Don't use isNullValue to evaluate ConstantExpr

[oota-llvm.git] / lib / Transforms / InstCombine / InstCombineVectorOps.cpp

diff --git a/lib/Transforms/InstCombine/InstCombineVectorOps.cpp b/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
index ffab87faf6889bb812820e0c6046ff7f8a0b4101..1e724106991a4c879eaad39aa659bb97086a7d50 100644 (file)
--- a/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
+++ b/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
@@ -106,8 +106,8 @@ static Value *FindScalarElement(Value *V, unsigned EltNo) {
 }
 
 // If we have a PHI node with a vector type that has only 2 uses: feed
-// itself and be an operand of extractelemnt at a constant location,
-// try to replace the PHI of the vector type with a PHI of a scalar type
+// itself and be an operand of extractelement at a constant location,
+// try to replace the PHI of the vector type with a PHI of a scalar type.
 Instruction *InstCombiner::scalarizePHI(ExtractElementInst &EI, PHINode *PN) {
   // Verify that the PHI node has exactly 2 uses. Otherwise return NULL.
   if (!PN->hasNUses(2))
@@ -282,6 +282,38 @@ Instruction *InstCombiner::visitExtractElementInst(ExtractElementInst &EI) {
         Worklist.AddValue(EE);
         return CastInst::Create(CI->getOpcode(), EE, EI.getType());
       }
+    } else if (SelectInst *SI = dyn_cast<SelectInst>(I)) {
+      if (SI->hasOneUse()) {
+        // TODO: For a select on vectors, it might be useful to do this if it
+        // has multiple extractelement uses. For vector select, that seems to
+        // fight the vectorizer.
+
+        // If we are extracting an element from a vector select or a select on
+        // vectors, a select on the scalars extracted from the vector arguments.
+        Value *TrueVal = SI->getTrueValue();
+        Value *FalseVal = SI->getFalseValue();
+
+        Value *Cond = SI->getCondition();
+        if (Cond->getType()->isVectorTy()) {
+          Cond = Builder->CreateExtractElement(Cond,
+                                               EI.getIndexOperand(),
+                                               Cond->getName() + ".elt");
+        }
+
+        Value *V1Elem
+          = Builder->CreateExtractElement(TrueVal,
+                                          EI.getIndexOperand(),
+                                          TrueVal->getName() + ".elt");
+
+        Value *V2Elem
+          = Builder->CreateExtractElement(FalseVal,
+                                          EI.getIndexOperand(),
+                                          FalseVal->getName() + ".elt");
+        return SelectInst::Create(Cond,
+                                  V1Elem,
+                                  V2Elem,
+                                  SI->getName() + ".elt");
+      }
     }
   }
   return 0;
@@ -294,7 +326,7 @@ static bool CollectSingleShuffleElements(Value *V, Value *LHS, Value *RHS,
                                          SmallVectorImpl<Constant*> &Mask) {
   assert(V->getType() == LHS->getType() && V->getType() == RHS->getType() &&
          "Invalid CollectSingleShuffleElements");
-  unsigned NumElts = cast<VectorType>(V->getType())->getNumElements();
+  unsigned NumElts = V->getType()->getVectorNumElements();
 
   if (isa<UndefValue>(V)) {
     Mask.assign(NumElts, UndefValue::get(Type::getInt32Ty(V->getContext())));
@@ -497,7 +529,7 @@ Instruction *InstCombiner::visitInsertElementInst(InsertElementInst &IE) {
 /// Return true if we can evaluate the specified expression tree if the vector
 /// elements were shuffled in a different order.
 static bool CanEvaluateShuffled(Value *V, ArrayRef<int> Mask,
-                                unsigned Depth = 100) {
+                                unsigned Depth = 5) {
   // We can always reorder the elements of a constant.
   if (isa<Constant>(V))
     return true;
@@ -717,14 +749,27 @@ InstCombiner::EvaluateInDifferentElementOrder(Value *V, ArrayRef<int> Mask) {
       return I;
     }
     case Instruction::InsertElement: {
-      uint32_t Element = cast<ConstantInt>(I->getOperand(2))->getLimitedValue();
-      if (Element >= Mask.size()) {
-        // Such instructions are valid and exhibit undefined behaviour.
-        return UndefValue::get(I->getType());
+      int Element = cast<ConstantInt>(I->getOperand(2))->getLimitedValue();
+
+      // The insertelement was inserting at Element. Figure out which element
+      // that becomes after shuffling. The answer is guaranteed to be unique
+      // by CanEvaluateShuffled.
+      bool Found = false;
+      int Index = 0;
+      for (int e = Mask.size(); Index != e; ++Index) {
+        if (Mask[Index] == Element) {
+          Found = true;
+          break;
+        }
       }
+
+      if (!Found)
+        return UndefValue::get(
+            VectorType::get(V->getType()->getScalarType(), Mask.size()));
+
       Value *V = EvaluateInDifferentElementOrder(I->getOperand(0), Mask);
       return InsertElementInst::Create(V, I->getOperand(1),
-                                       Builder->getInt32(Mask[Element]), "", I);
+                                       Builder->getInt32(Index), "", I);
     }
   }
   llvm_unreachable("failed to reorder elements of vector instruction!");
@@ -760,9 +805,9 @@ Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
   if (LHS == RHS || isa<UndefValue>(LHS)) {
     if (isa<UndefValue>(LHS) && LHS == RHS) {
       // shuffle(undef,undef,mask) -> undef.
-      Value* result = (VWidth == LHSWidth)
+      Value *Result = (VWidth == LHSWidth)
                       ? LHS : UndefValue::get(SVI.getType());
-      return ReplaceInstUsesWith(SVI, result);
+      return ReplaceInstUsesWith(SVI, Result);
     }
 
     // Remap any references to RHS to use LHS.
@@ -809,12 +854,7 @@ Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
     if (isRHSID) return ReplaceInstUsesWith(SVI, RHS);
   }
 
-  if (isa<UndefValue>(RHS) &&
-      // This isn't necessary for correctness, but the comment block below
-      // claims that there are cases where folding two shuffles into one would
-      // cause worse codegen on some targets.
-      !isa<ShuffleVectorInst>(LHS) &&
-      CanEvaluateShuffled(LHS, Mask)) {
+  if (isa<UndefValue>(RHS) && CanEvaluateShuffled(LHS, Mask)) {
     Value *V = EvaluateInDifferentElementOrder(LHS, Mask);
     return ReplaceInstUsesWith(SVI, V);
   }