public DalvInsn expandedPrefix(BitSet compatRegs){
  RegisterSpecList regs=registers;
  boolean firstBit=compatRegs.get(0);
  if (hasResult())   compatRegs.set(0);
  regs=regs.subset(compatRegs);
  if (hasResult())   compatRegs.set(0,firstBit);
  if (regs.size() == 0)   return null;
  return new HighRegisterPrefix(position,regs);
}

public DalvInsn expandedPrefix ( BitSet compatRegs ) { RegisterSpecList regs = registers ; boolean firstBit = compatRegs . get ( 0 ) ; if ( hasResult ( ) ) compatRegs . set ( 0 ) ; regs = regs . subset ( compatRegs ) ; if ( hasResult ( ) ) compatRegs . set ( 0 , firstBit ) ; if ( regs . size ( ) == 0 ) return null ; return new HighRegisterPrefix ( position , regs ) ; }
gets the instruction prefix required , if any , to use in an expanded version of this instance . will not generate moves for registers marked compatible to the format by the given bitset .
