org.ow2.asm/asm-analysis/7.1 : org/objectweb/asm/tree/analysis/Frame.java

Frame
http://asm.ow2.org/: Static code analysis API of ASM, a very small and fast Java bytecode manipulation framework (OW2)
Eric Bruneton
Eugene Kuleshov
Remi Forax
// ASM: a very small and fast Java bytecode manipulation framework
// Copyright (c) 2000-2011 INRIA, France Telecom
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
// 1. Redistributions of source code must retain the above copyright
//    notice, this list of conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in the
//    documentation and/or other materials provided with the distribution.
// 3. Neither the name of the copyright holders nor the names of its
//    contributors may be used to endorse or promote products derived from
//    this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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package org.objectweb.asm.tree.analysis;

import java.util.ArrayList;
import java.util.List;
import org.objectweb.asm.Opcodes;
import org.objectweb.asm.Type;
import org.objectweb.asm.tree.AbstractInsnNode;
import org.objectweb.asm.tree.IincInsnNode;
import org.objectweb.asm.tree.InvokeDynamicInsnNode;
import org.objectweb.asm.tree.LabelNode;
import org.objectweb.asm.tree.MethodInsnNode;
import org.objectweb.asm.tree.MultiANewArrayInsnNode;
import org.objectweb.asm.tree.VarInsnNode;

A symbolic execution stack frame. A stack frame contains a set of local variable slots, and an
operand stack. Warning: long and double values are represented with two slots in local
variables, and with one slot in the operand stack.
Author: Eric Bruneton
Type parameters: <V> – type of the Value used for the analysis./**
 * A symbolic execution stack frame. A stack frame contains a set of local variable slots, and an
 * operand stack. Warning: long and double values are represented with <i>two</i> slots in local
 * variables, and with <i>one</i> slot in the operand stack.
 *
 * @param <V> type of the Value used for the analysis.
 * @author Eric Bruneton
 */
public class Frame<V extends Value> {

  The expected return type of the analyzed method, or null if the method returns void. /**
   * The expected return type of the analyzed method, or {@literal null} if the method returns void.
   */
  private V returnValue;

  The local variables and the operand stack of this frame. The first Frame<V>.numLocals elements correspond to the local variables. The following Frame<V>.numStack elements correspond to the operand stack. /**
   * The local variables and the operand stack of this frame. The first {@link #numLocals} elements
   * correspond to the local variables. The following {@link #numStack} elements correspond to the
   * operand stack.
   */
  private V[] values;

  The number of local variables of this frame. /** The number of local variables of this frame. */
  private int numLocals;

  The number of elements in the operand stack. /** The number of elements in the operand stack. */
  private int numStack;

  Constructs a new frame with the given size.
Params: numLocals – the maximum number of local variables of the frame.
numStack – the maximum stack size of the frame./**
   * Constructs a new frame with the given size.
   *
   * @param numLocals the maximum number of local variables of the frame.
   * @param numStack the maximum stack size of the frame.
   */
  @SuppressWarnings("unchecked")
  public Frame(final int numLocals, final int numStack) {
    this.values = (V[]) new Value[numLocals + numStack];
    this.numLocals = numLocals;
  }

  Constructs a copy of the given Frame.
Params: frame – a frame./**
   * Constructs a copy of the given Frame.
   *
   * @param frame a frame.
   */
  public Frame(final Frame<? extends V> frame) {
    this(frame.numLocals, frame.values.length - frame.numLocals);
    init(frame); // NOPMD(ConstructorCallsOverridableMethod): can't fix for backward compatibility.
  }

  Copies the state of the given frame into this frame.
Params: frame – a frame.
Returns: this frame./**
   * Copies the state of the given frame into this frame.
   *
   * @param frame a frame.
   * @return this frame.
   */
  public Frame<V> init(final Frame<? extends V> frame) {
    returnValue = frame.returnValue;
    System.arraycopy(frame.values, 0, values, 0, values.length);
    numStack = frame.numStack;
    return this;
  }

  Initializes a frame corresponding to the target or to the successor of a jump instruction. This method is called by Analyzer.analyze(String, MethodNode) while interpreting jump instructions. It is called once for each possible target of the jump instruction, and once for its successor instruction (except for GOTO and JSR), before the frame is merged with the existing frame at this location. The default implementation of this method does nothing. Overriding this method and changing the frame values allows implementing branch-sensitive
analyses.
Params: opcode – the opcode of the jump instruction. Can be IFEQ, IFNE, IFLT, IFGE, IFGT, IFLE,
    IF_ICMPEQ, IF_ICMPNE, IF_ICMPLT, IF_ICMPGE, IF_ICMPGT, IF_ICMPLE, IF_ACMPEQ, IF_ACMPNE,
    GOTO, JSR, IFNULL, IFNONNULL, TABLESWITCH or LOOKUPSWITCH.
target – a target of the jump instruction this frame corresponds to, or null if this frame corresponds to the successor of the jump instruction (i.e. the next instruction in the instructions sequence)./**
   * Initializes a frame corresponding to the target or to the successor of a jump instruction. This
   * method is called by {@link Analyzer#analyze(String, org.objectweb.asm.tree.MethodNode)} while
   * interpreting jump instructions. It is called once for each possible target of the jump
   * instruction, and once for its successor instruction (except for GOTO and JSR), before the frame
   * is merged with the existing frame at this location. The default implementation of this method
   * does nothing.
   *
   * <p>Overriding this method and changing the frame values allows implementing branch-sensitive
   * analyses.
   *
   * @param opcode the opcode of the jump instruction. Can be IFEQ, IFNE, IFLT, IFGE, IFGT, IFLE,
   *     IF_ICMPEQ, IF_ICMPNE, IF_ICMPLT, IF_ICMPGE, IF_ICMPGT, IF_ICMPLE, IF_ACMPEQ, IF_ACMPNE,
   *     GOTO, JSR, IFNULL, IFNONNULL, TABLESWITCH or LOOKUPSWITCH.
   * @param target a target of the jump instruction this frame corresponds to, or {@literal null} if
   *     this frame corresponds to the successor of the jump instruction (i.e. the next instruction
   *     in the instructions sequence).
   */
  public void initJumpTarget(final int opcode, final LabelNode target) {
    // Does nothing by default.
  }

  Sets the expected return type of the analyzed method.
Params: v – the expected return type of the analyzed method, or null if the method returns void./**
   * Sets the expected return type of the analyzed method.
   *
   * @param v the expected return type of the analyzed method, or {@literal null} if the method
   *     returns void.
   */
  public void setReturn(final V v) {
    returnValue = v;
  }

  Returns the maximum number of local variables of this frame.
Returns: the maximum number of local variables of this frame./**
   * Returns the maximum number of local variables of this frame.
   *
   * @return the maximum number of local variables of this frame.
   */
  public int getLocals() {
    return numLocals;
  }

  Returns the maximum stack size of this frame.
Returns: the maximum stack size of this frame./**
   * Returns the maximum stack size of this frame.
   *
   * @return the maximum stack size of this frame.
   */
  public int getMaxStackSize() {
    return values.length - numLocals;
  }

  Returns the value of the given local variable.
Params: index – a local variable index.
Throws: IndexOutOfBoundsException – if the variable does not exist.
Returns: the value of the given local variable./**
   * Returns the value of the given local variable.
   *
   * @param index a local variable index.
   * @return the value of the given local variable.
   * @throws IndexOutOfBoundsException if the variable does not exist.
   */
  public V getLocal(final int index) {
    if (index >= numLocals) {
      throw new IndexOutOfBoundsException("Trying to get an inexistant local variable " + index);
    }
    return values[index];
  }

  Sets the value of the given local variable.
Params: index – a local variable index.
value – the new value of this local variable.
Throws: IndexOutOfBoundsException – if the variable does not exist./**
   * Sets the value of the given local variable.
   *
   * @param index a local variable index.
   * @param value the new value of this local variable.
   * @throws IndexOutOfBoundsException if the variable does not exist.
   */
  public void setLocal(final int index, final V value) {
    if (index >= numLocals) {
      throw new IndexOutOfBoundsException("Trying to set an inexistant local variable " + index);
    }
    values[index] = value;
  }

  Returns the number of values in the operand stack of this frame. Long and double values are
treated as single values.
Returns: the number of values in the operand stack of this frame./**
   * Returns the number of values in the operand stack of this frame. Long and double values are
   * treated as single values.
   *
   * @return the number of values in the operand stack of this frame.
   */
  public int getStackSize() {
    return numStack;
  }

  Returns the value of the given operand stack slot.
Params: index – the index of an operand stack slot.
Throws: IndexOutOfBoundsException – if the operand stack slot does not exist.
Returns: the value of the given operand stack slot./**
   * Returns the value of the given operand stack slot.
   *
   * @param index the index of an operand stack slot.
   * @return the value of the given operand stack slot.
   * @throws IndexOutOfBoundsException if the operand stack slot does not exist.
   */
  public V getStack(final int index) {
    return values[numLocals + index];
  }

  Sets the value of the given stack slot.
Params: index – the index of an operand stack slot.
value – the new value of the stack slot.
Throws: IndexOutOfBoundsException – if the stack slot does not exist./**
   * Sets the value of the given stack slot.
   *
   * @param index the index of an operand stack slot.
   * @param value the new value of the stack slot.
   * @throws IndexOutOfBoundsException if the stack slot does not exist.
   */
  public void setStack(final int index, final V value) {
    values[numLocals + index] = value;
  }

  Clears the operand stack of this frame. /** Clears the operand stack of this frame. */
  public void clearStack() {
    numStack = 0;
  }

  Pops a value from the operand stack of this frame.
Throws: IndexOutOfBoundsException – if the operand stack is empty.
Returns: the value that has been popped from the stack./**
   * Pops a value from the operand stack of this frame.
   *
   * @return the value that has been popped from the stack.
   * @throws IndexOutOfBoundsException if the operand stack is empty.
   */
  public V pop() {
    if (numStack == 0) {
      throw new IndexOutOfBoundsException("Cannot pop operand off an empty stack.");
    }
    return values[numLocals + (--numStack)];
  }

  Pushes a value into the operand stack of this frame.
Params: value – the value that must be pushed into the stack.
Throws: IndexOutOfBoundsException – if the operand stack is full./**
   * Pushes a value into the operand stack of this frame.
   *
   * @param value the value that must be pushed into the stack.
   * @throws IndexOutOfBoundsException if the operand stack is full.
   */
  public void push(final V value) {
    if (numLocals + numStack >= values.length) {
      throw new IndexOutOfBoundsException("Insufficient maximum stack size.");
    }
    values[numLocals + (numStack++)] = value;
  }

  Simulates the execution of the given instruction on this execution stack frame.
Params: insn – the instruction to execute.
interpreter – the interpreter to use to compute values from other values.
Throws: AnalyzerException – if the instruction cannot be executed on this execution frame (e.g. a
    POP on an empty operand stack)./**
   * Simulates the execution of the given instruction on this execution stack frame.
   *
   * @param insn the instruction to execute.
   * @param interpreter the interpreter to use to compute values from other values.
   * @throws AnalyzerException if the instruction cannot be executed on this execution frame (e.g. a
   *     POP on an empty operand stack).
   */
  public void execute(final AbstractInsnNode insn, final Interpreter<V> interpreter)
      throws AnalyzerException {
    V value1;
    V value2;
    V value3;
    V value4;
    int var;

    switch (insn.getOpcode()) {
      case Opcodes.NOP:
        break;
      case Opcodes.ACONST_NULL:
      case Opcodes.ICONST_M1:
      case Opcodes.ICONST_0:
      case Opcodes.ICONST_1:
      case Opcodes.ICONST_2:
      case Opcodes.ICONST_3:
      case Opcodes.ICONST_4:
      case Opcodes.ICONST_5:
      case Opcodes.LCONST_0:
      case Opcodes.LCONST_1:
      case Opcodes.FCONST_0:
      case Opcodes.FCONST_1:
      case Opcodes.FCONST_2:
      case Opcodes.DCONST_0:
      case Opcodes.DCONST_1:
      case Opcodes.BIPUSH:
      case Opcodes.SIPUSH:
      case Opcodes.LDC:
        push(interpreter.newOperation(insn));
        break;
      case Opcodes.ILOAD:
      case Opcodes.LLOAD:
      case Opcodes.FLOAD:
      case Opcodes.DLOAD:
      case Opcodes.ALOAD:
        push(interpreter.copyOperation(insn, getLocal(((VarInsnNode) insn).var)));
        break;
      case Opcodes.ISTORE:
      case Opcodes.LSTORE:
      case Opcodes.FSTORE:
      case Opcodes.DSTORE:
      case Opcodes.ASTORE:
        value1 = interpreter.copyOperation(insn, pop());
        var = ((VarInsnNode) insn).var;
        setLocal(var, value1);
        if (value1.getSize() == 2) {
          setLocal(var + 1, interpreter.newEmptyValue(var + 1));
        }
        if (var > 0) {
          Value local = getLocal(var - 1);
          if (local != null && local.getSize() == 2) {
            setLocal(var - 1, interpreter.newEmptyValue(var - 1));
          }
        }
        break;
      case Opcodes.IASTORE:
      case Opcodes.LASTORE:
      case Opcodes.FASTORE:
      case Opcodes.DASTORE:
      case Opcodes.AASTORE:
      case Opcodes.BASTORE:
      case Opcodes.CASTORE:
      case Opcodes.SASTORE:
        value3 = pop();
        value2 = pop();
        value1 = pop();
        interpreter.ternaryOperation(insn, value1, value2, value3);
        break;
      case Opcodes.POP:
        if (pop().getSize() == 2) {
          throw new AnalyzerException(insn, "Illegal use of POP");
        }
        break;
      case Opcodes.POP2:
        if (pop().getSize() == 1 && pop().getSize() != 1) {
          throw new AnalyzerException(insn, "Illegal use of POP2");
        }
        break;
      case Opcodes.DUP:
        value1 = pop();
        if (value1.getSize() != 1) {
          throw new AnalyzerException(insn, "Illegal use of DUP");
        }
        push(value1);
        push(interpreter.copyOperation(insn, value1));
        break;
      case Opcodes.DUP_X1:
        value1 = pop();
        value2 = pop();
        if (value1.getSize() != 1 || value2.getSize() != 1) {
          throw new AnalyzerException(insn, "Illegal use of DUP_X1");
        }
        push(interpreter.copyOperation(insn, value1));
        push(value2);
        push(value1);
        break;
      case Opcodes.DUP_X2:
        value1 = pop();
        if (value1.getSize() == 1) {
          value2 = pop();
          if (value2.getSize() == 1) {
            value3 = pop();
            if (value3.getSize() == 1) {
              push(interpreter.copyOperation(insn, value1));
              push(value3);
              push(value2);
              push(value1);
              break;
            }
          } else {
            push(interpreter.copyOperation(insn, value1));
            push(value2);
            push(value1);
            break;
          }
        }
        throw new AnalyzerException(insn, "Illegal use of DUP_X2");
      case Opcodes.DUP2:
        value1 = pop();
        if (value1.getSize() == 1) {
          value2 = pop();
          if (value2.getSize() == 1) {
            push(value2);
            push(value1);
            push(interpreter.copyOperation(insn, value2));
            push(interpreter.copyOperation(insn, value1));
            break;
          }
        } else {
          push(value1);
          push(interpreter.copyOperation(insn, value1));
          break;
        }
        throw new AnalyzerException(insn, "Illegal use of DUP2");
      case Opcodes.DUP2_X1:
        value1 = pop();
        if (value1.getSize() == 1) {
          value2 = pop();
          if (value2.getSize() == 1) {
            value3 = pop();
            if (value3.getSize() == 1) {
              push(interpreter.copyOperation(insn, value2));
              push(interpreter.copyOperation(insn, value1));
              push(value3);
              push(value2);
              push(value1);
              break;
            }
          }
        } else {
          value2 = pop();
          if (value2.getSize() == 1) {
            push(interpreter.copyOperation(insn, value1));
            push(value2);
            push(value1);
            break;
          }
        }
        throw new AnalyzerException(insn, "Illegal use of DUP2_X1");
      case Opcodes.DUP2_X2:
        value1 = pop();
        if (value1.getSize() == 1) {
          value2 = pop();
          if (value2.getSize() == 1) {
            value3 = pop();
            if (value3.getSize() == 1) {
              value4 = pop();
              if (value4.getSize() == 1) {
                push(interpreter.copyOperation(insn, value2));
                push(interpreter.copyOperation(insn, value1));
                push(value4);
                push(value3);
                push(value2);
                push(value1);
                break;
              }
            } else {
              push(interpreter.copyOperation(insn, value2));
              push(interpreter.copyOperation(insn, value1));
              push(value3);
              push(value2);
              push(value1);
              break;
            }
          }
        } else {
          value2 = pop();
          if (value2.getSize() == 1) {
            value3 = pop();
            if (value3.getSize() == 1) {
              push(interpreter.copyOperation(insn, value1));
              push(value3);
              push(value2);
              push(value1);
              break;
            }
          } else {
            push(interpreter.copyOperation(insn, value1));
            push(value2);
            push(value1);
            break;
          }
        }
        throw new AnalyzerException(insn, "Illegal use of DUP2_X2");
      case Opcodes.SWAP:
        value2 = pop();
        value1 = pop();
        if (value1.getSize() != 1 || value2.getSize() != 1) {
          throw new AnalyzerException(insn, "Illegal use of SWAP");
        }
        push(interpreter.copyOperation(insn, value2));
        push(interpreter.copyOperation(insn, value1));
        break;
      case Opcodes.IALOAD:
      case Opcodes.LALOAD:
      case Opcodes.FALOAD:
      case Opcodes.DALOAD:
      case Opcodes.AALOAD:
      case Opcodes.BALOAD:
      case Opcodes.CALOAD:
      case Opcodes.SALOAD:
      case Opcodes.IADD:
      case Opcodes.LADD:
      case Opcodes.FADD:
      case Opcodes.DADD:
      case Opcodes.ISUB:
      case Opcodes.LSUB:
      case Opcodes.FSUB:
      case Opcodes.DSUB:
      case Opcodes.IMUL:
      case Opcodes.LMUL:
      case Opcodes.FMUL:
      case Opcodes.DMUL:
      case Opcodes.IDIV:
      case Opcodes.LDIV:
      case Opcodes.FDIV:
      case Opcodes.DDIV:
      case Opcodes.IREM:
      case Opcodes.LREM:
      case Opcodes.FREM:
      case Opcodes.DREM:
      case Opcodes.ISHL:
      case Opcodes.LSHL:
      case Opcodes.ISHR:
      case Opcodes.LSHR:
      case Opcodes.IUSHR:
      case Opcodes.LUSHR:
      case Opcodes.IAND:
      case Opcodes.LAND:
      case Opcodes.IOR:
      case Opcodes.LOR:
      case Opcodes.IXOR:
      case Opcodes.LXOR:
      case Opcodes.LCMP:
      case Opcodes.FCMPL:
      case Opcodes.FCMPG:
      case Opcodes.DCMPL:
      case Opcodes.DCMPG:
        value2 = pop();
        value1 = pop();
        push(interpreter.binaryOperation(insn, value1, value2));
        break;
      case Opcodes.INEG:
      case Opcodes.LNEG:
      case Opcodes.FNEG:
      case Opcodes.DNEG:
        push(interpreter.unaryOperation(insn, pop()));
        break;
      case Opcodes.IINC:
        var = ((IincInsnNode) insn).var;
        setLocal(var, interpreter.unaryOperation(insn, getLocal(var)));
        break;
      case Opcodes.I2L:
      case Opcodes.I2F:
      case Opcodes.I2D:
      case Opcodes.L2I:
      case Opcodes.L2F:
      case Opcodes.L2D:
      case Opcodes.F2I:
      case Opcodes.F2L:
      case Opcodes.F2D:
      case Opcodes.D2I:
      case Opcodes.D2L:
      case Opcodes.D2F:
      case Opcodes.I2B:
      case Opcodes.I2C:
      case Opcodes.I2S:
        push(interpreter.unaryOperation(insn, pop()));
        break;
      case Opcodes.IFEQ:
      case Opcodes.IFNE:
      case Opcodes.IFLT:
      case Opcodes.IFGE:
      case Opcodes.IFGT:
      case Opcodes.IFLE:
        interpreter.unaryOperation(insn, pop());
        break;
      case Opcodes.IF_ICMPEQ:
      case Opcodes.IF_ICMPNE:
      case Opcodes.IF_ICMPLT:
      case Opcodes.IF_ICMPGE:
      case Opcodes.IF_ICMPGT:
      case Opcodes.IF_ICMPLE:
      case Opcodes.IF_ACMPEQ:
      case Opcodes.IF_ACMPNE:
      case Opcodes.PUTFIELD:
        value2 = pop();
        value1 = pop();
        interpreter.binaryOperation(insn, value1, value2);
        break;
      case Opcodes.GOTO:
        break;
      case Opcodes.JSR:
        push(interpreter.newOperation(insn));
        break;
      case Opcodes.RET:
        break;
      case Opcodes.TABLESWITCH:
      case Opcodes.LOOKUPSWITCH:
        interpreter.unaryOperation(insn, pop());
        break;
      case Opcodes.IRETURN:
      case Opcodes.LRETURN:
      case Opcodes.FRETURN:
      case Opcodes.DRETURN:
      case Opcodes.ARETURN:
        value1 = pop();
        interpreter.unaryOperation(insn, value1);
        interpreter.returnOperation(insn, value1, returnValue);
        break;
      case Opcodes.RETURN:
        if (returnValue != null) {
          throw new AnalyzerException(insn, "Incompatible return type");
        }
        break;
      case Opcodes.GETSTATIC:
        push(interpreter.newOperation(insn));
        break;
      case Opcodes.PUTSTATIC:
        interpreter.unaryOperation(insn, pop());
        break;
      case Opcodes.GETFIELD:
        push(interpreter.unaryOperation(insn, pop()));
        break;
      case Opcodes.INVOKEVIRTUAL:
      case Opcodes.INVOKESPECIAL:
      case Opcodes.INVOKESTATIC:
      case Opcodes.INVOKEINTERFACE:
        executeInvokeInsn(insn, ((MethodInsnNode) insn).desc, interpreter);
        break;
      case Opcodes.INVOKEDYNAMIC:
        executeInvokeInsn(insn, ((InvokeDynamicInsnNode) insn).desc, interpreter);
        break;
      case Opcodes.NEW:
        push(interpreter.newOperation(insn));
        break;
      case Opcodes.NEWARRAY:
      case Opcodes.ANEWARRAY:
      case Opcodes.ARRAYLENGTH:
        push(interpreter.unaryOperation(insn, pop()));
        break;
      case Opcodes.ATHROW:
        interpreter.unaryOperation(insn, pop());
        break;
      case Opcodes.CHECKCAST:
      case Opcodes.INSTANCEOF:
        push(interpreter.unaryOperation(insn, pop()));
        break;
      case Opcodes.MONITORENTER:
      case Opcodes.MONITOREXIT:
        interpreter.unaryOperation(insn, pop());
        break;
      case Opcodes.MULTIANEWARRAY:
        List<V> valueList = new ArrayList<>();
        for (int i = ((MultiANewArrayInsnNode) insn).dims; i > 0; --i) {
          valueList.add(0, pop());
        }
        push(interpreter.naryOperation(insn, valueList));
        break;
      case Opcodes.IFNULL:
      case Opcodes.IFNONNULL:
        interpreter.unaryOperation(insn, pop());
        break;
      default:
        throw new AnalyzerException(insn, "Illegal opcode " + insn.getOpcode());
    }
  }

  private void executeInvokeInsn(
      final AbstractInsnNode insn, final String methodDescriptor, final Interpreter<V> interpreter)
      throws AnalyzerException {
    ArrayList<V> valueList = new ArrayList<>();
    for (int i = Type.getArgumentTypes(methodDescriptor).length; i > 0; --i) {
      valueList.add(0, pop());
    }
    if (insn.getOpcode() != Opcodes.INVOKESTATIC && insn.getOpcode() != Opcodes.INVOKEDYNAMIC) {
      valueList.add(0, pop());
    }
    if (Type.getReturnType(methodDescriptor) == Type.VOID_TYPE) {
      interpreter.naryOperation(insn, valueList);
    } else {
      push(interpreter.naryOperation(insn, valueList));
    }
  }

  Merges the given frame into this frame.
Params: frame – a frame. This frame is left unchanged by this method.
interpreter – the interpreter used to merge values.
Throws: AnalyzerException – if the frames have incompatible sizes.
Returns: true if this frame has been changed as a result of the merge operation, or false otherwise./**
   * Merges the given frame into this frame.
   *
   * @param frame a frame. This frame is left unchanged by this method.
   * @param interpreter the interpreter used to merge values.
   * @return {@literal true} if this frame has been changed as a result of the merge operation, or
   *     {@literal false} otherwise.
   * @throws AnalyzerException if the frames have incompatible sizes.
   */
  public boolean merge(final Frame<? extends V> frame, final Interpreter<V> interpreter)
      throws AnalyzerException {
    if (numStack != frame.numStack) {
      throw new AnalyzerException(null, "Incompatible stack heights");
    }
    boolean changed = false;
    for (int i = 0; i < numLocals + numStack; ++i) {
      V v = interpreter.merge(values[i], frame.values[i]);
      if (!v.equals(values[i])) {
        values[i] = v;
        changed = true;
      }
    }
    return changed;
  }

  Merges the given frame into this frame (case of a subroutine). The operand stacks are not
merged, and only the local variables that have not been used by the subroutine are merged.
Params: frame – a frame. This frame is left unchanged by this method.
localsUsed – the local variables that are read or written by the subroutine. The i-th
    element is true if and only if the local variable at index i is read or written by the
    subroutine.
Returns: true if this frame has been changed as a result of the merge operation, or false otherwise./**
   * Merges the given frame into this frame (case of a subroutine). The operand stacks are not
   * merged, and only the local variables that have not been used by the subroutine are merged.
   *
   * @param frame a frame. This frame is left unchanged by this method.
   * @param localsUsed the local variables that are read or written by the subroutine. The i-th
   *     element is true if and only if the local variable at index i is read or written by the
   *     subroutine.
   * @return {@literal true} if this frame has been changed as a result of the merge operation, or
   *     {@literal false} otherwise.
   */
  public boolean merge(final Frame<? extends V> frame, final boolean[] localsUsed) {
    boolean changed = false;
    for (int i = 0; i < numLocals; ++i) {
      if (!localsUsed[i] && !values[i].equals(frame.values[i])) {
        values[i] = frame.values[i];
        changed = true;
      }
    }
    return changed;
  }

  Returns a string representation of this frame.
Returns: a string representation of this frame./**
   * Returns a string representation of this frame.
   *
   * @return a string representation of this frame.
   */
  @Override
  public String toString() {
    StringBuilder stringBuilder = new StringBuilder();
    for (int i = 0; i < getLocals(); ++i) {
      stringBuilder.append(getLocal(i));
    }
    stringBuilder.append(' ');
    for (int i = 0; i < getStackSize(); ++i) {
      stringBuilder.append(getStack(i).toString());
    }
    return stringBuilder.toString();
  }
}
Author:	Eric Bruneton
Type parameters:	<V> – type of the Value used for the analysis.
Params:	index – a local variable index.
Throws:	IndexOutOfBoundsException – if the variable does not exist.
Returns:	the value of the given local variable.
Params:	index – a local variable index. value – the new value of this local variable.
Throws:	IndexOutOfBoundsException – if the variable does not exist.
Params:	index – the index of an operand stack slot.
Throws:	IndexOutOfBoundsException – if the operand stack slot does not exist.
Returns:	the value of the given operand stack slot.
Params:	value – the value that must be pushed into the stack.
Throws:	IndexOutOfBoundsException – if the operand stack is full.
Params:	insn – the instruction to execute. interpreter – the interpreter to use to compute values from other values.
Throws:	AnalyzerException – if the instruction cannot be executed on this execution frame (e.g. a POP on an empty operand stack).
Params:	frame – a frame. This frame is left unchanged by this method. interpreter – the interpreter used to merge values.
Throws:	AnalyzerException – if the frames have incompatible sizes.
Returns:	true if this frame has been changed as a result of the merge operation, or false otherwise.
/

org.ow2.asm/ asm-analysis/ 7.1/ org/objectweb/asm/tree/analysis/Frame.java
