Support removing the nonstandard CEASE from rocket

(cherry picked from commit 956a1ff)

src/main/scala/rocket/IDecode.scala

@@ -118,7 +118,6 @@ class IDecode(aluFn: ALUFN = ALUFN())(implicit val p: Parameters) extends Decode
     EBREAK->    List(Y,N,N,N,N,N,N,X,N,N,N,N,A2_X,   A1_X,   IMM_X, DW_X,  aluFn.FN_X,     N,M_X,        N,N,N,N,N,N,N,CSR.I,N,N,N,N),
     MRET->      List(Y,N,N,N,N,N,N,X,N,N,N,N,A2_X,   A1_X,   IMM_X, DW_X,  aluFn.FN_X,     N,M_X,        N,N,N,N,N,N,N,CSR.I,N,N,N,N),
     WFI->       List(Y,N,N,N,N,N,N,X,N,N,N,N,A2_X,   A1_X,   IMM_X, DW_X,  aluFn.FN_X,     N,M_X,        N,N,N,N,N,N,N,CSR.I,N,N,N,N),
-    CEASE->     List(Y,N,N,N,N,N,N,X,N,N,N,N,A2_X,   A1_X,   IMM_X, DW_X,  aluFn.FN_X,     N,M_X,        N,N,N,N,N,N,N,CSR.I,N,N,N,N),
     CSRRW->     List(Y,N,N,N,N,N,N,Y,N,N,N,N,A2_ZERO,A1_RS1, IMM_X, DW_XPR,aluFn.FN_ADD,   N,M_X,        N,N,N,N,N,N,Y,CSR.W,N,N,N,N),
     CSRRS->     List(Y,N,N,N,N,N,N,Y,N,N,N,N,A2_ZERO,A1_RS1, IMM_X, DW_XPR,aluFn.FN_ADD,   N,M_X,        N,N,N,N,N,N,Y,CSR.S,N,N,N,N),
     CSRRC->     List(Y,N,N,N,N,N,N,Y,N,N,N,N,A2_ZERO,A1_RS1, IMM_X, DW_XPR,aluFn.FN_ADD,   N,M_X,        N,N,N,N,N,N,Y,CSR.C,N,N,N,N),
@@ -127,6 +126,13 @@ class IDecode(aluFn: ALUFN = ALUFN())(implicit val p: Parameters) extends Decode
     CSRRCI->    List(Y,N,N,N,N,N,N,N,N,N,N,N,A2_IMM, A1_ZERO,IMM_Z, DW_XPR,aluFn.FN_ADD,   N,M_X,        N,N,N,N,N,N,Y,CSR.C,N,N,N,N))
 }
 
+class CeaseDecode(aluFn: ALUFN = ALUFN())(implicit val p: Parameters) extends DecodeConstants
+{
+  val table: Array[(BitPat, List[BitPat])] = Array(
+    CEASE->     List(Y,N,N,N,N,N,N,X,N,N,N,N,A2_X,   A1_X,   IMM_X, DW_X,  aluFn.FN_X,     N,M_X,        N,N,N,N,N,N,N,CSR.I,N,N,N,N))
+}
+
+
 class FenceIDecode(flushDCache: Boolean, aluFn: ALUFN = ALUFN())(implicit val p: Parameters) extends DecodeConstants
 {
   private val (v, cmd) = if (flushDCache) (Y, BitPat(M_FLUSH_ALL)) else (N, M_X)

src/main/scala/rocket/RocketCore.scala

@@ -53,7 +53,8 @@ case class RocketCoreParams(
   mvendorid: Int = 0, // 0 means non-commercial implementation
   mimpid: Int = 0x20181004, // release date in BCD
   mulDiv: Option[MulDivParams] = Some(MulDivParams()),
-  fpu: Option[FPUParams] = Some(FPUParams())
+  fpu: Option[FPUParams] = Some(FPUParams()),
+  haveCease: Boolean = true // non-standard CEASE instruction
 ) extends CoreParams {
   val lgPauseCycles = 5
   val haveFSDirty = false
@@ -65,7 +66,7 @@ case class RocketCoreParams(
   val instBits: Int = if (useCompressed) 16 else 32
   val lrscCycles: Int = 80 // worst case is 14 mispredicted branches + slop
   val traceHasWdata: Boolean = false // ooo wb, so no wdata in trace
-  override val customIsaExt = Some("xrocket") // CEASE instruction
+  override val customIsaExt = Option.when(haveCease)("xrocket") // CEASE instruction
   override def minFLen: Int = fpu.map(_.minFLen).getOrElse(32)
   override def customCSRs(implicit p: Parameters) = new RocketCustomCSRs
 }
@@ -207,6 +208,7 @@ class Rocket(tile: RocketTile)(implicit p: Parameters) extends CoreModule()(p)
     (usingConditionalZero.option(new ConditionalZeroDecode(aluFn))) ++:
     Seq(new FenceIDecode(tile.dcache.flushOnFenceI, aluFn)) ++:
     coreParams.haveCFlush.option(new CFlushDecode(tile.dcache.canSupportCFlushLine, aluFn)) ++:
+    rocketParams.haveCease.option(new CeaseDecode(aluFn)) ++:
     Seq(new IDecode(aluFn))
   } flatMap(_.table)
 

src/main/scala/subsystem/Configs.scala

@@ -430,6 +430,14 @@ class WithCryptoSM extends Config((site, here, up) => {
   }
 })
 
+class WithRocketCease(enable: Boolean = true) extends Config((site, here, up) => {
+  case TilesLocated(InSubsystem) => up(TilesLocated(InSubsystem), site) map {
+    case tp: RocketTileAttachParams => tp.copy(tileParams = tp.tileParams.copy(
+      core = tp.tileParams.core.copy(haveCease = enable)
+    ))
+  }
+})
+
 class WithBootROMFile(bootROMFile: String) extends Config((site, here, up) => {
   case BootROMLocated(x) => up(BootROMLocated(x), site).map(_.copy(contentFileName = bootROMFile))
 })