From e7e0ac928b21e5f47e5b648723851c5270db24f2 Mon Sep 17 00:00:00 2001 From: Noah Goldstein Date: Sat, 23 Oct 2021 01:26:47 -0400 Subject: [PATCH] x86: Replace sse2 instructions with avx in memcmp-evex-movbe.S This commit replaces two usages of SSE2 'movups' with AVX 'vmovdqu'. it could potentially be dangerous to use SSE2 if this function is ever called without using 'vzeroupper' beforehand. While compilers appear to use 'vzeroupper' before function calls if AVX2 has been used, using SSE2 here is more brittle. Since it is not absolutely necessary it should be avoided. It costs 2-extra bytes but the extra bytes should only eat into alignment padding. Reviewed-by: H.J. Lu (cherry picked from commit bad852b61b79503fcb3c5fc379c70f768df3e1fb) --- sysdeps/x86_64/multiarch/memcmp-evex-movbe.S | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/sysdeps/x86_64/multiarch/memcmp-evex-movbe.S b/sysdeps/x86_64/multiarch/memcmp-evex-movbe.S index 2761b54f..640f6757 100644 --- a/sysdeps/x86_64/multiarch/memcmp-evex-movbe.S +++ b/sysdeps/x86_64/multiarch/memcmp-evex-movbe.S @@ -561,13 +561,13 @@ L(between_16_31): /* From 16 to 31 bytes. No branch when size == 16. */ /* Use movups to save code size. */ - movups (%rsi), %xmm2 + vmovdqu (%rsi), %xmm2 VPCMP $4, (%rdi), %xmm2, %k1 kmovd %k1, %eax testl %eax, %eax jnz L(return_vec_0_lv) /* Use overlapping loads to avoid branches. */ - movups -16(%rsi, %rdx, CHAR_SIZE), %xmm2 + vmovdqu -16(%rsi, %rdx, CHAR_SIZE), %xmm2 VPCMP $4, -16(%rdi, %rdx, CHAR_SIZE), %xmm2, %k1 addl $(CHAR_PER_VEC - (16 / CHAR_SIZE)), %edx kmovd %k1, %eax -- GitLab