divmod pattern question

[Paul Koning]

Gentlepeople,

I have a two-operand divide instruction that takes a double length dividend in a register pair, and produces the quotient in the first register and remainder in the second.

How do I write a divmod pattern for that?  The quotient is easy enough, I write a match_operand for that register and a matching constraint ("0") for the input dividend.  But what about the remainder?  The remainder appears in a register that isn't explicitly mentioned in the RTL (it's the regnum one higher than the quotient, or if you like, the second subreg of the input (dividend) register.

I can make it a define_expand that adds a move from the remainder register into a new register which is the output operand, and count on the optimizer to optimize away that move.  Is that the best answer?  The current "mod" pattern does that, and I could keep that approach.

	paul