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

[John McCall via cfe-commits]

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@@ -1672,10 +1672,11 @@ CodeGenTypes::GetFunctionType(const CGFunctionInfo &FI) {
 
   // Add type for sret argument.
   if (IRFunctionArgs.hasSRetArg()) {
-    QualType Ret = FI.getReturnType();
-    unsigned AddressSpace = CGM.getTypes().getTargetAddressSpace(Ret);
+    auto AddressSpace = CGM.getTarget().getIndirectArgAddressSpace();
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rjmccall wrote:

That's what I was thinking, yeah.  There should be plenty of space for that without inflating `ABIInfo`, right?

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