[PATCH] D50972: [InstCombine] Fold icmp ugt/ult (add nuw X, C2), C --> icmp ugt/ult X, (C - C2)

[Nicola Zaghen via Phabricator via llvm-commits]

Nicola created this revision.
Nicola added reviewers: nlopes, spatel.
Herald added a subscriber: llvm-commits.

Support for sgt/slt was added in https://reviews.llvm.org/D29774, this adds the same cases also for unsigned compares.

Alive proof is at: https://rise4fun.com/Alive/nyY

Name: ult
Pre: WillNotOverflowUnsignedSub(C2, C1)
%a = add nuw i8 %x, C1
%b = icmp ult %a, C2

  =>

%b = icmp ult %x, C2-C1

Name: ugt
Pre: WillNotOverflowUnsignedSub(C2, C1)
%a = add nuw i8 %x, C1
%b = icmp ugt %a, C2

  =>

%b = icmp ugt %x, C2-C1

I updated the tests that changed and added new tests for the new combines.


Repository:
  rL LLVM

https://reviews.llvm.org/D50972

Files:
  lib/Transforms/InstCombine/InstCombineCompares.cpp
  test/Analysis/ValueTracking/non-negative-phi-bits.ll
  test/Transforms/InstCombine/icmp-add.ll
  test/Transforms/LoopVectorize/X86/masked_load_store.ll
  test/Transforms/LoopVectorize/if-conversion-nest.ll
  test/Transforms/LoopVectorize/runtime-check.ll

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