+joinToTargets_first :: (FR freeRegs, Instruction instr)
+ => BlockMap RegSet
+ -> [NatBasicBlock instr]
+ -> BlockId
+ -> instr
+ -> BlockId
+ -> [BlockId]
+ -> BlockAssignment freeRegs
+ -> RegMap Loc
+ -> [RealReg]
+ -> RegM freeRegs ([NatBasicBlock instr], instr)