[all-commits] [llvm/llvm-project] 7d867c: [LoopVersioningLICM] Only mark pointers with gener...

[John Brawn via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 7d867c6d094cb1b7d98c5aab983558254fbd0fdc
      https://github.com/llvm/llvm-project/commit/7d867c6d094cb1b7d98c5aab983558254fbd0fdc
  Author: John Brawn <john.brawn at arm.com>
  Date:   2025-05-12 (Mon, 12 May 2025)

  Changed paths:
    M llvm/lib/Transforms/Scalar/LoopVersioningLICM.cpp
    A llvm/test/Transforms/LoopVersioningLICM/load-from-unknown-address.ll
    M llvm/test/Transforms/LoopVersioningLICM/loopversioningLICM1.ll
    M llvm/test/Transforms/LoopVersioningLICM/loopversioningLICM2.ll

  Log Message:
  -----------
  [LoopVersioningLICM] Only mark pointers with generated checks as noalias (#135168)

Currently when we version a loop all loads and stores have the noalias
metadata added to them. If there were some pointers that could not be
analysed, and thus we could not generate runtime aliasing checks for,
then we should not mark loads and stores using these pointers as
noalias.

This is done by getting rid of setNoAliasToLoop and instead using
annotateLoopWithNoAlias, as that already correctly handles partial alias
information. This does result in slightly different aliasing metadata
being generated, but it looks like it's more precise.

Currently this doesn't result in any change to the transforms that
LoopVersioningLICM does, as LoopAccessAnalysis discards all results if
it couldn't analyse every pointer leading to no loop versioning
happening, but an upcoming patch will change that and we need this first
otherwise we incorrectly mark some pointers as noalias even when they
aren't.



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