acinclude/ax_gcc_x86_cpuid.m4.htm
author Sam Lantinga <slouken@libsdl.org>
Wed, 04 Jun 2014 10:56:56 -0700
changeset 8820 0e935d5b193a
parent 5029 5d7d48157be7
permissions -rw-r--r--
Added annotations to help code analysis tools

CR: Bruce Dawson
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# ===========================================================================
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#     http://www.gnu.org/software/autoconf-archive/ax_gcc_x86_cpuid.html
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# ===========================================================================
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#
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# SYNOPSIS
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#
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#   AX_GCC_X86_CPUID(OP)
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#
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# DESCRIPTION
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#
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#   On Pentium and later x86 processors, with gcc or a compiler that has a
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#   compatible syntax for inline assembly instructions, run a small program
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#   that executes the cpuid instruction with input OP. This can be used to
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#   detect the CPU type.
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#
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#   On output, the values of the eax, ebx, ecx, and edx registers are stored
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#   as hexadecimal strings as "eax:ebx:ecx:edx" in the cache variable
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#   ax_cv_gcc_x86_cpuid_OP.
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#
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#   If the cpuid instruction fails (because you are running a
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#   cross-compiler, or because you are not using gcc, or because you are on
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#   a processor that doesn't have this instruction), ax_cv_gcc_x86_cpuid_OP
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#   is set to the string "unknown".
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#
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#   This macro mainly exists to be used in AX_GCC_ARCHFLAG.
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#
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# LICENSE
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#
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#   Copyright (c) 2008 Steven G. Johnson <stevenj@alum.mit.edu>
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#   Copyright (c) 2008 Matteo Frigo
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#
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#   This program is free software: you can redistribute it and/or modify it
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#   under the terms of the GNU General Public License as published by the
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#   Free Software Foundation, either version 3 of the License, or (at your
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#   option) any later version.
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#
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#   This program is distributed in the hope that it will be useful, but
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#   WITHOUT ANY WARRANTY; without even the implied warranty of
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#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
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#   Public License for more details.
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#
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#   You should have received a copy of the GNU General Public License along
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#   with this program. If not, see <http://www.gnu.org/licenses/>.
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#
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#   As a special exception, the respective Autoconf Macro's copyright owner
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#   gives unlimited permission to copy, distribute and modify the configure
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#   scripts that are the output of Autoconf when processing the Macro. You
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#   need not follow the terms of the GNU General Public License when using
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#   or distributing such scripts, even though portions of the text of the
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#   Macro appear in them. The GNU General Public License (GPL) does govern
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#   all other use of the material that constitutes the Autoconf Macro.
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#
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#   This special exception to the GPL applies to versions of the Autoconf
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#   Macro released by the Autoconf Archive. When you make and distribute a
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#   modified version of the Autoconf Macro, you may extend this special
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#   exception to the GPL to apply to your modified version as well.
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#serial 7
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AC_DEFUN([AX_GCC_X86_CPUID],
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[AC_REQUIRE([AC_PROG_CC])
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AC_LANG_PUSH([C])
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AC_CACHE_CHECK(for x86 cpuid $1 output, ax_cv_gcc_x86_cpuid_$1,
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 [AC_RUN_IFELSE([AC_LANG_PROGRAM([#include <stdio.h>], [
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     int op = $1, eax, ebx, ecx, edx;
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     FILE *f;
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      __asm__("cpuid"
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        : "=a" (eax), "=b" (ebx), "=c" (ecx), "=d" (edx)
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        : "a" (op));
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     f = fopen("conftest_cpuid", "w"); if (!f) return 1;
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     fprintf(f, "%x:%x:%x:%x\n", eax, ebx, ecx, edx);
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     fclose(f);
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     return 0;
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])],
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     [ax_cv_gcc_x86_cpuid_$1=`cat conftest_cpuid`; rm -f conftest_cpuid],
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     [ax_cv_gcc_x86_cpuid_$1=unknown; rm -f conftest_cpuid],
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     [ax_cv_gcc_x86_cpuid_$1=unknown])])
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AC_LANG_POP([C])
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])