35ce741ef3
Underlying FS can store different file names inside the stat response (e.g. symlinks resolved, absolute paths, dots removed). But we store path names as requested inside the preamble, https://github.com/llvm/llvm-project/blob/main/clang/lib/Serialization/ASTWriter.cpp#L1635. This improves cache hit rates from ~30% to 90% in a build system that uses symlinks. Differential Revision: https://reviews.llvm.org/D151185
82 lines
3.1 KiB
C++
82 lines
3.1 KiB
C++
//===--- FS.h - File system related utils ------------------------*- C++-*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANGD_FS_H
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#define LLVM_CLANG_TOOLS_EXTRA_CLANGD_FS_H
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#include "support/Path.h"
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#include "clang/Basic/LLVM.h"
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#include "llvm/ADT/StringMap.h"
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#include "llvm/Support/VirtualFileSystem.h"
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#include <optional>
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namespace clang {
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namespace clangd {
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/// Records status information for files open()ed or stat()ed during preamble
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/// build (except for the main file), so we can avoid stat()s on the underlying
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/// FS when reusing the preamble. For example, code completion can re-stat files
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/// when getting FileID for source locations stored in preamble (e.g. checking
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/// whether a location is in the main file).
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///
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/// The cache is keyed by absolute path of file name in cached status, as this
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/// is what preamble stores.
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///
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/// The cache is not thread-safe when updates happen, so the use pattern should
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/// be:
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/// - One FS writes to the cache from one thread (or several but strictly
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/// sequenced), e.g. when building preamble.
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/// - Sequence point (no writes after this point, no reads before).
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/// - Several FSs can read from the cache, e.g. code completions.
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///
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/// Note that the cache is only valid when reusing preamble.
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class PreambleFileStatusCache {
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public:
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/// \p MainFilePath is the absolute path of the main source file this preamble
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/// corresponds to. The stat for the main file will not be cached.
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PreambleFileStatusCache(llvm::StringRef MainFilePath);
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void update(const llvm::vfs::FileSystem &FS, llvm::vfs::Status S,
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llvm::StringRef File);
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/// \p Path is a path stored in preamble.
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std::optional<llvm::vfs::Status> lookup(llvm::StringRef Path) const;
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/// Returns a VFS that collects file status.
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/// Only cache stats for files that exist because
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/// 1) we only care about existing files when reusing preamble, unlike
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/// building preamble.
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/// 2) we use the file name in the Status as the cache key.
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///
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/// Note that the returned VFS should not outlive the cache.
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IntrusiveRefCntPtr<llvm::vfs::FileSystem>
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getProducingFS(IntrusiveRefCntPtr<llvm::vfs::FileSystem> FS);
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/// Returns a VFS that uses the cache collected.
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///
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/// Note that the returned VFS should not outlive the cache.
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IntrusiveRefCntPtr<llvm::vfs::FileSystem>
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getConsumingFS(IntrusiveRefCntPtr<llvm::vfs::FileSystem> FS) const;
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private:
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std::string MainFilePath;
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llvm::StringMap<llvm::vfs::Status> StatCache;
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};
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/// Returns a version of \p File that doesn't contain dots and dot dots.
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/// e.g /a/b/../c -> /a/c
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/// /a/b/./c -> /a/b/c
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/// FIXME: We should avoid encountering such paths in clangd internals by
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/// filtering everything we get over LSP, CDB, etc.
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Path removeDots(PathRef File);
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} // namespace clangd
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} // namespace clang
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#endif // LLVM_CLANG_TOOLS_EXTRA_CLANGD_FS_H
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