1 files changed, 136 insertions, 0 deletions
diff --git a/VexRiscv/src/main/scala/vexriscv/plugin/VfuPlugin.scala b/VexRiscv/src/main/scala/vexriscv/plugin/VfuPlugin.scala
new file mode 100644
index 0000000..a2c0930
--- /dev/null
+++ b/VexRiscv/src/main/scala/vexriscv/plugin/VfuPlugin.scala
@@ -0,0 +1,136 @@
+package vexriscv.plugin
+
+import vexriscv.{DecoderService, ExceptionCause, ExceptionService, Stage, Stageable, VexRiscv}
+import spinal.core._
+import spinal.lib._
+import spinal.lib.bus.bmb.WeakConnector
+import spinal.lib.bus.misc.{AddressMapping, DefaultMapping}
+import vexriscv.Riscv.IMM
+
+
+object VfuPlugin{
+  val ROUND_MODE_WIDTH = 3
+
+}
+
+
+case class VfuParameter() //Empty for now
+
+case class VfuCmd( p : VfuParameter ) extends Bundle{
+  val instruction = Bits(32 bits)
+  val inputs = Vec(Bits(32 bits), 2)
+  val rounding = Bits(VfuPlugin.ROUND_MODE_WIDTH bits)
+}
+
+case class VfuRsp(p : VfuParameter) extends Bundle{
+  val output = Bits(32 bits)
+}
+
+case class VfuBus(p : VfuParameter) extends Bundle with IMasterSlave{
+  val cmd = Stream(VfuCmd(p))
+  val rsp = Stream(VfuRsp(p))
+
+  def <<(m : VfuBus) : Unit = {
+    val s = this
+    s.cmd << m.cmd
+    m.rsp << s.rsp
+  }
+
+  override def asMaster(): Unit = {
+    master(cmd)
+    slave(rsp)
+  }
+}
+
+
+
+class VfuPlugin(val stageCount : Int,
+                val allowZeroLatency : Boolean,
+                val parameter : VfuParameter) extends Plugin[VexRiscv]{
+  def p = parameter
+  
+  var bus : VfuBus = null
+
+  lazy val forkStage = pipeline.execute
+  lazy val joinStage = pipeline.stages(Math.min(pipeline.stages.length - 1, pipeline.indexOf(forkStage) + stageCount))
+
+
+  object VFU_ENABLE extends Stageable(Bool())
+  object VFU_IN_FLIGHT extends Stageable(Bool())
+
+  override def setup(pipeline: VexRiscv): Unit = {
+    import pipeline._
+    import pipeline.config._
+
+    bus = master(VfuBus(p))
+
+    val decoderService = pipeline.service(classOf[DecoderService])
+    decoderService.addDefault(VFU_ENABLE, False)
+
+    decoderService.add(
+      key = M"-------------------------0001011",
+      values = List(
+        VFU_ENABLE -> True,
+        REGFILE_WRITE_VALID      -> True, //If you want to write something back into the integer register file
+        BYPASSABLE_EXECUTE_STAGE -> Bool(stageCount == 0),
+        BYPASSABLE_MEMORY_STAGE  -> Bool(stageCount <= 1),
+        RS1_USE -> True,
+        RS2_USE -> True
+      )
+    )
+  }
+
+  override def build(pipeline: VexRiscv): Unit = {
+    import pipeline._
+    import pipeline.config._
+
+    val csr = pipeline plug new Area{
+      val factory = pipeline.service(classOf[CsrInterface])
+      val rounding = Reg(Bits(VfuPlugin.ROUND_MODE_WIDTH bits))
+
+      factory.rw(csrAddress = 0xBC0, bitOffset = 0, that = rounding)
+    }
+
+
+    forkStage plug new Area{
+      import forkStage._
+      val hazard = stages.dropWhile(_ != forkStage).tail.map(s => s.arbitration.isValid && s.input(HAS_SIDE_EFFECT)).orR
+      val scheduleWish = arbitration.isValid && input(VFU_ENABLE)
+      val schedule = scheduleWish && !hazard
+      arbitration.haltItself setWhen(scheduleWish && hazard)
+
+      val hold = RegInit(False) setWhen(schedule) clearWhen(bus.cmd.ready)
+      val fired = RegInit(False) setWhen(bus.cmd.fire) clearWhen(!arbitration.isStuck)
+      insert(VFU_IN_FLIGHT) := schedule || hold || fired
+
+      bus.cmd.valid := (schedule || hold) && !fired
+      arbitration.haltItself setWhen(bus.cmd.valid && !bus.cmd.ready)
+
+      bus.cmd.instruction := input(INSTRUCTION)
+      bus.cmd.inputs(0) := input(RS1)
+      bus.cmd.inputs(1) := input(RS2)
+      bus.cmd.rounding := csr.rounding
+    }
+
+    joinStage plug new Area{
+      import joinStage._
+
+      val rsp = if(forkStage != joinStage && allowZeroLatency) {
+        bus.rsp.s2mPipe()
+      } else {
+        bus.rsp.combStage()
+      }
+
+      rsp.ready := False
+      when(input(VFU_IN_FLIGHT) && input(REGFILE_WRITE_VALID)){
+        arbitration.haltItself setWhen(!bus.rsp.valid)
+        rsp.ready := !arbitration.isStuckByOthers
+        output(REGFILE_WRITE_DATA) := bus.rsp.output
+      }
+    }
+
+    pipeline.stages.drop(1).foreach(s => s.output(VFU_IN_FLIGHT) clearWhen(s.arbitration.isStuck))
+    addPrePopTask(() => stages.dropWhile(_ != memory).reverse.dropWhile(_ != joinStage).foreach(s => s.input(VFU_IN_FLIGHT).init(False)))
+  }
+}
+