Rail Analysis (EM/IR drop)

[harrisonliew]

Added ability to characterize technology (stdcells) library and macros for EM + IR drop analysis (both static + dynamic).

Some notes:

• EM/IR requires power grid view libraries to be created. The init_technology step creates these once for the technology (stdcells) and for all macros (given in vlsi.inputs.extra_libraries), unless the list of extra libraries has changed.
• The rail analysis uses the current information from static/dynamic power analysis, and is implemented as a generic method that can be called by either the static_rail and active_rail steps.
• Rail analysis comes after static + dynamic power analysis, or else an implicit set_pg_nets from set_rail_analysis_config overrides the supply voltage for subsequent power analysis.
• The read_spef command was fixed--it was erroring out because the corner/file pairing wasn't done properly.

Fixes needed before this PR can be merged:

• Need to get the list of cells from extra libraries, perhaps from the name of each Library. Documentation also needs to reflect that for macro PG views, each Library must have a name and each set of files can only contain 1 cell.
• Fix error caused by reading additional LEFs or reading LEFs over again b/w tech/stdcell PGV generation and macro PGV generation. Seems to require design is dumped (yet reset_design errors out) or init_design to be called first?
• Separate filler and decap cells in tech's list of special cells. This way, characterization of area decapacitance can be done (if technology has that information)
• Add corner-specific Spice models (and corner flags) to tech JSON schema, and skip stdcell PG view creation if these aren't specified. Currently this is hardcoded for the ASAP7 case.
• Need a massive MMMC overhaul to support more corners and things like QRC should be tied to stackups and not MMMC corners
• Fix read_spef sequence relying on fact that the list of spefs was written in the [setup, hold] order by Innovus plugin

TODOs potentially in other PRs:

• Automatically populate power.inputs.database from Innovus
• Make a util to get the actual cell name for macros rather than relying on Library name property
• Fix generating PG views in the non-MMMC case (can only have 1 QRC file)
• Need to actually get combinations of all power nets + power domains, not just nets for power data. Alternatively, need to write TCL get all relevant .ptiavg files by parsing the .ptifiles file generated by power analysis.
• To report_irdrop_regions, the highest run number in the rail analysis output dir needs to be parsed and incremented in order to reference the correct database.
• Script to open Voltus, read the rail analysis database, generate visualization, and display waveforms.
• Documentation in main Hammer repo.

[dpgrubb13]

Not that it would necessarily need to be included in this PR, but do you think it would be useful to generate an open_chip type script for the rail analysis results like in the Innovus plugin?

Ah, just saw the TODO for future PRs, so that's covered already!

[dpgrubb13]

Looks good, comments were resolved. We just need to make sure to track the remaining TODOs.