Re: [PATCH] Remove MAX_REGISTER_SIZE from regcache.c

[Yao Qi <qiyaoltc@gmail.com>]

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.

-- 
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);
 }