Index: clang/lib/Basic/Targets/AVR.cpp
===================================================================
--- clang/lib/Basic/Targets/AVR.cpp
+++ clang/lib/Basic/Targets/AVR.cpp
@@ -377,7 +377,9 @@
                                      MacroBuilder &Builder) const {
   Builder.defineMacro("AVR");
   Builder.defineMacro("__AVR");
+  Builder.defineMacro("__avr");
   Builder.defineMacro("__AVR__");
+  Builder.defineMacro("__avr__");
   Builder.defineMacro("__ELF__");
 
   if (!this->CPU.empty()) {
Index: clang/test/Preprocessor/avr-common.c
===================================================================
--- clang/test/Preprocessor/avr-common.c
+++ clang/test/Preprocessor/avr-common.c
@@ -4,3 +4,5 @@
 // CHECK: #define __AVR 1
 // CHECK: #define __AVR__ 1
 // CHECK: #define __ELF__ 1
+// CHECK: #define __avr 1
+// CHECK: #define __avr__ 1