[all-commits] [llvm/llvm-project] 15776b: [CycleInfo] Remove GenericCycle::TopLevelCycle. NF...

[Fangrui Song via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 15776b5cddd4bfd8ff06f2aac6e9eea09cf0112c
      https://github.com/llvm/llvm-project/commit/15776b5cddd4bfd8ff06f2aac6e9eea09cf0112c
  Author: Fangrui Song <i at maskray.me>
  Date:   2026-07-15 (Wed, 15 Jul 2026)

  Changed paths:
    M llvm/include/llvm/ADT/GenericCycleImpl.h
    M llvm/include/llvm/ADT/GenericCycleInfo.h

  Log Message:
  -----------
  [CycleInfo] Remove GenericCycle::TopLevelCycle. NFC (#209677)

moveTopLevelCycleToNewParent maintains TopLevelCycle eagerly, rewriting
the whole re-parented subtree with depth_first. When discovery nests k
cycles one by one this is quadratic, and the df_iterator walk plus its
visited set dominate construction on deep nests (~78% of time on a
1500-deep nest).

Walk ParentCycle links in getTopLevelParentCycle instead and delete the
member. The walk is valid during construction too: parent links are
always current, and discovery queries blocks whose innermost cycle sits
at the top of the forest being merged, so the walk is short.

Aided by Claude Fable 5



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