<tnt>
Because in both cases the logic implemented is the same I know that for sure.
<tnt>
But I want to find where the synthisis screwed up and used more LUTs than it should.
<tnt>
LEC will tell me : yeah both circuit implement the same logic ... which is of no help to me. I need it to tell me "there is 2 LUT4s between those two FF in that circuit and only 1 LUT4 in that other circuit".
<killjoy>
Conformal LEC had a comparitive viewer you could see those differences with. Yes, it would tell you the circuits were equivalent, but you could also just browse things.
<mwk>
hm, some structural equivalence thing *would* be useful in yosys; I've often wanted this for test purposes to assert that something got synthesized in a particular way and not just an an equivalent way
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<mwk>
eg. writing testcases for IO buffer insertion is currently non-trivial and involves a lot of select -assert-count calls instead of a single "check these two circuits are equivalent" call
<tnt>
mwk: yeah, that's pretty much exactly what I want to do :) I also need to get better at the select syntax to make show more useful and filter just what I want to see.
<killjoy>
I'm trying to remember how this thing went.
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<killjoy>
I remember opening a menu and selecting a cell from one of the designs, then it would open a new window with a split down the middle, where design A would be on the left and design B would be on the right. The cell/module I had selected would be shown as a box with it's IO's on both sides. Conformal was pretty good at trying not to overwhelm you right away, which is very easy to do when looking at a
<killjoy>
schematic of a netlist. You could then select a pin and say "open fan-in/fan-out" and it would open it up until it hit the next module boundary.
<killjoy>
If you wanted to open the module you selected you just had to double-click it and it would expand it out and show you everything inside.
<killjoy>
The issue was always trying to poke around without the design blowing up in your face and bogging your machine and ram down.
<killjoy>
Also overwhelming you with massive amounts of gates.
<killjoy>
It would be awesome if something like this existed in the FOSS world, I don't think it does though.
<killjoy>
This comparative schematic viewer was used by Conformal to highlight differences between design A and design B, because it would attempt to only show you the parts of the schematics that didn't match up on each side, but you could just browse around in it too.
<killjoy>
I remember the first time seeing it was because the design engineer had accidentally instantiated a new module in a ddr4 controller and forgot to hook up the dft pins and left them hanging, so I was getting non-equivalencies in LEC from the RTL to the synthesized netlist.