[all-commits] [llvm/llvm-project] 5850c4: [InstCombine] Improve `foldDeadPhiWeb` compile tim...

[Mingjie Xu via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 5850c44288cba01c75f8afb7cfcf3a2d47e2d5a4
      https://github.com/llvm/llvm-project/commit/5850c44288cba01c75f8afb7cfcf3a2d47e2d5a4
  Author: Mingjie Xu <xumingjie.enna1 at bytedance.com>
  Date:   2025-09-15 (Mon, 15 Sep 2025)

  Changed paths:
    M llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp

  Log Message:
  -----------
  [InstCombine] Improve `foldDeadPhiWeb` compile time (#158057)

The foldDeadPhiWeb function identifies and removes small dead PHI webs,
it bails out if the web size exceeds threshold (16).

In the current implementation, when there is a phi node has large number
of users that most of them are phi nodes, we still push them on the
`Stack` even if the number of phi nodes user exceeds the threshold.

This patch checks the early stop condition when we push an unvisited phi
node on the `Stack`.
With this change, the wall duration of total instcombine pass decreased
from 523,649.276 ms to 208,687.042 ms in an our internal case.



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