OpenLane/docs/source/flow_overview.md

OpenLane Architecture

OpenLane Design Stages

OpenLane flow consists of several stages. By default all flow steps are run in sequence. Each stage may consist of multiple sub-stages. OpenLane can also be run interactively as shown here.

1. Synthesis
   1. yosys/abc - Perform RTL synthesis and technology mapping.
   2. OpenSTA - Performs static timing analysis on the resulting netlist to generate timing reports
2. Floorplaning
   1. init_fp - Defines the core area for the macro as well as the rows (used for placement) and the tracks (used for routing)
   2. ioplacer - Places the macro input and output ports
   3. pdngen - Generates the power distribution network
   4. tapcell - Inserts welltap and decap cells in the floorplan
3. Placement
   1. RePLace - Performs global placement
   2. Resizer - Performs optional optimizations on the design
   3. OpenDP - Performs detailed placement to legalize the globally placed components
4. CTS
   1. TritonCTS - Synthesizes the clock distribution network (the clock tree)
5. Routing
   1. FastRoute - Performs global routing to generate a guide file for the detailed router
   2. TritonRoute - Performs detailed routing
   3. OpenRCX - Performs SPEF extraction
6. Tapeout
   1. Magic - Streams out the final GDSII layout file from the routed def
   2. KLayout - Streams out the final GDSII layout file from the routed def as a back-up
7. Signoff
   1. Magic - Performs DRC Checks & Antenna Checks
   2. KLayout - Performs DRC Checks
   3. Netgen - Performs LVS Checks
   4. CVC - Performs Circuit Validity Checks

OpenLane integrated several key open source tools over the execution stages:

• RTL Synthesis, Technology Mapping, and Formal Verification : yosys + abc
• Static Timing Analysis: OpenSTA
• Floor Planning: init_fp, ioPlacer, pdn and tapcell
• Placement: RePLace (Global), Resizer and OpenPhySyn (formerly), and OpenDP (Detailed)
• Clock Tree Synthesis: TritonCTS
• Fill Insertion: OpenDP/filler_placement
• Routing: FastRoute or CU-GR (formerly) and TritonRoute (Detailed) or DR-CU
• SPEF Extraction: OpenRCX or SPEF-Extractor (formerly)
• GDSII Streaming out: Magic and KLayout
• DRC Checks: Magic and KLayout
• LVS check: Netgen
• Antenna Checks: Magic
• Circuit Validity Checker: CVC

Everything in Floorplanning through Routing is done using OpenROAD and its various sub-utilities.

OpenLane Output

All output run data is placed by default under ./designs/design_name/runs. Each flow cycle will output a timestamp-marked folder containing the following file structure:

<design_name>
├── config.json/config.tcl
├── runs
│   ├── <tag>
│   │   ├── config.tcl
│   │   ├── {logs, reports, tmp}
│   │   │   ├── cts
│   │   │   ├── signoff
│   │   │   ├── floorplan
│   │   │   ├── placement
│   │   │   ├── routing
│   │   │   └── synthesis
│   │   ├── results
│   │   │   ├── final
│   │   │   ├── cts
│   │   │   ├── signoff
│   │   │   ├── floorplan
│   │   │   ├── placement
│   │   │   ├── routing
│   │   │   └── synthesis

To delete all generated runs under all designs: make clean_runs