[committed] avr: fix clash between returned structure and return address

[Tristan Gingold <gingold at adacore dot com>]

Hi,

this patch fixes two issues related to inferior call than return  
structures whose address is passed by the
first parameter.
* an endianness issue: bytes were swapped.
* because the stack is post decremented, one byte must be reserved to  
avoid an overlap between the
returned structure and the return address (or the last parameter  
passed on the stack).

Tristan.

2009-11-13  Tristan Gingold  <gingold@adacore.com>

	* avr-tdep.c (avr_push_dummy_call): Fix endianness issue and avoid
	overlap between returned structure and return address/parameters.

*** avr-tdep.c	10 Nov 2009 11:14:38 -0000	1.122
--- avr-tdep.c	13 Nov 2009 10:28:30 -0000
***************
*** 1252,1261 ****

    if (struct_return)
      {
!       regcache_cooked_write_unsigned (regcache, regnum--,
!                                       struct_addr & 0xff);
!       regcache_cooked_write_unsigned (regcache, regnum--,
!                                       (struct_addr >> 8) & 0xff);
      }

    for (i = 0; i < nargs; i++)
--- 1252,1265 ----

    if (struct_return)
      {
!       regcache_cooked_write_unsigned
!         (regcache, regnum--, (struct_addr >> 8) & 0xff);
!       regcache_cooked_write_unsigned
!         (regcache, regnum--, struct_addr & 0xff);
!       /* SP being post decremented, we need to reserve one byte so  
that the
!          return address won't overwrite the result (or vice-versa).   
*/
!       if (sp == struct_addr)
!         sp--;
      }

    for (i = 0; i < nargs; i++)