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Diffstat (limited to 'sys/gnu/fpemul/reg_u_sub.s')
| -rw-r--r-- | sys/gnu/fpemul/reg_u_sub.s | 361 |
1 files changed, 361 insertions, 0 deletions
diff --git a/sys/gnu/fpemul/reg_u_sub.s b/sys/gnu/fpemul/reg_u_sub.s new file mode 100644 index 0000000000000..7d6d8961669e7 --- /dev/null +++ b/sys/gnu/fpemul/reg_u_sub.s @@ -0,0 +1,361 @@ + .file "reg_u_sub.S" +/* + * reg_u_sub.S + * + * Core floating point subtraction routine. + * + * Call from C as: + * void reg_u_sub(FPU_REG *arg1, FPU_REG *arg2, FPU_REG *answ, + * int control_w) + * + * + * Copyright (C) 1992,1993,1994 + * W. Metzenthen, 22 Parker St, Ormond, Vic 3163, + * Australia. E-mail billm@vaxc.cc.monash.edu.au + * All rights reserved. + * + * This copyright notice covers the redistribution and use of the + * FPU emulator developed by W. Metzenthen. It covers only its use + * in the 386BSD, FreeBSD and NetBSD operating systems. Any other + * use is not permitted under this copyright. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must include information specifying + * that source code for the emulator is freely available and include + * either: + * a) an offer to provide the source code for a nominal distribution + * fee, or + * b) list at least two alternative methods whereby the source + * can be obtained, e.g. a publically accessible bulletin board + * and an anonymous ftp site from which the software can be + * downloaded. + * 3. All advertising materials specifically mentioning features or use of + * this emulator must acknowledge that it was developed by W. Metzenthen. + * 4. The name of W. Metzenthen may not be used to endorse or promote + * products derived from this software without specific prior written + * permission. + * + * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, + * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY + * AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL + * W. METZENTHEN BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, + * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, + * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR + * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF + * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING + * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS + * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + * + * + * The purpose of this copyright, based upon the Berkeley copyright, is to + * ensure that the covered software remains freely available to everyone. + * + * The software (with necessary differences) is also available, but under + * the terms of the GNU copyleft, for the Linux operating system and for + * the djgpp ms-dos extender. + * + * W. Metzenthen June 1994. + * + * + * $Id: reg_u_sub.s,v 1.3 1994/06/10 07:44:59 rich Exp $ + * + */ + +/* + | Kernel subtraction routine reg_u_sub(reg *arg1, reg *arg2, reg *answ). + | Takes two valid reg f.p. numbers (TW_Valid), which are + | treated as unsigned numbers, + | and returns their difference as a TW_Valid or TW_Zero f.p. + | number. + | The first number (arg1) must be the larger. + | The returned number is normalized. + | Basic checks are performed if PARANOID is defined. + */ + +#include "exception.h" +#include "fpu_asm.h" +#include "control_w.h" + +.text + .align 2,144 +.globl _reg_u_sub +_reg_u_sub: + pushl %ebp + movl %esp,%ebp + pushl %esi + pushl %edi + pushl %ebx + + movl PARAM1,%esi /* source 1 */ + movl PARAM2,%edi /* source 2 */ + +#ifdef DENORM_OPERAND + cmpl EXP_UNDER,EXP(%esi) + jg xOp1_not_denorm + + call _denormal_operand + orl %eax,%eax + jnz FPU_Arith_exit + +xOp1_not_denorm: + cmpl EXP_UNDER,EXP(%edi) + jg xOp2_not_denorm + + call _denormal_operand + orl %eax,%eax + jnz FPU_Arith_exit + +xOp2_not_denorm: +#endif DENORM_OPERAND + +/* xorl %ecx,%ecx */ + movl EXP(%esi),%ecx + subl EXP(%edi),%ecx /* exp1 - exp2 */ + +#ifdef PARANOID + /* source 2 is always smaller than source 1 */ +/* jc L_bugged */ + js L_bugged_1 + + testl $0x80000000,SIGH(%edi) /* The args are assumed to be be normalized */ + je L_bugged_2 + + testl $0x80000000,SIGH(%esi) + je L_bugged_2 +#endif PARANOID + +/*--------------------------------------+ + | Form a register holding the | + | smaller number | + +--------------------------------------*/ + movl SIGH(%edi),%eax /* register ms word */ + movl SIGL(%edi),%ebx /* register ls word */ + + movl PARAM3,%edi /* destination */ + movl EXP(%esi),%edx + movl %edx,EXP(%edi) /* Copy exponent to destination */ + movb SIGN(%esi),%dl + movb %dl,SIGN(%edi) /* Copy the sign from the first arg */ + + xorl %edx,%edx /* register extension */ + +/*--------------------------------------+ + | Shift the temporary register | + | right the required number of | + | places. | + +--------------------------------------*/ +L_shift_r: + cmpl $32,%ecx /* shrd only works for 0..31 bits */ + jnc L_more_than_31 + +/* less than 32 bits */ + shrd %cl,%ebx,%edx + shrd %cl,%eax,%ebx + shr %cl,%eax + jmp L_shift_done + +L_more_than_31: + cmpl $64,%ecx + jnc L_more_than_63 + + subb $32,%cl + jz L_exactly_32 + + shrd %cl,%eax,%edx + shr %cl,%eax + orl %ebx,%ebx + jz L_more_31_no_low /* none of the lowest bits is set */ + + orl $1,%edx /* record the fact in the extension */ + +L_more_31_no_low: + movl %eax,%ebx + xorl %eax,%eax + jmp L_shift_done + +L_exactly_32: + movl %ebx,%edx + movl %eax,%ebx + xorl %eax,%eax + jmp L_shift_done + +L_more_than_63: + cmpw $65,%cx + jnc L_more_than_64 + + /* Shift right by 64 bits */ + movl %eax,%edx + orl %ebx,%ebx + jz L_more_63_no_low + + orl $1,%edx + jmp L_more_63_no_low + +L_more_than_64: + jne L_more_than_65 + + /* Shift right by 65 bits */ + /* Carry is clear if we get here */ + movl %eax,%edx + rcrl %edx + jnc L_shift_65_nc + + orl $1,%edx + jmp L_more_63_no_low + +L_shift_65_nc: + orl %ebx,%ebx + jz L_more_63_no_low + + orl $1,%edx + jmp L_more_63_no_low + +L_more_than_65: + movl $1,%edx /* The shifted nr always at least one '1' */ + +L_more_63_no_low: + xorl %ebx,%ebx + xorl %eax,%eax + +L_shift_done: +L_subtr: +/*------------------------------+ + | Do the subtraction | + +------------------------------*/ + xorl %ecx,%ecx + subl %edx,%ecx + movl %ecx,%edx + movl SIGL(%esi),%ecx + sbbl %ebx,%ecx + movl %ecx,%ebx + movl SIGH(%esi),%ecx + sbbl %eax,%ecx + movl %ecx,%eax + +#ifdef PARANOID + /* We can never get a borrow */ + jc L_bugged +#endif PARANOID + +/*--------------------------------------+ + | Normalize the result | + +--------------------------------------*/ + testl $0x80000000,%eax + jnz L_round /* no shifting needed */ + + orl %eax,%eax + jnz L_shift_1 /* shift left 1 - 31 bits */ + + orl %ebx,%ebx + jnz L_shift_32 /* shift left 32 - 63 bits */ + +/* A rare case, the only one which is non-zero if we got here +// is: 1000000 .... 0000 +// -0111111 .... 1111 1 +// -------------------- +// 0000000 .... 0000 1 */ + + cmpl $0x80000000,%edx + jnz L_must_be_zero + + /* Shift left 64 bits */ + subl $64,EXP(%edi) + movl %edx,%eax + jmp L_store + +L_must_be_zero: +#ifdef PARANOID + orl %edx,%edx + jnz L_bugged_3 +#endif PARANOID + + /* The result is zero */ + movb TW_Zero,TAG(%edi) + movl $0,EXP(%edi) /* exponent */ + movl $0,SIGL(%edi) + movl $0,SIGH(%edi) + jmp L_exit /* Does not underflow */ + +L_shift_32: + movl %ebx,%eax + movl %edx,%ebx + movl $0,%edx + subl $32,EXP(%edi) /* Can get underflow here */ + +/* We need to shift left by 1 - 31 bits */ +L_shift_1: + bsrl %eax,%ecx /* get the required shift in %ecx */ + subl $31,%ecx + negl %ecx + shld %cl,%ebx,%eax + shld %cl,%edx,%ebx + shl %cl,%edx + subl %ecx,EXP(%edi) /* Can get underflow here */ + +L_round: + jmp FPU_round /* Round the result */ + + +#ifdef PARANOID +L_bugged_1: + pushl EX_INTERNAL|0x206 + call EXCEPTION + pop %ebx + jmp L_exit + +L_bugged_2: + pushl EX_INTERNAL|0x209 + call EXCEPTION + pop %ebx + jmp L_exit + +L_bugged_3: + pushl EX_INTERNAL|0x210 + call EXCEPTION + pop %ebx + jmp L_exit + +L_bugged_4: + pushl EX_INTERNAL|0x211 + call EXCEPTION + pop %ebx + jmp L_exit + +L_bugged: + pushl EX_INTERNAL|0x212 + call EXCEPTION + pop %ebx + jmp L_exit +#endif PARANOID + + +L_store: +/*------------------------------+ + | Store the result | + +------------------------------*/ + movl %eax,SIGH(%edi) + movl %ebx,SIGL(%edi) + + movb TW_Valid,TAG(%edi) /* Set the tags to TW_Valid */ + + cmpl EXP_UNDER,EXP(%edi) + jle L_underflow + +L_exit: + popl %ebx + popl %edi + popl %esi + leave + ret + + +L_underflow: + push %edi + call _arith_underflow + pop %ebx + jmp L_exit + |