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package firrtl.passes

import firrtl._
import firrtl.ir._
import firrtl.Mappers._
import firrtl.PrimOps._
import firrtl.Utils.{one, zero, BoolType}
import MemPortUtils.memPortField
import AnalysisUtils.{Connects, getConnects}
import WrappedExpression.weq
import Annotations._

case class InferReadWriteAnnotation(t: String, tID: TransID)
    extends Annotation with Loose with Unstable {
  val target = CircuitName(t)
  def duplicate(n: Named) = this.copy(t=n.name)
}

// This pass examine the enable signals of the read & write ports of memories
// whose readLatency is greater than 1 (usually SeqMem in Chisel).
// If any product term of the enable signal of the read port is the complement
// of any product term of the enable signal of the write port, then the readwrite
// port is inferred.
object InferReadWritePass extends Pass {
  def name = "Infer ReadWrite Ports"

  type Netlist = collection.mutable.HashMap[String, Expression]
  type Statements = collection.mutable.ArrayBuffer[Statement]
  type PortSet = collection.mutable.HashSet[String]

  private implicit def toString(e: Expression) = e.serialize

  def getProductTerms(connects: Connects)(e: Expression): Seq[Expression] = e match {
    // No ConstProp yet...
    case Mux(cond, tval, fval, _) if weq(tval, one) && weq(fval, zero) =>
      getProductTerms(connects)(cond)
    // Visit each term of AND operation
    case DoPrim(op, args, consts, tpe) if op == And =>
      e +: (args flatMap getProductTerms(connects))
    // Visit connected nodes to references
    case _: WRef | _: WSubField | _: WSubIndex => connects get e match {
      case None => Seq(e)
      case Some(ex) => e +: getProductTerms(connects)(ex)
    }
    // Otherwise just return itself
    case _ => Seq(e)
  }

  def checkComplement(a: Expression, b: Expression) = (a, b) match {
    // b ?= Not(a)
    case (_, DoPrim(Not, args, _, _)) => weq(args.head, a)
    // a ?= Not(b)
    case (DoPrim(Not, args, _, _), _) => weq(args.head, b)
    // b ?= Eq(a, 0) or b ?= Eq(0, a)
    case (_, DoPrim(Eq, args, _, _)) =>
      weq(args(0), a) && weq(args(1), zero) ||
      weq(args(1), a) && weq(args(0), zero)
    // a ?= Eq(b, 0) or b ?= Eq(0, a)
    case (DoPrim(Eq, args, _, _), _) =>
      weq(args(0), b) && weq(args(1), zero) ||
      weq(args(1), b) && weq(args(0), zero)
    case _ => false
  }


  def replaceExp(repl: Netlist)(e: Expression): Expression =
    e map replaceExp(repl) match {
      case e: WSubField => repl getOrElse (e.serialize, e)
      case e => e
    }

  def replaceStmt(repl: Netlist)(s: Statement): Statement =
    s map replaceStmt(repl) map replaceExp(repl) match {
      case Connect(_, EmptyExpression, _) => EmptyStmt 
      case s => s
    }
    
  def inferReadWriteStmt(connects: Connects,
                         repl: Netlist,
                         stmts: Statements)
                         (s: Statement): Statement = s match {
    // infer readwrite ports only for non combinational memories
    case mem: DefMemory if mem.readLatency > 0 =>
      val ut = UnknownType
      val ug = UNKNOWNGENDER
      val readers = new PortSet
      val writers = new PortSet
      val readwriters = collection.mutable.ArrayBuffer[String]()
      val namespace = Namespace(mem.readers ++ mem.writers ++ mem.readwriters)
      for (w <- mem.writers ; r <- mem.readers) {
        val wp = getProductTerms(connects)(memPortField(mem, w, "en"))
        val rp = getProductTerms(connects)(memPortField(mem, r, "en"))
        if (wp exists (a => rp exists (b => checkComplement(a, b)))) {
          val rw = namespace newName "rw"
          val rwExp = createSubField(createRef(mem.name), rw)
          readwriters += rw
          readers += r
          writers += w
          repl(memPortField(mem, r, "clk"))  = EmptyExpression
          repl(memPortField(mem, r, "en"))   = EmptyExpression
          repl(memPortField(mem, r, "addr")) = EmptyExpression
          repl(memPortField(mem, r, "data")) = createSubField(rwExp, "rdata")
          repl(memPortField(mem, w, "clk"))  = EmptyExpression
          repl(memPortField(mem, w, "en"))   = createSubField(rwExp, "wmode")
          repl(memPortField(mem, w, "addr")) = EmptyExpression
          repl(memPortField(mem, w, "data")) = createSubField(rwExp, "wdata")
          repl(memPortField(mem, w, "mask")) = createSubField(rwExp, "wmask")
          stmts += Connect(NoInfo, createSubField(rwExp, "clk"), createRef("clk")) // TODO: fix it
          stmts += Connect(NoInfo, createSubField(rwExp, "en"),
             DoPrim(Or, Seq(connects(memPortField(mem, r, "en")),
                            connects(memPortField(mem, w, "en"))), Nil, BoolType))
          stmts += Connect(NoInfo, createSubField(rwExp, "addr"),
                        Mux(connects(memPortField(mem, w, "en")),
                            connects(memPortField(mem, w, "addr")),
                            connects(memPortField(mem, r, "addr")), UnknownType))
        }
      }
      if (readwriters.isEmpty) mem else mem copy (
        readers = mem.readers filterNot readers,
        writers = mem.writers filterNot writers,
        readwriters = mem.readwriters ++ readwriters)
    case s => s map inferReadWriteStmt(connects, repl, stmts)
  }

  def inferReadWrite(m: DefModule) = {
    val connects = getConnects(m)
    val repl = new Netlist
    val stmts = new Statements
    (m map inferReadWriteStmt(connects, repl, stmts)
       map replaceStmt(repl)) match {
      case m: ExtModule => m
      case m: Module => m copy (body = Block(m.body +: stmts))
    }
  }

  def run(c: Circuit) = c copy (modules = c.modules map inferReadWrite)
}

// Transform input: Middle Firrtl. Called after "HighFirrtlToMidleFirrtl"
// To use this transform, circuit name should be annotated with its TransId.
class InferReadWrite(transID: TransID) extends Transform with SimpleRun {
  def passSeq = Seq(
    InferReadWritePass,
    CheckInitialization,
    InferTypes,
    ResolveKinds,
    ResolveGenders
  )
  def execute(c: Circuit, map: AnnotationMap) = map get transID match {
    case Some(p) => p get CircuitName(c.main) match {
      case Some(InferReadWriteAnnotation(_, _)) => run(c, passSeq)
      case _ => error("Unexpected annotation for InferReadWrite")
    }
    case _ => TransformResult(c)
  }
}