Re: [RFA] mn10300-tdep.c: Always write return address to MDR register on push_dummy_call

[Michael Snyder <msnyder at redhat dot com>]

Corinna Vinschen wrote:
> Hi,
>
> the mn10300 hardware always writes the return address to the stack and
> into the MDR register when any "call" machine instruction is executed.
> The mn10300_push_dummy_call function does only write the return address
> to the stack, which might result into problems when leaf functions are
> called and the MDR register is known not to be clobbered by "mul" or
> "div" instructions.  The below patch also writes the return address
> always into the MDR register, like the hardware.
>
> Ok to apply?

Ha, yes, nice catch.   ;-)


> 	* mn10300-tdep.c (mn10300_push_dummy_call): Write breakpoint
> 	address to MDR register.
>
>
> Index: mn10300-tdep.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/mn10300-tdep.c,v
> retrieving revision 1.136
> diff -u -p -r1.136 mn10300-tdep.c
> --- mn10300-tdep.c	28 Feb 2006 22:28:21 -0000	1.136
> +++ mn10300-tdep.c	1 Mar 2006 17:23:05 -0000
> @@ -1055,6 +1055,11 @@ mn10300_push_dummy_call (struct gdbarch 
>    /* Push the return address that contains the magic breakpoint.  */
>    sp -= 4;
>    write_memory_unsigned_integer (sp, push_size, bp_addr);
> +
> +  /* The CPU also writes the return address always into the
> +     MDR register on "call".  */
> +  regcache_cooked_write_unsigned (regcache, E_MDR_REGNUM, bp_addr);
> +
>    /* Update $sp.  */
>    regcache_cooked_write_unsigned (regcache, E_SP_REGNUM, sp);
>    return sp;