Frontend: Remove CompilerInstance::VirtualFileSystem, NFC

Remove CompilerInstance::VirtualFileSystem and
CompilerInstance::setVirtualFileSystem, instead relying on the VFS in
the FileManager.  CompilerInstance and its clients already went to some
trouble to make these match.  Now they are guaranteed to match.

As part of this, I added a VFS parameter (defaults to nullptr) to
CompilerInstance::createFileManager, to avoid repeating construction
logic in clients that just wanted to customize the VFS.

https://reviews.llvm.org/D59377

llvm-svn: 357037

1 files changed, 13 insertions, 16 deletions

diff --git a/clang/lib/Frontend/ASTUnit.cpp b/clang/lib/Frontend/ASTUnit.cpp
index 0b2995b8eed..7bc3010fcad 100644
--- a/clang/lib/Frontend/ASTUnit.cpp
+++ b/clang/lib/Frontend/ASTUnit.cpp
@@ -1078,28 +1078,29 @@ bool ASTUnit::Parse(std::shared_ptr<PCHContainerOperations> PCHContainerOps,
   if (!Invocation)
     return true;
 
+  if (VFS && FileMgr)
+    assert(VFS == FileMgr->getVirtualFileSystem() &&
+           "VFS passed to Parse and VFS in FileMgr are different");
+
   auto CCInvocation = std::make_shared<CompilerInvocation>(*Invocation);
   if (OverrideMainBuffer) {
     assert(Preamble &&
            "No preamble was built, but OverrideMainBuffer is not null");
-    IntrusiveRefCntPtr<llvm::vfs::FileSystem> OldVFS = VFS;
     Preamble->AddImplicitPreamble(*CCInvocation, VFS, OverrideMainBuffer.get());
-    if (OldVFS != VFS && FileMgr) {
-      assert(OldVFS == FileMgr->getVirtualFileSystem() &&
-             "VFS passed to Parse and VFS in FileMgr are different");
-      FileMgr = new FileManager(FileMgr->getFileSystemOpts(), VFS);
-    }
+    // VFS may have changed...
   }
 
   // Create the compiler instance to use for building the AST.
   std::unique_ptr<CompilerInstance> Clang(
       new CompilerInstance(std::move(PCHContainerOps)));
-  if (FileMgr && VFS) {
-    assert(VFS == FileMgr->getVirtualFileSystem() &&
-           "VFS passed to Parse and VFS in FileMgr are different");
-  } else if (VFS) {
-    Clang->setVirtualFileSystem(VFS);
-  }
+
+  // Ensure that Clang has a FileManager with the right VFS, which may have
+  // changed above in AddImplicitPreamble.  If VFS is nullptr, rely on
+  // createFileManager to create one.
+  if (VFS && FileMgr && FileMgr->getVirtualFileSystem() == VFS)
+    Clang->setFileManager(&*FileMgr);
+  else
+    FileMgr = Clang->createFileManager(std::move(VFS));
 
   // Recover resources if we crash before exiting this method.
   llvm::CrashRecoveryContextCleanupRegistrar<CompilerInstance>
@@ -1136,10 +1137,6 @@ bool ASTUnit::Parse(std::shared_ptr<PCHContainerOperations> PCHContainerOps,
   // Configure the various subsystems.
   LangOpts = Clang->getInvocation().LangOpts;
   FileSystemOpts = Clang->getFileSystemOpts();
-  if (!FileMgr) {
-    Clang->createFileManager();
-    FileMgr = &Clang->getFileManager();
-  }
 
   ResetForParse();