gdb: Move DJGPP/go32 bits to their own tdep file

I posit that this makes them easier to find.

The other day while working on the wchar_t patch, I had a bit of
trouble finding the DJGPP/go32 tdep bits.  My initial reaction was
looking for a go32-specific tdep file, but there's none.

Confirmed that a --host=i586-pc-msdosdjgpp GDB still builds
successfully and includes the  i386-go32-tdep.o object.

Confirmed that an --enable-targets=all build of GDB on x86-64
GNU/Linux includes the DJGPP/go32 bits too.

gdb/ChangeLog:
2017-04-12  Pedro Alves  <palves@redhat.com>

	* Makefile.in (ALL_TARGET_OBS): Add i386-go32-tdep.o.
	* configure.tgt: Handle i[34567]86-*-go32* and
	i[34567]86-*-msdosdjgpp*.
	* i386-tdep.c (i386_svr4_reg_to_regnum):
	Make extern.
	(i386_go32_init_abi, i386_coff_osabi_sniffer): Moved to
	i386-go32-tdep.c.
	(_initialize_i386_tdep): DJGPP bits moved to i386-go32-tdep.c.
	* i386-go32-tdep.c: New file.
	* i386-tdep.h (tdesc_i386_mmx, i386_svr4_reg_to_regnum): New
	declarations.

1 files changed, 72 insertions, 0 deletions

diff --git a/gdb/i386-go32-tdep.c b/gdb/i386-go32-tdep.c
new file mode 100644
index 0000000..5bd4857
--- /dev/null
+++ b/gdb/i386-go32-tdep.c
@@ -0,0 +1,72 @@
+/* Target-dependent code for DJGPP/i386.
+
+   Copyright (C) 1988-2017 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program 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 of the License, or
+   (at your option) any later version.
+
+   This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include "defs.h"
+#include "i386-tdep.h"
+#include "target-descriptions.h"
+#include "osabi.h"
+
+static void
+i386_go32_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
+{
+  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
+
+  /* DJGPP doesn't have any special frames for signal handlers.  */
+  tdep->sigtramp_p = NULL;
+
+  tdep->jb_pc_offset = 36;
+
+  /* DJGPP does not support the SSE registers.  */
+  if (!tdesc_has_registers (info.target_desc))
+    tdep->tdesc = tdesc_i386_mmx;
+
+  /* Native compiler is GCC, which uses the SVR4 register numbering
+     even in COFF and STABS.  See the comment in i386_gdbarch_init,
+     before the calls to set_gdbarch_stab_reg_to_regnum and
+     set_gdbarch_sdb_reg_to_regnum.  */
+  set_gdbarch_stab_reg_to_regnum (gdbarch, i386_svr4_reg_to_regnum);
+  set_gdbarch_sdb_reg_to_regnum (gdbarch, i386_svr4_reg_to_regnum);
+
+  set_gdbarch_has_dos_based_file_system (gdbarch, 1);
+
+  set_gdbarch_wchar_bit (gdbarch, 16);
+  set_gdbarch_wchar_signed (gdbarch, 0);
+}
+
+
+static enum gdb_osabi
+i386_coff_osabi_sniffer (bfd *abfd)
+{
+  if (strcmp (bfd_get_target (abfd), "coff-go32-exe") == 0
+      || strcmp (bfd_get_target (abfd), "coff-go32") == 0)
+    return GDB_OSABI_GO32;
+
+  return GDB_OSABI_UNKNOWN;
+}
+
+
+void
+_initialize_i386_go32_tdep ()
+{
+  gdbarch_register_osabi_sniffer (bfd_arch_i386, bfd_target_coff_flavour,
+				  i386_coff_osabi_sniffer);
+
+  gdbarch_register_osabi (bfd_arch_i386, 0, GDB_OSABI_GO32,
+			  i386_go32_init_abi);
+}