cocotb verilator code coverage support

Could you add verilator coverage support in the following file:

cocotb/share/lib/verilator/verilator.cpp

diff --git a/cocotb/share/lib/verilator/verilator.cpp b/cocotb/share/lib/verilator/verilator.cpp
index aff06d9..fc43374 100644
--- a/cocotb/share/lib/verilator/verilator.cpp
+++ b/cocotb/share/lib/verilator/verilator.cpp
@@ -84,5 +84,9 @@ int main(int argc, char** argv) {
     tfp->close();
 #endif
 
+#if VM_COVERAGE
+    VerilatedCov::write("coverage.dat");
+#endif
+
     return 0;
 }

[sammy17]

I noticed that even when I enable verilator code coverage with EXTRA_ARGS= --coverage, coverage.dat file is not getting generated even with the above fix (as mentioned in https://github.com/cocotb/cocotb/issues/2573#issuecomment-865454544).

After a quick debug I noticed that anything after vl_finish(__FILE__, __LINE__, ""); in cocotb/share/lib/verilator/verilator.cpp is not getting executed. So VerilatedCov::write("coverage.dat"); that was added for this issue never got executed and coverage.dat file was not dumped.

I was able to get the coverage file to be dumped by moving the VerilatedCov::write call right before vl_finish as below.

        // If there are no more cbAfterDelay callbacks,
        // the next deadline is max value, so end the simulation now
        if (next_time == static_cast<vluint64_t>(~0ULL)) {
#if VM_COVERAGE
            VerilatedCov::write("coverage.dat");
#endif
            vl_finish(__FILE__, __LINE__, "");
            break;
        } else {
            main_time = next_time;
        }

[lavanyajagan]

https://github.com/cocotb/cocotb/pull/1479

Hope this is sufficient. Thanks