[PATCH] D119643: [Transforms] Enhance CorrelatedValuePropagation to handle both values of select

[Dmitry Vassiliev via Phabricator via llvm-commits]

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The "Correlated Value Propagation" pass was missing a case when handling select instructions. It was only handling the "false" constant value, while in NVPTX the select may have the condition (and thus the branches) inverted, for example:

  loop:
  	%phi = phi i32* [ %sel, %loop ], [ %x, %entry ]
  	%f = tail call i32* @f(i32* %phi)
  	%cmp1 = icmp ne i32* %f, %y
  	%sel = select i1 %cmp1, i32* %f, i32* null
  	%cmp2 = icmp eq i32* %sel, null
  	br i1 %cmp2, label %return, label %loop

But the select condition can be inverted:

  	%cmp1 = icmp eq i32* %f, %y
  	%sel = select i1 %cmp1, i32* null, i32* %f

The fix is to enhance "Correlated Value Propagation" to handle both branches of the select instruction.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D119643

Files:
  llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
  llvm/test/Transforms/CorrelatedValuePropagation/select_cond.ll

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