Add query for a possible target specific indirect arg AS.

Author: AlexVlx

clang/include/clang/Basic/TargetInfo.h

@@ -1780,6 +1780,14 @@ class TargetInfo : public TransferrableTargetInfo,
     return 0;
   }
 
+  /// \returns Target specific address space for indirect (e.g. sret) arguments.
+  /// If such an address space exists, it must be convertible to and from the
+  /// alloca address space. If it does not, std::nullopt is returned and the
+  /// alloca address space will be used.
+  virtual std::optional<unsigned> getIndirectArgAddressSpace() const {
+    return std::nullopt;
+  }
+
   /// \returns If a target requires an address within a target specific address
   /// space \p AddressSpace to be converted in order to be used, then return the
   /// corresponding target specific DWARF address space.

clang/lib/CodeGen/CGCall.cpp

@@ -1672,9 +1672,11 @@ CodeGenTypes::GetFunctionType(const CGFunctionInfo &FI) {
 
   // Add type for sret argument.
   if (IRFunctionArgs.hasSRetArg()) {
-    unsigned AddressSpace = CGM.getDataLayout().getAllocaAddrSpace();
+    auto AddressSpace = CGM.getTarget().getIndirectArgAddressSpace();
+    if (!AddressSpace)
+      AddressSpace = getDataLayout().getAllocaAddrSpace();
     ArgTypes[IRFunctionArgs.getSRetArgNo()] =
-        llvm::PointerType::get(getLLVMContext(), AddressSpace);
+        llvm::PointerType::get(getLLVMContext(), *AddressSpace);
   }
 
   // Add type for inalloca argument.