[PATCH] D123231: [StructurizeCFG] Improve basic block ordering

[Sameer Sahasrabuddhe via Phabricator via llvm-commits]

sameerds added a comment.

Needs more reviewers ... I would suggest authors of previous non-trivial changes to the structurizer, and their reviewers.



================
Comment at: llvm/lib/Transforms/Scalar/StructurizeCFG.cpp:449-451
+    if (Pred && Visited.count(Pred) && Succ && !Visited.count(Succ)) {
+      if (MoveTo.count(Pred))
+        Moved.reset(MoveTo[Pred]);
----------------
Lots of questions because the structurizer itself is so under-specified:

  # Seems like a block can be moved multiple times until it "floats" to its final place. Is this movement monotonic?
  # Can you please add a comment explaining the criterion in terms of the "Visited" state of the Structurizer itself?
  # Are there invariants about MoveTo and Moved that we could assert in each of the two for loops?
  # What happens when MoveTo[X] == MoveTo[Y]?


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D123231/new/

https://reviews.llvm.org/D123231