[all-commits] [llvm/llvm-project] a11a43: [clang][deps] Cache `VFS::getRealPath()` (#68645)

[Jan Svoboda via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: a11a4324bb27c01e7a005e1a7f49fb8284098e8c
      https://github.com/llvm/llvm-project/commit/a11a4324bb27c01e7a005e1a7f49fb8284098e8c
  Author: Jan Svoboda <jan_svoboda at apple.com>
  Date:   2024-04-12 (Fri, 12 Apr 2024)

  Changed paths:
    M clang/include/clang/Tooling/DependencyScanning/DependencyScanningFilesystem.h
    M clang/lib/Tooling/DependencyScanning/DependencyScanningFilesystem.cpp
    M clang/unittests/Tooling/CMakeLists.txt
    A clang/unittests/Tooling/DependencyScanning/DependencyScanningFilesystemTest.cpp

  Log Message:
  -----------
  [clang][deps] Cache `VFS::getRealPath()` (#68645)

This PR starts caching calls to
`DependencyScanningWorkerFilesystem::getRealPath()` that we use whenever
we canonicalize module map path. In the case of the real VFS, this
functions performs an expensive syscall that we'd like to do as rarely
as possible.

This PR keeps the real path out of `CachedFileSystemEntry`, since that's
**immutable**; populating the real path on creation of this data
structure (every stat/open) would be expensive.



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