Re: [RFA] sh-tdep.c: Fix little endian problem with doubles

[Corinna Vinschen <vinschen@redhat.com>]

On Fri, Oct 10, 2003 at 05:47:20PM -0400, Elena Zannoni wrote:
> Corinna Vinschen writes:
>  > --- sh-tdep.c.INTERIM	2003-10-04 13:22:01.000000000 +0200
>  > +++ sh-tdep.c	2003-10-07 18:42:13.000000000 +0200
>  > @@ -846,6 +846,17 @@ sh_push_dummy_call_fpu (struct gdbarch *
>  >  	      /* Argument goes in a float argument register.  */
>  >  	      reg_size = register_size (gdbarch, flt_argreg);
>  >  	      regval = extract_unsigned_integer (val, reg_size);
>  > +	      /* A float type taking two registers must be handled
>  > +	         differently in LE mode.  */
>  > +	      if (TARGET_BYTE_ORDER == BFD_ENDIAN_LITTLE
>  > +	          && len == 2 * reg_size)
>  > +	        {
>  > +		  regcache_cooked_write_unsigned (regcache, flt_argreg + 1,
>  > +						  regval);
>  > +		  val += reg_size;
>  > +		  len -= reg_size;
>  > +		  regval = extract_unsigned_integer (val, reg_size);
>  > +		}
> 
> I'd prefer if there is an 'else if' clause just for the
> doubles. I.e. don't use len in the test, but TYPE_LENGTH(type). This is
> too confusing.

Erm... sorry, I don't quite understand.  An `else if' in conjuction
with what `if'?  Actually, the double case is handled normally in
BE mode, it's only slightly different in LE mode in that the registers
are swapped.  The above code just makes the swap so I really don't see
what the problem is.

I see, however, that a TYPE_LENGTH(type) might be more readable than the
`len' and even more correct, since len is modified in the loop.  Yes,
that makes sense.

Back to the `else if'.  Wouldn't it be better just to pump up the comment
to explain what happens?  Instead of

  A float type taking two registers must be handled differently in LE mode.

better something along the lines

  In little endian mode, float types taking two registers (doubles on sh4,
  long doubles on sh2e, sh3e and sh4) must be stored swapped in the argument
  registers.  The below code first writes the first 32 bits in the next but
  one register, increments the val and len values accordingly and then
  proceeds as normal by writing the second 32 bits in the next register.

?

Corinna

-- 
Corinna Vinschen
Cygwin Developer
Red Hat, Inc.