[all-commits] [llvm/llvm-project] f1a9c4: [clangd] Skip (most) predefined macros when scanni...
Sam McCall via All-commits
all-commits at lists.llvm.org
Mon May 9 06:34:28 PDT 2022
Branch: refs/heads/main
Home: https://github.com/llvm/llvm-project
Commit: f1a9c4b717be9a9a730f837dfd70df69d1daf44f
https://github.com/llvm/llvm-project/commit/f1a9c4b717be9a9a730f837dfd70df69d1daf44f
Author: Sam McCall <sam.mccall at gmail.com>
Date: 2022-05-09 (Mon, 09 May 2022)
Changed paths:
M clang-tools-extra/clangd/Preamble.cpp
Log Message:
-----------
[clangd] Skip (most) predefined macros when scanning for preamble patching.
This is unneccesary work.
With this change, we skip generating and lexing ~10k of predefines twice.
A dumb benchmark of building a preamble for an empty file in a loop shows:
- before: 1.90ms/run
- after: 1.36ms/run
So this should be worth 0.5ms for each AST build and code completion.
There can be a functional difference, but it's very minor.
If the preamble contains e.g. `#ifndef __llvm__ ... #endif` then before we would
not take it. After this change we will take the branch (single-file mode takes
all branches with unknown conditions) and so gather different directives.
However I think this is negligible:
- this is already true of non-builtin macros (from included headers).
We've had no complaints.
- this affects the baseline and modified in the same way, so only makes a
difference transiently when code guarded by such an #ifdef is being edited
Differential Revision: https://reviews.llvm.org/D125179
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