[PATCH] D133945: [clang][ASTImporter] Continue with slow lookup in DeclContext::localUncachedLookup when regular lookup fails

[Michael Buch via Phabricator via cfe-commits]

Michael137 created this revision.
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The uncached lookup is mainly used in the ASTImporter/LLDB code-path
where we're not allowed to load from external storage. When importing
a FieldDecl with a DeclContext that had no external visible storage
(but came from a Clang module or PCH) the above call to `lookup(Name)`
the regular lookup fails because:

1. `DeclContext::buildLookup` doesn't set `LookupPtr` for decls that came from a module
2. LLDB doesn't use the `SharedImporterState`

In such a case but we would never go on to the "slow" path of iterating
through the decls in the DeclContext. In some cases this means that
`ASTNodeImporter::VisitFieldDecl` ends up importing a decl into the
`DeclContext` a second time.

The patch removes the short-circuit in the case where we don't find
any decls via the regular lookup.

**Tests**

- Un-skip the failing LLDB API tests


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D133945

Files:
  clang/lib/AST/DeclBase.cpp
  clang/unittests/AST/ASTImporterTest.cpp
  lldb/test/API/lang/cpp/gmodules/base-template-with-same-arg/TestBaseTemplateWithSameArg.py


Index: lldb/test/API/lang/cpp/gmodules/base-template-with-same-arg/TestBaseTemplateWithSameArg.py
===================================================================
--- lldb/test/API/lang/cpp/gmodules/base-template-with-same-arg/TestBaseTemplateWithSameArg.py
+++ lldb/test/API/lang/cpp/gmodules/base-template-with-same-arg/TestBaseTemplateWithSameArg.py
@@ -30,7 +30,6 @@
 class TestBaseTemplateWithSameArg(TestBase):
 
     @add_test_categories(["gmodules"])
-    @skipIf(bugnumber='rdar://96581048')
     def test_same_base_template_arg(self):
         self.build()
 
Index: clang/unittests/AST/ASTImporterTest.cpp
===================================================================
--- clang/unittests/AST/ASTImporterTest.cpp
+++ clang/unittests/AST/ASTImporterTest.cpp
@@ -4924,9 +4924,9 @@
   FooDC->getRedeclContext()->localUncachedLookup(FooName, FoundDecls);
   EXPECT_EQ(FoundDecls.size(), 0u);
 
-  // Cannot find in the LookupTable of its LexicalDC (A).
+  // Finds via linear search of its LexicalDC (A).
   FooLexicalDC->getRedeclContext()->localUncachedLookup(FooName, FoundDecls);
-  EXPECT_EQ(FoundDecls.size(), 0u);
+  EXPECT_EQ(FoundDecls.size(), 1u);
 
   // Can't find in the list of Decls of the DC.
   EXPECT_EQ(findInDeclListOfDC(FooDC, FooName), nullptr);
Index: clang/lib/AST/DeclBase.cpp
===================================================================
--- clang/lib/AST/DeclBase.cpp
+++ clang/lib/AST/DeclBase.cpp
@@ -1771,7 +1771,8 @@
   if (!hasExternalVisibleStorage() && !hasExternalLexicalStorage() && Name) {
     lookup_result LookupResults = lookup(Name);
     Results.insert(Results.end(), LookupResults.begin(), LookupResults.end());
-    return;
+    if (!Results.empty())
+      return;
   }
 
   // If we have a lookup table, check there first. Maybe we'll get lucky.


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