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

llvm/lib/Transforms/IPO/GlobalOpt.cpp

@@ -42,6 +42,7 @@
 #include "llvm/Transforms/Utils/GlobalStatus.h"
 #include "llvm/Transforms/Utils/ModuleUtils.h"
 #include <algorithm>
+#include <deque>
 using namespace llvm;
 
 #define DEBUG_TYPE "globalopt"
@@ -2166,7 +2167,7 @@ class Evaluator {
 public:
   Evaluator(const DataLayout *DL, const TargetLibraryInfo *TLI)
     : DL(DL), TLI(TLI) {
-    ValueStack.push_back(make_unique<DenseMap<Value*, Constant*>>());
+    ValueStack.emplace_back();
   }
 
   ~Evaluator() {
@@ -2191,13 +2192,13 @@ public:
 
   Constant *getVal(Value *V) {
     if (Constant *CV = dyn_cast<Constant>(V)) return CV;
-    Constant *R = ValueStack.back()->lookup(V);
+    Constant *R = ValueStack.back().lookup(V);
     assert(R && "Reference to an uncomputed value!");
     return R;
   }
 
   void setVal(Value *V, Constant *C) {
-    (*ValueStack.back())[V] = C;
+    ValueStack.back()[V] = C;
   }
 
   const DenseMap<Constant*, Constant*> &getMutatedMemory() const {
@@ -2212,9 +2213,9 @@ private:
   Constant *ComputeLoadResult(Constant *P);
 
   /// ValueStack - As we compute SSA register values, we store their contents
-  /// here. The back of the vector contains the current function and the stack
+  /// here. The back of the deque contains the current function and the stack
   /// contains the values in the calling frames.
-  SmallVector<std::unique_ptr<DenseMap<Value*, Constant*>>, 4> ValueStack;
+  std::deque<DenseMap<Value*, Constant*>> ValueStack;
 
   /// CallStack - This is used to detect recursion.  In pathological situations
   /// we could hit exponential behavior, but at least there is nothing
@@ -2526,7 +2527,7 @@ bool Evaluator::EvaluateBlock(BasicBlock::iterator CurInst,
 
         Constant *RetVal = nullptr;
         // Execute the call, if successful, use the return value.
-        ValueStack.push_back(make_unique<DenseMap<Value *, Constant *>>());
+        ValueStack.emplace_back();
         if (!EvaluateFunction(Callee, RetVal, Formals)) {
           DEBUG(dbgs() << "Failed to evaluate function.\n");
           return false;

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;