[PATCH] D59317: [ARM] Search backwards for CMP when combining into CBZ

[Dave Green via Phabricator via llvm-commits]

dmgreen created this revision.
dmgreen added reviewers: efriedma, jmolloy, t.p.northover, samparker.
Herald added subscribers: hiraditya, kristof.beyls, javed.absar.
Herald added a project: LLVM.

The constant island pass currently only looks at the instruction immediately before a branch for a CMP to fold into a CBZ/CBNZ. This extends it to search backwards for the instruction that defines CPSR. We need to ensure that the register is not overridden between the CMP and the branch.

The test case is new, I have just shown the differences for clarity.


https://reviews.llvm.org/D59317

Files:
  llvm/lib/Target/ARM/ARMConstantIslandPass.cpp
  llvm/test/CodeGen/Thumb2/constant-islands-cbz.ll

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