conditional assignment in selectionDAG


I am trying following transformation in X86 selection dag.

lhs = rhs; // lhs and rhs are f32


if(rhs == 0.0)
   lhs = rhs;
  lhs = rhs';

i.e. conditionally replace rhs by rhs'.

I guess it can be done using ISD::SELECT node(for float values)? In that case I have to create a condition node. Can you please suggest/refer to how to do so?

You may please suggest alternatives. Note that I want to perform this transformation on the selection dag during target lowering and hence prefer not to create any basicblock+instruction.

Thanks in advance.

Best Regards,

"The search for truth is more precious than its possession."