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| author | H.J. Lu <hjl.tools@gmail.com> | 2017-05-19 10:46:29 -0700 |
|---|---|---|
| committer | H.J. Lu <hjl.tools@gmail.com> | 2017-05-19 10:48:45 -0700 |
| commit | 402bf0695218bbe290418b9486b1dd5fe284d903 (patch) | |
| tree | 0107d383f8a38c75076dae69996b15b46e13b04a /bits | |
| parent | 1d71a6315396f6e1cc79a1d7ecca0a559929230a (diff) | |
x86: Optimize SSE2 memchr overflow calculation
SSE2 memchr computes "edx + ecx - 16" where ecx is less than 16. Use
"edx - (16 - ecx)", instead of satured math, to avoid possible addition
overflow. This replaces
add %ecx, %edx
sbb %eax, %eax
or %eax, %edx
sub $16, %edx
with
neg %ecx
add $16, %ecx
sub %ecx, %edx
It is the same for x86_64, except for rcx/rdx, instead of ecx/edx.
* sysdeps/i386/i686/multiarch/memchr-sse2.S (MEMCHR): Use
"edx + ecx - 16" to avoid possible addition overflow.
* sysdeps/x86_64/memchr.S (memchr): Likewise.
Diffstat (limited to 'bits')
0 files changed, 0 insertions, 0 deletions