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Re: [rfc, spu] Don't call set_gdbarch_cannot_step_breakpoint in spu_gdbarch_init
- From: Pedro Alves <palves at redhat dot com>
- To: Yao Qi <qiyaoltc at gmail dot com>, gdb-patches at sourceware dot org, Ulrich Weigand <uweigand at de dot ibm dot com>
- Date: Fri, 20 Mar 2015 17:47:55 +0000
- Subject: Re: [rfc, spu] Don't call set_gdbarch_cannot_step_breakpoint in spu_gdbarch_init
- Authentication-results: sourceware.org; auth=none
- References: <1426603922-24107-1-git-send-email-qiyaoltc at gmail dot com>
+Ulrich
Ulrich, any idea why cannot_step_breakpoint was ever needed?
Yao's change makes sense to me.
Thanks,
Pedro Alves
On 03/17/2015 02:52 PM, Yao Qi wrote:
> From: Yao Qi <yao.qi@linaro.org>
>
> Nowadays, in infrun.c:resume, the setting to 'step' variable is like:
>
> if (use_displaced_stepping (gdbarch)
> && tp->control.trap_expected
> && sig == GDB_SIGNAL_0
> && !current_inferior ()->waiting_for_vfork_done)
> {
> }
> /* Do we need to do it the hard way, w/temp breakpoints? */
> else if (step)
> step = maybe_software_singlestep (gdbarch, pc); <-- [1]
>
> ...
>
> if (execution_direction != EXEC_REVERSE
> && step && breakpoint_inserted_here_p (aspace, pc))
> {
> ...
> if (gdbarch_cannot_step_breakpoint (gdbarch)) <-- [2]
> step = 0;
> }
>
> spu doesn't have displaced stepping and uses software single step,
> so 'step' is set to zero in [1], and [2] becomes unreachable as a
> result. So don't have to call set_gdbarch_cannot_step_breakpoint
> in spu_gdbarch_init.
>
> On the other hand, we either have hardware single step or software
> single step, do we still need gdbarch method cannot_step_breakpoint?
> CANNOT_STEP_BREAKPOINT was introduced in 1993 by commit
> cef4c2e7a5f2d3426a8255f74b6c7f4e795fd9a4 for alpha OSF/1 native
> support.
>
> I don't have spu machine to test this patch.
>
> gdb:
>
> 2015-03-17 Yao Qi <yao.qi@linaro.org>
>
> * spu-tdep.c (spu_gdbarch_init): Don't call
> set_gdbarch_cannot_step_breakpoint.
> ---
> gdb/spu-tdep.c | 1 -
> 1 file changed, 1 deletion(-)
>
> diff --git a/gdb/spu-tdep.c b/gdb/spu-tdep.c
> index 36ad312..870cf32 100644
> --- a/gdb/spu-tdep.c
> +++ b/gdb/spu-tdep.c
> @@ -2794,7 +2794,6 @@ spu_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
> set_gdbarch_decr_pc_after_break (gdbarch, 4);
> set_gdbarch_breakpoint_from_pc (gdbarch, spu_breakpoint_from_pc);
> set_gdbarch_memory_remove_breakpoint (gdbarch, spu_memory_remove_breakpoint);
> - set_gdbarch_cannot_step_breakpoint (gdbarch, 1);
> set_gdbarch_software_single_step (gdbarch, spu_software_single_step);
> set_gdbarch_get_longjmp_target (gdbarch, spu_get_longjmp_target);
>
>