Java 类org.apache.bcel.generic.NOP 实例源码

void removeUnusedLocals(Method mOrig, MethodGen m) {
    InstructionList il = m.getInstructionList();
    InstructionHandle[] ins = il.getInstructionHandles();
    for (int i = 0; i < ins.length; i++) {
        Instruction in = ins[i].getInstruction();

        if (in instanceof LocalVariableInstruction) {
            LocalVariableInstruction curr = (LocalVariableInstruction) in;
            if (mtab.getLocal(m, curr, ins[i].getPosition()) != null
                && curr.getIndex() < m.getMaxLocals() - 5
                && !mtab.isLocalUsedInInlet(mOrig, curr.getIndex())) {
                if (curr instanceof IINC) {
                    ins[i].setInstruction(new NOP());
                } else if (curr instanceof LSTORE || curr instanceof DSTORE) {
                    ins[i].setInstruction(new POP2());
                } else if (curr instanceof StoreInstruction) {
                    ins[i].setInstruction(new POP());
                } else if (curr instanceof ALOAD) {
                    ins[i].setInstruction(new ACONST_NULL());
                } else if (curr instanceof FLOAD) {
                    ins[i].setInstruction(new FCONST((float) 0.0));
                } else if (curr instanceof ILOAD) {
                    ins[i].setInstruction(new ICONST(0));
                } else if (curr instanceof DLOAD) {
                    ins[i].setInstruction(new DCONST(0.0));
                } else if (curr instanceof LLOAD) {
                    ins[i].setInstruction(new LCONST(0L));
                } else {
                    System.out.println("unhandled ins in "
                        + "removeUnusedLocals: " + curr);
                    System.exit(1);
                }
            }
        }
    }
}

private @CheckForNull
InstructionHandle getPreviousInstruction(InstructionHandle handle, boolean skipNops) {
    while (handle.getPrev() != null) {
        handle = handle.getPrev();
        Instruction prevIns = handle.getInstruction();
        if (!(prevIns instanceof NOP && skipNops)) {
            return handle;
        }
    }
    return null;
}

public void build() throws CFGBuilderException {
    InstructionList instructionList = methodGen.getInstructionList();
    optimize(instructionList);
    topLevelSubroutine = new Subroutine(instructionList.getStart());
    subroutineWorkList.add(topLevelSubroutine);

    // Build top level subroutine and all JSR subroutines
    while (!subroutineWorkList.isEmpty()) {
        Subroutine subroutine = subroutineWorkList.removeFirst();
        if (DEBUG)
            System.out.println("Starting subroutine " + subroutine.getStartInstruction());
        build(subroutine);
    }

    // Inline everything into the top level subroutine
    cfg = inlineAll();

    // Add a NOP instruction to the entry block.
    // This allows analyses to construct a Location
    // representing the entry to the method.
    BasicBlock entryBlock = cfg.getEntry();
    InstructionList il = new InstructionList();
    entryBlock.addInstruction(il.append(new NOP()));

    if (VERIFY_INTEGRITY)
        cfg.checkIntegrity();

    if (true) {
        cfg.checkIntegrity();

    }
}

private @CheckForNull
InstructionHandle getPreviousInstruction(InstructionHandle handle, boolean skipNops) {
    while (handle.getPrev() != null) {
        handle = handle.getPrev();
        Instruction prevIns = handle.getInstruction();
        if (!(prevIns instanceof NOP && skipNops)) {
            return handle;
        }
    }
    return null;
}

public void build() throws CFGBuilderException {
    InstructionList instructionList = methodGen.getInstructionList();
    optimize(instructionList);
    topLevelSubroutine = new Subroutine(instructionList.getStart());
    subroutineWorkList.add(topLevelSubroutine);

    // Build top level subroutine and all JSR subroutines
    while (!subroutineWorkList.isEmpty()) {
        Subroutine subroutine = subroutineWorkList.removeFirst();
        if (DEBUG)
            System.out.println("Starting subroutine " + subroutine.getStartInstruction());
        build(subroutine);
    }

    // Inline everything into the top level subroutine
    cfg = inlineAll();

    // Add a NOP instruction to the entry block.
    // This allows analyses to construct a Location
    // representing the entry to the method.
    BasicBlock entryBlock = cfg.getEntry();
    InstructionList il = new InstructionList();
    entryBlock.addInstruction(il.append(new NOP()));

    if (VERIFY_INTEGRITY)
        cfg.checkIntegrity();

    if (true) {
        cfg.checkIntegrity();

    }
}

@SuppressWarnings("unused")
// Called using reflection
private Instruction createInstructionNop(Element inst) {
    return new NOP();
}