How to write pattern for addition with carry operation

[Uros Bizjak]

Hello!

> The 16bit target that i am porting to gcc4.1.2 doesn't have any
> instructions for 32bit operations. But for addition and subtraction
> there is
> addc
> subc
> instructions that consider carry bit also. Presently i have patterns
> for SImode addition and subtraction such that the template will have
>
> add %0, %1\naddc %N0, %N1
> sub %0, %1\nsubc %N0, %N1
>
> Will it be possible for me to write separate patterns for the
> instructions add and addc?
>   

You can look into config/i386.md, how i.e. adddi3 is expanded and split 
in case of !TARGET_64BIT.

Uros.