Implement constant folding for value primitives

compiler/src/l3/CPSOptimizer.scala

@@ -105,12 +105,21 @@ abstract class CPSOptimizer[T <: CPSTreeModule { type Name = Symbol }]
     case LetP(name, prim, args, body) => {
       val replacedArgs = replaceArgs(args, s)
       val newState = s.withExp(name, prim, replacedArgs)
-      val shrunkBody = shrink(body, newState)
+      lazy val shrunkBody = shrink(body, newState)
 
       if (s.dead(name) && !impure(prim)) {
         shrunkBody
       } else {
-        LetP(name, prim, replacedArgs, shrunkBody)
+        val allLitOpt = replacedArgs.map(_.asLiteral)
+        val isAllLit = allLitOpt.forall(_.isDefined)
+        lazy val asLit = allLitOpt.map(_.get)
+        if (isAllLit && vEvaluator.isDefinedAt((prim, asLit))) {
+          val newNewState = newState.withASubst(name, vEvaluator((prim, asLit)))
+          val newBody = shrink(body, newNewState)
+          newBody
+        } else {
+          LetP(name, prim, replacedArgs, shrunkBody)
+        }
       }
     }
 

compiler/src/l3/Main.scala

@@ -11,6 +11,7 @@ import CPSTreeChecker._   // Implicits required for CPS tree checking
 
 object Main {
   def main(args: Array[String]): Unit = {
+    val stats = new Statistics()
     val backEnd: Tree => TerminalPhaseResult = (
       CL3ToCPSTranslator
         andThen treePrinter("---------- After CPS translation")
@@ -25,7 +26,7 @@ object Main {
         andThen CPSOptimizerLow
         andThen treePrinter("---------- After Optimization (Low)")
         andThen treeChecker
-        andThen CPSInterpreterLow
+        andThen (new CPSInterpreterLow(stats.log _))
     )
 
 
@@ -37,6 +38,7 @@ object Main {
       .flatMap(backEnd) match {
       case Right((retCode, maybeMsg)) =>
         maybeMsg foreach println
+        println(stats)
         sys.exit(retCode)
       case Left(errMsg) =>
         println(s"Error: $errMsg")