xref: /XiangShan/src/main/scala/xiangshan/backend/issue/BypassNetwork.scala (revision 708ceed4afe43fb0ea3a52407e46b2794c573634) 
1/***************************************************************************************
2* Copyright (c) 2020-2021 Institute of Computing Technology, Chinese Academy of Sciences
3* Copyright (c) 2020-2021 Peng Cheng Laboratory
4*
5* XiangShan is licensed under Mulan PSL v2.
6* You can use this software according to the terms and conditions of the Mulan PSL v2.
7* You may obtain a copy of Mulan PSL v2 at:
8*          http://license.coscl.org.cn/MulanPSL2
9*
10* THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,
11* EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,
12* MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
13*
14* See the Mulan PSL v2 for more details.
15***************************************************************************************/
16
17package xiangshan.backend.issue
18
19import chipsalliance.rocketchip.config.Parameters
20import chisel3._
21import chisel3.util._
22import xiangshan._
23import utils._
24
25
26class BypassInfo(numWays: Int, dataBits: Int) extends Bundle {
27  val valid = Vec(numWays, Bool())
28  val data = UInt(dataBits.W)
29
30  override def cloneType: BypassInfo.this.type =
31    new BypassInfo(numWays, dataBits).asInstanceOf[this.type]
32}
33
34class BypassNetworkIO(numWays: Int, numBypass: Int, dataBits: Int) extends Bundle {
35  val hold = Input(Bool())
36  val source = Vec(numWays, Input(UInt(dataBits.W)))
37  val target = Vec(numWays, Output(UInt(dataBits.W)))
38  val bypass = Vec(numBypass, Input(new BypassInfo(numWays, dataBits)))
39
40  override def cloneType: BypassNetworkIO.this.type =
41    new BypassNetworkIO(numWays, numBypass, dataBits).asInstanceOf[this.type]
42}
43
44class BypassNetwork(numWays: Int, numBypass: Int, dataBits: Int)(implicit p: Parameters)
45  extends XSModule {
46
47  val io = IO(new BypassNetworkIO(numWays, numBypass, dataBits))
48
49  def doBypass(bypassValid: Seq[Bool], bypassData: Seq[UInt], baseData: UInt, debugIndex: Int = 0): UInt = {
50    val bypassVec = VecInit(bypassValid)
51    val target = Mux(bypassVec.asUInt.orR, Mux1H(bypassValid, bypassData), baseData)
52
53    XSError(PopCount(bypassVec) > 1.U, p"bypass mask ${Binary(bypassVec.asUInt)} is not one-hot\n")
54    bypassVec.zipWithIndex.map { case (m, i) =>
55      XSDebug(bypassVec(i), p"target($debugIndex) bypassed from $i:0x${Hexadecimal(bypassData(i))}\n")
56    }
57
58    target
59  }
60
61}
62
63// Bypass at the right: RegNext(data) and compute the bypassed data at the next clock cycle
64class BypassNetworkRight(numWays: Int, numBypass: Int, dataBits: Int)(implicit p: Parameters)
65  extends BypassNetwork(numWays, numBypass, dataBits) {
66
67  val target_reg = Reg(Vec(numWays, UInt(dataBits.W)))
68  val bypass_reg = Reg(Vec(numBypass, new BypassInfo(numWays, dataBits)))
69
70  when (io.hold) {
71    target_reg := io.target
72    bypass_reg.map(_.valid.map(_ := false.B))
73  }.otherwise {
74    target_reg := io.source
75    for ((by_reg, by_io) <- bypass_reg.zip(io.bypass)) {
76      by_reg.data := by_io.data
77      by_reg.valid := by_io.valid
78    }
79  }
80
81  // bypass data to target
82  for (i <- 0 until numWays) {
83    io.target(i) := doBypass(bypass_reg.map(_.valid(i)), bypass_reg.map(_.data), target_reg(i))
84  }
85
86}
87
88// Bypass at the left: compute the bypassed data and RegNext(bypassed_data)
89class BypassNetworkLeft(numWays: Int, numBypass: Int, dataBits: Int)(implicit p: Parameters)
90  extends BypassNetwork(numWays, numBypass, dataBits) {
91
92  val bypassedData = Reg(io.target.cloneType)
93
94  when (!io.hold) {
95    for ((by, i) <- bypassedData.zipWithIndex) {
96      by := doBypass(io.bypass.map(_.valid(i)), io.bypass.map(_.data), io.source(i))
97    }
98  }
99
100  io.target := bypassedData
101
102}
103
104object BypassNetwork {
105  def apply(numWays: Int, numBypass: Int, dataBits: Int, optFirstStage: Boolean)(implicit p: Parameters) = {
106    Module(new BypassNetworkLeft(numWays, numBypass, dataBits))
107  }
108}
109