Use the VFS from the CompilerInvocation by default

Summary:
The CompilerInstance should create its default VFS from its CompilerInvocation. Right now the
user has to manually create the VFS before creating the FileManager even though
`-ivfsoverlay file.yaml` was passed via the CompilerInvocation (which is exactly how we worked
around this issue in `FrontendAction.cpp` so far).

This patch uses the invocation's VFS by default and also tests this behavior now from the
point of view of a program that uses the clang API.

Reviewers: benlangmuir, v.g.vassilev

Reviewed By: v.g.vassilev

Subscribers: mgorny, cfe-commits, v.g.vassilev

Differential Revision: https://reviews.llvm.org/D37416

llvm-svn: 313049

1 files changed, 4 insertions, 10 deletions

diff --git a/clang/lib/Frontend/FrontendAction.cpp b/clang/lib/Frontend/FrontendAction.cpp
index 52e2799deb5..12226b23141 100644
--- a/clang/lib/Frontend/FrontendAction.cpp
+++ b/clang/lib/Frontend/FrontendAction.cpp
@@ -633,18 +633,12 @@ bool FrontendAction::BeginSourceFile(CompilerInstance &CI,
     return true;
   }
 
-  if (!CI.hasVirtualFileSystem()) {
-    if (IntrusiveRefCntPtr<vfs::FileSystem> VFS =
-          createVFSFromCompilerInvocation(CI.getInvocation(),
-                                          CI.getDiagnostics()))
-      CI.setVirtualFileSystem(VFS);
-    else
+  // Set up the file and source managers, if needed.
+  if (!CI.hasFileManager()) {
+    if (!CI.createFileManager()) {
       goto failure;
+    }
   }
-
-  // Set up the file and source managers, if needed.
-  if (!CI.hasFileManager())
-    CI.createFileManager();
   if (!CI.hasSourceManager())
     CI.createSourceManager(CI.getFileManager());