http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60233
--- Comment #5 from Uroš Bizjak <ubizjak at gmail dot com> --- (In reply to Jakub Jelinek from comment #4) > I think the reason for this is that -march=native passes in your case > -mf16c, and -mf16c implies -mavx. So, either OPTION_MASK_ISA_F16C_SET > should not include OPTION_MASK_ISA_AVX_SET, or the driver shouldn't set > -mf16c if AVX support is missing. > As at least some of the F16C instructions use ymmN registers, if we'd change > OPTION_MASK_ISA_F16C_SET, then the *256 TARGET_F16C patterns would also need > to be guarded with && TARGET_AVX. > For the latter alternative, we would need to do something like: > --- gcc/config/i386/driver-i386.c 2014-01-03 11:41:06.393269411 +0100 > +++ gcc/config/i386/driver-i386.c 2014-02-17 07:32:41.289022308 +0100 > @@ -513,6 +513,7 @@ const char *host_detect_local_cpu (int a > has_avx2 = 0; > has_fma = 0; > has_fma4 = 0; > + has_f16c = 0; > has_xop = 0; > has_xsave = 0; > has_xsaveopt = 0; This is the correct approach. We already disable f16c for -mno-avx in common/config/i386/i386-common.c in this way, and it looks that driver-i386.c was not updated accordingly. There are no real processors with F16C and no AVX, but we should be consistent here and follow i386-common.c.
