[all-commits] [llvm/llvm-project] 668165: [InstCombine] Revert the `signed icmp -> unsigned ...

[Yingwei Zheng via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 668165002543fd3a88413a5c2601774395bfd10e
      https://github.com/llvm/llvm-project/commit/668165002543fd3a88413a5c2601774395bfd10e
  Author: Yingwei Zheng <dtcxzyw2333 at gmail.com>
  Date:   2024-01-05 (Fri, 05 Jan 2024)

  Changed paths:
    M llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
    M llvm/test/Transforms/InstCombine/smax-icmp.ll
    M llvm/test/Transforms/LoopVectorize/X86/float-induction-x86.ll
    M llvm/test/Transforms/LoopVectorize/X86/invariant-load-gather.ll
    M llvm/test/Transforms/LoopVectorize/X86/invariant-store-vectorization.ll
    M llvm/test/Transforms/LoopVectorize/float-induction.ll
    M llvm/test/Transforms/LoopVectorize/induction.ll
    M llvm/test/Transforms/LoopVectorize/interleaved-accesses-pred-stores.ll
    M llvm/test/Transforms/LoopVectorize/interleaved-accesses.ll
    M llvm/test/Transforms/LoopVectorize/invariant-store-vectorization-2.ll
    M llvm/test/Transforms/LoopVectorize/invariant-store-vectorization.ll
    M llvm/test/Transforms/LoopVectorize/loop-scalars.ll
    M llvm/test/Transforms/LoopVectorize/reduction.ll
    M llvm/test/Transforms/LoopVectorize/vector-geps.ll

  Log Message:
  -----------
  [InstCombine] Revert the `signed icmp -> unsigned icmp` canonicalization when folding `icmp Pred min|max(X, Y), Z` (#76685)

This patch tries to flip the signedness of predicates when folding an
unsigned icmp with a signed min/max. It will enable more optimizations
as we canonicalizes a signed icmp into an unsigned icmp when both
operands are known to have the same sign.
Fixes #76672.

Compile-time impact:
http://llvm-compile-time-tracker.com/compare.php?from=949ec83eaf6fa6dbffb94c2ea9c0a4d5efdbd239&to=2deca1aea8a4e13609bab72c522a97d424f0fc2d&stat=instructions:u


|stage1-O3|stage1-ReleaseThinLTO|stage1-ReleaseLTO-g|stage1-O0-g|stage2-O3|stage2-O0-g|stage2-clang|
|--|--|--|--|--|--|--|
|-0.00%|+0.01%|+0.05%|-0.12%|-0.01%|-0.03%|-0.00%|

NOTE: We can flip the signedness of predicate if both operands are
negative. But I don't see the benefit of handling these cases.