[clang] [clang][CodeGen] Set `dead_on_return` on indirect pointer arguments (PR #148159)

[Antonio Frighetto via cfe-commits]

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@@ -2852,8 +2852,17 @@ void CodeGenModule::ConstructAttributeList(StringRef Name,
       if (AI.getInReg())
         Attrs.addAttribute(llvm::Attribute::InReg);
 
-      if (AI.getIndirectByVal())
+      // Depending on the ABI, this may be either a byval or a dead_on_return
+      // argument.
+      if (AI.getIndirectByVal()) {
         Attrs.addByValAttr(getTypes().ConvertTypeForMem(ParamType));
+      } else {
+        // If the argument type has a non-trivial destructor that the caller has
+        // to invoke, this cannot be a dead_on_return argument.
+        const auto *RD = ParamType->getAsCXXRecordDecl();
+        if (!RD || (RD && RD->hasTrivialDestructor()))
+          Attrs.addAttribute(llvm::Attribute::DeadOnReturn);
+      }
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antoniofrighetto wrote:

Thank you for clarifying this, updated it. Tests updated too (it indeed looks like from the tests that some MSVC callee-destroyed objects, which are passed indirectly, should be dead_on_return. So is the case for Obj-C++ structs, as mentioned, with __weak and __strong references, as per `objc-struct-cxx-abi.mm` and `ptrauth-struct-cxx-abi.mm` tests).

https://github.com/llvm/llvm-project/pull/148159