[PATCH] D89214: [X86] Add basic computeKnownBits support for X86ISD::BSR

[Craig Topper via Phabricator via llvm-commits]

craig.topper created this revision.
craig.topper added reviewers: RKSimon, spatel.
Herald added subscribers: javed.absar, hiraditya.
Herald added a project: LLVM.
craig.topper requested review of this revision.

The behavior is undefined for an input of 0, otherwise the result
is the position of the most significant set bit which must be in
the range [0, bitwidth-1]. So any bits above log2 of bitwidth
must be 0.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D89214

Files:
  llvm/lib/Target/X86/X86ISelLowering.cpp
  llvm/test/CodeGen/X86/clz.ll
  llvm/test/CodeGen/X86/pr40090.ll
  llvm/test/CodeGen/X86/scheduler-backtracking.ll

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