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arroz | 2 years ago

TCL is still the language of choice for EDA

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IshKebab|2 years ago

Unfortunately. It's not too bad for interactive use (it's somewhere between Bash and Python in terms of sanity; maybe closer to Bash). The problem is people end up writing huge scripts and workflows all TCL which is just way beyond its wheelhouse. Often with a bit of Make and Bash thrown in to make it especially awful.

Sadly there is no end in sight because all of the proprietary tools use it and you can't really do anything about that.

They did add a bytecode runner in one version of TCL and I experimented with making a new language that would compile to TCL bytecode, but unfortunately one of our tools (PowerArtist I think) still bundled TCL from 2005 or so and didn't support it.

I also experimented with a WASM to TCL transpiler, and got it to work a little, but the WASM spec is actually quite big and the TCL code you get out is huge so I don't think that is the right way really.

The only good thing about TCL is that it's value based, not reference based. Value based languages are much more intuitive and easy to reason about, but unfortunately most languages are reference based.

djmips|2 years ago

Would you like to elaborate on the meaning of value based versus reference based?

inomenic|2 years ago

Wow, had no idea. Is there a rich ecosystem for this?

Is this on the level of R/tidyverse/ggplot?

lizknope|2 years ago

I have no idea what tidyverse or ggplot are.

The two dominate EDA companies are Cadence and Synopsys. All of the digital design tools for synthesis, place and route, and static timing analysis use the Tcl language as the built in scripting language. These tools have literally thousands of built in commands.

You can look up some of the tools like Cadence Innovus that I use every day. A single license has a list price of over $1 million. We get big discounts because we have about 800 licenses.

https://www.cadence.com/en_US/home/tools/digital-design-and-... Then you write more Tcl code to script things within the tool. A standard thing is building a power grid. You need to write a for loop to build a metal 1 stripe every 5 microns. That's done in Tcl.

You have a list of clocks you need to define with names and frequencies. Use a Tcl array and a for loop.

Our CAD flow is literally tens of thousands of lines of Tcl code to take Verilog and go through all the steps until we get a GDS file with mask data to manufacture.

rhelz|2 years ago

The "ecosystem" would just be, e.g. the suite of ASIC place and route tools, or FPGA synthesis tools, provided by each company. They pretty much all have TCL built in, for to help script them all together.

Each individual script is typically very ad-hoc, to address a specific shortcoming in a tool, or to get a particular mix-and-match of tools from various vendors integrated into a design pipeline.

That being said, it is an ancient and venerable tradition, dating back to the creation of tcl itself, and as long as we're making chip from Silicon it will be the duct tape holding it all together.

tn1|2 years ago

Not really. Most of the tcl that gets written is very straightforward and business-logic. The framework you're using is pretty much just the host tool. Trying to integrate other libraries is often difficult if the tcl runtime is missing some features (looking at you, xilinx...)

sweetjuly|2 years ago

There really isn't an ecosystem. It's mostly just used for driving the tools and describing the configuration. For example, if you needed to generate power straps for an ASIC, you'd add a line to your place-and-route tcl script to generate them.

xorcist|2 years ago

Some fifteen years ago I briefly worked with Cisco VoIP and the IVR was all Tcl scripted.

F5 BigIP load balancers has hooks in Tcl that control the balancing and can rewrite requests.

So there are niches for Tcl still. Nice language.