Expand y_range Search for ymax

[amin1377]

In the find_compatible_compressed_loc_in_range function (Link), after an x location is chosen (in the compressed grid), the function retrieves the y locations of the corresponding x location (where blocks of the given type exist in that column) and checks if search_range.ymin exists in the column. If it doesn't, the search range is expanded to include the entire column (Link). I was wondering if expanding the search range to the entire column when ymax doesn't exist has been tried. The current implementation effectively moves IO blocks from the top edge to the bottom edge, but not vice versa.
@vaughnbetz: I can implement it if you think it is worth trying, and let you know the results.

[vaughnbetz]

That sounds reasonable to me. Not being able to move I/Os from the top to the bottom edge will not be good -- easy to get stuck. Seems worth trying.