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| author | H.J. Lu <hjl.tools@gmail.com> | 2019-07-24 14:48:33 -0700 |
|---|---|---|
| committer | H.J. Lu <hjl.tools@gmail.com> | 2019-07-24 14:48:43 -0700 |
| commit | 7e681561a3aea7aa8f21fb031a7c778147dfdf5b (patch) | |
| tree | 9d70b934aeae381ec82fa7b21481728bbf0ad59a /stdlib/labs.c | |
| parent | 82c664ed751f52a3074a9d6d366e87086f10b2f4 (diff) | |
| download | glibc-7e681561a3aea7aa8f21fb031a7c778147dfdf5b.tar.gz glibc-7e681561a3aea7aa8f21fb031a7c778147dfdf5b.tar.xz glibc-7e681561a3aea7aa8f21fb031a7c778147dfdf5b.zip | |
x86-64: Compile branred.c with -mprefer-vector-width=128 [BZ #24603]
When compiled with -O3 and AVX, GCC 8 and 9 optimize some loops in sysdeps/ieee754/dbl-64/branred.c with 256-bit vector instructions, which leads to store forward stall: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90579 There is no easy fix in compiler. This patch limits vector width to 128 bits to work around this issue. It improves performance of sin and cos by more than 40% on Skylake compiled with -O3 -march=skylake. Tested with GCC 7/8/9 on x86-64. [BZ #24603] * sysdeps/x86_64/configure.ac: Check if -mprefer-vector-width=128 works. * sysdeps/x86_64/configure: Regenerated. * sysdeps/x86_64/fpu/Makefile (CFLAGS-branred.c): New. Set to -mprefer-vector-width=128 if supported.
Diffstat (limited to 'stdlib/labs.c')
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