if (!isValid()) { throw new DataflowAnalysisException("Accessing invalid frame at " + ins); }
	public int getInstanceSlot(Instruction ins, ConstantPoolGen cpg) throws DataflowAnalysisException {		int numConsumed = ins.consumeStack(cpg);		if (numConsumed == Constants.UNPREDICTABLE)			throw new DataflowAnalysisException("Unpredictable stack consumption in " + ins);		if (numConsumed > getStackDepth())			throw new DataflowAnalysisException("Stack underflow " + ins);		return getNumSlots() - numConsumed;	}