Index: include/clang/Driver/CC1AsOptions.td
===================================================================
--- include/clang/Driver/CC1AsOptions.td
+++ include/clang/Driver/CC1AsOptions.td
@@ -85,6 +85,13 @@
 
 def g : Flag<["-"], "g">, HelpText<"Generate source level debug information">;
 
+def gdwarf_2 : Flag<["-"], "gdwarf-2">,
+  HelpText<"Generate source level debug information with dwarf version 2">;
+def gdwarf_3 : Flag<["-"], "gdwarf-3">,
+  HelpText<"Generate source level debug information with dwarf version 3">;
+def gdwarf_4 : Flag<["-"], "gdwarf-4">,
+  HelpText<"Generate source level debug information with dwarf version 4">;
+
 def fdebug_compilation_dir : Separate<["-"], "fdebug-compilation-dir">,
   HelpText<"The compilation directory to embed in the debug info.">;
 
Index: lib/Driver/Tools.cpp
===================================================================
--- lib/Driver/Tools.cpp
+++ lib/Driver/Tools.cpp
@@ -1723,6 +1723,8 @@
           // -I. The next arg will be the include directory.
           if (Value == "-I")
             TakeNextArg = true;
+        } else if (Value.startswith("-gdwarf-")) {
+          CmdArgs.push_back(Value.data());
         } else {
           D.Diag(diag::err_drv_unsupported_option_argument)
             << A->getOption().getName() << Value;
@@ -4068,6 +4070,13 @@
       if (!A->getOption().matches(options::OPT_g0))
         CmdArgs.push_back("-g");
 
+    if (Args.hasArg(options::OPT_gdwarf_2))
+      CmdArgs.push_back("-gdwarf-2");
+    if (Args.hasArg(options::OPT_gdwarf_3))
+      CmdArgs.push_back("-gdwarf-3");
+    if (Args.hasArg(options::OPT_gdwarf_4))
+      CmdArgs.push_back("-gdwarf-4");
+
     // Add the -fdebug-compilation-dir flag if needed.
     addDebugCompDirArg(Args, CmdArgs);
 
Index: test/Driver/integrated-as.s
===================================================================
--- test/Driver/integrated-as.s
+++ test/Driver/integrated-as.s
@@ -38,3 +38,18 @@
 // COMPRESS_DEBUG_QUIET-NOT: warning: DWARF compression is not implemented
 // COMPRESS_DEBUG_QUIET-NOT: warning: argument unused during compilation
 // COMPRESS_DEBUG_QUIET: -cc1as
+
+// RUN: %clang -### -c -integrated-as %s -gdwarf-2 2>&1 | FileCheck --check-prefix=DWARF2 %s
+// DWARF2: "-g" "-gdwarf-2"
+
+// RUN: %clang -### -c -integrated-as %s -gdwarf-3 2>&1 | FileCheck --check-prefix=DWARF3 %s
+// DWARF3: "-g" "-gdwarf-3"
+
+// RUN: %clang -### -c -integrated-as %s -gdwarf-4 2>&1 | FileCheck --check-prefix=DWARF4 %s
+// DWARF4: "-g" "-gdwarf-4"
+
+// RUN: %clang -### -c -integrated-as %s -Xassembler -gdwarf-2 2>&1 | FileCheck --check-prefix=DWARF2XASSEMBLER %s
+// DWARF2XASSEMBLER: "-gdwarf-2"
+
+// RUN: %clang -### -c -integrated-as %s -Wa,-gdwarf-2 2>&1 | FileCheck --check-prefix=DWARF2WA %s
+// DWARF2WA: "-gdwarf-2"
Index: tools/driver/cc1as_main.cpp
===================================================================
--- tools/driver/cc1as_main.cpp
+++ tools/driver/cc1as_main.cpp
@@ -85,6 +85,7 @@
   unsigned NoInitialTextSection : 1;
   unsigned SaveTemporaryLabels : 1;
   unsigned GenDwarfForAssembly : 1;
+  unsigned DwarfVersion;
   std::string DwarfDebugFlags;
   std::string DwarfDebugProducer;
   std::string DebugCompilationDir;
@@ -135,6 +136,7 @@
     ShowEncoding = 0;
     RelaxAll = 0;
     NoExecStack = 0;
+    DwarfVersion = 3;
   }
 
   static bool CreateFromArgs(AssemblerInvocation &Res, const char **ArgBegin,
@@ -186,6 +188,13 @@
   Opts.NoInitialTextSection = Args->hasArg(OPT_n);
   Opts.SaveTemporaryLabels = Args->hasArg(OPT_msave_temp_labels);
   Opts.GenDwarfForAssembly = Args->hasArg(OPT_g);
+  if (Args->hasArg(OPT_gdwarf_2))
+    Opts.DwarfVersion = 2;
+  if (Args->hasArg(OPT_gdwarf_3))
+    Opts.DwarfVersion = 3;
+  if (Args->hasArg(OPT_gdwarf_4))
+    Opts.DwarfVersion = 4;
+
   Opts.DwarfDebugFlags = Args->getLastArgValue(OPT_dwarf_debug_flags);
   Opts.DwarfDebugProducer = Args->getLastArgValue(OPT_dwarf_debug_producer);
   Opts.DebugCompilationDir = Args->getLastArgValue(OPT_fdebug_compilation_dir);
@@ -318,6 +327,7 @@
     Ctx.setCompilationDir(Opts.DebugCompilationDir);
   if (!Opts.MainFileName.empty())
     Ctx.setMainFileName(StringRef(Opts.MainFileName));
+  Ctx.setDwarfVersion(Opts.DwarfVersion);
 
   // Build up the feature string from the target feature list.
   std::string FS;