[PATCH] RISC-V: enable have_nonsteppable_watchpoint by default

[Craig Blackmore <craig.blackmore@embecosm.com>]

The RISC-V debug spec 0.13 recommends that write triggers fire before
the write is committed. If the target follows this behaviour, then
have_nonsteppable_watchpoint needs to be set to 1 so that GDB will step
over the watchpoint before checking if the value has changed.
    
This patch adds a setshow for have_nonsteppable_watchpoint which defaults
to 1 to match the recommended behaviour. If a target does not follow
this timing, then 'set riscv have_nonsteppable_watchpoint 0' will need
to be issued on the command line.
    
gdb/ChangeLog:
    
	* riscv-tdep.c (set_have_nonsteppable_watchpoint): add
	callback for 'set riscv have_nonsteppable_watchpoint'
	(riscv_gdbarch_init): initialise gdbarch setting for
	have_nonesteppable_watchpoint

---

diff --git a/gdb/riscv-tdep.c b/gdb/riscv-tdep.c
index 254914c9c7..8f301d8b01 100644
--- a/gdb/riscv-tdep.c
+++ b/gdb/riscv-tdep.c
@@ -226,6 +226,20 @@ show_use_compressed_breakpoints (struct ui_file *file, int from_tty,
 		      "to %s%s.\n"), value, additional_info);
 }
 
+static int riscv_have_nonsteppable_watchpoint = 1;
+
+/* The set callback for 'set riscv have-nonsteppable-watchpoint'. */
+
+static void
+set_have_nonsteppable_watchpoint (const char *args, int from_tty,
+			       struct cmd_list_element *c)
+{
+  struct gdbarch *gdbarch = target_gdbarch ();
+
+  set_gdbarch_have_nonsteppable_watchpoint (gdbarch,
+					    riscv_have_nonsteppable_watchpoint);
+}
+
 /* The set and show lists for 'set riscv' and 'show riscv' prefixes.  */
 
 static struct cmd_list_element *setriscvcmdlist = NULL;
@@ -2736,6 +2750,8 @@ riscv_gdbarch_init (struct gdbarch_info info,
   set_gdbarch_return_value (gdbarch, riscv_return_value);
   set_gdbarch_breakpoint_kind_from_pc (gdbarch, riscv_breakpoint_kind_from_pc);
   set_gdbarch_sw_breakpoint_from_kind (gdbarch, riscv_sw_breakpoint_from_kind);
+  set_gdbarch_have_nonsteppable_watchpoint (gdbarch,
+					    riscv_have_nonsteppable_watchpoint);
 
   /* Register architecture.  */
   set_gdbarch_num_regs (gdbarch, RISCV_LAST_REGNUM + 1);
@@ -2980,4 +2996,20 @@ can be used."),
 				show_use_compressed_breakpoints,
 				&setriscvcmdlist,
 				&showriscvcmdlist);
+
+  add_setshow_boolean_cmd ("have-nonsteppable-watchpoint", no_class,
+			   &riscv_have_nonsteppable_watchpoint,
+			   _("\
+Set whether debugger must step over hardware watchpoints"),
+			   _("\
+Show whether debugger must step over hardware watchpoints"),
+			   _("\
+The RISC-V debug spec recommends that hardware write watchpoints fire before\n\
+the write is committed, in which case, GDB must step over the watchpoint\n\
+before checking the old and new values. Set this option to 1 (default) for\n\
+targets that follow this behaviour, otherwise set to 0."),
+			   set_have_nonsteppable_watchpoint,
+			   NULL,
+			   &setriscvcmdlist,
+			   &showriscvcmdlist);
 }