Index: include/llvm/Demangle/Compiler.h
===================================================================
--- include/llvm/Demangle/Compiler.h
+++ include/llvm/Demangle/Compiler.h
@@ -14,6 +14,8 @@
 #ifndef LLVM_DEMANGLE_COMPILER_H
 #define LLVM_DEMANGLE_COMPILER_H
 
+#include "llvm/Config/llvm-config.h"
+
 #ifdef _MSC_VER
 // snprintf is implemented in VS 2015
 #if _MSC_VER < 1900