Index: llvm/trunk/include/llvm/MC/MCContext.h
===================================================================
--- llvm/trunk/include/llvm/MC/MCContext.h
+++ llvm/trunk/include/llvm/MC/MCContext.h
@@ -502,11 +502,8 @@
     /// Add an entry to the debug prefix map.
     void addDebugPrefixMapEntry(const std::string &From, const std::string &To);
 
-    // Remaps the given path in-place as per the debug prefix map.
-    void RemapDebugPath(std::string *Path);
-
-    // Remaps the compilation dir as per the debug prefix map.
-    void RemapCompilationDir();
+    // Remaps all debug directory paths in-place as per the debug prefix map.
+    void RemapDebugPaths();
 
     /// Get the main file name for use in error messages and debug
     /// info. This can be set to ensure we've got the correct file name
Index: llvm/trunk/include/llvm/MC/MCDwarf.h
===================================================================
--- llvm/trunk/include/llvm/MC/MCDwarf.h
+++ llvm/trunk/include/llvm/MC/MCDwarf.h
@@ -301,8 +301,6 @@
                                FileNumber));
   }
 
-  void RemapDwarfDirs(MCContext &Context);
-
   void setRootFile(StringRef Directory, StringRef FileName,
                    MD5::MD5Result *Checksum, Optional<StringRef> Source) {
     Header.CompilationDir = Directory;
Index: llvm/trunk/lib/MC/MCContext.cpp
===================================================================
--- llvm/trunk/lib/MC/MCContext.cpp
+++ llvm/trunk/lib/MC/MCContext.cpp
@@ -540,19 +540,26 @@
   DebugPrefixMap.insert(std::make_pair(From, To));
 }
 
-void MCContext::RemapDebugPath(std::string *Path) {
-  for (const auto &Entry : DebugPrefixMap)
-    if (StringRef(*Path).startswith(Entry.first)) {
-      std::string RemappedPath =
-          (Twine(Entry.second) + Path->substr(Entry.first.size())).str();
-      Path->swap(RemappedPath);
-    }
-}
+void MCContext::RemapDebugPaths() {
+  const auto &DebugPrefixMap = this->DebugPrefixMap;
+  const auto RemapDebugPath = [&DebugPrefixMap](std::string &Path) {
+    for (const auto &Entry : DebugPrefixMap)
+      if (StringRef(Path).startswith(Entry.first)) {
+        std::string RemappedPath =
+            (Twine(Entry.second) + Path.substr(Entry.first.size())).str();
+        Path.swap(RemappedPath);
+      }
+  };
 
-void MCContext::RemapCompilationDir() {
+  // Remap compilation directory.
   std::string CompDir = CompilationDir.str();
-  RemapDebugPath(&CompDir);
+  RemapDebugPath(CompDir);
   CompilationDir = CompDir;
+
+  // Remap MCDwarfDirs in all compilation units.
+  for (auto &CUIDTablePair : MCDwarfLineTablesCUMap)
+    for (auto &Dir : CUIDTablePair.second.getMCDwarfDirs())
+      RemapDebugPath(Dir);
 }
 
 //===----------------------------------------------------------------------===//
Index: llvm/trunk/lib/MC/MCDwarf.cpp
===================================================================
--- llvm/trunk/lib/MC/MCDwarf.cpp
+++ llvm/trunk/lib/MC/MCDwarf.cpp
@@ -251,9 +251,7 @@
 
   // Handle the rest of the Compile Units.
   for (const auto &CUIDTablePair : LineTables) {
-    auto &LineTable = context.getMCDwarfLineTable(CUIDTablePair.first);
-    LineTable.RemapDwarfDirs(MCOS->getContext());
-    LineTable.EmitCU(MCOS, Params, LineStr);
+    CUIDTablePair.second.EmitCU(MCOS, Params, LineStr);
   }
 
   if (LineStr)
@@ -634,11 +632,6 @@
   return FileNumber;
 }
 
-void MCDwarfLineTable::RemapDwarfDirs(MCContext &Context) {
-  for (auto &Dir : Header.MCDwarfDirs)
-    Context.RemapDebugPath(&Dir);
-}
-
 /// Utility function to emit the encoding to a streamer.
 void MCDwarfLineAddr::Emit(MCStreamer *MCOS, MCDwarfLineTableParams Params,
                            int64_t LineDelta, uint64_t AddrDelta) {
Index: llvm/trunk/lib/MC/MCObjectStreamer.cpp
===================================================================
--- llvm/trunk/lib/MC/MCObjectStreamer.cpp
+++ llvm/trunk/lib/MC/MCObjectStreamer.cpp
@@ -661,8 +661,7 @@
 }
 
 void MCObjectStreamer::FinishImpl() {
-  // Remap the compilation directory before emitting.
-  getContext().RemapCompilationDir();
+  getContext().RemapDebugPaths();
 
   // If we are generating dwarf for assembly source files dump out the sections.
   if (getContext().getGenDwarfForAssembly())
Index: llvm/trunk/test/MC/ELF/debug-prefix-map.s
===================================================================
--- llvm/trunk/test/MC/ELF/debug-prefix-map.s
+++ llvm/trunk/test/MC/ELF/debug-prefix-map.s
@@ -4,9 +4,13 @@
 
 // RUN: llvm-mc -triple=x86_64-linux-unknown -g src.s -filetype=obj -o out.o
 // RUN: llvm-dwarfdump -v -debug-info out.o | FileCheck --check-prefix=NO_MAP %s
+
 // RUN: llvm-mc -triple=x86_64-linux-unknown -g src.s -filetype=obj -o out.o -fdebug-prefix-map=%t.foo=src_root
 // RUN: llvm-dwarfdump -v -debug-info out.o | FileCheck --check-prefix=MAP --implicit-check-not ".foo" %s
 
+// RUN: llvm-mc -triple=x86_64-linux-unknown -g %t.foo/src.s -filetype=obj -o out.o -fdebug-prefix-map=%t.foo=/src_root
+// RUN: llvm-dwarfdump -v -debug-info out.o | FileCheck --check-prefix=MAP_ABS --implicit-check-not ".foo" %s
+
 f:
   nop
 
@@ -15,3 +19,7 @@
 // MAP: DW_AT_name [DW_FORM_string] ("src.s")
 // MAP: DW_AT_comp_dir [DW_FORM_string] ("src_root")
 // MAP: DW_AT_decl_file [DW_FORM_data4] ("src_root{{(/|\\)}}src.s")
+
+// MAP_ABS: DW_AT_name [DW_FORM_string] ("{{/|\\}}src_root{{(/|\\)}}src.s")
+// MAP_ABS: DW_AT_comp_dir [DW_FORM_string] ("{{/|\\}}src_root")
+// MAP_ABS: DW_AT_decl_file [DW_FORM_data4] ("{{/|\\}}src_root{{(/|\\)}}src.s")