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Autoconf Macro: ax_gcc_x86_cpuid
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<h1>
ax_gcc_x86_cpuid
</h1>
<h2>
Synopsis
</h2>
<p class="indent" style="white-space:nowrap;">
<code>AX_GCC_X86_CPUID(OP)</code>
</p>
<h2>
Description
</h2>
<div class="indent">
<p>
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.
</p>
<p>
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.
</p>
<p>
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".
</p>
<p>
This macro mainly exists to be used in AX_GCC_ARCHFLAG.
</p>
</div>
<h2>
Author
</h2>
<p class="indent">
Steven G. Johnson <stevenj@alum.mit.edu> and Matteo Frigo.
</p>
<h2>
Last Modified
</h2>
<p class="indent">
2005-05-30
</p>
<h2>
M4 Source Code
</h2>
<div class="indent">
<pre class="m4source">
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])
])
</pre>
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