SLPVectorizer: Lazily allocate the map for block numbering.

There is no point in creating it if we're not going to vectorize
anything. Creating the map is expensive as it creates large values.
No functionality change.

llvm-svn: 207916

1 files changed, 19 insertions, 21 deletions

diff --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index 15fb6d72b84..d7ccb796d31 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -73,8 +73,6 @@ struct BlockNumbering {
 
   BlockNumbering(BasicBlock *Bb) : BB(Bb), Valid(false) {}
 
-  BlockNumbering() : BB(nullptr), Valid(false) {}
-
   void numberInstructions() {
     unsigned Loc = 0;
     InstrIdx.clear();
@@ -346,17 +344,10 @@ public:
   typedef SmallVector<StoreInst *, 8> StoreList;
 
   BoUpSLP(Function *Func, ScalarEvolution *Se, const DataLayout *Dl,
-          TargetTransformInfo *Tti, TargetLibraryInfo *TLi, AliasAnalysis *Aa, LoopInfo *Li,
-          DominatorTree *Dt) :
-      F(Func), SE(Se), DL(Dl), TTI(Tti), TLI(TLi), AA(Aa), LI(Li), DT(Dt),
-    Builder(Se->getContext()) {
-      // Setup the block numbering utility for all of the blocks in the
-      // function.
-      for (Function::iterator it = F->begin(), e = F->end(); it != e; ++it) {
-        BasicBlock *BB = it;
-        BlocksNumbers[BB] = BlockNumbering(BB);
-      }
-    }
+          TargetTransformInfo *Tti, TargetLibraryInfo *TLi, AliasAnalysis *Aa,
+          LoopInfo *Li, DominatorTree *Dt)
+      : F(Func), SE(Se), DL(Dl), TTI(Tti), TLI(TLi), AA(Aa), LI(Li), DT(Dt),
+        Builder(Se->getContext()) {}
 
   /// \brief Vectorize the tree that starts with the elements in \p VL.
   /// Returns the vectorized root.
@@ -528,6 +519,13 @@ private:
   /// Numbers instructions in different blocks.
   DenseMap<BasicBlock *, BlockNumbering> BlocksNumbers;
 
+  /// \brief Get the corresponding instruction numbering list for a given
+  /// BasicBlock. The list is allocated lazily.
+  BlockNumbering &getBlockNumbering(BasicBlock *BB) {
+    auto I = BlocksNumbers.insert(std::make_pair(BB, BlockNumbering(BB)));
+    return I.first->second;
+  }
+
   /// Reduction operators.
   ValueSet *RdxOps;
 
@@ -715,7 +713,7 @@ void BoUpSLP::buildTree_rec(ArrayRef<Value *> VL, unsigned Depth) {
         continue;
 
       // Make sure that we can schedule this unknown user.
-      BlockNumbering &BN = BlocksNumbers[BB];
+      BlockNumbering &BN = getBlockNumbering(BB);
       int UserIndex = BN.getIndex(UI);
       if (UserIndex < MyLastIndex) {
 
@@ -1328,8 +1326,8 @@ Value *BoUpSLP::getSinkBarrier(Instruction *Src, Instruction *Dst) {
 
 int BoUpSLP::getLastIndex(ArrayRef<Value *> VL) {
   BasicBlock *BB = cast<Instruction>(VL[0])->getParent();
-  assert(BB == getSameBlock(VL) && BlocksNumbers.count(BB) && "Invalid block");
-  BlockNumbering &BN = BlocksNumbers[BB];
+  assert(BB == getSameBlock(VL) && "Invalid block");
+  BlockNumbering &BN = getBlockNumbering(BB);
 
   int MaxIdx = BN.getIndex(BB->getFirstNonPHI());
   for (unsigned i = 0, e = VL.size(); i < e; ++i)
@@ -1339,8 +1337,8 @@ int BoUpSLP::getLastIndex(ArrayRef<Value *> VL) {
 
 Instruction *BoUpSLP::getLastInstruction(ArrayRef<Value *> VL) {
   BasicBlock *BB = cast<Instruction>(VL[0])->getParent();
-  assert(BB == getSameBlock(VL) && BlocksNumbers.count(BB) && "Invalid block");
-  BlockNumbering &BN = BlocksNumbers[BB];
+  assert(BB == getSameBlock(VL) && "Invalid block");
+  BlockNumbering &BN = getBlockNumbering(BB);
 
   int MaxIdx = BN.getIndex(cast<Instruction>(VL[0]));
   for (unsigned i = 1, e = VL.size(); i < e; ++i)
@@ -1762,9 +1760,9 @@ Value *BoUpSLP::vectorizeTree() {
     }
   }
 
-  for (Function::iterator it = F->begin(), e = F->end(); it != e; ++it) {
-    BlocksNumbers[it].forget();
-  }
+  for (auto &BN : BlocksNumbers)
+    BN.second.forget();
+
   Builder.ClearInsertionPoint();
 
   return VectorizableTree[0].VectorizedValue;