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KLayout as an Optional Dependency

KLayout is only required for GDS/OAS stream generation, DRC, and LVS verification. All other ORFS functionality — synthesis, floorplanning, placement, CTS, routing, timing reports, and abstract generation — works without KLayout installed.

Makefile Targets

Target Requires KLayout Description
make finish Yes Complete flow including GDS generation
make gds Yes Generate GDS/OAS from finished design
make drc Yes Run DRC checks (requires GDS)
make lvs Yes Run LVS checks (requires GDS)
make gallery Yes Generate layout screenshots
make klayout_<file> Yes Open result in KLayout viewer
make generate_abstract No Generate LEF/LIB abstracts

A check-klayout guard produces a clear error message when KLayout is missing and a KLayout-dependent target is invoked:

Error: KLayout not found. Install KLayout or set KLAYOUT_CMD.
Hint: KLayout is needed for GDS/DRC/LVS targets.

bazel-orfs Integration

bazel-orfs uses the do- prefixed targets which bypass Make's dependency management. The relevant targets follow the standard pattern:

  • do-finish / do-final — runs the finish stage without GDS
  • do-gds — runs GDS generation (requires KLayout)

An orfs_gds() Bazel rule can call do-gds independently from orfs_flow(), making KLayout an optional toolchain dependency configured in MODULE.bazel.

KLayout Tech File Generation

The do-klayout and do-klayout_wrap targets generate .lyt technology files by substituting LEF and map file paths into platform templates. This is implemented in util/generate_klayout_tech.py using stdlib XML processing — no KLayout dependency required.

Testing Without KLayout

Unit tests for all KLayout-related Python scripts use unittest.mock to mock the pya API:

cd flow/test
python -m unittest test_generate_klayout_tech test_def2stream test_convertDrc

These tests cover:

  • .lyt tech file generation (test_generate_klayout_tech.py)
  • DEF-to-GDS merging logic (test_def2stream.py)
  • DRC report conversion (test_convertDrc.py)

Future: OpenROAD write_gds and KLayout Coexistence

OpenROAD has an unfinished write_gds command. When it is eventually completed, it would eliminate the KLayout dependency for GDS generation in many cases. However, KLayout support will live alongside write_gds until there is confidence that write_gds is robust and fully covers all current use cases.

Even then, non-public or future PDKs may have requirements that benefit from KLayout's mature GDS handling. Whether KLayout support stays in ORFS indefinitely remains to be seen. Once write_gds works robustly for all of today's use cases, extending it to cover future ones may turn out to be straightforward.