[PATCH] D70172: [CUDA][HIP][OpenMP] Emit deferred diagnostics by a post-parsing AST travese

[John McCall via Phabricator via cfe-commits]

rjmccall added inline comments.


================
Comment at: clang/lib/Sema/Sema.cpp:1514
+  void visitUsedDecl(SourceLocation Loc, Decl *D) {
+    if (auto *TD = dyn_cast<TranslationUnitDecl>(D)) {
+      for (auto *DD : TD->decls()) {
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erichkeane wrote:
> rjmccall wrote:
> > erichkeane wrote:
> > > Note that when recommitting this (if you choose to), this needs to also handle NamespaceDecl.  We're a downstream and discovered that this doesn't properly handle functions or records handled in a namespace.
> > > 
> > > It can be implemented identically to TranslationUnitDecl.
> > Wait, what?  We shouldn't be doing this for TranslationUnitDecl either.   I don't even know how we're "using" a TranslationUnitDecl, but neither this case not the case for `NamespaceDecl` should be recursively using every declaration declared inside it.  If there's a declaration in a namespace that's being used, it should be getting visited as part of the actual use of it.
> > 
> > The logic for `RecordDecl` has the same problem.  
> Despite the name, this seems to be more of a home-written ast walking class.  The entry point is the 'translation unit' which seems to walk through everything in an attempt to find all the functions (including those that are 'marked' as used by an attribute).
> 
> You'll see the FunctionDecl section makes this assumption as well (not necessarily that we got to a function via a call). IMO, this approach is strange, and we should register entry points in some manner (functions marked as emitted to the device in some fashion), then just follow its call-graph (via the clang::CallGraph?) to emit all of these functions.
> 
> It seemed really odd to see this approach here, but it seemed well reviewed by the time I noticed it (via a downstream bug) so I figured I'd lost my chance to disagree with the approach.
> 
> 
Sure, but `visitUsedDecl` isn't the right place to be entering the walk.  `visitUsedDecl` is supposed to be the *callback* from the walk.  If they need to walk all the global declarations to find kernels instead of tracking the kernels as they're encountered (which would be a *much* better approach), it should be done as a separate function.

I just missed this in the review.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D70172/new/

https://reviews.llvm.org/D70172