[all-commits] [llvm/llvm-project] afe6af: [msan] Add optional flag to improve instrumentatio...

[Thurston Dang via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: afe6af14ff9b790232efaf9f57667eba38eddfc9
      https://github.com/llvm/llvm-project/commit/afe6af14ff9b790232efaf9f57667eba38eddfc9
  Author: Thurston Dang <thurston at google.com>
  Date:   2025-06-26 (Thu, 26 Jun 2025)

  Changed paths:
    M llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
    M llvm/test/Instrumentation/MemorySanitizer/or.ll

  Log Message:
  -----------
  [msan] Add optional flag to improve instrumentation of disjoint OR (#145990)

The disjoint OR (https://github.com/llvm/llvm-project/pull/72583) of two '1's is poison, hence the MSan ought to consider the result uninitialized (rather than initialized - i.e. a false negative - as per the existing instrumentation which ignores disjointedness). This patch adds a flag, `-msan-precise-disjoint-or`, which defaults to false (the legacy behavior). A future patch will default this flag to true.

Updates the test from https://github.com/llvm/llvm-project/pull/145982



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