[clang][modules] Don't depend on sharing FileManager during module build

Sharing the FileManager between the importer and the module build should
only be an optimization. Add a cc1 option -fno-modules-share-filemanager
to allow us to test this. Fix the path to modulemap files, which
previously depended on the shared FileManager when using path mapped to
an external file in a VFS.

Differential Revision: https://reviews.llvm.org/D131076

1 files changed, 15 insertions, 6 deletions

diff --git a/clang/lib/Frontend/CompilerInstance.cpp b/clang/lib/Frontend/CompilerInstance.cpp
index 2cd7efd..51c7bc2 100644
--- a/clang/lib/Frontend/CompilerInstance.cpp
+++ b/clang/lib/Frontend/CompilerInstance.cpp
@@ -1213,11 +1213,16 @@ compileModuleImpl(CompilerInstance &ImportingInstance, SourceLocation ImportLoc,
                                    ImportingInstance.getDiagnosticClient()),
                              /*ShouldOwnClient=*/true);
 
-  // Note that this module is part of the module build stack, so that we
-  // can detect cycles in the module graph.
-  Instance.setFileManager(&ImportingInstance.getFileManager());
+  if (FrontendOpts.ModulesShareFileManager) {
+    Instance.setFileManager(&ImportingInstance.getFileManager());
+  } else {
+    Instance.createFileManager(&ImportingInstance.getVirtualFileSystem());
+  }
   Instance.createSourceManager(Instance.getFileManager());
   SourceManager &SourceMgr = Instance.getSourceManager();
+
+  // Note that this module is part of the module build stack, so that we
+  // can detect cycles in the module graph.
   SourceMgr.setModuleBuildStack(
     ImportingInstance.getSourceManager().getModuleBuildStack());
   SourceMgr.pushModuleBuildStack(ModuleName,
@@ -1303,12 +1308,16 @@ static bool compileModule(CompilerInstance &ImportingInstance,
             ModuleMapFile, ImportingInstance.getFileManager()))
       ModuleMapFile = PublicMMFile;
 
+    // FIXME: Update header search to keep FileEntryRef rather than rely on
+    // getLastRef().
+    StringRef ModuleMapFilePath =
+        ModuleMapFile->getLastRef().getNameAsRequested();
+
     // Use the module map where this module resides.
     Result = compileModuleImpl(
         ImportingInstance, ImportLoc, Module->getTopLevelModuleName(),
-        FrontendInputFile(ModuleMapFile->getName(), IK, +Module->IsSystem),
-        ModMap.getModuleMapFileForUniquing(Module)->getName(),
-        ModuleFileName);
+        FrontendInputFile(ModuleMapFilePath, IK, +Module->IsSystem),
+        ModMap.getModuleMapFileForUniquing(Module)->getName(), ModuleFileName);
   } else {
     // FIXME: We only need to fake up an input file here as a way of
     // transporting the module's directory to the module map parser. We should