Index: cfe/trunk/lib/Driver/ToolChains/Clang.cpp
===================================================================
--- cfe/trunk/lib/Driver/ToolChains/Clang.cpp
+++ cfe/trunk/lib/Driver/ToolChains/Clang.cpp
@@ -2152,6 +2152,9 @@
           }
           CmdArgs.push_back(Value.data());
           TakeNextArg = true;
+      } else if (Value == "-fdebug-compilation-dir") {
+        CmdArgs.push_back("-fdebug-compilation-dir");
+        TakeNextArg = true;
       } else {
         D.Diag(diag::err_drv_unsupported_option_argument)
             << A->getOption().getName() << Value;
Index: cfe/trunk/test/Driver/integrated-as.s
===================================================================
--- cfe/trunk/test/Driver/integrated-as.s
+++ cfe/trunk/test/Driver/integrated-as.s
@@ -50,3 +50,9 @@
 
 // RUN: %clang -### -target x86_64--- -x assembler -c -fPIC -integrated-as %s 2>&1 | FileCheck --check-prefix=PIC %s
 // PIC: "-mrelocation-model" "pic"
+
+// RUN: %clang -### -target x86_64--- -c -integrated-as %s -Wa,-fdebug-compilation-dir,. 2>&1 | FileCheck --check-prefix=WA_DEBUGDIR %s
+// WA_DEBUGDIR: "-fdebug-compilation-dir" "."
+
+// RUN: %clang -### -target x86_64--- -c -integrated-as %s -Xassembler -fdebug-compilation-dir -Xassembler . 2>&1 | FileCheck --check-prefix=XA_DEBUGDIR %s
+// XA_DEBUGDIR: "-fdebug-compilation-dir" "."