Re: [PATCH] Remove MAX_REGISTER_SIZE from regcache.c

[Alan Hayward <Alan dot Hayward at arm dot com>]

> On 10 Apr 2017, at 09:59, Yao Qi <qiyaoltc@gmail.com> wrote:
> 
> Alan Hayward <Alan.Hayward@arm.com> writes:
> 
>>>> @@ -395,9 +404,9 @@ regcache_restore (struct regcache *dst,
>>>> 	{
>>>> 	  enum register_status status;
>>> 
>>> Can we move "buf" here? and initialize it with the register_size,
>>> 
>>>          std::vector<gdb_byte> buf (register_size (gdbarch, regnum));
>>> 
>>> then, we don't need max_register_size ().
>>> 
>> 
>> Problem with this is that we are then creating a brand new buffer for each
>> iteration of the loop, which is a little heavyweight.
>> We could create an empty buf outside the loop and re-size it each iteration,
>> but that's still going to cost.
>> 
> 
> How is this patch below?  I class-fied regcache last month in my local
> tree, and MAX_REGISTER_SIZE is disappeared from regcache.c.  I suggested
> using std::vector in a loop so that it is easy to rebase my patches.
> 

I’m happy with this. It also simplifies the code logic a little, which is good.

This would then reduce my patch to recache_save and regcache_dump changes.

Alan.


> -- 
> Yao (齐尧)
> From 25d562b5f858314ad9d41a7ffa825d8d24e3828e Mon Sep 17 00:00:00 2001
> From: Yao Qi <yao.qi@linaro.org>
> Date: Fri, 7 Apr 2017 22:50:27 +0100
> Subject: [PATCH] Simplify regcache_restore
> 
> This patches removes the 2nd argument of regcache_restore, because it
> is only called by regcache_cpy.  In regcache_cpy, if regcache_restore
> is called, dst is not readonly, but src is readonly.  So this patch
> adds an assert that src is readonly in regcache_restore.
> regcache_cook_read read everything from a readonly regcache cache
> (src)'s register_buffer, and register status is from src->register_status.
> 
> gdb:
> 
> 2017-04-07  Yao Qi  <yao.qi@linaro.org>
> 
> 	* regcache.c (regcache_restore): Remove argument 2.  Replace
> 	argument 3 with regcache.  Get register status from
> 	src->register_status and get register contents from
> 	register_buffer (src, regnum).
> 	(regcache_cpy): Update.
> 
> diff --git a/gdb/regcache.c b/gdb/regcache.c
> index 37bc2f0..41c23a5 100644
> --- a/gdb/regcache.c
> +++ b/gdb/regcache.c
> @@ -374,17 +374,15 @@ regcache_save (struct regcache *dst, regcache_cooked_read_ftype *cooked_read,
> }
> 
> static void
> -regcache_restore (struct regcache *dst,
> -		  regcache_cooked_read_ftype *cooked_read,
> -		  void *cooked_read_context)
> +regcache_restore (struct regcache *dst, struct regcache *src)
> {
>   struct gdbarch *gdbarch = dst->descr->gdbarch;
> -  gdb_byte buf[MAX_REGISTER_SIZE];
>   int regnum;
> 
>   /* The dst had better not be read-only.  If it is, the `restore'
>      doesn't make much sense.  */
>   gdb_assert (!dst->readonly_p);
> +  gdb_assert (src->readonly_p);
>   /* Copy over any registers, being careful to only restore those that
>      were both saved and need to be restored.  The full [0 .. gdbarch_num_regs
>      + gdbarch_num_pseudo_regs) range is checked since some architectures need
> @@ -393,11 +391,8 @@ regcache_restore (struct regcache *dst,
>     {
>       if (gdbarch_register_reggroup_p (gdbarch, regnum, restore_reggroup))
> 	{
> -	  enum register_status status;
> -
> -	  status = cooked_read (cooked_read_context, regnum, buf);
> -	  if (status == REG_VALID)
> -	    regcache_cooked_write (dst, regnum, buf);
> +	  if (src->register_status[regnum] == REG_VALID)
> +	    regcache_cooked_write (dst, regnum, register_buffer (src, regnum));
> 	}
>     }
> }
> @@ -424,7 +419,7 @@ regcache_cpy (struct regcache *dst, struct regcache *src)
>   if (!src->readonly_p)
>     regcache_save (dst, do_cooked_read, src);
>   else if (!dst->readonly_p)
> -    regcache_restore (dst, do_cooked_read, src);
> +    regcache_restore (dst, src);
>   else
>     regcache_cpy_no_passthrough (dst, src);
> }