When we vectorize across multiple basic blocks we may vectorize PHINodes that create a cycle. We already break the cycle on phi-nodes, but arithmetic operations are still uplicated. This patch adds code that checks if the operation that we are vectorizing was vectorized during the visit of the operands and uses this value if it can.

llvm-svn: 186883

1 files changed, 31 insertions, 3 deletions

diff --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index 35022220694..25f7a78f667 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -264,12 +264,16 @@ private:
   /// This is the recursive part of buildTree.
   void buildTree_rec(ArrayRef<Value *> Roots, unsigned Depth);
 
-  /// Vectorizer a single entry in the tree.
+  /// Vectorize a single entry in the tree.
   Value *vectorizeTree(TreeEntry *E);
 
-  /// Vectorizer a single entry in the tree, starting in \p VL.
+  /// Vectorize a single entry in the tree, starting in \p VL.
   Value *vectorizeTree(ArrayRef<Value *> VL);
 
+  /// \returns the pointer to the vectorized value if \p VL is already
+  /// vectorized, or NULL. They may happen in cycles.
+  Value *alreadyVectorized(ArrayRef<Value *> VL);
+
   /// \brief Take the pointer operand from the Load/Store instruction.
   /// \returns NULL if this is not a valid Load/Store instruction.
   static Value *getPointerOperand(Value *I);
@@ -1117,6 +1121,16 @@ Value *BoUpSLP::Gather(ArrayRef<Value *> VL, VectorType *Ty) {
   return Vec;
 }
 
+Value *BoUpSLP::alreadyVectorized(ArrayRef<Value *> VL) {
+  if (ScalarToTreeEntry.count(VL[0])) {
+    int Idx = ScalarToTreeEntry[VL[0]];
+    TreeEntry *En = &VectorizableTree[Idx];
+    if (En->isSame(VL) && En->VectorizedValue)
+      return En->VectorizedValue;
+  }
+  return 0;
+}
+
 Value *BoUpSLP::vectorizeTree(ArrayRef<Value *> VL) {
   if (ScalarToTreeEntry.count(VL[0])) {
     int Idx = ScalarToTreeEntry[VL[0]];
@@ -1206,6 +1220,10 @@ Value *BoUpSLP::vectorizeTree(TreeEntry *E) {
 
       Builder.SetInsertPoint(getLastInstruction(E->Scalars));
       Value *InVec = vectorizeTree(INVL);
+
+      if (Value *V = alreadyVectorized(E->Scalars))
+        return V;
+
       CastInst *CI = dyn_cast<CastInst>(VL0);
       Value *V = Builder.CreateCast(CI->getOpcode(), InVec, VecTy);
       E->VectorizedValue = V;
@@ -1222,9 +1240,12 @@ Value *BoUpSLP::vectorizeTree(TreeEntry *E) {
       Builder.SetInsertPoint(getLastInstruction(E->Scalars));
       Value *L = vectorizeTree(LHSV);
       Value *R = vectorizeTree(RHSV);
-      Value *V;
+
+      if (Value *V = alreadyVectorized(E->Scalars))
+        return V;
 
       CmpInst::Predicate P0 = dyn_cast<CmpInst>(VL0)->getPredicate();
+      Value *V;
       if (Opcode == Instruction::FCmp)
         V = Builder.CreateFCmp(P0, L, R);
       else
@@ -1245,6 +1266,10 @@ Value *BoUpSLP::vectorizeTree(TreeEntry *E) {
       Value *Cond = vectorizeTree(CondVec);
       Value *True = vectorizeTree(TrueVec);
       Value *False = vectorizeTree(FalseVec);
+
+      if (Value *V = alreadyVectorized(E->Scalars))
+        return V;
+      
       Value *V = Builder.CreateSelect(Cond, True, False);
       E->VectorizedValue = V;
       return V;
@@ -1281,6 +1306,9 @@ Value *BoUpSLP::vectorizeTree(TreeEntry *E) {
         assert((VL0->getOperand(0) == VL0->getOperand(1)) && "Invalid order");
       }
 
+      if (Value *V = alreadyVectorized(E->Scalars))
+        return V;
+
       BinaryOperator *BinOp = cast<BinaryOperator>(VL0);
       Value *V = Builder.CreateBinOp(BinOp->getOpcode(), LHS, RHS);
       E->VectorizedValue = V;