diff --git a/gcc/config.gcc b/gcc/config.gcc
index 9cecc140c83..b3b84374fd0 100644
--- a/gcc/config.gcc
+++ b/gcc/config.gcc
@@ -2121,6 +2121,8 @@ i[34567]86-*-cygwin*)
 	extra_objs="${extra_objs} winnt.o winnt-stubs.o"
 	c_target_objs="${c_target_objs} msformat-c.o"
 	cxx_target_objs="${cxx_target_objs} winnt-cxx.o msformat-c.o"
+	d_target_objs="${d_target_objs} winnt-d.o"
+	target_has_targetdm="yes"
 	if test x$enable_threads = xyes; then
 		thread_file='posix'
 	fi
@@ -2137,6 +2139,8 @@ x86_64-*-cygwin*)
 	extra_objs="${extra_objs} winnt.o winnt-stubs.o"
 	c_target_objs="${c_target_objs} msformat-c.o"
 	cxx_target_objs="${cxx_target_objs} winnt-cxx.o msformat-c.o"
+	d_target_objs="${d_target_objs} winnt-d.o"
+	target_has_targetdm="yes"
 	if test x$enable_threads = xyes; then
 		thread_file='posix'
 	fi
@@ -2149,7 +2153,9 @@ i[34567]86-*-mingw* | x86_64-*-mingw*)
 	xm_file=i386/xm-mingw32.h
 	c_target_objs="${c_target_objs} winnt-c.o"
 	cxx_target_objs="${cxx_target_objs} winnt-c.o"
+	d_target_objs="${d_target_objs} winnt-d.o"
 	target_has_targetcm="yes"
+	target_has_targetdm="yes"
 	case ${target} in
 		x86_64-*-* | *-w64-*)
 			need_64bit_isa=yes
diff --git a/gcc/config/i386/cygwin.h b/gcc/config/i386/cygwin.h
index db0a3cc0b35..f28c6974cdc 100644
--- a/gcc/config/i386/cygwin.h
+++ b/gcc/config/i386/cygwin.h
@@ -29,6 +29,14 @@ along with GCC; see the file COPYING3.  If not see
     }								\
   while (0)
 
+#define EXTRA_TARGET_D_OS_VERSIONS()				\
+  do								\
+    {								\
+      builtin_version ("Cygwin");				\
+      builtin_version ("Posix");				\
+    }								\
+  while (0)
+
 #undef CPP_SPEC
 #define CPP_SPEC "%(cpp_cpu) %{posix:-D_POSIX_SOURCE} \
   %{!ansi:-Dunix} \
diff --git a/gcc/config/i386/mingw32.h b/gcc/config/i386/mingw32.h
index 1a6a3a07ca6..0589d39230d 100644
--- a/gcc/config/i386/mingw32.h
+++ b/gcc/config/i386/mingw32.h
@@ -53,6 +53,17 @@ along with GCC; see the file COPYING3.  If not see
     }								\
   while (0)
 
+#define EXTRA_TARGET_D_OS_VERSIONS()				\
+  do								\
+    {								\
+      builtin_version ("MinGW");				\
+      if (TARGET_64BIT && ix86_abi == MS_ABI)			\
+	builtin_version ("Win64");				\
+      else if (!TARGET_64BIT)					\
+	builtin_version ("Win32");				\
+    }								\
+  while (0)
+
 #ifndef TARGET_USE_PTHREAD_BY_DEFAULT
 #define SPEC_PTHREAD1 "pthread"
 #define SPEC_PTHREAD2 "!no-pthread"
diff --git a/gcc/config/t-winnt b/gcc/config/t-winnt
index 9587f66b3db..00bd3c348b4 100644
--- a/gcc/config/t-winnt
+++ b/gcc/config/t-winnt
@@ -20,3 +20,7 @@ winnt-c.o: config/winnt-c.c $(CONFIG_H) $(SYSTEM_H) coretypes.h \
   $(C_TARGET_H) $(C_TARGET_DEF_H)
 	$(COMPILER) -c $(ALL_COMPILERFLAGS) $(ALL_CPPFLAGS) \
 	  $< $(OUTPUT_OPTION)
+
+winnt-d.o: config/winnt-d.c
+	$(COMPILE) $<
+	$(POSTCOMPILE)
diff --git a/gcc/config/winnt-d.c b/gcc/config/winnt-d.c
new file mode 100644
index 00000000000..f3a36c28293
--- /dev/null
+++ b/gcc/config/winnt-d.c
@@ -0,0 +1,43 @@
+/* Windows support needed only by D front-end.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "target.h"
+#include "d/d-target.h"
+#include "d/d-target-def.h"
+#include "tm_p.h"
+
+/* Implement TARGET_D_OS_VERSIONS for Windows targets.  */
+
+static void
+winnt_d_os_builtins (void)
+{
+  d_add_builtin_version ("Windows");
+
+#define builtin_version(TXT) d_add_builtin_version (TXT)
+
+#ifdef EXTRA_TARGET_D_OS_VERSIONS
+  EXTRA_TARGET_D_OS_VERSIONS ();
+#endif
+}
+
+#undef TARGET_D_OS_VERSIONS
+#define TARGET_D_OS_VERSIONS winnt_d_os_builtins
+
+struct gcc_targetdm targetdm = TARGETDM_INITIALIZER;
