[all-commits] [llvm/llvm-project] 86d113: [SCEVExpand] Do not create redundant 'or false' fo...

[Florian Hahn via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 86d113a8b8aec1092d51115a8ff3e7e6682d1931
      https://github.com/llvm/llvm-project/commit/86d113a8b8aec1092d51115a8ff3e7e6682d1931
  Author: Florian Hahn <flo at fhahn.com>
  Date:   2022-01-06 (Thu, 06 Jan 2022)

  Changed paths:
    M llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp
    M llvm/test/Transforms/LoopDistribute/scev-inserted-runtime-check.ll
    M llvm/test/Transforms/LoopVectorize/ARM/mve-gather-scatter-tailpred.ll
    M llvm/test/Transforms/LoopVectorize/PowerPC/optimal-epilog-vectorization.ll
    M llvm/test/Transforms/LoopVectorize/X86/illegal-parallel-loop-uniform-write.ll
    M llvm/test/Transforms/LoopVectorize/X86/pr35432.ll
    M llvm/test/Transforms/LoopVectorize/first-order-recurrence-complex.ll
    M llvm/test/Transforms/LoopVectorize/induction.ll
    M llvm/test/Transforms/LoopVectorize/optimal-epilog-vectorization.ll
    M llvm/test/Transforms/LoopVectorize/pr30654-phiscev-sext-trunc.ll
    M llvm/test/Transforms/LoopVectorize/pr45259.ll
    M llvm/test/Transforms/LoopVectorize/runtime-check-needed-but-empty.ll
    M llvm/test/Transforms/LoopVectorize/runtime-check-small-clamped-bounds.ll
    M llvm/test/Transforms/LoopVersioning/wrapping-pointer-versioning.ll

  Log Message:
  -----------
  [SCEVExpand] Do not create redundant 'or false' for pred expansion.

This patch updates SCEVExpander::expandUnionPredicate to not create
redundant 'or false, x' instructions. While those are trivially
foldable, they can be easily avoided and hinder code that checks the
size/cost of the generated checks before further folds.

I am planning on look into a few other similar improvements to code
generated by SCEVExpander.

I remember a while ago @lebedev.ri working on doing some trivial folds
like that in IRBuilder itself, but there where concerns that such
changes may subtly break existing code.

Reviewed By: reames, lebedev.ri

Differential Revision: https://reviews.llvm.org/D116696