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| author | Noah Goldstein <goldstein.w.n@gmail.com> | 2021-06-23 19:19:34 -0400 |
|---|---|---|
| committer | Noah Goldstein <goldstein.w.n@gmail.com> | 2021-06-24 19:14:19 -0400 |
| commit | 08cbcd4dbc686bb38ec3093aff2f919fbff5ec17 (patch) | |
| tree | 970437dd91d18f00c146e93265d2b0aeae8f9c1d | |
| parent | bd3a2b3ed18fdeff0b370110c35850b51d025e8c (diff) | |
| download | glibc-08cbcd4dbc686bb38ec3093aff2f919fbff5ec17.tar glibc-08cbcd4dbc686bb38ec3093aff2f919fbff5ec17.tar.gz glibc-08cbcd4dbc686bb38ec3093aff2f919fbff5ec17.tar.bz2 glibc-08cbcd4dbc686bb38ec3093aff2f919fbff5ec17.zip | |
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>
| -rw-r--r-- | sysdeps/x86_64/multiarch/strlen-vec.S | 7 |
1 files changed, 0 insertions, 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 |