[verilator driver] Fix for clang (#8427)

Was failing on link due to Verilator trace library not being found. I
think this is because Verilator does not produce this library unless
tracing is enabled. Further, clang (by default) doesn't detect that the
symbols aren't actually needed (ie it doesn't optimize away the 'if'
branch) so it requires them.

Author: teqdruid

lib/Dialect/ESI/runtime/cosim_dpi_server/driver.cpp

@@ -63,7 +63,10 @@ int main(int argc, char **argv) {
               << std::endl;
   }
 
+#ifdef TRACE
   VerilatedVcdC *tfp = nullptr;
+#endif
+
   if (waveformFile) {
 #ifdef TRACE
     tfp = new VerilatedVcdC();
@@ -93,8 +96,10 @@ int main(int argc, char **argv) {
   for (timeStamp = 0; timeStamp < 8 && !Verilated::gotFinish(); timeStamp++) {
     dut.eval();
     dut.clk = !dut.clk;
+#ifdef TRACE
     if (tfp)
       tfp->dump(timeStamp);
+#endif
   }
 
   // Take simulation out of reset.
@@ -104,17 +109,22 @@ int main(int argc, char **argv) {
   for (; !Verilated::gotFinish() && !stopSimulation; timeStamp++) {
     dut.eval();
     dut.clk = !dut.clk;
+
+#ifdef TRACE
     if (tfp)
       tfp->dump(timeStamp);
+#endif
     if (debugPeriod)
       std::this_thread::sleep_for(std::chrono::milliseconds(debugPeriod));
   }
 
   // Tell the simulator that we're going to exit. This flushes the output(s) and
   // frees whatever memory may have been allocated.
   dut.final();
+#ifdef TRACE
   if (tfp)
     tfp->close();
+#endif
 
   std::cout << "[driver] Ending simulation at tick #" << timeStamp << std::endl;
   return 0;

tools/circt-rtl-sim/driver.cpp

@@ -53,7 +53,10 @@ int main(int argc, char **argv) {
   auto &dut = *new Vtop();
   char *waveformFile = getenv("SAVE_WAVE");
 
+#ifdef TRACE
   VerilatedVcdC *tfp = nullptr;
+#endif
+
   if (waveformFile) {
 #ifdef TRACE
     tfp = new VerilatedVcdC();
@@ -78,8 +81,10 @@ int main(int argc, char **argv) {
   for (timeStamp = 0; timeStamp < 8 && !Verilated::gotFinish(); timeStamp++) {
     dut.eval();
     dut.clk = !dut.clk;
+#ifdef TRACE
     if (tfp)
       tfp->dump(timeStamp);
+#endif
   }
 
   // Take simulation out of reset.
@@ -92,15 +97,19 @@ int main(int argc, char **argv) {
        timeStamp++) {
     dut.eval();
     dut.clk = !dut.clk;
+#ifdef TRACE
     if (tfp)
       tfp->dump(timeStamp);
+#endif
   }
 
   // Tell the simulator that we're going to exit. This flushes the output(s) and
   // frees whatever memory may have been allocated.
   dut.final();
+#ifdef TRACE
   if (tfp)
     tfp->close();
+#endif
 
   std::cout << "[driver] Ending simulation at tick #" << timeStamp << std::endl;
   return 0;