diff --git a/clang/lib/Basic/Targets/AArch64.cpp b/clang/lib/Basic/Targets/AArch64.cpp
--- a/clang/lib/Basic/Targets/AArch64.cpp
+++ b/clang/lib/Basic/Targets/AArch64.cpp
@@ -194,6 +194,14 @@
     Builder.defineMacro("__LP64__");
   }
 
+  std::string CodeModel = getTargetOpts().CodeModel;
+  if (CodeModel == "default")
+    CodeModel = "small";
+  for (auto& c : CodeModel) {
+    c = toupper(c);
+  }
+  Builder.defineMacro("__AARCH64_CMODEL_" + CodeModel + "__");
+
   // ACLE predefines. Many can only have one possible value on v8 AArch64.
   Builder.defineMacro("__ARM_ACLE", "200");
   Builder.defineMacro("__ARM_ARCH", "8");
diff --git a/clang/test/Preprocessor/init.c b/clang/test/Preprocessor/init.c
--- a/clang/test/Preprocessor/init.c
+++ b/clang/test/Preprocessor/init.c
@@ -285,6 +285,7 @@
 // AARCH64-NOT:#define __AARCH64EB__ 1
 // AARCH64:#define __AARCH64EL__ 1
 // AARCH64-NOT:#define __AARCH_BIG_ENDIAN 1
+// AARCH64:#define __AARCH64_CMODEL_SMALL__ 1
 // AARCH64:#define __ARM_64BIT_STATE 1
 // AARCH64:#define __ARM_ARCH 8
 // AARCH64:#define __ARM_ARCH_ISA_A64 1