The build system adds -msse2 at configure.ac:473, but cpu_flags_x86_sse2 is not mentioned in the ebuild. The following snippet should be updated to take cpu_flags_x86_sse2 in account or else sse2 might be unintentionally enabled. (Also -mmmx should be dropped since it is not needed by the build system.) # CPU Detection (dynsimd) uses asm routines which requires 3dnow, mmx and sse. if use cpudetection && use cpu_flags_x86_3dnow && use cpu_flags_x86_sse ; then einfo "Enabling cpudetection (dynsimd). Adding -mmmx, -msse, -m3dnow and -O2 to CFLAGS." myconf="${myconf} --enable-dynsimd" append-flags -mmmx -msse -m3dnow -O2 fi Reproducible: Always
well, it was worse: dynsimd controls even building optimized asm routines, 3dnow or sse the -msse2 in configure.ac is just for building simd files, which are c files with only inline asm, so -msse2 shouldn't affect the rest of the build I've updated 0.124.1 to enable dynsimd with 3dnow or sse enabled; jack should detect automatically which one to use
