Re: [PATCH v2 03/10] Add reg_buffer_common

[Simon Marchi <simark@simark.ca>]

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