VCDHackedEphemeralSimulator.scala

// Hacked from https://github.com/chipsalliance/chisel/blob/v6.5.0/src/main/scala/chisel3/simulator/EphemeralSimulator.scala
// Very frustratingly, svsim in Chisel 6+ doesn't include support for VCD-dumping by default.
// See https://github.com/chipsalliance/chisel/discussions/3957

package chisel3.simulator

import svsim._
import chisel3.RawModule
import java.nio.file.Files
import java.io.File
import scala.reflect.io.Directory

/** Provides a simple API for "ephemeral" invocations (where you don't care about the artifacts after the invocation completes) to
  * simulate Chisel modules. To keep things really simple, `EphemeralSimulator` simulations can only be controlled using the
  * peek/poke API, which provides enough control while hiding some of the lower-level svsim complexity.
  * @example
  * {{{
  * import chisel3.simulator.EphemeralSimulator._
  * ...
  * simulate(new MyChiselModule()) { module => ... }
  * }}}
  */
object VCDHackedEphemeralSimulator extends PeekPokeAPI {

  def simulate[T <: RawModule](
    module: => T
  )(body:   (T) => Unit
  ): Unit = {
    makeSimulator
      .simulate(module)({ module =>
        // HACK enable tracing
        module.controller.setTraceEnabled(true)
        body(module.wrapped)
      })
      .result
  }

  private class DefaultSimulator(val workspacePath: String) extends SingleBackendSimulator[verilator.Backend] {
    val backend = verilator.Backend.initializeFromProcessEnvironment()
    val tag = "default"
    val commonCompilationSettings = CommonCompilationSettings()
    // HACK to enable VCD dumping
    val backendSpecificCompilationSettings = verilator.Backend.CompilationSettings(
      traceStyle = Some(verilator.Backend.CompilationSettings.TraceStyle.Vcd(traceUnderscore = true))
    )

    // HACK don't delete temporary workspace to keep VCD
    // Try to clean up temporary workspace if possible
    sys.addShutdownHook {
      //(new Directory(new File(workspacePath))).deleteRecursively()
    }
  }
  private def makeSimulator: DefaultSimulator = {
    // TODO: Use ProcessHandle when we can drop Java 8 support
    // val id = ProcessHandle.current().pid().toString()
    val id = java.lang.management.ManagementFactory.getRuntimeMXBean().getName()
    val className = getClass().getName().stripSuffix("$")
    // HACK: use $PWD/test_run_dir like in old versions of Chisel
    //new DefaultSimulator(Files.createTempDirectory(s"${className}_${id}_").toString)
    new DefaultSimulator(
      Files.createDirectories(java.nio.file.Paths.get(s"test_run_dir/${className}_${id}_")).toAbsolutePath.toString
    )
  }
}