search

The-OpenROAD-Project / OpenLane

OpenLane is an automated RTL to GDSII flow based on several components including OpenROAD, Yosys, Magic, Netgen and custom methodology scripts for design exploration and optimization.
https://openlane.readthedocs.io/
Apache License 2.0
1.35k stars 373 forks source link

Special cells should be marked as dont use by synthesis #1787

Open mguthaus opened 1 year ago

mguthaus commented 1 year ago

Description

clkbuf cells are used as standard cells. These should be excluded during synthesis and resizing since they are balanced and probably not "efficient" in terms of area. Example where a short path is using a clkbuf:

image

Expected Behavior

I would expect clkbuf cells to be excluded from everything but CTS.

Environment report

Kernel: Linux v6.0.12-76060012-generic
Distribution: pop 20.04
Python: v3.9.12 (OK)
Container Engine: docker v23.0.5 (OK)
OpenLane Git Version: ed194238ac359aca044c54fa8cbbbd12280e1a8c
pip: INSTALLED
python-venv: INSTALLED
---
PDK Version Verification Status: FAILED
/home/mrg/courses/OpenLane/pdks/sky130A not found.
Traceback (most recent call last):
  File "/home/mrg/courses/OpenLane/dependencies/verify_versions.py", line 76, in verify_versions
    raise Exception(f"{pdk_dir} not found.")
Exception: /home/mrg/courses/OpenLane/pdks/sky130A not found.

Failed to verify sky130A.
---
Git Log (Last 3 Commits)

ed194238 2023-03-29T15:14:23+02:00 Move Timing Checks After Report Generation (#1706) - Mohamed Gaber -  (HEAD -> master, tag: 2023.03.30, origin/master, origin/HEAD)
c2944188 2023-03-29T14:34:48+02:00 Revert "#1703" (#1705) - Mohamed Gaber -  ()
54d5b5a3 2023-03-29T14:01:00+02:00 Fix regression in #1685 (#1703) - Mohamed Gaber -  ()
---
Git Remotes

origin  https://github.com/The-OpenROAD-Project/OpenLane (fetch)
origin  https://github.com/The-OpenROAD-Project/OpenLane (push)

Reproduction material

I synthesized picorv32a with a clock period of 6ns.

Relevant log output

See above timing path.
kareefardi commented 3 months ago

Seems like a similar issue to the one raised here https://github.com/The-OpenROAD-Project/OpenLane/issues/1035