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diff --git a/lib/Tooling/DependencyScanning/DependencyScanningFilesystem.cpp b/lib/Tooling/DependencyScanning/DependencyScanningFilesystem.cpp
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+//===- DependencyScanningFilesystem.cpp - clang-scan-deps fs --------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Tooling/DependencyScanning/DependencyScanningFilesystem.h"
+#include "clang/Lex/DependencyDirectivesSourceMinimizer.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/Threading.h"
+
+using namespace clang;
+using namespace tooling;
+using namespace dependencies;
+
+CachedFileSystemEntry CachedFileSystemEntry::createFileEntry(
+ StringRef Filename, llvm::vfs::FileSystem &FS, bool Minimize) {
+ // Load the file and its content from the file system.
+ llvm::ErrorOr<std::unique_ptr<llvm::vfs::File>> MaybeFile =
+ FS.openFileForRead(Filename);
+ if (!MaybeFile)
+ return MaybeFile.getError();
+ llvm::ErrorOr<llvm::vfs::Status> Stat = (*MaybeFile)->status();
+ if (!Stat)
+ return Stat.getError();
+
+ llvm::vfs::File &F = **MaybeFile;
+ llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> MaybeBuffer =
+ F.getBuffer(Stat->getName());
+ if (!MaybeBuffer)
+ return MaybeBuffer.getError();
+
+ llvm::SmallString<1024> MinimizedFileContents;
+ // Minimize the file down to directives that might affect the dependencies.
+ const auto &Buffer = *MaybeBuffer;
+ SmallVector<minimize_source_to_dependency_directives::Token, 64> Tokens;
+ if (!Minimize || minimizeSourceToDependencyDirectives(
+ Buffer->getBuffer(), MinimizedFileContents, Tokens)) {
+ // Use the original file unless requested otherwise, or
+ // if the minimization failed.
+ // FIXME: Propage the diagnostic if desired by the client.
+ CachedFileSystemEntry Result;
+ Result.MaybeStat = std::move(*Stat);
+ Result.Contents.reserve(Buffer->getBufferSize() + 1);
+ Result.Contents.append(Buffer->getBufferStart(), Buffer->getBufferEnd());
+ // Implicitly null terminate the contents for Clang's lexer.
+ Result.Contents.push_back('\0');
+ Result.Contents.pop_back();
+ return Result;
+ }
+
+ CachedFileSystemEntry Result;
+ size_t Size = MinimizedFileContents.size();
+ Result.MaybeStat = llvm::vfs::Status(Stat->getName(), Stat->getUniqueID(),
+ Stat->getLastModificationTime(),
+ Stat->getUser(), Stat->getGroup(), Size,
+ Stat->getType(), Stat->getPermissions());
+ // The contents produced by the minimizer must be null terminated.
+ assert(MinimizedFileContents.data()[MinimizedFileContents.size()] == '\0' &&
+ "not null terminated contents");
+ // Even though there's an implicit null terminator in the minimized contents,
+ // we want to temporarily make it explicit. This will ensure that the
+ // std::move will preserve it even if it needs to do a copy if the
+ // SmallString still has the small capacity.
+ MinimizedFileContents.push_back('\0');
+ Result.Contents = std::move(MinimizedFileContents);
+ // Now make the null terminator implicit again, so that Clang's lexer can find
+ // it right where the buffer ends.
+ Result.Contents.pop_back();
+
+ // Compute the skipped PP ranges that speedup skipping over inactive
+ // preprocessor blocks.
+ llvm::SmallVector<minimize_source_to_dependency_directives::SkippedRange, 32>
+ SkippedRanges;
+ minimize_source_to_dependency_directives::computeSkippedRanges(Tokens,
+ SkippedRanges);
+ PreprocessorSkippedRangeMapping Mapping;
+ for (const auto &Range : SkippedRanges) {
+ if (Range.Length < 16) {
+ // Ignore small ranges as non-profitable.
+ // FIXME: This is a heuristic, its worth investigating the tradeoffs
+ // when it should be applied.
+ continue;
+ }
+ Mapping[Range.Offset] = Range.Length;
+ }
+ Result.PPSkippedRangeMapping = std::move(Mapping);
+
+ return Result;
+}
+
+CachedFileSystemEntry
+CachedFileSystemEntry::createDirectoryEntry(llvm::vfs::Status &&Stat) {
+ assert(Stat.isDirectory() && "not a directory!");
+ auto Result = CachedFileSystemEntry();
+ Result.MaybeStat = std::move(Stat);
+ return Result;
+}
+
+DependencyScanningFilesystemSharedCache::
+ DependencyScanningFilesystemSharedCache() {
+ // This heuristic was chosen using a empirical testing on a
+ // reasonably high core machine (iMacPro 18 cores / 36 threads). The cache
+ // sharding gives a performance edge by reducing the lock contention.
+ // FIXME: A better heuristic might also consider the OS to account for
+ // the different cost of lock contention on different OSes.
+ NumShards = std::max(2u, llvm::hardware_concurrency() / 4);
+ CacheShards = std::make_unique<CacheShard[]>(NumShards);
+}
+
+/// Returns a cache entry for the corresponding key.
+///
+/// A new cache entry is created if the key is not in the cache. This is a
+/// thread safe call.
+DependencyScanningFilesystemSharedCache::SharedFileSystemEntry &
+DependencyScanningFilesystemSharedCache::get(StringRef Key) {
+ CacheShard &Shard = CacheShards[llvm::hash_value(Key) % NumShards];
+ std::unique_lock<std::mutex> LockGuard(Shard.CacheLock);
+ auto It = Shard.Cache.try_emplace(Key);
+ return It.first->getValue();
+}
+
+llvm::ErrorOr<const CachedFileSystemEntry *>
+DependencyScanningWorkerFilesystem::getOrCreateFileSystemEntry(
+ const StringRef Filename) {
+ if (const CachedFileSystemEntry *Entry = getCachedEntry(Filename)) {
+ return Entry;
+ }
+
+ // FIXME: Handle PCM/PCH files.
+ // FIXME: Handle module map files.
+
+ bool KeepOriginalSource = IgnoredFiles.count(Filename);
+ DependencyScanningFilesystemSharedCache::SharedFileSystemEntry
+ &SharedCacheEntry = SharedCache.get(Filename);
+ const CachedFileSystemEntry *Result;
+ {
+ std::unique_lock<std::mutex> LockGuard(SharedCacheEntry.ValueLock);
+ CachedFileSystemEntry &CacheEntry = SharedCacheEntry.Value;
+
+ if (!CacheEntry.isValid()) {
+ llvm::vfs::FileSystem &FS = getUnderlyingFS();
+ auto MaybeStatus = FS.status(Filename);
+ if (!MaybeStatus)
+ CacheEntry = CachedFileSystemEntry(MaybeStatus.getError());
+ else if (MaybeStatus->isDirectory())
+ CacheEntry = CachedFileSystemEntry::createDirectoryEntry(
+ std::move(*MaybeStatus));
+ else
+ CacheEntry = CachedFileSystemEntry::createFileEntry(
+ Filename, FS, !KeepOriginalSource);
+ }
+
+ Result = &CacheEntry;
+ }
+
+ // Store the result in the local cache.
+ setCachedEntry(Filename, Result);
+ return Result;
+}
+
+llvm::ErrorOr<llvm::vfs::Status>
+DependencyScanningWorkerFilesystem::status(const Twine &Path) {
+ SmallString<256> OwnedFilename;
+ StringRef Filename = Path.toStringRef(OwnedFilename);
+ const llvm::ErrorOr<const CachedFileSystemEntry *> Result =
+ getOrCreateFileSystemEntry(Filename);
+ if (!Result)
+ return Result.getError();
+ return (*Result)->getStatus();
+}
+
+namespace {
+
+/// The VFS that is used by clang consumes the \c CachedFileSystemEntry using
+/// this subclass.
+class MinimizedVFSFile final : public llvm::vfs::File {
+public:
+ MinimizedVFSFile(std::unique_ptr<llvm::MemoryBuffer> Buffer,
+ llvm::vfs::Status Stat)
+ : Buffer(std::move(Buffer)), Stat(std::move(Stat)) {}
+
+ llvm::ErrorOr<llvm::vfs::Status> status() override { return Stat; }
+
+ const llvm::MemoryBuffer *getBufferPtr() const { return Buffer.get(); }
+
+ llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>>
+ getBuffer(const Twine &Name, int64_t FileSize, bool RequiresNullTerminator,
+ bool IsVolatile) override {
+ return std::move(Buffer);
+ }
+
+ std::error_code close() override { return {}; }
+
+private:
+ std::unique_ptr<llvm::MemoryBuffer> Buffer;
+ llvm::vfs::Status Stat;
+};
+
+llvm::ErrorOr<std::unique_ptr<llvm::vfs::File>>
+createFile(const CachedFileSystemEntry *Entry,
+ ExcludedPreprocessorDirectiveSkipMapping *PPSkipMappings) {
+ if (Entry->isDirectory())
+ return llvm::ErrorOr<std::unique_ptr<llvm::vfs::File>>(
+ std::make_error_code(std::errc::is_a_directory));
+ llvm::ErrorOr<StringRef> Contents = Entry->getContents();
+ if (!Contents)
+ return Contents.getError();
+ auto Result = std::make_unique<MinimizedVFSFile>(
+ llvm::MemoryBuffer::getMemBuffer(*Contents, Entry->getName(),
+ /*RequiresNullTerminator=*/false),
+ *Entry->getStatus());
+ if (!Entry->getPPSkippedRangeMapping().empty() && PPSkipMappings)
+ (*PPSkipMappings)[Result->getBufferPtr()] =
+ &Entry->getPPSkippedRangeMapping();
+ return llvm::ErrorOr<std::unique_ptr<llvm::vfs::File>>(
+ std::unique_ptr<llvm::vfs::File>(std::move(Result)));
+}
+
+} // end anonymous namespace
+
+llvm::ErrorOr<std::unique_ptr<llvm::vfs::File>>
+DependencyScanningWorkerFilesystem::openFileForRead(const Twine &Path) {
+ SmallString<256> OwnedFilename;
+ StringRef Filename = Path.toStringRef(OwnedFilename);
+
+ const llvm::ErrorOr<const CachedFileSystemEntry *> Result =
+ getOrCreateFileSystemEntry(Filename);
+ if (!Result)
+ return Result.getError();
+ return createFile(Result.get(), PPSkipMappings);
+}