Index: lib/Basic/Targets.cpp
===================================================================
--- lib/Basic/Targets.cpp
+++ lib/Basic/Targets.cpp
@@ -208,6 +208,10 @@
   if (Triple.isOSDarwin())
     Builder.defineMacro("__MACH__");
 
+  // The Watch ABI uses Dwarf EH.
+  if(Triple.isWatchABI())
+    Builder.defineMacro("__ARM_DWARF_EH__");
+
   PlatformMinVersion = VersionTuple(Maj, Min, Rev);
 }
 
Index: test/Preprocessor/arm-target-features.c
===================================================================
--- test/Preprocessor/arm-target-features.c
+++ test/Preprocessor/arm-target-features.c
@@ -217,6 +217,7 @@
 // ARMV7K:#define __ARM_ARCH 7
 // ARMV7K:#define __ARM_ARCH_EXT_IDIV__ 1
 // ARMV7K:#define __ARM_ARCH_PROFILE 'A'
+// ARMV7K:#define __ARM_DWARF_EH__ 1
 // ARMV7K:#define __ARM_FEATURE_DSP 1
 // ARMV7K:#define __ARM_FP 0xE
 // ARMV7K:#define __ARM_PCS_VFP 1