diplomacy: remove the :=? operator in favour of magic :*=* (#1139)

The reason for the :=? operator was for when you have an adapter chain
whose direction of cardinality you could not know. We used explicit
directives to tell these compositions which way to go.

Unfortunately, that makes the API leaky. You think the chain of adapters
is just one adapter, but you have to use strange Cardinality scopes to
use it. That's just bad.

The new :*=* just automagically figures it out from the graph.

src/main/scala/coreplex/CrossingWrapper.scala

@@ -55,7 +55,7 @@ trait HasCrossingMethods extends LazyModule with LazyScope
     lazy val asink = LazyModule(new TLAsyncCrossingSink(depth, sync))
     val source = if (out) this { asource } else asource
     val sink = if (out) asink else this { asink }
-    sink.node :=? source.node
+    sink.node :*=* source.node
     checks = CrossingCheck(out, source.node, sink.node) :: checks
     NodeHandle(source.node, sink.node)
   }
@@ -65,7 +65,7 @@ trait HasCrossingMethods extends LazyModule with LazyScope
     lazy val rsink = LazyModule(new TLRationalCrossingSink(if (out) direction else direction.flip))
     val source = if (out) this { rsource } else rsource
     val sink = if (out) rsink else this { rsink }
-    sink.node :=? source.node
+    sink.node :*=* source.node
     checks = CrossingCheck(out, source.node, sink.node) :: checks
     NodeHandle(source.node, sink.node)
   }
@@ -102,7 +102,7 @@ trait HasCrossingMethods extends LazyModule with LazyScope
     lazy val axi4asink = LazyModule(new AXI4AsyncCrossingSink(depth, sync))
     val source = if (out) this { axi4asource } else axi4asource
     val sink = if (out) axi4asink else this { axi4asink }
-    sink.node :=? source.node
+    sink.node :*=* source.node
     checks = CrossingCheck(out, source.node, sink.node) :: checks
     NodeHandle(source.node, sink.node)
   }
@@ -131,7 +131,7 @@ trait HasCrossingMethods extends LazyModule with LazyScope
     lazy val intssink = LazyModule(new IntSyncCrossingSink(0))
     val source = if (out) this { intssource } else intssource
     val sink = if (out) intssink else this { intssink }
-    sink.node :=? source.node
+    sink.node :*=* source.node
     checks = CrossingCheck(out, source.node, sink.node) :: checks
     NodeHandle(source.node, sink.node)
   }
@@ -141,7 +141,7 @@ trait HasCrossingMethods extends LazyModule with LazyScope
     lazy val intasink = LazyModule(new IntSyncCrossingSink(sync))
     val source = if (out) this { intasource } else intasource
     val sink = if (out) intasink else this { intasink }
-    sink.node :=? source.node
+    sink.node :*=* source.node
     checks = CrossingCheck(out, source.node, sink.node) :: checks
     NodeHandle(source.node, sink.node)
   }
@@ -151,7 +151,7 @@ trait HasCrossingMethods extends LazyModule with LazyScope
     lazy val intrsink = LazyModule(new IntSyncCrossingSink(1))
     val source = if (out) this { intrsource } else intrsource
     val sink = if (out) intrsink else this { intrsink }
-    sink.node :=? source.node
+    sink.node :*=* source.node
     checks = CrossingCheck(out, source.node, sink.node) :: checks
     NodeHandle(source.node, sink.node)
   }

src/main/scala/coreplex/FrontBus.scala

@@ -28,12 +28,12 @@ class FrontBus(params: FrontBusParams)(implicit p: Parameters) extends TLBusWrap
   master_fixer.node :=* master_buffer.node
   inwardNode :=* master_fixer.node
 
-  def fromSyncPorts(addBuffers: Int = 0, name: Option[String] = None): TLInwardNode = SourceCardinality { implicit p =>
+  def fromSyncPorts(addBuffers: Int = 0, name: Option[String] = None): TLInwardNode = {
-    TLBuffer.chain(addBuffers).foldLeft(master_buffer.node:TLInwardNode)(_ :=? _)
+    TLBuffer.chain(addBuffers).foldLeft(master_buffer.node:TLInwardNode)(_ :=* _)
   }
 
-  def fromSyncMasters(addBuffers: Int = 0, name: Option[String] = None): TLInwardNode = SourceCardinality { implicit p =>
+  def fromSyncMasters(addBuffers: Int = 0, name: Option[String] = None): TLInwardNode = {
-    TLBuffer.chain(addBuffers).foldLeft(master_buffer.node:TLInwardNode)(_ :=? _)
+    TLBuffer.chain(addBuffers).foldLeft(master_buffer.node:TLInwardNode)(_ :=* _)
   }
 
   def fromCoherentChip: TLInwardNode = inwardNode

src/main/scala/coreplex/PeripheryBus.scala

@@ -39,10 +39,8 @@ class PeripheryBus(params: PeripheryBusParams)(implicit p: Parameters) extends T
   def toTile(name: Option[String] = None)(gen: Parameters => TLInwardNode) {
     this {
       LazyScope(s"${busName}ToTile${name.getOrElse("")}") {
-        SinkCardinality { implicit p =>
+        FlipRendering { implicit p =>
-          FlipRendering { implicit p =>
+          gen(p) :*= outwardNode
-            gen(p) :*= outwardNode
-          }
         }
       }
     }

src/main/scala/coreplex/RocketCoreplex.scala

@@ -112,7 +112,7 @@ trait HasRocketTiles extends HasTiles
     wrapper.intXbar.intnode := wrapper { IntSyncCrossingSink(3) } := debug.intnode // 1. always async crossign
 
     // 2. clint+plic conditionak crossing
-    val periphIntNode = SourceCardinality { implicit p => wrapper.intXbar.intnode :=? wrapper.crossIntIn }
+    val periphIntNode = wrapper.intXbar.intnode :=* wrapper.crossIntIn
     periphIntNode := clint.intnode                   // msip+mtip
     periphIntNode := plic.intnode                    // meip
     if (tp.core.useVM) periphIntNode := plic.intnode // seip
@@ -121,9 +121,9 @@ trait HasRocketTiles extends HasTiles
 
     // From core to PLIC
     wrapper.rocket.intOutputNode.foreach { i =>              // 4. conditional crossing
-      FlipRendering { implicit p => SourceCardinality { implicit p =>
+      FlipRendering { implicit p =>
-        plic.intnode :=? wrapper.crossIntOut :=? i
+        plic.intnode :=* wrapper.crossIntOut :=* i
-      } }
+      }
     }
 
     wrapper

src/main/scala/coreplex/SystemBus.scala

@@ -53,9 +53,7 @@ class SystemBus(params: SystemBusParams)(implicit p: Parameters) extends TLBusWr
   def fromTile(name: Option[String])(gen: Parameters => TLOutwardNode) {
     this {
       LazyScope(s"${busName}FromTile${name.getOrElse("")}") {
-        SourceCardinality { implicit p =>
+        master_splitter.node :=* gen(p)
-          master_splitter.node :=* gen(p)
-        }
       }
     }
   }

src/main/scala/diplomacy/Nodes.scala

@@ -9,24 +9,6 @@ import freechips.rocketchip.util.HeterogeneousBag
 import scala.collection.mutable.ListBuffer
 import scala.util.matching._
 
-object CardinalityInferenceDirection {
-  val cases = Seq(SOURCE_TO_SINK, SINK_TO_SOURCE, NO_INFERENCE)
-  sealed trait T {
-    def flip = this match {
-      case SOURCE_TO_SINK => SINK_TO_SOURCE
-      case SINK_TO_SOURCE => SOURCE_TO_SINK
-      case NO_INFERENCE   => NO_INFERENCE
-    }
-  }
-
-  case object SOURCE_TO_SINK extends T
-  case object SINK_TO_SOURCE extends T
-  case object NO_INFERENCE   extends T
-}
-
-private case object CardinalityInferenceDirectionKey extends
-  Field[CardinalityInferenceDirection.T](CardinalityInferenceDirection.NO_INFERENCE)
-
 case object MonitorsEnabled extends Field[Boolean](true)
 case object RenderFlipped extends Field[Boolean](false)
 
@@ -113,6 +95,9 @@ abstract class BaseNode(implicit val valName: ValName)
   protected[diplomacy] def gco: Option[BaseNode] // greatest common outer
   def inputs:  Seq[(BaseNode, RenderedEdge)]
   def outputs: Seq[(BaseNode, RenderedEdge)]
+
+  protected[diplomacy] val sinkCard: Int
+  protected[diplomacy] val sourceCard: Int
 }
 
 object BaseNode
@@ -130,12 +115,12 @@ trait NodeHandle[DI, UI, EI, BI <: Data, DO, UO, EO, BO <: Data]
   override def :=  [DX, UX, EX, BX <: Data, EY](h: NodeHandle[DX, UX, EX, BX, DI, UI, EY, BI])(implicit p: Parameters, sourceInfo: SourceInfo): NodeHandle[DX, UX, EX, BX, DO, UO, EO, BO] = { bind(h, BIND_ONCE);  NodeHandle(h, this) }
   override def :*= [DX, UX, EX, BX <: Data, EY](h: NodeHandle[DX, UX, EX, BX, DI, UI, EY, BI])(implicit p: Parameters, sourceInfo: SourceInfo): NodeHandle[DX, UX, EX, BX, DO, UO, EO, BO] = { bind(h, BIND_STAR);  NodeHandle(h, this) }
   override def :=* [DX, UX, EX, BX <: Data, EY](h: NodeHandle[DX, UX, EX, BX, DI, UI, EY, BI])(implicit p: Parameters, sourceInfo: SourceInfo): NodeHandle[DX, UX, EX, BX, DO, UO, EO, BO] = { bind(h, BIND_QUERY); NodeHandle(h, this) }
-  override def :=? [DX, UX, EX, BX <: Data, EY](h: NodeHandle[DX, UX, EX, BX, DI, UI, EY, BI])(implicit p: Parameters, sourceInfo: SourceInfo): NodeHandle[DX, UX, EX, BX, DO, UO, EO, BO] = { bind(h, p(CardinalityInferenceDirectionKey)); NodeHandle(h, this) }
+  override def :*=*[DX, UX, EX, BX <: Data, EY](h: NodeHandle[DX, UX, EX, BX, DI, UI, EY, BI])(implicit p: Parameters, sourceInfo: SourceInfo): NodeHandle[DX, UX, EX, BX, DO, UO, EO, BO] = { bind(h, BIND_FLEX);  NodeHandle(h, this) }
   // connecting a full node with an output => an output
   override def :=  [EY](h: OutwardNodeHandle[DI, UI, EY, BI])(implicit p: Parameters, sourceInfo: SourceInfo): OutwardNodeHandle[DO, UO, EO, BO] = { bind(h, BIND_ONCE);  this }
   override def :*= [EY](h: OutwardNodeHandle[DI, UI, EY, BI])(implicit p: Parameters, sourceInfo: SourceInfo): OutwardNodeHandle[DO, UO, EO, BO] = { bind(h, BIND_STAR);  this }
   override def :=* [EY](h: OutwardNodeHandle[DI, UI, EY, BI])(implicit p: Parameters, sourceInfo: SourceInfo): OutwardNodeHandle[DO, UO, EO, BO] = { bind(h, BIND_QUERY); this }
-  override def :=? [EY](h: OutwardNodeHandle[DI, UI, EY, BI])(implicit p: Parameters, sourceInfo: SourceInfo): OutwardNodeHandle[DO, UO, EO, BO] = { bind(h, p(CardinalityInferenceDirectionKey)); this }
+  override def :*=*[EY](h: OutwardNodeHandle[DI, UI, EY, BI])(implicit p: Parameters, sourceInfo: SourceInfo): OutwardNodeHandle[DO, UO, EO, BO] = { bind(h, BIND_FLEX);  this }
 }
 
 object NodeHandle
@@ -164,27 +149,19 @@ trait InwardNodeHandle[DI, UI, EI, BI <: Data] extends NoHandle
   def :=  [DX, UX, EX, BX <: Data, EY](h: NodeHandle[DX, UX, EX, BX, DI, UI, EY, BI])(implicit p: Parameters, sourceInfo: SourceInfo): InwardNodeHandle[DX, UX, EX, BX] = { bind(h, BIND_ONCE);  h }
   def :*= [DX, UX, EX, BX <: Data, EY](h: NodeHandle[DX, UX, EX, BX, DI, UI, EY, BI])(implicit p: Parameters, sourceInfo: SourceInfo): InwardNodeHandle[DX, UX, EX, BX] = { bind(h, BIND_STAR);  h }
   def :=* [DX, UX, EX, BX <: Data, EY](h: NodeHandle[DX, UX, EX, BX, DI, UI, EY, BI])(implicit p: Parameters, sourceInfo: SourceInfo): InwardNodeHandle[DX, UX, EX, BX] = { bind(h, BIND_QUERY); h }
-  def :=? [DX, UX, EX, BX <: Data, EY](h: NodeHandle[DX, UX, EX, BX, DI, UI, EY, BI])(implicit p: Parameters, sourceInfo: SourceInfo): InwardNodeHandle[DX, UX, EX, BX] = { bind(h, p(CardinalityInferenceDirectionKey)); h }
+  def :*=*[DX, UX, EX, BX <: Data, EY](h: NodeHandle[DX, UX, EX, BX, DI, UI, EY, BI])(implicit p: Parameters, sourceInfo: SourceInfo): InwardNodeHandle[DX, UX, EX, BX] = { bind(h, BIND_FLEX);  h }
   // connecting input node with output node => no node
   def :=  [EY](h: OutwardNodeHandle[DI, UI, EY, BI])(implicit p: Parameters, sourceInfo: SourceInfo): NoHandle = { bind(h, BIND_ONCE);  NoHandleObject }
   def :*= [EY](h: OutwardNodeHandle[DI, UI, EY, BI])(implicit p: Parameters, sourceInfo: SourceInfo): NoHandle = { bind(h, BIND_STAR);  NoHandleObject }
   def :=* [EY](h: OutwardNodeHandle[DI, UI, EY, BI])(implicit p: Parameters, sourceInfo: SourceInfo): NoHandle = { bind(h, BIND_QUERY); NoHandleObject }
-  def :=? [EY](h: OutwardNodeHandle[DI, UI, EY, BI])(implicit p: Parameters, sourceInfo: SourceInfo): NoHandle = { bind(h, p(CardinalityInferenceDirectionKey)); NoHandleObject }
+  def :*=*[EY](h: OutwardNodeHandle[DI, UI, EY, BI])(implicit p: Parameters, sourceInfo: SourceInfo): NoHandle = { bind(h, BIND_FLEX);  NoHandleObject }
 }
 
 sealed trait NodeBinding
 case object BIND_ONCE  extends NodeBinding
 case object BIND_QUERY extends NodeBinding
 case object BIND_STAR  extends NodeBinding
-
+case object BIND_FLEX  extends NodeBinding
-object NodeBinding
-{
-  implicit def apply(card: CardinalityInferenceDirection.T): NodeBinding = card match {
-    case CardinalityInferenceDirection.SOURCE_TO_SINK => BIND_QUERY
-    case CardinalityInferenceDirection.SINK_TO_SOURCE => BIND_STAR
-    case CardinalityInferenceDirection.NO_INFERENCE   => BIND_ONCE
-  }
-}
 
 trait InwardNode[DI, UI, BI <: Data] extends BaseNode
 {
@@ -253,27 +230,51 @@ sealed abstract class MixedNode[DI, UI, EI, BI <: Data, DO, UO, EO, BO <: Data](
   protected[diplomacy] def mapParamsD(n: Int, p: Seq[DI]): Seq[DO]
   protected[diplomacy] def mapParamsU(n: Int, p: Seq[UO]): Seq[UI]
 
+  protected[diplomacy] lazy val sinkCard   = oBindings.count(_._3 == BIND_QUERY) + iBindings.count(_._3 == BIND_STAR)
+  protected[diplomacy] lazy val sourceCard = iBindings.count(_._3 == BIND_QUERY) + oBindings.count(_._3 == BIND_STAR)
+  protected[diplomacy] lazy val flexOffset = { // positive = sink cardinality; define 0 to be sink (both should work)
+    def DFS(v: BaseNode, visited: Set[BaseNode]): Set[BaseNode] = {
+      if (visited.contains(v)) {
+        visited
+      } else {
+        val flexes = oBindings.filter(_._3 == BIND_FLEX).map(_._2) ++ iBindings.filter(_._3 == BIND_FLEX).map(_._2)
+        flexes.foldLeft(visited + v)((sum, n) => DFS(n, sum))
+      }
+    }
+    val flexSet = DFS(this, Set())
+    val allSink   = flexSet.map(_.sinkCard).sum
+    val allSource = flexSet.map(_.sourceCard).sum
+    require (flexSet.size == 1 || allSink == 0 || allSource == 0,
+      s"The nodes ${flexSet.map(_.name)} which are inter-connected by :*=* have ${allSink} :*= operators and ${allSource} :=* operators connected to them, making it impossible to determine cardinality inference direction.")
+    allSink - allSource
+  }
+
   private var starCycleGuard = false
   protected[diplomacy] lazy val (oPortMapping, iPortMapping, oStar, iStar) = {
     try {
       if (starCycleGuard) throw StarCycleException()
-      val oStars = oBindings.filter { case (_,_,b,_,_) => b == BIND_STAR }.size
+      starCycleGuard = true
-      val iStars = iBindings.filter { case (_,_,b,_,_) => b == BIND_STAR }.size
+      val oStars = oBindings.count { case (_,_,b,_,_) => b == BIND_STAR || (b == BIND_FLEX && flexOffset <  0) }
+      val iStars = iBindings.count { case (_,_,b,_,_) => b == BIND_STAR || (b == BIND_FLEX && flexOffset >= 0) }
       val oKnown = oBindings.map { case (_, n, b, _, _) => b match {
         case BIND_ONCE  => 1
+        case BIND_FLEX  => { if (flexOffset < 0) 0 else n.iStar }
         case BIND_QUERY => n.iStar
         case BIND_STAR  => 0 }}.foldLeft(0)(_+_)
       val iKnown = iBindings.map { case (_, n, b, _, _) => b match {
         case BIND_ONCE  => 1
+        case BIND_FLEX  => { if (flexOffset >= 0) 0 else n.oStar }
         case BIND_QUERY => n.oStar
         case BIND_STAR  => 0 }}.foldLeft(0)(_+_)
       val (iStar, oStar) = resolveStar(iKnown, oKnown, iStars, oStars)
       val oSum = oBindings.map { case (_, n, b, _, _) => b match {
         case BIND_ONCE  => 1
+        case BIND_FLEX  => { if (flexOffset < 0) oStar else n.iStar }
         case BIND_QUERY => n.iStar
         case BIND_STAR  => oStar }}.scanLeft(0)(_+_)
       val iSum = iBindings.map { case (_, n, b, _, _) => b match {
         case BIND_ONCE  => 1
+        case BIND_FLEX  => { if (flexOffset >= 0) iStar else n.oStar }
         case BIND_QUERY => n.oStar
         case BIND_STAR  => iStar }}.scanLeft(0)(_+_)
       val oTotal = oSum.lastOption.getOrElse(0)
@@ -385,6 +386,7 @@ sealed abstract class MixedNode[DI, UI, EI, BI <: Data, DO, UO, EO, BO <: Data](
     val o = y.oPushed
     y.oPush(i, x, binding match {
       case BIND_ONCE  => BIND_ONCE
+      case BIND_FLEX  => BIND_FLEX
       case BIND_STAR  => BIND_QUERY
       case BIND_QUERY => BIND_STAR })
     x.iPush(o, y, binding)

src/main/scala/diplomacy/package.scala

@@ -31,18 +31,6 @@ package object diplomacy
     }
   }
 
-  def SinkCardinality[T](body: Parameters => T)(implicit p: Parameters) = body(p.alterPartial {
-    case CardinalityInferenceDirectionKey => CardinalityInferenceDirection.SINK_TO_SOURCE
-  })
-  def SourceCardinality[T](body: Parameters => T)(implicit p: Parameters) = body(p.alterPartial {
-    case CardinalityInferenceDirectionKey => CardinalityInferenceDirection.SOURCE_TO_SINK
-  })
-  def UnaryCardinality[T](body: Parameters => T)(implicit p: Parameters) = body(p.alterPartial {
-    case CardinalityInferenceDirectionKey => CardinalityInferenceDirection.NO_INFERENCE
-  })
-  def FlipCardinality[T](body: Parameters => T)(implicit p: Parameters) = body(p.alterPartial {
-    case CardinalityInferenceDirectionKey => p(CardinalityInferenceDirectionKey).flip
-  })
   def EnableMonitors[T](body: Parameters => T)(implicit p: Parameters) = body(p.alterPartial {
     case MonitorsEnabled => true
   })

src/main/scala/tilelink/Bus.scala

@@ -72,8 +72,8 @@ abstract class TLBusWrapper(params: TLBusParams, val busName: String)(implicit p
 
   def bufferToSlaves: TLOutwardNode = outwardBufNode 
 
-  def toSyncSlaves(name: Option[String] = None, addBuffers: Int = 0): TLOutwardNode = SinkCardinality { implicit p =>
+  def toSyncSlaves(name: Option[String] = None, addBuffers: Int = 0): TLOutwardNode = {
-    TLBuffer.chain(addBuffers).foldRight(outwardBufNode)(_ :=? _)
+    TLBuffer.chain(addBuffers).foldRight(outwardBufNode)(_ :*= _)
   }
 
   def toVariableWidthSlaves: TLOutwardNode = outwardFragNode