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* [glibc/release/2.34/master] x86: Replace sse2 instructions with avx in memcmp-evex-movbe.S
@ 2022-04-27  2:00 Sunil Pandey
  0 siblings, 0 replies; only message in thread
From: Sunil Pandey @ 2022-04-27  2:00 UTC (permalink / raw)
  To: glibc-cvs;h=baf3ece63453adac59c5688930324a78ced5b2e4

commit baf3ece63453adac59c5688930324a78ced5b2e4
Author: Noah Goldstein <>
Date:   Sat Oct 23 01:26:47 2021 -0400

    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 2761b54f2e..640f6757fa 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

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