Hi, This patch makes "prefer-avx256" option as default tuning for "skylake-avx512". This is due to better performance of 256-bit code for some of the cases. In case of Skylake Server the Optimization Manual has following "Since port 0 and port 1 are 256-bits wide, Intel AVX-512 operations that will be dispatched to port 0 will execute on both port 0 and port 1" (chapter 2.1 in https://software.intel.com/sites/default/files/managed/9e/bc/64-ia-32-architectures-optimization-manual.pdf).
It is platform and case specific and not applicable to every AVX512-available
platform.
Option purpose is to make this code generation more performance efficient. It
provides
performance gain on SPEC2017int on Skylake Server for -march=skylake-avx512.
Patch leaves opportunity for some of AVX-512 instructions generated where they
are the most efficient.
2017-10-31 Sergey Shalnov <sergey.shal...@intel.com>
gcc/
* config/i386/x86-tune.def (X86_TUNE_AVX256_OPTIMAL): Add tuning
option prefer-avx256 for skylake-avx512 configuration.
* config/i386/i386.c (ix86_option_override_internal): Ditto.
(get_builtin_code_for_version): Ditto.
Sergey
0003-Make-prefer-avx256-default-for-skylake-avx512.patch
Description: 0003-Make-prefer-avx256-default-for-skylake-avx512.patch
