[Bug,TestFW] Zicntr in CoSim not compliant with the standard

[ZhongYic00]

Observed Behavior

I encountered some cosim mismatches around operations on CSR instret (user mode delegate of minstret), which is not (planned to be) implemented (according to #1973 ).

FAILURE: Co-simulation mismatch at time                   36
PC mismatch, DUT retired : 100000 , but the ISS retired: 100008
[36] %Error: ibex_simple_system_cosim_checker.sv:74: Assertion failed in TOP.ibex_simple_system.u_ibex_simple_system_cosim_checker_bind: Co-simulation mismatch seen
Received stop request, shutting down simulation.

trace_core_00000000.log:

Time    Cycle   PC      Insn    Decoded instruction     Register and memory contents
             30         11      00100004        c0206073        csrrsi  x0,instret,0      x0=0x00000000
=> trap IllegalInsn here
             36         14      00100000        0670    c.addi4spn      x12,x2,780       x12=0x0000030c

Expected Behavior

As the project has not yet planned to impl Zicntr, spike used as reference model should be aligned.
Currently the fork lowrisc/riscv-isa-sim is far behind the upstream. While the upstream has made Zicntr optional regarding the ISA string, there exists a fragment in the fork that always enable Zicntr:

riscv/isa_parser.cc:L37
// enable zicntr and zihpm unconditionally for backward compatibility
  extension_table[EXT_ZICNTR] = true;

Steps to reproduce the issue

1. Build lowrisc:ibex:ibex_simple_system_cosim
2. Run Cosim with the provided testcase binary (which may need conversion? bin is not officially supported, I run with my modified simulating c++ code) build/lowrisc_ibex_ibex_simple_system_cosim_0/sim-verilator/Vibex_simple_system -c 10000 --meminit=ram,errors/ba8335cdf5815390859b835ec904d458
3. Mismatch reported

ibex_zicntr_unimpl.zip

My Environment

EDA tool and version:

Verilator 5.006 2023-01-22 rev (Debian 5.006-3)

Operating system:

Version of the Ibex source code:

master (commit 587e9fe)