[PATCH] D121355: [SelectionDAG] Fold shift constants into cmp

[Allen zhong via Phabricator via llvm-commits]

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Perform the following transform for shift constants if legal

  X <  (NewC << ShiftBits)    -> X <  (NewC << ShiftBits)
  X >= (NewC << ShiftBits)    -> X >= (NewC << ShiftBits)
  X <= (NewC << ShiftBits) -1 -> X <  (NewC << ShiftBits)
  X >  (NewC << ShiftBits) -1 -> X >= (NewC << ShiftBits)


Fixes https://github.com/llvm/llvm-project/issues/54283


https://reviews.llvm.org/D121355

Files:
  llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
  llvm/test/CodeGen/AArch64/icmp-shift-opt.ll
  llvm/test/CodeGen/ARM/and-cmpz.ll
  llvm/test/CodeGen/ARM/consthoist-icmpimm.ll
  llvm/test/CodeGen/ARM/icmp-shift-opt.ll

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