Add FPUParams.fLen option, decoupled from xLen

src/main/scala/rocket/CSR.scala

@@ -333,8 +333,8 @@ class CSRFile(perfEventSets: EventSets = new EventSets(Seq()))(implicit p: Param
   val isaMaskString =
     (if (usingMulDiv) "M" else "") +
     (if (usingAtomics) "A" else "") +
-    (if (usingFPU) "F" else "") +
-    (if (usingFPU && xLen > 32) "D" else "") +
+    (if (fLen >= 32) "F" else "") +
+    (if (fLen >= 64) "D" else "") +
     (if (usingCompressed) "C" else "") +
     (if (usingRoCC) "X" else "")
   val isaString = "I" + isaMaskString +

src/main/scala/rocket/RocketCore.scala

@@ -108,8 +108,8 @@ class Rocket(implicit p: Parameters) extends CoreModule()(p)
   val decode_table = {
     (if (usingMulDiv) new MDecode +: (xLen > 32).option(new M64Decode).toSeq else Nil) ++:
     (if (usingAtomics) new ADecode +: (xLen > 32).option(new A64Decode).toSeq else Nil) ++:
-    (if (usingFPU) new FDecode +: (xLen > 32).option(new F64Decode).toSeq else Nil) ++:
-    (if (usingFPU && xLen > 32) Seq(new DDecode, new D64Decode) else Nil) ++:
+    (if (fLen >= 32) new FDecode +: (xLen > 32).option(new F64Decode).toSeq else Nil) ++:
+    (if (fLen >= 64) new DDecode +: (xLen > 32).option(new D64Decode).toSeq else Nil) ++:
     (usingRoCC.option(new RoCCDecode)) ++:
     ((xLen > 32).option(new I64Decode)) ++:
     (usingVM.option(new SDecode)) ++:

src/main/scala/tile/Core.scala

@@ -44,7 +44,7 @@ trait CoreParams {
 trait HasCoreParameters extends HasTileParameters {
   val coreParams: CoreParams = tileParams.core
 
-  val fLen = xLen // TODO relax this
+  val fLen = coreParams.fpu.map(_.fLen).getOrElse(0)
 
   val usingMulDiv = coreParams.mulDiv.nonEmpty
   val usingFPU = coreParams.fpu.nonEmpty

src/main/scala/tile/FPU.scala

@@ -14,6 +14,7 @@ import freechips.rocketchip.util.property._
 import chisel3.internal.sourceinfo.SourceInfo
 
 case class FPUParams(
+  fLen: Int = 64,
   divSqrt: Boolean = true,
   sfmaLatency: Int = 3,
   dfmaLatency: Int = 4