[2/4] Use the target architecture when encoding tracepoint actions

  This patch uses the target architecture rather then the objfile
architecture when encoding tracepoint actions.

The target architecture may contain additional registers. E.g. ARM VFP
registers. This information is needed to allow their collection. Since we
can never know whether the registers numbers in the target match the
binary's we have to use tdesc here.

One note about combined debuggers / multi-inferior from Pedro Alves:

In the combined debugger case taking Cell as the practical example that
gdb supports currently:

In that case, the main target_gdbarch() will be powerpc, but you may have set a
tracepoint on _spu_ code, which has a different gdbarch.  so for that case,
target_gdbarch would be wrong.  I think that in that case, we'd need to
find __the_ target/tdesc gdbarch that is (bfd) compatible with the
objfile's gdbarch.

I think cell/spu gdbserver doesn't support tracepoints, so we can ignore
this for now.

The multi-inferior/process case is somewhat related, but its simpler.
each inferior has its own gdbarch.

That is, target_gdbarch depends on the current inferior selected.
In fact, that just returns inferior->gdbarch nowaways.

No regressions, tested on ubuntu 14.04 ARMv7 and x86.
With gdbserver-{native,extended} / { -marm -mthumb }

gdb/ChangeLog:

	* tracepoint.c (encode_actions_1): Use target_gdbarch () rather
	than loc->gdbarch.
---
 gdb/tracepoint.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)
  

On 07/01/16 18:44, Antoine Tremblay wrote:
> This patch uses the target architecture rather then the objfile
> architecture when encoding tracepoint actions.
>
> The target architecture may contain additional registers. E.g. ARM VFP
> registers. This information is needed to allow their collection. Since we
> can never know whether the registers numbers in the target match the
> binary's we have to use tdesc here.
>
> One note about combined debuggers / multi-inferior from Pedro Alves:
>
> In the combined debugger case taking Cell as the practical example that
> gdb supports currently:
>
> In that case, the main target_gdbarch() will be powerpc, but you may have set a
> tracepoint on _spu_ code, which has a different gdbarch.  so for that case,
> target_gdbarch would be wrong.  I think that in that case, we'd need to
> find __the_ target/tdesc gdbarch that is (bfd) compatible with the
> objfile's gdbarch.
>
> I think cell/spu gdbserver doesn't support tracepoints, so we can ignore
> this for now.
>
> The multi-inferior/process case is somewhat related, but its simpler.
> each inferior has its own gdbarch.
>
> That is, target_gdbarch depends on the current inferior selected.
> In fact, that just returns inferior->gdbarch nowaways.
>
> No regressions, tested on ubuntu 14.04 ARMv7 and x86.
> With gdbserver-{native,extended} / { -marm -mthumb }
>
> gdb/ChangeLog:
>
> 	* tracepoint.c (encode_actions_1): Use target_gdbarch () rather
> 	than loc->gdbarch.
 > [...]

Hey, could we get that one pushed soon?  I've made a patchset that adds 
tdesc information to tfile format, making it work properly for 
multiple-tdesc architectures 
(https://sourceware.org/ml/gdb-patches/2016-02/msg00161.html), and made 
x86_64 work with collecting AVX registers 
(https://sourceware.org/ml/gdb-patches/2016-02/msg00167.html), so that 
patch could do a lot of good already.

Marcin Kościelnicki
  

On 01/07/2016 05:44 PM, Antoine Tremblay wrote:

> gdb/ChangeLog:
> 
> 	* tracepoint.c (encode_actions_1): Use target_gdbarch () rather
> 	than loc->gdbarch.

OK, please push.

Thanks,
Pedro Alves
  

Pedro Alves writes:

> On 01/07/2016 05:44 PM, Antoine Tremblay wrote:
>
>> gdb/ChangeLog:
>> 
>> 	* tracepoint.c (encode_actions_1): Use target_gdbarch () rather
>> 	than loc->gdbarch.
>
> OK, please push.
>
> Thanks,
> Pedro Alves

Pushed in.

Thanks,
Antoine