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

[Alex Voicu 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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AlexVlx wrote:

That's a reasonable expectation but it's not handled at the moment, and it appears that people just gave up on it and relied on the terrible PrivateIsDefault AS maps. I'm not really adding much functionality here, just ensuring that we can safely survive moving away from that.

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