Fix shape inference for math operators

[EliaGeretto]

Supposing to have a label lb, corresponding to the bit vector 001111, the path describing it on the tree could be as follows, with lb pointing to the node that contains [5,6).

     [0,0)
     /
  [0,2)
   / \
...  [2,3)
        \
        [3,4)
           \
           [4,5)
              \
              [5,6)

Calling infer_shape2(lb, 4), the function should be able to group bytes from 2 to 5 together. This, however, with the current implementation, does not happen. After some debugging, it appears that the for loop is moving the cur_lb one too many times and make it point to the root, instead of [2, 3), when terminating the loop. This patch fixes that behavior and correctly groups the bytes, producing the following tree after the execution:

     [0,0)
     /
  [0,2)
   / \
...  [2,6)
        \
        [3,4)
           \
           [4,5)
              \
              [5,6)

If this is not the intended behavior, please let me know.

[EliaGeretto]

My doubt on the expected behavior stems from the fact that using the infer_shape function to merge those four bytes together, the resulting tree would be the following:

     [0,0)
     /
  [0,2)
   / \
...  [2,3)
        \
        [3,4)
           \
           [4,5)
              \
              [2,6)

As you can see, the node that gets modified is the one at the bottom and not the one at the top.

[spinpx]

Thanks for your feedback, EliaGeretto. It is not intended behaviors. I have merged it to dev branch and will merge to master soon.

[EliaGeretto]

Thank you for your clarification! However, there is still a question that you did not answered. Is the difference between shape inference for math operators and loads intended? The difference between the second and the third tree I posted here. In the first, the aggregation node is at the beginning of the sequence, in the second one, it is at the end.

If you want to make the behavior uniform, I can create another pull request. It's a single line change within the same function.

[spinpx]

You are right. They had better should be consistent. I fix this issue, and add tests in 66582b3 .

Pleasse check it.
Thanks.