Operand pop(Register s){
  Stack<Operand> stack=get(s);
  if (stack == null) {
    throw new OptimizingCompilerException("Failure in translating out of SSA form: trying to pop operand from non-existant stack");
  }
 else {
    return stack.pop();
  }
}

Operand pop ( Register s ) { Stack < Operand > stack = get ( s ) ; if ( stack == null ) { throw new OptimizingCompilerException ( "Failure in translating out of SSA form: trying to pop operand from non-existant stack" ) ; } else { return stack . pop ( ) ; } }
pop the name at the top of the stack for a particular register
