[Libre-soc-dev] Coloquinte legalizer failure
Luke Kenneth Casson Leighton
lkcl at lkcl.net
Fri Dec 4 19:18:09 GMT 2020
On Fri, Dec 4, 2020 at 5:58 PM Jean-Paul Chaput
<Jean-Paul.Chaput at lip6.fr> wrote:
> This error usually happens when the placer has "too much cells
> too wide" to place in "too narrow a space". The area is good,
> but as it obviously can "cut" cells in two, if they are too
> big it cannot place. Typical case is when there is too much
> DFFs. As I don't see that effect either I wonder if you are
> not in the case where a SRAM was synthetized by Yosys as a
> big bunch of flip-flops...
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.
this in turn causes cascading overload of abc which i talked to the
developer of abc about, and we realised that what yosys was trying to
do was just... mental.
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.
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