[clang] [clang][CodeGen][OpenCL] Fix `alloca` handling & `sret`when compiling for (PR #113930)

[Matt Arsenault via cfe-commits]

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@@ -1648,6 +1648,8 @@ CodeGenTypes::GetFunctionType(const CGFunctionInfo &FI) {
   // Add type for sret argument.
   if (IRFunctionArgs.hasSRetArg()) {
     QualType Ret = FI.getReturnType();
+    if (CGM.getLangOpts().OpenCL)
+      Ret = getContext().getAddrSpaceQualType(Ret, LangAS::opencl_private);
     unsigned AddressSpace = CGM.getTypes().getTargetAddressSpace(Ret);
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arsenm wrote:

This seems like extra steps around directly calling getContext().getTargetAddressSpace(LangAS::opencl_private) 

But more importantly, I would expect this to have been handled by the target API lowering code. The language wouldn't factor in 

https://github.com/llvm/llvm-project/pull/113930