[clang] [llvm] [Clang][AIX] Add -mloadtime-comment-vars flag to preserve identifying variables (PR #187986)

[Wael Yehia via cfe-commits]

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@@ -1077,6 +1077,13 @@ void CodeGenModule::Release() {
   Module *Primary = getContext().getCurrentNamedModule();
   if (CXX20ModuleInits && Primary && !Primary->isHeaderLikeModule())
     EmitModuleInitializers(Primary);
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w2yehia wrote:

I don't see precedence for walking the translation unit, visiting each global variable decl, during codegen.

Why don't we process the list during CodeGenModule::EmitGlobal (which I assume is called for every GlobalDecl).
1) You would teach `MustBeEmitted()` to return true (no need to return true for `MayBeEmittedEagerly()` I think because adding to `DeferredDeclToEmit` is sufficient I think) for variables whose names occur in the `LoadTimeCommentVars` list; and 
2) teach EmitGlobalVarDefinition to generate the MD if its name occurs in the `LoadTimeCommentVars` list.

Alternatively, you can create a list of variables that need the MD, but since this feature is optional, I wouldn't add a new list to `CodeGenModule`, and instead do the lookup twice (as described above) and only if the LoadTimeCommentVars is non-empty.


https://github.com/llvm/llvm-project/pull/187986