[Dependency Scanning] Configure the Clang dependency scanner to generate PCM output paths

Using the convention of : <Module_Cache_Path> + "/" + <Module_Name> + "-" + <Context_Hash> + ".pcm"

Author: artemcm

lib/AST/ModuleDependencies.cpp

@@ -230,7 +230,7 @@ GlobalModuleDependenciesCache::GlobalModuleDependenciesCache()
                          clang::tooling::dependencies::ScanningMode::DependencyDirectivesScan,
                          clang::tooling::dependencies::ScanningOutputFormat::Full,
                          clang::CASOptions(),
-                         /* Cache */ nullptr,
+                         /* Cache (llvm::cas::ActionCache) */ nullptr,
                          /* SharedFS */ nullptr,
                          /* ReuseFileManager */ false,
                          /* OptimizeArgs */ false) {}

lib/ClangImporter/ClangModuleDependencyScanner.cpp

@@ -22,26 +22,32 @@
 #include "clang/Tooling/DependencyScanning/DependencyScanningTool.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/Signals.h"
+#include "llvm/Support/Path.h"
 
 using namespace swift;
 
 using namespace clang::tooling;
 using namespace clang::tooling::dependencies;
 
-static std::string lookupModuleOutput(const ModuleID &MID,
-                                      ModuleOutputKind MOK) {
-  // Deciding the output paths is done in swift-driver.
+static std::string moduleCacheRelativeLookupModuleOutput(const ModuleID &MID,
+                                                         ModuleOutputKind MOK,
+                                                         const std::string &moduleCachePathStr) {
+  llvm::SmallString<128> outputPath(moduleCachePathStr);
+  llvm::sys::path::append(outputPath, MID.ModuleName + "-" + MID.ContextHash);
   switch (MOK) {
   case ModuleOutputKind::ModuleFile:
-    return "<replace-me>";
+    llvm::sys::path::replace_extension(outputPath, getExtension(swift::file_types::TY_ClangModuleFile));
+    break;
   case ModuleOutputKind::DependencyFile:
-    return "<replace-me>";
+    llvm::sys::path::replace_extension(outputPath, getExtension(swift::file_types::TY_Dependencies));
+    break;
   case ModuleOutputKind::DependencyTargets:
     return MID.ModuleName + "-" + MID.ContextHash;
   case ModuleOutputKind::DiagnosticSerializationFile:
-    return "<replace-me>";
+    llvm::sys::path::replace_extension(outputPath, getExtension(swift::file_types::TY_SerializedDiagnostics));
+    break;
   }
-  llvm_unreachable("Fully covered switch above!");
+  return outputPath.str().str();
 }
 
 // Add search paths.
@@ -228,6 +234,12 @@ Optional<ModuleDependencies> ClangImporter::getModuleDependencies(
     workingDir = *(clangWorkingDirPos - 1);
   }
 
+  auto moduleCachePath = getModuleCachePathFromClang(getClangInstance());
+  auto lookupModuleOutput = [moduleCachePath] (const ModuleID &MID,
+                                               ModuleOutputKind MOK) -> std::string {
+    return moduleCacheRelativeLookupModuleOutput(MID, MOK, moduleCachePath);
+  };
+
   auto clangDependencies = cache.getClangScannerTool().getFullDependencies(
       commandLineArgs, workingDir, cache.getAlreadySeenClangModules(),
       lookupModuleOutput, moduleName);
@@ -284,6 +296,12 @@ bool ClangImporter::addBridgingHeaderDependencies(
   std::string workingDir =
       ctx.SourceMgr.getFileSystem()->getCurrentWorkingDirectory().get();
 
+  auto moduleCachePath = getModuleCachePathFromClang(getClangInstance());
+  auto lookupModuleOutput = [moduleCachePath] (const ModuleID &MID,
+                                               ModuleOutputKind MOK) -> std::string {
+    return moduleCacheRelativeLookupModuleOutput(MID, MOK, moduleCachePath);
+  };
+
   auto clangDependencies = cache.getClangScannerTool().getFullDependencies(
       commandLineArgs, workingDir, cache.getAlreadySeenClangModules(),
       lookupModuleOutput);

test/ScanDependencies/module_deps.swift

@@ -210,6 +210,10 @@ import SubE
 
 /// --------Clang module B
 // CHECK-LABEL: "modulePath": "B.pcm"
+// CHECK: "contextHash": [[B_CONTEXT:"{{.*}}"]],
+// CHECK: "-o"
+// CHECK-NEXT: "-Xcc"
+// CHECK-NEXT: "%t/clang-module-cache/B-[[B_CONTEXT]].pcm",
 
 // CHECK-NEXT: sourceFiles
 // CHECK-DAG: module.modulemap
@@ -222,7 +226,11 @@ import SubE
 
 /// --------Clang module SwiftShims
 // CHECK-LABEL: "modulePath": "SwiftShims.pcm",
-
+// CHECK: "contextHash": [[SHIMS_CONTEXT:"{{.*}}"]],
+// CHECK: "-o"
+// CHECK-NEXT: "-Xcc"
+// CHECK-NEXT: "%t/clang-module-cache/SwiftShims-[[SHIMS_CONTEXT]].pcm",
+// CHECK: "-fmodule-file=A=%t/clang-module-cache/A-{{.*}}.pcm"
 // CHECK-NO-SEARCH-PATHS-NOT: "-prebuilt-module-cache-path"
 
 // Check make-style dependencies