[PATCH] D122900: [x86] Disable optimization involved in an infinite loop inside DAG combiner.

[pierre gousseau via Phabricator via llvm-commits]

pgousseau updated this revision to Diff 420219.
pgousseau added a comment.

@RKSimon suggested the transformation might be caused by unneeded trunc/zext operations.
It is causing the DAG combiner to needlessly sink them under the OR operations so I have removed them where possible and this fixes the infinite loop.
The instructions generated end up being reordered is some cases but I think it is equivalent.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D122900/new/

https://reviews.llvm.org/D122900

Files:
  llvm/lib/Target/X86/X86ISelLowering.cpp
  llvm/test/CodeGen/X86/lzcnt-zext-cmp.ll

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