What does yosys -import do?

[xobs]

In the synthesis script, the flow runs yosys -import:

OpenLane/scripts/yosys/synth.tcl

Line 14 in cb634fd

yosys -import

However, this appears to be neither a valid yosys command, nor a valid yosys argument. What is this command and where does it come from?

[kareefardi]

@xobs Without it we can't use yosys builtin tcl commands, as far as I understand. From yosys docs

The tcl command 'yosys -import' can be used to import all yosys
commands directly as tcl commands to the tcl shell. Yosys commands
'proc' and 'rename' are wrapped to tcl commands 'procs' and 'renames'
in order to avoid a name collision with the built in commands.

[xobs]

I see, thank you.

Normally, I've used Yosys in interactive mode, and I've therefore used the custom Yosys script language.

OpenLane uses Yosys in tcl mode, which behaves slightly differently. Notably, commands aren't available by default as TCL verbs. The TCL function yosys -import re-imports all Yosys commands into TCL land.

This needs to be done any time additional verbs are added, such as when a plugin is loaded.

[kareefardi]

Yes. Thanks for better explaining it.