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+# ===========================================================================
+# http://autoconf-archive.cryp.to/ax_gcc_x86_cpuid.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+# AX_GCC_X86_CPUID(OP)
+#
+# DESCRIPTION
+#
+# On Pentium and later x86 processors, with gcc or a compiler that has a
+# compatible syntax for inline assembly instructions, run a small program
+# that executes the cpuid instruction with input OP. This can be used to
+# detect the CPU type.
+#
+# On output, the values of the eax, ebx, ecx, and edx registers are stored
+# as hexadecimal strings as "eax:ebx:ecx:edx" in the cache variable
+# ax_cv_gcc_x86_cpuid_OP.
+#
+# If the cpuid 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_cpuid_OP
+# is set to the string "unknown".
+#
+# This macro mainly exists to be used in AX_GCC_ARCHFLAG.
+#
+# LICENSE
+#
+# Copyright (c) 2008 Steven G. Johnson <stevenj@alum.mit.edu>
+# Copyright (c) 2008 Matteo Frigo
+#
+# 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 <http://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.
+
+AC_DEFUN([AX_GCC_X86_CPUID],
+[AC_REQUIRE([AC_PROG_CC])
+AC_LANG_PUSH([C])
+AC_CACHE_CHECK(for x86 cpuid $1 output, ax_cv_gcc_x86_cpuid_$1,
+ [AC_RUN_IFELSE([AC_LANG_PROGRAM([#include <stdio.h>], [
+ int op = $1, eax, ebx, ecx, edx;
+ FILE *f;
+ __asm__("cpuid"
+ : "=a" (eax), "=b" (ebx), "=c" (ecx), "=d" (edx)
+ : "a" (op));
+ f = fopen("conftest_cpuid", "w"); if (!f) return 1;
+ fprintf(f, "%x:%x:%x:%x\n", eax, ebx, ecx, edx);
+ fclose(f);
+ return 0;
+])],
+ [ax_cv_gcc_x86_cpuid_$1=`cat conftest_cpuid`; rm -f conftest_cpuid],
+ [ax_cv_gcc_x86_cpuid_$1=unknown; rm -f conftest_cpuid],
+ [ax_cv_gcc_x86_cpuid_$1=unknown])])
+AC_LANG_POP([C])
+])