understanding DAG: node creation

I have an intrinsic and it must be lowered to instruction, which works with fixed register.
So, it takes contents of this register and another argument as input. After execution, the result of the instruction is placed into that same fixed register.

What should I do in SelectionDAGBuilder::visitIntrinicCall to describe such behaviour for a SDNode?

Thank you for the ideas and insights.

I have an intrinsic and it must be lowered to instruction, which works with
fixed register.
So, it takes contents of this register and another argument as input. After
execution, the result of the instruction is placed into that same fixed
register.

What should I do in SelectionDAGBuilder::visitIntrinicCall to describe such
behaviour for a SDNode?

If this is a target specific intrinsic, you should custom lower it in
XXXTargetLowering::LowerOperation(). There are several examples of this
in lib/Target/

-Tom