Index: include/llvm/MC/MCContext.h
===================================================================
--- include/llvm/MC/MCContext.h
+++ include/llvm/MC/MCContext.h
@@ -137,6 +137,9 @@
     /// The compilation directory to use for DW_AT_comp_dir.
     SmallString<128> CompilationDir;
 
+    /// Prefix replacement map for source file information.
+    std::map<const std::string, const std::string> DebugPrefixMap;
+
     /// The main file name if passed in explicitly.
     std::string MainFileName;
 
@@ -490,6 +493,14 @@
     /// Set the compilation directory for DW_AT_comp_dir
     void setCompilationDir(StringRef S) { CompilationDir = S.str(); }
 
+    /// Get the debug prefix map.
+    const std::map<const std::string, const std::string> &getDebugPrefixMap() const {
+      return DebugPrefixMap;
+    }
+
+    /// Add an entry to the debug prefix map.
+    void addDebugPrefixMapEntry(const std::string &From, const std::string &To);
+
     /// 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
     /// after preprocessing or for -save-temps.
Index: lib/MC/MCContext.cpp
===================================================================
--- lib/MC/MCContext.cpp
+++ lib/MC/MCContext.cpp
@@ -535,6 +535,10 @@
   return *new (MCSubtargetAllocator.Allocate()) MCSubtargetInfo(STI);
 }
 
+void MCContext::addDebugPrefixMapEntry(const std::string &From, const std::string &To) {
+  DebugPrefixMap.insert(std::make_pair(From, To));
+}
+
 //===----------------------------------------------------------------------===//
 // Dwarf Management
 //===----------------------------------------------------------------------===//
Index: lib/MC/MCDwarf.cpp
===================================================================
--- lib/MC/MCDwarf.cpp
+++ lib/MC/MCDwarf.cpp
@@ -307,6 +307,13 @@
   OS.EmitValue(ABS, Size);
 }
 
+static std::string remapDebugPath(MCStreamer *MCOS, StringRef Path) {
+  for (const auto &Entry : MCOS->getContext().getDebugPrefixMap())
+    if (Path.startswith(Entry.first))
+      return (Twine(Entry.second) + Path.substr(Entry.first.size())).str();
+  return Path;
+}
+
 void MCDwarfLineStr::emitSection(MCStreamer *MCOS) {
   // Switch to the .debug_line_str section.
   MCOS->SwitchSection(
@@ -332,7 +339,8 @@
 void MCDwarfLineTableHeader::emitV2FileDirTables(MCStreamer *MCOS) const {
   // First the directory table.
   for (auto &Dir : MCDwarfDirs) {
-    MCOS->EmitBytes(Dir);                // The DirectoryName, and...
+    const std::string RemappedDir = remapDebugPath(MCOS, Dir);
+    MCOS->EmitBytes(RemappedDir);        // The DirectoryName, and...
     MCOS->EmitBytes(StringRef("\0", 1)); // its null terminator.
   }
   MCOS->EmitIntValue(0, 1); // Terminate the directory list.
@@ -391,17 +399,21 @@
   // Try not to emit an empty compilation directory.
   const StringRef CompDir =
       CompilationDir.empty() ? CtxCompilationDir : StringRef(CompilationDir);
+  const std::string RemappedCompDir = remapDebugPath(MCOS, CompDir);
   if (LineStr) {
     // Record path strings, emit references here.
-    LineStr->emitRef(MCOS, CompDir);
-    for (auto &Dir : MCDwarfDirs)
-      LineStr->emitRef(MCOS, Dir);
+    LineStr->emitRef(MCOS, RemappedCompDir);
+    for (const auto &Dir : MCDwarfDirs) {
+      const std::string RemappedDir = remapDebugPath(MCOS, Dir);
+      LineStr->emitRef(MCOS, RemappedDir);
+    }
   } else {
     // The list of directory paths.  Compilation directory comes first.
-    MCOS->EmitBytes(CompDir);
+    MCOS->EmitBytes(RemappedCompDir);
     MCOS->EmitBytes(StringRef("\0", 1));
-    for (auto &Dir : MCDwarfDirs) {
-      MCOS->EmitBytes(Dir);                // The DirectoryName, and...
+    for (const auto &Dir : MCDwarfDirs) {
+      const std::string RemappedDir = remapDebugPath(MCOS, Dir);
+      MCOS->EmitBytes(RemappedDir);        // The DirectoryName, and...
       MCOS->EmitBytes(StringRef("\0", 1)); // its null terminator.
     }
   }
@@ -955,7 +967,8 @@
   // and file table entries.
   const SmallVectorImpl<std::string> &MCDwarfDirs = context.getMCDwarfDirs();
   if (MCDwarfDirs.size() > 0) {
-    MCOS->EmitBytes(MCDwarfDirs[0]);
+    const std::string RemappedDir = remapDebugPath(MCOS, MCDwarfDirs[0]);
+    MCOS->EmitBytes(RemappedDir);
     MCOS->EmitBytes(sys::path::get_separator());
   }
   const SmallVectorImpl<MCDwarfFile> &MCDwarfFiles =
@@ -965,7 +978,8 @@
 
   // AT_comp_dir, the working directory the assembly was done in.
   if (!context.getCompilationDir().empty()) {
-    MCOS->EmitBytes(context.getCompilationDir());
+    const std::string RemappedCompDir = remapDebugPath(MCOS, context.getCompilationDir());
+    MCOS->EmitBytes(RemappedCompDir);
     MCOS->EmitIntValue(0, 1); // NULL byte to terminate the string.
   }
 
Index: test/MC/ELF/debug-prefix-map.s
===================================================================
--- /dev/null
+++ test/MC/ELF/debug-prefix-map.s
@@ -0,0 +1,18 @@
+// RUN: mkdir -p %t.foo
+// RUN: cp %s %t.foo/src.s
+// RUN: cd %t.foo
+
+// 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
+
+// NO_MAP: DW_AT_comp_dir [DW_FORM_string] ("{{.*}}.foo")
+
+// 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
+
+// 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")
+
+f:
+  nop
Index: tools/llvm-mc/llvm-mc.cpp
===================================================================
--- tools/llvm-mc/llvm-mc.cpp
+++ tools/llvm-mc/llvm-mc.cpp
@@ -152,6 +152,11 @@
 DebugCompilationDir("fdebug-compilation-dir",
                     cl::desc("Specifies the debug info's compilation dir"));
 
+static cl::list<std::string>
+DebugPrefixMap("fdebug-prefix-map",
+               cl::desc("Map file source paths in debug info"),
+               cl::value_desc("= separated key-value pairs"));
+
 static cl::opt<std::string>
 MainFileName("main-file-name",
              cl::desc("Specifies the name we should consider the input file"));
@@ -387,6 +392,10 @@
     if (!sys::fs::current_path(CWD))
       Ctx.setCompilationDir(CWD);
   }
+  for (const auto &Arg : DebugPrefixMap) {
+    const auto &KV = StringRef(Arg).split('=');
+    Ctx.addDebugPrefixMapEntry(KV.first, KV.second);
+  }
   if (!MainFileName.empty())
     Ctx.setMainFileName(MainFileName);
   if (GenDwarfForAssembly && DwarfVersion >= 5) {