How to get slang in yosys

[MoonbaseOtago]

I'm working from the current tip of tree, I have some complex System Verilog and need slang. It doesn't seem to be there - it's a shared library that should be in tools/install/yosys/share/yosys/plugins/slang.so

$ yosys -m slang -p "slang_version"

 /----------------------------------------------------------------------------\
 |  yosys -- Yosys Open SYnthesis Suite                                       |
 |  Copyright (C) 2012 - 2026  Claire Xenia Wolf <claire@yosyshq.com>         |
 |  Distributed under an ISC-like license, type "license" to see terms        |
 \----------------------------------------------------------------------------/
 Yosys 0.68+post (git sha1 UNKNOWN, Release, GNU /usr/local/bin/wrapped-cc/g++ 11.4.0)
ERROR: Can't load module `./slang': /OpenROAD-flow-scripts/tools/install/yosys/bin/../share/yosys/plugins/slang.so: cannot open shared object file: No such file or directory

I tried building it using build_openroad.sh and it did seem to build (several) slangs - but the shared library didn't show up either

Anyone got any suggestions?

[abozaralizadeh]

I think you already have it. There's just no slang.so anymore.

From Yosys 0.67 on, slang is built into Yosys itself instead of being a plugin. ORFS's own synth script says so and calls read_slang without loading anything (synth_preamble.tcl#L97-L98):

# read_slang is built into Yosys (>=0.67); no plugin load needed.

Your build is 0.68, so -m slang fails only because it looks for a plugin file that doesn't exist. Try it without the -m:

yosys -p "help read_slang"

If that prints the help, you're good. For the flow itself, just set SYNTH_HDL_FRONTEND=slang in your design config (FlowVariables), and SYNTH_SLANG_ARGS if you need extra flags.

The yosys -m slang -p "slang_version" line in the install docs (BuildLocally.md) looks like it's from before the change, which is probably what sent you looking for the .so.

[abozaralizadeh]

@MoonbaseOtago yes the docs are a bit behind on that, easy to get confused. if it works now, you can click "Mark as answer" on it so the next person finds it quick.

[MoonbaseOtago]

Ah, thanks! all the docs say to use "yosys -m slang -p "slang_version"" to verify your build so I'd assumed that was my issue