[all-commits] [llvm/llvm-project] e24c9e: [IR] improve hashing quality for ValueInfo (#132917)

[Zhaoxuan Jiang via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: e24c9e7a0c61ed49e79433d405cb5157483ce691
      https://github.com/llvm/llvm-project/commit/e24c9e7a0c61ed49e79433d405cb5157483ce691
  Author: Zhaoxuan Jiang <jiangzhaoxuan94 at gmail.com>
  Date:   2025-04-09 (Wed, 09 Apr 2025)

  Changed paths:
    M llvm/include/llvm/IR/ModuleSummaryIndex.h

  Log Message:
  -----------
  [IR] improve hashing quality for ValueInfo (#132917)

The current hashing quality for `ValueInfo` is poor because it uses
pointers as the hash value, which can negatively impact performance in
various places that use a `DenseSet`/`Map` of `ValueInfo`. In one
observed case, `ModuleSummaryIndex::propagateAttributes()` was taking
about 25 minutes to complete on a ThinLTO application. Profiling
revealed that the majority of this time was spent operating on the
`MarkedNonReadWriteOnly` set.

With the improved hashing, the execution time for `propagateAttributes`
is dramatically reduced to less than 10 seconds.



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