Masked Load and Store Intrinsics in loop vectorizer.

The loop vectorizer optimizes loops containing conditional memory
accesses by generating masked load and store intrinsics.
This decision is target dependent.

http://reviews.llvm.org/D6527

llvm-svn: 224334

1 files changed, 100 insertions, 21 deletions

diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index dca6a0c4bcd..96a169d7ed9 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -580,9 +580,10 @@ public:
 
   LoopVectorizationLegality(Loop *L, ScalarEvolution *SE, const DataLayout *DL,
                             DominatorTree *DT, TargetLibraryInfo *TLI,
-                            AliasAnalysis *AA, Function *F)
+                            AliasAnalysis *AA, Function *F,
+                            const TargetTransformInfo *TTI)
       : NumLoads(0), NumStores(0), NumPredStores(0), TheLoop(L), SE(SE), DL(DL),
-        DT(DT), TLI(TLI), AA(AA), TheFunction(F), Induction(nullptr),
+        DT(DT), TLI(TLI), AA(AA), TheFunction(F), TTI(TTI), Induction(nullptr),
         WidestIndTy(nullptr), HasFunNoNaNAttr(false), MaxSafeDepDistBytes(-1U) {
   }
 
@@ -768,6 +769,21 @@ public:
   }
   SmallPtrSet<Value *, 8>::iterator strides_end() { return StrideSet.end(); }
 
+  /// Returns true if the target machine supports masked store operation
+  /// for the given \p DataType and kind of access to \p Ptr.
+  bool isLegalMaskedStore(Type *DataType, Value *Ptr) {
+    return TTI->isLegalMaskedStore(DataType, isConsecutivePtr(Ptr));
+  }
+  /// Returns true if the target machine supports masked load operation
+  /// for the given \p DataType and kind of access to \p Ptr.
+  bool isLegalMaskedLoad(Type *DataType, Value *Ptr) {
+    return TTI->isLegalMaskedLoad(DataType, isConsecutivePtr(Ptr));
+  }
+  /// Returns true if vector representation of the instruction \p I
+  /// requires mask.
+  bool isMaskRequired(const Instruction* I) {
+    return (MaskedOp.count(I) != 0);
+  }
 private:
   /// Check if a single basic block loop is vectorizable.
   /// At this point we know that this is a loop with a constant trip count
@@ -840,6 +856,8 @@ private:
   AliasAnalysis *AA;
   /// Parent function
   Function *TheFunction;
+  /// Target Transform Info
+  const TargetTransformInfo *TTI;
 
   //  ---  vectorization state --- //
 
@@ -871,6 +889,10 @@ private:
 
   ValueToValueMap Strides;
   SmallPtrSet<Value *, 8> StrideSet;
+  
+  /// While vectorizing these instructions we have to generate a
+  /// call to the appropriate masked intrinsic
+  SmallPtrSet<const Instruction*, 8> MaskedOp;
 };
 
 /// LoopVectorizationCostModel - estimates the expected speedups due to
@@ -1373,7 +1395,7 @@ struct LoopVectorize : public FunctionPass {
     }
 
     // Check if it is legal to vectorize the loop.
-    LoopVectorizationLegality LVL(L, SE, DL, DT, TLI, AA, F);
+    LoopVectorizationLegality LVL(L, SE, DL, DT, TLI, AA, F, TTI);
     if (!LVL.canVectorize()) {
       DEBUG(dbgs() << "LV: Not vectorizing: Cannot prove legality.\n");
       emitMissedWarning(F, L, Hints);
@@ -1761,7 +1783,8 @@ void InnerLoopVectorizer::vectorizeMemoryInstruction(Instruction *Instr) {
   unsigned ScalarAllocatedSize = DL->getTypeAllocSize(ScalarDataTy);
   unsigned VectorElementSize = DL->getTypeStoreSize(DataTy)/VF;
 
-  if (SI && Legal->blockNeedsPredication(SI->getParent()))
+  if (SI && Legal->blockNeedsPredication(SI->getParent()) &&
+      !Legal->isMaskRequired(SI))
     return scalarizeInstruction(Instr, true);
 
   if (ScalarAllocatedSize != VectorElementSize)
@@ -1855,8 +1878,24 @@ void InnerLoopVectorizer::vectorizeMemoryInstruction(Instruction *Instr) {
 
       Value *VecPtr = Builder.CreateBitCast(PartPtr,
                                             DataTy->getPointerTo(AddressSpace));
-      StoreInst *NewSI =
-        Builder.CreateAlignedStore(StoredVal[Part], VecPtr, Alignment);
+
+      Instruction *NewSI;
+      if (Legal->isMaskRequired(SI)) {
+        Type *I8PtrTy =
+        Builder.getInt8PtrTy(PartPtr->getType()->getPointerAddressSpace());
+
+        Value *I8Ptr = Builder.CreateBitCast(PartPtr, I8PtrTy);
+
+        VectorParts Cond = createBlockInMask(SI->getParent());
+        SmallVector <Value *, 8> Ops;
+        Ops.push_back(I8Ptr);
+        Ops.push_back(StoredVal[Part]);
+        Ops.push_back(Builder.getInt32(Alignment));
+        Ops.push_back(Cond[Part]);
+        NewSI = Builder.CreateMaskedStore(Ops);
+      }
+      else 
+        NewSI = Builder.CreateAlignedStore(StoredVal[Part], VecPtr, Alignment);
       propagateMetadata(NewSI, SI);
     }
     return;
@@ -1876,9 +1915,26 @@ void InnerLoopVectorizer::vectorizeMemoryInstruction(Instruction *Instr) {
       PartPtr = Builder.CreateGEP(PartPtr, Builder.getInt32(1 - VF));
     }
 
-    Value *VecPtr = Builder.CreateBitCast(PartPtr,
-                                          DataTy->getPointerTo(AddressSpace));
-    LoadInst *NewLI = Builder.CreateAlignedLoad(VecPtr, Alignment, "wide.load");
+    Instruction* NewLI;
+    if (Legal->isMaskRequired(LI)) {
+      Type *I8PtrTy =
+        Builder.getInt8PtrTy(PartPtr->getType()->getPointerAddressSpace());
+
+      Value *I8Ptr = Builder.CreateBitCast(PartPtr, I8PtrTy);
+
+      VectorParts SrcMask = createBlockInMask(LI->getParent());
+      SmallVector <Value *, 8> Ops;
+      Ops.push_back(I8Ptr);
+      Ops.push_back(UndefValue::get(DataTy));
+      Ops.push_back(Builder.getInt32(Alignment));
+      Ops.push_back(SrcMask[Part]);
+      NewLI = Builder.CreateMaskedLoad(Ops);
+    }
+    else {
+      Value *VecPtr = Builder.CreateBitCast(PartPtr,
+                                            DataTy->getPointerTo(AddressSpace));
+      NewLI = Builder.CreateAlignedLoad(VecPtr, Alignment, "wide.load");
+    }
     propagateMetadata(NewLI, LI);
     Entry[Part] = Reverse ? reverseVector(NewLI) :  NewLI;
   }
@@ -5305,12 +5361,27 @@ bool LoopVectorizationLegality::blockNeedsPredication(BasicBlock *BB)  {
 
 bool LoopVectorizationLegality::blockCanBePredicated(BasicBlock *BB,
                                            SmallPtrSetImpl<Value *> &SafePtrs) {
+  
   for (BasicBlock::iterator it = BB->begin(), e = BB->end(); it != e; ++it) {
+    // Check that we don't have a constant expression that can trap as operand.
+    for (Instruction::op_iterator OI = it->op_begin(), OE = it->op_end();
+         OI != OE; ++OI) {
+      if (Constant *C = dyn_cast<Constant>(*OI))
+        if (C->canTrap())
+          return false;
+    }
     // We might be able to hoist the load.
     if (it->mayReadFromMemory()) {
       LoadInst *LI = dyn_cast<LoadInst>(it);
-      if (!LI || !SafePtrs.count(LI->getPointerOperand()))
+      if (!LI)
+        return false;
+      if (!SafePtrs.count(LI->getPointerOperand())) {
+        if (isLegalMaskedLoad(LI->getType(), LI->getPointerOperand())) {
+          MaskedOp.insert(LI);
+          continue;
+        }
         return false;
+      }
     }
 
     // We don't predicate stores at the moment.
@@ -5318,22 +5389,30 @@ bool LoopVectorizationLegality::blockCanBePredicated(BasicBlock *BB,
       StoreInst *SI = dyn_cast<StoreInst>(it);
       // We only support predication of stores in basic blocks with one
       // predecessor.
-      if (!SI || ++NumPredStores > NumberOfStoresToPredicate ||
-          !SafePtrs.count(SI->getPointerOperand()) ||
-          !SI->getParent()->getSinglePredecessor())
+      if (!SI)
+        return false;
+
+      bool isSafePtr = (SafePtrs.count(SI->getPointerOperand()) != 0);
+      bool isSinglePredecessor = SI->getParent()->getSinglePredecessor();
+      
+      if (++NumPredStores > NumberOfStoresToPredicate || !isSafePtr ||
+          !isSinglePredecessor) {
+        // Build a masked store if it is legal for the target, otherwise scalarize
+        // the block.
+        bool isLegalMaskedOp =
+          isLegalMaskedStore(SI->getValueOperand()->getType(),
+                             SI->getPointerOperand());
+        if (isLegalMaskedOp) {
+          --NumPredStores;
+          MaskedOp.insert(SI);
+          continue;
+        }
         return false;
+      }
     }
     if (it->mayThrow())
       return false;
 
-    // Check that we don't have a constant expression that can trap as operand.
-    for (Instruction::op_iterator OI = it->op_begin(), OE = it->op_end();
-         OI != OE; ++OI) {
-      if (Constant *C = dyn_cast<Constant>(*OI))
-        if (C->canTrap())
-          return false;
-    }
-
     // The instructions below can trap.
     switch (it->getOpcode()) {
     default: continue;