diff --git a/clang/lib/Basic/Targets/PPC.cpp b/clang/lib/Basic/Targets/PPC.cpp
--- a/clang/lib/Basic/Targets/PPC.cpp
+++ b/clang/lib/Basic/Targets/PPC.cpp
@@ -257,6 +257,9 @@
     Builder.defineMacro("__ppc64__");
     Builder.defineMacro("__PPC64__");
   }
+  if (getTriple().isOSAIX()) {
+    Builder.defineMacro("__THW_PPC__");
+  }
 
   // Target properties.
   if (getTriple().getArch() == llvm::Triple::ppc64le ||
diff --git a/clang/test/Preprocessor/init-ppc.c b/clang/test/Preprocessor/init-ppc.c
--- a/clang/test/Preprocessor/init-ppc.c
+++ b/clang/test/Preprocessor/init-ppc.c
@@ -539,6 +539,7 @@
 // PPC-AIX:#define __SIZE_TYPE__ long unsigned int
 // PPC-AIX:#define __SIZE_WIDTH__ 32
 // PPC-AIX:#define __THW_BIG_ENDIAN__ 1
+// PPC-AIX:#define __THW_PPC__ 1
 // PPC-AIX:#define __TOS_AIX__ 1
 // PPC-AIX:#define __UINT16_C_SUFFIX__
 // PPC-AIX:#define __UINT16_MAX__ 65535