Modelsim Design Optimization Error Seen In Simulating FlooNoC

[HamasWaqar]

Hi,

I am currently working on simulating floo_nw_mesh_noc.sv and floo_axi_mesh_noc.sv, which were generated using the FlooNoC script. To verify them, I am using the corresponding testbenches tb_floo_nw_mesh.sv and tb_floo_axi_mesh.sv on ModelSim SE 10-7c. However, I’ve encountered the following error during the simulation:

# Start time: 00:44:29 on Dec 04,2024
# ** Note: (vsim-3812) Design is being optimized...
# ** Error: /autofs/fs1.ece/fs1.eecg.janders/waqarha4/Documents/reseach/NoC_CGRA/floo/floo/flooNOC/.bender/git/checkouts/common_cells-ef73fb619e9c374f/src/id_queue.sv(420): Questa has encountered an unexpected internal error: ../../src/vlog/vgentd.c(607). Please contact Questa support at http://supportnet.mentor.com/
# ** Error: (vopt-2064) Compiler back-end code generation process terminated with code 2.

From my investigation, it appears the error might be caused by the failure of the QuestaSim optimizer. This could be due to complex generated blocks, unsupported SystemVerilog constraints, or deeply nested logic in either the testbench or design files.

I was wondering if there is a dependency on the ModelSim version for simulating FlooNoC that could explain this issue? Additionally, do you have any recommendations or solutions to address this error?

Please let me know if you need any more information. Thanks in advance for your help.

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Update:

I’ve been investigating the issue further to identify its root cause. I successfully simulated the following test benches along with their respective design files in ModelSim SE 10-7c:

• tb_floo_router.sv
• tb_floo_nw_chimney.sv
• tb_floo_axi_chimney.sv

This leads me to believe that the error might be specifically tied to either floo_nw_mesh_noc.sv or floo_axi_mesh_noc.sv and their corresponding testbenches (tb_floo_nw_mesh.sv and tb_floo_axi_mesh.sv).

[fischeti]

I don't have an exact answer which versions of QuestaSim are supported unfortunately. But the mentioned testbenches are also tested in the CI, but with a newer version of QuestaSim (see here). My guess is that this is a version issue, so my first recommendation would be to update the Modelsim/QuestaSim if that is a possibility for you.

Otherwise, you can also try to turn of any optimizations with -voptargs=+acc. Maybe that also helps.