[PATCH] D52267: [AST] Various optimizations + refactoring in DeclarationName(Table)

[Bruno Ricci via Phabricator via cfe-commits]

riccibruno added a comment.

Addressed some inline comments.



================
Comment at: include/clang/AST/DeclarationName.h:46
 
-/// DeclarationName - The name of a declaration. In the common case,
-/// this just stores an IdentifierInfo pointer to a normal
-/// name. However, it also provides encodings for Objective-C
-/// selectors (optimizing zero- and one-argument selectors, which make
-/// up 78% percent of all selectors in Cocoa.h) and special C++ names
-/// for constructors, destructors, and conversion functions.
+namespace detail {
+
----------------
rjmccall wrote:
> Should `DeclarationNameExtra` be moved here?  I'm not sure why it's in `IdentifierTable.h` in the first place, and your refactor seems to make that even more pointless.
`DeclarationNameExtra` is unfortunately needed by `MultiKeywordSelector`
in `IdentifierInfo.cpp`.


================
Comment at: include/clang/AST/DeclarationName.h:164
+    CXXUsingDirective = 10,
+    ObjCMultiArgSelector = 11
+  };
----------------
rjmccall wrote:
> Is the criterion for inclusion in the first seven really just frequency of use, or is it a combination of that and relative benefit?
> 
> The only one I would really quibble about is that multi-argument selectors are probably more common and important to Objective-C code than conversion operators are to C++.  But it's quite possible that the relative benefit is much higher for C++, since selectors only appear on specific kinds of declarations that know they're declared with selectors — relatively little code actually needs to be polymorphic about them — and since they have to be defined out-of-line.
I did not do an in-depth analysis regarding the selection of the first seven inline kinds.
My thought process was that C++ constructors and operator names should definitely be
inline. C++ destructors seemed much more frequent than c++ literal operators and
deduction guides. This leaves one slot available and since C++ conversion operators
share the same class `CXXSpecialName` including it as an inline kind simplifies the code.

Also a practical point is that I don't really have a representative sample of ObjC code
to benchmark this. For C++ I am using all of Boost which I hope is representative
enough. If you deem it necessary I will try to do some benchmarks with
`ObjCMultiArgSelector` stored inline.


Repository:
  rC Clang

https://reviews.llvm.org/D52267