Register spilling with recent gcc & clang
Submitted by Gael Guennebaud
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):
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gcc 5: OK
-
gcc >= 6: spilling in 2pX4 kernel
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clang: OK
With AVX+FMA:
-
gcc: OK
-
clang 5: OK
-
clang >=6: spilling in 3pX4 kernel
With AVX512f(+FMA)
-
gcc: ok
-
clang: ok