-@c Copyright 1996, 1997, 1998, 1999, 2000, 2001, 2003
-@c Free Software Foundation, Inc.
+@c Copyright 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
+@c 2006, 2007, 2008, 2009, 2010, 2011 Free Software Foundation, Inc.
@c This is part of the GAS manual.
@c For copying conditions, see the file as.texinfo.
* ARM Floating Point:: Floating Point
* ARM Directives:: ARM Machine Directives
* ARM Opcodes:: Opcodes
+* ARM Mapping Symbols:: Mapping Symbols
+* ARM Unwinding Tutorial:: Unwinding
@end menu
@node ARM Options
@code{arm7500fe},
@code{arm7t},
@code{arm7tdmi},
+@code{arm7tdmi-s},
@code{arm8},
@code{arm810},
@code{strongarm},
@code{arm922t},
@code{arm940t},
@code{arm9tdmi},
+@code{fa526} (Faraday FA526 processor),
+@code{fa626} (Faraday FA626 processor),
@code{arm9e},
+@code{arm926e},
+@code{arm926ej-s},
@code{arm946e-r0},
@code{arm946e},
+@code{arm946e-s},
@code{arm966e-r0},
@code{arm966e},
+@code{arm966e-s},
+@code{arm968e-s},
@code{arm10t},
+@code{arm10tdmi},
@code{arm10e},
@code{arm1020},
@code{arm1020t},
-@code{arm1020e},
+@code{arm1020e},
+@code{arm1022e},
+@code{arm1026ej-s},
+@code{fa606te} (Faraday FA606TE processor),
+@code{fa616te} (Faraday FA616TE processor),
+@code{fa626te} (Faraday FA626TE processor),
+@code{fmp626} (Faraday FMP626 processor),
+@code{fa726te} (Faraday FA726TE processor),
+@code{arm1136j-s},
+@code{arm1136jf-s},
+@code{arm1156t2-s},
+@code{arm1156t2f-s},
+@code{arm1176jz-s},
+@code{arm1176jzf-s},
+@code{mpcore},
+@code{mpcorenovfp},
+@code{cortex-a5},
+@code{cortex-a8},
+@code{cortex-a9},
+@code{cortex-a15},
+@code{cortex-r4},
+@code{cortex-r4f},
+@code{cortex-m4},
+@code{cortex-m3},
+@code{cortex-m1},
+@code{cortex-m0},
@code{ep9312} (ARM920 with Cirrus Maverick coprocessor),
@code{i80200} (Intel XScale processor)
@code{iwmmxt} (Intel(r) XScale processor with Wireless MMX(tm) technology coprocessor)
In addition to the basic instruction set, the assembler can be told to
accept various extension mnemonics that extend the processor using the
co-processor instruction space. For example, @code{-mcpu=arm920+maverick}
-is equivalent to specifying @code{-mcpu=ep9312}. The following extensions
-are currently supported:
-@code{+maverick}
-@code{+iwmmxt}
+is equivalent to specifying @code{-mcpu=ep9312}.
+
+Multiple extensions may be specified, separated by a @code{+}. The
+extensions should be specified in ascending alphabetical order.
+
+Some extensions may be restricted to particular architectures; this is
+documented in the list of extensions below.
+
+Extension mnemonics may also be removed from those the assembler accepts.
+This is done be prepending @code{no} to the option that adds the extension.
+Extensions that are removed should be listed after all extensions which have
+been added, again in ascending alphabetical order. For example,
+@code{-mcpu=ep9312+nomaverick} is equivalent to specifying @code{-mcpu=arm920}.
+
+
+The following extensions are currently supported:
+@code{idiv}, (Integer Divide Extensions for v7-A and v7-R architectures),
+@code{iwmmxt},
+@code{iwmmxt2},
+@code{maverick},
+@code{mp} (Multiprocessing Extensions for v7-A and v7-R architectures),
+@code{os} (Operating System for v6M architecture),
+@code{sec} (Security Extensions for v6K and v7-A architectures),
+@code{virt} (Virtualization Extensions for v7-A architecture, implies
+@code{idiv}),
and
-@code{+xscale}.
+@code{xscale}.
@cindex @code{-march=} command line option, ARM
@item -march=@var{architecture}[+@var{extension}@dots{}]
@code{armv5t},
@code{armv5txm},
@code{armv5te},
-@code{armv5texp}
+@code{armv5texp},
+@code{armv6},
+@code{armv6j},
+@code{armv6k},
+@code{armv6z},
+@code{armv6zk},
+@code{armv6-m},
+@code{armv6s-m},
+@code{armv7},
+@code{armv7-a},
+@code{armv7-r},
+@code{armv7-m},
+@code{armv7e-m},
@code{iwmmxt}
and
@code{xscale}.
@code{vfp10-r0},
@code{vfp9},
@code{vfpxd},
-@code{arm1020t}
+@code{vfpv2},
+@code{vfpv3},
+@code{vfpv3-fp16},
+@code{vfpv3-d16},
+@code{vfpv3-d16-fp16},
+@code{vfpv3xd},
+@code{vfpv3xd-d16},
+@code{vfpv4},
+@code{vfpv4-d16},
+@code{fpv4-sp-d16},
+@code{arm1020t},
+@code{arm1020e},
+@code{arm1136jf-s},
+@code{maverick},
+@code{neon},
and
-@code{arm1020e}.
+@code{neon-vfpv4}.
In addition to determining which instructions are assembled, this option
also affects the way in which the @code{.double} assembler directive behaves
This option specifies that the output generated by the assembler should
be marked as supporting interworking.
-@cindex @code{-mapcs} command line option, ARM
-@item -mapcs @code{[26|32]}
-This option specifies that the output generated by the assembler should
+@cindex @code{-mimplicit-it} command line option, ARM
+@item -mimplicit-it=never
+@itemx -mimplicit-it=always
+@itemx -mimplicit-it=arm
+@itemx -mimplicit-it=thumb
+The @code{-mimplicit-it} option controls the behavior of the assembler when
+conditional instructions are not enclosed in IT blocks.
+There are four possible behaviors.
+If @code{never} is specified, such constructs cause a warning in ARM
+code and an error in Thumb-2 code.
+If @code{always} is specified, such constructs are accepted in both
+ARM and Thumb-2 code, where the IT instruction is added implicitly.
+If @code{arm} is specified, such constructs are accepted in ARM code
+and cause an error in Thumb-2 code.
+If @code{thumb} is specified, such constructs cause a warning in ARM
+code and are accepted in Thumb-2 code. If you omit this option, the
+behavior is equivalent to @code{-mimplicit-it=arm}.
+
+@cindex @code{-mapcs-26} command line option, ARM
+@cindex @code{-mapcs-32} command line option, ARM
+@item -mapcs-26
+@itemx -mapcs-32
+These options specify that the output generated by the assembler should
be marked as supporting the indicated version of the Arm Procedure.
Calling Standard.
This indicates that the reentrant variant of the APCS should be used.
This variant supports position independent code.
+@cindex @code{-mfloat-abi=} command line option, ARM
+@item -mfloat-abi=@var{abi}
+This option specifies that the output generated by the assembler should be
+marked as using specified floating point ABI.
+The following values are recognized:
+@code{soft},
+@code{softfp}
+and
+@code{hard}.
+
+@cindex @code{-eabi=} command line option, ARM
+@item -meabi=@var{ver}
+This option specifies which EABI version the produced object files should
+conform to.
+The following values are recognized:
+@code{gnu},
+@code{4}
+and
+@code{5}.
+
@cindex @code{-EB} command line option, ARM
@item -EB
This option specifies that the output generated by the assembler should
This option specifies that the output of the assembler should be marked
as position-independent code (PIC).
-@cindex @code{-moabi} command line option, ARM
-@item -moabi
-This indicates that the code should be assembled using the old ARM ELF
-conventions, based on a beta release release of the ARM-ELF
-specifications, rather than the default conventions which are based on
-the final release of the ARM-ELF specifications.
+@cindex @code{--fix-v4bx} command line option, ARM
+@item --fix-v4bx
+Allow @code{BX} instructions in ARMv4 code. This is intended for use with
+the linker option of the same name.
+
+@cindex @code{-mwarn-deprecated} command line option, ARM
+@item -mwarn-deprecated
+@itemx -mno-warn-deprecated
+Enable or disable warnings about using deprecated options or
+features. The default is to warn.
@end table
@node ARM Syntax
@section Syntax
@menu
+* ARM-Instruction-Set:: Instruction Set
* ARM-Chars:: Special Characters
* ARM-Regs:: Register Names
+* ARM-Relocations:: Relocations
+* ARM-Neon-Alignment:: NEON Alignment Specifiers
@end menu
+@node ARM-Instruction-Set
+@subsection Instruction Set Syntax
+Two slightly different syntaxes are support for ARM and THUMB
+instructions. The default, @code{divided}, uses the old style where
+ARM and THUMB instructions had their own, separate syntaxes. The new,
+@code{unified} syntax, which can be selected via the @code{.syntax}
+directive, and has the following main features:
+
+@table @bullet
+@item
+Immediate operands do not require a @code{#} prefix.
+
+@item
+The @code{IT} instruction may appear, and if it does it is validated
+against subsequent conditional affixes. In ARM mode it does not
+generate machine code, in THUMB mode it does.
+
+@item
+For ARM instructions the conditional affixes always appear at the end
+of the instruction. For THUMB instructions conditional affixes can be
+used, but only inside the scope of an @code{IT} instruction.
+
+@item
+All of the instructions new to the V6T2 architecture (and later) are
+available. (Only a few such instructions can be written in the
+@code{divided} syntax).
+
+@item
+The @code{.N} and @code{.W} suffixes are recognized and honored.
+
+@item
+All instructions set the flags if and only if they have an @code{s}
+affix.
+@end table
+
@node ARM-Chars
@subsection Special Characters
@cindex line comment character, ARM
@cindex ARM line comment character
-The presence of a @samp{@@} on a line indicates the start of a comment
-that extends to the end of the current line. If a @samp{#} appears as
-the first character of a line, the whole line is treated as a comment.
+The presence of a @samp{@@} 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 could also be
+a logical line number directive (@pxref{Comments}) or a preprocessor
+control command (@pxref{Preprocessing}).
@cindex line separator, ARM
@cindex statement separator, ARM
@cindex register names, ARM
*TODO* Explain about ARM register naming, and the predefined names.
+@node ARM-Neon-Alignment
+@subsection NEON Alignment Specifiers
+
+@cindex alignment for NEON instructions
+Some NEON load/store instructions allow an optional address
+alignment qualifier.
+The ARM documentation specifies that this is indicated by
+@samp{@@ @var{align}}. However GAS already interprets
+the @samp{@@} character as a "line comment" start,
+so @samp{: @var{align}} is used instead. For example:
+
+@smallexample
+ vld1.8 @{q0@}, [r0, :128]
+@end smallexample
+
@node ARM Floating Point
@section Floating Point
@cindex ARM floating point (@sc{ieee})
The ARM family uses @sc{ieee} floating-point numbers.
+@node ARM-Relocations
+@subsection ARM relocation generation
+
+@cindex data relocations, ARM
+@cindex ARM data relocations
+Specific data relocations can be generated by putting the relocation name
+in parentheses after the symbol name. For example:
+
+@smallexample
+ .word foo(TARGET1)
+@end smallexample
+
+This will generate an @samp{R_ARM_TARGET1} relocation against the symbol
+@var{foo}.
+The following relocations are supported:
+@code{GOT},
+@code{GOTOFF},
+@code{TARGET1},
+@code{TARGET2},
+@code{SBREL},
+@code{TLSGD},
+@code{TLSLDM},
+@code{TLSLDO},
+@code{TLSDESC},
+@code{TLSCALL},
+@code{GOTTPOFF},
+@code{GOT_PREL}
+and
+@code{TPOFF}.
+
+For compatibility with older toolchains the assembler also accepts
+@code{(PLT)} after branch targets. This will generate the deprecated
+@samp{R_ARM_PLT32} relocation.
+
+@cindex MOVW and MOVT relocations, ARM
+Relocations for @samp{MOVW} and @samp{MOVT} instructions can be generated
+by prefixing the value with @samp{#:lower16:} and @samp{#:upper16}
+respectively. For example to load the 32-bit address of foo into r0:
+@smallexample
+ MOVW r0, #:lower16:foo
+ MOVT r0, #:upper16:foo
+@end smallexample
@node ARM Directives
@section ARM Machine Directives
@cindex ARM machine directives
@table @code
-@cindex @code{align} directive, ARM
+@c AAAAAAAAAAAAAAAAAAAAAAAAA
+
+@cindex @code{.2byte} directive, ARM
+@cindex @code{.4byte} directive, ARM
+@cindex @code{.8byte} directive, ARM
+@item .2byte @var{expression} [, @var{expression}]*
+@itemx .4byte @var{expression} [, @var{expression}]*
+@itemx .8byte @var{expression} [, @var{expression}]*
+These directives write 2, 4 or 8 byte values to the output section.
+
+@cindex @code{.align} directive, ARM
@item .align @var{expression} [, @var{expression}]
This is the generic @var{.align} directive. For the ARM however if the
first argument is zero (ie no alignment is needed) the assembler will
behave as if the argument had been 2 (ie pad to the next four byte
boundary). This is for compatibility with ARM's own assembler.
-@cindex @code{req} directive, ARM
-@item @var{name} .req @var{register name}
-This creates an alias for @var{register name} called @var{name}. For
-example:
+@cindex @code{.arch} directive, ARM
+@item .arch @var{name}
+Select the target architecture. Valid values for @var{name} are the same as
+for the @option{-march} commandline option.
-@smallexample
- foo .req r0
-@end smallexample
+Specifying @code{.arch} clears any previously selected architecture
+extensions.
-@cindex @code{unreq} directive, ARM
-@item .unreq @var{alias-name}
-This undefines a register alias which was previously defined using the
-@code{req} directive. For example:
+@cindex @code{.arch_extension} directive, ARM
+@item .arch_extension @var{name}
+Add or remove an architecture extension to the target architecture. Valid
+values for @var{name} are the same as those accepted as architectural
+extensions by the @option{-mcpu} commandline option.
-@smallexample
- foo .req r0
- .unreq foo
-@end smallexample
+@code{.arch_extension} may be used multiple times to add or remove extensions
+incrementally to the architecture being compiled for.
-An error occurs if the name is undefined. Note - this pseudo op can
-be used to delete builtin in register name aliases (eg 'r0'). This
-should only be done if it is really necessary.
+@cindex @code{.arm} directive, ARM
+@item .arm
+This performs the same action as @var{.code 32}.
+
+@anchor{arm_pad}
+@cindex @code{.pad} directive, ARM
+@item .pad #@var{count}
+Generate unwinder annotations for a stack adjustment of @var{count} bytes.
+A positive value indicates the function prologue allocated stack space by
+decrementing the stack pointer.
+
+@c BBBBBBBBBBBBBBBBBBBBBBBBBB
+
+@cindex @code{.bss} directive, ARM
+@item .bss
+This directive switches to the @code{.bss} section.
+
+@c CCCCCCCCCCCCCCCCCCCCCCCCCC
-@cindex @code{code} directive, ARM
+@cindex @code{.cantunwind} directive, ARM
+@item .cantunwind
+Prevents unwinding through the current function. No personality routine
+or exception table data is required or permitted.
+
+@cindex @code{.code} directive, ARM
@item .code @code{[16|32]}
This directive selects the instruction set being generated. The value 16
selects Thumb, with the value 32 selecting ARM.
-@cindex @code{thumb} directive, ARM
-@item .thumb
-This performs the same action as @var{.code 16}.
+@cindex @code{.cpu} directive, ARM
+@item .cpu @var{name}
+Select the target processor. Valid values for @var{name} are the same as
+for the @option{-mcpu} commandline option.
-@cindex @code{arm} directive, ARM
-@item .arm
-This performs the same action as @var{.code 32}.
+Specifying @code{.cpu} clears any previously selected architecture
+extensions.
-@cindex @code{force_thumb} directive, ARM
+@c DDDDDDDDDDDDDDDDDDDDDDDDDD
+
+@cindex @code{.dn} and @code{.qn} directives, ARM
+@item @var{name} .dn @var{register name} [@var{.type}] [[@var{index}]]
+@itemx @var{name} .qn @var{register name} [@var{.type}] [[@var{index}]]
+
+The @code{dn} and @code{qn} directives are used to create typed
+and/or indexed register aliases for use in Advanced SIMD Extension
+(Neon) instructions. The former should be used to create aliases
+of double-precision registers, and the latter to create aliases of
+quad-precision registers.
+
+If these directives are used to create typed aliases, those aliases can
+be used in Neon instructions instead of writing types after the mnemonic
+or after each operand. For example:
+
+@smallexample
+ x .dn d2.f32
+ y .dn d3.f32
+ z .dn d4.f32[1]
+ vmul x,y,z
+@end smallexample
+
+This is equivalent to writing the following:
+
+@smallexample
+ vmul.f32 d2,d3,d4[1]
+@end smallexample
+
+Aliases created using @code{dn} or @code{qn} can be destroyed using
+@code{unreq}.
+
+@c EEEEEEEEEEEEEEEEEEEEEEEEEE
+
+@cindex @code{.eabi_attribute} directive, ARM
+@item .eabi_attribute @var{tag}, @var{value}
+Set the EABI object attribute @var{tag} to @var{value}.
+
+The @var{tag} is either an attribute number, or one of the following:
+@code{Tag_CPU_raw_name}, @code{Tag_CPU_name}, @code{Tag_CPU_arch},
+@code{Tag_CPU_arch_profile}, @code{Tag_ARM_ISA_use},
+@code{Tag_THUMB_ISA_use}, @code{Tag_FP_arch}, @code{Tag_WMMX_arch},
+@code{Tag_Advanced_SIMD_arch}, @code{Tag_PCS_config},
+@code{Tag_ABI_PCS_R9_use}, @code{Tag_ABI_PCS_RW_data},
+@code{Tag_ABI_PCS_RO_data}, @code{Tag_ABI_PCS_GOT_use},
+@code{Tag_ABI_PCS_wchar_t}, @code{Tag_ABI_FP_rounding},
+@code{Tag_ABI_FP_denormal}, @code{Tag_ABI_FP_exceptions},
+@code{Tag_ABI_FP_user_exceptions}, @code{Tag_ABI_FP_number_model},
+@code{Tag_ABI_align_needed}, @code{Tag_ABI_align_preserved},
+@code{Tag_ABI_enum_size}, @code{Tag_ABI_HardFP_use},
+@code{Tag_ABI_VFP_args}, @code{Tag_ABI_WMMX_args},
+@code{Tag_ABI_optimization_goals}, @code{Tag_ABI_FP_optimization_goals},
+@code{Tag_compatibility}, @code{Tag_CPU_unaligned_access},
+@code{Tag_FP_HP_extension}, @code{Tag_ABI_FP_16bit_format},
+@code{Tag_MPextension_use}, @code{Tag_DIV_use},
+@code{Tag_nodefaults}, @code{Tag_also_compatible_with},
+@code{Tag_conformance}, @code{Tag_T2EE_use},
+@code{Tag_Virtualization_use}
+
+The @var{value} is either a @code{number}, @code{"string"}, or
+@code{number, "string"} depending on the tag.
+
+Note - the following legacy values are also accepted by @var{tag}:
+@code{Tag_VFP_arch}, @code{Tag_ABI_align8_needed},
+@code{Tag_ABI_align8_preserved}, @code{Tag_VFP_HP_extension},
+
+@cindex @code{.even} directive, ARM
+@item .even
+This directive aligns to an even-numbered address.
+
+@cindex @code{.extend} directive, ARM
+@cindex @code{.ldouble} directive, ARM
+@item .extend @var{expression} [, @var{expression}]*
+@itemx .ldouble @var{expression} [, @var{expression}]*
+These directives write 12byte long double floating-point values to the
+output section. These are not compatible with current ARM processors
+or ABIs.
+
+@c FFFFFFFFFFFFFFFFFFFFFFFFFF
+
+@anchor{arm_fnend}
+@cindex @code{.fnend} directive, ARM
+@item .fnend
+Marks the end of a function with an unwind table entry. The unwind index
+table entry is created when this directive is processed.
+
+If no personality routine has been specified then standard personality
+routine 0 or 1 will be used, depending on the number of unwind opcodes
+required.
+
+@anchor{arm_fnstart}
+@cindex @code{.fnstart} directive, ARM
+@item .fnstart
+Marks the start of a function with an unwind table entry.
+
+@cindex @code{.force_thumb} directive, ARM
@item .force_thumb
This directive forces the selection of Thumb instructions, even if the
target processor does not support those instructions
-@cindex @code{thumb_func} directive, ARM
-@item .thumb_func
-This directive specifies that the following symbol is the name of a
-Thumb encoded function. This information is necessary in order to allow
-the assembler and linker to generate correct code for interworking
-between Arm and Thumb instructions and should be used even if
-interworking is not going to be performed. The presence of this
-directive also implies @code{.thumb}
+@cindex @code{.fpu} directive, ARM
+@item .fpu @var{name}
+Select the floating-point unit to assemble for. Valid values for @var{name}
+are the same as for the @option{-mfpu} commandline option.
-@cindex @code{thumb_set} directive, ARM
-@item .thumb_set
-This performs the equivalent of a @code{.set} directive in that it
-creates a symbol which is an alias for another symbol (possibly not yet
-defined). This directive also has the added property in that it marks
-the aliased symbol as being a thumb function entry point, in the same
-way that the @code{.thumb_func} directive does.
+@c GGGGGGGGGGGGGGGGGGGGGGGGGG
+@c HHHHHHHHHHHHHHHHHHHHHHHHHH
+
+@cindex @code{.handlerdata} directive, ARM
+@item .handlerdata
+Marks the end of the current function, and the start of the exception table
+entry for that function. Anything between this directive and the
+@code{.fnend} directive will be added to the exception table entry.
+
+Must be preceded by a @code{.personality} or @code{.personalityindex}
+directive.
+
+@c IIIIIIIIIIIIIIIIIIIIIIIIII
+
+@cindex @code{.inst} directive, ARM
+@item .inst @var{opcode} [ , @dots{} ]
+@itemx .inst.n @var{opcode} [ , @dots{} ]
+@itemx .inst.w @var{opcode} [ , @dots{} ]
+Generates the instruction corresponding to the numerical value @var{opcode}.
+@code{.inst.n} and @code{.inst.w} allow the Thumb instruction size to be
+specified explicitly, overriding the normal encoding rules.
+
+@c JJJJJJJJJJJJJJJJJJJJJJJJJJ
+@c KKKKKKKKKKKKKKKKKKKKKKKKKK
+@c LLLLLLLLLLLLLLLLLLLLLLLLLL
+
+@item .ldouble @var{expression} [, @var{expression}]*
+See @code{.extend}.
@cindex @code{.ltorg} directive, ARM
@item .ltorg
pool any time a section change occurred. This is no longer done, since
it prevents accurate control of the placement of literal pools.
+@c MMMMMMMMMMMMMMMMMMMMMMMMMM
+
+@cindex @code{.movsp} directive, ARM
+@item .movsp @var{reg} [, #@var{offset}]
+Tell the unwinder that @var{reg} contains an offset from the current
+stack pointer. If @var{offset} is not specified then it is assumed to be
+zero.
+
+@c NNNNNNNNNNNNNNNNNNNNNNNNNN
+@c OOOOOOOOOOOOOOOOOOOOOOOOOO
+
+@cindex @code{.object_arch} directive, ARM
+@item .object_arch @var{name}
+Override the architecture recorded in the EABI object attribute section.
+Valid values for @var{name} are the same as for the @code{.arch} directive.
+Typically this is useful when code uses runtime detection of CPU features.
+
+@c PPPPPPPPPPPPPPPPPPPPPPPPPP
+
+@cindex @code{.packed} directive, ARM
+@item .packed @var{expression} [, @var{expression}]*
+This directive writes 12-byte packed floating-point values to the
+output section. These are not compatible with current ARM processors
+or ABIs.
+
+@cindex @code{.pad} directive, ARM
+@item .pad #@var{count}
+Generate unwinder annotations for a stack adjustment of @var{count} bytes.
+A positive value indicates the function prologue allocated stack space by
+decrementing the stack pointer.
+
+@cindex @code{.personality} directive, ARM
+@item .personality @var{name}
+Sets the personality routine for the current function to @var{name}.
+
+@cindex @code{.personalityindex} directive, ARM
+@item .personalityindex @var{index}
+Sets the personality routine for the current function to the EABI standard
+routine number @var{index}
+
@cindex @code{.pool} directive, ARM
@item .pool
This is a synonym for .ltorg.
+@c QQQQQQQQQQQQQQQQQQQQQQQQQQ
+@c RRRRRRRRRRRRRRRRRRRRRRRRRR
+
+@cindex @code{.req} directive, ARM
+@item @var{name} .req @var{register name}
+This creates an alias for @var{register name} called @var{name}. For
+example:
+
+@smallexample
+ foo .req r0
+@end smallexample
+
+@c SSSSSSSSSSSSSSSSSSSSSSSSSS
+
+@anchor{arm_save}
+@cindex @code{.save} directive, ARM
+@item .save @var{reglist}
+Generate unwinder annotations to restore the registers in @var{reglist}.
+The format of @var{reglist} is the same as the corresponding store-multiple
+instruction.
+
+@smallexample
+@exdent @emph{core registers}
+ .save @{r4, r5, r6, lr@}
+ stmfd sp!, @{r4, r5, r6, lr@}
+@exdent @emph{FPA registers}
+ .save f4, 2
+ sfmfd f4, 2, [sp]!
+@exdent @emph{VFP registers}
+ .save @{d8, d9, d10@}
+ fstmdx sp!, @{d8, d9, d10@}
+@exdent @emph{iWMMXt registers}
+ .save @{wr10, wr11@}
+ wstrd wr11, [sp, #-8]!
+ wstrd wr10, [sp, #-8]!
+or
+ .save wr11
+ wstrd wr11, [sp, #-8]!
+ .save wr10
+ wstrd wr10, [sp, #-8]!
+@end smallexample
+
+@anchor{arm_setfp}
+@cindex @code{.setfp} directive, ARM
+@item .setfp @var{fpreg}, @var{spreg} [, #@var{offset}]
+Make all unwinder annotations relative to a frame pointer. Without this
+the unwinder will use offsets from the stack pointer.
+
+The syntax of this directive is the same as the @code{add} or @code{mov}
+instruction used to set the frame pointer. @var{spreg} must be either
+@code{sp} or mentioned in a previous @code{.movsp} directive.
+
+@smallexample
+.movsp ip
+mov ip, sp
+@dots{}
+.setfp fp, ip, #4
+add fp, ip, #4
+@end smallexample
+
+@cindex @code{.secrel32} directive, ARM
+@item .secrel32 @var{expression} [, @var{expression}]*
+This directive emits relocations that evaluate to the section-relative
+offset of each expression's symbol. This directive is only supported
+for PE targets.
+
+@cindex @code{.syntax} directive, ARM
+@item .syntax [@code{unified} | @code{divided}]
+This directive sets the Instruction Set Syntax as described in the
+@ref{ARM-Instruction-Set} section.
+
+@c TTTTTTTTTTTTTTTTTTTTTTTTTT
+
+@cindex @code{.thumb} directive, ARM
+@item .thumb
+This performs the same action as @var{.code 16}.
+
+@cindex @code{.thumb_func} directive, ARM
+@item .thumb_func
+This directive specifies that the following symbol is the name of a
+Thumb encoded function. This information is necessary in order to allow
+the assembler and linker to generate correct code for interworking
+between Arm and Thumb instructions and should be used even if
+interworking is not going to be performed. The presence of this
+directive also implies @code{.thumb}
+
+This directive is not neccessary when generating EABI objects. On these
+targets the encoding is implicit when generating Thumb code.
+
+@cindex @code{.thumb_set} directive, ARM
+@item .thumb_set
+This performs the equivalent of a @code{.set} directive in that it
+creates a symbol which is an alias for another symbol (possibly not yet
+defined). This directive also has the added property in that it marks
+the aliased symbol as being a thumb function entry point, in the same
+way that the @code{.thumb_func} directive does.
+
+@cindex @code{.tlsdescseq} directive, ARM
+@item .tlsdescseq @var{tls-variable}
+This directive is used to annotate parts of an inlined TLS descriptor
+trampoline. Normally the trampoline is provided by the linker, and
+this directive is not needed.
+
+@c UUUUUUUUUUUUUUUUUUUUUUUUUU
+
+@cindex @code{.unreq} directive, ARM
+@item .unreq @var{alias-name}
+This undefines a register alias which was previously defined using the
+@code{req}, @code{dn} or @code{qn} directives. For example:
+
+@smallexample
+ foo .req r0
+ .unreq foo
+@end smallexample
+
+An error occurs if the name is undefined. Note - this pseudo op can
+be used to delete builtin in register name aliases (eg 'r0'). This
+should only be done if it is really necessary.
+
+@cindex @code{.unwind_raw} directive, ARM
+@item .unwind_raw @var{offset}, @var{byte1}, @dots{}
+Insert one of more arbitary unwind opcode bytes, which are known to adjust
+the stack pointer by @var{offset} bytes.
+
+For example @code{.unwind_raw 4, 0xb1, 0x01} is equivalent to
+@code{.save @{r0@}}
+
+@c VVVVVVVVVVVVVVVVVVVVVVVVVV
+
+@cindex @code{.vsave} directive, ARM
+@item .vsave @var{vfp-reglist}
+Generate unwinder annotations to restore the VFP registers in @var{vfp-reglist}
+using FLDMD. Also works for VFPv3 registers
+that are to be restored using VLDM.
+The format of @var{vfp-reglist} is the same as the corresponding store-multiple
+instruction.
+
+@smallexample
+@exdent @emph{VFP registers}
+ .vsave @{d8, d9, d10@}
+ fstmdd sp!, @{d8, d9, d10@}
+@exdent @emph{VFPv3 registers}
+ .vsave @{d15, d16, d17@}
+ vstm sp!, @{d15, d16, d17@}
+@end smallexample
+
+Since FLDMX and FSTMX are now deprecated, this directive should be
+used in favour of @code{.save} for saving VFP registers for ARMv6 and above.
+
+@c WWWWWWWWWWWWWWWWWWWWWWWWWW
+@c XXXXXXXXXXXXXXXXXXXXXXXXXX
+@c YYYYYYYYYYYYYYYYYYYYYYYYYY
+@c ZZZZZZZZZZZZZZZZZZZZZZZZZZ
+
@end table
@node ARM Opcodes
Software Development Toolkit Reference Manual}, Advanced RISC Machines
Ltd.
+@node ARM Mapping Symbols
+@section Mapping Symbols
+
+The ARM ELF specification requires that special symbols be inserted
+into object files to mark certain features:
+
+@table @code
+
+@cindex @code{$a}
+@item $a
+At the start of a region of code containing ARM instructions.
+
+@cindex @code{$t}
+@item $t
+At the start of a region of code containing THUMB instructions.
+
+@cindex @code{$d}
+@item $d
+At the start of a region of data.
+
+@end table
+
+The assembler will automatically insert these symbols for you - there
+is no need to code them yourself. Support for tagging symbols ($b,
+$f, $p and $m) which is also mentioned in the current ARM ELF
+specification is not implemented. This is because they have been
+dropped from the new EABI and so tools cannot rely upon their
+presence.
+
+@node ARM Unwinding Tutorial
+@section Unwinding
+
+The ABI for the ARM Architecture specifies a standard format for
+exception unwind information. This information is used when an
+exception is thrown to determine where control should be transferred.
+In particular, the unwind information is used to determine which
+function called the function that threw the exception, and which
+function called that one, and so forth. This information is also used
+to restore the values of callee-saved registers in the function
+catching the exception.
+
+If you are writing functions in assembly code, and those functions
+call other functions that throw exceptions, you must use assembly
+pseudo ops to ensure that appropriate exception unwind information is
+generated. Otherwise, if one of the functions called by your assembly
+code throws an exception, the run-time library will be unable to
+unwind the stack through your assembly code and your program will not
+behave correctly.
+
+To illustrate the use of these pseudo ops, we will examine the code
+that G++ generates for the following C++ input:
+
+@verbatim
+void callee (int *);
+
+int
+caller ()
+{
+ int i;
+ callee (&i);
+ return i;
+}
+@end verbatim
+
+This example does not show how to throw or catch an exception from
+assembly code. That is a much more complex operation and should
+always be done in a high-level language, such as C++, that directly
+supports exceptions.
+
+The code generated by one particular version of G++ when compiling the
+example above is:
+
+@verbatim
+_Z6callerv:
+ .fnstart
+.LFB2:
+ @ Function supports interworking.
+ @ args = 0, pretend = 0, frame = 8
+ @ frame_needed = 1, uses_anonymous_args = 0
+ stmfd sp!, {fp, lr}
+ .save {fp, lr}
+.LCFI0:
+ .setfp fp, sp, #4
+ add fp, sp, #4
+.LCFI1:
+ .pad #8
+ sub sp, sp, #8
+.LCFI2:
+ sub r3, fp, #8
+ mov r0, r3
+ bl _Z6calleePi
+ ldr r3, [fp, #-8]
+ mov r0, r3
+ sub sp, fp, #4
+ ldmfd sp!, {fp, lr}
+ bx lr
+.LFE2:
+ .fnend
+@end verbatim
+
+Of course, the sequence of instructions varies based on the options
+you pass to GCC and on the version of GCC in use. The exact
+instructions are not important since we are focusing on the pseudo ops
+that are used to generate unwind information.
+
+An important assumption made by the unwinder is that the stack frame
+does not change during the body of the function. In particular, since
+we assume that the assembly code does not itself throw an exception,
+the only point where an exception can be thrown is from a call, such
+as the @code{bl} instruction above. At each call site, the same saved
+registers (including @code{lr}, which indicates the return address)
+must be located in the same locations relative to the frame pointer.
+
+The @code{.fnstart} (@pxref{arm_fnstart,,.fnstart pseudo op}) pseudo
+op appears immediately before the first instruction of the function
+while the @code{.fnend} (@pxref{arm_fnend,,.fnend pseudo op}) pseudo
+op appears immediately after the last instruction of the function.
+These pseudo ops specify the range of the function.
+
+Only the order of the other pseudos ops (e.g., @code{.setfp} or
+@code{.pad}) matters; their exact locations are irrelevant. In the
+example above, the compiler emits the pseudo ops with particular
+instructions. That makes it easier to understand the code, but it is
+not required for correctness. It would work just as well to emit all
+of the pseudo ops other than @code{.fnend} in the same order, but
+immediately after @code{.fnstart}.
+
+The @code{.save} (@pxref{arm_save,,.save pseudo op}) pseudo op
+indicates registers that have been saved to the stack so that they can
+be restored before the function returns. The argument to the
+@code{.save} pseudo op is a list of registers to save. If a register
+is ``callee-saved'' (as specified by the ABI) and is modified by the
+function you are writing, then your code must save the value before it
+is modified and restore the original value before the function
+returns. If an exception is thrown, the run-time library restores the
+values of these registers from their locations on the stack before
+returning control to the exception handler. (Of course, if an
+exception is not thrown, the function that contains the @code{.save}
+pseudo op restores these registers in the function epilogue, as is
+done with the @code{ldmfd} instruction above.)
+
+You do not have to save callee-saved registers at the very beginning
+of the function and you do not need to use the @code{.save} pseudo op
+immediately following the point at which the registers are saved.
+However, if you modify a callee-saved register, you must save it on
+the stack before modifying it and before calling any functions which
+might throw an exception. And, you must use the @code{.save} pseudo
+op to indicate that you have done so.
+
+The @code{.pad} (@pxref{arm_pad,,.pad}) pseudo op indicates a
+modification of the stack pointer that does not save any registers.
+The argument is the number of bytes (in decimal) that are subtracted
+from the stack pointer. (On ARM CPUs, the stack grows downwards, so
+subtracting from the stack pointer increases the size of the stack.)
+
+The @code{.setfp} (@pxref{arm_setfp,,.setfp pseudo op}) pseudo op
+indicates the register that contains the frame pointer. The first
+argument is the register that is set, which is typically @code{fp}.
+The second argument indicates the register from which the frame
+pointer takes its value. The third argument, if present, is the value
+(in decimal) added to the register specified by the second argument to
+compute the value of the frame pointer. You should not modify the
+frame pointer in the body of the function.
+
+If you do not use a frame pointer, then you should not use the
+@code{.setfp} pseudo op. If you do not use a frame pointer, then you
+should avoid modifying the stack pointer outside of the function
+prologue. Otherwise, the run-time library will be unable to find
+saved registers when it is unwinding the stack.
+
+The pseudo ops described above are sufficient for writing assembly
+code that calls functions which may throw exceptions. If you need to
+know more about the object-file format used to represent unwind
+information, you may consult the @cite{Exception Handling ABI for the
+ARM Architecture} available from @uref{http://infocenter.arm.com}.
projects / deliverable / binutils-gdb.git / blobdiff