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

[Hui Zhu <teawater at gmail dot com>]

On Thu, Dec 23, 2010 at 10:57, Hui Zhu <teawater@gmail.com> wrote:
> On Wed, Dec 22, 2010 at 23:36, Kevin Buettner <kevinb@redhat.com> wrote:
>> 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.

Checked in.

Joel,  do you think this patch can check in to 7.2.1.

Thanks,
Hui

>>
>> Thanks,
>>
>> Kevin
>>
>
> OK. ? Thanks Kevin.
>
> Best,
> Hui
>
>
> 2010-12-23 ?Kevin Buettner ?<kevinb@redhat.com>
> ? ? ? ? ? ?Hui Zhu ?<teawater@gmail.com>
>
> ? ? ? ?* mips-tedp.c (mips_register_name): Add comments.
>
> ---
> ?mips-tdep.c | ? 11 ++++++++++-
> ?1 file changed, 10 insertions(+), 1 deletion(-)
>
> --- a/mips-tdep.c
> +++ b/mips-tdep.c
> @@ -454,7 +454,16 @@ 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. ?This (upper)
> + ? ? range of user visible register numbers are the pseudo-registers.
> +
> + ? ? This approach was adopted accommodate 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 registers that the user
> + ? ? sees - the pseudo registers - match the users expectations
> + ? ? given the programming model being used. ?*/
> ? int rawnum = regno % gdbarch_num_regs (gdbarch);
> ? if (regno < gdbarch_num_regs (gdbarch))
> ? ? return "";
>