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# ===========================================================================
# https://www.gnu.org/software/autoconf-archive/ax_gcc_x86_avx_xgetbv.html
# ===========================================================================
#
# SYNOPSIS
#
# AX_GCC_X86_AVX_XGETBV
#
# DESCRIPTION
#
# On later x86 processors with AVX SIMD support, with gcc or a compiler
# that has a compatible syntax for inline assembly instructions, run a
# small program that executes the xgetbv instruction with input OP. This
# can be used to detect if the OS supports AVX instruction usage.
#
# On output, the values of the eax and edx registers are stored as
# hexadecimal strings as "eax:edx" in the cache variable
# ax_cv_gcc_x86_avx_xgetbv.
#
# If the xgetbv instruction fails (because you are running a
# cross-compiler, or because you are not using gcc, or because you are on
# a processor that doesn't have this instruction),
# ax_cv_gcc_x86_avx_xgetbv_OP is set to the string "unknown".
#
# This macro mainly exists to be used in AX_EXT.
#
# LICENSE
#
# Copyright (c) 2013 Michael Petch <mpetch@capp-sysware.com>
#
# This program is free software: you can redistribute it and/or modify it
# under the terms of the GNU General Public License as published by the
# Free Software Foundation, either version 3 of the License, or (at your
# option) any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
# Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program. If not, see <https://www.gnu.org/licenses/>.
#
# As a special exception, the respective Autoconf Macro's copyright owner
# gives unlimited permission to copy, distribute and modify the configure
# scripts that are the output of Autoconf when processing the Macro. You
# need not follow the terms of the GNU General Public License when using
# or distributing such scripts, even though portions of the text of the
# Macro appear in them. The GNU General Public License (GPL) does govern
# all other use of the material that constitutes the Autoconf Macro.
#
# This special exception to the GPL applies to versions of the Autoconf
# Macro released by the Autoconf Archive. When you make and distribute a
# modified version of the Autoconf Macro, you may extend this special
# exception to the GPL to apply to your modified version as well.
#serial 3
AC_DEFUN([AX_GCC_X86_AVX_XGETBV],
[AC_REQUIRE([AC_PROG_CC])
AC_LANG_PUSH([C])
AC_CACHE_CHECK(for x86-AVX xgetbv $1 output, ax_cv_gcc_x86_avx_xgetbv_$1,
[AC_RUN_IFELSE([AC_LANG_PROGRAM([#include <stdio.h>], [
int op = $1, eax, edx;
FILE *f;
/* Opcodes for xgetbv */
__asm__ __volatile__ (".byte 0x0f, 0x01, 0xd0"
: "=a" (eax), "=d" (edx)
: "c" (op));
f = fopen("conftest_xgetbv", "w"); if (!f) return 1;
fprintf(f, "%x:%x\n", eax, edx);
fclose(f);
return 0;
])],
[ax_cv_gcc_x86_avx_xgetbv_$1=`cat conftest_xgetbv`; rm -f conftest_xgetbv],
[ax_cv_gcc_x86_avx_xgetbv_$1=unknown; rm -f conftest_xgetbv],
[ax_cv_gcc_x86_avx_xgetbv_$1=unknown])])
AC_LANG_POP([C])
])
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