Re: [patch rfc] Deprecate EXTRA_STACK_ALIGNMENT_NEEDED, flip default

[Andrew Cagney <ac131313@redhat.com>]

I've checked this in.

Andrew

> Hello,
> 
> This patch does two things:
> 
> - deprecates the architecture variable EXTRA_STACK_ALIGNMENT_NEEDED
> - flips that variables default so that it is initially disabled (architectures adjusted where needed)
> 
> The code in question (from hand_function_call) reads:
> 
>   /* elz: on HPPA no need for this extra alignment, maybe it is needed
>      on other architectures. This is because all the alignment is
>      taken care of in the above code (ifdef REG_STRUCT_HAS_ADDR) and
>      in hppa_push_arguments */
>   if (EXTRA_STACK_ALIGNMENT_NEEDED)
>     {
>       /* MVS 11/22/96: I think at least some of this stack_align code
>          is really broken.  Better to let PUSH_ARGUMENTS adjust the
>          stack in a target-defined manner.  */
>       if (STACK_ALIGN_P () && INNER_THAN (1, 2))
>         {
>           /* If stack grows down, we must leave a hole at the top. */
>           int len = 0;
> 
>           for (i = nargs - 1; i >= 0; i--)
>             len += TYPE_LENGTH (VALUE_ENCLOSING_TYPE (args[i]));
>           if (CALL_DUMMY_STACK_ADJUST_P)
>             len += CALL_DUMMY_STACK_ADJUST;
>           sp -= STACK_ALIGN (len) - len;
>         }
>     }
> 
> Several things to note:
> 
> - The alignment code is only enabled when EXTRA_STACK_ALIGNMENT_NEEDED and STACK_ALIGN_P().  While EXTRA_STACK_ALIGNMENT_NEEDED defaults to 1 (and few architectures clear it), it turns out that very few architectures provide a STACK_ALIGN method and consequently most architectures don't have the above code enabled.  In fact, as best I can tell, the above is only used by the m68k, m68hc11 and SPARC.  (I've attached a text file containing the relevant values).
> 
> -  Unless there is some obscure magic going on (such as the TYPE_LENGTH always being aligned), the above, given an odd sized type, will most likely mis-align the SP and not align it!  Scary!
> 
> Anyway, this patch deprecates the method, and I'll commit it in a day or so.
> 
> Andrew
> 
>