[PATCH] D34979: [IndVars] Canonicalize comparisons between non-negative values and indvars

[Max Kazantsev via Phabricator via llvm-commits]

mkazantsev created this revision.

If there is a IndVar which is known to be non-negative, and there is a value which is also non-negative,
then signed and unsigned comparisons between them produce the same result. Both of those can be
seen in the same loop. To allow other optimizations to simplify them, we turn all instructions like

  %c = icmp slt i32 %iv, %b

to

  %c = icmp ult i32 %iv, %b

if both %iv and %b are known to be non-negative.


https://reviews.llvm.org/D34979

Files:
  lib/Transforms/Utils/SimplifyIndVar.cpp
  test/Analysis/ScalarEvolution/guards.ll
  test/Transforms/IndVarSimplify/canonicalize-cmp.ll
  test/Transforms/IndVarSimplify/eliminate-comparison.ll
  test/Transforms/IndVarSimplify/widen-loop-comp.ll

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