Richard Guenther <richard.guent...@gmail.com> writes:
> On Fri, Oct 5, 2012 at 3:18 PM, Richard Sandiford
> <rdsandif...@googlemail.com> wrote:
>> Richard Sandiford <rdsandif...@googlemail.com> writes:
>>>>>> How is CONST_WIDE_INT variable size?
>>>>>
>>>>> It's just the usual trailing variable-length array thing.
>>>>
>>>> Good. Do you get rid of CONST_DOUBLE (for integers) at the same time?
>>>
>>> Yeah. I initially thought it might be OK to keep them and have
>>> CONST_INT, integer CONST_DOUBLEs and CONST_WIDE_INT alongside
>>> each other. (The way the patch is structured means that the
>>> choice of whether to keep integer CONST_DOUBLEs can be changed
>>> very easily.) But Kenny convinced me it was a bad idea.
>>
>> Sorry to follow up on myself, but to clarify: I was talking about
>> converted targets here. (As in, I originally thought even converted
>> targets could continue to use integer CONST_DOUBLEs.)
>>
>> Unconverted targets continue to use CONST_DOUBLE.
>
> Why is it that not all targets are "converted"? What's the difficulty
> with that?
> I really do not like partially transitioning there.
The problem is that CONST_DOUBLE as it exists today has two meanings:
a floating-point meaning and an integer meaning. Ports that handle
CONST_DOUBLEs are aware of this and expect the two things to have
the same rtx code. Whereas in a converted port, the two things
have different rtx codes, and the integers have a different
representation from the current low/high pair.
So to take the first hit in config/alpha/alpha.c,
namely alpha_rtx_costs:
case CONST_DOUBLE:
if (x == CONST0_RTX (mode))
*total = 0;
else if ((outer_code == PLUS && add_operand (x, VOIDmode))
|| (outer_code == AND && and_operand (x, VOIDmode)))
*total = 0;
else if (add_operand (x, VOIDmode) || and_operand (x, VOIDmode))
*total = 2;
else
*total = COSTS_N_INSNS (2);
return true;
What could the patch do to make this work without modification?
The middle two cases are for integers, but the first and last
presumably apply to both integers and floats.
Richard
