1 files changed, 51 insertions, 0 deletions
diff --git a/lib/CodeGen/CGExprScalar.cpp b/lib/CodeGen/CGExprScalar.cpp
index b1d457589d..dff7bf45e0 100644
--- a/lib/CodeGen/CGExprScalar.cpp
+++ b/lib/CodeGen/CGExprScalar.cpp
@@ -508,6 +508,7 @@ public:
   Value *VisitObjCStringLiteral(const ObjCStringLiteral *E) {
     return CGF.EmitObjCStringLiteral(E);
   }
+  Value *VisitAsTypeExpr(AsTypeExpr *CE);
 };
 }  // end anonymous namespace.
 
@@ -2545,6 +2546,56 @@ Value *ScalarExprEmitter::VisitBlockExpr(const BlockExpr *block) {
   return CGF.EmitBlockLiteral(block);
 }
 
+Value *ScalarExprEmitter::VisitAsTypeExpr(AsTypeExpr *E) {
+  Value *Src  = CGF.EmitScalarExpr(E->getSrcExpr());
+  const llvm::Type * DstTy = ConvertType(E->getDstType());
+  
+  // Going from vec4->vec3 or vec3->vec4 is a special case and requires
+  // a shuffle vector instead of a bitcast.
+  const llvm::Type *SrcTy = Src->getType();
+  if (isa<llvm::VectorType>(DstTy) && isa<llvm::VectorType>(SrcTy)) {
+    unsigned numElementsDst = cast<llvm::VectorType>(DstTy)->getNumElements();
+    unsigned numElementsSrc = cast<llvm::VectorType>(SrcTy)->getNumElements();
+    if ((numElementsDst == 3 && numElementsSrc == 4) 
+        || (numElementsDst == 4 && numElementsSrc == 3)) {
+      
+      
+      // In the case of going from int4->float3, a bitcast is needed before
+      // doing a shuffle.
+      const llvm::Type *srcElemTy = 
+      cast<llvm::VectorType>(SrcTy)->getElementType();
+      const llvm::Type *dstElemTy = 
+      cast<llvm::VectorType>(DstTy)->getElementType();
+      
+      if ((srcElemTy->isIntegerTy() && dstElemTy->isFloatTy())
+          || (srcElemTy->isFloatTy() && dstElemTy->isIntegerTy())) {
+        // Create a float type of the same size as the source or destination.
+        const llvm::VectorType *newSrcTy = llvm::VectorType::get(dstElemTy,
+                                                                 numElementsSrc);
+        
+        Src = Builder.CreateBitCast(Src, newSrcTy, "astypeCast");
+      }
+      
+      llvm::Value *UnV = llvm::UndefValue::get(Src->getType());
+      
+      llvm::SmallVector<llvm::Constant*, 3> Args;
+      Args.push_back(Builder.getInt32(0));
+      Args.push_back(Builder.getInt32(1));
+      Args.push_back(Builder.getInt32(2));
+ 
+      if (numElementsDst == 4)
+        Args.push_back(llvm::UndefValue::get(
+                                             llvm::Type::getInt32Ty(CGF.getLLVMContext())));
+      
+      llvm::Constant *Mask = llvm::ConstantVector::get(Args);
+      
+      return Builder.CreateShuffleVector(Src, UnV, Mask, "astype");
+    }
+  }
+  
+  return Builder.CreateBitCast(Src, DstTy, "astype");
+}
+
 //===----------------------------------------------------------------------===//
 //                         Entry Point into this File
 //===----------------------------------------------------------------------===//