[PATCH] D22226: [AArch64][CodeGen] Peephole optimization of Cmp+Bcc sequences with unconditional branch

[Evgeny Astigeevich via llvm-commits]

eastig created this revision.
eastig added a reviewer: t.p.northover.
eastig added a subscriber: llvm-commits.
Herald added subscribers: rengolin, aemerson.

This is a peephole optimization of Cmp+Bcc sequences with an unconditional branch. Such sequences can appear after the patch: http://reviews.llvm.org/D18838

When we compare with zero a result can be known. We can figure out which path is taken by Bcc and substitute Bcc by an unconditional branch to that path.

Rules:
  SUBS reg, 0; B.LO              => B <false path>
  SUBS reg, 0; B.HS <label> => B <label>


http://reviews.llvm.org/D22226

Files:
  lib/Target/AArch64/AArch64InstrInfo.cpp
  lib/Target/AArch64/AArch64InstrInfo.h
  test/CodeGen/AArch64/cmp-bcc-opt.mir

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