On Sep 27, 2012, at 2:04 PM, Uros Bizjak wrote:
>
>
>
>>>>> I agree (subreg:M (op:N A C) 0) to (op:M (subreg:N (A 0)) C) is
>>>>> a good transformation, but why do we need to handle as special
>>>>> the case where the subreg is itself the operand of a plus or minus?
>>>>> I think it should happen regardless of where the subreg occurs.
>>>>
>>>> Don't we need to restrict this to the low part though?
>>>
>>> ...
>
> After some off-line discussion with Richard, attached is v2 of the patch.
>
> 2012-09-27 Uros Bizjak <ubiz...@gmail.com>
>
> PR rtl-optimization/54457
> * simplify-rtx.c (simplify_subreg):
> Simplify (subreg:SI (op:DI ((x:DI) (y:DI)), 0)
> to (op:SI (subreg:SI (x:DI) 0) (subreg:SI (x:DI) 0)).
> ...
Is it just specific to DI -> SI, or is it for any large mode -> smaller mode,
like SI -> HI?
paul
