[PATCH] [Multiprecision Arithmetic Optimization] Teach SelectionDAG how to promote the integer carry result of {add, sub}{c, e} to a larger integer type.

[Michael Gottesman]

Ping?

On May 18, 2013, at 5:30 PM, Michael Gottesman <mgottesman at apple.com> wrote:

> (Sorry there is a typo therein. When I say lowering is done for all 4 types for ResNo == 1 I meant for ResNo == 0 and ResNo == 1).
> 
> Michael
> 
> On May 18, 2013, at 5:26 PM, Michael Gottesman <mgottesman at apple.com> wrote:
> 
>> 
>> On May 18, 2013, at 2:22 AM, Duncan Sands <duncan.sands at gmail.com> wrote:
>> 
>>> Hi Michael,
>>> 
>>> On 17/05/13 23:33, Michael Gottesman wrote:
>>>> Hows this look Duncan/Sean?
>>> 
>>> returning SDValue() in PromoteIntRes_ADDSUBC is not valid.  There is no default
>>> method that can be fallen back to.  If you don't want to handle the ResNo != 1
>>> case then you must assert/fail, not just return SDValue().
>>> 
>>> Ciao, Duncan.
>> 
>> Hey Duncan,
>> 
>> In the updated patch are the changes that you requested (i.e. I am not just returning SDValue() in said patch). The lowering is done for all 4 types for ResNo == 1. I should have said something in the email enclosing the updated patch. My apologies for not being clearer.
>> 
>> Michael
>> 
>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>>>> Michael
>>>> 
>>>> On May 16, 2013, at 10:41 AM, Michael Gottesman <mgottesman at apple.com
>>>> <mailto:mgottesman at apple.com>> wrote:
>>>> 
>>>>> I am trying to be incremental and did not have a need for such lowering. On
>>>>> the other hand if you want I can implement that in this patch. Just state your
>>>>> preference = ).
>>>>> 
>>>>> Michael
>>>>> 
>>>>> On May 16, 2013, at 1:34 AM, Duncan Sands <duncan.sands at gmail.com
>>>>> <mailto:duncan.sands at gmail.com>> wrote:
>>>>> 
>>>>>> Hi Michael,
>>>>>> 
>>>>>> On 15/05/13 19:37, Michael Gottesman wrote:
>>>>>>> The attached patch teaches selection DAG how to promote the integer carry
>>>>>>> result of an {add,sub}{c,e} node to a larger integer type. It is a part of a
>>>>>>> larger set of patches that I will be committing over the next little bit to
>>>>>>> enable the optimization of uaddo/usubo chains.
>>>>>>> 
>>>>>>> Please Review,
>>>>>>> Michael
>>>>>> 
>>>>>> +SDValue DAGTypeLegalizer::PromoteIntRes_ADDSUBC(SDNode *N, unsigned ResNo) {
>>>>>> +  if (ResNo == 1)
>>>>>> +    return PromoteIntRes_Overflow(N);
>>>>>> +  return SDValue();
>>>>>> +}
>>>>>> +
>>>>>> +SDValue DAGTypeLegalizer::PromoteIntRes_ADDSUBE(SDNode *N, unsigned ResNo) {
>>>>>> +  if (ResNo == 1)
>>>>>> +    return PromoteIntRes_Overflow(N);
>>>>>> +  return SDValue();
>>>>>> +}
>>>>>> 
>>>>>> why do you return SDValue() if ResNo != 1 ?  Shouldn't you either assert or
>>>>>> promote the value?
>>>>>> 
>>>>>> Ciao, Duncan.
>>>>>> 
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