[PATCH] D13186: AMDGPU: Make SIInsertWaits about a factor of 4 faster

Matt Arsenault via llvm-commits llvm-commits at lists.llvm.org
Fri Sep 25 17:52:27 PDT 2015

arsenm created this revision.
arsenm added a reviewer: tstellarAMD.
arsenm added a subscriber: llvm-commits.
Herald added a subscriber: arsenm.

This was the slowest target custom pass and was spending 80%
of the time in getMinimalPhysRegClass which was called
for every register operand.
Try to use the statically known register class when possible from
the instruction's MCOperandInfo. There are a few pseudo instructions
which are not well behaved with unknown register classes which still
require the expensive physical register class search.
There are a few other possibilities for making this even faster,
such as not inspecting implicit operands. For now those are checked
because it is technically possible to have a scalar load into
exec or vcc which can be implicitly used.



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