Index: cfe/trunk/lib/CodeGen/CGDebugInfo.h
===================================================================
--- cfe/trunk/lib/CodeGen/CGDebugInfo.h
+++ cfe/trunk/lib/CodeGen/CGDebugInfo.h
@@ -538,9 +538,16 @@
   /// Get the source of the given file ID.
   Optional<StringRef> getSource(const SourceManager &SM, FileID FID);
 
-  /// Get the file debug info descriptor for the input location.
+  /// Convenience function to get the file debug info descriptor for the input
+  /// location.
   llvm::DIFile *getOrCreateFile(SourceLocation Loc);
 
+  /// Create a file debug info descriptor for a source file.
+  llvm::DIFile *
+  createFile(StringRef FileName,
+             Optional<llvm::DIFile::ChecksumInfo<StringRef>> CSInfo,
+             Optional<StringRef> Source);
+
   /// Get the file info for main compile unit.
   llvm::DIFile *getOrCreateMainFile();
 
Index: cfe/trunk/lib/CodeGen/CGDebugInfo.cpp
===================================================================
--- cfe/trunk/lib/CodeGen/CGDebugInfo.cpp
+++ cfe/trunk/lib/CodeGen/CGDebugInfo.cpp
@@ -429,7 +429,13 @@
   Optional<llvm::DIFile::ChecksumInfo<StringRef>> CSInfo;
   if (CSKind)
     CSInfo.emplace(*CSKind, Checksum);
+  return createFile(FileName, CSInfo, getSource(SM, SM.getFileID(Loc)));
+}
 
+llvm::DIFile *
+CGDebugInfo::createFile(StringRef FileName,
+                        Optional<llvm::DIFile::ChecksumInfo<StringRef>> CSInfo,
+                        Optional<StringRef> Source) {
   StringRef Dir;
   StringRef File;
   std::string RemappedFile = remapDIPath(FileName);
@@ -460,16 +466,13 @@
     Dir = CurDir;
     File = RemappedFile;
   }
-  llvm::DIFile *F =
-      DBuilder.createFile(File, Dir, CSInfo,
-                          getSource(SM, SM.getFileID(Loc)));
-
+  llvm::DIFile *F = DBuilder.createFile(File, Dir, CSInfo, Source);
   DIFileCache[FileName.data()].reset(F);
   return F;
 }
 
 llvm::DIFile *CGDebugInfo::getOrCreateMainFile() {
-  return DBuilder.createFile(
+  return createFile(
       remapDIPath(TheCU->getFilename()), remapDIPath(TheCU->getDirectory()),
       TheCU->getFile()->getChecksum(),
       CGM.getCodeGenOpts().EmbedSource ? TheCU->getSource() : None);
@@ -607,9 +610,7 @@
   auto &CGOpts = CGM.getCodeGenOpts();
   TheCU = DBuilder.createCompileUnit(
       LangTag,
-      DBuilder.createFile(remapDIPath(MainFileName),
-                          remapDIPath(getCurrentDirname()), CSInfo,
-                          getSource(SM, SM.getMainFileID())),
+      createFile(MainFileName, CSInfo, getSource(SM, SM.getMainFileID())),
       CGOpts.EmitVersionIdentMetadata ? Producer : "",
       LO.Optimize || CGOpts.PrepareForLTO || CGOpts.PrepareForThinLTO,
       CGOpts.DwarfDebugFlags, RuntimeVers,
Index: cfe/trunk/test/CodeGen/debug-info-compilation-dir.c
===================================================================
--- cfe/trunk/test/CodeGen/debug-info-compilation-dir.c
+++ cfe/trunk/test/CodeGen/debug-info-compilation-dir.c
@@ -1,4 +1,6 @@
-// RUN: %clang_cc1 -fdebug-compilation-dir /nonsense -emit-llvm -debug-info-kind=limited %s -o - | FileCheck -check-prefix=CHECK-NONSENSE %s
+// RUN: mkdir -p %t.dir && cd %t.dir
+// RUN: cp %s rel.c
+// RUN: %clang_cc1 -fdebug-compilation-dir /nonsense -emit-llvm -debug-info-kind=limited rel.c -o - | FileCheck -check-prefix=CHECK-NONSENSE %s
 // CHECK-NONSENSE: nonsense
 
 // RUN: %clang_cc1 -emit-llvm -debug-info-kind=limited %s -o - | FileCheck -check-prefix=CHECK-DIR %s
Index: cfe/trunk/test/PCH/debug-info-pch-path.c
===================================================================
--- cfe/trunk/test/PCH/debug-info-pch-path.c
+++ cfe/trunk/test/PCH/debug-info-pch-path.c
@@ -24,7 +24,7 @@
 // CHECK-REL-NODIR: !DICompileUnit(
 // CHECK-REL-NODIR-SAME:           file: ![[PCH:[0-9]+]]
 // CHECK-REL-NODIR-SAME:           splitDebugFilename: "prefix.pch"
-// CHECK-REL-NODIR: ![[PCH]] = !DIFile({{.*}}directory: "[[DIR]]"
+// CHECK-REL-NODIR: ![[PCH]] = !DIFile({{.*}}directory: "[[DIR]]
 
 // ---------------------------------------------------------------------
 // Relative PCH in a subdirectory.
@@ -71,4 +71,4 @@
 // CHECK-ABS: !DICompileUnit(
 // CHECK-ABS-SAME:           file: ![[PCH:[0-9]+]]
 // CHECK-ABS-SAME:           splitDebugFilename: "prefix.pch"
-// CHECK-ABS: ![[PCH]] = !DIFile({{.*}}directory: "[[DIR]]"
+// CHECK-ABS: ![[PCH]] = !DIFile({{.*}}directory: "[[DIR]]