From cf0dcdc71c8e568692b255b6338c289d85cb9a1e Mon Sep 17 00:00:00 2001
From: Nadav Rotem <nrotem@apple.com>
Date: Mon, 22 Jul 2013 22:18:07 +0000
Subject: 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
---
 llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp | 34 ++++++++++++++++++++++---
 1 file changed, 31 insertions(+), 3 deletions(-)

(limited to 'llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp')

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;
-- 
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