============================================================== Guild: wafer.space Community Channel: ๐Ÿ—๏ธ - Designing / project-template / Yosys Issue After: 04/30/2026 23:59 ============================================================== [05/27/2026 20:17] mole99 [05/27/2026 20:17] mole99 Dang, this really is an issue in Yosys then. After updating Yosys to 0.64 I saw similar issues in the LibreLane CI: https://github.com/librelane/librelane/pull/916 I dismissed them for now and didn't merge, hoping that the recent 0.65 release would rectify things, but it doesn't. If you are able to create a Yosys-only reproducible, you could submit an issue upstream. If not, I'll try to create one tomorrow or simply explain the issue, perhaps someone has an idea what's going on. {Embed} https://github.com/librelane/librelane/pull/916 chore: update nix-eda to 6.16.0 by mole99 ยท Pull Request #916 ยท l... Updated nix-eda to 6.16.0 Updated Magic to 8.3.635 Updated Netgen to 1.5.318 Updated Yosys to 0.64 Updated yosys-eqy 0.64 Updated yosys-sby 0.64 Updated yosys-slang to 2026-03-25 Removed yosys-li... 2026-05_media/916-89463 [05/27/2026 20:17] mole99 Changed the channel name: Yosys Issue [05/27/2026 20:18] rebelmike The yosys version that the build is using is 0.64: ` Yosys 0.64 (git sha1 d8dab5b32666564eca8e18f412973853ce006e61, clang++ 21.1.2 -fPIC -O3)` [05/27/2026 20:18] rebelmike Or did you try it with 0.65 and that didn't fix it? [05/27/2026 20:21] mole99 I tried 0.65 with the LibreLane CI: https://github.com/fossi-foundation/nix-eda/pull/69 {Reactions} ๐Ÿ‘ [05/27/2026 20:22] mole99 I could also update the wafer.space branch to nix-eda with Yosys 0.65, but it probably wouldn't help :) [05/27/2026 20:24] rebelmike Fair enough, I guess we need to roll back to 0.63 until it is fixed, and work out how to report the issue. In config.yaml if I set the DESIGN_NAME to `uart_tx` and remove chip_top and chip_core I still get the issue, so that is getting towards a small repro. But I'm not quite sure how to then wrap that up into something I can report to yosys [05/27/2026 20:30] mole99 Yes, I'll try overriding the Yosys version with 0.63 in the project template for now. I think LibreLane should be able to create a standalone reproducible, as it does for OpenROAD. Maybe pyosys complicates things, but we'll see. The easiest way would be to write a small Yosys script that reads the Verilog and reproduces the issue, but I'm not sure it will be that easy :) [05/27/2026 20:32] mole99 In any case, thanks Mike, for giving this a try and identifying the issue! [05/27/2026 20:34] rebelmike Ah - this may not be so hard to repro ๐Ÿ˜„ ``` yosys> read_verilog src/uart_tx.v 1. Executing Verilog-2005 frontend: src/uart_tx.v Parsing Verilog input from `src/uart_tx.v' to AST representation. Generating RTLIL representation for module `\uart_tx'. Successfully finished Verilog frontend. yosys> check 2. Executing CHECK pass (checking for obvious problems). Checking module uart_tx... Warning: Wire uart_tx.\next_fsm_state$func$src/uart_tx.v:128$1.tx_en is used but has no driver. Warning: Wire uart_tx.\next_fsm_state$func$src/uart_tx.v:128$1.$result [3] is used but has no driver. Warning: Wire uart_tx.\next_fsm_state$func$src/uart_tx.v:128$1.$result [2] is used but has no driver. Warning: Wire uart_tx.\next_fsm_state$func$src/uart_tx.v:128$1.$result [1] is used but has no driver. Warning: Wire uart_tx.\next_fsm_state$func$src/uart_tx.v:128$1.$result [0] is used but has no driver. Found and reported 5 problems. ``` {Reactions} โค๏ธ [05/27/2026 20:38] rebelmike I'll raise a yosys issue [05/27/2026 20:40] mole99 Awesome! [05/27/2026 20:48] rebelmike https://github.com/YosysHQ/yosys/issues/5911 {Embed} https://github.com/YosysHQ/yosys/issues/5911 Check command fails with undriven nets ยท Issue #5911 ยท YosysHQ/yosys Version Yosys 0.64 (git sha1 d8dab5b, clang++ 21.1.2 -fPIC -O3) On which OS did this happen? Linux Reproduction Steps Run yosys, read and check the verilog: yosys> read_verilog src/uart_tx.v yos... [05/27/2026 20:51] rebelmike I tried to help them isolate by grabbing a couple of OSS CAD suite builds, it was present in a 0.63+ build, but not a 0.62+ (but I think OSS CAD suite might build off the dev branch so possibly the release 0.63 is ok) {Reactions} ๐Ÿ‘ [05/28/2026 06:31] mole99 I've pushed an update to the project template that overrides Yosys with version 0.62: https://github.com/wafer-space/gf180mcu-project-template/pull/60/changes/9f23d7e3dad93aba1b9c8d15c748cc486014628a However, before merging the PR I hope that the issue will be fixed upstream. [05/28/2026 07:04] mole99 Well, something else fails with this older version. So we might just have to wait for a fix :) {Reactions} ๐Ÿ˜ž [05/28/2026 19:04] 246tnt @Leo Moser (mole99) I see you got CI working on the PR now ? [05/28/2026 19:13] mole99 Yeah, it was already working before since the template does not trigger the regression in Yosys. When I backported Yosys to 0.62 something else broke, so I dropped that commit and am now waiting on a proper fix. [05/28/2026 19:55] rebelmike Yosys 0.63 looks to be working for me - that might be worth a try [05/28/2026 20:05] 246tnt @RebelMike Which versions of oss cad did you try that was 0.63+? [05/28/2026 20:07] rebelmike 20260331 [05/28/2026 20:13] rebelmike Ah hah, 20260307 fails [05/28/2026 20:14] rebelmike So regression very early in dev after 0.63 release [05/28/2026 20:17] 246tnt What's the reported hash ? [05/28/2026 20:22] rebelmike Yosys 0.63+87 (git sha1 2f1cdc2df, clang++ 18.1.8 -fPIC -O3) [05/28/2026 20:23] 246tnt ``` commit e9442194f27140e3e80cb3bf407c3259d562c449 Author: likeamahoney Date: Fri Feb 27 20:42:40 2026 +0300 support automatic lifetime qualifier on procedural variables ``` [05/28/2026 20:23] 246tnt this sounds like a possible culprit ? [05/28/2026 20:35] 246tnt ``` 0.62+119 04113eb95 bad 20260304 0.62+117 1d3f9b790 works 20260302 ``` {Reactions} ๐Ÿ‘€ [05/28/2026 21:03] 246tnt @Leo Moser (mole99) You coul dtry reverting that [05/28/2026 21:55] 246tnt Confirmed. I reverted this on `master` and that fixed the issue. [05/28/2026 22:20] rebelmike Thank you! Hopefully Leo can confirm if reverting that fixes the various other failures that Librelane CI picked up: https://github.com/librelane/librelane/actions/runs/26505823629 {Embed} https://github.com/librelane/librelane/actions/runs/26505823629 chore: update nix-eda ยท librelane/librelane@3dec125 ASIC implementation flow infrastructure, successor to OpenLane - chore: update nix-eda ยท librelane/librelane@3dec125 [05/29/2026 06:43] mole99 Thanks for pinpointing the faulty commit! [05/29/2026 06:44] mole99 Let's see if this works: - https://github.com/fossi-foundation/nix-eda/pull/70 - https://github.com/librelane/librelane/pull/916 I also noticed a slight fmax regression as well, so I'll have to adjust the target frequency for some designs. But what can you do... [05/29/2026 07:12] 246tnt Not done yet, but looking so far ... [05/29/2026 08:31] mole99 It seems that does the trick. Had to fix `CLOCK_PERIOD` slightly for two designs. `full_chip_sky130` now has issues which are likely due to a magic update, but I think those are valid issues. Looking into it. [05/29/2026 08:41] mole99 If this runs through I can properly rebase everything and finally update nix-eda in LibreLane again. https://github.com/librelane/librelane/pull/916/changes/d867039ca70d301a784f5b65e206076372d635b0 [05/29/2026 08:44] mole99 The issue with `full_chip_sky130` was in the power ports. The sky130 pads have a separate port for the bondpad. But LibreLane would short all of the global connections for it. Until now I somehow managed to convince magic to short them during extraction as well. Not sure if this was actually buggy behavior or not? With a recent magic update this does not work anymore, so I've properly implemented power/ground busses in LibreLane. [05/29/2026 08:45] mole99 {Attachments} 2026-05_media/message-B818F.txt [05/29/2026 08:45] mole99 LVS now looks like this. Instead of a single `VCCD_PAD` there is now `VCCD_PAD[0]` and `VCCD_PAD[1]`, as it should be. [05/29/2026 11:25] mole99 Merged, and I've updated the template: https://github.com/wafer-space/gf180mcu-project-template/pull/60 ============================================================== Exported 41 message(s) ==============================================================