xref: /XiangShan/src/main/scala/xiangshan/backend/fu/util/CSA.scala (revision c6d439803a044ea209139672b25e35fe8d7f4aa0) 
1/***************************************************************************************
2* Copyright (c) 2020-2021 Institute of Computing Technology, Chinese Academy of Sciences
3*
4* XiangShan is licensed under Mulan PSL v2.
5* You can use this software according to the terms and conditions of the Mulan PSL v2.
6* You may obtain a copy of Mulan PSL v2 at:
7*          http://license.coscl.org.cn/MulanPSL2
8*
9* THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,
10* EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,
11* MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
12*
13* See the Mulan PSL v2 for more details.
14***************************************************************************************/
15
16package xiangshan.backend.fu.util
17
18import chisel3._
19import chisel3.util._
20
21abstract class CarrySaveAdderMToN(m: Int, n: Int)(len: Int) extends Module{
22  val io = IO(new Bundle() {
23    val in = Input(Vec(m, UInt(len.W)))
24    val out = Output(Vec(n, UInt(len.W)))
25  })
26}
27
28class CSA2_2(len: Int) extends CarrySaveAdderMToN(2, 2)(len) {
29  val temp = Wire(Vec(len, UInt(2.W)))
30  for((t, i) <- temp.zipWithIndex){
31    val (a, b) = (io.in(0)(i), io.in(1)(i))
32    val sum = a ^ b
33    val cout = a & b
34    t := Cat(cout, sum)
35  }
36  io.out.zipWithIndex.foreach({case(x, i) => x := Cat(temp.reverse map(_(i)))})
37}
38
39class CSA3_2(len: Int) extends CarrySaveAdderMToN(3, 2)(len){
40  val temp = Wire(Vec(len, UInt(2.W)))
41  for((t, i) <- temp.zipWithIndex){
42    val (a, b, cin) = (io.in(0)(i), io.in(1)(i), io.in(2)(i))
43    val a_xor_b = a ^ b
44    val a_and_b = a & b
45    val sum = a_xor_b ^ cin
46    val cout = a_and_b | (a_xor_b & cin)
47    t := Cat(cout, sum)
48  }
49  io.out.zipWithIndex.foreach({case(x, i) => x := Cat(temp.reverse map(_(i)))})
50}
51
52class CSA5_3(len: Int)extends CarrySaveAdderMToN(5, 3)(len){
53  val FAs = Array.fill(2)(Module(new CSA3_2(len)))
54  FAs(0).io.in := io.in.take(3)
55  FAs(1).io.in := VecInit(FAs(0).io.out(0), io.in(3), io.in(4))
56  io.out := VecInit(FAs(1).io.out(0), FAs(0).io.out(1), FAs(1).io.out(1))
57}
58
59class C22 extends CSA2_2(1)
60class C32 extends CSA3_2(1)
61class C53 extends CSA5_3(1)
62
63