[PATCH] D33076: [PPC] Move the combine "a << (b % (sizeof(a) * 8)) -> (PPCshl a, b)" to the backend. NFC.

[Tim Shen via Phabricator via llvm-commits]

timshen created this revision.
Herald added a subscriber: nemanjai.

Eli pointed out that it's unsafe to combine the shifts to ISD::SHL etc.,
because those are not defined for b > sizeof(a) * 8, even after some of
the combiners run.

However, PPCISD::SHL defines that behavior (as the instructions themselves).
Move the combination to the backend.

The tests in shift_mask.ll still pass.


https://reviews.llvm.org/D33076

Files:
  llvm/include/llvm/Target/TargetLowering.h
  llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  llvm/lib/Target/PowerPC/PPCISelLowering.cpp
  llvm/lib/Target/PowerPC/PPCISelLowering.h
  llvm/lib/Target/PowerPC/PPCInstrAltivec.td

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