[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]

Chatted w/Duncan on IRC. I will follow the UADDO logic here (preparing patch).

Michael

On May 25, 2013, at 5:54 AM, Duncan Sands <duncan.sands at gmail.com> wrote:

> Hi Michael,
> 
>> Would zero extending just ResNo 0 be a satisfactory lowering (i.e. no inputs,
>> just ResNo 0)?
> 
> do you mean not changing the node, just creating a node to extend ResNo 0?  If
> so, that won't work: the legalizer will go into an infinite loop as it will keep
> on trying to legalize the original node.
> 
> Ciao, Duncan.
> 

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