[PATCH] D141179: [X86]] Search through commutable operators for BMI patterns (BLSI, BLSR, BLSMSK)

[Noah Goldstein via Phabricator via llvm-commits]

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(a & (-b)) & b is often lowered as:

  %sub  = sub i32     0, %b
  %and0 = and i32  %sub, %a
  %and1 = and i32 %and0, %b

Which won't get detected by the BLSI pattern as b & -b are never in
the same SDNode.

This patch will do a small search through commutable operators and try
and place BMI patterns in the same node so they will hit the pattern.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D141179

Files:
  llvm/lib/Target/X86/X86ISelLowering.cpp
  llvm/test/CodeGen/X86/bmi-out-of-order.ll

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