org.objectweb.asm.Opcodes# FNEG 源码实例Demo

/**
 * Mutates a primitive float return (<code>Opcode.FRETURN</code>). The
 * strategy used was translated from jumble BCEL code. The following is
 * complicated by the problem of <tt>NaN</tt>s. By default the new value is
 * <code>-(x + 1)</code>, but this doesn't work for <tt>NaN</tt>s. But for a
 * <tt>NaN</tt> <code>x != x</code> is true, and we use this to detect them.
 *
 * @see #mutatePrimitiveDoubleReturn()
 */
private void mutatePrimitiveFloatReturn() {
  if (shouldMutate("primitive float", "(x != NaN)? -(x + 1) : -1 ")) {
    final Label label = new Label();

    super.visitInsn(Opcodes.DUP);
    super.visitInsn(Opcodes.DUP);
    super.visitInsn(Opcodes.FCMPG);
    super.visitJumpInsn(Opcodes.IFEQ, label);

    super.visitInsn(Opcodes.POP);
    super.visitInsn(Opcodes.FCONST_0);

    // the following code is executed in NaN case, too
    super.visitLabel(label);
    super.visitInsn(Opcodes.FCONST_1);
    super.visitInsn(Opcodes.FADD);
    super.visitInsn(Opcodes.FNEG);
    super.visitInsn(Opcodes.FRETURN);
  }
}
 

public final void neg(Type type) {
    switch (type.getOpcode(Opcodes.INEG)) {
    case Opcodes.INEG:
        ineg();
        return;
    case Opcodes.LNEG:
        lneg();
        return;
    case Opcodes.FNEG:
        fneg();
        return;
    case Opcodes.DNEG:
        dneg();
        return;
    default:
        throw new IllegalArgumentException();
    }
}
 

public static int getNegateOpcode(Type type) {
	if (type == Type.INT_TYPE || type == Type.SHORT_TYPE || type == Type.BYTE_TYPE) {
		return Opcodes.INEG;
	} else if (type == Type.LONG_TYPE) {
		return Opcodes.LNEG;
	} else if (type == Type.FLOAT_TYPE) {
		return Opcodes.FNEG;
	} else if (type == Type.DOUBLE_TYPE) {
		return Opcodes.DNEG;
	} else {
		throw new IllegalArgumentException(type.toString());
	}
}
 

public InsnValue invertValue(AbstractInsnNode insn, InsnValue value) {
	Object obj = value.getValue();
	switch (insn.getOpcode()) {
	case Opcodes.INEG:
		if (obj == null) {
			return InsnValue.INT_VALUE;
		}
		return InsnValue.intValue(-1 * (int) obj);
	case Opcodes.LNEG:
		if (obj == null) {
			return InsnValue.LONG_VALUE;
		}
		return InsnValue.longValue(-1L * (long) obj);
	case Opcodes.FNEG:
		if (obj == null) {
			return InsnValue.FLOAT_VALUE;
		}
		return InsnValue.floatValue(-1F * (float) obj);
	case Opcodes.DNEG:
		if (obj == null) {
			return InsnValue.DOUBLE_VALUE;
		}
		return InsnValue.doubleValue(-1D * (double) obj);
	}

	return null;
}
 

public static boolean isArithmeticOp(Instruction instr) {
    
    switch (instr.getOpcode()) {
        case Opcodes.ISHL:
        case Opcodes.ISHR:
        case Opcodes.LSHL:
        case Opcodes.LSHR:
        case Opcodes.IUSHR:
        case Opcodes.LUSHR:
        
        case Opcodes.DCMPG:
        case Opcodes.DCMPL:
        case Opcodes.FCMPG:
        case Opcodes.FCMPL:
        case Opcodes.LCMP:
        case Opcodes.FNEG:
        case Opcodes.DNEG:
        case Opcodes.INEG:
        case Opcodes.D2F:
        case Opcodes.D2I:
        case Opcodes.D2L:
        case Opcodes.F2D:
        case Opcodes.F2I:
        case Opcodes.F2L:
        case Opcodes.L2D:
        case Opcodes.L2F:
        case Opcodes.L2I:
        case Opcodes.I2L:
        case Opcodes.I2B:
        case Opcodes.I2C:
        case Opcodes.I2D:
        case Opcodes.I2F:
        case Opcodes.I2S:
        case Opcodes.IOR:
        case Opcodes.LOR:
        case Opcodes.IXOR:
        case Opcodes.LXOR:
        case Opcodes.IAND:
        case Opcodes.LAND:
        case Opcodes.FADD:
        case Opcodes.DADD:
        case Opcodes.IADD:
        case Opcodes.LADD:
        case Opcodes.FSUB:
        case Opcodes.DSUB:
        case Opcodes.ISUB:
        case Opcodes.LSUB:
        case Opcodes.FDIV:
        case Opcodes.DDIV:
        case Opcodes.LDIV:
        case Opcodes.IDIV:
        case Opcodes.IREM:
        case Opcodes.FREM:
        case Opcodes.DREM:
        case Opcodes.LREM:
        case Opcodes.FMUL:
        case Opcodes.DMUL:
        case Opcodes.IMUL:
        case Opcodes.LMUL:
            return true;
    }
    return false;
}