Upgrade to Chisel 6 (#64)

* Bump to chisel 6.2.0

* Rename Const variables to Consts

Const is an object in chisel6: https://www.chisel-lang.org/api/latest/chisel3/Const$.html

* Use single-threaded emulation by default

* Use c++14 to pass the verilator check

Verilator 5.020 (released 2024/01/01) requires C++14: https://verilator.org/guide/latest/changes.html.

Makefile

@@ -4,7 +4,7 @@ base_dir   = $(abspath .)
 src_dir    = $(base_dir)/src/main
 gen_dir    = $(base_dir)/generated-src
 out_dir    = $(base_dir)/outputs
-nproc      = $(shell nproc --ignore 1)
+threads   ?= 1
 
 SBT       = sbt
 SBT_FLAGS = -ivy $(base_dir)/.ivy2
@@ -17,11 +17,11 @@ compile: $(gen_dir)/Tile.sv
 $(gen_dir)/Tile.sv: $(wildcard $(src_dir)/scala/*.scala)
 	$(SBT) $(SBT_FLAGS) "run --target-dir=$(gen_dir)"
 
-CXXFLAGS += -std=c++11 -Wall -Wno-unused-variable
+CXXFLAGS += -std=c++14 -Wall -Wno-unused-variable
 
 # compile verilator
 VERILATOR = verilator --cc --exe
-VERILATOR_FLAGS = --assert -Wno-STMTDLY -O3 --trace --threads $(nproc)\
+VERILATOR_FLAGS = --assert -Wno-STMTDLY -O3 --trace --threads $(threads)\
 	--top-module Tile -Mdir $(gen_dir)/VTile.csrc \
 	-CFLAGS "$(CXXFLAGS) -include $(gen_dir)/VTile.csrc/VTile.h" 
 

build.sbt

@@ -2,8 +2,8 @@ ThisBuild / scalaVersion     := "2.13.7"
 ThisBuild / version          := "2.5.0"
 ThisBuild / organization     := "edu.berkeley.cs"
 
-val chiselVersion = "5.0.0"
-val chiseltestVersion = "5.0.2"
+val chiselVersion = "6.2.0"
+val chiseltestVersion = "6.0.0"
 
 lazy val root = (project in file("."))
   .settings(

src/main/scala/mini/CSR.scala

@@ -159,7 +159,7 @@ class CSR(val xlen: Int) extends Module {
   val FS = 0.U(2.W)
   val SD = 0.U(1.W)
   val mstatus = Cat(SD, 0.U((xlen - 23).W), VM, MPRV, XS, FS, PRV3, IE3, PRV2, IE2, PRV1, IE1, PRV, IE)
-  val mtvec = Const.PC_EVEC.U(xlen.W)
+  val mtvec = Consts.PC_EVEC.U(xlen.W)
   val mtdeleg = 0x0.U(xlen.W)
 
   // interrupt registers

src/main/scala/mini/Datapath.scala

@@ -6,7 +6,7 @@ import chisel3._
 import chisel3.util._
 import chisel3.experimental.BundleLiterals._
 
-object Const {
+object Consts {
   val PC_START = 0x200
   val PC_EVEC = 0x100
 }
@@ -76,7 +76,7 @@ class Datapath(val conf: CoreConfig) extends Module {
     */
   val started = RegNext(reset.asBool)
   val stall = !io.icache.resp.valid || !io.dcache.resp.valid
-  val pc = RegInit(Const.PC_START.U(conf.xlen.W) - 4.U(conf.xlen.W))
+  val pc = RegInit(Consts.PC_START.U(conf.xlen.W) - 4.U(conf.xlen.W))
   // Next Program Counter
   val next_pc = MuxCase(
     pc + 4.U,

src/test/scala/mini/CSRTests.scala

@@ -65,7 +65,7 @@ class CSRTester(c: => CSR, trace: Boolean = false) extends BasicTester with Test
       addr -> RegInit(
         if (addr == CSR.mcpuid.litValue) (BigInt(1) << ('I' - 'A') | BigInt(1) << ('U' - 'A')).U(xlen.W)
         else if (addr == CSR.mstatus.litValue) (CSR.PRV_M.litValue << 4 | CSR.PRV_M.litValue << 1).U(xlen.W)
-        else if (addr == CSR.mtvec.litValue) Const.PC_EVEC.U(xlen.W)
+        else if (addr == CSR.mtvec.litValue) Consts.PC_EVEC.U(xlen.W)
         else 0.U(xlen.W)
       )
     }

src/test/scala/mini/DatapathTests.scala

@@ -42,10 +42,10 @@ class DatapathTester(datapath: => Datapath, testType: DatapathTest) extends Basi
 
   switch(state) {
     is(sInit) {
-      (0 until Const.PC_START by 4).foreach { addr =>
-        mem((addr / 4).U) := (if (addr == Const.PC_EVEC + (3 << 6)) fin else nop)
+      (0 until Consts.PC_START by 4).foreach { addr =>
+        mem((addr / 4).U) := (if (addr == Consts.PC_EVEC + (3 << 6)) fin else nop)
       }
-      mem((Const.PC_START / (xlen / 8)).U + cntr) := VecInit(insts)(cntr)
+      mem((Consts.PC_START / (xlen / 8)).U + cntr) := VecInit(insts)(cntr)
       when(done) { state := sRun }
     }
     is(sRun) {