[all-commits] [llvm/llvm-project] 8cc83b: [MLGO] Count LR Evictions Rather than Relying on C...

[Aiden Grossman via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 8cc83b66e20e72cdb3bb5fbd549c941797b0e0c9
      https://github.com/llvm/llvm-project/commit/8cc83b66e20e72cdb3bb5fbd549c941797b0e0c9
  Author: Aiden Grossman <aidengrossman at google.com>
  Date:   2025-01-27 (Mon, 27 Jan 2025)

  Changed paths:
    M llvm/lib/CodeGen/MLRegAllocEvictAdvisor.cpp

  Log Message:
  -----------
  [MLGO] Count LR Evictions Rather than Relying on Cascade (#124440)

This patch adjusts the mlregalloc-max-cascade flag (renaming it to
mlregalloc-max-eviction-count) to actually count evictions rather than
just looking at the cascade number. The cascade number is not very
representative of how many times a LR has been evicted, which can lead
to some problems in certain cases, where we might end up with many
eviction problems where we have now masked off all the interferences and
are forced to evict the candidate.

This is probably what I should've done in the first place. No test case
as this only shows up in quite large functions post ThinLTO and it would
be hard to construct something that would serve as a nice regression
test without being super brittle. I've tested this on the pathological
cases that we have come across so far and it works.

Fixes #122829



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