Add 'OverridenFilesKeepOriginalName' field in SourceManager which if true the SourceManager

should report the original file name for contents of files that were overriden by other files,
otherwise it should report the name of the new file. Default is true.

Also add similar field in PreprocessorOptions and pass similar parameter in ASTUnit::LoadFromCommandLine.

llvm-svn: 127289

clang/lib/Frontend/InitPreprocessor.cpp

@@ -531,20 +531,13 @@ static void InitializeFileRemapping(Diagnostic &Diags,
       continue;
     }
     
-    // Load the contents of the file we're mapping to.
-    std::string ErrorStr;
-    const llvm::MemoryBuffer *Buffer
-      = FileMgr.getBufferForFile(ToFile->getName(), &ErrorStr);
-    if (!Buffer) {
-      Diags.Report(diag::err_fe_error_opening)
-        << Remap->second << ErrorStr;
-      continue;
-    }
-    
     // Override the contents of the "from" file with the contents of
     // the "to" file.
-    SourceMgr.overrideFileContents(FromFile, Buffer);
+    SourceMgr.overrideFileContents(FromFile, ToFile);
   }
+
+  SourceMgr.setOverridenFilesKeepOriginalName(
+                                        InitOpts.RemappedFilesKeepOriginalName);
 }
 
 /// InitializePreprocessor - Initialize the preprocessor getting it and the