[clang][cas] Move CompileJobCache into Frontend library

(cherry picked from commit b36bc6f)

Author: akyrtzi

clang/include/clang/Frontend/CompileJobCache.h

@@ -0,0 +1,100 @@
+//===- CompileJobCache.h ----------------------------------------*- C++ -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_FRONTEND_COMPILEJOBCACHE_H
+#define LLVM_CLANG_FRONTEND_COMPILEJOBCACHE_H
+
+#include "clang/Frontend/CompileJobCacheResult.h"
+
+namespace clang {
+
+class CompilerInstance;
+class DiagnosticsEngine;
+
+// Manage caching and replay of compile jobs.
+//
+// The high-level model is:
+//
+//  1. Extract options from the CompilerInvocation:
+//       - that can be simulated and
+//       - that don't affect the compile job's result.
+//  2. Canonicalize the options extracted in (1).
+//  3. Compute the result of the compile job using the canonicalized
+//     CompilerInvocation, with hooks installed to redirect outputs and
+//     enable live-streaming of a running compile job to stdout or stderr.
+//       - Compute a cache key.
+//       - Check the cache, and run the compile job if there's a cache miss.
+//       - Store the result of the compile job in the cache.
+//  4. Replay the compile job, using the options extracted in (1).
+//
+// An example (albeit not yet implemented) is handling options controlling
+// output of diagnostics. The CompilerInvocation can be canonicalized to
+// serialize the diagnostics to a virtual path (<output>.diag or something).
+//
+//   - On a cache miss, the compile job runs, and the diagnostics are
+//     serialized and stored in the cache per the canonicalized options
+//     from (2).
+//   - Either way, the diagnostics are replayed according to the options
+//     extracted from (1) during (4).
+//
+// The above will produce the correct output for diagnostics, but the experience
+// will be degraded in the common command-line case (emitting to stderr)
+// because the diagnostics will not be streamed live. This can be improved:
+//
+//   - Change (3) to accept a hook: a DiagnosticsConsumer that diagnostics
+//     are mirrored to (in addition to canonicalized options from (2)).
+//   - If diagnostics would be live-streamed, send in a diagnostics consumer
+//     that matches (1). Otherwise, send in an IgnoringDiagnosticsConsumer.
+//   - In step (4), only skip replaying the diagnostics if they were already
+//     handled.
+class CompileJobCache {
+public:
+  CompileJobCache();
+  ~CompileJobCache();
+
+  using OutputKind = clang::cas::CompileJobCacheResult::OutputKind;
+
+  StringRef getPathForOutputKind(OutputKind Kind);
+
+  /// Canonicalize \p Clang.
+  ///
+  /// \returns status if should exit immediately, otherwise None.
+  ///
+  /// TODO: Refactor \a cc1_main() so that instead this canonicalizes the
+  /// CompilerInvocation before Clang gets access to command-line arguments, to
+  /// control what might leak.
+  std::optional<int> initialize(CompilerInstance &Clang);
+
+  /// Try looking up a cached result and replaying it.
+  ///
+  /// \returns status if should exit immediately, otherwise None.
+  std::optional<int> tryReplayCachedResult(CompilerInstance &Clang);
+
+  /// Finish writing outputs from a computed result, after a cache miss.
+  ///
+  /// \returns true if finished successfully.
+  bool finishComputedResult(CompilerInstance &Clang, bool Success);
+
+  class CachingOutputs;
+
+private:
+  int reportCachingBackendError(DiagnosticsEngine &Diag, llvm::Error &&E);
+
+  bool CacheCompileJob = false;
+  bool DisableCachedCompileJobReplay = false;
+
+  std::shared_ptr<llvm::cas::ObjectStore> CAS;
+  std::shared_ptr<llvm::cas::ActionCache> Cache;
+  llvm::Optional<llvm::cas::CASID> ResultCacheKey;
+
+  std::unique_ptr<CachingOutputs> CacheBackend;
+};
+
+} // namespace clang
+
+#endif // LLVM_CLANG_FRONTEND_COMPILEJOBCACHE_H

clang/lib/Frontend/CMakeLists.txt

@@ -6,16 +6,19 @@ set(LLVM_LINK_COMPONENTS
   CAS
   Option
   ProfileData
+  RemoteCachingService
   Support
   )
 
 add_clang_library(clangFrontend
   ASTConsumers.cpp
   ASTMerge.cpp
   ASTUnit.cpp
+  CachedDiagnostics.cpp
   CASDependencyCollector.cpp
   ChainedDiagnosticConsumer.cpp
   ChainedIncludesSource.cpp
+  CompileJobCache.cpp
   CompileJobCacheKey.cpp
   CompileJobCacheResult.cpp
   CompilerInstance.cpp