[glibc/release/2.33/master] x86: Remove unnecessary overflow check from wcsnlen-sse4_1.S

[glibc/release/2.33/master] x86: Remove unnecessary overflow check from wcsnlen-sse4_1.S

[Sunil Pandey]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=853f83686ae12f572eea0546ed3cd195113653b3

commit 853f83686ae12f572eea0546ed3cd195113653b3
Author: Noah Goldstein <goldstein.w.n@gmail.com>
Date:   Wed Jun 23 19:19:34 2021 -0400

    x86: Remove unnecessary overflow check from wcsnlen-sse4_1.S
    
    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>
    (cherry picked from commit 08cbcd4dbc686bb38ec3093aff2f919fbff5ec17)

Diff:
---
 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 439e486a43..b7657282bd 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