@node ax_gcc_builtin
@unnumberedsec ax_gcc_builtin

@majorheading Synopsis

@smallexample
AX_GCC_BUILTIN(BUILTIN)
@end smallexample

@majorheading Description

This macro checks if the compiler supports one of GCC's built-in
functions; many other compilers also provide those same built-ins.

The BUILTIN parameter is the name of the built-in function.

If BUILTIN is supported define HAVE_<BUILTIN>. Keep in mind that since
builtins usually start with two underscores they will be copied over
into the HAVE_<BUILTIN> definition (e.g. HAVE___BUILTIN_EXPECT for
__builtin_expect()).

The macro caches its result in the ax_cv_have_<BUILTIN> variable (e.g.
ax_cv_have___builtin_expect).

The macro currently supports the following built-in functions:

@smallexample
 __builtin_assume_aligned
 __builtin_bswap16
 __builtin_bswap32
 __builtin_bswap64
 __builtin_choose_expr
 __builtin___clear_cache
 __builtin_clrsb
 __builtin_clrsbl
 __builtin_clrsbll
 __builtin_clz
 __builtin_clzl
 __builtin_clzll
 __builtin_complex
 __builtin_constant_p
 __builtin_cpu_init
 __builtin_cpu_is
 __builtin_cpu_supports
 __builtin_ctz
 __builtin_ctzl
 __builtin_ctzll
 __builtin_expect
 __builtin_ffs
 __builtin_ffsl
 __builtin_ffsll
 __builtin_fpclassify
 __builtin_huge_val
 __builtin_huge_valf
 __builtin_huge_vall
 __builtin_inf
 __builtin_infd128
 __builtin_infd32
 __builtin_infd64
 __builtin_inff
 __builtin_infl
 __builtin_isinf_sign
 __builtin_nan
 __builtin_nand128
 __builtin_nand32
 __builtin_nand64
 __builtin_nanf
 __builtin_nanl
 __builtin_nans
 __builtin_nansf
 __builtin_nansl
 __builtin_object_size
 __builtin_parity
 __builtin_parityl
 __builtin_parityll
 __builtin_popcount
 __builtin_popcountl
 __builtin_popcountll
 __builtin_powi
 __builtin_powif
 __builtin_powil
 __builtin_prefetch
 __builtin_trap
 __builtin_types_compatible_p
 __builtin_unreachable
@end smallexample

Unsupported built-ins will be tested with an empty parameter set and the
result of the check might be wrong or meaningless so use with care.

@majorheading Source Code

Download the
@uref{http://git.savannah.gnu.org/gitweb/?p=autoconf-archive.git;a=blob_plain;f=m4/ax_gcc_builtin.m4,latest
version of @file{ax_gcc_builtin.m4}} or browse
@uref{http://git.savannah.gnu.org/gitweb/?p=autoconf-archive.git;a=history;f=m4/ax_gcc_builtin.m4,the
macro's revision history}.

@majorheading License

@w{Copyright @copyright{} 2013 Gabriele Svelto @email{gabriele.svelto@@gmail.com}}

Copying and distribution of this file, with or without modification, are
permitted in any medium without royalty provided the copyright notice
and this notice are preserved.  This file is offered as-is, without any
warranty.