tweak return's use of intermediate variable

Author: irmen

codeOptimizers/src/prog8/optimizer/StatementOptimizer.kt

@@ -459,10 +459,14 @@ class StatementOptimizer(private val program: Program,
             return null
         }
 
-        if(returnStmt.value is BinaryExpression) {
-            val mod = returnViaIntermediaryVar(returnStmt.value!!)
-            if(mod!=null)
-                return mod
+        // TODO decision when to use intermediary variable to calculate returnvalue seems a bit arbitrary...
+        val returnvalue = returnStmt.value
+        if (returnvalue!=null) {
+            if (returnvalue is BinaryExpression || (returnvalue is TypecastExpression && !returnvalue.expression.isSimple)) {
+                val mod = returnViaIntermediaryVar(returnvalue)
+                if(mod!=null)
+                    return mod
+            }
         }
 
         return noModifications

docs/source/todo.rst

@@ -3,10 +3,7 @@ TODO
 
 For next release
 ^^^^^^^^^^^^^^^^
-- why does this use stack eval on return:
-    sub sprite_y_for_row(ubyte row) -> word {
-        return (8-row as byte)
-    }
+...
 
 
 Need help with

examples/test.p8

@@ -4,22 +4,20 @@
 
 main {
     sub start() {
-        ubyte ccc
-        ubyte @shared qq = string.find("irmendejong", ccc)!=0
-        word ww
-        ww = calculate(6)
+        word  ww = calculate(6)
         txt.print_w(ww)
         txt.nl()
-        ww = calculate(8)
-        txt.print_w(ww)
-        txt.nl()
-        ww = calculate(10)
-        txt.print_w(ww)
+        ubyte bb = calculate2(6)
+        txt.print_ub(bb)
         txt.nl()
-        qq = string.find("irmendejong", ccc)!=0
     }
 
+    sub calculate2(ubyte row) -> ubyte {
+        return 8+row
+    }
+
+
     sub calculate(ubyte row) -> word {
-        return 8-(row as byte)
+        return 8+row
     }
 }