[PATCH] D125287: [SLP] Improve root steering by building actual trees instead of calling the look-ahead heuristic

[Vasileios Porpodas via Phabricator via llvm-commits]

vporpo added inline comments.


================
Comment at: llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp:2028-2036
+      SmallVector<Value *, 2> Roots(
+          {Candidates[I].first, Candidates[I].second});
+      buildTree(Roots, /*UserIgnoreList=*/None,
+                RootLookAheadMaxSize.getValue());
+      if (isTreeTinyAndNotFullyVectorizable())
+        continue;
+      reorderTopToBottom();
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ABataev wrote:
> I'm afraid of increasing compile time. All this stuff includes scheduling, which may take lots of time for large basic blocks.
What if we set a flag to disable scheduling for these types of fast tree estimations? 


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D125287/new/

https://reviews.llvm.org/D125287