[PATCH] D109678: [LV][NFC] Cache scalar cost.

[Evgeniy via Phabricator via llvm-commits]

ebrevnov created this revision.
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Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D109678

Files:
  llvm/lib/Transforms/Vectorize/LoopVectorize.cpp


Index: llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
===================================================================
--- llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -1855,6 +1855,19 @@
   /// \p VF is the vectorization factor chosen for the original loop.
   bool isEpilogueVectorizationProfitable(const ElementCount VF) const;
 
+  /// Returns vectorization factor for scalar loop. The cost is computed on
+  /// the first call and cached value is returned on all consequent calls.
+  VectorizationFactor getScalarVF() const {
+    if (ScalarVF.Cost.isValid())
+      return ScalarVF;
+    const_cast<LoopVectorizationCostModel *>(this)->ScalarVF.Cost =
+        expectedCost(ScalarVF.Width).first;
+    assert(ScalarVF.Cost.isValid() &&
+           "Unexpected invalid cost for scalar loop");
+    LLVM_DEBUG(dbgs() << "LV: Scalar loop costs: " << ScalarVF.Cost << ".\n");
+    return ScalarVF;
+  }
+
 public:
   /// The loop that we evaluate.
   Loop *TheLoop;
@@ -1903,6 +1916,10 @@
 
   /// Profitable vector factors.
   SmallVector<VectorizationFactor, 8> ProfitableVFs;
+
+  /// Cached cost of one scalar iteraton;
+  VectorizationFactor ScalarVF = {ElementCount::getFixed(1),
+                                  InstructionCost::getInvalid()};
 };
 } // end namespace llvm
 
@@ -6057,14 +6074,10 @@
 
 VectorizationFactor LoopVectorizationCostModel::selectVectorizationFactor(
     const ElementCountSet &VFCandidates) {
-  InstructionCost ExpectedCost = expectedCost(ElementCount::getFixed(1)).first;
-  LLVM_DEBUG(dbgs() << "LV: Scalar loop costs: " << ExpectedCost << ".\n");
-  assert(ExpectedCost.isValid() && "Unexpected invalid cost for scalar loop");
   assert(VFCandidates.count(ElementCount::getFixed(1)) &&
          "Expected Scalar VF to be a candidate");
 
-  const VectorizationFactor ScalarCost(ElementCount::getFixed(1), ExpectedCost);
-  VectorizationFactor ChosenFactor = ScalarCost;
+  VectorizationFactor ChosenFactor = getScalarVF();
 
   bool ForceVectorization = Hints->getForce() == LoopVectorizeHints::FK_Enabled;
   if (ForceVectorization && VFCandidates.size() > 1) {
@@ -6096,7 +6109,7 @@
     }
 
     // If profitable add it to ProfitableVF list.
-    if (isMoreProfitable(Candidate, ScalarCost))
+    if (isMoreProfitable(Candidate, getScalarVF()))
       ProfitableVFs.push_back(Candidate);
 
     if (isMoreProfitable(Candidate, ChosenFactor))
@@ -6167,11 +6180,11 @@
     reportVectorizationFailure("There are conditional stores.",
         "store that is conditionally executed prevents vectorization",
         "ConditionalStore", ORE, TheLoop);
-    ChosenFactor = ScalarCost;
+    ChosenFactor = getScalarVF();
   }
 
   LLVM_DEBUG(if (ForceVectorization && !ChosenFactor.Width.isScalar() &&
-                 ChosenFactor.Cost >= ScalarCost.Cost) dbgs()
+                 ChosenFactor.Cost >= getScalarVF().Cost) dbgs()
              << "LV: Vectorization seems to be not beneficial, "
              << "but was forced by a user.\n");
   LLVM_DEBUG(dbgs() << "LV: Selecting VF: " << ChosenFactor.Width << ".\n");


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