const0_rtx)) - && GET_CODE (bl->biv->add_val) == CONST_INT - && INTVAL (bl->biv->add_val) < 0) - { - /* Initial value must be greater than 0, - init_val % -dec_value == 0 to ensure that it equals zero on - the last iteration */ - - if (GET_CODE (bl->initial_value) == CONST_INT - && INTVAL (bl->initial_value) > 0 - && (INTVAL (bl->initial_value) % - (-INTVAL (bl->biv->add_val))) == 0) - { - /* register always nonnegative, add REG_NOTE to branch */ - REG_NOTES (PREV_INSN (loop_end)) - = gen_rtx (EXPR_LIST, REG_NONNEG, NULL_RTX, - REG_NOTES (PREV_INSN (loop_end))); - bl->nonneg = 1; - - return 1; - } - - /* If the decrement is 1 and the value was tested as >= 0 before - the loop, then we can safely optimize. */ - for (p = loop_start; p; p = PREV_INSN (p)) - { - if (GET_CODE (p) == CODE_LABEL) - break; - if (GET_CODE (p) != JUMP_INSN) - continue; - - before_comparison = get_condition_for_loop (p); - if (before_comparison - && XEXP (before_comparison, 0) == bl->biv->dest_reg - && GET_CODE (before_comparison) == LT - && XEXP (before_comparison, 1) == const0_rtx - && ! reg_set_between_p (bl->biv->dest_reg, p, loop_start) - && INTVAL (bl->biv->add_val) == -1) - { - REG_NOTES (PREV_INSN (loop_end)) - = gen_rtx (EXPR_LIST, REG_NONNEG, NULL_RTX, - REG_NOTES (PREV_INSN (loop_end))); - bl->nonneg = 1; - - return 1; - } - } - } - else if (num_mem_sets <= 1) - { - /* Try to change inc to dec, so can apply above optimization. */ - /* Can do this if: - all registers modified are induction variables or invariant, - all memory references have non-overlapping addresses - (obviously true if only one write) - allow 2 insns for the compare/jump at the end of the loop. */ - int num_nonfixed_reads = 0; - /* 1 if the iteration var is used only to count iterations. */ - int no_use_except_counting = 0; - - for (p = loop_start; p != loop_end; p = NEXT_INSN (p)) - if (GET_RTX_CLASS (GET_CODE (p)) == 'i') - num_nonfixed_reads += count_nonfixed_reads (PATTERN (p)); - - if (bl->giv_count == 0 - && ! loop_number_exit_labels[uid_loop_num[INSN_UID (loop_start)]]) - { - rtx bivreg = regno_reg_rtx[bl->regno]; - - /* If there are no givs for this biv, and the only exit is the - fall through at the end of the the loop, then - see if perhaps there are no uses except to count. */ - no_use_except_counting = 1; - for (p = loop_start; p != loop_end; p = NEXT_INSN (p)) - if (GET_RTX_CLASS (GET_CODE (p)) == 'i') - { - rtx set = single_set (p); - - if (set && GET_CODE (SET_DEST (set)) == REG - && REGNO (SET_DEST (set)) == bl->regno) - /* An insn that sets the biv is okay. */ - ; - else if (p == prev_nonnote_insn (prev_nonnote_insn (loop_end)) - || p == prev_nonnote_insn (loop_end)) - /* Don't bother about the end test. */ - ; - else if (reg_mentioned_p (bivreg, PATTERN (p))) - /* Any other use of the biv is no good. */ - { - no_use_except_counting = 0; - break; - } - } - } - - /* This code only acts for innermost loops. Also it simplifies - the memory address check by only reversing loops with - zero or one memory access. - Two memory accesses could involve parts of the same array, - and that can't be reversed. */ - - if (num_nonfixed_reads <= 1 - && !loop_has_call - && !loop_has_volatile - && (no_use_except_counting - || (bl->giv_count + bl->biv_count + num_mem_sets - + num_movables + 2 == insn_count))) - { - rtx condition = get_condition_for_loop (PREV_INSN (loop_end)); - int win; - rtx tem; - - /* Loop can be reversed. */ - if (loop_dump_stream) - fprintf (loop_dump_stream, "Can reverse loop\n"); - - /* Now check other conditions: - initial_value must be zero, - final_value % add_val == 0, so that when reversed, the - biv will be zero on the last iteration. - - This test can probably be improved since +/- 1 in the constant - can be obtained by changing LT to LE and vice versa; this is - confusing. */ - - if (comparison && bl->initial_value == const0_rtx - && GET_CODE (XEXP (comparison, 1)) == CONST_INT - /* LE gets turned into LT */ - && GET_CODE (comparison) == LT - && (INTVAL (XEXP (comparison, 1)) - % INTVAL (bl->biv->add_val)) == 0) - { - /* Register will always be nonnegative, with value - 0 on last iteration if loop reversed */ - - /* Save some info needed to produce the new insns. */ - reg = bl->biv->dest_reg; - jump_label = XEXP (SET_SRC (PATTERN (PREV_INSN (loop_end))), 1); - new_add_val = GEN_INT (- INTVAL (bl->biv->add_val)); - - final_value = XEXP (comparison, 1); - start_value = GEN_INT (INTVAL (XEXP (comparison, 1)) - - INTVAL (bl->biv->add_val)); - - /* Initialize biv to start_value before loop start. - The old initializing insn will be deleted as a - dead store by flow.c. */ - emit_insn_before (gen_move_insn (reg, start_value), loop_start); - - /* Add insn to decrement register, and delete insn - that incremented the register. */ - p = emit_insn_before (gen_add2_insn (reg, new_add_val), - bl->biv->insn); - delete_insn (bl->biv->insn); - - /* Update biv info to reflect its new status. */ - bl->biv->insn = p; - bl->initial_value = start_value; - bl->biv->add_val = new_add_val; - - /* Inc LABEL_NUSES so that delete_insn will - not delete the label. */ - LABEL_NUSES (XEXP (jump_label, 0)) ++; - - /* Emit an insn after the end of the loop to set the biv's - proper exit value if it is used anywhere outside the loop. */ - if ((regno_last_uid[bl->regno] - != INSN_UID (PREV_INSN (PREV_INSN (loop_end)))) - || ! bl->init_insn - || regno_first_uid[bl->regno] != INSN_UID (bl->init_insn)) - emit_insn_after (gen_move_insn (reg, final_value), - loop_end); - - /* Delete compare/branch at end of loop. */ - delete_insn (PREV_INSN (loop_end)); - delete_insn (PREV_INSN (loop_end)); - - /* Add new compare/branch insn at end of loop. */ - start_sequence (); - emit_cmp_insn (reg, const0_rtx, GE, NULL_RTX, - GET_MODE (reg), 0, 0); - emit_jump_insn (gen_bge (XEXP (jump_label, 0))); - tem = gen_sequence (); - end_sequence (); - emit_jump_insn_before (tem, loop_end); - - for (tem = PREV_INSN (loop_end); - tem && GET_CODE (tem) != JUMP_INSN; tem = PREV_INSN (tem)) - ; - if (tem) - { - JUMP_LABEL (tem) = XEXP (jump_label, 0); - - /* Increment of LABEL_NUSES done above. */ - /* Register is now always nonnegative, - so add REG_NONNEG note to the branch. */ - REG_NOTES (tem) = gen_rtx (EXPR_LIST, REG_NONNEG, NULL_RTX, - REG_NOTES (tem)); - } - - bl->nonneg = 1; - - /* Mark that this biv has been reversed. Each giv which depends - on this biv, and which is also live past the end of the loop - will have to be fixed up. */ - - bl->reversed = 1; - - if (loop_dump_stream) - fprintf (loop_dump_stream, - "Reversed loop and added reg_nonneg\n"); - - return 1; - } - } - } - - return 0; -} - -/* Verify whether the biv BL appears to be eliminable, - based on the insns in the loop that refer to it. - LOOP_START is the first insn of the loop, and END is the end insn. - - If ELIMINATE_P is non-zero, actually do the elimination. - - THRESHOLD and INSN_COUNT are from loop_optimize and are used to - determine whether invariant insns should be placed inside or at the - start of the loop. */ - -static int -maybe_eliminate_biv (bl, loop_start, end, eliminate_p, threshold, insn_count) - struct iv_class *bl; - rtx loop_start; - rtx end; - int eliminate_p; - int threshold, insn_count; -{ - rtx reg = bl->biv->dest_reg; - rtx p, set; - struct induction *v; - - /* Scan all insns in the loop, stopping if we find one that uses the - biv in a way that we cannot eliminate. */ - - for (p = loop_start; p != end; p = NEXT_INSN (p)) - { - enum rtx_code code = GET_CODE (p); - rtx where = threshold >= insn_count ? loop_start : p; - - if ((code == INSN || code == JUMP_INSN || code == CALL_INSN) - && reg_mentioned_p (reg, PATTERN (p)) - && ! maybe_eliminate_biv_1 (PATTERN (p), p, bl, eliminate_p, where)) - { - if (loop_dump_stream) - fprintf (loop_dump_stream, - "Cannot eliminate biv %d: biv used in insn %d.\n", - bl->regno, INSN_UID (p)); - break; - } - } - - if (p == end) - { - if (loop_dump_stream) - fprintf (loop_dump_stream, "biv %d %s eliminated.\n", - bl->regno, eliminate_p ? "was" : "can be"); - return 1; - } - - return 0; -} - -/* If BL appears in X (part of the pattern of INSN), see if we can - eliminate its use. If so, return 1. If not, return 0. - - If BIV does not appear in X, return 1. - - If ELIMINATE_P is non-zero, actually do the elimination. WHERE indicates - where extra insns should be added. Depending on how many items have been - moved out of the loop, it will either be before INSN or at the start of - the loop. */ - -static int -maybe_eliminate_biv_1 (x, insn, bl, eliminate_p, where) - rtx x, insn; - struct iv_class *bl; - int eliminate_p; - rtx where; -{ - enum rtx_code code = GET_CODE (x); - rtx reg = bl->biv->dest_reg; - enum machine_mode mode = GET_MODE (reg); - struct induction *v; - rtx arg, new, tem; - int arg_operand; - char *fmt; - int i, j; - - switch (code) - { - case REG: - /* If we haven't already been able to do something with this BIV, - we can't eliminate it. */ - if (x == reg) - return 0; - return 1; - - case SET: - /* If this sets the BIV, it is not a problem. */ - if (SET_DEST (x) == reg) - return 1; - - /* If this is an insn that defines a giv, it is also ok because - it will go away when the giv is reduced. */ - for (v = bl->giv; v; v = v->next_iv) - if (v->giv_type == DEST_REG && SET_DEST (x) == v->dest_reg) - return 1; - -#ifdef HAVE_cc0 - if (SET_DEST (x) == cc0_rtx && SET_SRC (x) == reg) - { - /* Can replace with any giv that was reduced and - that has (MULT_VAL != 0) and (ADD_VAL == 0). - Require a constant for MULT_VAL, so we know it's nonzero. */ - - for (v = bl->giv; v; v = v->next_iv) - if (CONSTANT_P (v->mult_val) && v->mult_val != const0_rtx - && v->add_val == const0_rtx - && ! v->ignore && ! v->maybe_dead - && v->mode == mode) - { - if (! eliminate_p) - return 1; - - /* If the giv has the opposite direction of change, - then reverse the comparison. */ - if (INTVAL (v->mult_val) < 0) - new = gen_rtx (COMPARE, GET_MODE (v->new_reg), - const0_rtx, v->new_reg); - else - new = v->new_reg; - - /* We can probably test that giv's reduced reg. */ - if (validate_change (insn, &SET_SRC (x), new, 0)) - return 1; - } - - /* Look for a giv with (MULT_VAL != 0) and (ADD_VAL != 0); - replace test insn with a compare insn (cmp REDUCED_GIV ADD_VAL). - Require a constant for MULT_VAL, so we know it's nonzero. */ - - for (v = bl->giv; v; v = v->next_iv) - if (CONSTANT_P (v->mult_val) && v->mult_val != const0_rtx - && ! v->ignore && ! v->maybe_dead - && v->mode == mode) - { - if (! eliminate_p) - return 1; - - /* If the giv has the opposite direction of change, - then reverse the comparison. */ - if (INTVAL (v->mult_val) < 0) - new = gen_rtx (COMPARE, VOIDmode, copy_rtx (v->add_val), - v->new_reg); - else - new = gen_rtx (COMPARE, VOIDmode, v->new_reg, - copy_rtx (v->add_val)); - - /* Replace biv with the giv's reduced register. */ - update_reg_last_use (v->add_val, insn); - if (validate_change (insn, &SET_SRC (PATTERN (insn)), new, 0)) - return 1; - - /* Insn doesn't support that constant or invariant. Copy it - into a register (it will be a loop invariant.) */ - tem = gen_reg_rtx (GET_MODE (v->new_reg)); - - emit_insn_before (gen_move_insn (tem, copy_rtx (v->add_val)), - where); - - if (validate_change (insn, &SET_SRC (PATTERN (insn)), - gen_rtx (COMPARE, VOIDmode, - v->new_reg, tem), 0)) - return 1; - } - } -#endif - break; - - case COMPARE: - case EQ: case NE: - case GT: case GE: case GTU: case GEU: - case LT: case LE: case LTU: case LEU: - /* See if either argument is the biv. */ - if (XEXP (x, 0) == reg) - arg = XEXP (x, 1), arg_operand = 1; - else if (XEXP (x, 1) == reg) - arg = XEXP (x, 0), arg_operand = 0; - else - break; - - if (CONSTANT_P (arg)) - { - /* First try to replace with any giv that has constant positive - mult_val and constant add_val. We might be able to support - negative mult_val, but it seems complex to do it in general. */ - - for (v = bl->giv; v; v = v->next_iv) - if (CONSTANT_P (v->mult_val) && INTVAL (v->mult_val) > 0 - && CONSTANT_P (v->add_val) - && ! v->ignore && ! v->maybe_dead - && v->mode == mode) - { - if (! eliminate_p) - return 1; - - /* Replace biv with the giv's reduced reg. */ - XEXP (x, 1-arg_operand) = v->new_reg; - - /* If all constants are actually constant integers and - the derived constant can be directly placed in the COMPARE, - do so. */ - if (GET_CODE (arg) == CONST_INT - && GET_CODE (v->mult_val) == CONST_INT - && GET_CODE (v->add_val) == CONST_INT - && validate_change (insn, &XEXP (x, arg_operand), - GEN_INT (INTVAL (arg) - * INTVAL (v->mult_val) - + INTVAL (v->add_val)), 0)) - return 1; - - /* Otherwise, load it into a register. */ - tem = gen_reg_rtx (mode); - emit_iv_add_mult (arg, v->mult_val, v->add_val, tem, where); - if (validate_change (insn, &XEXP (x, arg_operand), tem, 0)) - return 1; - - /* If that failed, put back the change we made above. */ - XEXP (x, 1-arg_operand) = reg; - } - - /* Look for giv with positive constant mult_val and nonconst add_val. - Insert insns to calculate new compare value. */ - - for (v = bl->giv; v; v = v->next_iv) - if (CONSTANT_P (v->mult_val) && INTVAL (v->mult_val) > 0 - && ! v->ignore && ! v->maybe_dead - && v->mode == mode) - { - rtx tem; - - if (! eliminate_p) - return 1; - - tem = gen_reg_rtx (mode); - - /* Replace biv with giv's reduced register. */ - validate_change (insn, &XEXP (x, 1 - arg_operand), - v->new_reg, 1); - - /* Compute value to compare against. */ - emit_iv_add_mult (arg, v->mult_val, v->add_val, tem, where); - /* Use it in this insn. */ - validate_change (insn, &XEXP (x, arg_operand), tem, 1); - if (apply_change_group ()) - return 1; - } - } - else if (GET_CODE (arg) == REG || GET_CODE (arg) == MEM) - { - if (invariant_p (arg) == 1) - { - /* Look for giv with constant positive mult_val and nonconst - add_val. Insert insns to compute new compare value. */ - - for (v = bl->giv; v; v = v->next_iv) - if (CONSTANT_P (v->mult_val) && INTVAL (v->mult_val) > 0 - && ! v->ignore && ! v->maybe_dead - && v->mode == mode) - { - rtx tem; - - if (! eliminate_p) - return 1; - - tem = gen_reg_rtx (mode); - - /* Replace biv with giv's reduced register. */ - validate_change (insn, &XEXP (x, 1 - arg_operand), - v->new_reg, 1); - - /* Compute value to compare against. */ - emit_iv_add_mult (arg, v->mult_val, v->add_val, - tem, where); - validate_change (insn, &XEXP (x, arg_operand), tem, 1); - if (apply_change_group ()) - return 1; - } - } - - /* This code has problems. Basically, you can't know when - seeing if we will eliminate BL, whether a particular giv - of ARG will be reduced. If it isn't going to be reduced, - we can't eliminate BL. We can try forcing it to be reduced, - but that can generate poor code. - - The problem is that the benefit of reducing TV, below should - be increased if BL can actually be eliminated, but this means - we might have to do a topological sort of the order in which - we try to process biv. It doesn't seem worthwhile to do - this sort of thing now. */ - -#if 0 - /* Otherwise the reg compared with had better be a biv. */ - if (GET_CODE (arg) != REG - || reg_iv_type[REGNO (arg)] != BASIC_INDUCT) - return 0; - - /* Look for a pair of givs, one for each biv, - with identical coefficients. */ - for (v = bl->giv; v; v = v->next_iv) - { - struct induction *tv; - - if (v->ignore || v->maybe_dead || v->mode != mode) - continue; - - for (tv = reg_biv_class[REGNO (arg)]->giv; tv; tv = tv->next_iv) - if (! tv->ignore && ! tv->maybe_dead - && rtx_equal_p (tv->mult_val, v->mult_val) - && rtx_equal_p (tv->add_val, v->add_val) - && tv->mode == mode) - { - if (! eliminate_p) - return 1; - - /* Replace biv with its giv's reduced reg. */ - XEXP (x, 1-arg_operand) = v->new_reg; - /* Replace other operand with the other giv's - reduced reg. */ - XEXP (x, arg_operand) = tv->new_reg; - return 1; - } - } -#endif - } - - /* If we get here, the biv can't be eliminated. */ - return 0; - - case MEM: - /* If this address is a DEST_ADDR giv, it doesn't matter if the - biv is used in it, since it will be replaced. */ - for (v = bl->giv; v; v = v->next_iv) - if (v->giv_type == DEST_ADDR && v->location == &XEXP (x, 0)) - return 1; - break; - } - - /* See if any subexpression fails elimination. */ - fmt = GET_RTX_FORMAT (code); - for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--) - { - switch (fmt[i]) - { - case 'e': - if (! maybe_eliminate_biv_1 (XEXP (x, i), insn, bl, - eliminate_p, where)) - return 0; - break; - - case 'E': - for (j = XVECLEN (x, i) - 1; j >= 0; j--) - if (! maybe_eliminate_biv_1 (XVECEXP (x, i, j), insn, bl, - eliminate_p, where)) - return 0; - break; - } - } - - return 1; -} - -/* Return nonzero if the last use of REG - is in an insn following INSN in the same basic block. */ - -static int -last_use_this_basic_block (reg, insn) - rtx reg; - rtx insn; -{ - rtx n; - for (n = insn; - n && GET_CODE (n) != CODE_LABEL && GET_CODE (n) != JUMP_INSN; - n = NEXT_INSN (n)) - { - if (regno_last_uid[REGNO (reg)] == INSN_UID (n)) - return 1; - } - return 0; -} - -/* Called via `note_stores' to record the initial value of a biv. Here we - just record the location of the set and process it later. */ - -static void -record_initial (dest, set) - rtx dest; - rtx set; -{ - struct iv_class *bl; - - if (GET_CODE (dest) != REG - || REGNO (dest) >= max_reg_before_loop - || reg_iv_type[REGNO (dest)] != BASIC_INDUCT - /* Reject this insn if the source isn't valid for the mode of DEST. */ - || GET_MODE (dest) != GET_MODE (SET_DEST (set))) - return; - - bl = reg_biv_class[REGNO (dest)]; - - /* If this is the first set found, record it. */ - if (bl->init_insn == 0) - { - bl->init_insn = note_insn; - bl->init_set = set; - } -} - -/* If any of the registers in X are "old" and currently have a last use earlier - than INSN, update them to have a last use of INSN. Their actual last use - will be the previous insn but it will not have a valid uid_luid so we can't - use it. */ - -static void -update_reg_last_use (x, insn) - rtx x; - rtx insn; -{ - /* Check for the case where INSN does not have a valid luid. In this case, - there is no need to modify the regno_last_uid, as this can only happen - when code is inserted after the loop_end to set a pseudo's final value, - and hence this insn will never be the last use of x. */ - if (GET_CODE (x) == REG && REGNO (x) < max_reg_before_loop - && INSN_UID (insn) < max_uid_for_loop - && uid_luid[regno_last_uid[REGNO (x)]] < uid_luid[INSN_UID (insn)]) - regno_last_uid[REGNO (x)] = INSN_UID (insn); - else - { - register int i, j; - register char *fmt = GET_RTX_FORMAT (GET_CODE (x)); - for (i = GET_RTX_LENGTH (GET_CODE (x)) - 1; i >= 0; i--) - { - if (fmt[i] == 'e') - update_reg_last_use (XEXP (x, i), insn); - else if (fmt[i] == 'E') - for (j = XVECLEN (x, i) - 1; j >= 0; j--) - update_reg_last_use (XVECEXP (x, i, j), insn); - } - } -} - -/* Given a jump insn JUMP, return the condition that will cause it to branch - to its JUMP_LABEL. If the condition cannot be understood, or is an - inequality floating-point comparison which needs to be reversed, 0 will - be returned. - - If EARLIEST is non-zero, it is a pointer to a place where the earliest - insn used in locating the condition was found. If a replacement test - of the condition is desired, it should be placed in front of that - insn and we will be sure that the inputs are still valid. - - The condition will be returned in a canonical form to simplify testing by - callers. Specifically: - - (1) The code will always be a comparison operation (EQ, NE, GT, etc.). - (2) Both operands will be machine operands; (cc0) will have been replaced. - (3) If an operand is a constant, it will be the second operand. - (4) (LE x const) will be replaced with (LT x <const+1>) and similarly - for GE, GEU, and LEU. */ - -rtx -get_condition (jump, earliest) - rtx jump; - rtx *earliest; -{ - enum rtx_code code; - rtx prev = jump; - rtx set; - rtx tem; - rtx op0, op1; - int reverse_code = 0; - int did_reverse_condition = 0; - - /* If this is not a standard conditional jump, we can't parse it. */ - if (GET_CODE (jump) != JUMP_INSN - || ! condjump_p (jump) || simplejump_p (jump)) - return 0; - - code = GET_CODE (XEXP (SET_SRC (PATTERN (jump)), 0)); - op0 = XEXP (XEXP (SET_SRC (PATTERN (jump)), 0), 0); - op1 = XEXP (XEXP (SET_SRC (PATTERN (jump)), 0), 1); - - if (earliest) - *earliest = jump; - - /* If this branches to JUMP_LABEL when the condition is false, reverse - the condition. */ - if (GET_CODE (XEXP (SET_SRC (PATTERN (jump)), 2)) == LABEL_REF - && XEXP (XEXP (SET_SRC (PATTERN (jump)), 2), 0) == JUMP_LABEL (jump)) - code = reverse_condition (code), did_reverse_condition ^= 1; - - /* If we are comparing a register with zero, see if the register is set - in the previous insn to a COMPARE or a comparison operation. Perform - the same tests as a function of STORE_FLAG_VALUE as find_comparison_args - in cse.c */ - - while (GET_RTX_CLASS (code) == '<' && op1 == const0_rtx) - { - /* Set non-zero when we find something of interest. */ - rtx x = 0; - -#ifdef HAVE_cc0 - /* If comparison with cc0, import actual comparison from compare - insn. */ - if (op0 == cc0_rtx) - { - if ((prev = prev_nonnote_insn (prev)) == 0 - || GET_CODE (prev) != INSN - || (set = single_set (prev)) == 0 - || SET_DEST (set) != cc0_rtx) - return 0; - - op0 = SET_SRC (set); - op1 = CONST0_RTX (GET_MODE (op0)); - if (earliest) - *earliest = prev; - } -#endif - - /* If this is a COMPARE, pick up the two things being compared. */ - if (GET_CODE (op0) == COMPARE) - { - op1 = XEXP (op0, 1); - op0 = XEXP (op0, 0); - continue; - } - else if (GET_CODE (op0) != REG) - break; - - /* Go back to the previous insn. Stop if it is not an INSN. We also - stop if it isn't a single set or if it has a REG_INC note because - we don't want to bother dealing with it. */ - - if ((prev = prev_nonnote_insn (prev)) == 0 - || GET_CODE (prev) != INSN - || FIND_REG_INC_NOTE (prev, 0) - || (set = single_set (prev)) == 0) - break; - - /* If this is setting OP0, get what it sets it to if it looks - relevant. */ - if (SET_DEST (set) == op0) - { - enum machine_mode inner_mode = GET_MODE (SET_SRC (set)); - - if ((GET_CODE (SET_SRC (set)) == COMPARE - || (((code == NE - || (code == LT - && GET_MODE_CLASS (inner_mode) == MODE_INT - && (GET_MODE_BITSIZE (inner_mode) - <= HOST_BITS_PER_WIDE_INT) - && (STORE_FLAG_VALUE - & ((HOST_WIDE_INT) 1 - << (GET_MODE_BITSIZE (inner_mode) - 1)))) -#ifdef FLOAT_STORE_FLAG_VALUE - || (code == LT - && GET_MODE_CLASS (inner_mode) == MODE_FLOAT - && FLOAT_STORE_FLAG_VALUE < 0) -#endif - )) - && GET_RTX_CLASS (GET_CODE (SET_SRC (set))) == '<'))) - x = SET_SRC (set); - else if (((code == EQ - || (code == GE - && (GET_MODE_BITSIZE (inner_mode) - <= HOST_BITS_PER_WIDE_INT) - && GET_MODE_CLASS (inner_mode) == MODE_INT - && (STORE_FLAG_VALUE - & ((HOST_WIDE_INT) 1 - << (GET_MODE_BITSIZE (inner_mode) - 1)))) -#ifdef FLOAT_STORE_FLAG_VALUE - || (code == GE - && GET_MODE_CLASS (inner_mode) == MODE_FLOAT - && FLOAT_STORE_FLAG_VALUE < 0) -#endif - )) - && GET_RTX_CLASS (GET_CODE (SET_SRC (set))) == '<') - { - /* We might have reversed a LT to get a GE here. But this wasn't - actually the comparison of data, so we don't flag that we - have had to reverse the condition. */ - did_reverse_condition ^= 1; - reverse_code = 1; - x = SET_SRC (set); - } - } - - else if (reg_set_p (op0, prev)) - /* If this sets OP0, but not directly, we have to give up. */ - break; - - if (x) - { - if (GET_RTX_CLASS (GET_CODE (x)) == '<') - code = GET_CODE (x); - if (reverse_code) - { - code = reverse_condition (code); - did_reverse_condition ^= 1; - reverse_code = 0; - } - - op0 = XEXP (x, 0), op1 = XEXP (x, 1); - if (earliest) - *earliest = prev; - } - } - - /* If constant is first, put it last. */ - if (CONSTANT_P (op0)) - code = swap_condition (code), tem = op0, op0 = op1, op1 = tem; - - /* If OP0 is the result of a comparison, we weren't able to find what - was really being compared, so fail. */ - if (GET_MODE_CLASS (GET_MODE (op0)) == MODE_CC) - return 0; - - /* Canonicalize any ordered comparison with integers involving equality - if we can do computations in the relevant mode and we do not - overflow. */ - - if (GET_CODE (op1) == CONST_INT - && GET_MODE (op0) != VOIDmode - && GET_MODE_BITSIZE (GET_MODE (op0)) <= HOST_BITS_PER_WIDE_INT) - { - HOST_WIDE_INT const_val = INTVAL (op1); - unsigned HOST_WIDE_INT uconst_val = const_val; - unsigned HOST_WIDE_INT max_val - = (unsigned HOST_WIDE_INT) GET_MODE_MASK (GET_MODE (op0)); - - switch (code) - { - case LE: - if (const_val != max_val >> 1) - code = LT, op1 = GEN_INT (const_val + 1); - break; - - case GE: - if (const_val - != (((HOST_WIDE_INT) 1 - << (GET_MODE_BITSIZE (GET_MODE (op0)) - 1)))) - code = GT, op1 = GEN_INT (const_val - 1); - break; - - case LEU: - if (uconst_val != max_val) - code = LTU, op1 = GEN_INT (uconst_val + 1); - break; - - case GEU: - if (uconst_val != 0) - code = GTU, op1 = GEN_INT (uconst_val - 1); - break; - } - } - - /* If this was floating-point and we reversed anything other than an - EQ or NE, return zero. */ - if (TARGET_FLOAT_FORMAT == IEEE_FLOAT_FORMAT - && did_reverse_condition && code != NE && code != EQ - && GET_MODE_CLASS (GET_MODE (op0)) == MODE_FLOAT) - return 0; - -#ifdef HAVE_cc0 - /* Never return CC0; return zero instead. */ - if (op0 == cc0_rtx) - return 0; -#endif - - return gen_rtx (code, VOIDmode, op0, op1); -} - -/* Similar to above routine, except that we also put an invariant last - unless both operands are invariants. */ - -rtx -get_condition_for_loop (x) - rtx x; -{ - rtx comparison = get_condition (x, NULL_PTR); - - if (comparison == 0 - || ! invariant_p (XEXP (comparison, 0)) - || invariant_p (XEXP (comparison, 1))) - return comparison; - - return gen_rtx (swap_condition (GET_CODE (comparison)), VOIDmode, - XEXP (comparison, 1), XEXP (comparison, 0)); -} |