Fix creating bitcasts with wrong address space

[arsenm]

Summary

In a future commit AMDGPU will start passing
aggregates directly to more functions, triggering
asserts in test/CodeGenOpenCL/addr-space-struct-arg.cl

[yaxunl]

LGTM. Thanks.

[arsenm]

r309741

lib/CodeGen/CGCall.cpp

static llvm::Value *CreateCoercedLoad(Address Src, llvm::Type *Ty,
   // If load is legal, just bitcast the src pointer.
   if (SrcSize >= DstSize) {
     // Generally SrcSize is never greater than DstSize, since this means we are
     // losing bits. However, this can happen in cases where the structure has
     // additional padding, for example due to a user specified alignment.
     //
     // FIXME: Assert that we aren't truncating non-padding bits when have access
     // to that information.
-    Src = CGF.Builder.CreateBitCast(Src, llvm::PointerType::getUnqual(Ty));
+    Src = CGF.Builder.CreateBitCast(Src,
+                                    Ty->getPointerTo(Src.getAddressSpace()));
     return CGF.Builder.CreateLoad(Src);
   }
 
   // Otherwise do coercion through memory. This is stupid, but simple.
   Address Tmp = CreateTempAllocaForCoercion(CGF, Ty, Src.getAlignment());
   Address Casted = CGF.Builder.CreateBitCast(Tmp, CGF.Int8PtrTy);
   Address SrcCasted = CGF.Builder.CreateBitCast(Src, CGF.Int8PtrTy);
   CGF.Builder.CreateMemCpy(Casted, SrcCasted,
case ABIArgInfo::Direct: {
         // the source value are left undef.
         if (SrcSize < DstSize) {
           Address TempAlloca
             = CreateTempAlloca(STy, Src.getAlignment(),
                                Src.getName() + ".coerce");
           Builder.CreateMemCpy(TempAlloca, Src, SrcSize);
           Src = TempAlloca;
         } else {
-          Src = Builder.CreateBitCast(Src, llvm::PointerType::getUnqual(STy));
+          Src = Builder.CreateBitCast(Src,
+                                      STy->getPointerTo(Src.getAddressSpace()));
         }
 
         auto SrcLayout = CGM.getDataLayout().getStructLayout(STy);
         assert(NumIRArgs == STy->getNumElements());
         for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
           auto Offset = CharUnits::fromQuantity(SrcLayout->getElementOffset(i));
           Address EltPtr = Builder.CreateStructGEP(Src, i, Offset);
           llvm::Value *LI = Builder.CreateLoad(EltPtr);