printing 2-letter strings is now only optimized into direct CHROUT if it's a const string literal

compiler/src/prog8/optimizer/StatementOptimizer.kt

@@ -48,6 +48,7 @@ internal class StatementOptimizer(private val program: Program,
         }
 
         // printing a literal string of just 2 or 1 characters is replaced by directly outputting those characters
+        // only do this optimization if the arg is a known-constant string literal instead of a user defined variable.
         if(functionCallStatement.target.nameInSource==listOf("txt", "print")) {
             val arg = functionCallStatement.args.single()
             val stringVar: IdentifierReference? = if(arg is AddressOf) {
@@ -55,10 +56,7 @@ internal class StatementOptimizer(private val program: Program,
             } else {
                 arg as? IdentifierReference
             }
-            if(stringVar!=null) {
-
-                // TODO: only do this optimization if the arg is a known-constant string literal instead of a user defined variable. We can't see the difference here yet.
-
+            if(stringVar!=null && stringVar.wasStringLiteral(program)) {
                 val string = stringVar.targetVarDecl(program)?.value as? StringLiteralValue
                 if(string!=null) {
                     val pos = functionCallStatement.position

compiler/src/prog8/optimizer/UnusedCodeRemover.kt

@@ -1,9 +1,6 @@
 package prog8.optimizer
 
-import prog8.ast.INameScope
-import prog8.ast.Module
-import prog8.ast.Node
-import prog8.ast.Program
+import prog8.ast.*
 import prog8.ast.base.VarDeclType
 import prog8.ast.expressions.BinaryExpression
 import prog8.ast.expressions.FunctionCall
@@ -65,7 +62,7 @@ internal class UnusedCodeRemover(private val program: Program,
     override fun after(block: Block, parent: Node): Iterable<IAstModification> {
         if("force_output" !in block.options()) {
             if (block.containsNoCodeNorVars()) {
-                if(block.name != program.internedStringsModuleName)
+                if(block.name != internedStringsModuleName)
                     errors.warn("removing unused block '${block.name}'", block.position)
                 return listOf(IAstModification.Remove(block, parent as INameScope))
             }

compilerAst/src/prog8/ast/AstToplevel.kt

@@ -8,6 +8,8 @@ import prog8.ast.walk.IAstVisitor
 import java.nio.file.Path
 import kotlin.math.abs
 
+const val internedStringsModuleName = "prog8_interned_strings"
+
 interface IStringEncoding {
     fun encodeString(str: String, altEncoding: Boolean): List<Short>
     fun decodeString(bytes: List<Short>, altEncoding: Boolean): String
@@ -257,7 +259,6 @@ class Program(val name: String,
 
     var actualLoadAddress: Int = 0
     private val internedStringsUnique = mutableMapOf<Pair<String, Boolean>, List<String>>()
-    val internedStringsModuleName = "prog8_interned_strings"
 
     init {
         // insert a container module for all interned strings later

compilerAst/src/prog8/ast/expressions/AstExpressions.kt

@@ -788,6 +788,15 @@ data class IdentifierReference(val nameInSource: List<String>, override val posi
             else -> InferredTypes.InferredType.unknown()
         }
     }
+
+    fun wasStringLiteral(program: Program): Boolean {
+        val decl = targetVarDecl(program)
+        if(decl == null || !decl.autogeneratedDontRemove)
+            return false
+
+        val scope=decl.definingModule()
+        return scope.name==internedStringsModuleName
+    }
 }
 
 class FunctionCall(override var target: IdentifierReference,

docs/source/todo.rst

@@ -4,8 +4,9 @@ TODO
 
 - possible idea: option to mark vardecls 'shared' to indicate they should not be optimized away because they're shared with assembly code?
   However: who even needs variables declared in prog8 code that are only used by assembly???
+
 - github issue about strings and their immutability:
-    StatementOptimizer line 60: only optimize when it's a known constant literal
+    Can we make deduplication the default again? (only string literals are considered...) remove cli option for it again?
     IMPROVE DOCUMENTATION ABOUT STRINGS AND DEDUP and (NON)IMMUTABILITY.
 
 - test all examples (including imgviewer, assembler and petaxian) before release of the new version

examples/test.p8

@@ -1,24 +1,26 @@
 %import textio ; txt.*
 %zeropage basicsafe
 main {
+
     sub start() {
 
-        str string1 = "stringvalue"
-        str string2 = "stringvalue"
-        str string3 = "stringvalue"
+        str string1 = "stringvalue\n"
+        str string2 = "stringvalue\n"
+        str string3 = "stringvalue\n"
+        str string4 = "a"
+        str string5 = "bb"
 
         txt.print("a")
         txt.print("a")
+        txt.print(string4)
         txt.print("bb")
         txt.print("bb")
+        txt.print(string5)
         txt.print("\n")
         txt.print("\n\n")
         txt.print(string1)
-        txt.nl()
         txt.print(string2)
-        txt.nl()
         txt.print(string3)
-        txt.nl()
         txt.print("hello\n")
         txt.print("hello\n")
         txt.print("hello\n")