package xiangshan.backend

import chisel3._
import chisel3.util._
import freechips.rocketchip.diplomacy.{LazyModule, LazyModuleImp}
import org.chipsalliance.cde.config.Parameters
import utility.SyncDataModuleTemplate
import xiangshan.HasXSParameter
import xiangshan.frontend.{FtqPtr, IfuToBackendIO}

class GPAMem(implicit p: Parameters) extends LazyModule {
  override def shouldBeInlined: Boolean = false

  lazy val module = new GPAMemImp(this)
}

class GPAMemImp(override val wrapper: GPAMem)(implicit p: Parameters) extends LazyModuleImp(wrapper) with HasXSParameter {
  val io = IO(new GPAMemIO)

  private val PageOffsetWidth = 12

  private val mem = Module (new SyncDataModuleTemplate(Vec(2, UInt(GPAddrBits.W)), FtqSize, numRead = 1, numWrite = 1, hasRen = true))

  mem.io.wen.head := io.fromIFU.gpaddrMem_wen
  mem.io.waddr.head := io.fromIFU.gpaddrMem_waddr
  mem.io.wdata.head := io.fromIFU.gpaddrMem_wdata

  mem.io.ren.get.head := io.exceptionReadAddr.valid
  mem.io.raddr.head := io.exceptionReadAddr.bits.ftqPtr.value

  private val ftqOffset = RegEnable(io.exceptionReadAddr.bits.ftqOffset, io.exceptionReadAddr.valid)

  private val gpa0base = mem.io.rdata.head.head
  private val gpa1base = mem.io.rdata.head.last
  private val gpa0 = gpa0base + Cat(ftqOffset, 0.U(instOffsetBits))
  private val gpa1 = gpa1base + Cat(ftqOffset, 0.U(instOffsetBits))

  private val gpa0basePage = getGPAPage(gpa0base)
  private val gpa0page = getGPAPage(gpa0)
  private val gpa = Mux(gpa0basePage === gpa0page, gpa0, gpa1)

  io.exceptionReadData := gpa

  def getGPAPage(vaddr: UInt): UInt = {
    require(vaddr.getWidth == GPAddrBits, s"The width of gpa should be $GPAddrBits")
    vaddr(GPAddrBits - 1, PageOffsetWidth)
  }
}

class GPAMemIO(implicit val p: Parameters) extends Bundle with HasXSParameter {
  val fromIFU = Flipped(new IfuToBackendIO())

  val exceptionReadAddr = Input(ValidIO(new Bundle {
    val ftqPtr = new FtqPtr()
    val ftqOffset = UInt(log2Up(PredictWidth).W)
  }))

  val exceptionReadData = Output(UInt(GPAddrBits.W))
}