Single threaded mode

src/main/scala/millfork/CompilationOptions.scala

@@ -126,6 +126,8 @@ object CompilationFlag extends Enumeration {
   VariableOverlap, CompactReturnDispatchParams,
   // runtime check options
   CheckIndexOutOfBounds,
+  // special options
+  SingleThreaded,
   // warning options
   ExtraComparisonWarnings,
   RorWarning,

src/main/scala/millfork/Main.scala

@@ -301,6 +301,10 @@ object Main {
 
     fluff("", "Other options:", "")
 
+    flag("--single-threaded").action(c =>
+      c.changeFlag(CompilationFlag.SingleThreaded, true)
+    ).description("Run the compiler in a single thread.")
+
     flag("--help").action(c => {
       printHelp(20).foreach(println(_))
       assumeStatus(CliStatus.Quit)

src/main/scala/millfork/assembly/opt/SuperOptimizer.scala

@@ -52,7 +52,8 @@ object SuperOptimizer extends AssemblyOptimization {
     while(queue.nonEmpty) {
       val (optsSoFar, codeSoFar) = queue.dequeue()
       var isLeaf = true
-      allOptimizers.par.foreach { o =>
+      (if (options.flag(CompilationFlag.SingleThreaded)) allOptimizers
+      else allOptimizers.par).foreach { o =>
         val optimized = o.optimize(m, codeSoFar, options)
         val view = viewCode(optimized)
         seenSoFar.synchronized{

src/main/scala/millfork/assembly/opt/VariableToRegisterOptimization.scala

@@ -194,7 +194,7 @@ object VariableToRegisterOptimization extends AssemblyOptimization {
     val aCandidateSets = NonOverlappingIntervals.apply[(String, Range, Int)](aCandidates, _._2.start, _._2.end)
 
     val variants = for {
-      vx <- xCandidateSets.par
+      vx <- if (options.flag(CompilationFlag.SingleThreaded)) xCandidateSets else xCandidateSets.par
       nx = vx.map(_._1)
 
       vy <- yCandidateSets

src/main/scala/millfork/parser/SourceLoadingQueue.scala

@@ -30,8 +30,12 @@ class SourceLoadingQueue(val initialFilenames: List[String], val includePath: Li
       moduleQueue.enqueue(() => parseModule("zp_reg", includePath, Left(None), options))
     }
     while (moduleQueue.nonEmpty) {
+      if (options.flag(CompilationFlag.SingleThreaded)) {
+        moduleQueue.dequeueAll(_ => true).foreach(_())
+      } else {
         moduleQueue.dequeueAll(_ => true).par.foreach(_())
       }
+    }
     ErrorReporting.assertNoErrors("Parse failed")
     parsedModules.values.reduce(_ + _)
   }