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diff --git a/contrib/binutils/gas/doc/c-i386.texi b/contrib/binutils/gas/doc/c-i386.texi deleted file mode 100644 index bb51be3997e6..000000000000 --- a/contrib/binutils/gas/doc/c-i386.texi +++ /dev/null @@ -1,456 +0,0 @@ -@c Copyright (C) 1991, 92, 93, 94, 95, 1997 Free Software Foundation, Inc. -@c This is part of the GAS manual. -@c For copying conditions, see the file as.texinfo. -@ifset GENERIC -@page -@node i386-Dependent -@chapter 80386 Dependent Features -@end ifset -@ifclear GENERIC -@node Machine Dependencies -@chapter 80386 Dependent Features -@end ifclear - -@cindex i386 support -@cindex i80306 support -@menu -* i386-Options:: Options -* i386-Syntax:: AT&T Syntax versus Intel Syntax -* i386-Opcodes:: Opcode Naming -* i386-Regs:: Register Naming -* i386-prefixes:: Opcode Prefixes -* i386-Memory:: Memory References -* i386-jumps:: Handling of Jump Instructions -* i386-Float:: Floating Point -* i386-16bit:: Writing 16-bit Code -* i386-Notes:: Notes -@end menu - -@node i386-Options -@section Options - -@cindex options for i386 (none) -@cindex i386 options (none) -The 80386 has no machine dependent options. - -@node i386-Syntax -@section AT&T Syntax versus Intel Syntax - -@cindex i386 syntax compatibility -@cindex syntax compatibility, i386 -In order to maintain compatibility with the output of @code{@value{GCC}}, -@code{@value{AS}} supports AT&T System V/386 assembler syntax. This is quite -different from Intel syntax. We mention these differences because -almost all 80386 documents used only Intel syntax. Notable differences -between the two syntaxes are: - -@cindex immediate operands, i386 -@cindex i386 immediate operands -@cindex register operands, i386 -@cindex i386 register operands -@cindex jump/call operands, i386 -@cindex i386 jump/call operands -@cindex operand delimiters, i386 -@itemize @bullet -@item -AT&T immediate operands are preceded by @samp{$}; Intel immediate -operands are undelimited (Intel @samp{push 4} is AT&T @samp{pushl $4}). -AT&T register operands are preceded by @samp{%}; Intel register operands -are undelimited. AT&T absolute (as opposed to PC relative) jump/call -operands are prefixed by @samp{*}; they are undelimited in Intel syntax. - -@cindex i386 source, destination operands -@cindex source, destination operands; i386 -@item -AT&T and Intel syntax use the opposite order for source and destination -operands. Intel @samp{add eax, 4} is @samp{addl $4, %eax}. The -@samp{source, dest} convention is maintained for compatibility with -previous Unix assemblers. - -@cindex opcode suffixes, i386 -@cindex sizes operands, i386 -@cindex i386 size suffixes -@item -In AT&T syntax the size of memory operands is determined from the last -character of the opcode name. Opcode suffixes of @samp{b}, @samp{w}, -and @samp{l} specify byte (8-bit), word (16-bit), and long (32-bit) -memory references. Intel syntax accomplishes this by prefixes memory -operands (@emph{not} the opcodes themselves) with @samp{byte ptr}, -@samp{word ptr}, and @samp{dword ptr}. Thus, Intel @samp{mov al, byte -ptr @var{foo}} is @samp{movb @var{foo}, %al} in AT&T syntax. - -@cindex return instructions, i386 -@cindex i386 jump, call, return -@item -Immediate form long jumps and calls are -@samp{lcall/ljmp $@var{section}, $@var{offset}} in AT&T syntax; the -Intel syntax is -@samp{call/jmp far @var{section}:@var{offset}}. Also, the far return -instruction -is @samp{lret $@var{stack-adjust}} in AT&T syntax; Intel syntax is -@samp{ret far @var{stack-adjust}}. - -@cindex sections, i386 -@cindex i386 sections -@item -The AT&T assembler does not provide support for multiple section -programs. Unix style systems expect all programs to be single sections. -@end itemize - -@node i386-Opcodes -@section Opcode Naming - -@cindex i386 opcode naming -@cindex opcode naming, i386 -Opcode names are suffixed with one character modifiers which specify the -size of operands. The letters @samp{b}, @samp{w}, and @samp{l} specify -byte, word, and long operands. If no suffix is specified by an -instruction and it contains no memory operands then @code{@value{AS}} tries to -fill in the missing suffix based on the destination register operand -(the last one by convention). Thus, @samp{mov %ax, %bx} is equivalent -to @samp{movw %ax, %bx}; also, @samp{mov $1, %bx} is equivalent to -@samp{movw $1, %bx}. Note that this is incompatible with the AT&T Unix -assembler which assumes that a missing opcode suffix implies long -operand size. (This incompatibility does not affect compiler output -since compilers always explicitly specify the opcode suffix.) - -Almost all opcodes have the same names in AT&T and Intel format. There -are a few exceptions. The sign extend and zero extend instructions need -two sizes to specify them. They need a size to sign/zero extend -@emph{from} and a size to zero extend @emph{to}. This is accomplished -by using two opcode suffixes in AT&T syntax. Base names for sign extend -and zero extend are @samp{movs@dots{}} and @samp{movz@dots{}} in AT&T -syntax (@samp{movsx} and @samp{movzx} in Intel syntax). The opcode -suffixes are tacked on to this base name, the @emph{from} suffix before -the @emph{to} suffix. Thus, @samp{movsbl %al, %edx} is AT&T syntax for -``move sign extend @emph{from} %al @emph{to} %edx.'' Possible suffixes, -thus, are @samp{bl} (from byte to long), @samp{bw} (from byte to word), -and @samp{wl} (from word to long). - -@cindex conversion instructions, i386 -@cindex i386 conversion instructions -The Intel-syntax conversion instructions - -@itemize @bullet -@item -@samp{cbw} --- sign-extend byte in @samp{%al} to word in @samp{%ax}, - -@item -@samp{cwde} --- sign-extend word in @samp{%ax} to long in @samp{%eax}, - -@item -@samp{cwd} --- sign-extend word in @samp{%ax} to long in @samp{%dx:%ax}, - -@item -@samp{cdq} --- sign-extend dword in @samp{%eax} to quad in @samp{%edx:%eax}, -@end itemize - -@noindent -are called @samp{cbtw}, @samp{cwtl}, @samp{cwtd}, and @samp{cltd} in -AT&T naming. @code{@value{AS}} accepts either naming for these instructions. - -@cindex jump instructions, i386 -@cindex call instructions, i386 -Far call/jump instructions are @samp{lcall} and @samp{ljmp} in -AT&T syntax, but are @samp{call far} and @samp{jump far} in Intel -convention. - -@node i386-Regs -@section Register Naming - -@cindex i386 registers -@cindex registers, i386 -Register operands are always prefixes with @samp{%}. The 80386 registers -consist of - -@itemize @bullet -@item -the 8 32-bit registers @samp{%eax} (the accumulator), @samp{%ebx}, -@samp{%ecx}, @samp{%edx}, @samp{%edi}, @samp{%esi}, @samp{%ebp} (the -frame pointer), and @samp{%esp} (the stack pointer). - -@item -the 8 16-bit low-ends of these: @samp{%ax}, @samp{%bx}, @samp{%cx}, -@samp{%dx}, @samp{%di}, @samp{%si}, @samp{%bp}, and @samp{%sp}. - -@item -the 8 8-bit registers: @samp{%ah}, @samp{%al}, @samp{%bh}, -@samp{%bl}, @samp{%ch}, @samp{%cl}, @samp{%dh}, and @samp{%dl} (These -are the high-bytes and low-bytes of @samp{%ax}, @samp{%bx}, -@samp{%cx}, and @samp{%dx}) - -@item -the 6 section registers @samp{%cs} (code section), @samp{%ds} -(data section), @samp{%ss} (stack section), @samp{%es}, @samp{%fs}, -and @samp{%gs}. - -@item -the 3 processor control registers @samp{%cr0}, @samp{%cr2}, and -@samp{%cr3}. - -@item -the 6 debug registers @samp{%db0}, @samp{%db1}, @samp{%db2}, -@samp{%db3}, @samp{%db6}, and @samp{%db7}. - -@item -the 2 test registers @samp{%tr6} and @samp{%tr7}. - -@item -the 8 floating point register stack @samp{%st} or equivalently -@samp{%st(0)}, @samp{%st(1)}, @samp{%st(2)}, @samp{%st(3)}, -@samp{%st(4)}, @samp{%st(5)}, @samp{%st(6)}, and @samp{%st(7)}. -@end itemize - -@node i386-prefixes -@section Opcode Prefixes - -@cindex i386 opcode prefixes -@cindex opcode prefixes, i386 -@cindex prefixes, i386 -Opcode prefixes are used to modify the following opcode. They are used -to repeat string instructions, to provide section overrides, to perform -bus lock operations, and to give operand and address size (16-bit -operands are specified in an instruction by prefixing what would -normally be 32-bit operands with a ``operand size'' opcode prefix). -Opcode prefixes are usually given as single-line instructions with no -operands, and must directly precede the instruction they act upon. For -example, the @samp{scas} (scan string) instruction is repeated with: -@smallexample - repne - scas -@end smallexample - -Here is a list of opcode prefixes: - -@cindex section override prefixes, i386 -@itemize @bullet -@item -Section override prefixes @samp{cs}, @samp{ds}, @samp{ss}, @samp{es}, -@samp{fs}, @samp{gs}. These are automatically added by specifying -using the @var{section}:@var{memory-operand} form for memory references. - -@cindex size prefixes, i386 -@item -Operand/Address size prefixes @samp{data16} and @samp{addr16} -change 32-bit operands/addresses into 16-bit operands/addresses. Note -that 16-bit addressing modes (i.e. 8086 and 80286 addressing modes) -are not supported (yet). - -@cindex bus lock prefixes, i386 -@cindex inhibiting interrupts, i386 -@item -The bus lock prefix @samp{lock} inhibits interrupts during -execution of the instruction it precedes. (This is only valid with -certain instructions; see a 80386 manual for details). - -@cindex coprocessor wait, i386 -@item -The wait for coprocessor prefix @samp{wait} waits for the -coprocessor to complete the current instruction. This should never be -needed for the 80386/80387 combination. - -@cindex repeat prefixes, i386 -@item -The @samp{rep}, @samp{repe}, and @samp{repne} prefixes are added -to string instructions to make them repeat @samp{%ecx} times. -@end itemize - -@node i386-Memory -@section Memory References - -@cindex i386 memory references -@cindex memory references, i386 -An Intel syntax indirect memory reference of the form - -@smallexample -@var{section}:[@var{base} + @var{index}*@var{scale} + @var{disp}] -@end smallexample - -@noindent -is translated into the AT&T syntax - -@smallexample -@var{section}:@var{disp}(@var{base}, @var{index}, @var{scale}) -@end smallexample - -@noindent -where @var{base} and @var{index} are the optional 32-bit base and -index registers, @var{disp} is the optional displacement, and -@var{scale}, taking the values 1, 2, 4, and 8, multiplies @var{index} -to calculate the address of the operand. If no @var{scale} is -specified, @var{scale} is taken to be 1. @var{section} specifies the -optional section register for the memory operand, and may override the -default section register (see a 80386 manual for section register -defaults). Note that section overrides in AT&T syntax @emph{must} have -be preceded by a @samp{%}. If you specify a section override which -coincides with the default section register, @code{@value{AS}} does @emph{not} -output any section register override prefixes to assemble the given -instruction. Thus, section overrides can be specified to emphasize which -section register is used for a given memory operand. - -Here are some examples of Intel and AT&T style memory references: - -@table @asis -@item AT&T: @samp{-4(%ebp)}, Intel: @samp{[ebp - 4]} -@var{base} is @samp{%ebp}; @var{disp} is @samp{-4}. @var{section} is -missing, and the default section is used (@samp{%ss} for addressing with -@samp{%ebp} as the base register). @var{index}, @var{scale} are both missing. - -@item AT&T: @samp{foo(,%eax,4)}, Intel: @samp{[foo + eax*4]} -@var{index} is @samp{%eax} (scaled by a @var{scale} 4); @var{disp} is -@samp{foo}. All other fields are missing. The section register here -defaults to @samp{%ds}. - -@item AT&T: @samp{foo(,1)}; Intel @samp{[foo]} -This uses the value pointed to by @samp{foo} as a memory operand. -Note that @var{base} and @var{index} are both missing, but there is only -@emph{one} @samp{,}. This is a syntactic exception. - -@item AT&T: @samp{%gs:foo}; Intel @samp{gs:foo} -This selects the contents of the variable @samp{foo} with section -register @var{section} being @samp{%gs}. -@end table - -Absolute (as opposed to PC relative) call and jump operands must be -prefixed with @samp{*}. If no @samp{*} is specified, @code{@value{AS}} -always chooses PC relative addressing for jump/call labels. - -Any instruction that has a memory operand @emph{must} specify its size (byte, -word, or long) with an opcode suffix (@samp{b}, @samp{w}, or @samp{l}, -respectively). - -@node i386-jumps -@section Handling of Jump Instructions - -@cindex jump optimization, i386 -@cindex i386 jump optimization -Jump instructions are always optimized to use the smallest possible -displacements. This is accomplished by using byte (8-bit) displacement -jumps whenever the target is sufficiently close. If a byte displacement -is insufficient a long (32-bit) displacement is used. We do not support -word (16-bit) displacement jumps (i.e. prefixing the jump instruction -with the @samp{addr16} opcode prefix), since the 80386 insists upon masking -@samp{%eip} to 16 bits after the word displacement is added. - -Note that the @samp{jcxz}, @samp{jecxz}, @samp{loop}, @samp{loopz}, -@samp{loope}, @samp{loopnz} and @samp{loopne} instructions only come in byte -displacements, so that if you use these instructions (@code{@value{GCC}} does -not use them) you may get an error message (and incorrect code). The AT&T -80386 assembler tries to get around this problem by expanding @samp{jcxz foo} -to - -@smallexample - jcxz cx_zero - jmp cx_nonzero -cx_zero: jmp foo -cx_nonzero: -@end smallexample - -@node i386-Float -@section Floating Point - -@cindex i386 floating point -@cindex floating point, i386 -All 80387 floating point types except packed BCD are supported. -(BCD support may be added without much difficulty). These data -types are 16-, 32-, and 64- bit integers, and single (32-bit), -double (64-bit), and extended (80-bit) precision floating point. -Each supported type has an opcode suffix and a constructor -associated with it. Opcode suffixes specify operand's data -types. Constructors build these data types into memory. - -@cindex @code{float} directive, i386 -@cindex @code{single} directive, i386 -@cindex @code{double} directive, i386 -@cindex @code{tfloat} directive, i386 -@itemize @bullet -@item -Floating point constructors are @samp{.float} or @samp{.single}, -@samp{.double}, and @samp{.tfloat} for 32-, 64-, and 80-bit formats. -These correspond to opcode suffixes @samp{s}, @samp{l}, and @samp{t}. -@samp{t} stands for temporary real, and that the 80387 only supports -this format via the @samp{fldt} (load temporary real to stack top) and -@samp{fstpt} (store temporary real and pop stack) instructions. - -@cindex @code{word} directive, i386 -@cindex @code{long} directive, i386 -@cindex @code{int} directive, i386 -@cindex @code{quad} directive, i386 -@item -Integer constructors are @samp{.word}, @samp{.long} or @samp{.int}, and -@samp{.quad} for the 16-, 32-, and 64-bit integer formats. The corresponding -opcode suffixes are @samp{s} (single), @samp{l} (long), and @samp{q} -(quad). As with the temporary real format the 64-bit @samp{q} format is -only present in the @samp{fildq} (load quad integer to stack top) and -@samp{fistpq} (store quad integer and pop stack) instructions. -@end itemize - -Register to register operations do not require opcode suffixes, -so that @samp{fst %st, %st(1)} is equivalent to @samp{fstl %st, %st(1)}. - -@node i386-16bit -@section Writing 16-bit Code - -@cindex i386 16-bit code -@cindex 16-bit code, i386 -@cindex real-mode code, i386 -@cindex @code{code16} directive, i386 -@cindex @code{code32} directive, i386 -While GAS normally writes only ``pure'' 32-bit i386 code, it has limited -support for writing code to run in real mode or in 16-bit protected mode -code segments. To do this, insert a @samp{.code16} directive before the -assembly language instructions to be run in 16-bit mode. You can switch -GAS back to writing normal 32-bit code with the @samp{.code32} directive. - -GAS understands exactly the same assembly language syntax in 16-bit mode as -in 32-bit mode. The function of any given instruction is exactly the same -regardless of mode, as long as the resulting object code is executed in the -mode for which GAS wrote it. So, for example, the @samp{ret} mnemonic -produces a 32-bit return instruction regardless of whether it is to be run -in 16-bit or 32-bit mode. (If GAS is in 16-bit mode, it will add an -operand size prefix to the instruction to force it to be a 32-bit return.) - -This means, for one thing, that you can use @sc{gnu} @sc{cc} to write code to be run -in real mode or 16-bit protected mode. Just insert the statement -@samp{asm(".code16");} at the beginning of your C source file, and while -@sc{gnu} @sc{cc} will still be generating 32-bit code, GAS will automatically add -all the necessary size prefixes to make that code run in 16-bit mode. Of -course, since @sc{gnu} @sc{cc} only writes small-model code (it doesn't know how to -attach segment selectors to pointers like native x86 compilers do), any -16-bit code you write with @sc{gnu} @sc{cc} will essentially be limited to a 64K -address space. Also, there will be a code size and performance penalty -due to all the extra address and operand size prefixes GAS has to add to -the instructions. - -Note that placing GAS in 16-bit mode does not mean that the resulting -code will necessarily run on a 16-bit pre-80386 processor. To write code -that runs on such a processor, you would have to refrain from using -@emph{any} 32-bit constructs which require GAS to output address or -operand size prefixes. At the moment this would be rather difficult, -because GAS currently supports @emph{only} 32-bit addressing modes: when -writing 16-bit code, it @emph{always} outputs address size prefixes for any -instruction that uses a non-register addressing mode. So you can write -code that runs on 16-bit processors, but only if that code never references -memory. - -@node i386-Notes -@section Notes - -@cindex i386 @code{mul}, @code{imul} instructions -@cindex @code{mul} instruction, i386 -@cindex @code{imul} instruction, i386 -There is some trickery concerning the @samp{mul} and @samp{imul} -instructions that deserves mention. The 16-, 32-, and 64-bit expanding -multiplies (base opcode @samp{0xf6}; extension 4 for @samp{mul} and 5 -for @samp{imul}) can be output only in the one operand form. Thus, -@samp{imul %ebx, %eax} does @emph{not} select the expanding multiply; -the expanding multiply would clobber the @samp{%edx} register, and this -would confuse @code{@value{GCC}} output. Use @samp{imul %ebx} to get the -64-bit product in @samp{%edx:%eax}. - -We have added a two operand form of @samp{imul} when the first operand -is an immediate mode expression and the second operand is a register. -This is just a shorthand, so that, multiplying @samp{%eax} by 69, for -example, can be done with @samp{imul $69, %eax} rather than @samp{imul -$69, %eax, %eax}. - |