[PATCH] D74111: [LegalizeDAG][X86][AMDGPU] Use ANY_EXTEND instead of ZERO_EXTEND when promoting ISD::CTTZ/CTTZ_ZERO_UNDEF.

[Craig Topper via Phabricator via llvm-commits]

craig.topper created this revision.
craig.topper added reviewers: RKSimon, spatel, efriedma, arsenm.
Herald added subscribers: kerbowa, hiraditya, t-tye, tpr, dstuttard, yaxunl, nhaehnle, wdng, jvesely, kzhuravl.
Herald added a project: LLVM.

For CTTZ we place a set bit just past where the non-promoted type
stopped so the extended bits won't be used for the count. For
CTTZ_ZERO_UNDEF we don't care what happens if no bits are set in
the original type and we end up counting into the extended bits.
So we can just use ANY_EXTEND for both cases.

This matches what is done in type legalization for these operations.
We make no effort to force the upper bits to zero.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D74111

Files:
  llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
  llvm/test/CodeGen/AMDGPU/cttz_zero_undef.ll
  llvm/test/CodeGen/X86/clz.ll

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