[PATCH] D69563: [LV] Strip wrap flags from vectorized reductions

[Ayal Zaks via Phabricator via llvm-commits]

Ayal added inline comments.


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Comment at: llvm/lib/Transforms/Vectorize/LoopVectorize.cpp:394
+      Instruction *UI = cast<Instruction>(U);
+      if (L->contains(UI->getParent()) && Result.insert(UI).second)
+        Worklist.push_back(UI);
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This is indeed a general way to record all transitively dependent instructions inside a loop. In our case, though, there's a single known `LoopExitInst `with a single (loop-closed phi) user outside the loop. More efficient to record that user and check if (UI != OutsideUser && Result.insert(UI).second) than to repeatedly check if parent block belongs to L. Agreed?


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Comment at: llvm/lib/Transforms/Vectorize/LoopVectorize.cpp:3732
 
+  // Wrap flags are in general invalid after vectorization, clear them.
+  SmallPtrSet<Instruction *, 4> RedictionInstructions;
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Worth restricting this wrap-dropping treatment to RecurrenceKind's that may wrap, namely RK_IntegerAdd and RK_IntegerMult.


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Comment at: llvm/lib/Transforms/Vectorize/LoopVectorize.cpp:3733
+  // Wrap flags are in general invalid after vectorization, clear them.
+  SmallPtrSet<Instruction *, 4> RedictionInstructions;
+  collectReductionInstructions(Phi, OrigLoop, RedictionInstructions);
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RedictionInstructions >> ReductionInstructions


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  https://reviews.llvm.org/D69563/new/

https://reviews.llvm.org/D69563