The following code:

class Test {
    void test(int[] ary, int p, int inc) {
        ary[p]+= inc;
    }
}

Used to generate this bytecode:

void test(int[], int, int);
  Code:
   Stack=4, Locals=4, Args_size=4
   0: aload_1
   1: iload_2
   2: dup2
   3: iaload
   4: iload_3
   5: iadd
   6: iastore
   7: return


Now it generates this:

void test(int[], int, int);
  Code:
   Stack=4, Locals=6, Args_size=4
   0: aload_1
   1: astore 4
   3: iload_2
   4: istore 5
   6: aload 4
   8: iload 5
   10: aload 4
   12: iload 5
   14: iaload
   15: iload_3
   16: iadd
   17: dup_x2
   18: iastore
   19: pop
   20: return