rmaz added a comment. In D109632#3000469 <https://reviews.llvm.org/D109632#3000469>, @vsapsai wrote:
> I'm a little bit confused here. Where is the speed-up coming from? Is it > because ObjCMethodList for `init` not being serialized? I'm asking because > right now I don't see how `seen` helps with that. > > My current understanding is that `Sema::addMethodToGlobalList` is too > expensive and `seen` reduces the number of calls to it. So maybe it makes > sense to invest into making it faster? For example, > `Sema::MatchTwoMethodDeclarations` can return early if both method decl > pointers are equal. But I haven't done any measurements, that's just an > example. The speedup is coming from reducing the number of times `Sema::addMethodToGlobalList` is called when looking up methods loaded from modules. From what I can see each serialized module will contain an ObjCMethodList with all the methods from all visible modules at the point of serialization. This means that if you have a lot of modules that redeclare `-(id)init`, which is a common pattern in our code, then each serialized module will contain a lot of shared method decls, which we do not de-duplicate. To illustrate this, here are the top 5 instance method counts sorted by amount of duplicates (using pointer comparison) from a pass of the `ReadMethodPoolVisitor` for a single file: | **selector** | **# methods** | **# unique** | **# duplicated** | | init | 9825 | 1652 | 8173 | | init | 2155 | 930 | 1225 | | copy | 1398 | 633 | 765 | | init | 1027 | 270 | 757 | | init | 948 | 410 | 538 | | Without having a set to deduplicate I'm not sure how we could make `Sema::addMethodToGlobalList` fast enough, wouldn't it require a list traversal for each insert, making it O(n^2)? Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D109632/new/ https://reviews.llvm.org/D109632 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
