rsmith added inline comments.
================
Comment at: lib/Serialization/ASTReaderDecl.cpp:213-215
+ assert(isa<RedeclarableTemplateDecl>(D) ||
+ isa<TypeAliasTemplateDecl>(D) &&
+ "Decl doesn't have specializations.");
----------------
Can this ever fail at runtime? I'd expect the below code to not compile if `D`
isn't one of these types.
================
Comment at: lib/Serialization/ASTReaderDecl.cpp:3911-3924
+ case UPD_CXX_ADDED_TEMPLATE_SPECIALIZATION: {
+ // It will be added to the template's lazy specialization set when
loaded.
+ SmallVector<serialization::DeclID, 1> SpecID;
+ SpecID.push_back(ReadDeclID());
+ if (auto *CTD = dyn_cast<ClassTemplateDecl>(D))
+ AddLazySpecializations(CTD, SpecID);
+ else if (auto *FTD = dyn_cast<FunctionTemplateDecl>(D))
----------------
This will end up being quadratic time and using quadratic storage if a module
adds N specializations to a template; instead, please move the SmallVector out
of the loop and call `AddLazySpecializations` once after reading all the update
records for the declaration. (It's probably best to move it all the way out to
`loadDeclUpdateRecords`, in case we have a large number of modules each adding
some specializations -- eg, if module A imports std::vector and declares A,
module B declares B and uses vector<A>, module C declares C and uses vector<B>,
..., we again should avoid quadratic behavior.)
https://reviews.llvm.org/D29951
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