Friday, 2019-11-29

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somlodaveshah: if I use yosys at #9e4801cca7, my point-to-point wide axi rocket-litedram setup works fine; as soon as I move to the immediately adjacent #ca99b1ee8dc, linux hangs on boot14:25
somloit's only the point-to-point AXI based design that exhibits the problem, and it doesn't look like stochasticity of p&r has anything to do with it (happens pretty predictably)14:26
somloout of desperation at how little sense this makes, I'm building the latest yosys (#419ca5c2) with #ca99b1ee reverted, to see what happens14:27
daveshahThe only change I can see in that PR is some new idstrings, which might have a small stochastic impact on synthesis14:28
somlomaybe we're tickling a migen, or litex/axi bug that somehow didn't manifest earlier?14:29
daveshahIf you try changing an identifier name somewhere, that should have a similar permutation effect14:33
daveshahSeems unlikely, more likely an issue on the Yosys or nextpnr side14:33
somlook, let's see what happens when I build with #419ca5c2 and reverted #ca99b1ee (should be up to another hour or so -- as I mentioned yesterday, later yosys commits take much longer to build litex/rocket on the trellisboard)14:37
somloand that's out of a sample of two (both times I tried it over the last two-three days, it took a LOOONG time to p&r the output of latest yosys)14:38
somlook, yosys done compiling, now running litex build15:00
somlodaveshah: reverting #ca99b1ee on top of current master (#419ca5c2) got me a working design15:33
somlonow, to be 100% sure, I'm building #419ca5c2 without the revert, to rule out some other interaction effects15:34
somlowould it make sense to diff the yosys json output with vs. without the "offending" commit ?15:36
daveshahI expect it would be too chaotic to diff in any meaningful way15:40
daveshahBut you could have a look at the ilang after `proc`15:40
daveshahthat is the point where that commit stops having any impact - so if the rtlil is the same after `proc` with and without the commit then it is some other stochastic impact of the commit rather than a bug in or triggered directly by the commit15:41
somloseems without the revert, yosys-master generated json once again takes very long to p&r17:14
somlospecifically, *route* (placement takes about the same as it ever has)17:15
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