[PATCH] D45815: [libclang] Add options to limit skipping of function bodies

[Nikolai Kosjar via Phabricator via cfe-commits]

nik added a comment.

In https://reviews.llvm.org/D45815#1073418, @ilya-biryukov wrote:

> In https://reviews.llvm.org/D45815#1072094, @nik wrote:
>
> > @ilya: Using SkipFunctionBodies_AllExceptTemplates for the preamble might be also useful for clangd.
>
>
> Unfortunately, that's also the biggest performance win you get when skipping the function bodies.
>  I.e. most codebases do not have function bodies in headers unless the function is template.
>
> Have you measured the performance gain of skipping only non-template functions, but not skipping the template ones?
>  Would that really make a significant difference for any real codebase?


Here are some rough numbers, based on LIBCLANG_TIMING=1 output: https://dpaste.de/os39/raw

Reparses of Qt Creator's texteditor.cpp
	Without any skipping of function bodies in the preamble: 1.9s
	Skipping all function bodies in the preamble: 1.0s
	Skipping all function bodies in the preamble except function template bodies: 1.2s

Reparses of Clang's SemaDecl.cpp
	Without any skipping of function bodies in the preamble: 1.7s
	Skipping all function bodies in the preamble: 0.59s
	Skipping all function bodies in the preamble except function template bodies: 0.64s

Hmm, that indicates that template function bodies are actually not that
dominant, which I also haven't thought. Now I'm doubting the correctness of
my patch/tests.

I'll recheck this on Tuesday. Until then, you/someone might want to give this also a shot.



================
Comment at: include/clang/Frontend/SkipFunctionBodies.h:18
+enum SkipFunctionBodiesKind {
+  SkipFunctionBodies_None,
+  SkipFunctionBodies_All,
----------------
ilya-biryukov wrote:
> Maybe make it `enum class` and remove the name prefix from enumerators?
> I.e.  `enum class SkipFunctionBodiesKind { None, ....`
Will do.


Repository:
  rC Clang

https://reviews.llvm.org/D45815