https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67406
Bug ID: 67406
Summary: OMP SIMD cloning does not generate fma instruction for
AVX2 target
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libgomp
Assignee: unassigned at gcc dot gnu.org
Reporter: vincenzo.innocente at cern dot ch
CC: jakub at gcc dot gnu.org
Target Milestone: ---
given
at simdCloning.cc
#pragma omp declare simd notinbranch
float fma(float x,float y, float z) {
return x+y*z;
}
compiled with
c++ -S -fopenmp -Ofast -Wall simdCloning.cc; cat simdCloning.s
will generate the same code for AVX and AVX2 clones
__ZGVdN8vvv__Z3fmafff:
LFB3:
leaq 8(%rsp), %r10
LCFI5:
andq $-32, %rsp
vmulps %ymm2, %ymm1, %ymm1
pushq -8(%r10)
pushq %rbp
vaddps %ymm0, %ymm1, %ymm0
while I would have expected
__ZGVdN8vvv__Z3fmafff:
LFB3:
leaq 8(%rsp), %r10
LCFI5:
andq $-32, %rsp
vfmadd231ps %ymm2, %ymm1, %ymm0
pushq -8(%r10)
pushq %rbp
this last code has been obtained compiling with -mfma.
unfortunately in this case ALL clones uses avx2 instructions
(so again AVX and AVX2 clones are identical)
btw: is there any reason why the AVX512 clone is not generated?
I am using gcc version 6.0.0 20150801 (experimental) [trunk revision 226463]
(GCC)
