[Libre-soc-dev] Coloquinte legalizer failure

[Cole Poirier]

On Fri, Dec 4, 2020 at 11:18 AM Luke Kenneth Casson Leighton <lkcl at lkcl.net>
wrote:

>
> yes, this would seem to fit.  we know that there is a bug in yosys
> where SRAMs are turned into DFFs and try to read multi-megabytes of
> 0b000000 as initialisation.
>
> [snip]
>
> i honestly have no idea how to "solve" this, there must be some script
> modifications to the yosys "synth" command to get it to use ASIC cells
> but i just don't know what it is.
>

I'm not sure but I *think* that the right stage of yosys would be the
'techmap' command. From this page
https://symbiflow.readthedocs.io/en/latest/toolchain-desc/yosys.html (I
think it's accurate to yosys not specific to symbiflow) it should be
possible to write a custom rule for a standard pre-existing techmap 'rule',
or to write the rule for our specific technology/needs/requirements
ourselves. Is this the case? I'm not familiar enough with yosys to
interpret this reliably.

Cole