From 08cbcd4dbc686bb38ec3093aff2f919fbff5ec17 Mon Sep 17 00:00:00 2001
From: Noah Goldstein <goldstein.w.n@gmail.com>
Date: Wed, 23 Jun 2021 19:19:34 -0400
Subject: [PATCH] x86: Remove unnecessary overflow check from wcsnlen-sse4_1.S
Content-type: text/plain; charset=UTF-8

No bug. The way wcsnlen will check if near the end of maxlen
is the following macro:

	mov	%r11, %rsi;	\
	subq	%rax, %rsi;	\
	andq	$-64, %rax;	\
	testq	$-64, %rsi;	\
	je	L(strnlen_ret)

Which words independently of s + maxlen overflowing. So the
second overflow check is unnecissary for correctness and
just extra overhead in the common no overflow case.

test-strlen.c, test-wcslen.c, test-strnlen.c and test-wcsnlen.c are
all passing

Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
---
 sysdeps/x86_64/multiarch/strlen-vec.S | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/sysdeps/x86_64/multiarch/strlen-vec.S b/sysdeps/x86_64/multiarch/strlen-vec.S
index 439e486a..b7657282 100644
--- a/sysdeps/x86_64/multiarch/strlen-vec.S
+++ b/sysdeps/x86_64/multiarch/strlen-vec.S
@@ -71,19 +71,12 @@ L(n_nonzero):
    suffice.  */
 	mov	%RSI_LP, %R10_LP
 	sar	$62, %R10_LP
-	test	%R10_LP, %R10_LP
 	jnz	__wcslen_sse4_1
 	sal	$2, %RSI_LP
 # endif
 
-
 /* Initialize long lived registers.  */
-
 	add	%RDI_LP, %RSI_LP
-# ifdef AS_WCSLEN
-/* Check for overflow again from s + maxlen * sizeof(wchar_t).  */
-	jbe	__wcslen_sse4_1
-# endif
 	mov	%RSI_LP, %R10_LP
 	and	$-64, %R10_LP
 	mov	%RSI_LP, %R11_LP
-- 
GitLab

