[PATCH] D52345: [PowerPC] optimize conditional branch on CRSET/CRUNSET

[Hiroshi Inoue via Phabricator via llvm-commits]

inouehrs created this revision.
inouehrs added reviewers: hfinkel, echristo, power-llvm-team.
Herald added subscribers: jsji, kbarton, nemanjai.

This patch adds a check to optimize conditional branch (BC and BCn) based on a constant set by CRSET or CRUNSET.
Other optimizers, such as block placement, may generate such code and hence I do this at the very end of the optimization in pre-emit peephole pass.

A conditional branch based on a constant is eliminated or converted into unconditional branch. Also CRSET/CRUNSET is also eliminated if the condition code register is not used by instruction other than the branch to be optimized.

I observed such redundancy happened around 150 times while building LLVM bootctrap.


https://reviews.llvm.org/D52345

Files:
  lib/Target/PowerPC/PPCPreEmitPeephole.cpp
  test/CodeGen/PowerPC/setcr_bc.mir
  test/CodeGen/PowerPC/setcr_bc2.mir

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