[all-commits] [llvm/llvm-project] fb6feb: [ADT] Restore handwritten vector find in SmallSet ...

[Victor Campos via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: fb6feb86a7dc324dcb2516397ba3fc5fe05ea584
      https://github.com/llvm/llvm-project/commit/fb6feb86a7dc324dcb2516397ba3fc5fe05ea584
  Author: Victor Campos <victor.campos at arm.com>
  Date:   2024-09-30 (Mon, 30 Sep 2024)

  Changed paths:
    M llvm/include/llvm/ADT/SmallSet.h

  Log Message:
  -----------
  [ADT] Restore handwritten vector find in SmallSet (#110254)

This patch restores handwritten linear searches instead of the use of
std::find.

After PR #109412, a performance regression was observed that's caused by
the use of std::find for linear searches.

The exact cause wasn't pinpointed, but, at the time of writing, the most
likely culprit is the forced loop unrolling in the definition of
libstdc++'s std::find. Presumably this is done to optimise for larger
containers.

However for the case of small containers such as SmallVector, this
actually hurts performance.



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