[clang][cas] Ignore the -fdepfile-entry= dependency option when calculating the cache key

`-fdepfile-entry=` is a dependency option that can be treated as "transparent", not affecting the
cached compilation. The passed-in filenames are added at the point where the dependency file is generated
and are not read from the file system.

rdar://99683427

Author: akyrtzi

clang/include/clang/Frontend/CASDependencyCollector.h

@@ -27,7 +27,7 @@ class CASDependencyCollector : public DependencyFileGenerator {
   /// \param Callback Callback that receives the resulting dependencies on
   ///                 completion, or \c None if an error occurred.
   CASDependencyCollector(
-      const DependencyOutputOptions &Opts, cas::ObjectStore &CAS,
+      DependencyOutputOptions Opts, cas::ObjectStore &CAS,
       std::function<void(Optional<cas::ObjectRef>)> Callback);
 
   /// Replay the given result, which should have been created by a
@@ -51,4 +51,4 @@ class CASDependencyCollector : public DependencyFileGenerator {
 
 } // namespace clang
 
-#endif // LLVM_CLANG_FRONTEND_CASDEPENDENCYCOLLECTOR_H
+#endif // LLVM_CLANG_FRONTEND_CASDEPENDENCYCOLLECTOR_H

clang/lib/Frontend/CASDependencyCollector.cpp

@@ -15,10 +15,19 @@
 using namespace clang;
 using namespace clang::cas;
 
+/// \returns \p DependencyOutputOptions but with \p ExtraDeps cleared out.
+///
+/// This is useful to avoid recording these filenames in the CAS.
+static DependencyOutputOptions dropExtraDeps(DependencyOutputOptions Opts) {
+  Opts.ExtraDeps.clear();
+  return Opts;
+}
+
 CASDependencyCollector::CASDependencyCollector(
-    const DependencyOutputOptions &Opts, cas::ObjectStore &CAS,
+    DependencyOutputOptions Opts, cas::ObjectStore &CAS,
     std::function<void(Optional<cas::ObjectRef>)> Callback)
-    : DependencyFileGenerator(Opts, llvm::vfs::makeNullOutputBackend()),
+    : DependencyFileGenerator(dropExtraDeps(std::move(Opts)),
+                              llvm::vfs::makeNullOutputBackend()),
       CAS(CAS), Callback(std::move(Callback)) {}
 
 llvm::Error CASDependencyCollector::replay(const DependencyOutputOptions &Opts,
@@ -29,6 +38,15 @@ llvm::Error CASDependencyCollector::replay(const DependencyOutputOptions &Opts,
     return Refs.takeError();
 
   CASDependencyCollector DC(Opts, CAS, nullptr);
+
+  // Add the filenames from DependencyOutputOptions::ExtraDeps. These are kept
+  // out of the compilation cache key since they can be passed-in and added at
+  // the point where the dependency file is generated, without needing to affect
+  // the cached compilation.
+  for (const std::pair<std::string, ExtraDepKind> &Dep : Opts.ExtraDeps) {
+    DC.addDependency(Dep.first);
+  }
+
   auto Err = Refs->forEachReference([&](ObjectRef Ref) -> llvm::Error {
     auto PathHandle = CAS.getProxy(Ref);
     if (!PathHandle)

clang/lib/Frontend/CompileJobCacheKey.cpp

@@ -79,6 +79,9 @@ clang::createCompileJobCacheKey(ObjectStore &CAS, DiagnosticsEngine &Diags,
   if (!DepOpts.Targets.empty())
     DepOpts.Targets = {"-"};
   DepOpts.UsePhonyTargets = false;
+  // These are added in when the dependency file is generated, but they don't
+  // affect the actual compilation.
+  DepOpts.ExtraDeps.clear();
 
   // Generate a new command-line in case Invocation has been canonicalized.
   llvm::BumpPtrAllocator Alloc;

clang/test/CAS/fcache-compile-job-dependency-file.c

@@ -31,11 +31,12 @@
 // RUN: %clang -cc1 -triple x86_64-apple-macos11 \
 // RUN:   -fcas-path %t/cas -faction-cache-path %t/cache -fcas-fs @%t/casid -fcache-compile-job \
 // RUN:   -Rcompile-job-cache %t/main.c -emit-obj -o %t/output.o -isystem %t/sys \
-// RUN:   -dependency-file %t/deps3.d -MT other1 -MT other2 -MP 2>&1 \
+// RUN:   -dependency-file %t/deps3.d -MT other1 -MT other2 -MP -fdepfile-entry=extra-depfile.json 2>&1 \
 // RUN:   | FileCheck %s --check-prefix=CACHE-HIT
 
 // RUN: FileCheck %s --input-file=%t/deps3.d --check-prefix=DEPS_OTHER
 // DEPS_OTHER: other1 other2:
+// DEPS_OTHER: extra-depfile.json
 // DEPS_OTHER: main.c
 // DEPS_OTHER: my_header.h
 // DEPS_OTHER-NOT: sys.h
@@ -56,6 +57,29 @@
 // DEPS_SYS: my_header.h
 // DEPS_SYS: sys.h
 
+// Using another cache path to avoid reusing artifacts.
+
+// RUN: %clang -cc1 -triple x86_64-apple-macos11 \
+// RUN:   -fcas-path %t/cas -faction-cache-path %t/cache2 -fcas-fs @%t/casid -fcache-compile-job \
+// RUN:   -Rcompile-job-cache %t/main.c -emit-obj -o %t/output.o -isystem %t/sys \
+// RUN:   -dependency-file %t/deps-depfile1.d -MT deps -fdepfile-entry=extra-depfile.json -fdepfile-entry=%t/main.c 2>&1 \
+// RUN:   | FileCheck %s --check-prefix=CACHE-MISS
+
+// RUN: FileCheck %s --input-file=%t/deps-depfile1.d --check-prefix=DEPS_DEPFILE1
+// DEPS_DEPFILE1: deps:
+// DEPS_DEPFILE1: extra-depfile.json
+// DEPS_DEPFILE1: main.c
+
+// RUN: %clang -cc1 -triple x86_64-apple-macos11 \
+// RUN:   -fcas-path %t/cas -faction-cache-path %t/cache2 -fcas-fs @%t/casid -fcache-compile-job \
+// RUN:   -Rcompile-job-cache %t/main.c -emit-obj -o %t/output.o -isystem %t/sys \
+// RUN:   -dependency-file %t/deps-depfile2.d -MT deps 2>&1 \
+// RUN:   | FileCheck %s --check-prefix=CACHE-HIT
+
+// RUN: FileCheck %s --input-file=%t/deps-depfile2.d --check-prefix=DEPS_DEPFILE2
+// DEPS_DEPFILE2-NOT: extra-depfile.json
+// DEPS_DEPFILE2: main.c
+
 //--- main.c
 #include "my_header.h"
 #include <sys.h>