https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93009
--- Comment #8 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jakub Jelinek <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:fbbc4c24fd7ba87e0c47cd965ae624afba6fa375 commit r10-5954-gfbbc4c24fd7ba87e0c47cd965ae624afba6fa375 Author: Jakub Jelinek <ja...@redhat.com> Date: Wed Jan 15 00:30:10 2020 +0100 i386: Fix wrong-code x86 issue with avx512{f,vl} fma PR93009 As mentioned in the PR, the following testcase is miscompiled with avx512vl. The reason is that the fma *_bcst_1 define_insns have two alternatives: "=v,v" "0,v" "v,0" "m,m" and use the same vfmadd213* %3<avx512bcst>, %2, %0<sd_mask_op4> pattern. If the first alternative is chosen, everything is ok, but if the second alternative is chosen, %2 and %0 are the same register, so instead of doing dest=dest*another+membcst we do dest=dest*dest+membcst. Now, to fix this, either we'd need separate: "vfmadd213<ssemodesuffix>\t{%3<avx512bcst>, %2, %0<sd_mask_op4>|%0<sd_mask_op4>, %2, %3<avx512bcst>} vfmadd213<ssemodesuffix>\t{%3<avx512bcst>, %1, %0<sd_mask_op4>|%0<sd_mask_op4>, %1, %3<avx512bcst>}" where for the second alternative, we'd just use %1 instead of %2, but what I think is actually cleaner is just use a single alternative and make the two multiplication operands commutative, which they really are. 2020-01-15 Jakub Jelinek <ja...@redhat.com> PR target/93009 * config/i386/sse.md (*<sd_mask_codefor>fma_fmadd_<mode><sd_maskz_name>_bcst_1, *<sd_mask_codefor>fma_fmsub_<mode><sd_maskz_name>_bcst_1, *<sd_mask_codefor>fma_fnmadd_<mode><sd_maskz_name>_bcst_1, *<sd_mask_codefor>fma_fnmsub_<mode><sd_maskz_name>_bcst_1): Use just a single alternative instead of two, make operands 1 and 2 commutative. * gcc.target/i386/avx512vl-pr93009.c: New test.
