[all-commits] [llvm/llvm-project] d19f06: [clang][Tooling] Try to avoid file system access i...

[Aleksandr Platonov via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: d19f0666bcd8f7d26aaf4019244c3ed91e47b1b7
      https://github.com/llvm/llvm-project/commit/d19f0666bcd8f7d26aaf4019244c3ed91e47b1b7
  Author: Aleksandr Platonov <platonov.aleksandr at huawei.com>
  Date:   2020-07-17 (Fri, 17 Jul 2020)

  Changed paths:
    M clang/lib/Tooling/FileMatchTrie.cpp
    M clang/unittests/Tooling/CompilationDatabaseTest.cpp

  Log Message:
  -----------
  [clang][Tooling] Try to avoid file system access if there is no record for the file in compile_commads.json

Summary:
If there is no record in compile_commands.json, we try to find suitable record with `MatchTrie.findEquivalent()` call.
This is very expensive operation with a lot of `llvm::sys::fs::equivalent()` calls in some cases.

This patch disables file symlinks for performance reasons.

Example scenario without this patch:
- compile_commands.json generated at clangd build (contains ~3000 files).
- it tooks more than 1 second to get compile command for newly created file in the root folder of LLVM project.
- we wait for 1 second every time when clangd requests compile command for this file (at file change).

Reviewers: sammccall, kadircet, hokein

Reviewed By: sammccall

Subscribers: chandlerc, djasper, klimek, ilya-biryukov, kadircet, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D83621