AX_GCC_ARCHFLAG([PORTABLE?], [ACTION-SUCCESS], [ACTION-FAILURE])
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.)
Download the latest version of ax_gcc_archflag.m4 or browse the macro’s revision history.
Copyright © 2008 Steven G. Johnson stevenj@alum.mit.edu
Copyright © 2008 Matteo Frigo
Copyright © 2014 Tsukasa Oi
Copyright © 2017-2018 Alexey Kopytov
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