[all-commits] [llvm/llvm-project] 6f44f3: [TBAA] Only keep the immutable flag if both merged...

[Mian Miftah via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 6f44f333c3572d3ee54cdfdcba9124424b6ad1df
      https://github.com/llvm/llvm-project/commit/6f44f333c3572d3ee54cdfdcba9124424b6ad1df
  Author: Mian Miftah <mmiftah.duna at gmail.com>
  Date:   2026-09-25 (Fri, 25 Sep 2026)

  Changed paths:
    M llvm/lib/Analysis/TypeBasedAliasAnalysis.cpp
    A llvm/test/Analysis/TypeBasedAliasAnalysis/merge-immutable.ll

  Log Message:
  -----------
  [TBAA] Only keep the immutable flag if both merged tags have it (#225907)

getMostGenericTBAA() can return one of the two tags unchanged, as it
does when both have the same base type and offset. If only that tag has
the immutable flag, the merged access claims that the memory is constant
on both paths. For example, after SimplifyCFG hoists two such loads, GVN
can forward a load across a store to the same location.

Keep the immutable flag only if both tags have it. Otherwise drop just
the flag and keep the rest of the tag.



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