CodeGen: Fix TargetLowering::LowerCallTo for sret value type

[yaxunl]

Summary

TargetLowering::LowerCallTo assumes that sret value type corresponds to a
pointer in default address space, which is incorrect, since sret value type
should correspond to a pointer in alloca address space, which may not
be the default address space. This causes assertion for amdgcn target
in amdgiz environment.

This patch fixes that.

[arsenm]

LGTM

llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

#ifndef NDEBUG
   }
 #endif
 
   SmallVector<SDValue, 4> ReturnValues;
   if (!CanLowerReturn) {
     // The instruction result is the result of loading from the
     // hidden sret parameter.
     SmallVector<EVT, 1> PVTs;
-    Type *PtrRetTy = PointerType::getUnqual(OrigRetTy);
+    Type *PtrRetTy = OrigRetTy->getPointerTo(DL.getAllocaAddrSpace());
 
     ComputeValueVTs(*this, DL, PtrRetTy, PVTs);
     assert(PVTs.size() == 1 && "Pointers should fit in one register");
     EVT PtrVT = PVTs[0];
 
     unsigned NumValues = RetTys.size();
     ReturnValues.resize(NumValues);
     SmallVector<SDValue, 4> Chains(NumValues);

llvm/trunk/test/CodeGen/AMDGPU/call-return-types.ll

-; RUN: llc -mtriple=amdgcn-amd-amdhsa -mcpu=fiji -mattr=-flat-for-global -verify-machineinstrs < %s | FileCheck -check-prefix=GCN %s
-; RUN: llc -mtriple=amdgcn-amd-amdhsa -mcpu=hawaii -verify-machineinstrs < %s | FileCheck -check-prefix=GCN %s
-; RUN: llc -mtriple=amdgcn-amd-amdhsa -mcpu=gfx900 -mattr=-flat-for-global -verify-machineinstrs < %s | FileCheck -check-prefix=GCN %s
+; RUN: llc -mtriple=amdgcn-amd-amdhsa-amdgiz -mcpu=fiji -mattr=-flat-for-global -verify-machineinstrs < %s | FileCheck -check-prefix=GCN %s
+; RUN: llc -mtriple=amdgcn-amd-amdhsa-amdgiz -mcpu=hawaii -verify-machineinstrs < %s | FileCheck -check-prefix=GCN %s
+; RUN: llc -mtriple=amdgcn-amd-amdhsa-amdgiz -mcpu=gfx900 -mattr=-flat-for-global -verify-machineinstrs < %s | FileCheck -check-prefix=GCN %s
 
 declare void @external_void_func_void() #0
 
 declare i1 @external_i1_func_void() #0
 declare zeroext i1 @external_i1_zeroext_func_void() #0
 declare signext i1 @external_i1_signext_func_void() #0
 
 declare i8 @external_i8_func_void() #0