* doc/as.texinfo (Object Attributes): New chapter.
(Pseudo Ops): Document .gnu_attribute. (LNS directives): Correct .loc_mark_labels documentation.
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Daniel Jacobowitz
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2007-10-12 Daniel Jacobowitz <dan@codesourcery.com>
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* doc/as.texinfo (Object Attributes): New chapter.
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(Pseudo Ops): Document .gnu_attribute.
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(LNS directives): Correct .loc_mark_labels documentation.
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2007-10-11 Nick Clifton <nickc@redhat.com>
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* config/obj-elf.c (obj_elf_section): When pushing a section, if
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@ -189,6 +189,9 @@ section entitled ``GNU Free Documentation License''.
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* Symbols:: Symbols
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* Expressions:: Expressions
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* Pseudo Ops:: Assembler Directives
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@ifset ELF
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* Object Attributes:: Object Attributes
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@end ifset
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* Machine Dependencies:: Machine Dependent Features
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* Reporting Bugs:: Reporting Bugs
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* Acknowledgements:: Who Did What
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@ -3828,6 +3831,7 @@ Some machine configurations provide additional directives.
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* Func:: @code{.func}
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* Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
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@ifset ELF
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* Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
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* Hidden:: @code{.hidden @var{names}}
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@end ifset
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@ -4254,9 +4258,9 @@ state machine to @var{value}, which must be an unsigned integer.
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@end table
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@section @code{.loc_mark_blocks @var{enable}}
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@cindex @code{loc_mark_blocks} directive
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The @code{.loc_mark_blocks} directive makes the assembler emit an entry
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@section @code{.loc_mark_labels @var{enable}}
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@cindex @code{loc_mark_labels} directive
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The @code{.loc_mark_labels} directive makes the assembler emit an entry
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to the @code{.debug_line} line number matrix with the @code{basic_block}
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register in the state machine set whenever a code label is seen.
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The @var{enable} argument should be either 1 or 0, to enable or disable
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@ -4582,6 +4586,10 @@ partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
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@end ifset
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@ifset ELF
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@node Gnu_attribute
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@section @code{.gnu_attribute @var{tag},@var{value}}
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Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
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@node Hidden
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@section @code{.hidden @var{names}}
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@ -6393,6 +6401,140 @@ They are included for compatibility with older assemblers.
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@item .line
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@end table
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@ifset ELF
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@node Object Attributes
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@chapter Object Attributes
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@cindex object attributes
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@command{@value{AS}} assembles source files written for a specific architecture
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into object files for that architecture. But not all object files are alike.
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Many architectures support incompatible variations. For instance, floating
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point arguments might be passed in floating point registers if the object file
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requires hardware floating point support---or floating point arguments might be
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passed in integer registers if the object file supports processors with no
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hardware floating point unit. Or, if two objects are built for different
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generations of the same architecture, the combination may require the
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newer generation at run-time.
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This information is useful during and after linking. At link time,
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@command{@value{LD}} can warn about incompatible object files. After link
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time, tools like @command{gdb} can use it to process the linked file
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correctly.
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Compatibility information is recorded as a series of object attributes. Each
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attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
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string, and indicates who sets the meaning of the tag. The tag is an integer,
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and indicates what property the attribute describes. The value may be a string
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or an integer, and indicates how the property affects this object. Missing
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attributes are the same as attributes with a zero value or empty string value.
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Object attributes were developed as part of the ABI for the ARM Architecture.
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The file format is documented in @cite{ELF for the ARM Architecture}.
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@menu
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* GNU Object Attributes:: @sc{gnu} Object Attributes
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* Defining New Object Attributes:: Defining New Object Attributes
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@end menu
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@node GNU Object Attributes
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@section @sc{gnu} Object Attributes
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The @code{.gnu_attribute} directive records an object attribute
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with vendor @samp{gnu}.
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Except for @samp{Tag_compatibility}, which has both an integer and a string for
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its value, @sc{gnu} attributes have a string value if the tag number is odd and
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an integer value if the tag number is even. The second bit (@code{@var{tag} &
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2} is set for architecture-independent attributes and clear for
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architecture-dependent ones.
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@subsection Common @sc{gnu} attributes
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These attributes are valid on all architectures.
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@table @r
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@item Tag_compatibility (32)
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The compatibility attribute takes an integer flag value and a vendor name. If
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the flag value is 0, the file is compatible with other toolchains. If it is 1,
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then the file is only compatible with the named toolchain. If it is greater
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than 1, the file can only be processed by other toolchains under some private
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arrangement indicated by the flag value and the vendor name.
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@end table
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@subsection MIPS Attributes
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@table @r
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@item Tag_GNU_MIPS_ABI_FP (4)
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The floating-point ABI used by this object file. The value will be:
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@itemize @bullet
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@item
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0 for files not affected by the floating-point ABI.
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@item
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1 for files using the hardware floating-point with a standard double-precision
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FPU.
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@item
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2 for files using the hardware floating-point ABI with a single-precision FPU.
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@item
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3 for files using the software floating-point ABI.
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@end itemize
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@end table
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@subsection PowerPC Attributes
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@table @r
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@item Tag_GNU_Power_ABI_FP (4)
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The floating-point ABI used by this object file. The value will be:
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@itemize @bullet
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@item
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0 for files not affected by the floating-point ABI.
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@item
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1 for files using the hardware floating-point ABI.
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@item
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2 for files using the software floating-point ABI.
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@end itemize
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@item Tag_GNU_Power_ABI_Vector (8)
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The vector ABI used by this object file. The value will be:
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@itemize @bullet
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@item
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0 for files not affected by the vector ABI.
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@item
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1 for files using general purpose registers to pass vectors.
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@item
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2 for files using AltiVec registers to pass vectors.
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@item
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3 for files using SPE registers to pass vectors.
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@end itemize
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@end table
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@node Defining New Object Attributes
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@section Defining New Object Attributes
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If you want to define a new @sc{gnu} object attribute, here are the places you
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will need to modify. New attributes should be discussed on the @samp{binutils}
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mailing list.
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@itemize @bullet
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@item
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This manual, which is the official register of attributes.
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@item
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The header for your architecture @file{include/elf}, to define the tag.
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@item
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The @file{bfd} support file for your architecture, to merge the attribute
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and issue any appropriate link warnings.
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@item
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Test cases in @file{ld/testsuite} for merging and link warnings.
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@item
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@file{binutils/readelf.c} to display your attribute.
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@item
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GCC, if you want the compiler to mark the attribute automatically.
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@end itemize
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@end ifset
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@ifset GENERIC
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@node Machine Dependencies
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@chapter Machine Dependent Features
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