Re: [PATCH v2 03/10] Add reg_buffer_common

Simon Marchi
2018-06-10T22:21:40Z

On 2018-06-08 10:14 AM, Alan Hayward wrote:
>
>> On 7 Jun 2018, at 21:18, Simon Marchi <simon.marchi@ericsson.com> wrote:
>>
>> Hi Alan,
>>
>> Just some quick comments.
>>
>
> <snip - moved to 02 thread>
>
>>> ---
>>> gdb/common/common-regcache.h | 8 ++++++++
>>> gdb/gdbserver/regcache.c | 47 ++++++++++++++++++++++++++++++++------------
>>> gdb/gdbserver/regcache.h | 18 +++++++++++------
>>> gdb/regcache.h | 19 ++++++++++++++----
>>> 4 files changed, 69 insertions(+), 23 deletions(-)
>>>
>>> diff --git a/gdb/common/common-regcache.h b/gdb/common/common-regcache.h
>>> index 696ba00955..487da0a7fb 100644
>>> --- a/gdb/common/common-regcache.h
>>> +++ b/gdb/common/common-regcache.h
>>> @@ -62,4 +62,12 @@ extern enum register_status regcache_raw_read_unsigned
>>>
>>> ULONGEST regcache_raw_get_unsigned (struct regcache *regcache, int regnum);
>>>
>>> +struct reg_buffer_common
>>> +{
>>> + virtual ~reg_buffer_common () = default;
>>> + virtual void raw_supply (int regnum, const void *buf) = 0;
>>> + virtual void raw_collect (int regnum, void *buf) const = 0;
>>> + virtual register_status get_register_status (int regnum) const = 0;
>>> +};
>>
>> Ideally, we would gather the documentation for these methods here. Where they
>> are implemented/overriden, we can maybe add a reference such as
>>
>> /* See struct reg_buffer_common. */
>>
>> ?
>
> Agreed. Updated all the comments for all the moved functions.
>
> I noticed the comment for transfer_regset had become detached from the function,
> so I move it back to the right place.
>
>>
>>> diff --git a/gdb/regcache.h b/gdb/regcache.h
>>> index 3edddf47e1..b559a10752 100644
>>> --- a/gdb/regcache.h
>>> +++ b/gdb/regcache.h
>>> @@ -139,7 +139,7 @@ typedef struct cached_reg
>>>
>>> /* Buffer of registers. */
>>>
>>> -class reg_buffer
>>> +class reg_buffer : public reg_buffer_common
>>> {
>>> public:
>>> reg_buffer (gdbarch *gdbarch, bool has_pseudo);
>>> @@ -151,13 +151,24 @@ public:
>>>
>>> /* Get the availability status of the value of register REGNUM in this
>>> buffer. */
>>> - enum register_status get_register_status (int regnum) const;
>>> + enum register_status get_register_status (int regnum) const override;
>>>
>>> virtual ~reg_buffer ()
>>> {
>>> xfree (m_registers);
>>> xfree (m_register_status);
>>> }
>>> +
>>> + virtual void raw_supply (int regnum, const void *buf) override
>>> + {
>>> + gdb_assert (false);
>>> + }
>>> +
>>> + virtual void raw_collect (int regnum, void *buf) const override
>>> + {
>>> + gdb_assert (false);
>>> + }
>>
>> Hmm, I understand why you need to do this right now. But what do you think of the
>> idea of moving the supply and collect implementations up to reg_buffer? I think
>> that the supply/collect operations are a good fit to go in reg_buffer. Essentially
>> they just peek/poke in the buffer. The regcache layer's responsibility is then to
>> use that register buffer to implement a cache in front of the target registers,
>> and offer the API to properly read/write registers (including pseudo ones).
>>
>> For reference here's the patch in the regcache-for-alan branch that did this:
>> https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=commitdiff;h=0e04bb35765d2717818dddd88328cb975f417b2c;hp=ca9f66e37913be55abaea44813a768b40673a39a
>>
>
> I’m happy with that. I hadn’t that there was no methods for copying in and out
> of reg_buffer. Your change improves that.
>
> Ok, so updated with changes as above. Are you ok with this version?

Yes, that LGTM, thanks.

Simon