org.objectweb.asm.Opcodes# DUP_X1 ( ) 源码实例Demo

private void invokeRecordAllocation(String typeName) {
  Matcher matcher = namePattern.matcher(typeName);
  if (matcher.find()) {
    typeName = matcher.group(1);
  }
  // stack: ... count newobj
  super.visitInsn(Opcodes.DUP_X1);
  // -> stack: ... newobj count newobj
  super.visitLdcInsn(typeName);
  // -> stack: ... newobj count newobj typename
  super.visitInsn(Opcodes.SWAP);
  // -> stack: ... newobj count typename newobj
  super.visitMethodInsn(
      Opcodes.INVOKESTATIC, recorderClass, recorderMethod, RECORDER_SIGNATURE, false);
  // -> stack: ... newobj
}
 

public static int getDupXOpcode(Type dType, Type bType) {
	if (dType.getSize() == 1 && bType.getSize() == 1) {
		return Opcodes.DUP_X1;
	} else if (dType.getSize() == 1 && bType.getSize() == 2) {
		return Opcodes.DUP_X2;
	} else if (dType.getSize() == 2 && bType.getSize() == 1) {
		return Opcodes.DUP2_X1;
	} else if (dType.getSize() == 2 && bType.getSize() == 2) {
		return Opcodes.DUP2_X2;
	} else {
		throw new IllegalArgumentException(dType.toString() + " " + bType.toString());
	}
}
 

void calculateArrayLengthAndDispatch(String typeName, int dimCount) {
  // Since the dimensions of the array are not known at instrumentation
  // time, we take the created multi-dimensional array and peel off nesting
  // levels from the left.  For each nesting layer we probe the array length
  // and accumulate a partial product which we can then feed the recording
  // function.

  // below we note the partial product of dimensions 1 to X-1 as productToX
  // (so productTo1 == 1 == no dimensions yet).  We denote by aref0 the
  // array reference at the current nesting level (the containing aref's [0]
  // element).  If we hit a level whose arraylength is 0 or whose
  // reference is null, there's no point continuing, so we shortcut
  // out.

  // This approach works pretty well when you create a new array with the
  // newarray bytecodes.  You can also create a new array by cloning an
  // existing array; an existing multidimensional array might have had some
  // of its [0] elements nulled out.  We currently deal with this by bailing
  // out, but arguably we should do something more principled (like calculate
  // the size of the multidimensional array from scratch if you are using
  // clone()).
  // TODO(java-platform-team): Do something about modified multidimensional
  // arrays and clone().
  Label zeroDimension = new Label();
  super.visitInsn(Opcodes.DUP); // -> stack: ... origaref aref0
  super.visitLdcInsn(1); // -> stack: ... origaref aref0 productTo1
  for (int i = 0; i < dimCount; ++i) {
    // pre: stack: ... origaref aref0 productToI
    super.visitInsn(Opcodes.SWAP); // -> stack: ... origaref productToI aref
    super.visitInsn(Opcodes.DUP);

    Label nonNullDimension = new Label();
    // -> stack: ... origaref productToI aref aref
    super.visitJumpInsn(Opcodes.IFNONNULL, nonNullDimension);
    // -> stack: ... origaref productToI aref
    super.visitInsn(Opcodes.SWAP);
    // -> stack: ... origaref aref productToI
    super.visitJumpInsn(Opcodes.GOTO, zeroDimension);
    super.visitLabel(nonNullDimension);

    // -> stack: ... origaref productToI aref
    super.visitInsn(Opcodes.DUP_X1);
    // -> stack: ... origaref aref0 productToI aref
    super.visitInsn(Opcodes.ARRAYLENGTH);
    // -> stack: ... origaref aref0 productToI dimI

    Label nonZeroDimension = new Label();
    super.visitInsn(Opcodes.DUP);
    // -> stack: ... origaref aref0 productToI dimI dimI
    super.visitJumpInsn(Opcodes.IFNE, nonZeroDimension);
    // -> stack: ... origaref aref0 productToI dimI
    super.visitInsn(Opcodes.POP);
    // -> stack: ... origaref aref0 productToI
    super.visitJumpInsn(Opcodes.GOTO, zeroDimension);
    super.visitLabel(nonZeroDimension);
    // -> stack: ... origaref aref0 productToI max(dimI,1)

    super.visitInsn(Opcodes.IMUL);
    // -> stack: ... origaref aref0 productTo{I+1}
    if (i < dimCount - 1) {
      super.visitInsn(Opcodes.SWAP);
      // -> stack: ... origaref productTo{I+1} aref0
      super.visitInsn(Opcodes.ICONST_0);
      // -> stack: ... origaref productTo{I+1} aref0 0
      super.visitInsn(Opcodes.AALOAD);
      // -> stack: ... origaref productTo{I+1} aref0'
      super.visitInsn(Opcodes.SWAP);
    }
    // post: stack: ... origaref aref0 productTo{I+1}
  }
  super.visitLabel(zeroDimension);

  super.visitInsn(Opcodes.SWAP); // -> stack: ... origaref product aref0
  super.visitInsn(Opcodes.POP); // -> stack: ... origaref product
  super.visitInsn(Opcodes.SWAP); // -> stack: ... product origaref
  invokeRecordAllocation(typeName);
}