Re: [RFA/RFC] mips tracepoint: fix Bug 12013

[Kevin Buettner <kevinb at redhat dot com>]

On Wed, 22 Dec 2010 15:12:22 +0800
Hui Zhu <teawater@gmail.com> wrote:

> > You might consider implementing a new gdbarch method which provides a
> > mapping from pseudo register numbers to raw register numbers. __The
> > trace machinery could use such a mapping to find the corresponding raw
> > register(s) when presented with a pseudo register. __I can think of
> > several potential pitfalls with this approach, but I think the idea is
> > worth exploring.
>
> Thanks Kevin.  I will do it.

Please look at Pedro's reply.  He has outlined a better approach.

> And I make a patch to add some comments from your mail to mips_register_name.
> Wish it can help other people.
> 
> Please help me review it.

Okay, see below...

> 2010-12-22  Hui Zhu  <teawater@gmail.com>
> 
> 	* mips-tedp.c (mips_register_name): Add comments.
> 
> ---
>  mips-tdep.c |    7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> --- a/mips-tdep.c
> +++ b/mips-tdep.c
> @@ -454,7 +454,12 @@ mips_register_name (struct gdbarch *gdba
>    enum mips_abi abi = mips_abi (gdbarch);
> 
>    /* Map [gdbarch_num_regs .. 2*gdbarch_num_regs) onto the raw registers,
> -     but then don't make the raw register names visible.  */
> +     but then don't make the raw register names visible.
> +     Because It is possible to debug a 64-bit device using a 32-bit programming
> +     model.  In such instances, the raw registers are configured to be
> +     64-bits wide, while the pseudo registers are configured to be 32-bits
> +     wide.  The registers that the user sees - the pseudo registers - match
> +     the user's expectations given the programming model being used.  */

Could you revise the comment to read as follows?

    /* Map [gdbarch_num_regs .. 2*gdbarch_num_regs) onto the raw registers,
       but do not make the raw register names visible.  This (upper)
       range of user visible register numbers are the
       pseudo-registers.
       
       This approach was adopted accomodate the following scenario: 
       It is possible to debug a 64-bit device using a 32-bit
       programming model.  In such instances, the raw registers are
       configured to be 64-bits wide, while the pseudo registers are
       configured to be 32-bits wide.  The reigsters that the user
       sees - the pseudo registers - match the users expectations
       given the programming model being used.  */

Please allow several days for others to tweak my suggested wording.  If
there are no further comments on the above wording, feel free to commit
it.

Thanks,

Kevin