[clang] [llvm] [PowerPC][AIX] Support #pragma comment copyright for AIX (PR #178184)

[Hubert Tong via llvm-commits]

================
@@ -3572,6 +3574,47 @@ void CodeGenModule::AddDependentLib(StringRef Lib) {
   LinkerOptionsMetadata.push_back(llvm::MDNode::get(C, MDOpts));
 }
 
+/// Process copyright pragma and create LLVM metadata.
+/// #pragma comment(copyright, "string") embeds copyright information into a
+/// loadable program-data section of the object file for inclusion in the linked
+/// module.
+///
+/// Example: #pragma comment(copyright, "Copyright string")
+///
+/// Only one copyright pragma is allowed per translation unit. Subsequent
+/// pragmas in the same TU are ignored with a warning at the parse level.
+void CodeGenModule::ProcessPragmaComment(PragmaMSCommentKind Kind,
+                                         StringRef Comment,
+                                         bool isFromASTFile) {
+  // Ensure we are only processing Copyright Pragmas
+  assert(Kind == PCK_Copyright &&
+         "Unexpected pragma comment kind, ProcessPragmaComment should only be "
+         "called for PCK_Copyright");
+  // Target Guard: Only AIX supports PCK_Copyright currently.
+  assert(getTriple().isOSAIX() &&
+         "pragma comment copyright is supported only when targeting AIX");
+
+  // Interaction with C++20 Modules and PCH:
+  // When a module interface unit containing a copyright pragma is imported,
+  // Clang deserializes the PragmaCommentDecl from the precompiled module file
+  // (.pcm) into the importing TU's AST. isFromASTFile() returns true for such
+  // deserialized declarations. We skip those to ensure only the module
+  // interface TU that originally parsed the pragma emits the copyright metadata
+  // -- not every TU that imports it. This prevents duplicate copyright strings
+  // in the final binary.
+  if (isFromASTFile)
+    return;
+
+  // Only one copyright pragma allowed per translation unit
----------------
hubert-reinterpretcast wrote:

Let us not have a comment to explain an assertion that explains itself.
```suggestion
```

https://github.com/llvm/llvm-project/pull/178184