d: Add openbsd support for D compiler [PR99691]

gcc/ChangeLog:

	PR d/99691
	* config.gcc (*-*-openbsd*): Add openbsd-d.o.
	* config/t-openbsd: Add openbsd-d.o.
	* config/openbsd-d.c: New file.

gcc/config.gcc

@@ -917,6 +917,8 @@ case ${target} in
       default_use_cxa_atexit=yes
       ;;
   esac
+  d_target_objs="${d_target_objs} openbsd-d.o"
+  target_has_targetdm=yes
   ;;
 *-*-phoenix*)
   gas=yes

gcc/config/openbsd-d.c

@@ -0,0 +1,39 @@
+/* Functions for generic OpenBSD as target machine for GNU D compiler.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+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 "memmodel.h"
+#include "tm.h"
+#include "tm_p.h"
+#include "d/d-target.h"
+#include "d/d-target-def.h"
+
+static void
+openbsd_d_os_builtins (void)
+{
+  d_add_builtin_version ("Posix");
+  d_add_builtin_version ("OpenBSD");
+}
+
+#undef TARGET_D_OS_VERSIONS
+#define TARGET_D_OS_VERSIONS openbsd_d_os_builtins
+
+struct gcc_targetdm targetdm = TARGETDM_INITIALIZER;

gcc/config/t-openbsd

@@ -1,2 +1,7 @@
 # We don't need GCC's own include files.
 USER_H = $(EXTRA_HEADERS)
+
+# OpenBSD-specific D support.
+openbsd-d.o: $(srcdir)/config/openbsd-d.c
+	$(COMPILE) $<
+	$(POSTCOMPILE)