https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104704
--- Comment #9 from H.J. Lu <hjl.tools at gmail dot com> --- --- pieces-memset-46.s 2022-03-02 06:44:55.845212762 -0800 +++ /export/build/gnu/tools-build/gcc-gitlab-debug/build-x86_64-linux/gcc/pieces-memset-46.s 2022-03-02 06:45:03.313188978 -0800 @@ -8,9 +8,11 @@ foo: .cfi_startproc movq dst(%rip), %rdx movl $3, %eax - vpbroadcastb %eax, %zmm31 - vmovdqu8 %zmm31, (%rdx) - vmovw %xmm31, 64(%rdx) + vpbroadcastb %eax, %zmm0 + movl $771, %eax + movw %ax, 64(%rdx) + vmovdqu8 %zmm0, (%rdx) + vzeroupper ret .cfi_endproc .LFE0: gen_reg_rtx generates 2 extra instructions for pieces-memset-46.c.