[clang] [clang][CodeGen] `sret` args should always point to the `alloca` AS, so use that (PR #114062)

[Alex Voicu via cfe-commits]

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@@ -49,6 +49,8 @@ class ABIInfo {
   CodeGen::CodeGenTypes &CGT;
   llvm::CallingConv::ID RuntimeCC;
 
+  unsigned getTargetDefaultAS() const;
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AlexVlx wrote:

Sure, but I couldn't quite figure out any other convenient, accessible, non-intrusive place to stash this; the alternative is to keep the spammy calls to `getContext().bla`, as per the prior iteration. I'm open to suggestions though, if you have something in mind?

https://github.com/llvm/llvm-project/pull/114062