On Thu, Jan 11, 2018 at 3:10 AM, Mason <slash.tmp@xxxxxxx> wrote: > On 11/01/2018 03:44, Roland Schulz wrote: > >> Is it possible to have a "if constexpr" inside a __target_clones__ >> multiversioned function to have certain parts of the function depend >> on the target? Outside of multiversioned function one normally would >> use preprocessor defines to query the SIMD support (e.g. __AVX__). >> But this doesn't work inside target_clones given that preprocessor >> variables don't depend on the target. __builtin_cpu_supports doesn't >> work because it isn't constexpr (and is meant for runtime detection). >> One could extract the target specific part into its own function >> (using target rather than target_clones attribute) but that doesn't >> work with different types. Is there some other way to query the >> target which does work inside a multiversioned function? > > I've CCed a few people involved in function multi-versioning. > > Also, Billy O'Mahony used to work on FMV. > > The following article might be interesting to you: > https://lwn.net/Articles/691932/ > > Regards. Hi Are you looking for simething like this ? #include <stdio.h> #include <immintrin.h> #define MAX 1000000 int a[256], b[256], c[256]; __attribute__((target_clones("avx2","arch=atom","default"))) void foo(){ int i,x; for (x=0; x<MAX; x++){ for (i=0; i<256; i++){ a[i] = b[i] + c[i]; } } } int main() { if (__builtin_cpu_supports ("ssse3")){ printf("System supprot SSE\n"); } if (__builtin_cpu_supports ("avx2")){ printf("System support AVX2\n"); } if (__builtin_cpu_supports ("avx512f")){ printf("System supports AVX 512\n"); } foo(); return 0; } # gcc fmv.c -O3 -o fmv # ./fmv System supprot SSE System support AVX2 more info here : https://gcc.gnu.org/onlinedocs/gcc-4.8.5/gcc/X86-Built-in-Functions.html once in the specific function you can also use #pragma GCC target https://gcc.gnu.org/onlinedocs/gcc-4.5.0/gcc/Function-Specific-Option-Pragmas.html Hope it helps Regards Victor Rodriguez
