https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101456
Bug ID: 101456 Summary: Unnecessary vzeroupper when upper bits of YMM registers already zero Product: gcc Version: 12.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: target Assignee: unassigned at gcc dot gnu.org Reporter: hjl.tools at gmail dot com CC: crazylht at gmail dot com Target Milestone: --- Target: i386, x86-64 Unnecessary vzeroupper: [hjl@gnu-cfl-2 tmp]$ cat x.c #include <x86intrin.h> extern __m256d x; void foo (void) { x = _mm256_setzero_pd (); } [hjl@gnu-cfl-2 tmp]$ gcc -S -O2 x.c -mavx2 c[hjl@gnu-cfl-2 tmp]$ cat x.s .file "x.c" .text .p2align 4 .globl foo .type foo, @function foo: .LFB5667: .cfi_startproc pushq %rbp .cfi_def_cfa_offset 16 .cfi_offset 6, -16 vxorpd %xmm0, %xmm0, %xmm0 vmovapd %ymm0, x(%rip) movq %rsp, %rbp .cfi_def_cfa_register 6 vzeroupper <<<<<< Not needed since upper bits of YMM0 are zero. popq %rbp .cfi_def_cfa 7, 8 ret .cfi_endproc .LFE5667: .size foo, .-foo .ident "GCC: (GNU) 11.1.1 20210531 (Red Hat 11.1.1-3)" .section .note.GNU-stack,"",@progbits [hjl@gnu-cfl-2 tmp]$