56 lines
1.5 KiB
Diff
56 lines
1.5 KiB
Diff
|
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
|
||
|
|
|