diff --git a/clang/utils/TableGen/SveEmitter.cpp b/clang/utils/TableGen/SveEmitter.cpp
--- a/clang/utils/TableGen/SveEmitter.cpp
+++ b/clang/utils/TableGen/SveEmitter.cpp
@@ -1282,6 +1282,7 @@
   OS << "#ifdef __cplusplus\n";
   OS << "} // extern \"C\"\n";
   OS << "#endif\n\n";
+  OS << "#undef __ai\n\n";
   OS << "#endif /*__ARM_FEATURE_SVE */\n\n";
   OS << "#endif /* __ARM_SVE_H */\n";
 }