[PATCH] D100094: [ARM] This patch adds some simplifications to ARMBlockPlacement Pass.

[Malhar via Phabricator via llvm-commits]

malharJ created this revision.
malharJ added reviewers: dmgreen, SjoerdMeijer.
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It simplifies the logic by moving the preHeader above the target/loopExit,
instead of the other way round.

Since the loopExit is no longer being moved, directions of
any branches within/to it are unaffected.

While the Preheader is being moved,

- The only directional branch within the Preheader is the backwards WLS (which gets corrected by the move).
- Directional branches like LE to the Preheader cannot regress (go backward to forward) since the PreHeader is being moved backwards.
- The only remaining consideration (for now) is that a forward WLS to the Preheader should not become backwards. This is taken care of by the patch.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D100094

Files:
  llvm/lib/Target/ARM/ARMBlockPlacement.cpp
  llvm/test/CodeGen/Thumb2/block-placement.mir

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