Index: clang/lib/Basic/Targets/AVR.cpp
===================================================================
--- clang/lib/Basic/Targets/AVR.cpp
+++ clang/lib/Basic/Targets/AVR.cpp
@@ -384,6 +384,9 @@
     auto It = llvm::find_if(
         AVRMcus, [&](const MCUInfo &Info) { return Info.Name == this->CPU; });
 
+    if (It->IsTiny)
+      Builder.defineMacro("__AVR_TINY__", "1");
+
     if (It != std::end(AVRMcus)) {
       Builder.defineMacro(It->DefineName);
       if (It->NumFlashBanks >= 1)
Index: clang/test/Preprocessor/avr-common.c
===================================================================
--- clang/test/Preprocessor/avr-common.c
+++ clang/test/Preprocessor/avr-common.c
@@ -1,6 +1,10 @@
 // RUN: %clang_cc1 -E -dM -triple avr-unknown-unknown /dev/null | FileCheck -match-full-lines %s
+// RUN: %clang_cc1 -E -dM -triple avr-unknown-unknown -target-cpu attiny4 /dev/null | FileCheck -match-full-lines %s --check-prefix TINY
 
 // CHECK: #define AVR 1
 // CHECK: #define __AVR 1
 // CHECK: #define __AVR__ 1
 // CHECK: #define __ELF__ 1
+// CHECK-NOT: __AVR_TINY__
+
+// TINY: #define __AVR_TINY__ 1