xiangshan/frontend/NewFtq.scala

/***************************************************************************************
* Copyright (c) 2020-2021 Institute of Computing Technology, Chinese Academy of Sciences
* Copyright (c) 2020-2021 Peng Cheng Laboratory
*
* XiangShan is licensed under Mulan PSL v2.
* You can use this software according to the terms and conditions of the Mulan PSL v2.
* You may obtain a copy of Mulan PSL v2 at:
*          http://license.coscl.org.cn/MulanPSL2
*
* THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,
* EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,
* MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
*
* See the Mulan PSL v2 for more details.
***************************************************************************************/

package xiangshan.frontend

import chipsalliance.rocketchip.config.Parameters
import chisel3._
import chisel3.util._
import utils._
import xiangshan._
import xiangshan.frontend.icache._
import xiangshan.backend.CtrlToFtqIO
import xiangshan.backend.decode.ImmUnion

class FtqPtr(implicit p: Parameters) extends CircularQueuePtr[FtqPtr](
  p => p(XSCoreParamsKey).FtqSize
){
}

object FtqPtr {
  def apply(f: Bool, v: UInt)(implicit p: Parameters): FtqPtr = {
    val ptr = Wire(new FtqPtr)
    ptr.flag := f
    ptr.value := v
    ptr
  }
  def inverse(ptr: FtqPtr)(implicit p: Parameters): FtqPtr = {
    apply(!ptr.flag, ptr.value)
  }
}

class FtqNRSRAM[T <: Data](gen: T, numRead: Int)(implicit p: Parameters) extends XSModule {

  val io = IO(new Bundle() {
    val raddr = Input(Vec(numRead, UInt(log2Up(FtqSize).W)))
    val ren = Input(Vec(numRead, Bool()))
    val rdata = Output(Vec(numRead, gen))
    val waddr = Input(UInt(log2Up(FtqSize).W))
    val wen = Input(Bool())
    val wdata = Input(gen)
  })

  for(i <- 0 until numRead){
    val sram = Module(new SRAMTemplate(gen, FtqSize))
    sram.io.r.req.valid := io.ren(i)
    sram.io.r.req.bits.setIdx := io.raddr(i)
    io.rdata(i) := sram.io.r.resp.data(0)
    sram.io.w.req.valid := io.wen
    sram.io.w.req.bits.setIdx := io.waddr
    sram.io.w.req.bits.data := VecInit(io.wdata)
  }

}

class Ftq_RF_Components(implicit p: Parameters) extends XSBundle with BPUUtils {
  val startAddr = UInt(VAddrBits.W)
  val nextLineAddr = UInt(VAddrBits.W)
  val isNextMask = Vec(PredictWidth, Bool())
  val fallThruError = Bool()
  // val carry = Bool()
  def getPc(offset: UInt) = {
    def getHigher(pc: UInt) = pc(VAddrBits-1, log2Ceil(PredictWidth)+instOffsetBits+1)
    def getOffset(pc: UInt) = pc(log2Ceil(PredictWidth)+instOffsetBits, instOffsetBits)
    Cat(getHigher(Mux(isNextMask(offset) && startAddr(log2Ceil(PredictWidth)+instOffsetBits), nextLineAddr, startAddr)),
        getOffset(startAddr)+offset, 0.U(instOffsetBits.W))
  }
  def fromBranchPrediction(resp: BranchPredictionBundle) = {
    def carryPos(addr: UInt) = addr(instOffsetBits+log2Ceil(PredictWidth)+1)
    this.startAddr := resp.pc
    this.nextLineAddr := resp.pc + (FetchWidth * 4 * 2).U // may be broken on other configs
    this.isNextMask := VecInit((0 until PredictWidth).map(i =>
      (resp.pc(log2Ceil(PredictWidth), 1) +& i.U)(log2Ceil(PredictWidth)).asBool()
    ))
    this.fallThruError := resp.fallThruError
    this
  }
  override def toPrintable: Printable = {
    p"startAddr:${Hexadecimal(startAddr)}"
  }
}

class Ftq_pd_Entry(implicit p: Parameters) extends XSBundle {
  val brMask = Vec(PredictWidth, Bool())
  val jmpInfo = ValidUndirectioned(Vec(3, Bool()))
  val jmpOffset = UInt(log2Ceil(PredictWidth).W)
  val jalTarget = UInt(VAddrBits.W)
  val rvcMask = Vec(PredictWidth, Bool())
  def hasJal  = jmpInfo.valid && !jmpInfo.bits(0)
  def hasJalr = jmpInfo.valid && jmpInfo.bits(0)
  def hasCall = jmpInfo.valid && jmpInfo.bits(1)
  def hasRet  = jmpInfo.valid && jmpInfo.bits(2)

  def fromPdWb(pdWb: PredecodeWritebackBundle) = {
    val pds = pdWb.pd
    this.brMask := VecInit(pds.map(pd => pd.isBr && pd.valid))
    this.jmpInfo.valid := VecInit(pds.map(pd => (pd.isJal || pd.isJalr) && pd.valid)).asUInt.orR
    this.jmpInfo.bits := ParallelPriorityMux(pds.map(pd => (pd.isJal || pd.isJalr) && pd.valid),
                                             pds.map(pd => VecInit(pd.isJalr, pd.isCall, pd.isRet)))
    this.jmpOffset := ParallelPriorityEncoder(pds.map(pd => (pd.isJal || pd.isJalr) && pd.valid))
    this.rvcMask := VecInit(pds.map(pd => pd.isRVC))
    this.jalTarget := pdWb.jalTarget
  }

  def toPd(offset: UInt) = {
    require(offset.getWidth == log2Ceil(PredictWidth))
    val pd = Wire(new PreDecodeInfo)
    pd.valid := true.B
    pd.isRVC := rvcMask(offset)
    val isBr = brMask(offset)
    val isJalr = offset === jmpOffset && jmpInfo.valid && jmpInfo.bits(0)
    pd.brType := Cat(offset === jmpOffset && jmpInfo.valid, isJalr || isBr)
    pd.isCall := offset === jmpOffset && jmpInfo.valid && jmpInfo.bits(1)
    pd.isRet  := offset === jmpOffset && jmpInfo.valid && jmpInfo.bits(2)
    pd
  }
}


class Ftq_Redirect_SRAMEntry(implicit p: Parameters) extends XSBundle with HasBPUConst {
  val rasSp = UInt(log2Ceil(RasSize).W)
  val rasEntry = new RASEntry
  // val specCnt = Vec(numBr, UInt(10.W))
  // val ghist = new ShiftingGlobalHistory
  val folded_hist = new AllFoldedHistories(foldedGHistInfos)
  val afhob = new AllAheadFoldedHistoryOldestBits(foldedGHistInfos)
  val lastBrNumOH = UInt((numBr+1).W)

  val histPtr = new CGHPtr

  def fromBranchPrediction(resp: BranchPredictionBundle) = {
    assert(!resp.is_minimal)
    this.rasSp := resp.rasSp
    this.rasEntry := resp.rasTop
    this.folded_hist := resp.folded_hist
    this.afhob := resp.afhob
    this.lastBrNumOH := resp.lastBrNumOH
    this.histPtr := resp.histPtr
    this
  }
}

class Ftq_1R_SRAMEntry(implicit p: Parameters) extends XSBundle with HasBPUConst {
  val meta = UInt(MaxMetaLength.W)
}

class Ftq_Pred_Info(implicit p: Parameters) extends XSBundle {
  val target = UInt(VAddrBits.W)
  val cfiIndex = ValidUndirectioned(UInt(log2Ceil(PredictWidth).W))
}


class FtqRead[T <: Data](private val gen: T)(implicit p: Parameters) extends XSBundle {
  val ptr = Output(new FtqPtr)
  val offset = Output(UInt(log2Ceil(PredictWidth).W))
  val data = Input(gen)
  def apply(ptr: FtqPtr, offset: UInt) = {
    this.ptr := ptr
    this.offset := offset
    this.data
  }
}


class FtqToBpuIO(implicit p: Parameters) extends XSBundle {
  val redirect = Valid(new BranchPredictionRedirect)
  val update = Valid(new BranchPredictionUpdate)
  val enq_ptr = Output(new FtqPtr)
}

class FtqToIfuIO(implicit p: Parameters) extends XSBundle with HasCircularQueuePtrHelper {
  val req = Decoupled(new FetchRequestBundle)
  val redirect = Valid(new Redirect)
  val flushFromBpu = new Bundle {
    // when ifu pipeline is not stalled,
    // a packet from bpu s3 can reach f1 at most
    val s2 = Valid(new FtqPtr)
    val s3 = Valid(new FtqPtr)
    def shouldFlushBy(src: Valid[FtqPtr], idx_to_flush: FtqPtr) = {
      src.valid && !isAfter(src.bits, idx_to_flush)
    }
    def shouldFlushByStage2(idx: FtqPtr) = shouldFlushBy(s2, idx)
    def shouldFlushByStage3(idx: FtqPtr) = shouldFlushBy(s3, idx)
  }
}

trait HasBackendRedirectInfo extends HasXSParameter {
  def numRedirectPcRead = exuParameters.JmpCnt + exuParameters.AluCnt + 1
  def isLoadReplay(r: Valid[Redirect]) = r.bits.flushItself()
}

class FtqToCtrlIO(implicit p: Parameters) extends XSBundle with HasBackendRedirectInfo {
  // write to backend pc mem
  val pc_mem_wen = Output(Bool())
  val pc_mem_waddr = Output(UInt(log2Ceil(FtqSize).W))
  val pc_mem_wdata = Output(new Ftq_RF_Components)
  val target = Output(UInt(VAddrBits.W))
  // predecode correct target
  val pd_redirect_waddr = Valid(UInt(log2Ceil(FtqSize).W))
  val pd_redirect_target = Output(UInt(VAddrBits.W))
}


class FTBEntryGen(implicit p: Parameters) extends XSModule with HasBackendRedirectInfo with HasBPUParameter {
  val io = IO(new Bundle {
    val start_addr = Input(UInt(VAddrBits.W))
    val old_entry = Input(new FTBEntry)
    val pd = Input(new Ftq_pd_Entry)
    val cfiIndex = Flipped(Valid(UInt(log2Ceil(PredictWidth).W)))
    val target = Input(UInt(VAddrBits.W))
    val hit = Input(Bool())
    val mispredict_vec = Input(Vec(PredictWidth, Bool()))

    val new_entry = Output(new FTBEntry)
    val new_br_insert_pos = Output(Vec(numBr, Bool()))
    val taken_mask = Output(Vec(numBr, Bool()))
    val mispred_mask = Output(Vec(numBr+1, Bool()))

    // for perf counters
    val is_init_entry = Output(Bool())
    val is_old_entry = Output(Bool())
    val is_new_br = Output(Bool())
    val is_jalr_target_modified = Output(Bool())
    val is_always_taken_modified = Output(Bool())
    val is_br_full = Output(Bool())
  })

  // no mispredictions detected at predecode
  val hit = io.hit
  val pd = io.pd

  val init_entry = WireInit(0.U.asTypeOf(new FTBEntry))


  val cfi_is_br = pd.brMask(io.cfiIndex.bits) && io.cfiIndex.valid
  val entry_has_jmp = pd.jmpInfo.valid
  val new_jmp_is_jal  = entry_has_jmp && !pd.jmpInfo.bits(0) && io.cfiIndex.valid
  val new_jmp_is_jalr = entry_has_jmp &&  pd.jmpInfo.bits(0) && io.cfiIndex.valid
  val new_jmp_is_call = entry_has_jmp &&  pd.jmpInfo.bits(1) && io.cfiIndex.valid
  val new_jmp_is_ret  = entry_has_jmp &&  pd.jmpInfo.bits(2) && io.cfiIndex.valid
  val last_jmp_rvi = entry_has_jmp && pd.jmpOffset === (PredictWidth-1).U && !pd.rvcMask.last
  // val last_br_rvi = cfi_is_br && io.cfiIndex.bits === (PredictWidth-1).U && !pd.rvcMask.last

  val cfi_is_jal = io.cfiIndex.bits === pd.jmpOffset && new_jmp_is_jal
  val cfi_is_jalr = io.cfiIndex.bits === pd.jmpOffset && new_jmp_is_jalr

  def carryPos = log2Ceil(PredictWidth)+instOffsetBits
  def getLower(pc: UInt) = pc(carryPos-1, instOffsetBits)
  // if not hit, establish a new entry
  init_entry.valid := true.B
  // tag is left for ftb to assign

  // case br
  val init_br_slot = init_entry.getSlotForBr(0)
  when (cfi_is_br) {
    init_br_slot.valid := true.B
    init_br_slot.offset := io.cfiIndex.bits
    init_br_slot.setLowerStatByTarget(io.start_addr, io.target, numBr == 1)
    init_entry.always_taken(0) := true.B // set to always taken on init
  }

  // case jmp
  when (entry_has_jmp) {
    init_entry.tailSlot.offset := pd.jmpOffset
    init_entry.tailSlot.valid := new_jmp_is_jal || new_jmp_is_jalr
    init_entry.tailSlot.setLowerStatByTarget(io.start_addr, Mux(cfi_is_jalr, io.target, pd.jalTarget), isShare=false)
  }

  val jmpPft = getLower(io.start_addr) +& pd.jmpOffset +& Mux(pd.rvcMask(pd.jmpOffset), 1.U, 2.U)
  init_entry.pftAddr := Mux(entry_has_jmp && !last_jmp_rvi, jmpPft, getLower(io.start_addr))
  init_entry.carry   := Mux(entry_has_jmp && !last_jmp_rvi, jmpPft(carryPos-instOffsetBits), true.B)
  init_entry.isJalr := new_jmp_is_jalr
  init_entry.isCall := new_jmp_is_call
  init_entry.isRet  := new_jmp_is_ret
  // that means fall thru points to the middle of an inst
  init_entry.last_may_be_rvi_call := pd.jmpOffset === (PredictWidth-1).U && !pd.rvcMask(pd.jmpOffset)

  // if hit, check whether a new cfi(only br is possible) is detected
  val oe = io.old_entry
  val br_recorded_vec = oe.getBrRecordedVec(io.cfiIndex.bits)
  val br_recorded = br_recorded_vec.asUInt.orR
  val is_new_br = cfi_is_br && !br_recorded
  val new_br_offset = io.cfiIndex.bits
  // vec(i) means new br will be inserted BEFORE old br(i)
  val allBrSlotsVec = oe.allSlotsForBr
  val new_br_insert_onehot = VecInit((0 until numBr).map{
    i => i match {
      case 0 =>
        !allBrSlotsVec(0).valid || new_br_offset < allBrSlotsVec(0).offset
      case idx =>
        allBrSlotsVec(idx-1).valid && new_br_offset > allBrSlotsVec(idx-1).offset &&
        (!allBrSlotsVec(idx).valid || new_br_offset < allBrSlotsVec(idx).offset)
    }
  })

  val old_entry_modified = WireInit(io.old_entry)
  for (i <- 0 until numBr) {
    val slot = old_entry_modified.allSlotsForBr(i)
    when (new_br_insert_onehot(i)) {
      slot.valid := true.B
      slot.offset := new_br_offset
      slot.setLowerStatByTarget(io.start_addr, io.target, i == numBr-1)
      old_entry_modified.always_taken(i) := true.B
    }.elsewhen (new_br_offset > oe.allSlotsForBr(i).offset) {
      old_entry_modified.always_taken(i) := false.B
      // all other fields remain unchanged
    }.otherwise {
      // case i == 0, remain unchanged
      if (i != 0) {
        val noNeedToMoveFromFormerSlot = (i == numBr-1).B && !oe.brSlots.last.valid
        when (!noNeedToMoveFromFormerSlot) {
          slot.fromAnotherSlot(oe.allSlotsForBr(i-1))
          old_entry_modified.always_taken(i) := oe.always_taken(i)
        }
      }
    }
  }

  // two circumstances:
  // 1. oe: | br | j  |, new br should be in front of j, thus addr of j should be new pft
  // 2. oe: | br | br |, new br could be anywhere between, thus new pft is the addr of either
  //        the previous last br or the new br
  val may_have_to_replace = oe.noEmptySlotForNewBr
  val pft_need_to_change = is_new_br && may_have_to_replace
  // it should either be the given last br or the new br
  when (pft_need_to_change) {
    val new_pft_offset =
      Mux(!new_br_insert_onehot.asUInt.orR,
        new_br_offset, oe.allSlotsForBr.last.offset)

    // set jmp to invalid
    old_entry_modified.pftAddr := getLower(io.start_addr) + new_pft_offset
    old_entry_modified.carry := (getLower(io.start_addr) +& new_pft_offset).head(1).asBool
    old_entry_modified.last_may_be_rvi_call := false.B
    old_entry_modified.isCall := false.B
    old_entry_modified.isRet := false.B
    old_entry_modified.isJalr := false.B
  }

  val old_entry_jmp_target_modified = WireInit(oe)
  val old_target = oe.tailSlot.getTarget(io.start_addr) // may be wrong because we store only 20 lowest bits
  val old_tail_is_jmp = !oe.tailSlot.sharing
  val jalr_target_modified = cfi_is_jalr && (old_target =/= io.target) && old_tail_is_jmp // TODO: pass full jalr target
  when (jalr_target_modified) {
    old_entry_jmp_target_modified.setByJmpTarget(io.start_addr, io.target)
    old_entry_jmp_target_modified.always_taken := 0.U.asTypeOf(Vec(numBr, Bool()))
  }

  val old_entry_always_taken = WireInit(oe)
  val always_taken_modified_vec = Wire(Vec(numBr, Bool())) // whether modified or not
  for (i <- 0 until numBr) {
    old_entry_always_taken.always_taken(i) :=
      oe.always_taken(i) && io.cfiIndex.valid && oe.brValids(i) && io.cfiIndex.bits === oe.brOffset(i)
    always_taken_modified_vec(i) := oe.always_taken(i) && !old_entry_always_taken.always_taken(i)
  }
  val always_taken_modified = always_taken_modified_vec.reduce(_||_)


  val derived_from_old_entry =
    Mux(is_new_br, old_entry_modified,
      Mux(jalr_target_modified, old_entry_jmp_target_modified, old_entry_always_taken))


  io.new_entry := Mux(!hit, init_entry, derived_from_old_entry)

  io.new_br_insert_pos := new_br_insert_onehot
  io.taken_mask := VecInit((io.new_entry.brOffset zip io.new_entry.brValids).map{
    case (off, v) => io.cfiIndex.bits === off && io.cfiIndex.valid && v
  })
  for (i <- 0 until numBr) {
    io.mispred_mask(i) := io.new_entry.brValids(i) && io.mispredict_vec(io.new_entry.brOffset(i))
  }
  io.mispred_mask.last := io.new_entry.jmpValid && io.mispredict_vec(pd.jmpOffset)

  // for perf counters
  io.is_init_entry := !hit
  io.is_old_entry := hit && !is_new_br && !jalr_target_modified && !always_taken_modified
  io.is_new_br := hit && is_new_br
  io.is_jalr_target_modified := hit && jalr_target_modified
  io.is_always_taken_modified := hit && always_taken_modified
  io.is_br_full := hit && is_new_br && may_have_to_replace
}

class Ftq(implicit p: Parameters) extends XSModule with HasCircularQueuePtrHelper
  with HasBackendRedirectInfo with BPUUtils with HasBPUConst with HasPerfEvents
  with HasICacheParameters{
  val io = IO(new Bundle {
    val fromBpu = Flipped(new BpuToFtqIO)
    val fromIfu = Flipped(new IfuToFtqIO)
    val fromBackend = Flipped(new CtrlToFtqIO)

    val toBpu = new FtqToBpuIO
    val toIfu = new FtqToIfuIO
    val toBackend = new FtqToCtrlIO

    val toPrefetch = new FtqPrefechBundle

    val bpuInfo = new Bundle {
      val bpRight = Output(UInt(XLEN.W))
      val bpWrong = Output(UInt(XLEN.W))
    }
  })
  io.bpuInfo := DontCare

  val backendRedirect = Wire(Valid(new Redirect))
  val backendRedirectReg = RegNext(backendRedirect)

  val stage2Flush = backendRedirect.valid
  val backendFlush = stage2Flush || RegNext(stage2Flush)
  val ifuFlush = Wire(Bool())

  val flush = stage2Flush || RegNext(stage2Flush)

  val allowBpuIn, allowToIfu = WireInit(false.B)
  val flushToIfu = !allowToIfu
  allowBpuIn := !ifuFlush && !backendRedirect.valid && !backendRedirectReg.valid
  allowToIfu := !ifuFlush && !backendRedirect.valid && !backendRedirectReg.valid

  val bpuPtr, ifuPtr, ifuWbPtr, commPtr = RegInit(FtqPtr(false.B, 0.U))
  val ifuPtrPlus1 = RegInit(FtqPtr(false.B, 1.U))
  val validEntries = distanceBetween(bpuPtr, commPtr)

  // **********************************************************************
  // **************************** enq from bpu ****************************
  // **********************************************************************
  val new_entry_ready = validEntries < FtqSize.U
  io.fromBpu.resp.ready := new_entry_ready

  val bpu_s2_resp = io.fromBpu.resp.bits.s2
  val bpu_s3_resp = io.fromBpu.resp.bits.s3
  val bpu_s2_redirect = bpu_s2_resp.valid && bpu_s2_resp.hasRedirect
  val bpu_s3_redirect = bpu_s3_resp.valid && bpu_s3_resp.hasRedirect

  io.toBpu.enq_ptr := bpuPtr
  val enq_fire = io.fromBpu.resp.fire() && allowBpuIn // from bpu s1
  val bpu_in_fire = (io.fromBpu.resp.fire() || bpu_s2_redirect || bpu_s3_redirect) && allowBpuIn

  val bpu_in_resp = io.fromBpu.resp.bits.selectedResp
  val bpu_in_stage = io.fromBpu.resp.bits.selectedRespIdx
  val bpu_in_resp_ptr = Mux(bpu_in_stage === BP_S1, bpuPtr, bpu_in_resp.ftq_idx)
  val bpu_in_resp_idx = bpu_in_resp_ptr.value

  // read ports:                                                ifuReq1 + ifuReq2 + commitUpdate
  val ftq_pc_mem = Module(new SyncDataModuleTemplate(new Ftq_RF_Components, FtqSize, 3, 1, "FtqPC",
    concatData=false, Some(Seq.tabulate(3)(i => false))))
  // resp from uBTB
  ftq_pc_mem.io.wen(0) := bpu_in_fire
  ftq_pc_mem.io.waddr(0) := bpu_in_resp_idx
  ftq_pc_mem.io.wdata(0).fromBranchPrediction(bpu_in_resp)

  //                                                            ifuRedirect + backendRedirect + commit
  val ftq_redirect_sram = Module(new FtqNRSRAM(new Ftq_Redirect_SRAMEntry, 1+1+1))
  // these info is intended to enq at the last stage of bpu
  ftq_redirect_sram.io.wen := io.fromBpu.resp.bits.lastStage.valid
  ftq_redirect_sram.io.waddr := io.fromBpu.resp.bits.lastStage.ftq_idx.value
  ftq_redirect_sram.io.wdata.fromBranchPrediction(io.fromBpu.resp.bits.lastStage)
  println(f"ftq redirect SRAM: entry ${ftq_redirect_sram.io.wdata.getWidth} * ${FtqSize} * 3")
  println(f"ftq redirect SRAM: ahead fh ${ftq_redirect_sram.io.wdata.afhob.getWidth} * ${FtqSize} * 3")

  val ftq_meta_1r_sram = Module(new FtqNRSRAM(new Ftq_1R_SRAMEntry, 1))
  // these info is intended to enq at the last stage of bpu
  ftq_meta_1r_sram.io.wen := io.fromBpu.resp.bits.lastStage.valid
  ftq_meta_1r_sram.io.waddr := io.fromBpu.resp.bits.lastStage.ftq_idx.value
  ftq_meta_1r_sram.io.wdata.meta := io.fromBpu.resp.bits.meta
  //                                                            ifuRedirect + backendRedirect + commit
  val ftb_entry_mem = Module(new SyncDataModuleTemplate(new FTBEntry, FtqSize, 1+1+1, 1))
  ftb_entry_mem.io.wen(0) := io.fromBpu.resp.bits.lastStage.valid
  ftb_entry_mem.io.waddr(0) := io.fromBpu.resp.bits.lastStage.ftq_idx.value
  ftb_entry_mem.io.wdata(0) := io.fromBpu.resp.bits.lastStage.ftb_entry


  // multi-write
  val update_target = Reg(Vec(FtqSize, UInt(VAddrBits.W))) // could be taken target or fallThrough
  val cfiIndex_vec = Reg(Vec(FtqSize, ValidUndirectioned(UInt(log2Ceil(PredictWidth).W))))
  val mispredict_vec = Reg(Vec(FtqSize, Vec(PredictWidth, Bool())))
  val pred_stage = Reg(Vec(FtqSize, UInt(2.W)))

  val c_invalid :: c_valid :: c_commited :: Nil = Enum(3)
  val commitStateQueue = RegInit(VecInit(Seq.fill(FtqSize) {
    VecInit(Seq.fill(PredictWidth)(c_invalid))
  }))

  val f_to_send :: f_sent :: Nil = Enum(2)
  val entry_fetch_status = RegInit(VecInit(Seq.fill(FtqSize)(f_sent)))

  val h_not_hit :: h_false_hit :: h_hit :: Nil = Enum(3)
  val entry_hit_status = RegInit(VecInit(Seq.fill(FtqSize)(h_not_hit)))

  // modify registers one cycle later to cut critical path
  val last_cycle_bpu_in = RegNext(bpu_in_fire)
  val last_cycle_bpu_in_idx = RegNext(bpu_in_resp_idx)
  val last_cycle_update_target = RegNext(bpu_in_resp.getTarget)
  val last_cycle_cfiIndex = RegNext(bpu_in_resp.cfiIndex)
  val last_cycle_bpu_in_stage = RegNext(bpu_in_stage)
  when (last_cycle_bpu_in) {
    entry_fetch_status(last_cycle_bpu_in_idx) := f_to_send
    commitStateQueue(last_cycle_bpu_in_idx) := VecInit(Seq.fill(PredictWidth)(c_invalid))
    cfiIndex_vec(last_cycle_bpu_in_idx) := last_cycle_cfiIndex
    mispredict_vec(last_cycle_bpu_in_idx) := WireInit(VecInit(Seq.fill(PredictWidth)(false.B)))
    update_target(last_cycle_bpu_in_idx) := last_cycle_update_target
    pred_stage(last_cycle_bpu_in_idx) := last_cycle_bpu_in_stage
  }


  bpuPtr := bpuPtr + enq_fire
  when (io.toIfu.req.fire && allowToIfu) {
    ifuPtr := ifuPtrPlus1
    ifuPtrPlus1 := ifuPtrPlus1 + 1.U
  }

  // only use ftb result to assign hit status
  when (bpu_s2_resp.valid) {
    entry_hit_status(bpu_s2_resp.ftq_idx.value) := Mux(bpu_s2_resp.full_pred.hit, h_hit, h_not_hit)
  }


  io.toIfu.flushFromBpu.s2.valid := bpu_s2_redirect
  io.toIfu.flushFromBpu.s2.bits := bpu_s2_resp.ftq_idx
  when (bpu_s2_resp.valid && bpu_s2_resp.hasRedirect) {
    bpuPtr := bpu_s2_resp.ftq_idx + 1.U
    // only when ifuPtr runs ahead of bpu s2 resp should we recover it
    when (!isBefore(ifuPtr, bpu_s2_resp.ftq_idx)) {
      ifuPtr := bpu_s2_resp.ftq_idx
      ifuPtrPlus1 := bpu_s2_resp.ftq_idx + 1.U
    }
  }

  io.toIfu.flushFromBpu.s3.valid := bpu_s3_redirect
  io.toIfu.flushFromBpu.s3.bits := bpu_s3_resp.ftq_idx
  when (bpu_s3_resp.valid && bpu_s3_resp.hasRedirect) {
    bpuPtr := bpu_s3_resp.ftq_idx + 1.U
    // only when ifuPtr runs ahead of bpu s2 resp should we recover it
    when (!isBefore(ifuPtr, bpu_s3_resp.ftq_idx)) {
      ifuPtr := bpu_s3_resp.ftq_idx
      ifuPtrPlus1 := bpu_s3_resp.ftq_idx + 1.U
    }
  }

  XSError(isBefore(bpuPtr, ifuPtr) && !isFull(bpuPtr, ifuPtr), "\nifuPtr is before bpuPtr!\n")

  // ****************************************************************
  // **************************** to ifu ****************************
  // ****************************************************************
  val bpu_in_bypass_buf = RegEnable(ftq_pc_mem.io.wdata(0), bpu_in_fire)
  val bpu_in_bypass_ptr = RegNext(bpu_in_resp_ptr)
  val last_cycle_to_ifu_fire = RegNext(io.toIfu.req.fire)

  // read pc and target
  ftq_pc_mem.io.raddr.init.init.last := ifuPtr.value
  ftq_pc_mem.io.raddr.init.last := ifuPtrPlus1.value

  io.toIfu.req.bits.ftqIdx := ifuPtr


  val toIfuPcBundle = Wire(new Ftq_RF_Components)
  val entry_is_to_send = WireInit(entry_fetch_status(ifuPtr.value) === f_to_send)
  val entry_next_addr = WireInit(update_target(ifuPtr.value))
  val entry_ftq_offset = WireInit(cfiIndex_vec(ifuPtr.value))


  when (last_cycle_bpu_in && bpu_in_bypass_ptr === ifuPtr) {
    toIfuPcBundle := bpu_in_bypass_buf
    entry_is_to_send := true.B
    entry_next_addr := last_cycle_update_target
    entry_ftq_offset := last_cycle_cfiIndex
  }.elsewhen (last_cycle_to_ifu_fire) {
    toIfuPcBundle := ftq_pc_mem.io.rdata.init.last
    entry_is_to_send := RegNext(entry_fetch_status(ifuPtrPlus1.value) === f_to_send) ||
                        RegNext(last_cycle_bpu_in && bpu_in_bypass_ptr === (ifuPtrPlus1)) // reduce potential bubbles
  }.otherwise {
    toIfuPcBundle := ftq_pc_mem.io.rdata.init.init.last
    entry_is_to_send := RegNext(entry_fetch_status(ifuPtr.value) === f_to_send)
  }

  io.toIfu.req.valid := entry_is_to_send && ifuPtr =/= bpuPtr
  io.toIfu.req.bits.nextStartAddr := entry_next_addr
  io.toIfu.req.bits.ftqOffset := entry_ftq_offset
  io.toIfu.req.bits.fromFtqPcBundle(toIfuPcBundle)

  // when fall through is smaller in value than start address, there must be a false hit
  when (toIfuPcBundle.fallThruError && entry_hit_status(ifuPtr.value) === h_hit) {
    when (io.toIfu.req.fire &&
      !(bpu_s2_redirect && bpu_s2_resp.ftq_idx === ifuPtr) &&
      !(bpu_s3_redirect && bpu_s3_resp.ftq_idx === ifuPtr)
    ) {
      entry_hit_status(ifuPtr.value) := h_false_hit
      // XSError(true.B, "FTB false hit by fallThroughError, startAddr: %x, fallTHru: %x\n", io.toIfu.req.bits.startAddr, io.toIfu.req.bits.nextStartAddr)
    }
    XSDebug(true.B, "fallThruError! start:%x, fallThru:%x\n", io.toIfu.req.bits.startAddr, io.toIfu.req.bits.nextStartAddr)
  }

  XSPerfAccumulate(f"fall_through_error_to_ifu", toIfuPcBundle.fallThruError && entry_hit_status(ifuPtr.value) === h_hit &&
    io.toIfu.req.fire && !(bpu_s2_redirect && bpu_s2_resp.ftq_idx === ifuPtr) && !(bpu_s3_redirect && bpu_s3_resp.ftq_idx === ifuPtr))

  val ifu_req_should_be_flushed =
    io.toIfu.flushFromBpu.shouldFlushByStage2(io.toIfu.req.bits.ftqIdx) ||
    io.toIfu.flushFromBpu.shouldFlushByStage3(io.toIfu.req.bits.ftqIdx)

    when (io.toIfu.req.fire && !ifu_req_should_be_flushed) {
      entry_fetch_status(ifuPtr.value) := f_sent
    }

  // *********************************************************************
  // **************************** wb from ifu ****************************
  // *********************************************************************
  val pdWb = io.fromIfu.pdWb
  val pds = pdWb.bits.pd
  val ifu_wb_valid = pdWb.valid
  val ifu_wb_idx = pdWb.bits.ftqIdx.value
  // read ports:                                                         commit update
  val ftq_pd_mem = Module(new SyncDataModuleTemplate(new Ftq_pd_Entry, FtqSize, 1, 1))
  ftq_pd_mem.io.wen(0) := ifu_wb_valid
  ftq_pd_mem.io.waddr(0) := pdWb.bits.ftqIdx.value
  ftq_pd_mem.io.wdata(0).fromPdWb(pdWb.bits)

  val hit_pd_valid = entry_hit_status(ifu_wb_idx) === h_hit && ifu_wb_valid
  val hit_pd_mispred = hit_pd_valid && pdWb.bits.misOffset.valid
  val hit_pd_mispred_reg = RegNext(hit_pd_mispred, init=false.B)
  val pd_reg       = RegEnable(pds,             pdWb.valid)
  val start_pc_reg = RegEnable(pdWb.bits.pc(0), pdWb.valid)
  val wb_idx_reg   = RegEnable(ifu_wb_idx,      pdWb.valid)

  when (ifu_wb_valid) {
    val comm_stq_wen = VecInit(pds.map(_.valid).zip(pdWb.bits.instrRange).map{
      case (v, inRange) => v && inRange
    })
    (commitStateQueue(ifu_wb_idx) zip comm_stq_wen).map{
      case (qe, v) => when (v) { qe := c_valid }
    }
  }

  ifuWbPtr := ifuWbPtr + ifu_wb_valid

  ftb_entry_mem.io.raddr.head := ifu_wb_idx
  val has_false_hit = WireInit(false.B)
  when (RegNext(hit_pd_valid)) {
    // check for false hit
    val pred_ftb_entry = ftb_entry_mem.io.rdata.head
    val brSlots = pred_ftb_entry.brSlots
    val tailSlot = pred_ftb_entry.tailSlot
    // we check cfis that bpu predicted

    // bpu predicted branches but denied by predecode
    val br_false_hit =
      brSlots.map{
        s => s.valid && !(pd_reg(s.offset).valid && pd_reg(s.offset).isBr)
      }.reduce(_||_) ||
      (tailSlot.valid && pred_ftb_entry.tailSlot.sharing &&
        !(pd_reg(tailSlot.offset).valid && pd_reg(tailSlot.offset).isBr))

    val jmpOffset = tailSlot.offset
    val jmp_pd = pd_reg(jmpOffset)
    val jal_false_hit = pred_ftb_entry.jmpValid &&
      ((pred_ftb_entry.isJal  && !(jmp_pd.valid && jmp_pd.isJal)) ||
       (pred_ftb_entry.isJalr && !(jmp_pd.valid && jmp_pd.isJalr)) ||
       (pred_ftb_entry.isCall && !(jmp_pd.valid && jmp_pd.isCall)) ||
       (pred_ftb_entry.isRet  && !(jmp_pd.valid && jmp_pd.isRet))
      )

    has_false_hit := br_false_hit || jal_false_hit || hit_pd_mispred_reg
    XSDebug(has_false_hit, "FTB false hit by br or jal or hit_pd, startAddr: %x\n", pdWb.bits.pc(0))

    // assert(!has_false_hit)
  }

  when (has_false_hit) {
    entry_hit_status(wb_idx_reg) := h_false_hit
  }


  // **********************************************************************
  // ***************************** to backend *****************************
  // **********************************************************************
  // to backend pc mem / target
  io.toBackend.pc_mem_wen   := RegNext(last_cycle_bpu_in)
  io.toBackend.pc_mem_waddr := RegNext(last_cycle_bpu_in_idx)
  io.toBackend.pc_mem_wdata := RegNext(bpu_in_bypass_buf)
  io.toBackend.target       := RegNext(last_cycle_update_target)

  // *******************************************************************************
  // **************************** redirect from backend ****************************
  // *******************************************************************************

  // redirect read cfiInfo, couples to redirectGen s2
  ftq_redirect_sram.io.ren.init.last := backendRedirect.valid
  ftq_redirect_sram.io.raddr.init.last := backendRedirect.bits.ftqIdx.value

  ftb_entry_mem.io.raddr.init.last := backendRedirect.bits.ftqIdx.value

  val stage3CfiInfo = ftq_redirect_sram.io.rdata.init.last
  val fromBackendRedirect = WireInit(backendRedirectReg)
  val backendRedirectCfi = fromBackendRedirect.bits.cfiUpdate
  backendRedirectCfi.fromFtqRedirectSram(stage3CfiInfo)

  val r_ftb_entry = ftb_entry_mem.io.rdata.init.last
  val r_ftqOffset = fromBackendRedirect.bits.ftqOffset

  when (entry_hit_status(fromBackendRedirect.bits.ftqIdx.value) === h_hit) {
    backendRedirectCfi.shift := PopCount(r_ftb_entry.getBrMaskByOffset(r_ftqOffset)) +&
      (backendRedirectCfi.pd.isBr && !r_ftb_entry.brIsSaved(r_ftqOffset) &&
      !r_ftb_entry.newBrCanNotInsert(r_ftqOffset))

    backendRedirectCfi.addIntoHist := backendRedirectCfi.pd.isBr && (r_ftb_entry.brIsSaved(r_ftqOffset) ||
        !r_ftb_entry.newBrCanNotInsert(r_ftqOffset))
  }.otherwise {
    backendRedirectCfi.shift := (backendRedirectCfi.pd.isBr && backendRedirectCfi.taken).asUInt
    backendRedirectCfi.addIntoHist := backendRedirectCfi.pd.isBr.asUInt
  }


  // ***************************************************************************
  // **************************** redirect from ifu ****************************
  // ***************************************************************************
  val fromIfuRedirect = WireInit(0.U.asTypeOf(Valid(new Redirect)))
  fromIfuRedirect.valid := pdWb.valid && pdWb.bits.misOffset.valid && !backendFlush
  fromIfuRedirect.bits.ftqIdx := pdWb.bits.ftqIdx
  fromIfuRedirect.bits.ftqOffset := pdWb.bits.misOffset.bits
  fromIfuRedirect.bits.level := RedirectLevel.flushAfter

  val ifuRedirectCfiUpdate = fromIfuRedirect.bits.cfiUpdate
  ifuRedirectCfiUpdate.pc := pdWb.bits.pc(pdWb.bits.misOffset.bits)
  ifuRedirectCfiUpdate.pd := pdWb.bits.pd(pdWb.bits.misOffset.bits)
  ifuRedirectCfiUpdate.predTaken := cfiIndex_vec(pdWb.bits.ftqIdx.value).valid
  ifuRedirectCfiUpdate.target := pdWb.bits.target
  ifuRedirectCfiUpdate.taken := pdWb.bits.cfiOffset.valid
  ifuRedirectCfiUpdate.isMisPred := pdWb.bits.misOffset.valid

  val ifuRedirectReg = RegNext(fromIfuRedirect, init=0.U.asTypeOf(Valid(new Redirect)))
  val ifuRedirectToBpu = WireInit(ifuRedirectReg)
  ifuFlush := fromIfuRedirect.valid || ifuRedirectToBpu.valid

  ftq_redirect_sram.io.ren.head := fromIfuRedirect.valid
  ftq_redirect_sram.io.raddr.head := fromIfuRedirect.bits.ftqIdx.value

  ftb_entry_mem.io.raddr.head := fromIfuRedirect.bits.ftqIdx.value

  val toBpuCfi = ifuRedirectToBpu.bits.cfiUpdate
  toBpuCfi.fromFtqRedirectSram(ftq_redirect_sram.io.rdata.head)
  when (ifuRedirectReg.bits.cfiUpdate.pd.isRet) {
    toBpuCfi.target := toBpuCfi.rasEntry.retAddr
  }

  // *********************************************************************
  // **************************** wb from exu ****************************
  // *********************************************************************

  backendRedirect := io.fromBackend.redirect

  def extractRedirectInfo(wb: Valid[Redirect]) = {
    val ftqIdx = wb.bits.ftqIdx.value
    val ftqOffset = wb.bits.ftqOffset
    val taken = wb.bits.cfiUpdate.taken
    val mispred = wb.bits.cfiUpdate.isMisPred
    (wb.valid, ftqIdx, ftqOffset, taken, mispred)
  }

  // fix mispredict entry
  val lastIsMispredict = RegNext(
    backendRedirect.valid && backendRedirect.bits.level === RedirectLevel.flushAfter, init = false.B
  )

  def updateCfiInfo(redirect: Valid[Redirect], isBackend: Boolean = true) = {
    val (r_valid, r_idx, r_offset, r_taken, r_mispred) = extractRedirectInfo(redirect)
    val cfiIndex_bits_wen = r_valid && r_taken && r_offset < cfiIndex_vec(r_idx).bits
    val cfiIndex_valid_wen = r_valid && r_offset === cfiIndex_vec(r_idx).bits
    when (cfiIndex_bits_wen || cfiIndex_valid_wen) {
      cfiIndex_vec(r_idx).valid := cfiIndex_bits_wen || cfiIndex_valid_wen && r_taken
    }
    when (cfiIndex_bits_wen) {
      cfiIndex_vec(r_idx).bits := r_offset
    }
    update_target(r_idx) := redirect.bits.cfiUpdate.target
    if (isBackend) {
      mispredict_vec(r_idx)(r_offset) := r_mispred
    }
  }

  // write to backend target vec
  io.toBackend.pd_redirect_waddr.valid := RegNext(fromIfuRedirect.valid)
  io.toBackend.pd_redirect_waddr.bits  := RegNext(fromIfuRedirect.bits.ftqIdx.value)
  io.toBackend.pd_redirect_target      := RegNext(fromIfuRedirect.bits.cfiUpdate.target)

  when(backendRedirectReg.valid && lastIsMispredict) {
    updateCfiInfo(backendRedirectReg)
  }.elsewhen (ifuRedirectToBpu.valid) {
    updateCfiInfo(ifuRedirectToBpu, isBackend=false)
  }

  // ***********************************************************************************
  // **************************** flush ptr and state queue ****************************
  // ***********************************************************************************

  val redirectVec = VecInit(backendRedirect, fromIfuRedirect)

  // when redirect, we should reset ptrs and status queues
  when(redirectVec.map(r => r.valid).reduce(_||_)){
    val r = PriorityMux(redirectVec.map(r => (r.valid -> r.bits)))
    val notIfu = redirectVec.dropRight(1).map(r => r.valid).reduce(_||_)
    val (idx, offset, flushItSelf) = (r.ftqIdx, r.ftqOffset, RedirectLevel.flushItself(r.level))
    val next = idx + 1.U
    bpuPtr := next
    ifuPtr := next
    ifuWbPtr := next
    ifuPtrPlus1 := idx + 2.U
    when (notIfu) {
      commitStateQueue(idx.value).zipWithIndex.foreach({ case (s, i) =>
        when(i.U > offset || i.U === offset && flushItSelf){
          s := c_invalid
        }
      })
    }
  }

  // only the valid bit is actually needed
  io.toIfu.redirect.bits    := backendRedirect.bits
  io.toIfu.redirect.valid   := stage2Flush

  // commit
  for (c <- io.fromBackend.rob_commits) {
    when(c.valid) {
      commitStateQueue(c.bits.ftqIdx.value)(c.bits.ftqOffset) := c_commited
      // TODO: remove this
      // For instruction fusions, we also update the next instruction
      when (c.bits.commitType === 4.U) {
        commitStateQueue(c.bits.ftqIdx.value)(c.bits.ftqOffset + 1.U) := c_commited
      }.elsewhen(c.bits.commitType === 5.U) {
        commitStateQueue(c.bits.ftqIdx.value)(c.bits.ftqOffset + 2.U) := c_commited
      }.elsewhen(c.bits.commitType === 6.U) {
        val index = (c.bits.ftqIdx + 1.U).value
        commitStateQueue(index)(0) := c_commited
      }.elsewhen(c.bits.commitType === 7.U) {
        val index = (c.bits.ftqIdx + 1.U).value
        commitStateQueue(index)(1) := c_commited
      }
    }
  }

  // ****************************************************************
  // **************************** to bpu ****************************
  // ****************************************************************

  io.toBpu.redirect <> Mux(fromBackendRedirect.valid, fromBackendRedirect, ifuRedirectToBpu)

  val may_have_stall_from_bpu = Wire(Bool())
  val bpu_ftb_update_stall = RegInit(0.U(2.W)) // 2-cycle stall, so we need 3 states
  may_have_stall_from_bpu := bpu_ftb_update_stall =/= 0.U
  val canCommit = commPtr =/= ifuWbPtr && !may_have_stall_from_bpu &&
    Cat(commitStateQueue(commPtr.value).map(s => {
      s === c_invalid || s === c_commited
    })).andR()

  // commit reads
  ftq_pc_mem.io.raddr.last := commPtr.value
  val commit_pc_bundle = ftq_pc_mem.io.rdata.last
  ftq_pd_mem.io.raddr.last := commPtr.value
  val commit_pd = ftq_pd_mem.io.rdata.last
  ftq_redirect_sram.io.ren.last := canCommit
  ftq_redirect_sram.io.raddr.last := commPtr.value
  val commit_spec_meta = ftq_redirect_sram.io.rdata.last
  ftq_meta_1r_sram.io.ren(0) := canCommit
  ftq_meta_1r_sram.io.raddr(0) := commPtr.value
  val commit_meta = ftq_meta_1r_sram.io.rdata(0)
  ftb_entry_mem.io.raddr.last := commPtr.value
  val commit_ftb_entry = ftb_entry_mem.io.rdata.last

  // need one cycle to read mem and srams
  val do_commit_ptr = RegNext(commPtr)
  val do_commit = RegNext(canCommit, init=false.B)
  when (canCommit) { commPtr := commPtr + 1.U }
  val commit_state = RegNext(commitStateQueue(commPtr.value))
  val can_commit_cfi = WireInit(cfiIndex_vec(commPtr.value))
  when (commitStateQueue(commPtr.value)(can_commit_cfi.bits) =/= c_commited) {
    can_commit_cfi.valid := false.B
  }
  val commit_cfi = RegNext(can_commit_cfi)

  val commit_mispredict = VecInit((RegNext(mispredict_vec(commPtr.value)) zip commit_state).map {
    case (mis, state) => mis && state === c_commited
  })
  val can_commit_hit = entry_hit_status(commPtr.value)
  val commit_hit = RegNext(can_commit_hit)
  val commit_target = RegNext(update_target(commPtr.value))
  val commit_stage = RegNext(pred_stage(commPtr.value))
  val commit_valid = commit_hit === h_hit || commit_cfi.valid // hit or taken

  val to_bpu_hit = can_commit_hit === h_hit || can_commit_hit === h_false_hit
  switch (bpu_ftb_update_stall) {
    is (0.U) {
      when (can_commit_cfi.valid && !to_bpu_hit && canCommit) {
        bpu_ftb_update_stall := 2.U // 2-cycle stall
      }
    }
    is (2.U) {
      bpu_ftb_update_stall := 1.U
    }
    is (1.U) {
      bpu_ftb_update_stall := 0.U
    }
    is (3.U) {
      XSError(true.B, "bpu_ftb_update_stall should be 0, 1 or 2")
    }
  }

  io.toBpu.update := DontCare
  io.toBpu.update.valid := commit_valid && do_commit
  val update = io.toBpu.update.bits
  update.false_hit   := commit_hit === h_false_hit
  update.pc          := commit_pc_bundle.startAddr
  update.meta        := commit_meta.meta
  update.full_target := commit_target
  update.from_stage  := commit_stage
  update.fromFtqRedirectSram(commit_spec_meta)

  val commit_real_hit = commit_hit === h_hit
  val update_ftb_entry = update.ftb_entry

  val ftbEntryGen = Module(new FTBEntryGen).io
  ftbEntryGen.start_addr     := commit_pc_bundle.startAddr
  ftbEntryGen.old_entry      := commit_ftb_entry
  ftbEntryGen.pd             := commit_pd
  ftbEntryGen.cfiIndex       := commit_cfi
  ftbEntryGen.target         := commit_target
  ftbEntryGen.hit            := commit_real_hit
  ftbEntryGen.mispredict_vec := commit_mispredict

  update_ftb_entry         := ftbEntryGen.new_entry
  update.new_br_insert_pos := ftbEntryGen.new_br_insert_pos
  update.mispred_mask      := ftbEntryGen.mispred_mask
  update.old_entry         := ftbEntryGen.is_old_entry
  update.pred_hit          := commit_hit === h_hit || commit_hit === h_false_hit

  update.is_minimal := false.B
  update.full_pred.fromFtbEntry(ftbEntryGen.new_entry, update.pc)
  update.full_pred.br_taken_mask  := ftbEntryGen.taken_mask
  update.full_pred.jalr_target := commit_target
  update.full_pred.hit := true.B
  when (update.full_pred.is_jalr) {
    update.full_pred.targets.last := commit_target
  }

  // ****************************************************************
  // *********************** to prefetch ****************************
  // ****************************************************************

  if(cacheParams.hasPrefetch){
    val prefetchPtr = RegInit(FtqPtr(false.B, 0.U))
    prefetchPtr := prefetchPtr + io.toPrefetch.req.fire()

    when (bpu_s2_resp.valid && bpu_s2_resp.hasRedirect && !isBefore(prefetchPtr, bpu_s2_resp.ftq_idx)) {
      prefetchPtr := bpu_s2_resp.ftq_idx
    }

    when (bpu_s3_resp.valid && bpu_s3_resp.hasRedirect && !isBefore(prefetchPtr, bpu_s3_resp.ftq_idx)) {
      prefetchPtr := bpu_s3_resp.ftq_idx
      // XSError(true.B, "\ns3_redirect mechanism not implemented!\n")
    }


    val prefetch_is_to_send = WireInit(entry_fetch_status(prefetchPtr.value) === f_to_send)
    val prefetch_addr = WireInit(update_target(prefetchPtr.value))

    when (last_cycle_bpu_in && bpu_in_bypass_ptr === prefetchPtr) {
      prefetch_is_to_send := true.B
      prefetch_addr := last_cycle_update_target
    }
    io.toPrefetch.req.valid := prefetchPtr =/= bpuPtr && prefetch_is_to_send
    io.toPrefetch.req.bits.target := prefetch_addr

    when(redirectVec.map(r => r.valid).reduce(_||_)){
      val r = PriorityMux(redirectVec.map(r => (r.valid -> r.bits)))
      val next = r.ftqIdx + 1.U
      prefetchPtr := next
    }

    XSError(isBefore(bpuPtr, prefetchPtr) && !isFull(bpuPtr, prefetchPtr), "\nprefetchPtr is before bpuPtr!\n")
    XSError(isBefore(prefetchPtr, ifuPtr) && !isFull(ifuPtr, prefetchPtr), "\nifuPtr is before prefetchPtr!\n")
  }
  else {
    io.toPrefetch.req <> DontCare
  }

  // ******************************************************************************
  // **************************** commit perf counters ****************************
  // ******************************************************************************

  val commit_inst_mask    = VecInit(commit_state.map(c => c === c_commited && do_commit)).asUInt
  val commit_mispred_mask = commit_mispredict.asUInt
  val commit_not_mispred_mask = ~commit_mispred_mask

  val commit_br_mask = commit_pd.brMask.asUInt
  val commit_jmp_mask = UIntToOH(commit_pd.jmpOffset) & Fill(PredictWidth, commit_pd.jmpInfo.valid.asTypeOf(UInt(1.W)))
  val commit_cfi_mask = (commit_br_mask | commit_jmp_mask)

  val mbpInstrs = commit_inst_mask & commit_cfi_mask

  val mbpRights = mbpInstrs & commit_not_mispred_mask
  val mbpWrongs = mbpInstrs & commit_mispred_mask

  io.bpuInfo.bpRight := PopCount(mbpRights)
  io.bpuInfo.bpWrong := PopCount(mbpWrongs)

  // Cfi Info
  for (i <- 0 until PredictWidth) {
    val pc = commit_pc_bundle.startAddr + (i * instBytes).U
    val v = commit_state(i) === c_commited
    val isBr = commit_pd.brMask(i)
    val isJmp = commit_pd.jmpInfo.valid && commit_pd.jmpOffset === i.U
    val isCfi = isBr || isJmp
    val isTaken = commit_cfi.valid && commit_cfi.bits === i.U
    val misPred = commit_mispredict(i)
    // val ghist = commit_spec_meta.ghist.predHist
    val histPtr = commit_spec_meta.histPtr
    val predCycle = commit_meta.meta(63, 0)
    val target = commit_target

    val brIdx = OHToUInt(Reverse(Cat(update_ftb_entry.brValids.zip(update_ftb_entry.brOffset).map{case(v, offset) => v && offset === i.U})))
    val inFtbEntry = update_ftb_entry.brValids.zip(update_ftb_entry.brOffset).map{case(v, offset) => v && offset === i.U}.reduce(_||_)
    val addIntoHist = ((commit_hit === h_hit) && inFtbEntry) || ((!(commit_hit === h_hit) && i.U === commit_cfi.bits && isBr && commit_cfi.valid))
    XSDebug(v && do_commit && isCfi, p"cfi_update: isBr(${isBr}) pc(${Hexadecimal(pc)}) " +
    p"taken(${isTaken}) mispred(${misPred}) cycle($predCycle) hist(${histPtr.value}) " +
    p"startAddr(${Hexadecimal(commit_pc_bundle.startAddr)}) AddIntoHist(${addIntoHist}) " +
    p"brInEntry(${inFtbEntry}) brIdx(${brIdx}) target(${Hexadecimal(target)})\n")
  }

  val enq = io.fromBpu.resp
  val perf_redirect = backendRedirect

  XSPerfAccumulate("entry", validEntries)
  XSPerfAccumulate("bpu_to_ftq_stall", enq.valid && !enq.ready)
  XSPerfAccumulate("mispredictRedirect", perf_redirect.valid && RedirectLevel.flushAfter === perf_redirect.bits.level)
  XSPerfAccumulate("replayRedirect", perf_redirect.valid && RedirectLevel.flushItself(perf_redirect.bits.level))
  XSPerfAccumulate("predecodeRedirect", fromIfuRedirect.valid)

  XSPerfAccumulate("to_ifu_bubble", io.toIfu.req.ready && !io.toIfu.req.valid)

  XSPerfAccumulate("to_ifu_stall", io.toIfu.req.valid && !io.toIfu.req.ready)
  XSPerfAccumulate("from_bpu_real_bubble", !enq.valid && enq.ready && allowBpuIn)
  XSPerfAccumulate("bpu_to_ifu_bubble", bpuPtr === ifuPtr)

  val from_bpu = io.fromBpu.resp.bits
  def in_entry_len_map_gen(resp: BranchPredictionBundle)(stage: String) = {
    assert(!resp.is_minimal)
    val entry_len = (resp.ftb_entry.getFallThrough(resp.pc) - resp.pc) >> instOffsetBits
    val entry_len_recording_vec = (1 to PredictWidth+1).map(i => entry_len === i.U)
    val entry_len_map = (1 to PredictWidth+1).map(i =>
      f"${stage}_ftb_entry_len_$i" -> (entry_len_recording_vec(i-1) && resp.valid)
    ).foldLeft(Map[String, UInt]())(_+_)
    entry_len_map
  }
  val s2_entry_len_map = in_entry_len_map_gen(from_bpu.s2)("s2")
  val s3_entry_len_map = in_entry_len_map_gen(from_bpu.s3)("s3")

  val to_ifu = io.toIfu.req.bits


  val commit_num_inst_recording_vec = (1 to PredictWidth).map(i => PopCount(commit_inst_mask) === i.U)
  val commit_num_inst_map = (1 to PredictWidth).map(i =>
    f"commit_num_inst_$i" -> (commit_num_inst_recording_vec(i-1) && do_commit)
  ).foldLeft(Map[String, UInt]())(_+_)


  val commit_jal_mask  = UIntToOH(commit_pd.jmpOffset) & Fill(PredictWidth, commit_pd.hasJal.asTypeOf(UInt(1.W)))
  val commit_jalr_mask = UIntToOH(commit_pd.jmpOffset) & Fill(PredictWidth, commit_pd.hasJalr.asTypeOf(UInt(1.W)))
  val commit_call_mask = UIntToOH(commit_pd.jmpOffset) & Fill(PredictWidth, commit_pd.hasCall.asTypeOf(UInt(1.W)))
  val commit_ret_mask  = UIntToOH(commit_pd.jmpOffset) & Fill(PredictWidth, commit_pd.hasRet.asTypeOf(UInt(1.W)))


  val mbpBRights = mbpRights & commit_br_mask
  val mbpJRights = mbpRights & commit_jal_mask
  val mbpIRights = mbpRights & commit_jalr_mask
  val mbpCRights = mbpRights & commit_call_mask
  val mbpRRights = mbpRights & commit_ret_mask

  val mbpBWrongs = mbpWrongs & commit_br_mask
  val mbpJWrongs = mbpWrongs & commit_jal_mask
  val mbpIWrongs = mbpWrongs & commit_jalr_mask
  val mbpCWrongs = mbpWrongs & commit_call_mask
  val mbpRWrongs = mbpWrongs & commit_ret_mask

  val commit_pred_stage = RegNext(pred_stage(commPtr.value))

  def pred_stage_map(src: UInt, name: String) = {
    (0 until numBpStages).map(i =>
      f"${name}_stage_${i+1}" -> PopCount(src.asBools.map(_ && commit_pred_stage === BP_STAGES(i)))
    ).foldLeft(Map[String, UInt]())(_+_)
  }

  val mispred_stage_map      = pred_stage_map(mbpWrongs,  "mispredict")
  val br_mispred_stage_map   = pred_stage_map(mbpBWrongs, "br_mispredict")
  val jalr_mispred_stage_map = pred_stage_map(mbpIWrongs, "jalr_mispredict")
  val correct_stage_map      = pred_stage_map(mbpRights,  "correct")
  val br_correct_stage_map   = pred_stage_map(mbpBRights, "br_correct")
  val jalr_correct_stage_map = pred_stage_map(mbpIRights, "jalr_correct")

  val update_valid = io.toBpu.update.valid
  def u(cond: Bool) = update_valid && cond
  val ftb_false_hit = u(update.false_hit)
  // assert(!ftb_false_hit)
  val ftb_hit = u(commit_hit === h_hit)

  val ftb_new_entry = u(ftbEntryGen.is_init_entry)
  val ftb_new_entry_only_br = ftb_new_entry && !update_ftb_entry.jmpValid
  val ftb_new_entry_only_jmp = ftb_new_entry && !update_ftb_entry.brValids(0)
  val ftb_new_entry_has_br_and_jmp = ftb_new_entry && update_ftb_entry.brValids(0) && update_ftb_entry.jmpValid

  val ftb_old_entry = u(ftbEntryGen.is_old_entry)

  val ftb_modified_entry = u(ftbEntryGen.is_new_br || ftbEntryGen.is_jalr_target_modified || ftbEntryGen.is_always_taken_modified)
  val ftb_modified_entry_new_br = u(ftbEntryGen.is_new_br)
  val ftb_modified_entry_jalr_target_modified = u(ftbEntryGen.is_jalr_target_modified)
  val ftb_modified_entry_br_full = ftb_modified_entry && ftbEntryGen.is_br_full
  val ftb_modified_entry_always_taken = ftb_modified_entry && ftbEntryGen.is_always_taken_modified

  val ftb_entry_len = (ftbEntryGen.new_entry.getFallThrough(update.pc) - update.pc) >> instOffsetBits
  val ftb_entry_len_recording_vec = (1 to PredictWidth+1).map(i => ftb_entry_len === i.U)
  val ftb_init_entry_len_map = (1 to PredictWidth+1).map(i =>
    f"ftb_init_entry_len_$i" -> (ftb_entry_len_recording_vec(i-1) && ftb_new_entry)
  ).foldLeft(Map[String, UInt]())(_+_)
  val ftb_modified_entry_len_map = (1 to PredictWidth+1).map(i =>
    f"ftb_modified_entry_len_$i" -> (ftb_entry_len_recording_vec(i-1) && ftb_modified_entry)
  ).foldLeft(Map[String, UInt]())(_+_)

  val ftq_occupancy_map = (0 to FtqSize).map(i =>
    f"ftq_has_entry_$i" ->( validEntries === i.U)
  ).foldLeft(Map[String, UInt]())(_+_)

  val perfCountsMap = Map(
    "BpInstr" -> PopCount(mbpInstrs),
    "BpBInstr" -> PopCount(mbpBRights | mbpBWrongs),
    "BpRight"  -> PopCount(mbpRights),
    "BpWrong"  -> PopCount(mbpWrongs),
    "BpBRight" -> PopCount(mbpBRights),
    "BpBWrong" -> PopCount(mbpBWrongs),
    "BpJRight" -> PopCount(mbpJRights),
    "BpJWrong" -> PopCount(mbpJWrongs),
    "BpIRight" -> PopCount(mbpIRights),
    "BpIWrong" -> PopCount(mbpIWrongs),
    "BpCRight" -> PopCount(mbpCRights),
    "BpCWrong" -> PopCount(mbpCWrongs),
    "BpRRight" -> PopCount(mbpRRights),
    "BpRWrong" -> PopCount(mbpRWrongs),

    "ftb_false_hit"                -> PopCount(ftb_false_hit),
    "ftb_hit"                      -> PopCount(ftb_hit),
    "ftb_new_entry"                -> PopCount(ftb_new_entry),
    "ftb_new_entry_only_br"        -> PopCount(ftb_new_entry_only_br),
    "ftb_new_entry_only_jmp"       -> PopCount(ftb_new_entry_only_jmp),
    "ftb_new_entry_has_br_and_jmp" -> PopCount(ftb_new_entry_has_br_and_jmp),
    "ftb_old_entry"                -> PopCount(ftb_old_entry),
    "ftb_modified_entry"           -> PopCount(ftb_modified_entry),
    "ftb_modified_entry_new_br"    -> PopCount(ftb_modified_entry_new_br),
    "ftb_jalr_target_modified"     -> PopCount(ftb_modified_entry_jalr_target_modified),
    "ftb_modified_entry_br_full"   -> PopCount(ftb_modified_entry_br_full),
    "ftb_modified_entry_always_taken" -> PopCount(ftb_modified_entry_always_taken)
  ) ++ ftb_init_entry_len_map ++ ftb_modified_entry_len_map ++ s2_entry_len_map ++
  s3_entry_len_map ++ commit_num_inst_map ++ ftq_occupancy_map ++
  mispred_stage_map ++ br_mispred_stage_map ++ jalr_mispred_stage_map ++
  correct_stage_map ++ br_correct_stage_map ++ jalr_correct_stage_map

  for((key, value) <- perfCountsMap) {
    XSPerfAccumulate(key, value)
  }

  // --------------------------- Debug --------------------------------
  // XSDebug(enq_fire, p"enq! " + io.fromBpu.resp.bits.toPrintable)
  XSDebug(io.toIfu.req.fire, p"fire to ifu " + io.toIfu.req.bits.toPrintable)
  XSDebug(do_commit, p"deq! [ptr] $do_commit_ptr\n")
  XSDebug(true.B, p"[bpuPtr] $bpuPtr, [ifuPtr] $ifuPtr, [ifuWbPtr] $ifuWbPtr [commPtr] $commPtr\n")
  XSDebug(true.B, p"[in] v:${io.fromBpu.resp.valid} r:${io.fromBpu.resp.ready} " +
    p"[out] v:${io.toIfu.req.valid} r:${io.toIfu.req.ready}\n")
  XSDebug(do_commit, p"[deq info] cfiIndex: $commit_cfi, $commit_pc_bundle, target: ${Hexadecimal(commit_target)}\n")

  //   def ubtbCheck(commit: FtqEntry, predAns: Seq[PredictorAnswer], isWrong: Bool) = {
  //     commit.valids.zip(commit.pd).zip(predAns).zip(commit.takens).map {
  //       case (((valid, pd), ans), taken) =>
  //       Mux(valid && pd.isBr,
  //         isWrong ^ Mux(ans.hit.asBool,
  //           Mux(ans.taken.asBool, taken && ans.target === commitEntry.target,
  //           !taken),
  //         !taken),
  //       false.B)
  //     }
  //   }

  //   def btbCheck(commit: FtqEntry, predAns: Seq[PredictorAnswer], isWrong: Bool) = {
  //     commit.valids.zip(commit.pd).zip(predAns).zip(commit.takens).map {
  //       case (((valid, pd), ans), taken) =>
  //       Mux(valid && pd.isBr,
  //         isWrong ^ Mux(ans.hit.asBool,
  //           Mux(ans.taken.asBool, taken && ans.target === commitEntry.target,
  //           !taken),
  //         !taken),
  //       false.B)
  //     }
  //   }

  //   def tageCheck(commit: FtqEntry, predAns: Seq[PredictorAnswer], isWrong: Bool) = {
  //     commit.valids.zip(commit.pd).zip(predAns).zip(commit.takens).map {
  //       case (((valid, pd), ans), taken) =>
  //       Mux(valid && pd.isBr,
  //         isWrong ^ (ans.taken.asBool === taken),
  //       false.B)
  //     }
  //   }

  //   def loopCheck(commit: FtqEntry, predAns: Seq[PredictorAnswer], isWrong: Bool) = {
  //     commit.valids.zip(commit.pd).zip(predAns).zip(commit.takens).map {
  //       case (((valid, pd), ans), taken) =>
  //       Mux(valid && (pd.isBr) && ans.hit.asBool,
  //         isWrong ^ (!taken),
  //           false.B)
  //     }
  //   }

  //   def rasCheck(commit: FtqEntry, predAns: Seq[PredictorAnswer], isWrong: Bool) = {
  //     commit.valids.zip(commit.pd).zip(predAns).zip(commit.takens).map {
  //       case (((valid, pd), ans), taken) =>
  //       Mux(valid && pd.isRet.asBool /*&& taken*/ && ans.hit.asBool,
  //         isWrong ^ (ans.target === commitEntry.target),
  //           false.B)
  //     }
  //   }

  //   val ubtbRights = ubtbCheck(commitEntry, commitEntry.metas.map(_.ubtbAns), false.B)
  //   val ubtbWrongs = ubtbCheck(commitEntry, commitEntry.metas.map(_.ubtbAns), true.B)
  //   // btb and ubtb pred jal and jalr as well
  //   val btbRights = btbCheck(commitEntry, commitEntry.metas.map(_.btbAns), false.B)
  //   val btbWrongs = btbCheck(commitEntry, commitEntry.metas.map(_.btbAns), true.B)
  //   val tageRights = tageCheck(commitEntry, commitEntry.metas.map(_.tageAns), false.B)
  //   val tageWrongs = tageCheck(commitEntry, commitEntry.metas.map(_.tageAns), true.B)

  //   val loopRights = loopCheck(commitEntry, commitEntry.metas.map(_.loopAns), false.B)
  //   val loopWrongs = loopCheck(commitEntry, commitEntry.metas.map(_.loopAns), true.B)

  //   val rasRights = rasCheck(commitEntry, commitEntry.metas.map(_.rasAns), false.B)
  //   val rasWrongs = rasCheck(commitEntry, commitEntry.metas.map(_.rasAns), true.B)

  val perfEvents = Seq(
    ("bpu_s2_redirect        ", bpu_s2_redirect                                                             ),
    ("bpu_s3_redirect        ", bpu_s3_redirect                                                             ),
    ("bpu_to_ftq_stall       ", enq.valid && ~enq.ready                                                     ),
    ("mispredictRedirect     ", perf_redirect.valid && RedirectLevel.flushAfter === perf_redirect.bits.level),
    ("replayRedirect         ", perf_redirect.valid && RedirectLevel.flushItself(perf_redirect.bits.level)  ),
    ("predecodeRedirect      ", fromIfuRedirect.valid                                                       ),
    ("to_ifu_bubble          ", io.toIfu.req.ready && !io.toIfu.req.valid                                   ),
    ("from_bpu_real_bubble   ", !enq.valid && enq.ready && allowBpuIn                                       ),
    ("BpInstr                ", PopCount(mbpInstrs)                                                         ),
    ("BpBInstr               ", PopCount(mbpBRights | mbpBWrongs)                                           ),
    ("BpRight                ", PopCount(mbpRights)                                                         ),
    ("BpWrong                ", PopCount(mbpWrongs)                                                         ),
    ("BpBRight               ", PopCount(mbpBRights)                                                        ),
    ("BpBWrong               ", PopCount(mbpBWrongs)                                                        ),
    ("BpJRight               ", PopCount(mbpJRights)                                                        ),
    ("BpJWrong               ", PopCount(mbpJWrongs)                                                        ),
    ("BpIRight               ", PopCount(mbpIRights)                                                        ),
    ("BpIWrong               ", PopCount(mbpIWrongs)                                                        ),
    ("BpCRight               ", PopCount(mbpCRights)                                                        ),
    ("BpCWrong               ", PopCount(mbpCWrongs)                                                        ),
    ("BpRRight               ", PopCount(mbpRRights)                                                        ),
    ("BpRWrong               ", PopCount(mbpRWrongs)                                                        ),
    ("ftb_false_hit          ", PopCount(ftb_false_hit)                                                     ),
    ("ftb_hit                ", PopCount(ftb_hit)                                                           ),
  )
  generatePerfEvent()
}