Re: Extending RSP with vCont;n and vCont;f

[Yao Qi <yao@codesourcery.com>]

On 10/02/2013 11:08 PM, ILG.Robert wrote:
> void
> _initialize_remote (void)
> {
> @@ -12168,6 +12274,34 @@
>                    &setlist,
>                    &showlist);
>
> +  add_setshow_boolean_cmd ("next-stepping", class_run,
> +                 &use_next_stepping, _("\
> +  Enable or disable next stepping."), _("\
> +  Show whether target-assisted next stepping is enabled."), _("\
> +  If on, and the target supports it, when skipping over a source line, GDB\n\
> +  tells the target to skip the next instruction itself instead of\n\
> +  of issuing multiple single-steps.  This speeds up source level\n\
> +  stepping.  If off, GDB always issues slower stepping mechanisms\n\
> +  instead, even if next stepping is supported by the target.  The default is on."),

Due to lack of description of these two packets, I have to understand
them from the help message of the command.

IIUC, it is similar to range-stepping, vCont;r except that start and 
stop address are not provided to the stub.  That means vCont;n requires 
a smarter stub to know enough line table information to decide where to 
stop.

An alternative to me is to teach your stub understand range stepping.

> +                 set_next_stepping,
> +                 show_next_stepping,
> +                 &setlist,
> +                 &showlist);
> +
> +  add_setshow_boolean_cmd ("finish-stepping", class_run,
> +                 &use_finish_stepping, _("\
> +  Enable or disable finish stepping."), _("\
> +  Show whether target-assisted finish stepping is enabled."), _("\
> +  If on, and the target supports it, when stepping out of a function, GDB\n\
> +  tells the target to step out of the corresponding stack frame itself.\n\
> +  This speeds up source level stepping. If off, GDB issues slower\n\
> +  stepping mechanisms instead, even if finish\n\
> +  stepping is supported by the target.  The default is on."),

GDB inserts a momentary breakpoint, resume the inferior and wait when
command "finish" is executed.  I don't think GDB emits a large number of 
RSP packets in this process.  Do you have an experiment that vCont;f
packet improves performance to some extent?

-- 
Yao (齐尧)