[PATCH] D36408: [LV] Minor fixes to Sink casts to unravel first order recurrence

[Ayal Zaks via Phabricator via llvm-commits]

Ayal created this revision.
Herald added a subscriber: mzolotukhin.

Two minor fixes: avoid copying a map and avoid redundant motion.


https://reviews.llvm.org/D36408

Files:
  lib/Transforms/Utils/LoopUtils.cpp
  lib/Transforms/Vectorize/LoopVectorize.cpp


Index: lib/Transforms/Vectorize/LoopVectorize.cpp
===================================================================
--- lib/Transforms/Vectorize/LoopVectorize.cpp
+++ lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -7653,7 +7653,7 @@
   // 2. Copy and widen instructions from the old loop into the new loop.
 
   // Move instructions to handle first-order recurrences.
-  DenseMap<Instruction *, Instruction *> SinkAfter = Legal->getSinkAfter();
+  DenseMap<Instruction *, Instruction *> &SinkAfter = Legal->getSinkAfter();
   for (auto &Entry : SinkAfter) {
     Entry.first->removeFromParent();
     Entry.first->insertAfter(Entry.second);
Index: lib/Transforms/Utils/LoopUtils.cpp
===================================================================
--- lib/Transforms/Utils/LoopUtils.cpp
+++ lib/Transforms/Utils/LoopUtils.cpp
@@ -565,7 +565,8 @@
     auto *I = Phi->user_back();
     if (I->isCast() && (I->getParent() == Phi->getParent()) && I->hasOneUse() &&
         DT->dominates(Previous, I->user_back())) {
-      SinkAfter[I] = Previous;
+      if (!DT->dominates(Previous, I)) // Otherwise we're good w/o sinking.
+        SinkAfter[I] = Previous;
       return true;
     }
   }


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