[all-commits] [llvm/llvm-project] 0b6fae: [LoopInterchange] Reject inner-latch lcssa PHI fee...

[Madhur Amilkanthwar via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 0b6faeeaadc5791797e3708c4084f2be74212ca4
      https://github.com/llvm/llvm-project/commit/0b6faeeaadc5791797e3708c4084f2be74212ca4
  Author: Madhur Amilkanthwar <madhura at nvidia.com>
  Date:   2026-06-15 (Mon, 15 Jun 2026)

  Changed paths:
    M llvm/lib/Transforms/Scalar/LoopInterchange.cpp
    A llvm/test/Transforms/LoopInterchange/inner-latch-lcssa-feeds-exit-condition.ll

  Log Message:
  -----------
  [LoopInterchange] Reject inner-latch lcssa PHI feeding the exit condition (#202863)

In a multi-level nest, an lcssa PHI in the inner loop latch that feeds
the latch's exit condition can be left with a stale incoming block after
a subsequent interchange rewires the CFG, producing invalid IR. This
happened even when the outer latch had a single predecessor, where the
legality check returned early. Instead, reject the interchange when such
a PHI feeds the exit condition.

Fixes #202027



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