-@c Copyright (C) 1991, 92, 93, 94, 95, 97, 1998 Free Software Foundation, Inc.
+@c Copyright (C) 1991-2017 Free Software Foundation, Inc.
@c This is part of the GAS manual.
@c For copying conditions, see the file as.texinfo.
+@c man end
+
@ifset GENERIC
@page
@node i386-Dependent
@end ifclear
@cindex i386 support
-@cindex i80306 support
+@cindex i80386 support
@cindex x86-64 support
The i386 version @code{@value{AS}} supports both the original Intel 386
@menu
* i386-Options:: Options
-* i386-Syntax:: AT&T Syntax versus Intel Syntax
+* i386-Directives:: X86 specific directives
+* i386-Syntax:: Syntactical considerations
* i386-Mnemonics:: Instruction Naming
* i386-Regs:: Register Naming
* i386-Prefixes:: Instruction Prefixes
* i386-Memory:: Memory References
-* i386-jumps:: Handling of Jump Instructions
+* i386-Jumps:: Handling of Jump Instructions
* i386-Float:: Floating Point
* i386-SIMD:: Intel's MMX and AMD's 3DNow! SIMD Operations
+* i386-LWP:: AMD's Lightweight Profiling Instructions
+* i386-BMI:: Bit Manipulation Instruction
+* i386-TBM:: AMD's Trailing Bit Manipulation Instructions
* i386-16bit:: Writing 16-bit Code
* i386-Arch:: Specifying an x86 CPU architecture
* i386-Bugs:: AT&T Syntax bugs
@cindex options for i386
@cindex options for x86-64
@cindex i386 options
-@cindex x86-64 options
+@cindex x86-64 options
The i386 version of @code{@value{AS}} has a few machine
dependent options:
-@table @code
+@c man begin OPTIONS
+@table @gcctabopt
@cindex @samp{--32} option, i386
@cindex @samp{--32} option, x86-64
+@cindex @samp{--x32} option, i386
+@cindex @samp{--x32} option, x86-64
@cindex @samp{--64} option, i386
@cindex @samp{--64} option, x86-64
-@item --32 | --64
-Select the word size, either 32 bits or 64 bits. Selecting 32-bit
-implies Intel i386 architecture, while 64-bit implies AMD x86-64
-architecture.
+@item --32 | --x32 | --64
+Select the word size, either 32 bits or 64 bits. @samp{--32}
+implies Intel i386 architecture, while @samp{--x32} and @samp{--64}
+imply AMD x86-64 architecture with 32-bit or 64-bit word-size
+respectively.
These options are only available with the ELF object file format, and
require that the necessary BFD support has been included (on a 32-bit
platform you have to add --enable-64-bit-bfd to configure enable 64-bit
usage and use x86-64 as target platform).
+
+@item -n
+By default, x86 GAS replaces multiple nop instructions used for
+alignment within code sections with multi-byte nop instructions such
+as leal 0(%esi,1),%esi. This switch disables the optimization.
+
+@cindex @samp{--divide} option, i386
+@item --divide
+On SVR4-derived platforms, the character @samp{/} is treated as a comment
+character, which means that it cannot be used in expressions. The
+@samp{--divide} option turns @samp{/} into a normal character. This does
+not disable @samp{/} at the beginning of a line starting a comment, or
+affect using @samp{#} for starting a comment.
+
+@cindex @samp{-march=} option, i386
+@cindex @samp{-march=} option, x86-64
+@item -march=@var{CPU}[+@var{EXTENSION}@dots{}]
+This option specifies the target processor. The assembler will
+issue an error message if an attempt is made to assemble an instruction
+which will not execute on the target processor. The following
+processor names are recognized:
+@code{i8086},
+@code{i186},
+@code{i286},
+@code{i386},
+@code{i486},
+@code{i586},
+@code{i686},
+@code{pentium},
+@code{pentiumpro},
+@code{pentiumii},
+@code{pentiumiii},
+@code{pentium4},
+@code{prescott},
+@code{nocona},
+@code{core},
+@code{core2},
+@code{corei7},
+@code{l1om},
+@code{k1om},
+@code{iamcu},
+@code{k6},
+@code{k6_2},
+@code{athlon},
+@code{opteron},
+@code{k8},
+@code{amdfam10},
+@code{bdver1},
+@code{bdver2},
+@code{bdver3},
+@code{bdver4},
+@code{znver1},
+@code{btver1},
+@code{btver2},
+@code{generic32} and
+@code{generic64}.
+
+In addition to the basic instruction set, the assembler can be told to
+accept various extension mnemonics. For example,
+@code{-march=i686+sse4+vmx} extends @var{i686} with @var{sse4} and
+@var{vmx}. The following extensions are currently supported:
+@code{8087},
+@code{287},
+@code{387},
+@code{687},
+@code{no87},
+@code{no287},
+@code{no387},
+@code{no687},
+@code{mmx},
+@code{nommx},
+@code{sse},
+@code{sse2},
+@code{sse3},
+@code{ssse3},
+@code{sse4.1},
+@code{sse4.2},
+@code{sse4},
+@code{nosse},
+@code{nosse2},
+@code{nosse3},
+@code{nossse3},
+@code{nosse4.1},
+@code{nosse4.2},
+@code{nosse4},
+@code{avx},
+@code{avx2},
+@code{noavx},
+@code{noavx2},
+@code{adx},
+@code{rdseed},
+@code{prfchw},
+@code{smap},
+@code{mpx},
+@code{sha},
+@code{rdpid},
+@code{ptwrite},
+@code{cet},
+@code{gfni},
+@code{vaes},
+@code{vpclmulqdq},
+@code{prefetchwt1},
+@code{clflushopt},
+@code{se1},
+@code{clwb},
+@code{avx512f},
+@code{avx512cd},
+@code{avx512er},
+@code{avx512pf},
+@code{avx512vl},
+@code{avx512bw},
+@code{avx512dq},
+@code{avx512ifma},
+@code{avx512vbmi},
+@code{avx512_4fmaps},
+@code{avx512_4vnniw},
+@code{avx512_vpopcntdq},
+@code{avx512_vbmi2},
+@code{avx512_vnni},
+@code{avx512_bitalg},
+@code{noavx512f},
+@code{noavx512cd},
+@code{noavx512er},
+@code{noavx512pf},
+@code{noavx512vl},
+@code{noavx512bw},
+@code{noavx512dq},
+@code{noavx512ifma},
+@code{noavx512vbmi},
+@code{noavx512_4fmaps},
+@code{noavx512_4vnniw},
+@code{noavx512_vpopcntdq},
+@code{noavx512_vbmi2},
+@code{noavx512_vnni},
+@code{noavx512_bitalg},
+@code{vmx},
+@code{vmfunc},
+@code{smx},
+@code{xsave},
+@code{xsaveopt},
+@code{xsavec},
+@code{xsaves},
+@code{aes},
+@code{pclmul},
+@code{fsgsbase},
+@code{rdrnd},
+@code{f16c},
+@code{bmi2},
+@code{fma},
+@code{movbe},
+@code{ept},
+@code{lzcnt},
+@code{hle},
+@code{rtm},
+@code{invpcid},
+@code{clflush},
+@code{mwaitx},
+@code{clzero},
+@code{lwp},
+@code{fma4},
+@code{xop},
+@code{cx16},
+@code{syscall},
+@code{rdtscp},
+@code{3dnow},
+@code{3dnowa},
+@code{sse4a},
+@code{sse5},
+@code{svme},
+@code{abm} and
+@code{padlock}.
+Note that rather than extending a basic instruction set, the extension
+mnemonics starting with @code{no} revoke the respective functionality.
+
+When the @code{.arch} directive is used with @option{-march}, the
+@code{.arch} directive will take precedent.
+
+@cindex @samp{-mtune=} option, i386
+@cindex @samp{-mtune=} option, x86-64
+@item -mtune=@var{CPU}
+This option specifies a processor to optimize for. When used in
+conjunction with the @option{-march} option, only instructions
+of the processor specified by the @option{-march} option will be
+generated.
+
+Valid @var{CPU} values are identical to the processor list of
+@option{-march=@var{CPU}}.
+
+@cindex @samp{-msse2avx} option, i386
+@cindex @samp{-msse2avx} option, x86-64
+@item -msse2avx
+This option specifies that the assembler should encode SSE instructions
+with VEX prefix.
+
+@cindex @samp{-msse-check=} option, i386
+@cindex @samp{-msse-check=} option, x86-64
+@item -msse-check=@var{none}
+@itemx -msse-check=@var{warning}
+@itemx -msse-check=@var{error}
+These options control if the assembler should check SSE instructions.
+@option{-msse-check=@var{none}} will make the assembler not to check SSE
+instructions, which is the default. @option{-msse-check=@var{warning}}
+will make the assembler issue a warning for any SSE instruction.
+@option{-msse-check=@var{error}} will make the assembler issue an error
+for any SSE instruction.
+
+@cindex @samp{-mavxscalar=} option, i386
+@cindex @samp{-mavxscalar=} option, x86-64
+@item -mavxscalar=@var{128}
+@itemx -mavxscalar=@var{256}
+These options control how the assembler should encode scalar AVX
+instructions. @option{-mavxscalar=@var{128}} will encode scalar
+AVX instructions with 128bit vector length, which is the default.
+@option{-mavxscalar=@var{256}} will encode scalar AVX instructions
+with 256bit vector length.
+
+@cindex @samp{-mevexlig=} option, i386
+@cindex @samp{-mevexlig=} option, x86-64
+@item -mevexlig=@var{128}
+@itemx -mevexlig=@var{256}
+@itemx -mevexlig=@var{512}
+These options control how the assembler should encode length-ignored
+(LIG) EVEX instructions. @option{-mevexlig=@var{128}} will encode LIG
+EVEX instructions with 128bit vector length, which is the default.
+@option{-mevexlig=@var{256}} and @option{-mevexlig=@var{512}} will
+encode LIG EVEX instructions with 256bit and 512bit vector length,
+respectively.
+
+@cindex @samp{-mevexwig=} option, i386
+@cindex @samp{-mevexwig=} option, x86-64
+@item -mevexwig=@var{0}
+@itemx -mevexwig=@var{1}
+These options control how the assembler should encode w-ignored (WIG)
+EVEX instructions. @option{-mevexwig=@var{0}} will encode WIG
+EVEX instructions with evex.w = 0, which is the default.
+@option{-mevexwig=@var{1}} will encode WIG EVEX instructions with
+evex.w = 1.
+
+@cindex @samp{-mmnemonic=} option, i386
+@cindex @samp{-mmnemonic=} option, x86-64
+@item -mmnemonic=@var{att}
+@itemx -mmnemonic=@var{intel}
+This option specifies instruction mnemonic for matching instructions.
+The @code{.att_mnemonic} and @code{.intel_mnemonic} directives will
+take precedent.
+
+@cindex @samp{-msyntax=} option, i386
+@cindex @samp{-msyntax=} option, x86-64
+@item -msyntax=@var{att}
+@itemx -msyntax=@var{intel}
+This option specifies instruction syntax when processing instructions.
+The @code{.att_syntax} and @code{.intel_syntax} directives will
+take precedent.
+
+@cindex @samp{-mnaked-reg} option, i386
+@cindex @samp{-mnaked-reg} option, x86-64
+@item -mnaked-reg
+This option specifies that registers don't require a @samp{%} prefix.
+The @code{.att_syntax} and @code{.intel_syntax} directives will take precedent.
+
+@cindex @samp{-madd-bnd-prefix} option, i386
+@cindex @samp{-madd-bnd-prefix} option, x86-64
+@item -madd-bnd-prefix
+This option forces the assembler to add BND prefix to all branches, even
+if such prefix was not explicitly specified in the source code.
+
+@cindex @samp{-mshared} option, i386
+@cindex @samp{-mshared} option, x86-64
+@item -mno-shared
+On ELF target, the assembler normally optimizes out non-PLT relocations
+against defined non-weak global branch targets with default visibility.
+The @samp{-mshared} option tells the assembler to generate code which
+may go into a shared library where all non-weak global branch targets
+with default visibility can be preempted. The resulting code is
+slightly bigger. This option only affects the handling of branch
+instructions.
+
+@cindex @samp{-mbig-obj} option, x86-64
+@item -mbig-obj
+On x86-64 PE/COFF target this option forces the use of big object file
+format, which allows more than 32768 sections.
+
+@cindex @samp{-momit-lock-prefix=} option, i386
+@cindex @samp{-momit-lock-prefix=} option, x86-64
+@item -momit-lock-prefix=@var{no}
+@itemx -momit-lock-prefix=@var{yes}
+These options control how the assembler should encode lock prefix.
+This option is intended as a workaround for processors, that fail on
+lock prefix. This option can only be safely used with single-core,
+single-thread computers
+@option{-momit-lock-prefix=@var{yes}} will omit all lock prefixes.
+@option{-momit-lock-prefix=@var{no}} will encode lock prefix as usual,
+which is the default.
+
+@cindex @samp{-mfence-as-lock-add=} option, i386
+@cindex @samp{-mfence-as-lock-add=} option, x86-64
+@item -mfence-as-lock-add=@var{no}
+@itemx -mfence-as-lock-add=@var{yes}
+These options control how the assembler should encode lfence, mfence and
+sfence.
+@option{-mfence-as-lock-add=@var{yes}} will encode lfence, mfence and
+sfence as @samp{lock addl $0x0, (%rsp)} in 64-bit mode and
+@samp{lock addl $0x0, (%esp)} in 32-bit mode.
+@option{-mfence-as-lock-add=@var{no}} will encode lfence, mfence and
+sfence as usual, which is the default.
+
+@cindex @samp{-mrelax-relocations=} option, i386
+@cindex @samp{-mrelax-relocations=} option, x86-64
+@item -mrelax-relocations=@var{no}
+@itemx -mrelax-relocations=@var{yes}
+These options control whether the assembler should generate relax
+relocations, R_386_GOT32X, in 32-bit mode, or R_X86_64_GOTPCRELX and
+R_X86_64_REX_GOTPCRELX, in 64-bit mode.
+@option{-mrelax-relocations=@var{yes}} will generate relax relocations.
+@option{-mrelax-relocations=@var{no}} will not generate relax
+relocations. The default can be controlled by a configure option
+@option{--enable-x86-relax-relocations}.
+
+@cindex @samp{-mevexrcig=} option, i386
+@cindex @samp{-mevexrcig=} option, x86-64
+@item -mevexrcig=@var{rne}
+@itemx -mevexrcig=@var{rd}
+@itemx -mevexrcig=@var{ru}
+@itemx -mevexrcig=@var{rz}
+These options control how the assembler should encode SAE-only
+EVEX instructions. @option{-mevexrcig=@var{rne}} will encode RC bits
+of EVEX instruction with 00, which is the default.
+@option{-mevexrcig=@var{rd}}, @option{-mevexrcig=@var{ru}}
+and @option{-mevexrcig=@var{rz}} will encode SAE-only EVEX instructions
+with 01, 10 and 11 RC bits, respectively.
+
+@cindex @samp{-mamd64} option, x86-64
+@cindex @samp{-mintel64} option, x86-64
+@item -mamd64
+@itemx -mintel64
+This option specifies that the assembler should accept only AMD64 or
+Intel64 ISA in 64-bit mode. The default is to accept both.
+
+@end table
+@c man end
+
+@node i386-Directives
+@section x86 specific Directives
+
+@cindex machine directives, x86
+@cindex x86 machine directives
+@table @code
+
+@cindex @code{lcomm} directive, COFF
+@item .lcomm @var{symbol} , @var{length}[, @var{alignment}]
+Reserve @var{length} (an absolute expression) bytes for a local common
+denoted by @var{symbol}. The section and value of @var{symbol} are
+those of the new local common. The addresses are allocated in the bss
+section, so that at run-time the bytes start off zeroed. Since
+@var{symbol} is not declared global, it is normally not visible to
+@code{@value{LD}}. The optional third parameter, @var{alignment},
+specifies the desired alignment of the symbol in the bss section.
+
+This directive is only available for COFF based x86 targets.
+
+@c FIXME: Document other x86 specific directives ? Eg: .code16gcc,
+@c .largecomm
+
@end table
@node i386-Syntax
-@section AT&T Syntax versus Intel Syntax
+@section i386 Syntactical Considerations
+@menu
+* i386-Variations:: AT&T Syntax versus Intel Syntax
+* i386-Chars:: Special Characters
+@end menu
+
+@node i386-Variations
+@subsection AT&T Syntax versus Intel Syntax
@cindex i386 intel_syntax pseudo op
@cindex intel_syntax pseudo op, i386
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. Note that instructions with more than one
-source operand, such as the @samp{enter} instruction, do @emph{not} have
-reversed order. @ref{i386-Bugs}.
+previous Unix assemblers. Note that @samp{bound}, @samp{invlpga}, and
+instructions with 2 immediate operands, such as the @samp{enter}
+instruction, do @emph{not} have reversed order. @ref{i386-Bugs}.
@cindex mnemonic suffixes, i386
@cindex sizes operands, i386
Intel @samp{mov al, byte ptr @var{foo}} is @samp{movb @var{foo}, %al} in AT&T
syntax.
+In 64-bit code, @samp{movabs} can be used to encode the @samp{mov}
+instruction with the 64-bit displacement or immediate operand.
+
@cindex return instructions, i386
@cindex i386 jump, call, return
@cindex return instructions, x86-64
programs. Unix style systems expect all programs to be single sections.
@end itemize
+@node i386-Chars
+@subsection Special Characters
+
+@cindex line comment character, i386
+@cindex i386 line comment character
+The presence of a @samp{#} appearing anywhere on a line indicates the
+start of a comment that extends to the end of that line.
+
+If a @samp{#} appears as the first character of a line then the whole
+line is treated as a comment, but in this case the line can also be a
+logical line number directive (@pxref{Comments}) or a preprocessor
+control command (@pxref{Preprocessing}).
+
+If the @option{--divide} command line option has not been specified
+then the @samp{/} character appearing anywhere on a line also
+introduces a line comment.
+
+@cindex line separator, i386
+@cindex statement separator, i386
+@cindex i386 line separator
+The @samp{;} character can be used to separate statements on the same
+line.
+
@node i386-Mnemonics
-@section Instruction Naming
+@section i386-Mnemonics
+@subsection Instruction Naming
@cindex i386 instruction naming
@cindex instruction naming, i386
@samp{wq} (from word to quadruple word), and @samp{lq} (from long to
quadruple word).
+@cindex encoding options, i386
+@cindex encoding options, x86-64
+
+Different encoding options can be specified via pseudo prefixes:
+
+@itemize @bullet
+@item
+@samp{@{disp8@}} -- prefer 8-bit displacement.
+
+@item
+@samp{@{disp32@}} -- prefer 32-bit displacement.
+
+@item
+@samp{@{load@}} -- prefer load-form instruction.
+
+@item
+@samp{@{store@}} -- prefer store-form instruction.
+
+@item
+@samp{@{vex2@}} -- prefer 2-byte VEX prefix for VEX instruction.
+
+@item
+@samp{@{vex3@}} -- prefer 3-byte VEX prefix for VEX instruction.
+
+@item
+@samp{@{evex@}} -- encode with EVEX prefix.
+@end itemize
+
@cindex conversion instructions, i386
@cindex i386 conversion instructions
@cindex conversion instructions, x86-64
(x86-64 only),
@item
-@samp{cdo} --- sign-extend quad in @samp{%rax} to octuple in
+@samp{cqo} --- sign-extend quad in @samp{%rax} to octuple in
@samp{%rdx:%rax} (x86-64 only),
@end itemize
AT&T syntax, but are @samp{call far} and @samp{jump far} in Intel
convention.
+@subsection AT&T Mnemonic versus Intel Mnemonic
+
+@cindex i386 mnemonic compatibility
+@cindex mnemonic compatibility, i386
+
+@code{@value{AS}} supports assembly using Intel mnemonic.
+@code{.intel_mnemonic} selects Intel mnemonic with Intel syntax, and
+@code{.att_mnemonic} switches back to the usual AT&T mnemonic with AT&T
+syntax for compatibility with the output of @code{@value{GCC}}.
+Several x87 instructions, @samp{fadd}, @samp{fdiv}, @samp{fdivp},
+@samp{fdivr}, @samp{fdivrp}, @samp{fmul}, @samp{fsub}, @samp{fsubp},
+@samp{fsubr} and @samp{fsubrp}, are implemented in AT&T System V/386
+assembler with different mnemonics from those in Intel IA32 specification.
+@code{@value{GCC}} generates those instructions with AT&T mnemonic.
+
@node i386-Regs
@section Register Naming
and @samp{%gs}.
@item
-the 3 processor control registers @samp{%cr0}, @samp{%cr2}, and
-@samp{%cr3}.
+the 5 processor control registers @samp{%cr0}, @samp{%cr2},
+@samp{%cr3}, @samp{%cr4}, and @samp{%cr8}.
@item
the 6 debug registers @samp{%db0}, @samp{%db1}, @samp{%db2},
@samp{%mm6} and @samp{%mm7}.
@item
-the 8 SSE registers registers @samp{%xmm0}, @samp{%xmm1}, @samp{%xmm2},
+the 8 128-bit SSE registers registers @samp{%xmm0}, @samp{%xmm1}, @samp{%xmm2},
@samp{%xmm3}, @samp{%xmm4}, @samp{%xmm5}, @samp{%xmm6} and @samp{%xmm7}.
@end itemize
the 8 extended registers @samp{%r8}--@samp{%r15}.
@item
-the 8 32-bit low ends of the extended registers: @samp{%r8d}--@samp{%r15d}
+the 8 32-bit low ends of the extended registers: @samp{%r8d}--@samp{%r15d}.
@item
-the 8 16-bit low ends of the extended registers: @samp{%r8w}--@samp{%r15w}
+the 8 16-bit low ends of the extended registers: @samp{%r8w}--@samp{%r15w}.
@item
-the 8 8-bit low ends of the extended registers: @samp{%r8b}--@samp{%r15b}
+the 8 8-bit low ends of the extended registers: @samp{%r8b}--@samp{%r15b}.
@item
the 4 8-bit registers: @samp{%sil}, @samp{%dil}, @samp{%bpl}, @samp{%spl}.
the 8 debug registers: @samp{%db8}--@samp{%db15}.
@item
-the 8 SSE registers: @samp{%xmm8}--@samp{%xmm15}.
+the 8 128-bit SSE registers: @samp{%xmm8}--@samp{%xmm15}.
+@end itemize
+
+With the AVX extensions more registers were made available:
+
+@itemize @bullet
+
+@item
+the 16 256-bit SSE @samp{%ymm0}--@samp{%ymm15} (only the first 8
+available in 32-bit mode). The bottom 128 bits are overlaid with the
+@samp{xmm0}--@samp{xmm15} registers.
+
+@end itemize
+
+The AVX2 extensions made in 64-bit mode more registers available:
+
+@itemize @bullet
+
+@item
+the 16 128-bit registers @samp{%xmm16}--@samp{%xmm31} and the 16 256-bit
+registers @samp{%ymm16}--@samp{%ymm31}.
+
+@end itemize
+
+The AVX512 extensions added the following registers:
+
+@itemize @bullet
+
+@item
+the 32 512-bit registers @samp{%zmm0}--@samp{%zmm31} (only the first 8
+available in 32-bit mode). The bottom 128 bits are overlaid with the
+@samp{%xmm0}--@samp{%xmm31} registers and the first 256 bits are
+overlaid with the @samp{%ymm0}--@samp{%ymm31} registers.
+
+@item
+the 8 mask registers @samp{%k0}--@samp{%k7}.
+
@end itemize
@node i386-Prefixes
Other addressing modes remain unchanged in x86-64 architecture, except
registers used are 64-bit instead of 32-bit.
-@node i386-jumps
+@node i386-Jumps
@section Handling of Jump Instructions
@cindex jump optimization, i386
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
+is insufficient a long displacement is used. We do not support
word (16-bit) displacement jumps in 32-bit mode (i.e. prefixing the jump
instruction with the @samp{data16} instruction prefix), since the 80386
insists upon masking @samp{%eip} to 16 bits after the word displacement
-is added.
+is added. (See also @pxref{i386-Arch})
Note that the @samp{jcxz}, @samp{jecxz}, @samp{loop}, @samp{loopz},
@samp{loope}, @samp{loopnz} and @samp{loopne} instructions only come in byte
@code{@value{AS}} supports Intel's MMX instruction set (SIMD
instructions for integer data), available on Intel's Pentium MMX
processors and Pentium II processors, AMD's K6 and K6-2 processors,
-Cyrix' M2 processor, and probably others. It also supports AMD's 3DNow!
+Cyrix' M2 processor, and probably others. It also supports AMD's 3DNow!@:
instruction set (SIMD instructions for 32-bit floating point data)
available on AMD's K6-2 processor and possibly others in the future.
See Intel and AMD documentation, keeping in mind that the operand order in
instructions is reversed from the Intel syntax.
+@node i386-LWP
+@section AMD's Lightweight Profiling Instructions
+
+@cindex LWP, i386
+@cindex LWP, x86-64
+
+@code{@value{AS}} supports AMD's Lightweight Profiling (LWP)
+instruction set, available on AMD's Family 15h (Orochi) processors.
+
+LWP enables applications to collect and manage performance data, and
+react to performance events. The collection of performance data
+requires no context switches. LWP runs in the context of a thread and
+so several counters can be used independently across multiple threads.
+LWP can be used in both 64-bit and legacy 32-bit modes.
+
+For detailed information on the LWP instruction set, see the
+@cite{AMD Lightweight Profiling Specification} available at
+@uref{http://developer.amd.com/cpu/LWP,Lightweight Profiling Specification}.
+
+@node i386-BMI
+@section Bit Manipulation Instructions
+
+@cindex BMI, i386
+@cindex BMI, x86-64
+
+@code{@value{AS}} supports the Bit Manipulation (BMI) instruction set.
+
+BMI instructions provide several instructions implementing individual
+bit manipulation operations such as isolation, masking, setting, or
+resetting.
+
+@c Need to add a specification citation here when available.
+
+@node i386-TBM
+@section AMD's Trailing Bit Manipulation Instructions
+
+@cindex TBM, i386
+@cindex TBM, x86-64
+
+@code{@value{AS}} supports AMD's Trailing Bit Manipulation (TBM)
+instruction set, available on AMD's BDVER2 processors (Trinity and
+Viperfish).
+
+TBM instructions provide instructions implementing individual bit
+manipulation operations such as isolating, masking, setting, resetting,
+complementing, and operations on trailing zeros and ones.
+
+@c Need to add a specification citation here when available.
+
@node i386-16bit
@section Writing 16-bit Code
it also supports writing code to run in real mode or in 16-bit protected
mode code segments. To do this, put a @samp{.code16} or
@samp{.code16gcc} directive before the assembly language instructions to
-be run in 16-bit mode. You can switch @code{@value{AS}} back to writing
-normal 32-bit code with the @samp{.code32} directive.
+be run in 16-bit mode. You can switch @code{@value{AS}} to writing
+32-bit code with the @samp{.code32} directive or 64-bit code with the
+@samp{.code64} directive.
@samp{.code16gcc} provides experimental support for generating 16-bit
code from gcc, and differs from @samp{.code16} in that @samp{call},
@end smallexample
The same code in a 16-bit code section would generate the machine
-opcode bytes @samp{6a 04} (ie. without the operand size prefix), which
+opcode bytes @samp{6a 04} (i.e., without the operand size prefix), which
is correct since the processor default operand size is assumed to be 16
bits in a 16-bit code section.
-@node i386-Bugs
-@section AT&T Syntax bugs
-
-The UnixWare assembler, and probably other AT&T derived ix86 Unix
-assemblers, generate floating point instructions with reversed source
-and destination registers in certain cases. Unfortunately, gcc and
-possibly many other programs use this reversed syntax, so we're stuck
-with it.
-
-For example
-
-@smallexample
- fsub %st,%st(3)
-@end smallexample
-@noindent
-results in @samp{%st(3)} being updated to @samp{%st - %st(3)} rather
-than the expected @samp{%st(3) - %st}. This happens with all the
-non-commutative arithmetic floating point operations with two register
-operands where the source register is @samp{%st} and the destination
-register is @samp{%st(i)}.
-
@node i386-Arch
@section Specifying CPU Architecture
@cindex x86-64 arch directive
@code{@value{AS}} may be told to assemble for a particular CPU
-architecture with the @code{.arch @var{cpu_type}} directive. This
+(sub-)architecture with the @code{.arch @var{cpu_type}} directive. This
directive enables a warning when gas detects an instruction that is not
supported on the CPU specified. The choices for @var{cpu_type} are:
@multitable @columnfractions .20 .20 .20 .20
@item @samp{i8086} @tab @samp{i186} @tab @samp{i286} @tab @samp{i386}
@item @samp{i486} @tab @samp{i586} @tab @samp{i686} @tab @samp{pentium}
-@item @samp{pentiumpro} @tab @samp{pentium4} @tab @samp{k6} @tab @samp{athlon}
-@item @samp{sledgehammer}
+@item @samp{pentiumpro} @tab @samp{pentiumii} @tab @samp{pentiumiii} @tab @samp{pentium4}
+@item @samp{prescott} @tab @samp{nocona} @tab @samp{core} @tab @samp{core2}
+@item @samp{corei7} @tab @samp{l1om} @tab @samp{k1om} @samp{iamcu}
+@item @samp{k6} @tab @samp{k6_2} @tab @samp{athlon} @tab @samp{k8}
+@item @samp{amdfam10} @tab @samp{bdver1} @tab @samp{bdver2} @tab @samp{bdver3}
+@item @samp{bdver4} @tab @samp{znver1} @tab @samp{btver1} @tab @samp{btver2}
+@item @samp{generic32} @tab @samp{generic64}
+@item @samp{.mmx} @tab @samp{.sse} @tab @samp{.sse2} @tab @samp{.sse3}
+@item @samp{.ssse3} @tab @samp{.sse4.1} @tab @samp{.sse4.2} @tab @samp{.sse4}
+@item @samp{.avx} @tab @samp{.vmx} @tab @samp{.smx} @tab @samp{.ept}
+@item @samp{.clflush} @tab @samp{.movbe} @tab @samp{.xsave} @tab @samp{.xsaveopt}
+@item @samp{.aes} @tab @samp{.pclmul} @tab @samp{.fma} @tab @samp{.fsgsbase}
+@item @samp{.rdrnd} @tab @samp{.f16c} @tab @samp{.avx2} @tab @samp{.bmi2}
+@item @samp{.lzcnt} @tab @samp{.invpcid} @tab @samp{.vmfunc} @tab @samp{.hle}
+@item @samp{.rtm} @tab @samp{.adx} @tab @samp{.rdseed} @tab @samp{.prfchw}
+@item @samp{.smap} @tab @samp{.mpx} @tab @samp{.sha} @tab @samp{.prefetchwt1}
+@item @samp{.clflushopt} @tab @samp{.xsavec} @tab @samp{.xsaves} @tab @samp{.se1}
+@item @samp{.avx512f} @tab @samp{.avx512cd} @tab @samp{.avx512er} @tab @samp{.avx512pf}
+@item @samp{.avx512vl} @tab @samp{.avx512bw} @tab @samp{.avx512dq} @tab @samp{.avx512ifma}
+@item @samp{.avx512vbmi} @tab @samp{.avx512_4fmaps} @tab @samp{.avx512_4vnniw}
+@item @samp{.avx512_vpopcntdq} @tab @samp{.avx512_vbmi2} @tab @samp{.avx512_vnni}
+@item @samp{.avx512_bitalg}
+@item @samp{.clwb} @tab @samp{.rdpid} @tab @samp{.ptwrite} @tab @item @samp{.cet}
+@item @samp{.3dnow} @tab @samp{.3dnowa} @tab @samp{.sse4a} @tab @samp{.sse5}
+@item @samp{.syscall} @tab @samp{.rdtscp} @tab @samp{.svme} @tab @samp{.abm}
+@item @samp{.lwp} @tab @samp{.fma4} @tab @samp{.xop} @tab @samp{.cx16}
+@item @samp{.padlock} @tab @samp{.clzero} @tab @samp{.mwaitx} @tab @samp{.gfni}
+@item @samp{.vaes} @tab @samp{.vpclmulqdq}
@end multitable
-Apart from the warning, there is only one other effect on
-@code{@value{AS}} operation; If you specify a CPU other than
+Apart from the warning, there are only two other effects on
+@code{@value{AS}} operation; Firstly, if you specify a CPU other than
@samp{i486}, then shift by one instructions such as @samp{sarl $1, %eax}
will automatically use a two byte opcode sequence. The larger three
byte opcode sequence is used on the 486 (and when no architecture is
specified) because it executes faster on the 486. Note that you can
explicitly request the two byte opcode by writing @samp{sarl %eax}.
+Secondly, if you specify @samp{i8086}, @samp{i186}, or @samp{i286},
+@emph{and} @samp{.code16} or @samp{.code16gcc} then byte offset
+conditional jumps will be promoted when necessary to a two instruction
+sequence consisting of a conditional jump of the opposite sense around
+an unconditional jump to the target.
+
+Following the CPU architecture (but not a sub-architecture, which are those
+starting with a dot), you may specify @samp{jumps} or @samp{nojumps} to
+control automatic promotion of conditional jumps. @samp{jumps} is the
+default, and enables jump promotion; All external jumps will be of the long
+variety, and file-local jumps will be promoted as necessary.
+(@pxref{i386-Jumps}) @samp{nojumps} leaves external conditional jumps as
+byte offset jumps, and warns about file-local conditional jumps that
+@code{@value{AS}} promotes.
+Unconditional jumps are treated as for @samp{jumps}.
+
+For example
+
+@smallexample
+ .arch i8086,nojumps
+@end smallexample
+
+@node i386-Bugs
+@section AT&T Syntax bugs
+
+The UnixWare assembler, and probably other AT&T derived ix86 Unix
+assemblers, generate floating point instructions with reversed source
+and destination registers in certain cases. Unfortunately, gcc and
+possibly many other programs use this reversed syntax, so we're stuck
+with it.
+
+For example
+
+@smallexample
+ fsub %st,%st(3)
+@end smallexample
+@noindent
+results in @samp{%st(3)} being updated to @samp{%st - %st(3)} rather
+than the expected @samp{%st(3) - %st}. This happens with all the
+non-commutative arithmetic floating point operations with two register
+operands where the source register is @samp{%st} and the destination
+register is @samp{%st(i)}.
@node i386-Notes
@section Notes
projects / deliverable / binutils-gdb.git / blobdiff