Checks if the host cpu supports various x86 instruction set, the instructions that will get tested are "mmx, popcnt, sse, sse2, sse3, sse4.1, sse4.2, sse4a, avx, avx2, avx512f, fma, fma4, bmi, bmi2". If the instruction set is supported by the host cpu, the C preprocessor macro HAVE_XXX_INSTRUCTIONS is set to 1. The XXX is up-cased instruction case with dot replaced by underscore. For example, the test for "sse4.2" would export HAVE_SSE4_2_INSTRUCTIONS=1. Also the compiler flag "-msse4.2" would be added to X86_FEATURE_CFLAGS variable, that can be obtained in Makefile.am using @X86_FEATURE_CFLAGS@.
If any of the test for the instruction set were succeeded, the configure script would run ACTION-IF-FOUND if it is specified, or append X86_FEATURE_CFLAGS to CFLAGS. If none of the instruction were found, ACTION-IF-NOT-FOUND hook is triggered.
This macro requires gcc extended builtin function "__builtin_cpu_init" and "__builtin_cpu_supports" to detect the cpu features. It will error out if the compiler doesn’t has these builtins.
See also AX_GCC_X86_CPU_SUPPORTS, which is the actual macro that perform the checks for the instruction sets.
Download the latest version of ax_check_x86_features.m4 or browse the macro’s revision history.
Copyright © 2016 Felix Chern firstname.lastname@example.org
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