diff --git a/lib/CodeGen/ABIInfo.h b/lib/CodeGen/ABIInfo.h
index 1ab2f55..c1efd05 100644
--- a/lib/CodeGen/ABIInfo.h
+++ b/lib/CodeGen/ABIInfo.h
@@ -136,7 +136,11 @@
 
     virtual void computeInfo(CodeGen::CGFunctionInfo &FI,
                              ASTContext &Ctx,
-                             llvm::LLVMContext &VMContext) const = 0;
+                             llvm::LLVMContext &VMContext,
+                             // This is the preferred type for argument lowering
+                             // which can be used to generate better IR.
+                             const llvm::Type *const *PrefTypes = 0,
+                             unsigned NumPrefTypes = 0) const = 0;
 
     /// EmitVAArg - Emit the target dependent code to load a value of
     /// \arg Ty from the va_list pointed to by \arg VAListAddr.
diff --git a/lib/CodeGen/CGCall.cpp b/lib/CodeGen/CGCall.cpp
index 7ade427..d7a03c9 100644
--- a/lib/CodeGen/CGCall.cpp
+++ b/lib/CodeGen/CGCall.cpp
@@ -244,8 +244,16 @@
                           ArgTys);
   FunctionInfos.InsertNode(FI, InsertPos);
 
+  // ABI lowering wants to know what our preferred type for the argument is in
+  // various situations, pass it in.
+  llvm::SmallVector<const llvm::Type *, 8> PreferredArgTypes;
+  for (llvm::SmallVectorImpl<CanQualType>::const_iterator
+       I = ArgTys.begin(), E = ArgTys.end(); I != E; ++I)
+    PreferredArgTypes.push_back(ConvertType(*I));
+
   // Compute ABI information.
-  getABIInfo().computeInfo(*FI, getContext(), TheModule.getContext());
+  getABIInfo().computeInfo(*FI, getContext(), TheModule.getContext(),
+                           PreferredArgTypes.data(), PreferredArgTypes.size());
 
   return *FI;
 }
diff --git a/lib/CodeGen/TargetInfo.cpp b/lib/CodeGen/TargetInfo.cpp
index 80163b3..3bdfbf6 100644
--- a/lib/CodeGen/TargetInfo.cpp
+++ b/lib/CodeGen/TargetInfo.cpp
@@ -280,7 +280,9 @@
                                   llvm::LLVMContext &VMContext) const;
 
   virtual void computeInfo(CGFunctionInfo &FI, ASTContext &Context,
-                           llvm::LLVMContext &VMContext) const {
+                           llvm::LLVMContext &VMContext,
+                           const llvm::Type *const *PrefTypes,
+                           unsigned NumPrefTypes) const {
     FI.getReturnInfo() = classifyReturnType(FI.getReturnType(), Context,
                                             VMContext);
     for (CGFunctionInfo::arg_iterator it = FI.arg_begin(), ie = FI.arg_end();
@@ -347,7 +349,9 @@
                                   llvm::LLVMContext &VMContext) const;
 
   virtual void computeInfo(CGFunctionInfo &FI, ASTContext &Context,
-                           llvm::LLVMContext &VMContext) const {
+                           llvm::LLVMContext &VMContext,
+                           const llvm::Type *const *PrefTypes,
+                           unsigned NumPrefTypes) const {
     FI.getReturnInfo() = classifyReturnType(FI.getReturnType(), Context,
                                             VMContext);
     for (CGFunctionInfo::arg_iterator it = FI.arg_begin(), ie = FI.arg_end();
@@ -747,7 +751,9 @@
 
 public:
   virtual void computeInfo(CGFunctionInfo &FI, ASTContext &Context,
-                           llvm::LLVMContext &VMContext) const;
+                           llvm::LLVMContext &VMContext,
+                           const llvm::Type *const *PrefTypes,
+                           unsigned NumPrefTypes) const;
 
   virtual llvm::Value *EmitVAArg(llvm::Value *VAListAddr, QualType Ty,
                                  CodeGenFunction &CGF) const;
@@ -1373,7 +1379,9 @@
 }
 
 void X86_64ABIInfo::computeInfo(CGFunctionInfo &FI, ASTContext &Context,
-                                llvm::LLVMContext &VMContext) const {
+                                llvm::LLVMContext &VMContext,
+                                const llvm::Type *const *PrefTypes,
+                                unsigned NumPrefTypes) const {
   FI.getReturnInfo() = classifyReturnType(FI.getReturnType(),
                                           Context, VMContext);
 
@@ -1635,7 +1643,9 @@
                                   llvm::LLVMContext &VMContext) const;
 
   virtual void computeInfo(CGFunctionInfo &FI, ASTContext &Context,
-                           llvm::LLVMContext &VMContext) const {
+                           llvm::LLVMContext &VMContext,
+                           const llvm::Type *const *PrefTypes,
+                           unsigned NumPrefTypes) const {
     FI.getReturnInfo() = classifyReturnType(FI.getReturnType(), Context,
                                             VMContext);
     for (CGFunctionInfo::arg_iterator it = FI.arg_begin(), ie = FI.arg_end();
@@ -1786,7 +1796,9 @@
                                   llvm::LLVMContext &VMContext) const;
 
   virtual void computeInfo(CGFunctionInfo &FI, ASTContext &Context,
-                           llvm::LLVMContext &VMContext) const;
+                           llvm::LLVMContext &VMContext,
+                           const llvm::Type *const *PrefTypes,
+                           unsigned NumPrefTypes) const;
 
   virtual llvm::Value *EmitVAArg(llvm::Value *VAListAddr, QualType Ty,
                                  CodeGenFunction &CGF) const;
@@ -1805,7 +1817,9 @@
 }
 
 void ARMABIInfo::computeInfo(CGFunctionInfo &FI, ASTContext &Context,
-                             llvm::LLVMContext &VMContext) const {
+                             llvm::LLVMContext &VMContext,
+                             const llvm::Type *const *PrefTypes,
+                             unsigned NumPrefTypes) const {
   FI.getReturnInfo() = classifyReturnType(FI.getReturnType(), Context,
                                           VMContext);
   for (CGFunctionInfo::arg_iterator it = FI.arg_begin(), ie = FI.arg_end();
@@ -2088,7 +2102,9 @@
                                   llvm::LLVMContext &VMContext) const;
 
   virtual void computeInfo(CGFunctionInfo &FI, ASTContext &Context,
-                          llvm::LLVMContext &VMContext) const {
+                          llvm::LLVMContext &VMContext,
+                           const llvm::Type *const *PrefTypes,
+                           unsigned NumPrefTypes) const {
     FI.getReturnInfo() = classifyReturnType(FI.getReturnType(),
                                             Context, VMContext);
     for (CGFunctionInfo::arg_iterator it = FI.arg_begin(), ie = FI.arg_end();