Remove start address option from AddrMapEntries

It appears to never be used, and clutters things.  The new invariant is
that AddrMaps are relative and AddrHashMaps are absolute.

junctions/src/main/scala/addrmap.scala

@@ -59,7 +59,7 @@ class AddrMapProt extends Bundle {
   val r = Bool()
 }
 
-case class AddrMapEntry(name: String, start: Option[BigInt], region: MemRegion)
+case class AddrMapEntry(name: String, region: MemRegion)
 
 case class AddrHashMapEntry(port: Int, start: BigInt, size: BigInt, prot: Int, cacheable: Boolean)
 
@@ -84,16 +84,12 @@ class AddrHashMap(addrmap: AddrMap, start: BigInt = BigInt(0)) {
     var ind = 0
     var base = start
     var pairs = Seq[(String, AddrHashMapEntry)]()
-    am.foreach { case AddrMapEntry(name, startOpt, region) =>
-      region match {
-        case MemSize(size, prot, cacheable) => {
-          if (!startOpt.isEmpty) base = startOpt.get
+    am.foreach {
+      case AddrMapEntry(name, MemSize(size, prot, cacheable)) =>
         pairs = (name, AddrHashMapEntry(ind, base, size, prot, cacheable)) +: pairs
         base += size
         ind += 1
-        }
-        case MemSubmap(size, submap) => {
-          if (!startOpt.isEmpty) base = startOpt.get
+      case AddrMapEntry(name, MemSubmap(size, submap)) =>
         val subpairs = genPairs(submap, base).map {
           case (subname, AddrHashMapEntry(subind, subbase, subsize, prot, cacheable)) =>
             (name + ":" + subname,
@@ -103,8 +99,6 @@ class AddrHashMap(addrmap: AddrMap, start: BigInt = BigInt(0)) {
         ind += subpairs.size
         base += size
     }
-      }
-    }
     pairs
   }
 

junctions/src/main/scala/nasti.scala

@@ -505,21 +505,20 @@ class NastiRecursiveInterconnect(
   var lastEnd = base
   var slaveInd = 0
   val levelSize = addrmap.size
-  val realAddrMap = new ArraySeq[(BigInt, BigInt)](addrmap.size)
 
-  addrmap.zipWithIndex.foreach { case (AddrMapEntry(name, startOpt, region), i) =>
-    val start = startOpt.getOrElse(lastEnd)
+  val realAddrMap = addrmap map { case AddrMapEntry(name, region) =>
+    val start = lastEnd
     val size = region.size
 
-    require(bigIntPow2(size),
+    require(isPow2(size),
       s"Region $name size $size is not a power of 2")
     require(start % size == 0,
       f"Region $name start address 0x$start%x not divisible by 0x$size%x" )
     require(start >= lastEnd,
       f"Region $name start address 0x$start%x before previous region end")
 
-    realAddrMap(i) = (start, size)
     lastEnd = start + size
+    (start, size)
   }
 
   val routeSel = (addr: UInt) => {

junctions/src/main/scala/util.scala

@@ -3,10 +3,6 @@ package junctions
 import Chisel._
 import cde.Parameters
 
-object bigIntPow2 {
-  def apply(in: BigInt): Boolean = in > 0 && ((in & (in-1)) == 0)
-}
-
 class ParameterizedBundle(implicit p: Parameters) extends Bundle {
   override def cloneType = {
     try {