Tapeout: Final error check for Innovus

[steveri]

As far as I could tell, there was no final error check in the tapeout scripts. So I put one in. The relevant scripts include sr_count_errors.tcl (called from top_garnet_staged.tcl) and sr_finalfix.tcl).

I use the command check_drc to do the final error check at the very end, just before tape streamout. Initially it found about a million DRC violations. Eventually I managed to get this down to zero by

• delete sealring: 1M errors => 50K errors

• reduce extra-large ICOVL blockages (BIGBLOCK issue #395)
  51K errors => 18K errors

• ICOVL blockages instead of halos (SPACE1703 issue #393)
  15K => 11K

• delete tile_id straps (M4CGRA issue #394)
  11K => 300

• delete M8 blockages across top of chip (issue #396)
  300 => 6

• delete iphy blockages (see sr_count_errors.tcl)
  6 => 2

• fix double corner (see sr_count_errors.tcl, sr_finalfix.tcl)
  2 => 0

After the check, I replace the tile_id straps.

My questions:

• is there a reason why there was no final error check in the script?
• is this a reasonable thing to do and/or is there a better thing?

Also: yes I know that the important check is the Calibre DRC, but it
seems like getting the innovus script DRC-free is also a good goal?