Re: [PATCH] Removal of uses of MAX_REGISTER_SIZE

[Alan Hayward <Alan.Hayward@arm.com>]

> On 8 Feb 2017, at 17:36, Yao Qi <qiyaoltc@gmail.com> wrote:
> 
> Alan Hayward <Alan.Hayward@arm.com> writes:
> 
>> @@ -1279,7 +1335,7 @@ regcache_dump (struct regcache *regcache, struct ui_file *file,
>>   int footnote_register_offset = 0;
>>   int footnote_register_type_name_null = 0;
>>   long register_offset = 0;
>> -  gdb_byte buf[MAX_REGISTER_SIZE];
>> +  std::vector<gdb_byte> buf (max_register_size (gdbarch));
>> 
>> #if 0
>>   fprintf_unfiltered (file, "nr_raw_registers %d\n",
>> @@ -1406,8 +1462,8 @@ regcache_dump (struct regcache *regcache, struct ui_file *file,
>> 	    fprintf_unfiltered (file, "<unavailable>");
>> 	  else
>> 	    {
>> -	      regcache_raw_read (regcache, regnum, buf);
>> -	      print_hex_chars (file, buf,
>> +	      regcache_raw_update (regcache, regnum);
>> +	      print_hex_chars (file, register_buffer (regcache, regnum),
>> 			       regcache->descr->sizeof_register[regnum],
>> 			       gdbarch_byte_order (gdbarch));
>> 	    }
>> @@ -1422,13 +1478,13 @@ regcache_dump (struct regcache *regcache, struct ui_file *file,
>> 	    {
>> 	      enum register_status status;
>> 
>> -	      status = regcache_cooked_read (regcache, regnum, buf);
>> +	      status = regcache_cooked_read (regcache, regnum, buf.data ());
> 
> Can we use regcache_cooked_read_value so that we don't need buf at all.

Yes, that would work.
However, this cooked read is in the middle of a for() loop of every register value.

With the patch currently, we have the allocation of buf once, and then re-use it for each
iteration.

Switching to regcache_cooked_read_value() would result in a call to allocate_value()
(within the regcache_cooked_read_value code) every iteration, which would then be freed
after printing it.


> 
>> 	      if (status == REG_UNKNOWN)
>> 		fprintf_unfiltered (file, "<invalid>");
>> 	      else if (status == REG_UNAVAILABLE)
>> 		fprintf_unfiltered (file, "<unavailable>");
>> 	      else
>> -		print_hex_chars (file, buf,
>> +		print_hex_chars (file, buf.data (),
>> 				 regcache->descr->sizeof_register[regnum],
>> 				 gdbarch_byte_order (gdbarch));
>> 	    }
> 
> -- 
> Yao (齐尧)