Update ALU MULT mode in gowin to match nextpnr #4827
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I don't see I2 mentioned in the apicula docs for the ALU primitive, could you explain where I can take a look to see how this affects the function? |
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@widlarizer the documentation I was referring to is this. The first table describes connections in different ALU modes. The |
widlarizer
approved these changes
Jan 9, 2025
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nextpnrcurrently wires an ALU inMULTmode in a different fashion than expected. Instead ofI2toGND, it is connected toVCC. This has been mentioned in YosysHQ/nextpnr#1407. While fixing this innextpnrwould work, leaving it as-is is arguably a better option, since it can perform the same operations plus being able to take a second operand. This would have a profound impact if choosing to synthesize multiplication using this mode.So, instead of fixing the wiring in
nextpnr, this PR seeks to update the expected behavior of the cell to reflect the current wiring.yosysdoesn't use this mode yet, and therefore no tests or workflows should be impacted.