rocket-chip/rocket/src/main/scala/nbdcache.scala

// See LICENSE for license details.

package rocket

import Chisel._
import uncore._
import Util._

case object StoreDataQueueDepth extends Field[Int]
case object ReplayQueueDepth extends Field[Int]
case object NMSHRs extends Field[Int]
case object LRSCCycles extends Field[Int]
case object NDTLBEntries extends Field[Int]

abstract trait L1HellaCacheParameters extends L1CacheParameters {
  val indexmsb = untagBits-1
  val indexlsb = blockOffBits
  val offsetmsb = indexlsb-1
  val offsetlsb = wordOffBits
  val doNarrowRead = coreDataBits * nWays % rowBits == 0
  val encDataBits = code.width(coreDataBits)
  val encRowBits = encDataBits*rowWords
}

abstract class L1HellaCacheBundle extends Bundle with L1HellaCacheParameters
abstract class L1HellaCacheModule extends Module with L1HellaCacheParameters

class StoreGen(typ: Bits, addr: Bits, dat: Bits)
{
  val byte = typ === MT_B || typ === MT_BU
  val half = typ === MT_H || typ === MT_HU
  val word = typ === MT_W || typ === MT_WU
  def mask =
    Mux(byte, Bits(  1) <<     addr(2,0),
    Mux(half, Bits(  3) << Cat(addr(2,1), Bits(0,1)),
    Mux(word, Bits( 15) << Cat(addr(2),   Bits(0,2)),
              Bits(255))))
  def data =
    Mux(byte, Fill(8, dat( 7,0)),
    Mux(half, Fill(4, dat(15,0)),
                      wordData))
  lazy val wordData =
    Mux(word, Fill(2, dat(31,0)),
                      dat)
}

class LoadGen(typ: Bits, addr: Bits, dat: Bits, zero: Bool)
{
  val t = new StoreGen(typ, addr, dat)
  val sign = typ === MT_B || typ === MT_H || typ === MT_W || typ === MT_D

  val wordShift = Mux(addr(2), dat(63,32), dat(31,0))
  val word = Cat(Mux(t.word, Fill(32, sign && wordShift(31)), dat(63,32)), wordShift)
  val halfShift = Mux(addr(1), word(31,16), word(15,0))
  val half = Cat(Mux(t.half, Fill(48, sign && halfShift(15)), word(63,16)), halfShift)
  val byteShift = Mux(zero, UInt(0), Mux(addr(0), half(15,8), half(7,0)))
  val byte = Cat(Mux(zero || t.byte, Fill(56, sign && byteShift(7)), half(63,8)), byteShift)
}

trait HasCoreData extends CoreBundle {
  val data = Bits(width = coreDataBits)
}

class HellaCacheReqInternal extends CoreBundle {
  val kill = Bool()
  val typ  = Bits(width = MT_SZ)
  val phys = Bool()
  val addr = UInt(width = coreMaxAddrBits)
  val tag  = Bits(width = coreDCacheReqTagBits)
  val cmd  = Bits(width = M_SZ)
}

class HellaCacheReq extends HellaCacheReqInternal
    with HasCoreData

class HellaCacheResp extends CoreBundle
    with HasCoreData {
  val nack = Bool() // comes 2 cycles after req.fire
  val replay = Bool()
  val typ = Bits(width = 3)
  val has_data = Bool()
  val data_subword = Bits(width = coreDataBits)
  val tag = Bits(width = coreDCacheReqTagBits)
  val cmd  = Bits(width = 4)
  val addr = UInt(width = coreMaxAddrBits)
  val store_data = Bits(width = coreDataBits)
}

class AlignmentExceptions extends Bundle {
  val ld = Bool()
  val st = Bool()
}

class HellaCacheExceptions extends Bundle {
  val ma = new AlignmentExceptions
  val pf = new AlignmentExceptions
}

// interface between D$ and processor/DTLB
class HellaCacheIO extends CoreBundle {
  val req = Decoupled(new HellaCacheReq)
  val resp = Valid(new HellaCacheResp).flip
  val replay_next = Valid(Bits(width = coreDCacheReqTagBits)).flip
  val xcpt = (new HellaCacheExceptions).asInput
  val ptw = new TLBPTWIO().flip
  val ordered = Bool(INPUT)
}

trait HasSDQId extends CoreBundle {
  val sdq_id = UInt(width = log2Up(params(StoreDataQueueDepth)))
}

trait HasMissInfo extends CoreBundle with L1HellaCacheParameters {
  val tag_match = Bool()
  val old_meta = new L1Metadata
  val way_en = Bits(width = nWays)
}

class MSHRReq extends HellaCacheReqInternal with HasMissInfo with HasCoreData

class MSHRReqInternal extends HellaCacheReqInternal with HasMissInfo with HasSDQId

class Replay extends HellaCacheReqInternal with L1HellaCacheParameters with HasCoreData

class ReplayInternal extends HellaCacheReqInternal with L1HellaCacheParameters with HasSDQId

class DataReadReq extends L1HellaCacheBundle {
  val way_en = Bits(width = nWays)
  val addr   = Bits(width = untagBits)
}

class DataWriteReq extends DataReadReq {
  val wmask  = Bits(width = rowWords)
  val data   = Bits(width = encRowBits)
}

class L1MetaReadReq extends MetaReadReq {
  val tag = Bits(width = tagBits)
}

class L1MetaWriteReq extends 
  MetaWriteReq[L1Metadata](new L1Metadata)

object L1Metadata {
  def apply(tag: Bits, coh: ClientMetadata) = {
    val meta = new L1Metadata
    meta.tag := tag
    meta.coh := coh
    meta
  }
}
class L1Metadata extends Metadata with L1HellaCacheParameters {
  val coh = co.clientMetadataOnFlush.clone
}

class InternalProbe extends Probe with HasClientTransactionId

class WritebackReq extends L1HellaCacheBundle {
  val tag = Bits(width = tagBits)
  val idx = Bits(width = idxBits)
  val way_en = Bits(width = nWays)
  val client_xact_id = Bits(width = params(TLClientXactIdBits))
  val r_type = UInt(width = co.releaseTypeWidth) 
}

class MSHR(id: Int) extends L1HellaCacheModule {
  val io = new Bundle {
    val req_pri_val    = Bool(INPUT)
    val req_pri_rdy    = Bool(OUTPUT)
    val req_sec_val    = Bool(INPUT)
    val req_sec_rdy    = Bool(OUTPUT)
    val req_bits       = new MSHRReqInternal().asInput

    val idx_match       = Bool(OUTPUT)
    val tag             = Bits(OUTPUT, tagBits)

    val mem_req  = Decoupled(new Acquire)
    val mem_resp = new DataWriteReq().asOutput
    val meta_read = Decoupled(new L1MetaReadReq)
    val meta_write = Decoupled(new L1MetaWriteReq)
    val replay = Decoupled(new ReplayInternal)
    val mem_grant = Valid(new LogicalNetworkIO(new Grant)).flip
    val mem_finish = Decoupled(new LogicalNetworkIO(new Finish))
    val wb_req = Decoupled(new WritebackReq)
    val probe_rdy = Bool(OUTPUT)
  }

  val s_invalid :: s_wb_req :: s_wb_resp :: s_meta_clear :: s_refill_req :: s_refill_resp :: s_meta_write_req :: s_meta_write_resp :: s_drain_rpq :: Nil = Enum(UInt(), 9)
  val state = Reg(init=s_invalid)

  val acquire_type = Reg(UInt())
  val release_type = Reg(UInt())
  val line_state = Reg(new ClientMetadata()(co))
  val req = Reg(new MSHRReqInternal())

  val req_cmd = io.req_bits.cmd
  val req_idx = req.addr(untagBits-1,blockOffBits)
  val idx_match = req_idx === io.req_bits.addr(untagBits-1,blockOffBits)
  val sec_rdy = idx_match && (state === s_wb_req || state === s_wb_resp || state === s_meta_clear || (state === s_refill_req || state === s_refill_resp) && !co.needsTransactionOnSecondaryMiss(req_cmd, io.mem_req.bits))

  val reply = io.mem_grant.valid && io.mem_grant.bits.payload.client_xact_id === UInt(id)
  val (refill_cnt, refill_done) = Counter(reply && co.messageUpdatesDataArray(io.mem_grant.bits.payload), refillCycles) // TODO: Zero width?
  val wb_done = reply && (state === s_wb_resp)

  val meta_on_flush = co.clientMetadataOnFlush
  val meta_on_grant = co.clientMetadataOnGrant(io.mem_grant.bits.payload, io.mem_req.bits)
  val meta_on_hit = co.clientMetadataOnHit(req_cmd, io.req_bits.old_meta.coh)

  val rpq = Module(new Queue(new ReplayInternal, params(ReplayQueueDepth)))
  rpq.io.enq.valid := (io.req_pri_val && io.req_pri_rdy || io.req_sec_val && sec_rdy) && !isPrefetch(req_cmd)
  rpq.io.enq.bits := io.req_bits
  rpq.io.deq.ready := io.replay.ready && state === s_drain_rpq || state === s_invalid

  when (state === s_drain_rpq && !rpq.io.deq.valid) {
    state := s_invalid
  }
  when (state === s_meta_write_resp) {
    // this wait state allows us to catch RAW hazards on the tags via nack_victim
    state := s_drain_rpq
  }
  when (state === s_meta_write_req && io.meta_write.ready) {
    state := s_meta_write_resp
  }
  when (state === s_refill_resp) {
    when (refill_done) { state := s_meta_write_req }
    when (reply) {
      if(refillCycles > 1) refill_cnt := refill_cnt + UInt(1)
      line_state := meta_on_grant
    }
  }
  when (io.mem_req.fire()) { // s_refill_req
    state := s_refill_resp
  }
  when (state === s_meta_clear && io.meta_write.ready) {
    state := s_refill_req
  }
  when (state === s_wb_resp && reply) {
    state := s_meta_clear
  }
  when (io.wb_req.fire()) { // s_wb_req
    state := s_wb_resp 
  }
  when (io.req_sec_val && io.req_sec_rdy) { // s_wb_req, s_wb_resp, s_refill_req
    acquire_type := co.getAcquireTypeOnSecondaryMiss(req_cmd, meta_on_flush, io.mem_req.bits)
  }
  when (io.req_pri_val && io.req_pri_rdy) {
    line_state := meta_on_flush
    refill_cnt := UInt(0)
    acquire_type := co.getAcquireTypeOnPrimaryMiss(req_cmd, meta_on_flush)
    release_type := co.getReleaseTypeOnVoluntaryWriteback() //TODO downgrades etc 
    req := io.req_bits

    when (io.req_bits.tag_match) {
      when (co.isHit(req_cmd, io.req_bits.old_meta.coh)) { // set dirty bit
        state := s_meta_write_req
        line_state := meta_on_hit
      }.otherwise { // upgrade permissions
        state := s_refill_req
      }
    }.otherwise { // writback if necessary and refill
      state := Mux(co.needsWriteback(io.req_bits.old_meta.coh), s_wb_req, s_meta_clear)
    }
  }

  val ackq = Module(new Queue(new LogicalNetworkIO(new Finish), 1))
  ackq.io.enq.valid := (wb_done || refill_done) && co.requiresAckForGrant(io.mem_grant.bits.payload)
  ackq.io.enq.bits.payload.master_xact_id := io.mem_grant.bits.payload.master_xact_id
  ackq.io.enq.bits.header.dst := io.mem_grant.bits.header.src
  val can_finish = state === s_invalid || state === s_refill_req || state === s_refill_resp
  io.mem_finish.valid := ackq.io.deq.valid && can_finish
  ackq.io.deq.ready := io.mem_finish.ready && can_finish
  io.mem_finish.bits := ackq.io.deq.bits

  io.idx_match := (state != s_invalid) && idx_match
  io.mem_resp := req
  io.mem_resp.addr := (if(refillCycles > 1) Cat(req_idx, refill_cnt) else req_idx) << rowOffBits
  io.tag := req.addr >> untagBits
  io.req_pri_rdy := state === s_invalid
  io.req_sec_rdy := sec_rdy && rpq.io.enq.ready

  val meta_hazard = Reg(init=UInt(0,2))
  when (meta_hazard != UInt(0)) { meta_hazard := meta_hazard + 1 }
  when (io.meta_write.fire()) { meta_hazard := 1 }
  io.probe_rdy := !idx_match || (state != s_wb_req && state != s_wb_resp && state != s_meta_clear && meta_hazard === 0)

  io.meta_write.valid := state === s_meta_write_req || state === s_meta_clear
  io.meta_write.bits.idx := req_idx
  io.meta_write.bits.data.coh := Mux(state === s_meta_clear, meta_on_flush, line_state)
  io.meta_write.bits.data.tag := io.tag
  io.meta_write.bits.way_en := req.way_en

  io.wb_req.valid := state === s_wb_req && ackq.io.enq.ready
  io.wb_req.bits.tag := req.old_meta.tag
  io.wb_req.bits.idx := req_idx
  io.wb_req.bits.way_en := req.way_en
  io.wb_req.bits.client_xact_id := Bits(id)
  io.wb_req.bits.r_type := co.getReleaseTypeOnVoluntaryWriteback()

  io.mem_req.valid := state === s_refill_req && ackq.io.enq.ready
  io.mem_req.bits := Acquire(acquire_type, Cat(io.tag, req_idx).toUInt, Bits(id))
  io.mem_finish <> ackq.io.deq

  io.meta_read.valid := state === s_drain_rpq
  io.meta_read.bits.idx := req_idx
  io.meta_read.bits.tag := io.tag

  io.replay.valid := state === s_drain_rpq && rpq.io.deq.valid
  io.replay.bits := rpq.io.deq.bits
  io.replay.bits.phys := Bool(true)
  io.replay.bits.addr := Cat(io.tag, req_idx, rpq.io.deq.bits.addr(blockOffBits-1,0)).toUInt

  when (!io.meta_read.ready) {
    rpq.io.deq.ready := Bool(false)
    io.replay.bits.cmd := M_NOP
  }
}

class MSHRFile extends L1HellaCacheModule {
  val io = new Bundle {
    val req = Decoupled(new MSHRReq).flip
    val secondary_miss = Bool(OUTPUT)

    val mem_req  = Decoupled(new Acquire)
    val mem_resp = new DataWriteReq().asOutput
    val meta_read = Decoupled(new L1MetaReadReq)
    val meta_write = Decoupled(new L1MetaWriteReq)
    val replay = Decoupled(new Replay)
    val mem_grant = Valid(new LogicalNetworkIO(new Grant)).flip
    val mem_finish = Decoupled(new LogicalNetworkIO(new Finish))
    val wb_req = Decoupled(new WritebackReq)

    val probe_rdy = Bool(OUTPUT)
    val fence_rdy = Bool(OUTPUT)
  }

  val sdq_val = Reg(init=Bits(0, params(StoreDataQueueDepth)))
  val sdq_alloc_id = PriorityEncoder(~sdq_val(params(StoreDataQueueDepth)-1,0))
  val sdq_rdy = !sdq_val.andR
  val sdq_enq = io.req.valid && io.req.ready && isWrite(io.req.bits.cmd)
  val sdq = Mem(io.req.bits.data, params(StoreDataQueueDepth))
  when (sdq_enq) { sdq(sdq_alloc_id) := io.req.bits.data }

  val idxMatch = Vec.fill(params(NMSHRs)){Bool()}
  val tagList = Vec.fill(params(NMSHRs)){Bits()}
  val tag_match = Mux1H(idxMatch, tagList) === io.req.bits.addr >> untagBits

  val wbTagList = Vec.fill(params(NMSHRs)){Bits()}
  val memRespMux = Vec.fill(params(NMSHRs)){new DataWriteReq}
  val meta_read_arb = Module(new Arbiter(new L1MetaReadReq, params(NMSHRs)))
  val meta_write_arb = Module(new Arbiter(new L1MetaWriteReq, params(NMSHRs)))
  val mem_req_arb = Module(new LockingArbiter(new Acquire, params(NMSHRs), outerDataBeats, co.messageHasData _))
  val mem_finish_arb = Module(new Arbiter(new LogicalNetworkIO(new Finish), params(NMSHRs)))
  val wb_req_arb = Module(new Arbiter(new WritebackReq, params(NMSHRs)))
  val replay_arb = Module(new Arbiter(new ReplayInternal, params(NMSHRs)))
  val alloc_arb = Module(new Arbiter(Bool(), params(NMSHRs)))

  var idx_match = Bool(false)
  var pri_rdy = Bool(false)
  var sec_rdy = Bool(false)

  io.fence_rdy := true
  io.probe_rdy := true

  for (i <- 0 until params(NMSHRs)) {
    val mshr = Module(new MSHR(i))

    idxMatch(i) := mshr.io.idx_match
    tagList(i) := mshr.io.tag
    wbTagList(i) := mshr.io.wb_req.bits.tag

    alloc_arb.io.in(i).valid := mshr.io.req_pri_rdy
    mshr.io.req_pri_val := alloc_arb.io.in(i).ready

    mshr.io.req_sec_val := io.req.valid && sdq_rdy && tag_match
    mshr.io.req_bits := io.req.bits
    mshr.io.req_bits.sdq_id := sdq_alloc_id

    mshr.io.meta_read <> meta_read_arb.io.in(i)
    mshr.io.meta_write <> meta_write_arb.io.in(i)
    mshr.io.mem_req <> mem_req_arb.io.in(i)
    mshr.io.mem_finish <> mem_finish_arb.io.in(i)
    mshr.io.wb_req <> wb_req_arb.io.in(i)
    mshr.io.replay <> replay_arb.io.in(i)

    mshr.io.mem_grant <> io.mem_grant
    memRespMux(i) := mshr.io.mem_resp

    pri_rdy = pri_rdy || mshr.io.req_pri_rdy
    sec_rdy = sec_rdy || mshr.io.req_sec_rdy
    idx_match = idx_match || mshr.io.idx_match

    when (!mshr.io.req_pri_rdy) { io.fence_rdy := false }
    when (!mshr.io.probe_rdy) { io.probe_rdy := false }
  }

  alloc_arb.io.out.ready := io.req.valid && sdq_rdy && !idx_match

  meta_read_arb.io.out <> io.meta_read
  meta_write_arb.io.out <> io.meta_write
  mem_req_arb.io.out <> io.mem_req
  mem_finish_arb.io.out <> io.mem_finish
  wb_req_arb.io.out <> io.wb_req

  io.req.ready := Mux(idx_match, tag_match && sec_rdy, pri_rdy) && sdq_rdy
  io.secondary_miss := idx_match
  io.mem_resp := memRespMux(io.mem_grant.bits.payload.client_xact_id)

  val free_sdq = io.replay.fire() && isWrite(io.replay.bits.cmd)
  io.replay.bits.data := sdq(RegEnable(replay_arb.io.out.bits.sdq_id, free_sdq))
  io.replay <> replay_arb.io.out

  when (io.replay.valid || sdq_enq) {
    sdq_val := sdq_val & ~(UIntToOH(replay_arb.io.out.bits.sdq_id) & Fill(params(StoreDataQueueDepth), free_sdq)) | 
               PriorityEncoderOH(~sdq_val(params(StoreDataQueueDepth)-1,0)) & Fill(params(StoreDataQueueDepth), sdq_enq)
  }
}

class WritebackUnit extends L1HellaCacheModule {
  val io = new Bundle {
    val req = Decoupled(new WritebackReq()).flip
    val meta_read = Decoupled(new L1MetaReadReq)
    val data_req = Decoupled(new DataReadReq())
    val data_resp = Bits(INPUT, encRowBits)
    val release = Decoupled(new Release)
  }

  val active = Reg(init=Bool(false))
  val r1_data_req_fired = Reg(init=Bool(false))
  val r2_data_req_fired = Reg(init=Bool(false))
  val cnt = Reg(init = UInt(0, width = log2Up(refillCycles+1))) //TODO Zero width
  val buf_v = (if(refillCyclesPerBeat > 1) Reg(init=Bits(0, width = refillCyclesPerBeat-1)) else Bits(1))
  val beat_done = buf_v.andR
  val req = Reg(new WritebackReq)

  io.release.valid := false
  when (active) {
    r1_data_req_fired := false
    r2_data_req_fired := r1_data_req_fired
    when (io.data_req.fire() && io.meta_read.fire()) {
      r1_data_req_fired := true
      cnt := cnt + 1
    }
    when (r2_data_req_fired) {
      io.release.valid := beat_done
      when(!io.release.ready) {
        r1_data_req_fired := false
        r2_data_req_fired := false
        cnt := cnt - Mux[UInt](Bool(refillCycles > 1) && r1_data_req_fired, 2, 1)
      } .elsewhen(beat_done) { if(refillCyclesPerBeat > 1) buf_v := 0 }
      when(!r1_data_req_fired) {
        active := cnt < UInt(refillCycles)
      }
    }
  }
  when (io.req.fire()) {
    active := true
    cnt := 0
    if(refillCyclesPerBeat > 1) buf_v := 0
    req := io.req.bits
  }

  val fire = active && cnt < UInt(refillCycles)
  io.req.ready := !active

  // We reissue the meta read as it sets up the muxing for s2_data_muxed
  io.meta_read.valid := fire
  io.meta_read.bits.idx := req.idx
  io.meta_read.bits.tag := req.tag

  io.data_req.valid := fire
  io.data_req.bits.way_en := req.way_en
  io.data_req.bits.addr := (if(refillCycles > 1) Cat(req.idx, cnt(log2Up(refillCycles)-1,0))
                            else req.idx) << rowOffBits

  io.release.bits.r_type := req.r_type
  io.release.bits.addr := Cat(req.tag, req.idx).toUInt
  io.release.bits.client_xact_id := req.client_xact_id
  io.release.bits.data := 
    (if(refillCyclesPerBeat > 1) {
      val data_buf = Reg(Bits())
      when(active && r2_data_req_fired && !beat_done) {
        data_buf := Cat(io.data_resp, data_buf((refillCyclesPerBeat-1)*encRowBits-1, encRowBits))
        buf_v := (if(refillCyclesPerBeat > 2)
                    Cat(UInt(1), buf_v(refillCyclesPerBeat-2,1))
                  else UInt(1))
      }
      Cat(io.data_resp, data_buf)
    } else { io.data_resp })
}

class ProbeUnit extends L1HellaCacheModule {
  val io = new Bundle {
    val req = Decoupled(new InternalProbe).flip
    val rep = Decoupled(new Release)
    val meta_read = Decoupled(new L1MetaReadReq)
    val meta_write = Decoupled(new L1MetaWriteReq)
    val wb_req = Decoupled(new WritebackReq)
    val way_en = Bits(INPUT, nWays)
    val mshr_rdy = Bool(INPUT)
    val line_state = new ClientMetadata()(co).asInput
  }

  val s_reset :: s_invalid :: s_meta_read :: s_meta_resp :: s_mshr_req :: s_release :: s_writeback_req :: s_writeback_resp :: s_meta_write :: Nil = Enum(UInt(), 9)
  val state = Reg(init=s_invalid)
  val line_state = Reg(co.clientMetadataOnFlush.clone)
  val way_en = Reg(Bits())
  val req = Reg(new InternalProbe)
  val hit = way_en.orR

  when (state === s_meta_write && io.meta_write.ready) {
    state := s_invalid
  }
  when (state === s_writeback_resp && io.wb_req.ready) {
    state := s_meta_write
  }
  when (state === s_writeback_req && io.wb_req.ready) {
    state := s_writeback_resp
  }
  when (state === s_release && io.rep.ready) {
    state := s_invalid
    when (hit) {
      state := Mux(co.needsWriteback(line_state), s_writeback_req, s_meta_write)
    }
  }
  when (state === s_mshr_req) {
    state := s_release
    line_state := io.line_state
    way_en := io.way_en
    when (!io.mshr_rdy) { state := s_meta_read }
  }
  when (state === s_meta_resp) {
    state := s_mshr_req
  }
  when (state === s_meta_read && io.meta_read.ready) {
    state := s_meta_resp
  }
  when (state === s_invalid && io.req.valid) {
    state := s_meta_read
    req := io.req.bits
  }
  when (state === s_reset) {
    state := s_invalid
  }

  io.req.ready := state === s_invalid
  io.rep.valid := state === s_release &&
                  !(hit && co.needsWriteback(line_state)) // Otherwise WBU will issue release
  io.rep.bits := Release(co.getReleaseTypeOnProbe(req,
                                                  Mux(hit, line_state, co.clientMetadataOnFlush)),
                                                  req.addr, 
                                                  req.client_xact_id)

  io.meta_read.valid := state === s_meta_read
  io.meta_read.bits.idx := req.addr
  io.meta_read.bits.tag := req.addr >> idxBits

  io.meta_write.valid := state === s_meta_write
  io.meta_write.bits.way_en := way_en
  io.meta_write.bits.idx := req.addr
  io.meta_write.bits.data.coh := co.clientMetadataOnProbe(req, line_state)
  io.meta_write.bits.data.tag := req.addr >> UInt(idxBits)

  io.wb_req.valid := state === s_writeback_req
  io.wb_req.bits.way_en := way_en
  io.wb_req.bits.idx := req.addr
  io.wb_req.bits.tag := req.addr >> UInt(idxBits)
  io.wb_req.bits.r_type := co.getReleaseTypeOnProbe(req, Mux(hit, line_state, co.clientMetadataOnFlush))
  io.wb_req.bits.client_xact_id := req.client_xact_id
}

class DataArray extends L1HellaCacheModule {
  val io = new Bundle {
    val read = Decoupled(new DataReadReq).flip
    val write = Decoupled(new DataWriteReq).flip
    val resp = Vec.fill(nWays){Bits(OUTPUT, encRowBits)}
  }

  val waddr = io.write.bits.addr >> rowOffBits
  val raddr = io.read.bits.addr >> rowOffBits

  if (doNarrowRead) {
    for (w <- 0 until nWays by rowWords) {
      val wway_en = io.write.bits.way_en(w+rowWords-1,w)
      val rway_en = io.read.bits.way_en(w+rowWords-1,w)
      val resp = Vec.fill(rowWords){Bits(width = encRowBits)}
      val r_raddr = RegEnable(io.read.bits.addr, io.read.valid)
      for (p <- 0 until resp.size) {
        val array = Mem(Bits(width=encRowBits), nSets*refillCycles, seqRead = true)
        when (wway_en.orR && io.write.valid && io.write.bits.wmask(p)) {
          val data = Fill(rowWords, io.write.bits.data(encDataBits*(p+1)-1,encDataBits*p))
          val mask = FillInterleaved(encDataBits, wway_en)
          array.write(waddr, data, mask)
        }
        resp(p) := array(RegEnable(raddr, rway_en.orR && io.read.valid))
      }
      for (dw <- 0 until rowWords) {
        val r = Vec(resp.map(_(encDataBits*(dw+1)-1,encDataBits*dw)))
        val resp_mux =
          if (r.size == 1) r
          else Vec(r(r_raddr(rowOffBits-1,wordOffBits)), r.tail:_*)
        io.resp(w+dw) := resp_mux.toBits
      }
    }
  } else {
    val wmask = FillInterleaved(encDataBits, io.write.bits.wmask)
    for (w <- 0 until nWays) {
      val array = Mem(Bits(width=encRowBits), nSets*refillCycles, seqRead = true)
      when (io.write.bits.way_en(w) && io.write.valid) {
        array.write(waddr, io.write.bits.data, wmask)
      }
      io.resp(w) := array(RegEnable(raddr, io.read.bits.way_en(w) && io.read.valid))
    }
  }

  io.read.ready := Bool(true)
  io.write.ready := Bool(true)
}

class AMOALU extends L1HellaCacheModule {
  val io = new Bundle {
    val addr = Bits(INPUT, blockOffBits)
    val cmd = Bits(INPUT, 4)
    val typ = Bits(INPUT, 3)
    val lhs = Bits(INPUT, coreDataBits)
    val rhs = Bits(INPUT, coreDataBits)
    val out = Bits(OUTPUT, coreDataBits)
  }

  require(coreDataBits == 64)
  val storegen = new StoreGen(io.typ, io.addr, io.rhs)
  val rhs = storegen.wordData
  
  val sgned = io.cmd === M_XA_MIN || io.cmd === M_XA_MAX
  val max = io.cmd === M_XA_MAX || io.cmd === M_XA_MAXU
  val min = io.cmd === M_XA_MIN || io.cmd === M_XA_MINU
  val word = io.typ === MT_W || io.typ === MT_WU || io.typ === MT_B || io.typ === MT_BU

  val mask = SInt(-1,64) ^ (io.addr(2) << 31)
  val adder_out = (io.lhs & mask).toUInt + (rhs & mask)

  val cmp_lhs  = Mux(word && !io.addr(2), io.lhs(31), io.lhs(63))
  val cmp_rhs  = Mux(word && !io.addr(2), rhs(31), rhs(63))
  val lt_lo = io.lhs(31,0) < rhs(31,0)
  val lt_hi = io.lhs(63,32) < rhs(63,32)
  val eq_hi = io.lhs(63,32) === rhs(63,32)
  val lt = Mux(word, Mux(io.addr(2), lt_hi, lt_lo), lt_hi || eq_hi && lt_lo)
  val less = Mux(cmp_lhs === cmp_rhs, lt, Mux(sgned, cmp_lhs, cmp_rhs))

  val out = Mux(io.cmd === M_XA_ADD, adder_out,
            Mux(io.cmd === M_XA_AND, io.lhs & rhs,
            Mux(io.cmd === M_XA_OR,  io.lhs | rhs,
            Mux(io.cmd === M_XA_XOR, io.lhs ^ rhs,
            Mux(Mux(less, min, max), io.lhs,
            storegen.data)))))

  val wmask = FillInterleaved(8, storegen.mask)
  io.out := wmask & out | ~wmask & io.lhs
}

class HellaCache extends L1HellaCacheModule {
  val io = new Bundle {
    val cpu = (new HellaCacheIO).flip
    val mem = new TileLinkIO
  }
 
  require(params(LRSCCycles) >= 32) // ISA requires 16-insn LRSC sequences to succeed
  require(isPow2(nSets))
  require(isPow2(nWays)) // TODO: relax this
  require(params(RowBits) <= params(TLDataBits))
  require(paddrBits-blockOffBits == params(TLAddrBits) )
  require(untagBits <= pgIdxBits)

  val wb = Module(new WritebackUnit)
  val prober = Module(new ProbeUnit)
  val mshrs = Module(new MSHRFile)

  io.cpu.req.ready := Bool(true)
  val s1_valid = Reg(next=io.cpu.req.fire(), init=Bool(false))
  val s1_req = Reg(io.cpu.req.bits.clone)
  val s1_valid_masked = s1_valid && !io.cpu.req.bits.kill
  val s1_replay = Reg(init=Bool(false))
  val s1_clk_en = Reg(Bool())

  val s2_valid = Reg(next=s1_valid_masked, init=Bool(false))
  val s2_req = Reg(io.cpu.req.bits.clone)
  val s2_replay = Reg(next=s1_replay, init=Bool(false)) && s2_req.cmd != M_NOP
  val s2_recycle = Bool()
  val s2_valid_masked = Bool()

  val s3_valid = Reg(init=Bool(false))
  val s3_req = Reg(io.cpu.req.bits.clone)
  val s3_way = Reg(Bits())

  val s1_recycled = RegEnable(s2_recycle, s1_clk_en)
  val s1_read  = isRead(s1_req.cmd)
  val s1_write = isWrite(s1_req.cmd)
  val s1_sc = s1_req.cmd === M_XSC
  val s1_readwrite = s1_read || s1_write || isPrefetch(s1_req.cmd)

  val dtlb = Module(new TLB(params(NDTLBEntries)))
  dtlb.io.ptw <> io.cpu.ptw
  dtlb.io.req.valid := s1_valid_masked && s1_readwrite && !s1_req.phys
  dtlb.io.req.bits.passthrough := s1_req.phys
  dtlb.io.req.bits.asid := UInt(0)
  dtlb.io.req.bits.vpn := s1_req.addr >> pgIdxBits
  dtlb.io.req.bits.instruction := Bool(false)
  when (!dtlb.io.req.ready && !io.cpu.req.bits.phys) { io.cpu.req.ready := Bool(false) }
  
  when (io.cpu.req.valid) {
    s1_req := io.cpu.req.bits
  }
  when (wb.io.meta_read.valid) {
    s1_req.addr := Cat(wb.io.meta_read.bits.tag, wb.io.meta_read.bits.idx) << blockOffBits
    s1_req.phys := Bool(true)
  }
  when (prober.io.meta_read.valid) {
    s1_req.addr := Cat(prober.io.meta_read.bits.tag, prober.io.meta_read.bits.idx) << blockOffBits
    s1_req.phys := Bool(true)
  }
  when (mshrs.io.replay.valid) {
    s1_req := mshrs.io.replay.bits
  }
  when (s2_recycle) {
    s1_req := s2_req
  }
  val s1_addr = Cat(dtlb.io.resp.ppn, s1_req.addr(pgIdxBits-1,0))

  when (s1_clk_en) {
    s2_req.kill := s1_req.kill
    s2_req.typ := s1_req.typ
    s2_req.phys := s1_req.phys
    s2_req.addr := s1_addr
    when (s1_write) {
      s2_req.data := Mux(s1_replay, mshrs.io.replay.bits.data, io.cpu.req.bits.data)
    }
    when (s1_recycled) { s2_req.data := s1_req.data }
    s2_req.tag := s1_req.tag
    s2_req.cmd := s1_req.cmd
  }

  val misaligned =
    (((s1_req.typ === MT_H) || (s1_req.typ === MT_HU)) && (s1_req.addr(0) != Bits(0))) ||
    (((s1_req.typ === MT_W) || (s1_req.typ === MT_WU)) && (s1_req.addr(1,0) != Bits(0))) ||
    ((s1_req.typ === MT_D) && (s1_req.addr(2,0) != Bits(0)))
    
  io.cpu.xcpt.ma.ld := s1_read && misaligned
  io.cpu.xcpt.ma.st := s1_write && misaligned
  io.cpu.xcpt.pf.ld := s1_read && dtlb.io.resp.xcpt_ld
  io.cpu.xcpt.pf.st := s1_write && dtlb.io.resp.xcpt_st

  // tags
  def onReset = L1Metadata(UInt(0), ClientMetadata(UInt(0))(co))
  val meta = Module(new MetadataArray(onReset _))
  val metaReadArb = Module(new Arbiter(new MetaReadReq, 5))
  val metaWriteArb = Module(new Arbiter(new L1MetaWriteReq, 2))
  metaReadArb.io.out <> meta.io.read
  metaWriteArb.io.out <> meta.io.write

  // data
  val data = Module(new DataArray)
  val readArb = Module(new Arbiter(new DataReadReq, 4))
  val writeArb = Module(new Arbiter(new DataWriteReq, 2))
  data.io.write.valid := writeArb.io.out.valid
  writeArb.io.out.ready := data.io.write.ready
  data.io.write.bits := writeArb.io.out.bits
  val wdata_encoded = (0 until rowWords).map(i => code.encode(writeArb.io.out.bits.data(coreDataBits*(i+1)-1,coreDataBits*i)))
  data.io.write.bits.data := Vec(wdata_encoded).toBits

  // tag read for new requests
  metaReadArb.io.in(4).valid := io.cpu.req.valid
  metaReadArb.io.in(4).bits.idx := io.cpu.req.bits.addr >> blockOffBits
  when (!metaReadArb.io.in(4).ready) { io.cpu.req.ready := Bool(false) }

  // data read for new requests
  readArb.io.in(3).valid := io.cpu.req.valid
  readArb.io.in(3).bits.addr := io.cpu.req.bits.addr
  readArb.io.in(3).bits.way_en := SInt(-1)
  when (!readArb.io.in(3).ready) { io.cpu.req.ready := Bool(false) }

  // recycled requests
  metaReadArb.io.in(0).valid := s2_recycle
  metaReadArb.io.in(0).bits.idx := s2_req.addr >> blockOffBits
  readArb.io.in(0).valid := s2_recycle
  readArb.io.in(0).bits.addr := s2_req.addr
  readArb.io.in(0).bits.way_en := SInt(-1)

  // tag check and way muxing
  def wayMap[T <: Data](f: Int => T) = Vec((0 until nWays).map(f))
  val s1_tag_eq_way = wayMap((w: Int) => meta.io.resp(w).tag === (s1_addr >> untagBits)).toBits
  val s1_tag_match_way = wayMap((w: Int) => s1_tag_eq_way(w) && co.isValid(meta.io.resp(w).coh)).toBits
  s1_clk_en := metaReadArb.io.out.valid //TODO: should be metaReadArb.io.out.fire(), but triggers Verilog backend bug
  val s1_writeback = s1_clk_en && !s1_valid && !s1_replay
  val s2_tag_match_way = RegEnable(s1_tag_match_way, s1_clk_en)
  val s2_tag_match = s2_tag_match_way.orR
  val s2_hit_state = Mux1H(s2_tag_match_way, wayMap((w: Int) => RegEnable(meta.io.resp(w).coh, s1_clk_en)))
  val s2_hit = s2_tag_match && co.isHit(s2_req.cmd, s2_hit_state) && s2_hit_state === co.clientMetadataOnHit(s2_req.cmd, s2_hit_state)

  // load-reserved/store-conditional
  val lrsc_count = Reg(init=UInt(0))
  val lrsc_valid = lrsc_count.orR
  val lrsc_addr = Reg(UInt())
  val (s2_lr, s2_sc) = (s2_req.cmd === M_XLR, s2_req.cmd === M_XSC)
  val s2_lrsc_addr_match = lrsc_valid && lrsc_addr === (s2_req.addr >> blockOffBits)
  val s2_sc_fail = s2_sc && !s2_lrsc_addr_match
  when (lrsc_valid) { lrsc_count := lrsc_count - 1 }
  when (s2_valid_masked && s2_hit || s2_replay) {
    when (s2_lr) {
      when (!lrsc_valid) { lrsc_count := params(LRSCCycles)-1 }
      lrsc_addr := s2_req.addr >> blockOffBits
    }
    when (s2_sc) {
      lrsc_count := 0
    }
  }
  when (io.cpu.ptw.sret) { lrsc_count := 0 }

  val s2_data = Vec.fill(nWays){Bits(width = encRowBits)}
  for (w <- 0 until nWays) {
    val regs = Vec.fill(rowWords){Reg(Bits(width = encDataBits))}
    val en1 = s1_clk_en && s1_tag_eq_way(w)
    for (i <- 0 until regs.size) {
      val en = en1 && ((Bool(i == 0) || !Bool(doNarrowRead)) || s1_writeback)
      when (en) { regs(i) := data.io.resp(w) >> encDataBits*i }
    }
    s2_data(w) := regs.toBits
  }
  val s2_data_muxed = Mux1H(s2_tag_match_way, s2_data)
  val s2_data_decoded = (0 until rowWords).map(i => code.decode(s2_data_muxed(encDataBits*(i+1)-1,encDataBits*i)))
  val s2_data_corrected = Vec(s2_data_decoded.map(_.corrected)).toBits
  val s2_data_uncorrected = Vec(s2_data_decoded.map(_.uncorrected)).toBits
  val s2_word_idx = if(doNarrowRead) UInt(0) else s2_req.addr(log2Up(rowWords*coreDataBytes)-1,3)
  val s2_data_correctable = Vec(s2_data_decoded.map(_.correctable)).toBits()(s2_word_idx)
  
  // store/amo hits
  s3_valid := (s2_valid_masked && s2_hit || s2_replay) && !s2_sc_fail && isWrite(s2_req.cmd)
  val amoalu = Module(new AMOALU)
  when ((s2_valid || s2_replay) && (isWrite(s2_req.cmd) || s2_data_correctable)) {
    s3_req := s2_req
    s3_req.data := Mux(s2_data_correctable, s2_data_corrected, amoalu.io.out)
    s3_way := s2_tag_match_way
  }

  writeArb.io.in(0).bits.addr := s3_req.addr
  writeArb.io.in(0).bits.wmask := UInt(1) << (if(rowOffBits > offsetlsb) 
                                                s3_req.addr(rowOffBits-1,offsetlsb).toUInt
                                              else UInt(0))
  writeArb.io.in(0).bits.data := Fill(rowWords, s3_req.data)
  writeArb.io.in(0).valid := s3_valid
  writeArb.io.in(0).bits.way_en :=  s3_way

  // replacement policy
  val replacer = params(Replacer)()
  val s1_replaced_way_en = UIntToOH(replacer.way)
  val s2_replaced_way_en = UIntToOH(RegEnable(replacer.way, s1_clk_en))
  val s2_repl_meta = Mux1H(s2_replaced_way_en, wayMap((w: Int) => RegEnable(meta.io.resp(w), s1_clk_en && s1_replaced_way_en(w))).toSeq)

  // miss handling
  mshrs.io.req.valid := s2_valid_masked && !s2_hit && (isPrefetch(s2_req.cmd) || isRead(s2_req.cmd) || isWrite(s2_req.cmd))
  mshrs.io.req.bits := s2_req
  mshrs.io.req.bits.tag_match := s2_tag_match
  mshrs.io.req.bits.old_meta := Mux(s2_tag_match, L1Metadata(s2_repl_meta.tag, s2_hit_state), s2_repl_meta)
  mshrs.io.req.bits.way_en := Mux(s2_tag_match, s2_tag_match_way, s2_replaced_way_en)
  mshrs.io.req.bits.data := s2_req.data
  when (mshrs.io.req.fire()) { replacer.miss }

  io.mem.acquire <> DecoupledLogicalNetworkIOWrapper(mshrs.io.mem_req)

  // replays
  readArb.io.in(1).valid := mshrs.io.replay.valid
  readArb.io.in(1).bits := mshrs.io.replay.bits
  readArb.io.in(1).bits.way_en := SInt(-1)
  mshrs.io.replay.ready := readArb.io.in(1).ready
  s1_replay := mshrs.io.replay.valid && readArb.io.in(1).ready
  metaReadArb.io.in(1) <> mshrs.io.meta_read
  metaWriteArb.io.in(0) <> mshrs.io.meta_write

  // probes and releases
  val releaseArb = Module(new LockingArbiter(new Release, 2, outerDataBeats, co.messageHasData _))
  DecoupledLogicalNetworkIOWrapper(releaseArb.io.out) <> io.mem.release

  val probe = DecoupledLogicalNetworkIOUnwrapper(io.mem.probe)
  prober.io.req.valid := probe.valid && !lrsc_valid
  probe.ready := prober.io.req.ready && !lrsc_valid
  prober.io.req.bits := probe.bits
  prober.io.rep <> releaseArb.io.in(1)
  prober.io.way_en := s2_tag_match_way
  prober.io.line_state := s2_hit_state
  prober.io.meta_read <> metaReadArb.io.in(2)
  prober.io.meta_write <> metaWriteArb.io.in(1)
  prober.io.mshr_rdy := mshrs.io.probe_rdy

  // refills
  def doRefill(g: Grant): Bool = co.messageUpdatesDataArray(g)
  val ser = Module(new FlowThroughSerializer(io.mem.grant.bits, refillCyclesPerBeat, doRefill))
  ser.io.in <> io.mem.grant
  val refill = ser.io.out
  mshrs.io.mem_grant.valid := refill.fire()
  mshrs.io.mem_grant.bits := refill.bits
  refill.ready := writeArb.io.in(1).ready || !doRefill(refill.bits.payload)
  writeArb.io.in(1).valid := refill.valid && doRefill(refill.bits.payload)
  writeArb.io.in(1).bits := mshrs.io.mem_resp
  writeArb.io.in(1).bits.wmask := SInt(-1)
  writeArb.io.in(1).bits.data := refill.bits.payload.data(encRowBits-1,0)
  readArb.io.out.ready := !refill.valid || refill.ready // insert bubble if refill gets blocked
  readArb.io.out <> data.io.read

  // writebacks
  val wbArb = Module(new Arbiter(new WritebackReq, 2))
  prober.io.wb_req <> wbArb.io.in(0)
  mshrs.io.wb_req <> wbArb.io.in(1)
  wbArb.io.out <> wb.io.req
  wb.io.meta_read <> metaReadArb.io.in(3)
  wb.io.data_req <> readArb.io.in(2)
  wb.io.data_resp := s2_data_corrected
  releaseArb.io.in(0) <> wb.io.release

  // store->load bypassing
  val s4_valid = Reg(next=s3_valid, init=Bool(false))
  val s4_req = RegEnable(s3_req, s3_valid && metaReadArb.io.out.valid)
  val bypasses = List(
    ((s2_valid_masked || s2_replay) && !s2_sc_fail, s2_req, amoalu.io.out),
    (s3_valid, s3_req, s3_req.data),
    (s4_valid, s4_req, s4_req.data)
  ).map(r => (r._1 && (s1_addr >> wordOffBits === r._2.addr >> wordOffBits) && isWrite(r._2.cmd), r._3))
  val s2_store_bypass_data = Reg(Bits(width = coreDataBits))
  val s2_store_bypass = Reg(Bool())
  when (s1_clk_en) {
    s2_store_bypass := false
    when (bypasses.map(_._1).reduce(_||_)) {
      s2_store_bypass_data := PriorityMux(bypasses)
      s2_store_bypass := true
    }
  }

  // load data subword mux/sign extension
  val s2_data_word_prebypass = s2_data_uncorrected >> Cat(s2_word_idx, Bits(0,log2Up(coreDataBits)))
  val s2_data_word = Mux(s2_store_bypass, s2_store_bypass_data, s2_data_word_prebypass)
  val loadgen = new LoadGen(s2_req.typ, s2_req.addr, s2_data_word, s2_sc)

  amoalu.io := s2_req
  amoalu.io.lhs := s2_data_word
  amoalu.io.rhs := s2_req.data

  // nack it like it's hot
  val s1_nack = dtlb.io.req.valid && dtlb.io.resp.miss ||
                s1_req.addr(indexmsb,indexlsb) === prober.io.meta_write.bits.idx && !prober.io.req.ready
  val s2_nack_hit = RegEnable(s1_nack, s1_valid || s1_replay)
  when (s2_nack_hit) { mshrs.io.req.valid := Bool(false) }
  val s2_nack_victim = s2_hit && mshrs.io.secondary_miss
  val s2_nack_miss = !s2_hit && !mshrs.io.req.ready
  val s2_nack = s2_nack_hit || s2_nack_victim || s2_nack_miss
  s2_valid_masked := s2_valid && !s2_nack

  val s2_recycle_ecc = (s2_valid || s2_replay) && s2_hit && s2_data_correctable
  val s2_recycle_next = Reg(init=Bool(false))
  when (s1_valid || s1_replay) { s2_recycle_next := (s1_valid || s1_replay) && s2_recycle_ecc }
  s2_recycle := s2_recycle_ecc || s2_recycle_next

  // after a nack, block until nack condition resolves to save energy
  val block_miss = Reg(init=Bool(false))
  block_miss := (s2_valid || block_miss) && s2_nack_miss
  when (block_miss) {
    io.cpu.req.ready := Bool(false)
  }

  io.cpu.resp.valid  := (s2_replay || s2_valid_masked && s2_hit) && !s2_data_correctable
  io.cpu.resp.bits.nack := s2_valid && s2_nack
  io.cpu.resp.bits := s2_req
  io.cpu.resp.bits.has_data := isRead(s2_req.cmd) || s2_sc
  io.cpu.resp.bits.replay := s2_replay
  io.cpu.resp.bits.data := loadgen.word
  io.cpu.resp.bits.data_subword := loadgen.byte | s2_sc_fail
  io.cpu.resp.bits.store_data := s2_req.data
  io.cpu.ordered := mshrs.io.fence_rdy && !s1_valid && !s2_valid

  io.cpu.replay_next.valid := s1_replay && (s1_read || s1_sc)
  io.cpu.replay_next.bits := s1_req.tag

  io.mem.finish <> mshrs.io.mem_finish
}

// exposes a sane decoupled request interface
class SimpleHellaCacheIF extends Module
{
  val io = new Bundle {
    val requestor = new HellaCacheIO().flip
    val cache = new HellaCacheIO
  }

  val replaying_cmb = Bool()
  val replaying = Reg(next = replaying_cmb, init = Bool(false))
  replaying_cmb := replaying

  val replayq1 = Module(new Queue(new HellaCacheReq, 1, flow = true))
  val replayq2 = Module(new Queue(new HellaCacheReq, 1))
  val req_arb = Module(new Arbiter(new HellaCacheReq, 2))

  req_arb.io.in(0) <> replayq1.io.deq
  req_arb.io.in(1).valid := !replaying_cmb && io.requestor.req.valid
  req_arb.io.in(1).bits := io.requestor.req.bits
  io.requestor.req.ready := !replaying_cmb && req_arb.io.in(1).ready

  val s2_nack = io.cache.resp.bits.nack
  val s3_nack = Reg(next=s2_nack)

  val s0_req_fire = io.cache.req.fire()
  val s1_req_fire = Reg(next=s0_req_fire)
  val s2_req_fire = Reg(next=s1_req_fire)

  io.cache.req.bits.kill := s2_nack
  io.cache.req.bits.phys := Bool(true)
  io.cache.req.bits.data := RegEnable(req_arb.io.out.bits.data, s0_req_fire)
  io.cache.req <> req_arb.io.out

  // replay queues
  // replayq1 holds the older request
  // replayq2 holds the newer request (for the first nack)
  // we need to split the queues like this for the case where the older request
  // goes through but gets nacked, while the newer request stalls
  // if this happens, the newer request will go through before the older
  // request
  // we don't need to check replayq1.io.enq.ready and replayq2.io.enq.ready as
  // there will only be two requests going through at most

  // stash d$ request in stage 2 if nacked (older request)
  replayq1.io.enq.valid := Bool(false)
  replayq1.io.enq.bits.cmd := io.cache.resp.bits.cmd
  replayq1.io.enq.bits.typ := io.cache.resp.bits.typ
  replayq1.io.enq.bits.addr := io.cache.resp.bits.addr
  replayq1.io.enq.bits.data := io.cache.resp.bits.store_data
  replayq1.io.enq.bits.tag := io.cache.resp.bits.tag

  // stash d$ request in stage 1 if nacked (newer request)
  replayq2.io.enq.valid := s2_req_fire && s3_nack
  replayq2.io.enq.bits.data := io.cache.resp.bits.store_data
  replayq2.io.enq.bits <> io.cache.resp.bits
  replayq2.io.deq.ready := Bool(false)

  when (s2_nack) {
    replayq1.io.enq.valid := Bool(true)
    replaying_cmb := Bool(true)
  }

  // when replaying request got sunk into the d$
  when (s2_req_fire && Reg(next=Reg(next=replaying_cmb)) && !s2_nack) {
    // see if there's a stashed request in replayq2
    when (replayq2.io.deq.valid) {
      replayq1.io.enq.valid := Bool(true)
      replayq1.io.enq.bits.cmd := replayq2.io.deq.bits.cmd
      replayq1.io.enq.bits.typ := replayq2.io.deq.bits.typ
      replayq1.io.enq.bits.addr := replayq2.io.deq.bits.addr
      replayq1.io.enq.bits.data := replayq2.io.deq.bits.data
      replayq1.io.enq.bits.tag := replayq2.io.deq.bits.tag
      replayq2.io.deq.ready := Bool(true)
    } .otherwise {
      replaying_cmb := Bool(false)
    }
  }

  io.requestor.resp := io.cache.resp
}