refactor: replace strings ListBuffer with labelGenerator

src/main/wacc/backend/asmGenerator.scala

@@ -1,6 +1,6 @@
 package wacc
 
-import scala.collection.mutable.ListBuffer
+import scala.collection.mutable
 import cats.data.Chain
 import cats.syntax.foldable._
 import wacc.RuntimeError._
@@ -31,8 +31,9 @@ object asmGenerator {
     def concatAll(chains: Chain[T]*): Chain[T] =
       chains.foldLeft(chain)(_ ++ _)
 
-  class LabelGenerator {
-    var labelVal = -1
+  private class LabelGenerator {
+    private val strings = mutable.HashMap[String, String]()
+    private var labelVal = -1
     def getLabel(): String = {
       labelVal += 1
       s".L$labelVal"
@@ -41,11 +42,21 @@ object asmGenerator {
       case Ident(v, _)   => s"wacc_$v"
       case Builtin(name) => s"_$name"
     }
+    def getLabel(str: String): String =
+      strings.getOrElseUpdate(str, s".L.str${strings.size}")
+
+    def generateConstants: Chain[AsmLine] =
+      strings.foldLeft(Chain.empty) { case (acc, (str, label)) =>
+        acc ++ Chain(
+          Directive.Int(str.size),
+          LabelDef(label),
+          Directive.Asciz(str.escaped)
+        )
+      }
   }
 
   def generateAsm(microProg: Program): Chain[AsmLine] = {
     given stack: Stack = Stack()
-    given strings: ListBuffer[String] = ListBuffer[String]()
     given labelGenerator: LabelGenerator = LabelGenerator()
     val Program(funcs, main) = microProg
 
@@ -58,20 +69,13 @@ object asmGenerator {
       funcs.foldMap(generateUserFunc(_))
     )
 
-    val strDirs = strings.toList.zipWithIndex.foldMap { case (str, i) =>
-      Chain(
-        Directive.Int(str.size),
-        LabelDef(s".L.str$i"),
-        Directive.Asciz(str.escaped)
-      )
-    } ++ RuntimeError.all.foldMap(_.stringDef)
-
     Chain(
       Directive.IntelSyntax,
       Directive.Global("main"),
       Directive.RoData
     ).concatAll(
-      strDirs,
+      labelGenerator.generateConstants,
+      RuntimeError.all.foldMap(_.stringDef),
       Chain.one(Directive.Text),
       progAsm
     )
@@ -88,7 +92,6 @@ object asmGenerator {
   }
 
   private def generateUserFunc(func: FuncDecl)(using
-      strings: ListBuffer[String],
       labelGenerator: LabelGenerator
   ): Chain[AsmLine] = {
     given stack: Stack = Stack()
@@ -175,7 +178,6 @@ object asmGenerator {
 
   private def generateStmt(stmt: Stmt)(using
       stack: Stack,
-      strings: ListBuffer[String],
       labelGenerator: LabelGenerator
   ): Chain[AsmLine] = {
     var chain = Chain.empty[AsmLine]
@@ -259,7 +261,6 @@ object asmGenerator {
 
   private def evalExprOntoStack(expr: Expr)(using
       stack: Stack,
-      strings: ListBuffer[String],
       labelGenerator: LabelGenerator
   ): Chain[AsmLine] = {
     var chain = Chain.empty[AsmLine]
@@ -272,8 +273,8 @@ object asmGenerator {
       case array @ ArrayLiter(elems) =>
         expr.ty match {
           case KnownType.String =>
-            strings += elems.collect { case CharLiter(v) => v }.mkString
-            chain += Load(RAX, IndexAddress(RIP, LabelArg(s".L.str${strings.size - 1}")))
+            val str = elems.collect { case CharLiter(v) => v }.mkString
+            chain += Load(RAX, IndexAddress(RIP, LabelArg(labelGenerator.getLabel(str))))
             chain += stack.push(Q64, RAX)
           case ty =>
             chain ++= generateCall(
@@ -398,7 +399,6 @@ object asmGenerator {
 
   private def generateCall(call: microWacc.Call, isTail: Boolean)(using
       stack: Stack,
-      strings: ListBuffer[String],
       labelGenerator: LabelGenerator
   ): Chain[AsmLine] = {
     var chain = Chain.empty[AsmLine]