Register spilling with recent gcc & clang
Submitted by Gael Guennebaud @ggael
Assigned to Nobody
Link to original bugzilla bug (#1637)
Description
We have some performance regressions with recent compiler versions of both clang and gcc. The problem is bad register allocation leading to spilling. More precisely, here is what I found:
With AVX (no FMA):
- gcc 5: OK
- gcc >= 6: spilling in 2pX4 kernel
- clang: OK
With AVX+FMA:
- gcc: OK
- clang 5: OK
- clang >=6: spilling in 3pX4 kernel
With AVX512f(+FMA)
- gcc: ok
- clang: ok