18% speedup from interrupt optimization

src/main/kotlin/Main.kt

@@ -19,7 +19,7 @@ fun main(args: Array<String>) {
         cpu.runState = CPU.RunState.RUNNING
         cpu.pc = 0x80u
         val start = System.nanoTime()
-        val ninsn = cpu.run()
+        val ninsn = cpu.run(50000000)
         val end = System.nanoTime()
 
         System.err.println("Halted at 0${cpu.pc.toString(8)}")
@@ -29,4 +29,5 @@ fun main(args: Array<String>) {
         println("Exiting")
         console.stop()
     }
+    System.exit(0)
 }

src/main/kotlin/com/thequux/mcpdp/core/CPU.kt

@@ -828,6 +828,7 @@ class CPU(val mbus: MemBus) {
         try {
             if (runState == RunState.HALTED) return
 
+            if (mbus.unibus.interruptPending) {
                 for (i in 7 downTo (psw_priority + 1)) {
                     if (pirq bit 8 + i) {
                         logger.debug("PIRQ{} trap to 0xA0", i)
@@ -845,6 +846,12 @@ class CPU(val mbus: MemBus) {
                         break
                     }
                 }
+            } else {
+                val pirqLvl = pirq.toInt() shr 1 and 7;
+                if (pirqLvl > psw_priority) {
+                    trap(0xA0u)
+                }
+            }
             if (runState == RunState.WAIT_FOR_INTERRUPT) {
                 return
             }
@@ -867,6 +874,15 @@ class CPU(val mbus: MemBus) {
     fun run(): Long {
         var ninsn: Long = 0
         while (runState == RunState.RUNNING) {
+            ninsn += run(Long.MAX_VALUE)
+            step()
+        }
+        return ninsn
+    }
+
+    fun run(nstep: Long): Long {
+        var ninsn: Long = 0
+        while (runState == RunState.RUNNING && ninsn < nstep) {
             ninsn++
             step()
         }

src/main/kotlin/com/thequux/mcpdp/peripheral/Unibus.kt

@@ -77,6 +77,9 @@ class Unibus: PAddressSpace, Subregion(12, 6) {
     private val logger = LoggerFactory.getLogger(this.javaClass)
 
     private val queue: Array<MutableList<InterruptSource>> = Array(8) { Vector(4) }
+    private var interruptCount: Int = 0
+    val interruptPending: Boolean
+        get() = interruptCount > 0
 
     override fun map(address: UInt): PAddressSpace =
         super.map(address) ?: throw BusTimeoutError(address)
@@ -101,11 +104,17 @@ class Unibus: PAddressSpace, Subregion(12, 6) {
     /// to fetch the currently desired interrupt vector
     fun assertInterrupt(priority: Int, device: InterruptSource) {
         val list = queue[priority]
+        if (list.isEmpty()) {
+            interruptCount++
+        }
         if (!list.contains(device)) list.add(device)
     }
 
     fun deassertInterrupt(priority: Int, device: InterruptSource) {
-        queue[priority].remove(device)
+        val lvlQueue = queue[priority]
+        if (lvlQueue.remove(device) && lvlQueue.isEmpty()) {
+            interruptCount--
+        }
     }
 
     // Checks for an interrupt. The handler receives (priority, device)