[difftest] print cycles at end of simulation

difftest/dpi_common/src/lib.rs

@@ -1,6 +1,7 @@
 pub mod dpi_target;
 pub mod dump;
 pub mod plusarg;
+pub mod util;
 
 pub use dpi_target::DpiTarget;
 

difftest/dpi_common/src/util.rs

@@ -0,0 +1,15 @@
+//! utility functions
+
+pub fn write_perf_json(cycle: u64) {
+  let mut content = String::new();
+  content += "{\n";
+  content += &format!("    \"total_cycles\": {cycle}\n");
+  content += "}\n";
+
+  match std::fs::write("perf.json", &content) {
+    Ok(()) => {}
+    Err(e) => {
+      tracing::error!("failed to write 'perf.json': {e}");
+    }
+  }
+}

difftest/dpi_t1/src/dpi.rs

@@ -229,6 +229,11 @@ unsafe extern "C" fn t1_cosim_init() {
   TARGET.init(|| Driver::new(scope, dump_control, &args));
 }
 
+#[no_mangle]
+unsafe extern "C" fn t1_cosim_final() {
+  dpi_common::util::write_perf_json(crate::get_t());
+}
+
 /// evaluate at every 1024 cycles, return reason = 0 to continue simulation,
 /// other value is used as error code.
 #[no_mangle]

difftest/dpi_t1/src/lib.rs

@@ -45,7 +45,8 @@ impl OnlineArgs {
 }
 
 // keep in sync with TestBench.ClockGen
-pub const CYCLE_PERIOD: u64 = 20;
+// the value is measured in simulation time unit
+pub const CYCLE_PERIOD: u64 = 20000;
 
 /// get cycle
 pub fn get_t() -> u64 {

difftest/dpi_t1rocket/src/dpi.rs

@@ -282,6 +282,11 @@ unsafe extern "C" fn t1rocket_cosim_init() {
   TARGET.init(|| Driver::new(scope, dump_control, &args));
 }
 
+#[no_mangle]
+unsafe extern "C" fn t1rocket_cosim_final() {
+  dpi_common::util::write_perf_json(crate::get_t());
+}
+
 /// evaluate at every 1024 cycles, return reason = 0 to continue simulation,
 /// other value is used as error code.
 #[no_mangle]

difftest/dpi_t1rocket/src/lib.rs

@@ -36,7 +36,8 @@ const EXIT_POS: u32 = 0x4000_0000;
 const EXIT_CODE: u32 = 0xdead_beef;
 
 // keep in sync with TestBench.ClockGen
-pub const CYCLE_PERIOD: u64 = 20;
+// the value is measured in simulation time unit
+pub const CYCLE_PERIOD: u64 = 20000;
 
 /// get cycle
 pub fn get_t() -> u64 {

ipemu/src/TestBench.scala

@@ -56,11 +56,15 @@ class TestBench(generator: SerializableModuleGenerator[T1, T1Parameter])
          |`endif
          |
          |  import "DPI-C" context function void t1_cosim_init();
+         |  import "DPI-C" context function void t1_cosim_final();
          |  initial begin
          |    t1_cosim_init();
          |    clock = 1'b0;
          |    reset = 1'b1;
          |  end
+         |  final begin
+         |    t1_cosim_final();
+         |  end
          |  initial #(11) reset = 1'b0;
          |  always #10 clock = ~clock;
          |endmodule

t1rocketemu/src/TestBench.scala

@@ -43,11 +43,16 @@ class TestBench(generator: SerializableModuleGenerator[T1RocketTile, T1RocketTil
          |  endfunction;
          |
          |  import "DPI-C" context function void t1rocket_cosim_init();
+         |  import "DPI-C" context function void t1rocket_cosim_final();
          |  initial begin
          |    t1rocket_cosim_init();
          |    clock = 1'b0;
          |    reset = 1'b1;
          |  end
+         |  final begin
+         |    t1rocket_cosim_final();
+         |  end
+         |
          |  initial #(100) reset = 1'b0;
          |  always #10 clock = ~clock;
          |endmodule