[all-commits] [llvm/llvm-project] ea2f53: [SimplifyCFG] Avoid threading for loop headers (#1...

[Arne Stenkrona via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: ea2f5395b1acdc6eaf69a79b7660d7fa7d08c271
      https://github.com/llvm/llvm-project/commit/ea2f5395b1acdc6eaf69a79b7660d7fa7d08c271
  Author: Arne Stenkrona <arne.stenkrona at arm.com>
  Date:   2025-08-18 (Mon, 18 Aug 2025)

  Changed paths:
    M llvm/lib/Transforms/Utils/SimplifyCFG.cpp
    M llvm/test/CodeGen/ARM/2013-05-05-IfConvertBug.ll
    M llvm/test/Transforms/SimplifyCFG/2008-07-13-InfLoopMiscompile.ll
    A llvm/test/Transforms/SimplifyCFG/2025-07-29-non-canoncial-loop.ll
    M llvm/test/Transforms/SimplifyCFG/branch-phi-thread.ll
    M llvm/test/Transforms/SimplifyCFG/jump-threading.ll
    M llvm/test/Transforms/SimplifyCFG/two-entry-phi-return.ll

  Log Message:
  -----------
  [SimplifyCFG] Avoid threading for loop headers (#151142)

Updates SimplifyCFG to avoid jump threading through loop headers if
-keep-loops is requested. Canonical loop form requires a loop header
that dominates all blocks in the loop. If we thread through a header, we
risk breaking its domination of the loop. This change avoids this issue
by conservatively avoiding threading through headers entirely.

Fixes: https://github.com/llvm/llvm-project/issues/151144



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