Variable Migration Guides

These are migration guides for some particularly complex variables from OpenLane 1.

Note

In this document, OpenLane 1 refers to OpenLane versions before the release of 2.0.0, and OpenLane 2 refers to 2.0.0 or higher.

Migrating FP_PDN_VOFFSET/FP_PDN_HOFFSET/FP_PDN_VPITCH/FP_PDN_HPITCH for smaller designs

When working with smaller designs, OpenLane 1 used to scale down the PDN pitch/offset values by a factor of 4 so at least one set of PDN straps would be able to connect to the design.

This was a bit too magical and not entirely deterministic, and thus OpenLane 2 will no longer automatically do this scaling down for you. You will have to manually calculate the scale.

See Power Distribution Networks for more info.

Migrating DIODE_INSERTION_STRATEGY

As they were extremely complex, the OpenLane 1 diode insertion strategies were replaced by two flags in OpenLane 2’s “Classic” flow:

  • GRT_REPAIR_ANTENNAS: Attempts to repair antennas by enabling the step OpenROAD.RepairAntennas that invokes OpenROAD’s repair_antennas function

  • RUN_HEURISTIC_DIODE_INSERTION: Runs a custom script by Sylvain Munaut that inserts diodes based on a net’s Manhattan distance at global placement time.

The mapping for the strategies is as follows:

  • Strategies 1, 2 and 5 will throw an error.

    • 1 is an unreasonable brute force approach that adds a diode to every single net. 2 and 5 utilize replaceable “fake diode” fill cells, which are a hack that will not be available in all PDKs.

  • Strategy 0:

    • Both flags are set to false.

  • Strategy 3:

    • GRT_REPAIR_ANTENNAS is set to true.

  • Strategy 4:

    • RUN_HEURISTIC_DIODE_INSERTION is set to true.

  • Strategy 6:

    • Both flags are set to true.

Although for now OpenLane 2 will attempt the conversion for you automatically, it is recommended you update your designs as this feature will get removed.