extend.texi (Common Function Attributes): Move to correct alphabetization of table.
2016-01-01 Sandra Loosemore <sandra@codesourcery.com> gcc/ * doc/extend.texi (Common Function Attributes) <noplt>: Move to correct alphabetization of table. Copy-edit and correct markup. <stack_protect>: Likewise. <target_clones>: Likewise. <simd>: Likewise. * doc/invoke.texi (Optimize Options) <-fstack-protector-explicit>: Correct punctuation. (Code Gen Options) <-fno-plt>: Copy-edit. From-SVN: r232030
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Sandra Loosemore
Sandra Loosemore
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@ -1,3 +1,15 @@
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2016-01-01 Sandra Loosemore <sandra@codesourcery.com>
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* doc/extend.texi (Common Function Attributes) <noplt>: Move
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to correct alphabetization of table. Copy-edit and correct
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markup.
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<stack_protect>: Likewise.
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<target_clones>: Likewise.
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<simd>: Likewise.
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* doc/invoke.texi (Optimize Options) <-fstack-protector-explicit>:
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Correct punctuation.
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(Code Gen Options) <-fno-plt>: Copy-edit.
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2016-01-01 Bernd Edlinger <bernd.edlinger@hotmail.de>
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PR target/68917
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@ -2932,6 +2932,36 @@ my_memcpy (void *dest, const void *src, size_t len)
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__attribute__((nonnull));
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@end smallexample
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@item noplt
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@cindex @code{noplt} function attribute
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The @code{noplt} attribute is the counterpart to option @option{-fno-plt}.
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Calls to functions marked with this attribute in position-independent code
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do not use the PLT.
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@smallexample
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@group
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/* Externally defined function foo. */
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int foo () __attribute__ ((noplt));
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int
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main (/* @r{@dots{}} */)
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@{
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/* @r{@dots{}} */
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foo ();
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/* @r{@dots{}} */
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@}
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@end group
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@end smallexample
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The @code{noplt} attribute on function @code{foo}
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tells the compiler to assume that
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the function @code{foo} is externally defined and that the call to
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@code{foo} must avoid the PLT
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in position-independent code.
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In position-dependent code, a few targets also convert calls to
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functions that are marked to not use the PLT to use the GOT instead.
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@item noreturn
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@cindex @code{noreturn} function attribute
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@cindex functions that never return
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@ -2977,35 +3007,6 @@ the standard C library can be guaranteed not to throw an exception
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with the notable exceptions of @code{qsort} and @code{bsearch} that
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take function pointer arguments.
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@item noplt
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@cindex @code{noplt} function attribute
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The @code{noplt} attribute is the counterpart to option @option{-fno-plt} and
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does not use PLT for calls to functions marked with this attribute in position
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independent code.
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@smallexample
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@group
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/* Externally defined function foo. */
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int foo () __attribute__ ((noplt));
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int
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main (/* @r{@dots{}} */)
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@{
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/* @r{@dots{}} */
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foo ();
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/* @r{@dots{}} */
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@}
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@end group
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@end smallexample
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The @code{noplt} attribute on function foo tells the compiler to assume that
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the function foo is externally defined and the call to foo must avoid the PLT
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in position independent code.
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Additionally, a few targets also convert calls to those functions that are
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marked to not use the PLT to use the GOT instead for non-position independent
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code.
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@item optimize
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@cindex @code{optimize} function attribute
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The @code{optimize} attribute is used to specify that a function is to
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@ -3120,44 +3121,35 @@ with a copy that redefines NULL appropriately.
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The warnings for missing or incorrect sentinels are enabled with
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@option{-Wformat}.
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@item stack_protect
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@cindex @code{stack_protect} function attribute
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This function attribute make a stack protection of the function if
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flags @option{fstack-protector} or @option{fstack-protector-strong}
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or @option{fstack-protector-explicit} are set.
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@item target_clones (@var{options})
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@cindex @code{target_clones} function attribute
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The @code{target_clones} attribute is used to specify that a function is to
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be cloned into multiple versions compiled with different target options
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than specified on the command line. The supported options and restrictions
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are the same as for @code{target} attribute.
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For instance on an x86, you could compile a function with
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@code{target_clones("sse4.1,avx")}. It will create 2 function clones,
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one compiled with @option{-msse4.1} and another with @option{-mavx}.
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At the function call it will create resolver @code{ifunc}, that will
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dynamically call a clone suitable for current architecture.
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@item simd
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@itemx simd("@var{mask}")
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@cindex @code{simd} function attribute.
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@cindex @code{simd} function attribute
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This attribute enables creation of one or more function versions that
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can process multiple arguments using SIMD instructions from a
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single invocation. Specifying this attribute allows compiler to
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assume that such versions are available at link time (provided
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in the same or another translation unit). Generated versions are
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target dependent and described in corresponding Vector ABI document. For
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target-dependent and described in the corresponding Vector ABI document. For
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x86_64 target this document can be found
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@w{@uref{https://sourceware.org/glibc/wiki/libmvec?action=AttachFile&do=view&target=VectorABI.txt,here}}.
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The optional argument @var{mask} may have the value
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@code{notinbranch} or @code{inbranch},
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and instructs the compiler to generate non-masked or masked
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clones correspondingly. By default, all clones are generated.
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The attribute should not be used together with Cilk Plus @code{vector}
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attribute on the same function.
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If the attribute is specified and @code{#pragma omp declare simd}
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present on a declaration and @code{-fopenmp} or @code{-fopenmp-simd}
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If the attribute is specified and @code{#pragma omp declare simd} is
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present on a declaration and the @option{-fopenmp} or @option{-fopenmp-simd}
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switch is specified, then the attribute is ignored.
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The optional argument @var{mask} may have "notinbranch" or "inbranch"
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value and instructs the compiler to generate non-masked or masked
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clones correspondingly. By default, all clones are generated.
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@item stack_protect
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@cindex @code{stack_protect} function attribute
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This attribute adds stack protection code to the function if
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flags @option{-fstack-protector}, @option{-fstack-protector-strong}
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or @option{-fstack-protector-explicit} are set.
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@item target (@var{options})
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@cindex @code{target} function attribute
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@ -3196,6 +3188,19 @@ Function Attributes}, @ref{PowerPC Function Attributes},
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@ref{ARM Function Attributes},and @ref{Nios II Function Attributes},
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for details.
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@item target_clones (@var{options})
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@cindex @code{target_clones} function attribute
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The @code{target_clones} attribute is used to specify that a function
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be cloned into multiple versions compiled with different target options
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than specified on the command line. The supported options and restrictions
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are the same as for @code{target} attribute.
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For instance, on an x86, you could compile a function with
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@code{target_clones("sse4.1,avx")}. GCC creates two function clones,
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one compiled with @option{-msse4.1} and another with @option{-mavx}.
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It also creates a resolver function (see the @code{ifunc} attribute
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above) that dynamically selects a clone suitable for current architecture.
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@item unused
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@cindex @code{unused} function attribute
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This attribute, attached to a function, means that the function is meant
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@ -10284,7 +10284,7 @@ references to local frame addresses.
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@item -fstack-protector-explicit
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@opindex fstack-protector-explicit
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Like @option{-fstack-protector} but only protects those functions which
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have the @code{stack_protect} attribute
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have the @code{stack_protect} attribute.
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@item -fstdarg-opt
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@opindex fstdarg-opt
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@ -24418,21 +24418,20 @@ for @option{-fpie} and 2 for @option{-fPIE}.
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@item -fno-plt
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@opindex fno-plt
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Do not use PLT for external function calls in position-independent code.
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Instead, load callee address at call site from GOT and branch to it.
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Do not use the PLT for external function calls in position-independent code.
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Instead, load the callee address at call sites from the GOT and branch to it.
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This leads to more efficient code by eliminating PLT stubs and exposing
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GOT load to optimizations. On architectures such as 32-bit x86 where
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PLT stubs expect GOT pointer in a specific register, this gives more
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register allocation freedom to the compiler. Lazy binding requires PLT:
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GOT loads to optimizations. On architectures such as 32-bit x86 where
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PLT stubs expect the GOT pointer in a specific register, this gives more
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register allocation freedom to the compiler.
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Lazy binding requires use of the PLT;
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with @option{-fno-plt} all external symbols are resolved at load time.
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Alternatively, function attribute @code{noplt} can be used to avoid PLT
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for calls to specific external functions by marking those functions with
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this attribute.
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Alternatively, the function attribute @code{noplt} can be used to avoid calls
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through the PLT for specific external functions.
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Additionally, a few targets also convert calls to those functions that are
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marked to not use the PLT to use the GOT instead for non-position independent
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code.
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In position-dependent code, a few targets also convert calls to
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functions that are marked to not use the PLT to use the GOT instead.
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@item -fno-jump-tables
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@opindex fno-jump-tables
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