From 08cbcd4dbc686bb38ec3093aff2f919fbff5ec17 Mon Sep 17 00:00:00 2001 From: Noah Goldstein 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 Reviewed-by: H.J. Lu --- 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