VOIDmode in ZERO_EXTEND crashed

[daniel tian]

2009/10/12 Paolo Bonzini <bonzini@gnu.org>:
>
>>> That exactly is the problem.  You can't have a CONST_INT inside a
>>> ZERO_EXTEND.  That is not valid.
>>> You'll need a separate pattern to recognize the CONST_INT without a
>>> ZERO_EXTEND around it.  Unfortunately, this will not give reload
>>> the freedom it should have.
>>>
>>
>>
>> You mean I should remove the const_int (by predicator) in umulhisi3
>> pattern?
>> I mean if I remove it,  how to deal with the "reg = const_int * reg"
>> in umulhisi3 pattern.
>
> You follow these steps:
>
> 1) rename the existing pattern to something else than umulhisi3, and make it
> only accept register_operands
>
> 2) create another insn that matches (mult (zero_extend (match_operand
> "register_operand") (const_int))
>
> 3) create a define_expand that checks for a CONST_INT and does not wrap it
> (but wraps REGs and SUBREGs and if applicable MEMs).
>
> This is in general how you deal with too-forgiving predicates during
> expansion.
>
> Paolo
>

It sounds good point. I will try it first
I  would like to accepted only register and force all const_int
operand into register first.
Obviously, this may generate low efficiency code compared with your solution.

I still can't get a clear mind with step3. I may need take a while to
think about it.
I am a newcomer. :)

Thanks for your guys advice.
Best wishes.
                                                                    daniel.