https://llvm.org/bugs/show_bug.cgi?id=27737
Bug ID: 27737
Summary: [SSE2] poor performance _mm_extract_epi8
Product: clang
Version: 3.8
Hardware: PC
OS: All
Status: NEW
Severity: normal
Priority: P
Component: Headers
Assignee: unassignedclangb...@nondot.org
Reporter: rozhuk...@gmail.com
CC: llvm-bugs@lists.llvm.org
Classification: Unclassified
I have some code that heavy uses _mm_extract_epi8().
Then I build with clang 3.8 and -msse2 (without -msse4.1) then program work
very slow.
To build with GCC and clang 3.4, 3.6, 3.7 I use macro:
#ifndef _mm_extract_epi8 /* SSE4.1 required. */
#define _mm_extract_epi8(__xmm, __n) \
((_mm_extract_epi16(__xmm, ((__n) >> 1)) >> (8 * ((__n) & 1))) & 0xff)
#endif
Test results:
AMD Athlon(tm) 5350 APU with Radeon(tm) R3 (2050.04-MHz K8-class CPU)
GCC: 20391006000 (SSE4.1) / 20116413000 (SSE2)
clang 3.8: 22329895000 (SSE4.1) / 117304135000 (SSE2) !!!
clang 3.7: 22367008000 (SSE4.1) / 25542571000 (SSE2)
clang 3.6: 22306648000 (SSE4.1) / 25914115000 (SSE2)
clang 3.4: 23684031000 (SSE4.1) / 25914115000 (SSE2)
Intel(R) Core(TM)2 Duo CPU E8400 @ 3.00GHz (2999.72-MHz K8-class CPU)
GCC: 12031595000 (SSE4.1) / 12011303000 (SSE2)
clang 3.8: 12431116000 (SSE4.1) / 73035466000 (SSE2) !!!
clang 3.7: 12458839000 (SSE4.1) / 13317058000 (SSE2)
clang 3.6: 12462181000 (SSE4.1) / 14119683000 (SSE2)
clang 3.4: 13555167000 (SSE4.1) / 13178893000 (SSE2)
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