re-use global returnvalue temp var instead of duplicating it in every subroutine that needs it

codeOptimizers/src/prog8/optimizer/StatementOptimizer.kt

@@ -15,8 +15,6 @@ import prog8.compilerinterface.IErrorReporter
 import prog8.compilerinterface.size
 import kotlin.math.floor
 
-internal const val retvarName = "prog8_retval"
-
 
 class StatementOptimizer(private val program: Program,
                                   private val errors: IErrorReporter,
@@ -24,23 +22,6 @@ class StatementOptimizer(private val program: Program,
                                   private val compTarget: ICompilationTarget
 ) : AstWalker() {
 
-    private val subsThatNeedReturnVariable = mutableSetOf<Triple<IStatementContainer, DataType, Position>>()
-
-
-    override fun after(subroutine: Subroutine, parent: Node): Iterable<IAstModification> {
-        for(returnvar in subsThatNeedReturnVariable) {
-            val decl = VarDecl(VarDeclType.VAR, returnvar.second, ZeropageWish.DONTCARE, null, retvarName, null,
-                isArray = false,
-                autogeneratedDontRemove = true,
-                sharedWithAsm = false,
-                position = returnvar.third
-            )
-            returnvar.first.statements.add(0, decl)
-        }
-        subsThatNeedReturnVariable.clear()
-        return noModifications
-    }
-
     override fun before(functionCall: FunctionCall, parent: Node): Iterable<IAstModification> {
         // if the first instruction in the called subroutine is a return statement with a simple value,
         // remove the jump altogeter and inline the returnvalue directly.
@@ -439,12 +420,17 @@ class StatementOptimizer(private val program: Program,
             val returnDt = subr.returntypes.single()
             if (returnDt in IntegerDatatypes) {
                 // first assign to intermediary variable, then return that
-                subsThatNeedReturnVariable.add(Triple(subr, returnDt, returnStmt.position))
-                val returnValueIntermediary1 = IdentifierReference(listOf(retvarName), returnStmt.position)
-                val returnValueIntermediary2 = IdentifierReference(listOf(retvarName), returnStmt.position)
-                val tgt = AssignTarget(returnValueIntermediary1, null, null, returnStmt.position)
+                val returnVarName = "retval_interm_" + when(returnDt) {
+                    DataType.UBYTE -> "ub"
+                    DataType.BYTE -> "b"
+                    DataType.UWORD -> "uw"
+                    DataType.WORD -> "w"
+                    else -> "<undefined>"
+                }
+                val returnValueIntermediary = IdentifierReference(listOf("prog8_lib", returnVarName), returnStmt.position)
+                val tgt = AssignTarget(returnValueIntermediary, null, null, returnStmt.position)
                 val assign = Assignment(tgt, value, returnStmt.position)
-                val returnReplacement = Return(returnValueIntermediary2, returnStmt.position)
+                val returnReplacement = Return(returnValueIntermediary.copy(), returnStmt.position)
                 return listOf(
                     IAstModification.InsertBefore(returnStmt, assign, parent as IStatementContainer),
                     IAstModification.ReplaceNode(returnStmt, returnReplacement, parent)

compiler/res/prog8lib/prog8_lib.p8

@@ -6,12 +6,13 @@ prog8_lib {
 	%asminclude "library:prog8_lib.asm"
 	%asminclude "library:prog8_funcs.asm"
 
-        ; TODO these retval variables are no longer used???
-	uword @zp retval_interm_uw      ; to store intermediary expression results for return values (hopefully allocated on ZP to reduce code size)
-	word @zp retval_interm_w        ; to store intermediary expression results for return values (hopefully allocated on ZP to reduce code size)
-	ubyte @zp retval_interm_ub      ; to store intermediary expression results for return values (hopefully allocated on ZP to reduce code size)
-	byte @zp retval_interm_b        ; to store intermediary expression results for return values (hopefully allocated on ZP to reduce code size)
-	; NOTE: these variables are checked in the StatementReorderer (in fun after(decl: VarDecl)), for these exact names!
+	; to store intermediary expression results for return values (hopefully allocated on ZP to reduce code size):
+	; NOTE: these variables are used in the StatementReorderer and StatementOptimizer
+	uword @zp retval_interm_uw
+	word @zp retval_interm_w
+	ubyte @zp retval_interm_ub
+	byte @zp retval_interm_b
+
 
 	asmsub pattern_match(str string @AY, str pattern @R0) clobbers(Y) -> ubyte @A {
 		%asm {{

compiler/res/version.txt

@@ -1 +1 @@
-7.2
+7.3-dev

compiler/src/prog8/compiler/astprocessing/StatementReorderer.kt

@@ -53,7 +53,6 @@ internal class StatementReorderer(val program: Program, val errors: IErrorReport
                         decl.value = null
                         if(decl.name.startsWith("retval_interm_") && decl.definingScope.name=="prog8_lib") {
                             // no need to zero out the special internal returnvalue intermediates.
-                            // TODO these variables are no longer used???
                             return noModifications
                         }
                         val nextStmt  = decl.nextSibling()