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

[Duncan Sands]

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.