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@node ax_gcc_x86_cpuid
@unnumberedsec ax_gcc_x86_cpuid
@majorheading Synopsis
@smallexample
AX_GCC_X86_CPUID(OP)
AX_GCC_X86_CPUID_COUNT(OP, COUNT)
@end smallexample
@majorheading 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. AX_GCC_X86_CPUID_COUNT takes an additional COUNT
parameter that gets passed into register ECX before calling cpuid.
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.
@majorheading Source Code
Download the
@uref{http://git.savannah.gnu.org/gitweb/?p=autoconf-archive.git;a=blob_plain;f=m4/ax_gcc_x86_cpuid.m4,latest
version of @file{ax_gcc_x86_cpuid.m4}} or browse
@uref{http://git.savannah.gnu.org/gitweb/?p=autoconf-archive.git;a=history;f=m4/ax_gcc_x86_cpuid.m4,the
macro's revision history}.
@majorheading License
@w{Copyright @copyright{} 2008 Steven G. Johnson @email{stevenj@@alum.mit.edu}} @* @w{Copyright @copyright{} 2008 Matteo Frigo} @* @w{Copyright @copyright{} 2015 Michael Petch @email{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 <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
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This special exception to the GPL applies to versions of the Autoconf
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