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ax_gcc_archflag

Synopsis

AX_GCC_ARCHFLAG([PORTABLE?], [ACTION-SUCCESS], [ACTION-FAILURE])

Description

This macro tries to guess the "native" arch corresponding to the target architecture for use with gcc’s -march=arch or -mtune=arch flags. If found, the cache variable $ax_cv_gcc_archflag is set to this flag and ACTION-SUCCESS is executed; otherwise $ax_cv_gcc_archflag is set to "unknown" and ACTION-FAILURE is executed. The default ACTION-SUCCESS is to add $ax_cv_gcc_archflag to the end of $CFLAGS.

PORTABLE? should be either [yes] (default) or [no]. In the former case, the flag is set to -mtune (or equivalent) so that the architecture is only used for tuning, but the instruction set used is still portable. In the latter case, the flag is set to -march (or equivalent) so that architecture-specific instructions are enabled.

The user can specify –with-gcc-arch=<arch> in order to override the macro’s choice of architecture, or –without-gcc-arch to disable this.

When cross-compiling, or if $CC is not gcc, then ACTION-FAILURE is called unless the user specified –with-gcc-arch manually.

Requires macros: AX_CHECK_COMPILE_FLAG, AX_GCC_X86_CPUID

(The main emphasis here is on recent CPUs, on the principle that doing high-performance computing on old hardware is uncommon.)

Source Code

Download the latest version of ax_gcc_archflag.m4 or browse the macro’s revision history.

License

Copyright © 2008 Steven G. Johnson stevenj@alum.mit.edu
Copyright © 2008 Matteo Frigo
Copyright © 2012 Tsukasa Oi

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/>.

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