Merge branch 'rocc-fpu-port'

rocket/src/main/scala/arbiter.scala

@@ -5,6 +5,7 @@ package rocket
 import Chisel._
 import uncore._
 import cde.{Parameters, Field}
+import junctions.ParameterizedBundle
 
 class HellaCacheArbiter(n: Int)(implicit p: Parameters) extends Module
 {
@@ -53,3 +54,51 @@ class HellaCacheArbiter(n: Int)(implicit p: Parameters) extends Module
     io.requestor(i).replay_next.bits := io.mem.replay_next.bits >> log2Up(n)
   }
 }
+
+class InOrderArbiter[T <: Data, U <: Data](reqTyp: T, respTyp: U, n: Int)
+    (implicit p: Parameters) extends Module {
+  val io = new Bundle {
+    val in_req = Vec(n, Decoupled(reqTyp)).flip
+    val in_resp = Vec(n, Decoupled(respTyp))
+    val out_req = Decoupled(reqTyp)
+    val out_resp = Decoupled(respTyp).flip
+  }
+
+  if (n > 1) {
+    val route_q = Module(new Queue(UInt(width = log2Up(n)), 2))
+    val req_arb = Module(new RRArbiter(reqTyp, n))
+    req_arb.io.in <> io.in_req
+
+    val req_helper = DecoupledHelper(
+      req_arb.io.out.valid,
+      route_q.io.enq.ready,
+      io.out_req.ready)
+
+    io.out_req.bits := req_arb.io.out.bits
+    io.out_req.valid := req_helper.fire(io.out_req.ready)
+
+    route_q.io.enq.bits := req_arb.io.chosen
+    route_q.io.enq.valid := req_helper.fire(route_q.io.enq.ready)
+
+    req_arb.io.out.ready := req_helper.fire(req_arb.io.out.valid)
+
+    val resp_sel = route_q.io.deq.bits
+    val resp_ready = io.in_resp(resp_sel).ready
+    val resp_helper = DecoupledHelper(
+      resp_ready,
+      route_q.io.deq.valid,
+      io.out_resp.valid)
+
+    val resp_valid = resp_helper.fire(resp_ready)
+    for (i <- 0 until n) {
+      io.in_resp(i).bits := io.out_resp.bits
+      io.in_resp(i).valid := resp_valid && resp_sel === UInt(i)
+    }
+
+    route_q.io.deq.ready := resp_helper.fire(route_q.io.deq.valid)
+    io.out_resp.ready := resp_helper.fire(io.out_resp.valid)
+  } else {
+    io.out_req <> io.in_req.head
+    io.in_resp.head <> io.out_resp
+  }
+}

rocket/src/main/scala/fpu.scala

@@ -163,9 +163,9 @@ class FPUIO extends Bundle {
   val sboard_set = Bool(OUTPUT)
   val sboard_clr = Bool(OUTPUT)
   val sboard_clra = UInt(OUTPUT, 5)
-}
 
-class CtrlFPUIO extends Bundle {
+  val cp_req = Decoupled(new FPInput()).flip //cp doesn't pay attn to kill sigs
+  val cp_resp = Decoupled(new FPResult())
 }
 
 class FPResult extends Bundle
@@ -439,18 +439,27 @@ class FPU(implicit p: Parameters) extends CoreModule()(p) {
   val io = new FPUIO
 
   val ex_reg_valid = Reg(next=io.valid, init=Bool(false))
+  val req_valid = ex_reg_valid || io.cp_req.valid
   val ex_reg_inst = RegEnable(io.inst, io.valid)
-  val mem_reg_valid = Reg(next=ex_reg_valid && !io.killx, init=Bool(false))
+  val ex_cp_valid = io.cp_req.valid && !ex_reg_valid
+  val mem_reg_valid = Reg(next=ex_reg_valid && !io.killx || ex_cp_valid, init=Bool(false))
   val mem_reg_inst = RegEnable(ex_reg_inst, ex_reg_valid)
-  val killm = io.killm || io.nack_mem
+  val mem_cp_valid = Reg(next=ex_cp_valid, init=Bool(false))
-  val wb_reg_valid = Reg(next=mem_reg_valid && !killm, init=Bool(false))
+  val killm = (io.killm || io.nack_mem) && !mem_cp_valid
+  val wb_reg_valid = Reg(next=mem_reg_valid && (!killm || mem_cp_valid), init=Bool(false))
+  val wb_cp_valid = Reg(next=mem_cp_valid, init=Bool(false))
 
   val fp_decoder = Module(new FPUDecoder)
   fp_decoder.io.inst := io.inst
 
+  val cp_ctrl = new FPUCtrlSigs
+  cp_ctrl <> io.cp_req.bits
+  io.cp_resp.valid := Bool(false)
+  io.cp_resp.bits.data := UInt(0)
+
   val id_ctrl = fp_decoder.io.sigs
-  val ex_ctrl = RegEnable(id_ctrl, io.valid)
+  val ex_ctrl = Mux(ex_reg_valid, RegEnable(id_ctrl, io.valid), cp_ctrl)
-  val mem_ctrl = RegEnable(ex_ctrl, ex_reg_valid)
+  val mem_ctrl = RegEnable(ex_ctrl, req_valid)
   val wb_ctrl = RegEnable(mem_ctrl, mem_reg_valid)
 
   // load response
@@ -488,35 +497,43 @@ class FPU(implicit p: Parameters) extends CoreModule()(p) {
   val ex_rs1::ex_rs2::ex_rs3::Nil = Seq(ex_ra1, ex_ra2, ex_ra3).map(regfile(_))
   val ex_rm = Mux(ex_reg_inst(14,12) === Bits(7), io.fcsr_rm, ex_reg_inst(14,12))
 
+  val cp_rs1 = io.cp_req.bits.in1
+  val cp_rs2 = Mux(io.cp_req.bits.swap23, io.cp_req.bits.in3, io.cp_req.bits.in2)
+  val cp_rs3 = Mux(io.cp_req.bits.swap23, io.cp_req.bits.in2, io.cp_req.bits.in3)
+
   val req = Wire(new FPInput)
   req := ex_ctrl
-  req.rm := ex_rm
+  req.rm := Mux(ex_reg_valid, ex_rm, io.cp_req.bits.rm)
-  req.in1 := ex_rs1
+  req.in1 := Mux(ex_reg_valid, ex_rs1, cp_rs1)
-  req.in2 := ex_rs2
+  req.in2 := Mux(ex_reg_valid, ex_rs2, cp_rs2)
-  req.in3 := ex_rs3
+  req.in3 := Mux(ex_reg_valid, ex_rs3, cp_rs3)
-  req.typ := ex_reg_inst(21,20)
+  req.typ := Mux(ex_reg_valid, ex_reg_inst(21,20), io.cp_req.bits.typ)
 
   val sfma = Module(new FPUFMAPipe(p(SFMALatency), 8, 24))
-  sfma.io.in.valid := ex_reg_valid && ex_ctrl.fma && ex_ctrl.single
+  sfma.io.in.valid := req_valid && ex_ctrl.fma && ex_ctrl.single
   sfma.io.in.bits := req
 
   val dfma = Module(new FPUFMAPipe(p(DFMALatency), 11, 53))
-  dfma.io.in.valid := ex_reg_valid && ex_ctrl.fma && !ex_ctrl.single
+  dfma.io.in.valid := req_valid && ex_ctrl.fma && !ex_ctrl.single
   dfma.io.in.bits := req
 
   val fpiu = Module(new FPToInt)
-  fpiu.io.in.valid := ex_reg_valid && (ex_ctrl.toint || ex_ctrl.div || ex_ctrl.sqrt || ex_ctrl.cmd === FCMD_MINMAX)
+  fpiu.io.in.valid := req_valid && (ex_ctrl.toint || ex_ctrl.div || ex_ctrl.sqrt || ex_ctrl.cmd === FCMD_MINMAX)
   fpiu.io.in.bits := req
   io.store_data := fpiu.io.out.bits.store
   io.toint_data := fpiu.io.out.bits.toint
+  when(fpiu.io.out.valid && mem_cp_valid && mem_ctrl.toint){
+    io.cp_resp.bits.data := fpiu.io.out.bits.toint
+    io.cp_resp.valid := Bool(true)
+  }
 
   val ifpu = Module(new IntToFP(3))
-  ifpu.io.in.valid := ex_reg_valid && ex_ctrl.fromint
+  ifpu.io.in.valid := req_valid && ex_ctrl.fromint
   ifpu.io.in.bits := req
-  ifpu.io.in.bits.in1 := io.fromint_data
+  ifpu.io.in.bits.in1 := Mux(ex_reg_valid, io.fromint_data, cp_rs1)
 
   val fpmu = Module(new FPToFP(2))
-  fpmu.io.in.valid := ex_reg_valid && ex_ctrl.fastpipe
+  fpmu.io.in.valid := req_valid && ex_ctrl.fastpipe
   fpmu.io.in.bits := req
   fpmu.io.lt := fpiu.io.out.bits.lt
 
@@ -546,8 +563,8 @@ class FPU(implicit p: Parameters) extends CoreModule()(p) {
   val wen = Reg(init=Bits(0, maxLatency-1))
   val winfo = Reg(Vec(Bits(), maxLatency-1))
   val mem_wen = mem_reg_valid && (mem_ctrl.fma || mem_ctrl.fastpipe || mem_ctrl.fromint)
-  val write_port_busy = RegEnable(mem_wen && (memLatencyMask & latencyMask(ex_ctrl, 1)).orR || (wen & latencyMask(ex_ctrl, 0)).orR, ex_reg_valid)
+  val write_port_busy = RegEnable(mem_wen && (memLatencyMask & latencyMask(ex_ctrl, 1)).orR || (wen & latencyMask(ex_ctrl, 0)).orR, req_valid)
-  val mem_winfo = Cat(pipeid(mem_ctrl), mem_ctrl.single, mem_reg_inst(11,7)) //single only used for debugging
+  val mem_winfo = Cat(mem_cp_valid, pipeid(mem_ctrl), mem_ctrl.single, mem_reg_inst(11,7)) //single only used for debugging
 
   for (i <- 0 until maxLatency-2) {
     when (wen(i+1)) { winfo(i) := winfo(i+1) }
@@ -566,9 +583,10 @@ class FPU(implicit p: Parameters) extends CoreModule()(p) {
 
   val waddr = Mux(divSqrt_wen, divSqrt_waddr, winfo(0)(4,0).toUInt)
   val wsrc = (winfo(0) >> 6)
+  val wcp = winfo(0)(6+log2Up(pipes.size))
   val wdata = Mux(divSqrt_wen, divSqrt_wdata, Vec(pipes.map(_.res.data))(wsrc))
   val wexc = Vec(pipes.map(_.res.exc))(wsrc)
-  when (wen(0) || divSqrt_wen) {
+  when ((!wcp && wen(0)) || divSqrt_wen) {
     regfile(waddr) := wdata
     if (enableCommitLog) {
       val wdata_unrec_s = hardfloat.fNFromRecFN(8, 24, wdata(64,0))
@@ -578,6 +596,11 @@ class FPU(implicit p: Parameters) extends CoreModule()(p) {
         Mux(wb_single, Cat(UInt(0,32), wdata_unrec_s), wdata_unrec_d))
     }
   }
+  when (wcp && wen(0)) {
+    io.cp_resp.bits.data := wdata
+    io.cp_resp.valid := Bool(true)
+  }
+  io.cp_req.ready := !ex_reg_valid
 
   val wb_toint_valid = wb_reg_valid && wb_ctrl.toint
   val wb_toint_exc = RegEnable(fpiu.io.out.bits.exc, mem_ctrl.toint)
@@ -592,8 +615,8 @@ class FPU(implicit p: Parameters) extends CoreModule()(p) {
   io.nack_mem := units_busy || write_port_busy || divSqrt_in_flight
   io.dec <> fp_decoder.io.sigs
   def useScoreboard(f: ((Pipe, Int)) => Bool) = pipes.zipWithIndex.filter(_._1.lat > 3).map(x => f(x)).fold(Bool(false))(_||_)
-  io.sboard_set := wb_reg_valid && Reg(next=useScoreboard(_._1.cond(mem_ctrl)) || mem_ctrl.div || mem_ctrl.sqrt)
+  io.sboard_set := wb_reg_valid && !wb_cp_valid && Reg(next=useScoreboard(_._1.cond(mem_ctrl)) || mem_ctrl.div || mem_ctrl.sqrt)
-  io.sboard_clr := divSqrt_wen || (wen(0) && useScoreboard(x => wsrc === UInt(x._2)))
+  io.sboard_clr := !wb_cp_valid && (divSqrt_wen || (wen(0) && useScoreboard(x => wsrc === UInt(x._2))))
   io.sboard_clra := waddr
   // we don't currently support round-max-magnitude (rm=4)
   io.illegal_rm := ex_rm(2) && ex_ctrl.round

rocket/src/main/scala/frontend.scala

@@ -46,13 +46,14 @@ class Frontend(implicit p: Parameters) extends CoreModule()(p) with HasL1CachePa
   val s2_btb_resp_valid = Reg(init=Bool(false))
   val s2_btb_resp_bits = Reg(btb.io.resp.bits)
   val s2_xcpt_if = Reg(init=Bool(false))
+  val icbuf = Module(new Queue(new ICacheResp, 1, pipe=true))
 
   val msb = vaddrBits-1
   val lsb = log2Up(fetchWidth*coreInstBytes)
   val btbTarget = Cat(btb.io.resp.bits.target(msb), btb.io.resp.bits.target)
   val ntpc_0 = s1_pc + UInt(coreInstBytes*fetchWidth)
   val ntpc = Cat(s1_pc(msb) & ntpc_0(msb), ntpc_0(msb,lsb), Bits(0,lsb)) // unsure
-  val icmiss = s2_valid && !icache.io.resp.valid
+  val icmiss = s2_valid && !icbuf.io.deq.valid
   val predicted_npc = Mux(btb.io.resp.bits.taken, btbTarget, ntpc)
   val npc = Mux(icmiss, s2_pc, predicted_npc).toUInt
   val s0_same_block = !icmiss && !io.cpu.req.valid && !btb.io.resp.bits.taken && ((ntpc & rowBytes) === (s1_pc & rowBytes))
@@ -100,14 +101,17 @@ class Frontend(implicit p: Parameters) extends CoreModule()(p) with HasL1CachePa
     icmiss || io.ptw.invalidate
   icache.io.resp.ready := !stall && !s1_same_block
 
-  io.cpu.resp.valid := s2_valid && (s2_xcpt_if || icache.io.resp.valid)
+  io.cpu.resp.valid := s2_valid && (s2_xcpt_if || icbuf.io.deq.valid)
   io.cpu.resp.bits.pc := s2_pc
   io.cpu.npc := Mux(io.cpu.req.valid, io.cpu.req.bits.pc, npc)
 
+  icbuf.io.enq <> icache.io.resp
+  icbuf.io.deq.ready := !stall && !s1_same_block
+
   require(fetchWidth * coreInstBytes <= rowBytes)
   val fetch_data =
-    if (fetchWidth * coreInstBytes == rowBytes) icache.io.resp.bits.datablock
+    if (fetchWidth * coreInstBytes == rowBytes) icbuf.io.deq.bits.datablock
-    else icache.io.resp.bits.datablock >> (s2_pc(log2Up(rowBytes)-1,log2Up(fetchWidth*coreInstBytes)) << log2Up(fetchWidth*coreInstBits))
+    else icbuf.io.deq.bits.datablock >> (s2_pc(log2Up(rowBytes)-1,log2Up(fetchWidth*coreInstBytes)) << log2Up(fetchWidth*coreInstBits))
 
   for (i <- 0 until fetchWidth) {
     io.cpu.resp.bits.data(i) := fetch_data(i*coreInstBits+coreInstBits-1, i*coreInstBits)

rocket/src/main/scala/icache.scala

@@ -40,9 +40,8 @@ class ICache(implicit p: Parameters) extends CoreModule()(p) with HasL1CachePara
   val stall = !io.resp.ready
   val rdy = Wire(Bool())
 
-  val s2_valid = Reg(init=Bool(false))
+  val refill_addr = Reg(UInt(width = paddrBits))
-  val s2_addr = Reg(UInt(width = paddrBits))
+  val s1_any_tag_hit = Bool()
-  val s2_any_tag_hit = Wire(Bool())
 
   val s1_valid = Reg(init=Bool(false))
   val s1_pgoff = Reg(UInt(width = pgIdxBits))
@@ -57,91 +56,85 @@ class ICache(implicit p: Parameters) extends CoreModule()(p) with HasL1CachePara
     s1_pgoff := io.req.bits.idx
   }
 
-  s2_valid := s1_valid && rdy && !io.req.bits.kill || io.resp.valid && stall
+  val out_valid = s1_valid && !io.req.bits.kill && state === s_ready
-  when (s1_valid && rdy && !stall) {
+  val s1_idx = s1_addr(untagBits-1,blockOffBits)
-    s2_addr := s1_addr
+  val s1_offset = s1_addr(blockOffBits-1,0)
-  }
+  val s1_hit = out_valid && s1_any_tag_hit
+  val s1_miss = out_valid && !s1_any_tag_hit
+  rdy := state === s_ready && !s1_miss
 
-  val s2_tag = s2_addr(tagBits+untagBits-1,untagBits)
+  when (s1_valid && state === s_ready && s1_miss) {
-  val s2_idx = s2_addr(untagBits-1,blockOffBits)
+    refill_addr := s1_addr
-  val s2_offset = s2_addr(blockOffBits-1,0)
+  }
-  val s2_hit = s2_valid && s2_any_tag_hit
+  val refill_tag = refill_addr(tagBits+untagBits-1,untagBits)
-  val s2_miss = s2_valid && !s2_any_tag_hit
-  rdy := state === s_ready && !s2_miss
 
   val narrow_grant = FlowThroughSerializer(io.mem.grant, refillCyclesPerBeat)
   val (refill_cnt, refill_wrap) = Counter(narrow_grant.fire(), refillCycles) //TODO Zero width wire
   val refill_done = state === s_refill && refill_wrap
   narrow_grant.ready := Bool(true)
 
-  val repl_way = if (isDM) UInt(0) else LFSR16(s2_miss)(log2Up(nWays)-1,0)
+  val repl_way = if (isDM) UInt(0) else LFSR16(s1_miss)(log2Up(nWays)-1,0)
   val entagbits = code.width(tagBits)
   val tag_array = SeqMem(Vec(Bits(width = entagbits), nWays), nSets)
   val tag_rdata = tag_array.read(s0_pgoff(untagBits-1,blockOffBits), !refill_done && s0_valid)
   when (refill_done) {
-    val tag = code.encode(s2_tag).toUInt
+    val tag = code.encode(refill_tag).toUInt
-    tag_array.write(s2_idx, Vec.fill(nWays)(tag), Vec.tabulate(nWays)(repl_way === _))
+    tag_array.write(s1_idx, Vec.fill(nWays)(tag), Vec.tabulate(nWays)(repl_way === _))
   }
 
   val vb_array = Reg(init=Bits(0, nSets*nWays))
   when (refill_done && !invalidated) {
-    vb_array := vb_array.bitSet(Cat(repl_way, s2_idx), Bool(true))
+    vb_array := vb_array.bitSet(Cat(repl_way, s1_idx), Bool(true))
   }
   when (io.invalidate) {
     vb_array := Bits(0)
     invalidated := Bool(true)
   }
-  val s2_disparity = Wire(Vec(Bool(), nWays))
+  val s1_disparity = Vec.fill(nWays){Bool()}
   for (i <- 0 until nWays)
-    when (s2_valid && s2_disparity(i)) { vb_array := vb_array.bitSet(Cat(UInt(i), s2_idx), Bool(false)) }
+    when (s1_valid && s1_disparity(i)) { vb_array := vb_array.bitSet(Cat(UInt(i), s1_idx), Bool(false)) }
 
-  val s1_tag_match = Wire(Vec(Bool(), nWays))
+  val s1_tag_match = Vec.fill(nWays){Bool()}
-  val s2_tag_hit = Wire(Vec(Bool(), nWays))
+  val s1_tag_hit = Vec.fill(nWays){Bool()}
-  val s2_dout = Reg(Vec(Bits(width = code.width(rowBits)), nWays))
+  val s1_dout = Vec.fill(nWays){(Bits())}
 
   for (i <- 0 until nWays) {
     val s1_vb = !io.invalidate && vb_array(Cat(UInt(i), s1_pgoff(untagBits-1,blockOffBits))).toBool
-    val s2_vb = Reg(Bool())
-    val s2_tag_disparity = Reg(Bool())
-    val s2_tag_match = Reg(Bool())
     val tag_out = tag_rdata(i)
+    val s1_tag_disparity = code.decode(tag_out).error
     when (s1_valid && rdy && !stall) {
-      s2_vb := s1_vb
-      s2_tag_disparity := code.decode(tag_out).error
-      s2_tag_match := s1_tag_match(i)
     }
     s1_tag_match(i) := tag_out(tagBits-1,0) === s1_tag
-    s2_tag_hit(i) := s2_vb && s2_tag_match
+    s1_tag_hit(i) := s1_vb && s1_tag_match(i)
-    s2_disparity(i) := s2_vb && (s2_tag_disparity || code.decode(s2_dout(i)).error)
+    s1_disparity(i) := s1_vb && (s1_tag_disparity || code.decode(s1_dout(i)).error)
   }
-  s2_any_tag_hit := s2_tag_hit.reduceLeft(_||_) && !s2_disparity.reduceLeft(_||_)
+  s1_any_tag_hit := s1_tag_hit.reduceLeft(_||_) && !s1_disparity.reduceLeft(_||_)
 
   for (i <- 0 until nWays) {
     val data_array = SeqMem(Bits(width = code.width(rowBits)), nSets*refillCycles)
     val wen = narrow_grant.valid && repl_way === UInt(i)
     when (wen) {
       val e_d = code.encode(narrow_grant.bits.data).toUInt
-      if(refillCycles > 1) data_array.write(Cat(s2_idx, refill_cnt), e_d)
+      if(refillCycles > 1) data_array.write(Cat(s1_idx, refill_cnt), e_d)
-      else data_array.write(s2_idx, e_d)
+      else data_array.write(s1_idx, e_d)
     }
     val s0_raddr = s0_pgoff(untagBits-1,blockOffBits-(if(refillCycles > 1) refill_cnt.getWidth else 0))
     val s1_rdata = data_array.read(s0_raddr, !wen && s0_valid)
     // if s1_tag_match is critical, replace with partial tag check
-    when (s1_valid && rdy && !stall && (Bool(isDM) || s1_tag_match(i))) { s2_dout(i) := s1_rdata }
+    s1_dout(i) := 0
+    when (s1_valid && rdy && !stall && (Bool(isDM) || s1_tag_match(i))) { s1_dout(i) := s1_rdata }
   }
-  val s2_dout_word = s2_dout.map(x => (x >> (s2_offset(log2Up(rowBytes)-1,log2Up(coreInstBytes)) << log2Up(coreInstBits)))(coreInstBits-1,0))
+  io.resp.bits.datablock := Mux1H(s1_tag_hit, s1_dout)
-  io.resp.bits.data := Mux1H(s2_tag_hit, s2_dout_word)
-  io.resp.bits.datablock := Mux1H(s2_tag_hit, s2_dout)
 
   // output signals
-  io.resp.valid := s2_hit
+  io.resp.valid := s1_hit
   io.mem.acquire.valid := (state === s_request)
-  io.mem.acquire.bits := GetBlock(addr_block = s2_addr >> blockOffBits)
+  io.mem.acquire.bits := GetBlock(addr_block = refill_addr >> blockOffBits)
 
   // control state machine
   switch (state) {
     is (s_ready) {
-      when (s2_miss) { state := s_request }
+      when (s1_miss) { state := s_request }
       invalidated := Bool(false)
     }
     is (s_request) {

rocket/src/main/scala/rocc.scala

@@ -47,6 +47,8 @@ class RoCCInterface(implicit p: Parameters) extends Bundle {
   val iptw = new TLBPTWIO
   val dptw = new TLBPTWIO
   val pptw = new TLBPTWIO
+  val fpu_req = Decoupled(new FPInput)
+  val fpu_resp = Decoupled(new FPResult).flip
   val exception = Bool(INPUT)
 }
 

rocket/src/main/scala/tile.scala

@@ -13,13 +13,15 @@ case object BuildRoCC extends Field[Seq[RoccParameters]]
 case class RoccParameters(
   opcodes: OpcodeSet,
   generator: Parameters => RoCC,
-  nMemChannels: Int = 1)
+  nMemChannels: Int = 1,
+  useFPU: Boolean = false)
 
 abstract class Tile(resetSignal: Bool = null)
                    (implicit p: Parameters) extends Module(_reset = resetSignal) {
   val buildRocc = p(BuildRoCC)
   val usingRocc = !buildRocc.isEmpty
   val nRocc = buildRocc.size
+  val nFPUPorts = buildRocc.filter(_.useFPU).size
   val nDCachePorts = 2 + nRocc
   val nPTWPorts = 2 + 3 * nRocc
   val nCachedTileLinkPorts = 1
@@ -53,8 +55,8 @@ class RocketTile(resetSignal: Bool = null)(implicit p: Parameters) extends Tile(
   icache.io.cpu <> core.io.imem
   core.io.ptw <> ptw.io.dpath
 
-  //If so specified, build an FPU module and wire it in
+  val fpuOpt = if (p(UseFPU)) Some(Module(new FPU)) else None
-  if (p(UseFPU)) core.io.fpu <> Module(new FPU()(p)).io
+  fpuOpt.foreach(fpu => core.io.fpu <> fpu.io)
 
    // Connect the caches and ROCC to the outer memory system
   io.cached.head <> dcache.io.mem
@@ -87,10 +89,32 @@ class RocketTile(resetSignal: Bool = null)(implicit p: Parameters) extends Tile(
       rocc
     }
 
+    if (nFPUPorts > 0) {
+      fpuOpt.foreach { fpu =>
+        val fpArb = Module(new InOrderArbiter(new FPInput, new FPResult, nFPUPorts))
+        val fp_roccs = roccs.zip(buildRocc)
+          .filter { case (_, params) => params.useFPU }
+          .map { case (rocc, _) => rocc.io }
+        fpArb.io.in_req <> fp_roccs.map(_.fpu_req)
+        fp_roccs.zip(fpArb.io.in_resp).foreach {
+          case (rocc, fpu_resp) => rocc.fpu_resp <> fpu_resp
+        }
+        fpu.io.cp_req <> fpArb.io.out_req
+        fpArb.io.out_resp <> fpu.io.cp_resp
+      }
+    }
+
     core.io.rocc.busy := cmdRouter.io.busy || roccs.map(_.io.busy).reduce(_ || _)
     core.io.rocc.interrupt := roccs.map(_.io.interrupt).reduce(_ || _)
     respArb.io.in <> roccs.map(rocc => Queue(rocc.io.resp))
 
     roccs.flatMap(_.io.dmem) :+ iMemArb.io.out
   } else { Seq(icache.io.mem) })
+
+  if (!usingRocc || nFPUPorts == 0) {
+    fpuOpt.foreach { fpu =>
+      fpu.io.cp_req.valid := Bool(false)
+      fpu.io.cp_resp.ready := Bool(false)
+    }
+  }
 }