diff --git a/compiler/src/prog8/compiler/Compiler.kt b/compiler/src/prog8/compiler/Compiler.kt
index 426460364..bf60062aa 100644
--- a/compiler/src/prog8/compiler/Compiler.kt
+++ b/compiler/src/prog8/compiler/Compiler.kt
@@ -1552,17 +1552,19 @@ internal class Compiler(private val program: Program) {
     private fun translate(loop: ForLoop) {
         if(loop.body.containsNoCodeNorVars()) return
         prog.line(loop.position)
-        val loopVarName: String
-        val loopVarDt: DataType
+        val loopVarName: String?
+        val loopRegister: Register?
+        val loopvalueDt: DataType
 
         if(loop.loopRegister!=null) {
-            val reg = loop.loopRegister
-            loopVarName = reg.name
-            loopVarDt = DataType.UBYTE
+            loopVarName = null
+            loopRegister = loop.loopRegister
+            loopvalueDt = DataType.UBYTE
         } else {
             val loopvar = loop.loopVar!!.targetVarDecl(program.namespace)!!
             loopVarName = loopvar.scopedname
-            loopVarDt = loopvar.datatype
+            loopvalueDt = loopvar.datatype
+            loopRegister = null
         }
 
         if(loop.iterable is RangeExpr) {
@@ -1575,7 +1577,7 @@ internal class Compiler(private val program: Program) {
                     throw CompilerException("loop over just 1 value should have been optimized away")
                 if((range.last-range.first) % range.step != 0)
                     throw CompilerException("range first and last must be exactly inclusive")
-                when (loopVarDt) {
+                when (loopvalueDt) {
                     DataType.UBYTE -> {
                         if (range.first < 0 || range.first > 255 || range.last < 0 || range.last > 255)
                             throw CompilerException("range out of bounds for ubyte")
@@ -1594,7 +1596,7 @@ internal class Compiler(private val program: Program) {
                     }
                     else -> throw CompilerException("range must be byte or word")
                 }
-                translateForOverConstantRange(loopVarName, loopVarDt, range, loop.body)
+                translateForOverConstantRange(loopVarName, loopRegister, loopvalueDt, range, loop.body)
             } else {
                 // loop over a range where one or more of the start, last or step values is not a constant
                 if(loop.loopRegister!=null) {
@@ -1613,7 +1615,7 @@ internal class Compiler(private val program: Program) {
                     val iterableValue = vardecl.value as LiteralValue
                     if(iterableValue.type !in IterableDatatypes)
                         throw CompilerException("loop over something that isn't iterable ${loop.iterable}")
-                    translateForOverIterableVar(loop, loopVarDt, iterableValue)
+                    translateForOverIterableVar(loop, loopvalueDt, iterableValue)
                 }
                 loop.iterable is LiteralValue -> throw CompilerException("literal value in loop must have been moved to heap already $loop")
                 else -> throw CompilerException("loopvar is something strange ${loop.iterable}")
@@ -1706,7 +1708,7 @@ internal class Compiler(private val program: Program) {
         continueStmtLabelStack.pop()
     }
 
-    private fun translateForOverConstantRange(varname: String, varDt: DataType, range: IntProgression, body: AnonymousScope) {
+    private fun translateForOverConstantRange(varname: String?, loopregister: Register?, varDt: DataType, range: IntProgression, body: AnonymousScope) {
         /**
          * for LV in start..last { body }
          * (and we already know that the range is not empty, and first and last are exactly inclusive.)
@@ -1734,7 +1736,9 @@ internal class Compiler(private val program: Program) {
         breakStmtLabelStack.push(breakLabel)
 
         prog.instr(opcodePush(varDt), RuntimeValue(varDt, range.first))
-        prog.instr(opcodePopvar(varDt), callLabel = varname)
+        val variableLabel = varname ?: loopregister?.name
+
+        prog.instr(opcodePopvar(varDt), callLabel = variableLabel)
         prog.label(loopLabel)
         translate(body)
         prog.label(continueLabel)
@@ -1742,25 +1746,25 @@ internal class Compiler(private val program: Program) {
         when {
             range.step in 1..numberOfIncDecsForOptimize -> {
                 repeat(range.step) {
-                    prog.instr(opcodeIncvar(varDt), callLabel = varname)
+                    prog.instr(opcodeIncvar(varDt), callLabel = variableLabel)
                 }
             }
             range.step in -1 downTo -numberOfIncDecsForOptimize -> {
                 repeat(abs(range.step)) {
-                    prog.instr(opcodeDecvar(varDt), callLabel = varname)
+                    prog.instr(opcodeDecvar(varDt), callLabel = variableLabel)
                 }
             }
             range.step>numberOfIncDecsForOptimize -> {
-                prog.instr(opcodePushvar(varDt), callLabel = varname)
+                prog.instr(opcodePushvar(varDt), callLabel = variableLabel)
                 prog.instr(opcodePush(varDt), RuntimeValue(varDt, range.step))
                 prog.instr(opcodeAdd(varDt))
-                prog.instr(opcodePopvar(varDt), callLabel = varname)
+                prog.instr(opcodePopvar(varDt), callLabel = variableLabel)
             }
             range.step<numberOfIncDecsForOptimize -> {
-                prog.instr(opcodePushvar(varDt), callLabel = varname)
+                prog.instr(opcodePushvar(varDt), callLabel = variableLabel)
                 prog.instr(opcodePush(varDt), RuntimeValue(varDt, abs(range.step)))
                 prog.instr(opcodeSub(varDt))
-                prog.instr(opcodePopvar(varDt), callLabel = varname)
+                prog.instr(opcodePopvar(varDt), callLabel = variableLabel)
             }
         }
 
@@ -1768,7 +1772,7 @@ internal class Compiler(private val program: Program) {
             // optimize for the for loop that counts to 0
             prog.instr(if(range.first>0) Opcode.BPOS else Opcode.BNEG, callLabel = loopLabel)
         } else {
-            prog.instr(opcodePushvar(varDt), callLabel = varname)
+            prog.instr(opcodePushvar(varDt), callLabel = variableLabel)
             val checkValue =
                     when (varDt) {
                         DataType.UBYTE -> (range.last + range.step) and 255
diff --git a/compiler/src/prog8/compiler/Main.kt b/compiler/src/prog8/compiler/Main.kt
index 1e9917632..cf92d4cda 100644
--- a/compiler/src/prog8/compiler/Main.kt
+++ b/compiler/src/prog8/compiler/Main.kt
@@ -88,7 +88,7 @@ fun compileProgram(filepath: Path,
             programAst.checkValid(compilerOptions)          // check if final tree is valid
             programAst.checkRecursion()         // check if there are recursive subroutine calls
 
-            // printAst(programAst)
+            printAst(programAst)
             // namespace.debugPrint()
 
             if(generateVmCode) {
diff --git a/compiler/src/prog8/vm/astvm/AstVm.kt b/compiler/src/prog8/vm/astvm/AstVm.kt
index 72f4db1f4..dc3c6083c 100644
--- a/compiler/src/prog8/vm/astvm/AstVm.kt
+++ b/compiler/src/prog8/vm/astvm/AstVm.kt
@@ -10,9 +10,11 @@ import prog8.vm.RuntimeValue
 import prog8.vm.RuntimeValueRange
 import prog8.compiler.target.c64.Petscii
 import java.awt.EventQueue
+import java.util.*
 import kotlin.NoSuchElementException
 import kotlin.concurrent.fixedRateTimer
-import kotlin.math.min
+import kotlin.math.*
+import kotlin.random.Random
 
 
 class VmExecutionException(msg: String?) : Exception(msg)
@@ -128,6 +130,13 @@ class AstVm(val program: Program) {
     val bootTime = System.currentTimeMillis()
     var rtcOffset = bootTime
 
+    private val rnd = Random(0)
+    private val statusFlagsSave = Stack<StatusFlags>()
+    private val registerXsave = Stack<RuntimeValue>()
+    private val registerYsave = Stack<RuntimeValue>()
+    private val registerAsave = Stack<RuntimeValue>()
+
+
     init {
         // observe the jiffyclock
         mem.observe(0xa0, 0xa1, 0xa2)
@@ -236,8 +245,7 @@ class AstVm(val program: Program) {
     }
 
     private val runtimeVariables = RuntimeVariables()
-    private val functions = BuiltinFunctions()
-    private val evalCtx = EvalContext(program, mem, statusflags, runtimeVariables, functions, ::executeSubroutine)
+    private val evalCtx = EvalContext(program, mem, statusflags, runtimeVariables, ::performBuiltinFunction, ::executeSubroutine)
 
     class LoopControlBreak : Exception()
     class LoopControlContinue : Exception()
@@ -324,7 +332,7 @@ class AstVm(val program: Program) {
                             executeSwap(stmt)
                         } else {
                             val args = evaluate(stmt.arglist)
-                            functions.performBuiltinFunction(target.name, args, statusflags)
+                            performBuiltinFunction(target.name, args, statusflags)
                         }
                     }
                     else -> {
@@ -363,6 +371,16 @@ class AstVm(val program: Program) {
                     stmt.target.arrayindexed != null -> {
                         TODO("postincrdecr array $stmt")
                     }
+                    stmt.target.register != null -> {
+                        var value = runtimeVariables.get(program.namespace, stmt.target.register!!.name)
+                        value = when {
+                            stmt.operator == "++" -> value.add(RuntimeValue(value.type, 1))
+                            stmt.operator == "--" -> value.sub(RuntimeValue(value.type, 1))
+                            else -> throw VmExecutionException("strange postincdec operator $stmt")
+                        }
+                        runtimeVariables.set(program.namespace, stmt.target.register!!.name, value)
+                    }
+                    else -> throw VmExecutionException("empty postincrdecr? $stmt")
                 }
             }
             is Jump -> throw LoopControlJump(stmt.identifier, stmt.address, stmt.generatedLabel)
@@ -629,5 +647,199 @@ class AstVm(val program: Program) {
             else -> TODO("syscall  ${sub.scopedname} $sub")
         }
     }
+
+    private fun performBuiltinFunction(name: String, args: List<RuntimeValue>, statusflags: StatusFlags): RuntimeValue? {
+        return when (name) {
+            "rnd" -> RuntimeValue(DataType.UBYTE, rnd.nextInt() and 255)
+            "rndw" -> RuntimeValue(DataType.UWORD, rnd.nextInt() and 65535)
+            "rndf" -> RuntimeValue(DataType.FLOAT, rnd.nextDouble())
+            "lsb" -> RuntimeValue(DataType.UBYTE, args[0].integerValue() and 255)
+            "msb" -> RuntimeValue(DataType.UBYTE, (args[0].integerValue() ushr 8) and 255)
+            "sin" -> RuntimeValue(DataType.FLOAT, sin(args[0].numericValue().toDouble()))
+            "sin8" -> {
+                val rad = args[0].numericValue().toDouble() / 256.0 * 2.0 * PI
+                RuntimeValue(DataType.BYTE, (127.0 * sin(rad)).toShort())
+            }
+            "sin8u" -> {
+                val rad = args[0].numericValue().toDouble() / 256.0 * 2.0 * PI
+                RuntimeValue(DataType.UBYTE, (128.0 + 127.5 * sin(rad)).toShort())
+            }
+            "sin16" -> {
+                val rad = args[0].numericValue().toDouble() / 256.0 * 2.0 * PI
+                RuntimeValue(DataType.BYTE, (32767.0 * sin(rad)).toShort())
+            }
+            "sin16u" -> {
+                val rad = args[0].numericValue().toDouble() / 256.0 * 2.0 * PI
+                RuntimeValue(DataType.UBYTE, (32768.0 + 32767.5 * sin(rad)).toShort())
+            }
+            "cos" -> RuntimeValue(DataType.FLOAT, cos(args[0].numericValue().toDouble()))
+            "cos8" -> {
+                val rad = args[0].numericValue().toDouble() / 256.0 * 2.0 * PI
+                RuntimeValue(DataType.BYTE, (127.0 * cos(rad)).toShort())
+            }
+            "cos8u" -> {
+                val rad = args[0].numericValue().toDouble() / 256.0 * 2.0 * PI
+                RuntimeValue(DataType.UBYTE, (128.0 + 127.5 * cos(rad)).toShort())
+            }
+            "cos16" -> {
+                val rad = args[0].numericValue().toDouble() / 256.0 * 2.0 * PI
+                RuntimeValue(DataType.BYTE, (32767.0 * cos(rad)).toShort())
+            }
+            "cos16u" -> {
+                val rad = args[0].numericValue().toDouble() / 256.0 * 2.0 * PI
+                RuntimeValue(DataType.UBYTE, (32768.0 + 32767.5 * cos(rad)).toShort())
+            }
+            "tan" -> RuntimeValue(DataType.FLOAT, tan(args[0].numericValue().toDouble()))
+            "atan" -> RuntimeValue(DataType.FLOAT, atan(args[0].numericValue().toDouble()))
+            "ln" -> RuntimeValue(DataType.FLOAT, ln(args[0].numericValue().toDouble()))
+            "log2" -> RuntimeValue(DataType.FLOAT, log2(args[0].numericValue().toDouble()))
+            "sqrt" -> RuntimeValue(DataType.FLOAT, sqrt(args[0].numericValue().toDouble()))
+            "sqrt16" -> RuntimeValue(DataType.UBYTE, sqrt(args[0].wordval!!.toDouble()).toInt())
+            "rad" -> RuntimeValue(DataType.FLOAT, Math.toRadians(args[0].numericValue().toDouble()))
+            "deg" -> RuntimeValue(DataType.FLOAT, Math.toDegrees(args[0].numericValue().toDouble()))
+            "round" -> RuntimeValue(DataType.FLOAT, round(args[0].numericValue().toDouble()))
+            "floor" -> RuntimeValue(DataType.FLOAT, floor(args[0].numericValue().toDouble()))
+            "ceil" -> RuntimeValue(DataType.FLOAT, ceil(args[0].numericValue().toDouble()))
+            "rol" -> {
+                val (result, newCarry) = args[0].rol(statusflags.carry)
+                statusflags.carry = newCarry
+                return result
+            }
+            "rol2" -> args[0].rol2()
+            "ror" -> {
+                val (result, newCarry) = args[0].ror(statusflags.carry)
+                statusflags.carry = newCarry
+                return result
+            }
+            "ror2" -> args[0].ror2()
+            "lsl" -> args[0].shl()
+            "lsr" -> args[0].shr()
+            "abs" -> {
+                when (args[0].type) {
+                    DataType.UBYTE -> args[0]
+                    DataType.BYTE -> RuntimeValue(DataType.UBYTE, abs(args[0].numericValue().toDouble()))
+                    DataType.UWORD -> args[0]
+                    DataType.WORD -> RuntimeValue(DataType.UWORD, abs(args[0].numericValue().toDouble()))
+                    DataType.FLOAT -> RuntimeValue(DataType.FLOAT, abs(args[0].numericValue().toDouble()))
+                    else -> TODO("strange abs type")
+                }
+            }
+            "max" -> {
+                val numbers = args.map { it.numericValue().toDouble() }
+                RuntimeValue(args[0].type, numbers.max())
+            }
+            "min" -> {
+                val numbers = args.map { it.numericValue().toDouble() }
+                RuntimeValue(args[0].type, numbers.min())
+            }
+            "avg" -> {
+                val numbers = args.map { it.numericValue().toDouble() }
+                RuntimeValue(DataType.FLOAT, numbers.average())
+            }
+            "sum" -> {
+                val sum = args.map { it.numericValue().toDouble() }.sum()
+                when (args[0].type) {
+                    DataType.UBYTE -> RuntimeValue(DataType.UWORD, sum)
+                    DataType.BYTE -> RuntimeValue(DataType.WORD, sum)
+                    DataType.UWORD -> RuntimeValue(DataType.UWORD, sum)
+                    DataType.WORD -> RuntimeValue(DataType.WORD, sum)
+                    DataType.FLOAT -> RuntimeValue(DataType.FLOAT, sum)
+                    else -> TODO("weird sum type")
+                }
+            }
+            "any" -> {
+                val numbers = args.map { it.numericValue().toDouble() }
+                RuntimeValue(DataType.UBYTE, if (numbers.any { it != 0.0 }) 1 else 0)
+            }
+            "all" -> {
+                val numbers = args.map { it.numericValue().toDouble() }
+                RuntimeValue(DataType.UBYTE, if (numbers.all { it != 0.0 }) 1 else 0)
+            }
+            "swap" ->
+                throw VmExecutionException("swap() cannot be implemented as a function")
+            "strlen" -> {
+                val zeroIndex = args[0].str!!.indexOf(0.toChar())
+                if (zeroIndex >= 0)
+                    RuntimeValue(DataType.UBYTE, zeroIndex)
+                else
+                    RuntimeValue(DataType.UBYTE, args[0].str!!.length)
+            }
+            "memset" -> {
+                val target = args[0].array!!
+                val amount = args[1].integerValue()
+                val value = args[2].integerValue()
+                for (i in 0 until amount) {
+                    target[i] = value
+                }
+                null
+            }
+            "memsetw" -> {
+                val target = args[0].array!!
+                val amount = args[1].integerValue()
+                val value = args[2].integerValue()
+                for (i in 0 until amount step 2) {
+                    target[i * 2] = value and 255
+                    target[i * 2 + 1] = value ushr 8
+                }
+                null
+            }
+            "memcopy" -> {
+                val source = args[0].array!!
+                val dest = args[1].array!!
+                val amount = args[2].integerValue()
+                for(i in 0 until amount) {
+                    dest[i] = source[i]
+                }
+                null
+            }
+            "mkword" -> {
+                val result = (args[1].integerValue() shl 8) or args[0].integerValue()
+                RuntimeValue(DataType.UWORD, result)
+            }
+            "set_carry" -> {
+                statusflags.carry=true
+                null
+            }
+            "clear_carry" -> {
+                statusflags.carry=false
+                null
+            }
+            "set_irqd" -> {
+                statusflags.irqd=true
+                null
+            }
+            "clear_irqd" -> {
+                statusflags.irqd=false
+                null
+            }
+            "read_flags" -> {
+                val carry = if(statusflags.carry) 1 else 0
+                val zero = if(statusflags.zero) 2 else 0
+                val irqd = if(statusflags.irqd) 4 else 0
+                val negative = if(statusflags.negative) 128 else 0
+                RuntimeValue(DataType.UBYTE, carry or zero or irqd or negative)
+            }
+            "rsave" -> {
+                statusFlagsSave.push(statusflags)
+                registerAsave.push(runtimeVariables.get(program.namespace, Register.A.name))
+                registerXsave.push(runtimeVariables.get(program.namespace, Register.X.name))
+                registerYsave.push(runtimeVariables.get(program.namespace, Register.Y.name))
+                null
+            }
+            "rrestore" -> {
+                val flags = statusFlagsSave.pop()
+                statusflags.carry = flags.carry
+                statusflags.negative = flags.negative
+                statusflags.zero = flags.zero
+                statusflags.irqd = flags.irqd
+                runtimeVariables.set(program.namespace, Register.A.name, registerAsave.pop())
+                runtimeVariables.set(program.namespace, Register.X.name, registerXsave.pop())
+                runtimeVariables.set(program.namespace, Register.Y.name, registerYsave.pop())
+                null
+            }
+            else -> TODO("builtin function $name")
+        }
+    }
+
 }
 
diff --git a/compiler/src/prog8/vm/astvm/BuiltinFunctions.kt b/compiler/src/prog8/vm/astvm/BuiltinFunctions.kt
deleted file mode 100644
index 2060252a5..000000000
--- a/compiler/src/prog8/vm/astvm/BuiltinFunctions.kt
+++ /dev/null
@@ -1,204 +0,0 @@
-package prog8.vm.astvm
-
-import prog8.ast.base.DataType
-import prog8.vm.RuntimeValue
-import java.lang.Math.toDegrees
-import java.lang.Math.toRadians
-import java.util.*
-import kotlin.math.*
-import kotlin.random.Random
-
-
-class BuiltinFunctions {
-
-    private val rnd = Random(0)
-    private val statusFlagsSave = Stack<StatusFlags>()
-
-
-    fun performBuiltinFunction(name: String, args: List<RuntimeValue>, statusflags: StatusFlags): RuntimeValue? {
-        return when (name) {
-            "rnd" -> RuntimeValue(DataType.UBYTE, rnd.nextInt() and 255)
-            "rndw" -> RuntimeValue(DataType.UWORD, rnd.nextInt() and 65535)
-            "rndf" -> RuntimeValue(DataType.FLOAT, rnd.nextDouble())
-            "lsb" -> RuntimeValue(DataType.UBYTE, args[0].integerValue() and 255)
-            "msb" -> RuntimeValue(DataType.UBYTE, (args[0].integerValue() ushr 8) and 255)
-            "sin" -> RuntimeValue(DataType.FLOAT, sin(args[0].numericValue().toDouble()))
-            "sin8" -> {
-                val rad = args[0].numericValue().toDouble() / 256.0 * 2.0 * PI
-                RuntimeValue(DataType.BYTE, (127.0 * sin(rad)).toShort())
-            }
-            "sin8u" -> {
-                val rad = args[0].numericValue().toDouble() / 256.0 * 2.0 * PI
-                RuntimeValue(DataType.UBYTE, (128.0 + 127.5 * sin(rad)).toShort())
-            }
-            "sin16" -> {
-                val rad = args[0].numericValue().toDouble() / 256.0 * 2.0 * PI
-                RuntimeValue(DataType.BYTE, (32767.0 * sin(rad)).toShort())
-            }
-            "sin16u" -> {
-                val rad = args[0].numericValue().toDouble() / 256.0 * 2.0 * PI
-                RuntimeValue(DataType.UBYTE, (32768.0 + 32767.5 * sin(rad)).toShort())
-            }
-            "cos" -> RuntimeValue(DataType.FLOAT, cos(args[0].numericValue().toDouble()))
-            "cos8" -> {
-                val rad = args[0].numericValue().toDouble() / 256.0 * 2.0 * PI
-                RuntimeValue(DataType.BYTE, (127.0 * cos(rad)).toShort())
-            }
-            "cos8u" -> {
-                val rad = args[0].numericValue().toDouble() / 256.0 * 2.0 * PI
-                RuntimeValue(DataType.UBYTE, (128.0 + 127.5 * cos(rad)).toShort())
-            }
-            "cos16" -> {
-                val rad = args[0].numericValue().toDouble() / 256.0 * 2.0 * PI
-                RuntimeValue(DataType.BYTE, (32767.0 * cos(rad)).toShort())
-            }
-            "cos16u" -> {
-                val rad = args[0].numericValue().toDouble() / 256.0 * 2.0 * PI
-                RuntimeValue(DataType.UBYTE, (32768.0 + 32767.5 * cos(rad)).toShort())
-            }
-            "tan" -> RuntimeValue(DataType.FLOAT, tan(args[0].numericValue().toDouble()))
-            "atan" -> RuntimeValue(DataType.FLOAT, atan(args[0].numericValue().toDouble()))
-            "ln" -> RuntimeValue(DataType.FLOAT, ln(args[0].numericValue().toDouble()))
-            "log2" -> RuntimeValue(DataType.FLOAT, log2(args[0].numericValue().toDouble()))
-            "sqrt" -> RuntimeValue(DataType.FLOAT, sqrt(args[0].numericValue().toDouble()))
-            "sqrt16" -> RuntimeValue(DataType.UBYTE, sqrt(args[0].wordval!!.toDouble()).toInt())
-            "rad" -> RuntimeValue(DataType.FLOAT, toRadians(args[0].numericValue().toDouble()))
-            "deg" -> RuntimeValue(DataType.FLOAT, toDegrees(args[0].numericValue().toDouble()))
-            "round" -> RuntimeValue(DataType.FLOAT, round(args[0].numericValue().toDouble()))
-            "floor" -> RuntimeValue(DataType.FLOAT, floor(args[0].numericValue().toDouble()))
-            "ceil" -> RuntimeValue(DataType.FLOAT, ceil(args[0].numericValue().toDouble()))
-            "rol" -> {
-                val (result, newCarry) = args[0].rol(statusflags.carry)
-                statusflags.carry = newCarry
-                return result
-            }
-            "rol2" -> args[0].rol2()
-            "ror" -> {
-                val (result, newCarry) = args[0].ror(statusflags.carry)
-                statusflags.carry = newCarry
-                return result
-            }
-            "ror2" -> args[0].ror2()
-            "lsl" -> args[0].shl()
-            "lsr" -> args[0].shr()
-            "abs" -> {
-                when (args[0].type) {
-                    DataType.UBYTE -> args[0]
-                    DataType.BYTE -> RuntimeValue(DataType.UBYTE, abs(args[0].numericValue().toDouble()))
-                    DataType.UWORD -> args[0]
-                    DataType.WORD -> RuntimeValue(DataType.UWORD, abs(args[0].numericValue().toDouble()))
-                    DataType.FLOAT -> RuntimeValue(DataType.FLOAT, abs(args[0].numericValue().toDouble()))
-                    else -> TODO("strange abs type")
-                }
-            }
-            "max" -> {
-                val numbers = args.map { it.numericValue().toDouble() }
-                RuntimeValue(args[0].type, numbers.max())
-            }
-            "min" -> {
-                val numbers = args.map { it.numericValue().toDouble() }
-                RuntimeValue(args[0].type, numbers.min())
-            }
-            "avg" -> {
-                val numbers = args.map { it.numericValue().toDouble() }
-                RuntimeValue(DataType.FLOAT, numbers.average())
-            }
-            "sum" -> {
-                val sum = args.map { it.numericValue().toDouble() }.sum()
-                when (args[0].type) {
-                    DataType.UBYTE -> RuntimeValue(DataType.UWORD, sum)
-                    DataType.BYTE -> RuntimeValue(DataType.WORD, sum)
-                    DataType.UWORD -> RuntimeValue(DataType.UWORD, sum)
-                    DataType.WORD -> RuntimeValue(DataType.WORD, sum)
-                    DataType.FLOAT -> RuntimeValue(DataType.FLOAT, sum)
-                    else -> TODO("weird sum type")
-                }
-            }
-            "any" -> {
-                val numbers = args.map { it.numericValue().toDouble() }
-                RuntimeValue(DataType.UBYTE, if (numbers.any { it != 0.0 }) 1 else 0)
-            }
-            "all" -> {
-                val numbers = args.map { it.numericValue().toDouble() }
-                RuntimeValue(DataType.UBYTE, if (numbers.all { it != 0.0 }) 1 else 0)
-            }
-            "swap" ->
-                throw VmExecutionException("swap() cannot be implemented as a function")
-            "strlen" -> {
-                val zeroIndex = args[0].str!!.indexOf(0.toChar())
-                if (zeroIndex >= 0)
-                    RuntimeValue(DataType.UBYTE, zeroIndex)
-                else
-                    RuntimeValue(DataType.UBYTE, args[0].str!!.length)
-            }
-            "memset" -> {
-                val target = args[0].array!!
-                val amount = args[1].integerValue()
-                val value = args[2].integerValue()
-                for (i in 0 until amount) {
-                    target[i] = value
-                }
-                null
-            }
-            "memsetw" -> {
-                val target = args[0].array!!
-                val amount = args[1].integerValue()
-                val value = args[2].integerValue()
-                for (i in 0 until amount step 2) {
-                    target[i * 2] = value and 255
-                    target[i * 2 + 1] = value ushr 8
-                }
-                null
-            }
-            "memcopy" -> {
-                val source = args[0].array!!
-                val dest = args[1].array!!
-                val amount = args[2].integerValue()
-                for(i in 0 until amount) {
-                    dest[i] = source[i]
-                }
-                null
-            }
-            "mkword" -> {
-                val result = (args[1].integerValue() shl 8) or args[0].integerValue()
-                RuntimeValue(DataType.UWORD, result)
-            }
-            "set_carry" -> {
-                statusflags.carry=true
-                null
-            }
-            "clear_carry" -> {
-                statusflags.carry=false
-                null
-            }
-            "set_irqd" -> {
-                statusflags.irqd=true
-                null
-            }
-            "clear_irqd" -> {
-                statusflags.irqd=false
-                null
-            }
-            "read_flags" -> {
-                val carry = if(statusflags.carry) 1 else 0
-                val zero = if(statusflags.zero) 2 else 0
-                val irqd = if(statusflags.irqd) 4 else 0
-                val negative = if(statusflags.negative) 128 else 0
-                RuntimeValue(DataType.UBYTE, carry or zero or irqd or negative)
-            }
-            "rsave" -> {
-                statusFlagsSave.push(statusflags)
-                null
-            }
-            "rrestore" -> {
-                val flags = statusFlagsSave.pop()
-                statusflags.carry = flags.carry
-                statusflags.negative = flags.negative
-                statusflags.zero = flags.zero
-                statusflags.irqd = flags.irqd
-                null
-            }
-            else -> TODO("builtin function $name")
-        }
-    }
-}
diff --git a/compiler/src/prog8/vm/astvm/Expressions.kt b/compiler/src/prog8/vm/astvm/Expressions.kt
index d2eccdd0e..1afbbc66c 100644
--- a/compiler/src/prog8/vm/astvm/Expressions.kt
+++ b/compiler/src/prog8/vm/astvm/Expressions.kt
@@ -14,7 +14,8 @@ import prog8.vm.RuntimeValueRange
 import kotlin.math.abs
 
 class EvalContext(val program: Program, val mem: Memory, val statusflags: StatusFlags,
-                  val runtimeVars: RuntimeVariables, val functions: BuiltinFunctions,
+                  val runtimeVars: RuntimeVariables,
+                  val performBuiltinFunction: (String, List<RuntimeValue>, StatusFlags) -> RuntimeValue?,
                   val executeSubroutine: (sub: Subroutine, args: List<RuntimeValue>, startlabel: Label?) -> List<RuntimeValue>)
 
 fun evaluate(expr: IExpression, ctx: EvalContext): RuntimeValue {
@@ -122,7 +123,7 @@ fun evaluate(expr: IExpression, ctx: EvalContext): RuntimeValue {
                     results[0]
                 }
                 is BuiltinFunctionStatementPlaceholder -> {
-                    val result = ctx.functions.performBuiltinFunction(sub.name, args, ctx.statusflags)
+                    val result = ctx.performBuiltinFunction(sub.name, args, ctx.statusflags)
                             ?: throw VmExecutionException("expected 1 result from functioncall $expr")
                     result
                 }
diff --git a/compiler/src/prog8/vm/stackvm/StackVm.kt b/compiler/src/prog8/vm/stackvm/StackVm.kt
index c33675629..302f0c192 100644
--- a/compiler/src/prog8/vm/stackvm/StackVm.kt
+++ b/compiler/src/prog8/vm/stackvm/StackVm.kt
@@ -1863,8 +1863,8 @@ class StackVm(private var traceOutputFile: String?) {
             }
             Opcode.RRESTORE -> {
                 variables["A"] = evalstack.pop()
-                variables["X"] = evalstack.pop()
                 variables["Y"] = evalstack.pop()
+                variables["X"] = evalstack.pop()
                 P_carry = evalstack.pop().asBoolean
                 P_irqd = evalstack.pop().asBoolean
             }
diff --git a/examples/test.p8 b/examples/test.p8
index d6516b9cb..13f7f63ff 100644
--- a/examples/test.p8
+++ b/examples/test.p8
@@ -4,14 +4,39 @@
 ~ main {
 
     sub start() {
-        c64scr.print("you start here! --> S\n")
-        for A in 0 to 16 {
-            for Y in 0 to 39 {
-                if rnd() >128 c64.CHROUT(109)
-                else c64.CHROUT(110)
-            }
+        A=0
+        Y=0
+        ubyte aa =0
+
+        while Y<10 {
+            rsave()
+            c64scr.print_ub(Y)
+            c64.CHROUT(',')
+            rrestore()
+            Y++
         }
-        c64scr.print("      x <-- try to find your way here!")
+        c64.CHROUT('!')
+        c64.CHROUT('!')
+        c64.CHROUT('\n')
+
+;        repeat {
+;            c64scr.print_ub(A)
+;            c64.CHROUT(',')
+;            A--
+;        } until A<5
+;
+;        c64.CHROUT('!')
+;        c64.CHROUT('!')
+;        c64.CHROUT('\n')
+;
+;        for A in 0 to 4 {
+;            for Y in 0 to 3 {
+;                c64scr.print_ub(A)
+;                c64.CHROUT(',')
+;                c64scr.print_ub(Y)
+;                c64.CHROUT('\n')
+;            }
+;        }
     }
 
 }