// TODO: keep a single varnum map, then make all of these maps slices instead?
	vars map[ir.Node]*ssa.Value

	// fwdVars are variables that are used before they are defined in the current block.
	// This map exists just to coalesce multiple references into a single FwdRef op.
	// *Node is the unique identifier (an ONAME Node) for the variable.
	fwdVars map[ir.Node]*ssa.Value