Index: lib/Basic/Targets.cpp
===================================================================
--- lib/Basic/Targets.cpp
+++ lib/Basic/Targets.cpp
@@ -1878,7 +1878,11 @@
 
   void getTargetDefines(const LangOptions &Opts,
                         MacroBuilder &Builder) const override {
-    Builder.defineMacro("__R600__");
+    if (getTriple().getArch() == llvm::Triple::amdgcn)
+      Builder.defineMacro("__AMDGCN__");
+    else
+      Builder.defineMacro("__R600__");
+
     if (hasFMAF)
       Builder.defineMacro("__HAS_FMAF__");
     if (hasLDEXPF)
Index: test/Preprocessor/predefined-arch-macros.c
===================================================================
--- test/Preprocessor/predefined-arch-macros.c
+++ test/Preprocessor/predefined-arch-macros.c
@@ -1824,3 +1824,17 @@
 // RUN:   | FileCheck %s -check-prefix=CHECK_SYSTEMZ_ZVECTOR
 //
 // CHECK_SYSTEMZ_ZVECTOR: #define __VEC__ 10301
+
+// Begin amdgcn tests ----------------
+//
+// RUN: %clang -march=amdgcn -E -dM %s -o - 2>&1 \
+// RUN:     -target amdgcn-unknown-unknown \
+// RUN:   | FileCheck %s -check-prefix=CHECK_AMDGCN
+// CHECK_AMDGCN: #define __AMDGCN__ 1
+
+// Begin r600 tests ----------------
+//
+// RUN: %clang -march=amdgcn -E -dM %s -o - 2>&1 \
+// RUN:     -target r600-unknown-unknown \
+// RUN:   | FileCheck %s -check-prefix=CHECK_R600
+// CHECK_R600: #define __R600__ 1