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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 /debug | |
| parent | 1d71a6315396f6e1cc79a1d7ecca0a559929230a (diff) | |
| download | glibc-402bf0695218bbe290418b9486b1dd5fe284d903.tar.gz glibc-402bf0695218bbe290418b9486b1dd5fe284d903.tar.xz glibc-402bf0695218bbe290418b9486b1dd5fe284d903.zip | |
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 'debug')
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