diff --git a/include/clang/Driver/CC1AsOptions.td b/include/clang/Driver/CC1AsOptions.td
index 9fd855a..620d721 100644
--- a/include/clang/Driver/CC1AsOptions.td
+++ b/include/clang/Driver/CC1AsOptions.td
@@ -86,5 +86,8 @@
 
 def g : Flag<["-"], "g">, HelpText<"Generate source level debug information">;
 
+def fdebug_compilation_dir : Separate<["-"], "fdebug-compilation-dir">,
+  HelpText<"The compilation directory to embed in the debug info.">;
+
 def dwarf_debug_flags : Separate<["-"], "dwarf-debug-flags">,
   HelpText<"The string to embed in the Dwarf debug flags record.">;
diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index 2737c1a..bbc3ccc 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -1611,6 +1611,20 @@
   return true;
 }
 
+/// If the PWD environment variable is set, add a CC1 option to specify the
+/// debug compilation directory.
+static void addDebugCompDirArg(const ArgList &Args, ArgStringList &CmdArgs) {
+  if (const char *pwd = ::getenv("PWD")) {
+    // GCC also verifies that stat(pwd) and stat(".") have the same inode
+    // number. Not doing those because stats are slow, but we could.
+    if (llvm::sys::path::is_absolute(pwd)) {
+      std::string CompDir = pwd;
+      CmdArgs.push_back("-fdebug-compilation-dir");
+      CmdArgs.push_back(Args.MakeArgString(CompDir));
+    }
+  }
+}
+
 void Clang::ConstructJob(Compilation &C, const JobAction &JA,
                          const InputInfo &Output,
                          const InputInfoList &Inputs,
@@ -2362,15 +2376,8 @@
   if (ShouldDisableDwarfDirectory(Args, getToolChain()))
     CmdArgs.push_back("-fno-dwarf-directory-asm");
 
-  if (const char *pwd = ::getenv("PWD")) {
-    // GCC also verifies that stat(pwd) and stat(".") have the same inode
-    // number. Not doing those because stats are slow, but we could.
-    if (llvm::sys::path::is_absolute(pwd)) {
-      std::string CompDir = pwd;
-      CmdArgs.push_back("-fdebug-compilation-dir");
-      CmdArgs.push_back(Args.MakeArgString(CompDir));
-    }
-  }
+  // Add in -fdebug-compilation-dir if necessary.
+  addDebugCompDirArg(Args, CmdArgs);
 
   if (Arg *A = Args.getLastArg(options::OPT_ftemplate_depth_,
                                options::OPT_ftemplate_depth_EQ)) {
@@ -3295,13 +3302,17 @@
     SourceAction = SourceAction->getInputs()[0];
   }
 
-  // Forward -g, assuming we are dealing with an actual assembly file.
+  // Forward -g and handle debug info related flags, assuming we are dealing
+  // with an actual assembly file.
   if (SourceAction->getType() == types::TY_Asm ||
       SourceAction->getType() == types::TY_PP_Asm) {
     Args.ClaimAllArgs(options::OPT_g_Group);
     if (Arg *A = Args.getLastArg(options::OPT_g_Group))
       if (!A->getOption().matches(options::OPT_g0))
         CmdArgs.push_back("-g");
+
+    // Add the -fdebug-compilation-dir flag if needed.
+    addDebugCompDirArg(Args, CmdArgs);
   }
 
   // Optionally embed the -cc1as level arguments into the debug info, for build
diff --git a/test/Driver/debug-comp-dir.S b/test/Driver/debug-comp-dir.S
new file mode 100644
index 0000000..ca1ca30
--- /dev/null
+++ b/test/Driver/debug-comp-dir.S
@@ -0,0 +1,11 @@
+// RUN: cd %S && %clang -### -g %s -c 2>&1 | FileCheck -check-prefix=CHECK-PWD %s
+// CHECK-PWD: {{"-fdebug-compilation-dir" ".*Driver.*"}}
+
+// RUN: env PWD=/foo %clang -### -g %s -c 2>&1 | FileCheck -check-prefix=CHECK-FOO %s
+// CHECK-FOO: {{"-fdebug-compilation-dir" ".*foo"}}
+
+// "PWD=/foo gcc" wouldn't necessarily work. You would need to pick a different
+// path to the same directory (try a symlink).
+
+// This depends on host's behavior how $PWD would be set.
+// REQUIRES: shell
diff --git a/tools/driver/cc1as_main.cpp b/tools/driver/cc1as_main.cpp
index 87e3bfb..73be56c 100644
--- a/tools/driver/cc1as_main.cpp
+++ b/tools/driver/cc1as_main.cpp
@@ -83,6 +83,7 @@
   unsigned SaveTemporaryLabels : 1;
   unsigned GenDwarfForAssembly : 1;
   std::string DwarfDebugFlags;
+  std::string DebugCompilationDir;
 
   /// @}
   /// @name Frontend Options
@@ -181,6 +182,7 @@
   Opts.SaveTemporaryLabels = Args->hasArg(OPT_L);
   Opts.GenDwarfForAssembly = Args->hasArg(OPT_g);
   Opts.DwarfDebugFlags = Args->getLastArgValue(OPT_dwarf_debug_flags);
+  Opts.DebugCompilationDir = Args->getLastArgValue(OPT_fdebug_compilation_dir);
 
   // Frontend Options
   if (Args->hasArg(OPT_INPUT)) {
@@ -305,6 +307,8 @@
     Ctx.setGenDwarfForAssembly(true);
   if (!Opts.DwarfDebugFlags.empty())
     Ctx.setDwarfDebugFlags(StringRef(Opts.DwarfDebugFlags));
+  if (!Opts.DebugCompilationDir.empty())
+    Ctx.setCompilationDir(Opts.DebugCompilationDir);
 
   // Build up the feature string from the target feature list.
   std::string FS;