Index: flang/runtime/complex-reduction.h
===================================================================
--- flang/runtime/complex-reduction.h
+++ flang/runtime/complex-reduction.h
@@ -20,7 +20,7 @@
 
 struct CppDescriptor; /* dummy type name for Fortran::runtime::Descriptor */
 
-#ifdef _MSC_VER
+#if defined _MSC_VER && ! __clang_major__ >= 12
 typedef _Fcomplex float_Complex_t;
 typedef _Dcomplex double_Complex_t;
 typedef _Lcomplex long_double_Complex_t;