[PATCH] D135370: Narrow inline namespace filtration for unqualified friend declarations

[Troy Johnson via Phabricator via cfe-commits]

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rG04ba1856 <https://reviews.llvm.org/rG04ba18563390ec87400fa068a9b4981b235ebaa6> introduced a call to FilterLookupForScope that is expensive for very large translation units where it was observed to cause a 6% compile time degradation. As the comment states, the only effect is to "remove declarations found in inline namespaces for friend declarations with unqualified names." This change limits the call to that scenario. The test that was added by rG04ba1856 <https://reviews.llvm.org/rG04ba18563390ec87400fa068a9b4981b235ebaa6> continues to pass, but the observed degradation is cut in half.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D135370

Files:
  clang/lib/Sema/SemaTemplateInstantiateDecl.cpp


Index: clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
===================================================================
--- clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -2170,9 +2170,11 @@
     // Filter out previous declarations that don't match the scope. The only
     // effect this has is to remove declarations found in inline namespaces
     // for friend declarations with unqualified names.
-    SemaRef.FilterLookupForScope(Previous, DC, /*Scope*/ nullptr,
-                                 /*ConsiderLinkage*/ true,
-                                 QualifierLoc.hasQualifier());
+    if (isFriend && !QualifierLoc && !FunctionTemplate) {
+      SemaRef.FilterLookupForScope(Previous, DC, /*Scope*/ nullptr,
+                                   /*ConsiderLinkage*/ true,
+                                   QualifierLoc.hasQualifier());
+    }
   }
 
   SemaRef.CheckFunctionDeclaration(/*Scope*/ nullptr, Function, Previous,


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