Introduce FileEntryRef and use it when handling includes to report correct dependencies

when the FileManager is reused across invocations

This commit introduces a parallel API to FileManager's getFile: getFileEntryRef, which returns
a reference to the FileEntry, and the name that was used to access the file. In the case of
a VFS with 'use-external-names', the FileEntyRef contains the external name of the file,
not the filename that was used to access it.

The new API is adopted only in the HeaderSearch and Preprocessor for include file lookup, so that the
accessed path can be propagated to SourceManager's FileInfo. SourceManager's FileInfo now can report this accessed path, using
the new getName method. This API is then adopted in the dependency collector, which now correctly reports dependencies when a file
is included both using a symlink and a real path in the case when the FileManager is reused across multiple Preprocessor invocations.

Note that this patch does not fix all dependency collector issues, as the same problem is still present in other cases when dependencies
are obtained using FileSkipped, InclusionDirective, and HasInclude. This will be fixed in follow-up commits.

Differential Revision: https://reviews.llvm.org/D65907

llvm-svn: 369680

1 files changed, 13 insertions, 9 deletions

diff --git a/clang/lib/Frontend/CompilerInstance.cpp b/clang/lib/Frontend/CompilerInstance.cpp
index c7dedb78ed8..cbf519758ec 100644
--- a/clang/lib/Frontend/CompilerInstance.cpp
+++ b/clang/lib/Frontend/CompilerInstance.cpp
@@ -831,33 +831,37 @@ bool CompilerInstance::InitializeSourceManager(
 
   // Figure out where to get and map in the main file.
   if (InputFile != "-") {
-    auto FileOrErr = FileMgr.getFile(InputFile, /*OpenFile=*/true);
+    auto FileOrErr = FileMgr.getFileRef(InputFile, /*OpenFile=*/true);
     if (!FileOrErr) {
       Diags.Report(diag::err_fe_error_reading) << InputFile;
       return false;
     }
-    auto File = *FileOrErr;
+    FileEntryRef File = *FileOrErr;
 
     // The natural SourceManager infrastructure can't currently handle named
     // pipes, but we would at least like to accept them for the main
     // file. Detect them here, read them with the volatile flag so FileMgr will
     // pick up the correct size, and simply override their contents as we do for
     // STDIN.
-    if (File->isNamedPipe()) {
-      auto MB = FileMgr.getBufferForFile(File, /*isVolatile=*/true);
+    if (File.getFileEntry().isNamedPipe()) {
+      auto MB =
+          FileMgr.getBufferForFile(&File.getFileEntry(), /*isVolatile=*/true);
       if (MB) {
         // Create a new virtual file that will have the correct size.
-        File = FileMgr.getVirtualFile(InputFile, (*MB)->getBufferSize(), 0);
-        SourceMgr.overrideFileContents(File, std::move(*MB));
+        const FileEntry *FE =
+            FileMgr.getVirtualFile(InputFile, (*MB)->getBufferSize(), 0);
+        SourceMgr.overrideFileContents(FE, std::move(*MB));
+        SourceMgr.setMainFileID(
+            SourceMgr.createFileID(FE, SourceLocation(), Kind));
       } else {
         Diags.Report(diag::err_cannot_open_file) << InputFile
                                                  << MB.getError().message();
         return false;
       }
+    } else {
+      SourceMgr.setMainFileID(
+          SourceMgr.createFileID(File, SourceLocation(), Kind));
     }
-
-    SourceMgr.setMainFileID(
-        SourceMgr.createFileID(File, SourceLocation(), Kind));
   } else {
     llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> SBOrErr =
         llvm::MemoryBuffer::getSTDIN();