[PATCH] D66701: [ARM] Invert CSEL predicates if the opposite is a simpler constant to materialise

[Dave Green via Phabricator via llvm-commits]

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

This moves ConstantMaterializationCost into ARMBaseInstrInfo so that it can also be used in ISel Lowering, adding codesize values to the computed costs, to be able to compare either approximate instruction counts or codesize costs.

It also adds a HasLowerConstantMaterializationCost, which compares the ConstantMaterializationCost of two values, returning true if the first is smaller either in instruction count/codesize, or falling back to the other in the case that they are equal.

This is used in constant CSEL lowering to invert the predicate if the opposite is easier to materialise.


https://reviews.llvm.org/D66701

Files:
  llvm/lib/Target/ARM/ARMBaseInstrInfo.cpp
  llvm/lib/Target/ARM/ARMBaseInstrInfo.h
  llvm/lib/Target/ARM/ARMISelDAGToDAG.cpp
  llvm/lib/Target/ARM/ARMISelLowering.cpp
  llvm/test/CodeGen/Thumb2/csel.ll

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