Optimize cmd VM with scoped slot addressing

lynglib/src/androidMain/kotlin/net/sergeych/lyng/PerfDefaults.android.kt

@@ -42,4 +42,4 @@ actual object PerfDefaults {
     actual val ARG_SMALL_ARITY_12: Boolean = false
     actual val INDEX_PIC_SIZE_4: Boolean = false
     actual val RANGE_FAST_ITER: Boolean = false
-}
+}

lynglib/src/androidMain/kotlin/net/sergeych/lyng/bytecode/CmdCallSiteCacheAndroid.kt

@@ -18,12 +18,12 @@ package net.sergeych.lyng.bytecode
 
 import java.util.IdentityHashMap
 
-internal actual object BytecodeCallSiteCache {
+internal actual object CmdCallSiteCache {
     private val cache = ThreadLocal.withInitial {
-        IdentityHashMap<BytecodeFunction, MutableMap<Int, MethodCallSite>>()
+        IdentityHashMap<CmdFunction, MutableMap<Int, MethodCallSite>>()
     }
 
-    actual fun methodCallSites(fn: BytecodeFunction): MutableMap<Int, MethodCallSite> {
+    actual fun methodCallSites(fn: CmdFunction): MutableMap<Int, MethodCallSite> {
         val map = cache.get()
         return map.getOrPut(fn) { mutableMapOf() }
     }

lynglib/src/commonMain/kotlin/net/sergeych/lyng/Compiler.kt

@@ -373,7 +373,8 @@ class Compiler(
 
     private fun wrapBytecode(stmt: Statement): Statement {
         if (!useBytecodeStatements) return stmt
-        return BytecodeStatement.wrap(stmt, "stmt@${stmt.pos}", allowLocalSlots = true)
+        val allowLocals = codeContexts.lastOrNull() is CodeContext.Function
+        return BytecodeStatement.wrap(stmt, "stmt@${stmt.pos}", allowLocalSlots = allowLocals)
     }
 
     private fun wrapFunctionBytecode(stmt: Statement, name: String): Statement {
@@ -381,6 +382,27 @@ class Compiler(
         return BytecodeStatement.wrap(stmt, "fn@$name", allowLocalSlots = true)
     }
 
+    private fun containsUnsupportedForBytecode(stmt: Statement): Boolean {
+        val target = if (stmt is BytecodeStatement) stmt.original else stmt
+        return when (target) {
+            is ExpressionStatement -> false
+            is IfStatement -> {
+                containsUnsupportedForBytecode(target.condition) ||
+                    containsUnsupportedForBytecode(target.ifBody) ||
+                    (target.elseBody?.let { containsUnsupportedForBytecode(it) } ?: false)
+            }
+            is ForInStatement -> {
+                target.constRange == null || target.canBreak ||
+                    containsUnsupportedForBytecode(target.source) ||
+                    containsUnsupportedForBytecode(target.body) ||
+                    (target.elseStatement?.let { containsUnsupportedForBytecode(it) } ?: false)
+            }
+            is BlockStatement -> target.statements().any { containsUnsupportedForBytecode(it) }
+            is VarDeclStatement -> target.initializer?.let { containsUnsupportedForBytecode(it) } ?: false
+            else -> true
+        }
+    }
+
     private fun unwrapBytecodeDeep(stmt: Statement): Statement {
         return when (stmt) {
             is BytecodeStatement -> unwrapBytecodeDeep(stmt.original)
@@ -397,6 +419,8 @@ class Compiler(
                     stmt.visibility,
                     init,
                     stmt.isTransient,
+                    stmt.slotIndex,
+                    stmt.slotDepth,
                     stmt.pos
                 )
             }
@@ -859,7 +883,7 @@ class Compiler(
 
         label?.let { cc.labels.add(it) }
         slotPlanStack.add(paramSlotPlan)
-        val body = try {
+        val parsedBody = try {
             inCodeContext(CodeContext.Function("<lambda>")) {
                 withLocalNames(slotParamNames.toSet()) {
                     parseBlock(skipLeadingBrace = true)
@@ -868,6 +892,7 @@ class Compiler(
         } finally {
             slotPlanStack.removeLast()
         }
+        val body = unwrapBytecodeDeep(parsedBody)
         label?.let { cc.labels.remove(it) }
 
         val paramSlotPlanSnapshot = slotPlanIndices(paramSlotPlan)
@@ -1494,15 +1519,20 @@ class Compiler(
                         val slotLoc = lookupSlotLocation(t.value)
                         val inClassCtx = codeContexts.any { it is CodeContext.ClassBody }
                         when {
-                            slotLoc != null -> LocalSlotRef(
+                            slotLoc != null -> {
-                                t.value,
+                                val scopeDepth = slotPlanStack.size - 1 - slotLoc.depth
-                                slotLoc.slot,
+                                LocalSlotRef(
-                                slotLoc.depth,
+                                    t.value,
-                                slotLoc.isMutable,
+                                    slotLoc.slot,
-                                slotLoc.isDelegated,
+                                    slotLoc.depth,
-                                t.pos
+                                    scopeDepth,
-                            )
+                                    slotLoc.isMutable,
-                            PerfFlags.EMIT_FAST_LOCAL_REFS && (currentLocalNames?.contains(t.value) == true) ->
+                                    slotLoc.isDelegated,
+                                    t.pos
+                                )
+                            }
+                            PerfFlags.EMIT_FAST_LOCAL_REFS && !useBytecodeStatements &&
+                                (currentLocalNames?.contains(t.value) == true) ->
                                 FastLocalVarRef(t.value, t.pos)
                             inClassCtx -> ImplicitThisMemberRef(t.value, t.pos)
                             else -> LocalVarRef(t.value, t.pos)
@@ -2041,7 +2071,19 @@ class Compiler(
     )
 
     private suspend fun parseTryStatement(): Statement {
-        val body = parseBlock()
+        fun withCatchSlot(block: Statement, catchName: String): Statement {
+            val stmt = block as? BlockStatement ?: return block
+            if (stmt.slotPlan.containsKey(catchName)) return stmt
+            val basePlan = stmt.slotPlan
+            val newPlan = LinkedHashMap<String, Int>(basePlan.size + 1)
+            newPlan[catchName] = 0
+            for ((name, idx) in basePlan) {
+                newPlan[name] = idx + 1
+            }
+            return BlockStatement(stmt.block, newPlan, stmt.pos)
+        }
+
+        val body = unwrapBytecodeDeep(parseBlock())
         val catches = mutableListOf<CatchBlockData>()
         cc.skipTokens(Token.Type.NEWLINE)
         var t = cc.next()
@@ -2078,7 +2120,7 @@ class Compiler(
                     exClassNames += "Exception"
                     cc.skipTokenOfType(Token.Type.RPAREN)
                 }
-                val block = parseBlock()
+                val block = withCatchSlot(unwrapBytecodeDeep(parseBlock()), catchVar.value)
                 catches += CatchBlockData(catchVar, exClassNames, block)
                 cc.skipTokens(Token.Type.NEWLINE)
                 t = cc.next()
@@ -2087,13 +2129,13 @@ class Compiler(
                 cc.skipTokenOfType(Token.Type.LBRACE, "expected catch(...) or catch { ... } here")
                 catches += CatchBlockData(
                     Token("it", cc.currentPos(), Token.Type.ID), listOf("Exception"),
-                    parseBlock(true)
+                    withCatchSlot(unwrapBytecodeDeep(parseBlock(true)), "it")
                 )
                 t = cc.next()
             }
         }
         val finallyClause = if (t.value == "finally") {
-            parseBlock()
+            unwrapBytecodeDeep(parseBlock())
         } else {
             cc.previous()
             null
@@ -2133,7 +2175,9 @@ class Compiler(
                             }
                         }
                         if (match != null) {
-                            val catchContext = scope.createChildScope(pos = cdata.catchVar.pos)
+                            val catchContext = scope.createChildScope(pos = cdata.catchVar.pos).apply {
+                                skipScopeCreation = true
+                            }
                             catchContext.addItem(cdata.catchVar.value, false, caughtObj)
                             result = cdata.block.execute(catchContext)
                             isCaught = true
@@ -3020,7 +3064,7 @@ class Compiler(
             currentLocalDeclCount
             localDeclCountStack.add(0)
             slotPlanStack.add(paramSlotPlan)
-            val fnStatements = try {
+            val parsedFnStatements = try {
                 if (actualExtern)
                     object : Statement() {
                         override val pos: Pos = start
@@ -3050,6 +3094,9 @@ class Compiler(
             } finally {
                 slotPlanStack.removeLast()
             }
+            val fnStatements = parsedFnStatements?.let {
+                if (containsUnsupportedForBytecode(it)) unwrapBytecodeDeep(it) else it
+            }
             // Capture and pop the local declarations count for this function
             val fnLocalDecls = localDeclCountStack.removeLastOrNull() ?: 0
 
@@ -3528,7 +3575,10 @@ class Compiler(
             !actualExtern &&
             !isAbstract
         ) {
-            return VarDeclStatement(name, isMutable, visibility, initialExpression, isTransient, start)
+            val slotPlan = slotPlanStack.lastOrNull()
+            val slotIndex = slotPlan?.slots?.get(name)?.index
+            val slotDepth = slotPlan?.let { slotPlanStack.size - 1 }
+            return VarDeclStatement(name, isMutable, visibility, initialExpression, isTransient, slotIndex, slotDepth, start)
         }
 
         if (isStatic) {

lynglib/src/commonMain/kotlin/net/sergeych/lyng/PerfFlags.kt

@@ -72,4 +72,5 @@ object PerfFlags {
 
     // Specialized non-allocating integer range iteration in hot loops
     var RANGE_FAST_ITER: Boolean = PerfDefaults.RANGE_FAST_ITER
+
 }

lynglib/src/commonMain/kotlin/net/sergeych/lyng/Scope.kt

@@ -18,7 +18,7 @@
 package net.sergeych.lyng
 
 import net.sergeych.lyng.obj.*
-import net.sergeych.lyng.bytecode.BytecodeDisassembler
+import net.sergeych.lyng.bytecode.CmdDisassembler
 import net.sergeych.lyng.bytecode.BytecodeStatement
 import net.sergeych.lyng.pacman.ImportManager
 import net.sergeych.lyng.pacman.ImportProvider
@@ -339,6 +339,8 @@ open class Scope(
 
     internal val objects = mutableMapOf<String, ObjRecord>()
 
+    internal fun getLocalRecordDirect(name: String): ObjRecord? = objects[name]
+
     open operator fun get(name: String): ObjRecord? {
         if (name == "this") return thisObj.asReadonly
 
@@ -381,6 +383,8 @@ open class Scope(
     fun setSlotValue(index: Int, newValue: Obj) {
         slots[index].value = newValue
     }
+    val slotCount: Int
+        get() = slots.size
 
     fun getSlotIndexOf(name: String): Int? = nameToSlot[name]
     fun allocateSlotFor(name: String, record: ObjRecord): Int {
@@ -440,6 +444,20 @@ open class Scope(
         }
     }
 
+    fun hasSlotPlanConflict(plan: Map<String, Int>): Boolean {
+        if (plan.isEmpty() || nameToSlot.isEmpty()) return false
+        val planIndexToNames = HashMap<Int, HashSet<String>>(plan.size)
+        for ((name, idx) in plan) {
+            val names = planIndexToNames.getOrPut(idx) { HashSet(2) }
+            names.add(name)
+        }
+        for ((existingName, existingIndex) in nameToSlot) {
+            val plannedNames = planIndexToNames[existingIndex] ?: continue
+            if (!plannedNames.contains(existingName)) return true
+        }
+        return false
+    }
+
     /**
      * Clear all references and maps to prevent memory leaks when pooled.
      */
@@ -651,7 +669,7 @@ open class Scope(
         val bytecode = (stmt as? BytecodeStatement)?.bytecodeFunction()
             ?: (stmt as? BytecodeBodyProvider)?.bytecodeBody()?.bytecodeFunction()
             ?: return "$name is not a compiled body"
-        return BytecodeDisassembler.disassemble(bytecode)
+        return CmdDisassembler.disassemble(bytecode)
     }
 
     fun addFn(vararg names: String, fn: suspend Scope.() -> Obj) {

lynglib/src/commonMain/kotlin/net/sergeych/lyng/VarDeclStatement.kt

@@ -26,6 +26,8 @@ class VarDeclStatement(
     val visibility: Visibility,
     val initializer: Statement?,
     val isTransient: Boolean,
+    val slotIndex: Int?,
+    val slotDepth: Int?,
     private val startPos: Pos,
 ) : Statement() {
     override val pos: Pos = startPos

lynglib/src/commonMain/kotlin/net/sergeych/lyng/bytecode/BytecodeBuilder.kt

@@ -1,222 +0,0 @@
-/*
- * Copyright 2026 Sergey S. Chernov
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package net.sergeych.lyng.bytecode
-
-class BytecodeBuilder {
-    sealed interface Operand {
-        data class IntVal(val value: Int) : Operand
-        data class LabelRef(val label: Label) : Operand
-    }
-
-    data class Label(val id: Int)
-
-    data class Instr(val op: Opcode, val operands: List<Operand>)
-
-    private val instructions = mutableListOf<Instr>()
-    private val constPool = mutableListOf<BytecodeConst>()
-    private val labelPositions = mutableMapOf<Label, Int>()
-    private var nextLabelId = 0
-    private val fallbackStatements = mutableListOf<net.sergeych.lyng.Statement>()
-
-    fun addConst(c: BytecodeConst): Int {
-        constPool += c
-        return constPool.lastIndex
-    }
-
-    fun emit(op: Opcode, vararg operands: Int) {
-        instructions += Instr(op, operands.map { Operand.IntVal(it) })
-    }
-
-    fun emit(op: Opcode, operands: List<Operand>) {
-        instructions += Instr(op, operands)
-    }
-
-    fun label(): Label = Label(nextLabelId++)
-
-    fun mark(label: Label) {
-        labelPositions[label] = instructions.size
-    }
-
-    fun addFallback(stmt: net.sergeych.lyng.Statement): Int {
-        fallbackStatements += stmt
-        return fallbackStatements.lastIndex
-    }
-
-    fun build(
-        name: String,
-        localCount: Int,
-        scopeSlotDepths: IntArray = IntArray(0),
-        scopeSlotIndices: IntArray = IntArray(0),
-        scopeSlotNames: Array<String?> = emptyArray()
-    ): BytecodeFunction {
-        val scopeSlotCount = scopeSlotDepths.size
-        require(scopeSlotIndices.size == scopeSlotCount) { "scope slot mapping size mismatch" }
-        require(scopeSlotNames.isEmpty() || scopeSlotNames.size == scopeSlotCount) {
-            "scope slot name mapping size mismatch"
-        }
-        val totalSlots = localCount + scopeSlotCount
-        val slotWidth = when {
-            totalSlots < 256 -> 1
-            totalSlots < 65536 -> 2
-            else -> 4
-        }
-        val constIdWidth = if (constPool.size < 65536) 2 else 4
-        val ipWidth = 2
-        val instrOffsets = IntArray(instructions.size)
-        var currentIp = 0
-        for (i in instructions.indices) {
-            instrOffsets[i] = currentIp
-            val kinds = operandKinds(instructions[i].op)
-            currentIp += 1 + kinds.sumOf { operandWidth(it, slotWidth, constIdWidth, ipWidth) }
-        }
-        val labelIps = mutableMapOf<Label, Int>()
-        for ((label, idx) in labelPositions) {
-            labelIps[label] = instrOffsets.getOrNull(idx) ?: error("Invalid label index: $idx")
-        }
-
-        val code = ByteArrayOutput()
-        for (ins in instructions) {
-            code.writeU8(ins.op.code and 0xFF)
-            val kinds = operandKinds(ins.op)
-            if (kinds.size != ins.operands.size) {
-                error("Operand count mismatch for ${ins.op}: expected ${kinds.size}, got ${ins.operands.size}")
-            }
-            for (i in kinds.indices) {
-                val operand = ins.operands[i]
-                val v = when (operand) {
-                    is Operand.IntVal -> operand.value
-                    is Operand.LabelRef -> labelIps[operand.label]
-                        ?: error("Unknown label ${operand.label.id} for ${ins.op}")
-                }
-                when (kinds[i]) {
-                    OperandKind.SLOT -> code.writeUInt(v, slotWidth)
-                    OperandKind.CONST -> code.writeUInt(v, constIdWidth)
-                    OperandKind.IP -> code.writeUInt(v, ipWidth)
-                    OperandKind.COUNT -> code.writeUInt(v, 2)
-                    OperandKind.ID -> code.writeUInt(v, 2)
-                }
-            }
-        }
-        return BytecodeFunction(
-            name = name,
-            localCount = localCount,
-            scopeSlotCount = scopeSlotCount,
-            scopeSlotDepths = scopeSlotDepths,
-            scopeSlotIndices = scopeSlotIndices,
-            scopeSlotNames = if (scopeSlotNames.isEmpty()) Array(scopeSlotCount) { null } else scopeSlotNames,
-            slotWidth = slotWidth,
-            ipWidth = ipWidth,
-            constIdWidth = constIdWidth,
-            constants = constPool.toList(),
-            fallbackStatements = fallbackStatements.toList(),
-            code = code.toByteArray()
-        )
-    }
-
-    private fun operandKinds(op: Opcode): List<OperandKind> {
-        return when (op) {
-            Opcode.NOP, Opcode.RET_VOID, Opcode.POP_SCOPE, Opcode.POP_SLOT_PLAN -> emptyList()
-            Opcode.MOVE_OBJ, Opcode.MOVE_INT, Opcode.MOVE_REAL, Opcode.MOVE_BOOL, Opcode.BOX_OBJ,
-            Opcode.INT_TO_REAL, Opcode.REAL_TO_INT, Opcode.BOOL_TO_INT, Opcode.INT_TO_BOOL,
-            Opcode.NEG_INT, Opcode.NEG_REAL, Opcode.NOT_BOOL, Opcode.INV_INT ->
-                listOf(OperandKind.SLOT, OperandKind.SLOT)
-            Opcode.CONST_NULL ->
-                listOf(OperandKind.SLOT)
-            Opcode.CONST_OBJ, Opcode.CONST_INT, Opcode.CONST_REAL, Opcode.CONST_BOOL ->
-                listOf(OperandKind.CONST, OperandKind.SLOT)
-            Opcode.PUSH_SCOPE, Opcode.PUSH_SLOT_PLAN ->
-                listOf(OperandKind.CONST)
-            Opcode.DECL_LOCAL ->
-                listOf(OperandKind.CONST, OperandKind.SLOT)
-            Opcode.ADD_INT, Opcode.SUB_INT, Opcode.MUL_INT, Opcode.DIV_INT, Opcode.MOD_INT,
-            Opcode.ADD_REAL, Opcode.SUB_REAL, Opcode.MUL_REAL, Opcode.DIV_REAL,
-            Opcode.AND_INT, Opcode.OR_INT, Opcode.XOR_INT, Opcode.SHL_INT, Opcode.SHR_INT, Opcode.USHR_INT,
-            Opcode.CMP_EQ_INT, Opcode.CMP_NEQ_INT, Opcode.CMP_LT_INT, Opcode.CMP_LTE_INT,
-            Opcode.CMP_GT_INT, Opcode.CMP_GTE_INT,
-            Opcode.CMP_EQ_REAL, Opcode.CMP_NEQ_REAL, Opcode.CMP_LT_REAL, Opcode.CMP_LTE_REAL,
-            Opcode.CMP_GT_REAL, Opcode.CMP_GTE_REAL,
-            Opcode.CMP_EQ_BOOL, Opcode.CMP_NEQ_BOOL,
-            Opcode.CMP_EQ_INT_REAL, Opcode.CMP_EQ_REAL_INT, Opcode.CMP_LT_INT_REAL, Opcode.CMP_LT_REAL_INT,
-            Opcode.CMP_LTE_INT_REAL, Opcode.CMP_LTE_REAL_INT, Opcode.CMP_GT_INT_REAL, Opcode.CMP_GT_REAL_INT,
-            Opcode.CMP_GTE_INT_REAL, Opcode.CMP_GTE_REAL_INT, Opcode.CMP_NEQ_INT_REAL, Opcode.CMP_NEQ_REAL_INT,
-            Opcode.CMP_EQ_OBJ, Opcode.CMP_NEQ_OBJ, Opcode.CMP_REF_EQ_OBJ, Opcode.CMP_REF_NEQ_OBJ,
-            Opcode.CMP_LT_OBJ, Opcode.CMP_LTE_OBJ, Opcode.CMP_GT_OBJ, Opcode.CMP_GTE_OBJ,
-            Opcode.ADD_OBJ, Opcode.SUB_OBJ, Opcode.MUL_OBJ, Opcode.DIV_OBJ, Opcode.MOD_OBJ,
-            Opcode.AND_BOOL, Opcode.OR_BOOL ->
-                listOf(OperandKind.SLOT, OperandKind.SLOT, OperandKind.SLOT)
-            Opcode.INC_INT, Opcode.DEC_INT, Opcode.RET ->
-                listOf(OperandKind.SLOT)
-            Opcode.JMP ->
-                listOf(OperandKind.IP)
-            Opcode.JMP_IF_TRUE, Opcode.JMP_IF_FALSE ->
-                listOf(OperandKind.SLOT, OperandKind.IP)
-            Opcode.CALL_DIRECT, Opcode.CALL_FALLBACK ->
-                listOf(OperandKind.ID, OperandKind.SLOT, OperandKind.COUNT, OperandKind.SLOT)
-            Opcode.CALL_SLOT ->
-                listOf(OperandKind.SLOT, OperandKind.SLOT, OperandKind.COUNT, OperandKind.SLOT)
-            Opcode.CALL_VIRTUAL ->
-                listOf(OperandKind.SLOT, OperandKind.ID, OperandKind.SLOT, OperandKind.COUNT, OperandKind.SLOT)
-            Opcode.GET_FIELD ->
-                listOf(OperandKind.SLOT, OperandKind.ID, OperandKind.SLOT)
-            Opcode.SET_FIELD ->
-                listOf(OperandKind.SLOT, OperandKind.ID, OperandKind.SLOT)
-            Opcode.GET_INDEX ->
-                listOf(OperandKind.SLOT, OperandKind.SLOT, OperandKind.SLOT)
-            Opcode.SET_INDEX ->
-                listOf(OperandKind.SLOT, OperandKind.SLOT, OperandKind.SLOT)
-            Opcode.EVAL_FALLBACK ->
-                listOf(OperandKind.ID, OperandKind.SLOT)
-        }
-    }
-
-    private fun operandWidth(kind: OperandKind, slotWidth: Int, constIdWidth: Int, ipWidth: Int): Int {
-        return when (kind) {
-            OperandKind.SLOT -> slotWidth
-            OperandKind.CONST -> constIdWidth
-            OperandKind.IP -> ipWidth
-            OperandKind.COUNT -> 2
-            OperandKind.ID -> 2
-        }
-    }
-
-    private enum class OperandKind {
-        SLOT,
-        CONST,
-        IP,
-        COUNT,
-        ID,
-    }
-
-    private class ByteArrayOutput {
-        private val data = ArrayList<Byte>(256)
-
-        fun writeU8(v: Int) {
-            data.add((v and 0xFF).toByte())
-        }
-
-        fun writeUInt(v: Int, width: Int) {
-            var value = v
-            var remaining = width
-            while (remaining-- > 0) {
-                writeU8(value)
-                value = value ushr 8
-            }
-        }
-
-        fun toByteArray(): ByteArray = data.toByteArray()
-    }
-}

lynglib/src/commonMain/kotlin/net/sergeych/lyng/bytecode/BytecodeCompiler.kt

@@ -29,21 +29,28 @@ import net.sergeych.lyng.obj.*
 class BytecodeCompiler(
     private val allowLocalSlots: Boolean = true,
 ) {
-    private var builder = BytecodeBuilder()
+    private var builder = CmdBuilder()
     private var nextSlot = 0
+    private var nextAddrSlot = 0
     private var scopeSlotCount = 0
     private var scopeSlotDepths = IntArray(0)
     private var scopeSlotIndices = IntArray(0)
     private var scopeSlotNames = emptyArray<String?>()
     private val scopeSlotMap = LinkedHashMap<ScopeSlotKey, Int>()
     private val scopeSlotNameMap = LinkedHashMap<ScopeSlotKey, String>()
+    private val addrSlotByScopeSlot = LinkedHashMap<Int, Int>()
+    private data class LocalSlotInfo(val name: String, val isMutable: Boolean, val depth: Int)
+    private val localSlotInfoMap = LinkedHashMap<ScopeSlotKey, LocalSlotInfo>()
+    private val localSlotIndexByKey = LinkedHashMap<ScopeSlotKey, Int>()
+    private val localSlotIndexByName = LinkedHashMap<String, Int>()
+    private var localSlotNames = emptyArray<String?>()
+    private var localSlotMutables = BooleanArray(0)
+    private var localSlotDepths = IntArray(0)
+    private val declaredLocalKeys = LinkedHashSet<ScopeSlotKey>()
     private val slotTypes = mutableMapOf<Int, SlotType>()
     private val intLoopVarNames = LinkedHashSet<String>()
-    private val loopVarNames = LinkedHashSet<String>()
-    private val loopVarSlotIndexByName = LinkedHashMap<String, Int>()
-    private val loopVarSlotIdByName = LinkedHashMap<String, Int>()
 
-    fun compileStatement(name: String, stmt: net.sergeych.lyng.Statement): BytecodeFunction? {
+    fun compileStatement(name: String, stmt: net.sergeych.lyng.Statement): CmdFunction? {
         prepareCompilation(stmt)
         return when (stmt) {
             is ExpressionStatement -> compileExpression(name, stmt)
@@ -55,12 +62,22 @@ class BytecodeCompiler(
         }
     }
 
-    fun compileExpression(name: String, stmt: ExpressionStatement): BytecodeFunction? {
+    fun compileExpression(name: String, stmt: ExpressionStatement): CmdFunction? {
         prepareCompilation(stmt)
         val value = compileRefWithFallback(stmt.ref, null, stmt.pos) ?: return null
         builder.emit(Opcode.RET, value.slot)
         val localCount = maxOf(nextSlot, value.slot + 1) - scopeSlotCount
-        return builder.build(name, localCount, scopeSlotDepths, scopeSlotIndices, scopeSlotNames)
+        return builder.build(
+            name,
+            localCount,
+            addrCount = nextAddrSlot,
+            scopeSlotDepths,
+            scopeSlotIndices,
+            scopeSlotNames,
+            localSlotNames,
+            localSlotMutables,
+            localSlotDepths
+        )
     }
 
     private data class CompiledValue(val slot: Int, val type: SlotType)
@@ -74,12 +91,18 @@ class BytecodeCompiler(
                 if (!allowLocalSlots) return null
                 if (ref.isDelegated) return null
                 if (ref.name.isEmpty()) return null
-                val loopSlotId = loopVarSlotIdByName[ref.name]
+                val mapped = resolveSlot(ref) ?: return null
-                val mapped = loopSlotId ?: scopeSlotMap[ScopeSlotKey(refDepth(ref), refSlot(ref))] ?: return null
+                var resolved = slotTypes[mapped] ?: SlotType.UNKNOWN
-                val resolved = slotTypes[mapped] ?: SlotType.UNKNOWN
                 if (resolved == SlotType.UNKNOWN && intLoopVarNames.contains(ref.name)) {
                     updateSlotType(mapped, SlotType.INT)
-                    return CompiledValue(mapped, SlotType.INT)
+                    resolved = SlotType.INT
+                }
+                if (mapped < scopeSlotCount && resolved != SlotType.UNKNOWN) {
+                    val addrSlot = ensureScopeAddr(mapped)
+                    val local = allocSlot()
+                    emitLoadFromAddr(addrSlot, local, resolved)
+                    updateSlotType(local, resolved)
+                    return CompiledValue(local, resolved)
                 }
                 CompiledValue(mapped, resolved)
             }
@@ -87,7 +110,7 @@ class BytecodeCompiler(
             is UnaryOpRef -> compileUnary(ref)
             is AssignRef -> compileAssign(ref)
             is AssignOpRef -> compileAssignOp(ref)
-            is IncDecRef -> compileIncDec(ref)
+            is IncDecRef -> compileIncDec(ref, true)
             is ConditionalRef -> compileConditional(ref)
             is ElvisRef -> compileElvis(ref)
             is CallRef -> compileCall(ref)
@@ -626,17 +649,17 @@ class BytecodeCompiler(
         if (op == BinOp.AND) {
             builder.emit(
                 Opcode.JMP_IF_FALSE,
-                listOf(BytecodeBuilder.Operand.IntVal(leftValue.slot), BytecodeBuilder.Operand.LabelRef(shortLabel))
+                listOf(CmdBuilder.Operand.IntVal(leftValue.slot), CmdBuilder.Operand.LabelRef(shortLabel))
             )
         } else {
             builder.emit(
                 Opcode.JMP_IF_TRUE,
-                listOf(BytecodeBuilder.Operand.IntVal(leftValue.slot), BytecodeBuilder.Operand.LabelRef(shortLabel))
+                listOf(CmdBuilder.Operand.IntVal(leftValue.slot), CmdBuilder.Operand.LabelRef(shortLabel))
             )
         }
         val rightValue = compileRefWithFallback(right, SlotType.BOOL, pos) ?: return null
         emitMove(rightValue, resultSlot)
-        builder.emit(Opcode.JMP, listOf(BytecodeBuilder.Operand.LabelRef(endLabel)))
+        builder.emit(Opcode.JMP, listOf(CmdBuilder.Operand.LabelRef(endLabel)))
         builder.mark(shortLabel)
         val constId = builder.addConst(BytecodeConst.Bool(op == BinOp.OR))
         builder.emit(Opcode.CONST_BOOL, constId, resultSlot)
@@ -648,27 +671,49 @@ class BytecodeCompiler(
         val target = assignTarget(ref) ?: return null
         if (!allowLocalSlots) return null
         if (!target.isMutable || target.isDelegated) return null
-        if (refDepth(target) > 0) return null
         val value = compileRef(assignValue(ref)) ?: return null
-        val slot = scopeSlotMap[ScopeSlotKey(refDepth(target), refSlot(target))] ?: return null
+        val slot = resolveSlot(target) ?: return null
-        when (value.type) {
+        if (slot < scopeSlotCount && value.type != SlotType.UNKNOWN) {
-            SlotType.INT -> builder.emit(Opcode.MOVE_INT, value.slot, slot)
+            val addrSlot = ensureScopeAddr(slot)
-            SlotType.REAL -> builder.emit(Opcode.MOVE_REAL, value.slot, slot)
+            emitStoreToAddr(value.slot, addrSlot, value.type)
-            SlotType.BOOL -> builder.emit(Opcode.MOVE_BOOL, value.slot, slot)
+        } else if (slot < scopeSlotCount) {
-            else -> builder.emit(Opcode.MOVE_OBJ, value.slot, slot)
+            val addrSlot = ensureScopeAddr(slot)
+            emitStoreToAddr(value.slot, addrSlot, SlotType.OBJ)
+        } else {
+            when (value.type) {
+                SlotType.INT -> builder.emit(Opcode.MOVE_INT, value.slot, slot)
+                SlotType.REAL -> builder.emit(Opcode.MOVE_REAL, value.slot, slot)
+                SlotType.BOOL -> builder.emit(Opcode.MOVE_BOOL, value.slot, slot)
+                else -> builder.emit(Opcode.MOVE_OBJ, value.slot, slot)
+            }
         }
         updateSlotType(slot, value.type)
-        return CompiledValue(slot, value.type)
+        return value
     }
 
     private fun compileAssignOp(ref: AssignOpRef): CompiledValue? {
         val target = ref.target as? LocalSlotRef ?: return null
         if (!allowLocalSlots) return null
         if (!target.isMutable || target.isDelegated) return null
-        if (refDepth(target) > 0) return null
+        val slot = resolveSlot(target) ?: return null
-        val slot = scopeSlotMap[ScopeSlotKey(refDepth(target), refSlot(target))] ?: return null
         val targetType = slotTypes[slot] ?: return null
         val rhs = compileRef(ref.value) ?: return null
+        if (slot < scopeSlotCount) {
+            val addrSlot = ensureScopeAddr(slot)
+            val current = allocSlot()
+            emitLoadFromAddr(addrSlot, current, targetType)
+            val result = when (ref.op) {
+                BinOp.PLUS -> compileAssignOpBinary(targetType, rhs, current, Opcode.ADD_INT, Opcode.ADD_REAL, Opcode.ADD_OBJ)
+                BinOp.MINUS -> compileAssignOpBinary(targetType, rhs, current, Opcode.SUB_INT, Opcode.SUB_REAL, Opcode.SUB_OBJ)
+                BinOp.STAR -> compileAssignOpBinary(targetType, rhs, current, Opcode.MUL_INT, Opcode.MUL_REAL, Opcode.MUL_OBJ)
+                BinOp.SLASH -> compileAssignOpBinary(targetType, rhs, current, Opcode.DIV_INT, Opcode.DIV_REAL, Opcode.DIV_OBJ)
+                BinOp.PERCENT -> compileAssignOpBinary(targetType, rhs, current, Opcode.MOD_INT, null, Opcode.MOD_OBJ)
+                else -> null
+            } ?: return null
+            emitStoreToAddr(current, addrSlot, result.type)
+            updateSlotType(slot, result.type)
+            return CompiledValue(current, result.type)
+        }
         val out = slot
         val result = when (ref.op) {
             BinOp.PLUS -> compileAssignOpBinary(targetType, rhs, out, Opcode.ADD_INT, Opcode.ADD_REAL, Opcode.ADD_OBJ)
@@ -733,15 +778,79 @@ class BytecodeCompiler(
         }
     }
 
-    private fun compileIncDec(ref: IncDecRef): CompiledValue? {
+    private fun compileIncDec(ref: IncDecRef, wantResult: Boolean): CompiledValue? {
         val target = ref.target as? LocalSlotRef ?: return null
         if (!allowLocalSlots) return null
         if (!target.isMutable || target.isDelegated) return null
-        val slot = scopeSlotMap[ScopeSlotKey(refDepth(target), refSlot(target))] ?: return null
+        val slot = resolveSlot(target) ?: return null
         val slotType = slotTypes[slot] ?: SlotType.UNKNOWN
+        if (slot < scopeSlotCount && slotType != SlotType.UNKNOWN) {
+            val addrSlot = ensureScopeAddr(slot)
+            val current = allocSlot()
+            emitLoadFromAddr(addrSlot, current, slotType)
+            val result = when (slotType) {
+                SlotType.INT -> {
+                    if (wantResult && ref.isPost) {
+                        val old = allocSlot()
+                        builder.emit(Opcode.MOVE_INT, current, old)
+                        builder.emit(if (ref.isIncrement) Opcode.INC_INT else Opcode.DEC_INT, current)
+                        emitStoreToAddr(current, addrSlot, SlotType.INT)
+                        CompiledValue(old, SlotType.INT)
+                    } else {
+                        builder.emit(if (ref.isIncrement) Opcode.INC_INT else Opcode.DEC_INT, current)
+                        emitStoreToAddr(current, addrSlot, SlotType.INT)
+                        CompiledValue(current, SlotType.INT)
+                    }
+                }
+                SlotType.REAL -> {
+                    val oneSlot = allocSlot()
+                    val oneId = builder.addConst(BytecodeConst.RealVal(1.0))
+                    builder.emit(Opcode.CONST_REAL, oneId, oneSlot)
+                    if (wantResult && ref.isPost) {
+                        val old = allocSlot()
+                        builder.emit(Opcode.MOVE_REAL, current, old)
+                        val op = if (ref.isIncrement) Opcode.ADD_REAL else Opcode.SUB_REAL
+                        builder.emit(op, current, oneSlot, current)
+                        emitStoreToAddr(current, addrSlot, SlotType.REAL)
+                        CompiledValue(old, SlotType.REAL)
+                    } else {
+                        val op = if (ref.isIncrement) Opcode.ADD_REAL else Opcode.SUB_REAL
+                        builder.emit(op, current, oneSlot, current)
+                        emitStoreToAddr(current, addrSlot, SlotType.REAL)
+                        CompiledValue(current, SlotType.REAL)
+                    }
+                }
+                SlotType.OBJ -> {
+                    val oneSlot = allocSlot()
+                    val oneId = builder.addConst(BytecodeConst.ObjRef(ObjInt.One))
+                    builder.emit(Opcode.CONST_OBJ, oneId, oneSlot)
+                    val boxed = allocSlot()
+                    builder.emit(Opcode.BOX_OBJ, current, boxed)
+                    if (wantResult && ref.isPost) {
+                        val result = allocSlot()
+                        val op = if (ref.isIncrement) Opcode.ADD_OBJ else Opcode.SUB_OBJ
+                        builder.emit(op, boxed, oneSlot, result)
+                        builder.emit(Opcode.MOVE_OBJ, result, boxed)
+                        emitStoreToAddr(boxed, addrSlot, SlotType.OBJ)
+                        updateSlotType(slot, SlotType.OBJ)
+                        CompiledValue(boxed, SlotType.OBJ)
+                    } else {
+                        val result = allocSlot()
+                        val op = if (ref.isIncrement) Opcode.ADD_OBJ else Opcode.SUB_OBJ
+                        builder.emit(op, boxed, oneSlot, result)
+                        builder.emit(Opcode.MOVE_OBJ, result, boxed)
+                        emitStoreToAddr(boxed, addrSlot, SlotType.OBJ)
+                        updateSlotType(slot, SlotType.OBJ)
+                        CompiledValue(result, SlotType.OBJ)
+                    }
+                }
+                else -> null
+            }
+            if (result != null) return result
+        }
         return when (slotType) {
             SlotType.INT -> {
-                if (ref.isPost) {
+                if (wantResult && ref.isPost) {
                     val old = allocSlot()
                     builder.emit(Opcode.MOVE_INT, slot, old)
                     builder.emit(if (ref.isIncrement) Opcode.INC_INT else Opcode.DEC_INT, slot)
@@ -755,7 +864,7 @@ class BytecodeCompiler(
                 val oneSlot = allocSlot()
                 val oneId = builder.addConst(BytecodeConst.RealVal(1.0))
                 builder.emit(Opcode.CONST_REAL, oneId, oneSlot)
-                if (ref.isPost) {
+                if (wantResult && ref.isPost) {
                     val old = allocSlot()
                     builder.emit(Opcode.MOVE_REAL, slot, old)
                     val op = if (ref.isIncrement) Opcode.ADD_REAL else Opcode.SUB_REAL
@@ -773,7 +882,7 @@ class BytecodeCompiler(
                 builder.emit(Opcode.CONST_OBJ, oneId, oneSlot)
                 val current = allocSlot()
                 builder.emit(Opcode.BOX_OBJ, slot, current)
-                if (ref.isPost) {
+                if (wantResult && ref.isPost) {
                     val result = allocSlot()
                     val op = if (ref.isIncrement) Opcode.ADD_OBJ else Opcode.SUB_OBJ
                     builder.emit(op, current, oneSlot, result)
@@ -790,7 +899,7 @@ class BytecodeCompiler(
                 }
             }
             SlotType.UNKNOWN -> {
-                if (ref.isPost) {
+                if (wantResult && ref.isPost) {
                     val old = allocSlot()
                     builder.emit(Opcode.MOVE_INT, slot, old)
                     builder.emit(if (ref.isIncrement) Opcode.INC_INT else Opcode.DEC_INT, slot)
@@ -814,12 +923,12 @@ class BytecodeCompiler(
         val endLabel = builder.label()
         builder.emit(
             Opcode.JMP_IF_FALSE,
-            listOf(BytecodeBuilder.Operand.IntVal(condition.slot), BytecodeBuilder.Operand.LabelRef(elseLabel))
+            listOf(CmdBuilder.Operand.IntVal(condition.slot), CmdBuilder.Operand.LabelRef(elseLabel))
         )
         val thenValue = compileRefWithFallback(ref.ifTrue, null, Pos.builtIn) ?: return null
         val thenObj = ensureObjSlot(thenValue)
         builder.emit(Opcode.MOVE_OBJ, thenObj.slot, resultSlot)
-        builder.emit(Opcode.JMP, listOf(BytecodeBuilder.Operand.LabelRef(endLabel)))
+        builder.emit(Opcode.JMP, listOf(CmdBuilder.Operand.LabelRef(endLabel)))
         builder.mark(elseLabel)
         val elseValue = compileRefWithFallback(ref.ifFalse, null, Pos.builtIn) ?: return null
         val elseObj = ensureObjSlot(elseValue)
@@ -841,10 +950,10 @@ class BytecodeCompiler(
         val endLabel = builder.label()
         builder.emit(
             Opcode.JMP_IF_TRUE,
-            listOf(BytecodeBuilder.Operand.IntVal(cmpSlot), BytecodeBuilder.Operand.LabelRef(rightLabel))
+            listOf(CmdBuilder.Operand.IntVal(cmpSlot), CmdBuilder.Operand.LabelRef(rightLabel))
         )
         builder.emit(Opcode.MOVE_OBJ, leftObj.slot, resultSlot)
-        builder.emit(Opcode.JMP, listOf(BytecodeBuilder.Operand.LabelRef(endLabel)))
+        builder.emit(Opcode.JMP, listOf(CmdBuilder.Operand.LabelRef(endLabel)))
         builder.mark(rightLabel)
         val rightValue = compileRefWithFallback(ref.right, null, Pos.builtIn) ?: return null
         val rightObj = ensureObjSlot(rightValue)
@@ -941,7 +1050,7 @@ class BytecodeCompiler(
         return 0x8000 or planId
     }
 
-    private fun compileIf(name: String, stmt: IfStatement): BytecodeFunction? {
+    private fun compileIf(name: String, stmt: IfStatement): CmdFunction? {
         val conditionStmt = stmt.condition as? ExpressionStatement ?: return null
         val condValue = compileRefWithFallback(conditionStmt.ref, SlotType.BOOL, stmt.pos) ?: return null
         if (condValue.type != SlotType.BOOL) return null
@@ -952,11 +1061,11 @@ class BytecodeCompiler(
 
         builder.emit(
             Opcode.JMP_IF_FALSE,
-            listOf(BytecodeBuilder.Operand.IntVal(condValue.slot), BytecodeBuilder.Operand.LabelRef(elseLabel))
+            listOf(CmdBuilder.Operand.IntVal(condValue.slot), CmdBuilder.Operand.LabelRef(elseLabel))
         )
         val thenValue = compileStatementValue(stmt.ifBody) ?: return null
         emitMove(thenValue, resultSlot)
-        builder.emit(Opcode.JMP, listOf(BytecodeBuilder.Operand.LabelRef(endLabel)))
+        builder.emit(Opcode.JMP, listOf(CmdBuilder.Operand.LabelRef(endLabel)))
 
         builder.mark(elseLabel)
         if (stmt.elseBody != null) {
@@ -970,28 +1079,68 @@ class BytecodeCompiler(
         builder.mark(endLabel)
         builder.emit(Opcode.RET, resultSlot)
         val localCount = maxOf(nextSlot, resultSlot + 1) - scopeSlotCount
-        return builder.build(name, localCount, scopeSlotDepths, scopeSlotIndices, scopeSlotNames)
+        return builder.build(
+            name,
+            localCount,
+            addrCount = nextAddrSlot,
+            scopeSlotDepths,
+            scopeSlotIndices,
+            scopeSlotNames,
+            localSlotNames,
+            localSlotMutables,
+            localSlotDepths
+        )
     }
 
-    private fun compileForIn(name: String, stmt: net.sergeych.lyng.ForInStatement): BytecodeFunction? {
+    private fun compileForIn(name: String, stmt: net.sergeych.lyng.ForInStatement): CmdFunction? {
-        val resultSlot = emitForIn(stmt) ?: return null
+        val resultSlot = emitForIn(stmt, true) ?: return null
         builder.emit(Opcode.RET, resultSlot)
         val localCount = maxOf(nextSlot, resultSlot + 1) - scopeSlotCount
-        return builder.build(name, localCount, scopeSlotDepths, scopeSlotIndices, scopeSlotNames)
+        return builder.build(
+            name,
+            localCount,
+            addrCount = nextAddrSlot,
+            scopeSlotDepths,
+            scopeSlotIndices,
+            scopeSlotNames,
+            localSlotNames,
+            localSlotMutables,
+            localSlotDepths
+        )
     }
 
-    private fun compileBlock(name: String, stmt: BlockStatement): BytecodeFunction? {
+    private fun compileBlock(name: String, stmt: BlockStatement): CmdFunction? {
-        val result = emitBlock(stmt) ?: return null
+        val result = emitBlock(stmt, true) ?: return null
         builder.emit(Opcode.RET, result.slot)
         val localCount = maxOf(nextSlot, result.slot + 1) - scopeSlotCount
-        return builder.build(name, localCount, scopeSlotDepths, scopeSlotIndices, scopeSlotNames)
+        return builder.build(
+            name,
+            localCount,
+            addrCount = nextAddrSlot,
+            scopeSlotDepths,
+            scopeSlotIndices,
+            scopeSlotNames,
+            localSlotNames,
+            localSlotMutables,
+            localSlotDepths
+        )
     }
 
-    private fun compileVarDecl(name: String, stmt: VarDeclStatement): BytecodeFunction? {
+    private fun compileVarDecl(name: String, stmt: VarDeclStatement): CmdFunction? {
         val result = emitVarDecl(stmt) ?: return null
         builder.emit(Opcode.RET, result.slot)
         val localCount = maxOf(nextSlot, result.slot + 1) - scopeSlotCount
-        return builder.build(name, localCount, scopeSlotDepths, scopeSlotIndices, scopeSlotNames)
+        return builder.build(
+            name,
+            localCount,
+            addrCount = nextAddrSlot,
+            scopeSlotDepths,
+            scopeSlotIndices,
+            scopeSlotNames,
+            localSlotNames,
+            localSlotMutables,
+            localSlotDepths
+        )
     }
 
     private fun compileStatementValue(stmt: Statement): CompiledValue? {
@@ -1001,53 +1150,127 @@ class BytecodeCompiler(
         }
     }
 
-    private fun compileStatementValueOrFallback(stmt: Statement): CompiledValue? {
+    private fun compileStatementValueOrFallback(stmt: Statement, needResult: Boolean = true): CompiledValue? {
         val target = if (stmt is BytecodeStatement) stmt.original else stmt
-        return when (target) {
+        return if (needResult) {
-            is ExpressionStatement -> compileRefWithFallback(target.ref, null, target.pos)
+            when (target) {
-            is IfStatement -> compileIfExpression(target)
+                is ExpressionStatement -> compileRefWithFallback(target.ref, null, target.pos)
-            is net.sergeych.lyng.ForInStatement -> {
+                is IfStatement -> compileIfExpression(target)
-                val resultSlot = emitForIn(target) ?: return null
+                is net.sergeych.lyng.ForInStatement -> {
-                updateSlotType(resultSlot, SlotType.OBJ)
+                    val resultSlot = emitForIn(target, true) ?: return null
-                CompiledValue(resultSlot, SlotType.OBJ)
+                    updateSlotType(resultSlot, SlotType.OBJ)
+                    CompiledValue(resultSlot, SlotType.OBJ)
+                }
+                is BlockStatement -> emitBlock(target, true)
+                is VarDeclStatement -> emitVarDecl(target)
+                else -> {
+                    val slot = allocSlot()
+                    val id = builder.addFallback(target)
+                    builder.emit(Opcode.EVAL_FALLBACK, id, slot)
+                    builder.emit(Opcode.BOX_OBJ, slot, slot)
+                    updateSlotType(slot, SlotType.OBJ)
+                    CompiledValue(slot, SlotType.OBJ)
+                }
             }
-            is BlockStatement -> emitBlock(target)
+        } else {
-            is VarDeclStatement -> emitVarDecl(target)
+            when (target) {
-            else -> {
+                is ExpressionStatement -> {
-                val slot = allocSlot()
+                    val ref = target.ref
-                val id = builder.addFallback(target)
+                    if (ref is IncDecRef) {
-                builder.emit(Opcode.EVAL_FALLBACK, id, slot)
+                        compileIncDec(ref, false)
-                builder.emit(Opcode.BOX_OBJ, slot, slot)
+                    } else {
-                updateSlotType(slot, SlotType.OBJ)
+                        compileRefWithFallback(ref, null, target.pos)
-                CompiledValue(slot, SlotType.OBJ)
+                    }
+                }
+                is IfStatement -> compileIfStatement(target)
+                is net.sergeych.lyng.ForInStatement -> {
+                    val resultSlot = emitForIn(target, false) ?: return null
+                    CompiledValue(resultSlot, SlotType.OBJ)
+                }
+                is BlockStatement -> emitBlock(target, false)
+                is VarDeclStatement -> emitVarDecl(target)
+                else -> {
+                    val slot = allocSlot()
+                    val id = builder.addFallback(target)
+                    builder.emit(Opcode.EVAL_FALLBACK, id, slot)
+                    builder.emit(Opcode.BOX_OBJ, slot, slot)
+                    updateSlotType(slot, SlotType.OBJ)
+                    CompiledValue(slot, SlotType.OBJ)
+                }
             }
         }
     }
 
-    private fun emitBlock(stmt: BlockStatement): CompiledValue? {
+    private fun emitBlock(stmt: BlockStatement, needResult: Boolean): CompiledValue? {
         val planId = builder.addConst(BytecodeConst.SlotPlan(stmt.slotPlan))
         builder.emit(Opcode.PUSH_SCOPE, planId)
+        resetAddrCache()
         val statements = stmt.statements()
         var lastValue: CompiledValue? = null
-        for (statement in statements) {
+        for ((index, statement) in statements.withIndex()) {
-            lastValue = compileStatementValueOrFallback(statement) ?: return null
+            val isLast = index == statements.lastIndex
+            val wantResult = needResult && isLast
+            val value = compileStatementValueOrFallback(statement, wantResult) ?: return null
+            if (wantResult) {
+                lastValue = value
+            }
         }
-        var result = lastValue ?: run {
+        val result = if (needResult) {
-            val slot = allocSlot()
+            var value = lastValue ?: run {
-            val voidId = builder.addConst(BytecodeConst.ObjRef(ObjVoid))
+                val slot = allocSlot()
-            builder.emit(Opcode.CONST_OBJ, voidId, slot)
+                val voidId = builder.addConst(BytecodeConst.ObjRef(ObjVoid))
-            CompiledValue(slot, SlotType.OBJ)
+                builder.emit(Opcode.CONST_OBJ, voidId, slot)
-        }
+                CompiledValue(slot, SlotType.OBJ)
-        if (result.slot < scopeSlotCount) {
+            }
-            val captured = allocSlot()
+            if (value.slot < scopeSlotCount) {
-            emitMove(result, captured)
+                val captured = allocSlot()
-            result = CompiledValue(captured, result.type)
+                emitMove(value, captured)
+                value = CompiledValue(captured, value.type)
+            }
+            value
+        } else {
+            lastValue ?: run {
+                val slot = allocSlot()
+                val voidId = builder.addConst(BytecodeConst.ObjRef(ObjVoid))
+                builder.emit(Opcode.CONST_OBJ, voidId, slot)
+                CompiledValue(slot, SlotType.OBJ)
+            }
         }
         builder.emit(Opcode.POP_SCOPE)
+        resetAddrCache()
         return result
     }
 
     private fun emitVarDecl(stmt: VarDeclStatement): CompiledValue? {
+        val localSlot = if (allowLocalSlots && stmt.slotIndex != null) {
+            val depth = stmt.slotDepth ?: 0
+            val key = ScopeSlotKey(depth, stmt.slotIndex)
+            val localIndex = localSlotIndexByKey[key]
+            localIndex?.let { scopeSlotCount + it }
+        } else {
+            null
+        }
+        if (localSlot != null) {
+            val value = stmt.initializer?.let { compileStatementValueOrFallback(it) } ?: run {
+                builder.emit(Opcode.CONST_NULL, localSlot)
+                updateSlotType(localSlot, SlotType.OBJ)
+                CompiledValue(localSlot, SlotType.OBJ)
+            }
+            if (value.slot != localSlot) {
+                emitMove(value, localSlot)
+            }
+            updateSlotType(localSlot, value.type)
+            val declId = builder.addConst(
+                BytecodeConst.LocalDecl(
+                    stmt.name,
+                    stmt.isMutable,
+                    stmt.visibility,
+                    stmt.isTransient
+                )
+            )
+            builder.emit(Opcode.DECL_LOCAL, declId, localSlot)
+            return CompiledValue(localSlot, value.type)
+        }
         val value = stmt.initializer?.let { compileStatementValueOrFallback(it) } ?: run {
             val slot = allocSlot()
             builder.emit(Opcode.CONST_NULL, slot)
@@ -1068,18 +1291,11 @@ class BytecodeCompiler(
         }
         return value
     }
-    private fun emitForIn(stmt: net.sergeych.lyng.ForInStatement): Int? {
+    private fun emitForIn(stmt: net.sergeych.lyng.ForInStatement, wantResult: Boolean): Int? {
         if (stmt.canBreak) return null
         val range = stmt.constRange ?: return null
-        val loopSlotId = loopVarSlotIdByName[stmt.loopVarName] ?: return null
+        val loopLocalIndex = localSlotIndexByName[stmt.loopVarName] ?: return null
-        val slotIndex = loopVarSlotIndexByName[stmt.loopVarName] ?: return null
+        val loopSlotId = scopeSlotCount + loopLocalIndex
-        val planId = builder.addConst(BytecodeConst.SlotPlan(mapOf(stmt.loopVarName to slotIndex)))
-        val useLoopScope = scopeSlotMap.isEmpty()
-        if (useLoopScope) {
-            builder.emit(Opcode.PUSH_SCOPE, planId)
-        } else {
-            builder.emit(Opcode.PUSH_SLOT_PLAN, planId)
-        }
 
         val iSlot = allocSlot()
         val endSlot = allocSlot()
@@ -1089,8 +1305,10 @@ class BytecodeCompiler(
         builder.emit(Opcode.CONST_INT, endId, endSlot)
 
         val resultSlot = allocSlot()
-        val voidId = builder.addConst(BytecodeConst.ObjRef(ObjVoid))
+        if (wantResult) {
-        builder.emit(Opcode.CONST_OBJ, voidId, resultSlot)
+            val voidId = builder.addConst(BytecodeConst.ObjRef(ObjVoid))
+            builder.emit(Opcode.CONST_OBJ, voidId, resultSlot)
+        }
 
         val loopLabel = builder.label()
         val endLabel = builder.label()
@@ -1099,35 +1317,53 @@ class BytecodeCompiler(
         builder.emit(Opcode.CMP_GTE_INT, iSlot, endSlot, cmpSlot)
         builder.emit(
             Opcode.JMP_IF_TRUE,
-            listOf(BytecodeBuilder.Operand.IntVal(cmpSlot), BytecodeBuilder.Operand.LabelRef(endLabel))
+            listOf(CmdBuilder.Operand.IntVal(cmpSlot), CmdBuilder.Operand.LabelRef(endLabel))
         )
         builder.emit(Opcode.MOVE_INT, iSlot, loopSlotId)
         updateSlotType(loopSlotId, SlotType.INT)
         updateSlotTypeByName(stmt.loopVarName, SlotType.INT)
-        val bodyValue = compileStatementValueOrFallback(stmt.body) ?: return null
+        val bodyValue = compileStatementValueOrFallback(stmt.body, wantResult) ?: return null
-        val bodyObj = ensureObjSlot(bodyValue)
+        if (wantResult) {
-        builder.emit(Opcode.MOVE_OBJ, bodyObj.slot, resultSlot)
+            val bodyObj = ensureObjSlot(bodyValue)
+            builder.emit(Opcode.MOVE_OBJ, bodyObj.slot, resultSlot)
+        }
         builder.emit(Opcode.INC_INT, iSlot)
-        builder.emit(Opcode.JMP, listOf(BytecodeBuilder.Operand.LabelRef(loopLabel)))
+        builder.emit(Opcode.JMP, listOf(CmdBuilder.Operand.LabelRef(loopLabel)))
 
         builder.mark(endLabel)
         if (stmt.elseStatement != null) {
-            val elseValue = compileStatementValueOrFallback(stmt.elseStatement) ?: return null
+            val elseValue = compileStatementValueOrFallback(stmt.elseStatement, wantResult) ?: return null
-            val elseObj = ensureObjSlot(elseValue)
+            if (wantResult) {
-            builder.emit(Opcode.MOVE_OBJ, elseObj.slot, resultSlot)
+                val elseObj = ensureObjSlot(elseValue)
-        }
+                builder.emit(Opcode.MOVE_OBJ, elseObj.slot, resultSlot)
-        if (useLoopScope) {
+            }
-            builder.emit(Opcode.POP_SCOPE)
-        } else {
-            builder.emit(Opcode.POP_SLOT_PLAN)
         }
         return resultSlot
     }
 
+    private fun compileIfStatement(stmt: IfStatement): CompiledValue? {
+        val condition = compileCondition(stmt.condition, stmt.pos) ?: return null
+        if (condition.type != SlotType.BOOL) return null
+        val elseLabel = builder.label()
+        val endLabel = builder.label()
+        builder.emit(
+            Opcode.JMP_IF_FALSE,
+            listOf(CmdBuilder.Operand.IntVal(condition.slot), CmdBuilder.Operand.LabelRef(elseLabel))
+        )
+        compileStatementValueOrFallback(stmt.ifBody, false) ?: return null
+        builder.emit(Opcode.JMP, listOf(CmdBuilder.Operand.LabelRef(endLabel)))
+        builder.mark(elseLabel)
+        stmt.elseBody?.let {
+            compileStatementValueOrFallback(it, false) ?: return null
+        }
+        builder.mark(endLabel)
+        return condition
+    }
+
     private fun updateSlotTypeByName(name: String, type: SlotType) {
-        val loopSlotId = loopVarSlotIdByName[name]
+        val localIndex = localSlotIndexByName[name]
-        if (loopSlotId != null) {
+        if (localIndex != null) {
-            updateSlotType(loopSlotId, type)
+            updateSlotType(scopeSlotCount + localIndex, type)
             return
         }
         for ((key, index) in scopeSlotMap) {
@@ -1145,12 +1381,12 @@ class BytecodeCompiler(
         val endLabel = builder.label()
         builder.emit(
             Opcode.JMP_IF_FALSE,
-            listOf(BytecodeBuilder.Operand.IntVal(condition.slot), BytecodeBuilder.Operand.LabelRef(elseLabel))
+            listOf(CmdBuilder.Operand.IntVal(condition.slot), CmdBuilder.Operand.LabelRef(elseLabel))
         )
         val thenValue = compileStatementValueOrFallback(stmt.ifBody) ?: return null
         val thenObj = ensureObjSlot(thenValue)
         builder.emit(Opcode.MOVE_OBJ, thenObj.slot, resultSlot)
-        builder.emit(Opcode.JMP, listOf(BytecodeBuilder.Operand.LabelRef(endLabel)))
+        builder.emit(Opcode.JMP, listOf(CmdBuilder.Operand.LabelRef(endLabel)))
         builder.mark(elseLabel)
         if (stmt.elseBody != null) {
             val elseValue = compileStatementValueOrFallback(stmt.elseBody) ?: return null
@@ -1178,12 +1414,60 @@ class BytecodeCompiler(
         }
     }
 
+    private fun resetAddrCache() {
+        addrSlotByScopeSlot.clear()
+    }
+
+    private fun ensureScopeAddr(scopeSlot: Int): Int {
+        val existing = addrSlotByScopeSlot[scopeSlot]
+        if (existing != null) return existing
+        val addrSlot = nextAddrSlot++
+        addrSlotByScopeSlot[scopeSlot] = addrSlot
+        builder.emit(Opcode.RESOLVE_SCOPE_SLOT, scopeSlot, addrSlot)
+        return addrSlot
+    }
+
+    private fun emitLoadFromAddr(addrSlot: Int, dstSlot: Int, type: SlotType) {
+        when (type) {
+            SlotType.INT -> builder.emit(Opcode.LOAD_INT_ADDR, addrSlot, dstSlot)
+            SlotType.REAL -> builder.emit(Opcode.LOAD_REAL_ADDR, addrSlot, dstSlot)
+            SlotType.BOOL -> builder.emit(Opcode.LOAD_BOOL_ADDR, addrSlot, dstSlot)
+            SlotType.OBJ -> builder.emit(Opcode.LOAD_OBJ_ADDR, addrSlot, dstSlot)
+            else -> builder.emit(Opcode.LOAD_OBJ_ADDR, addrSlot, dstSlot)
+        }
+    }
+
+    private fun emitStoreToAddr(srcSlot: Int, addrSlot: Int, type: SlotType) {
+        when (type) {
+            SlotType.INT -> builder.emit(Opcode.STORE_INT_ADDR, srcSlot, addrSlot)
+            SlotType.REAL -> builder.emit(Opcode.STORE_REAL_ADDR, srcSlot, addrSlot)
+            SlotType.BOOL -> builder.emit(Opcode.STORE_BOOL_ADDR, srcSlot, addrSlot)
+            SlotType.OBJ -> builder.emit(Opcode.STORE_OBJ_ADDR, srcSlot, addrSlot)
+            else -> builder.emit(Opcode.STORE_OBJ_ADDR, srcSlot, addrSlot)
+        }
+    }
+
     private fun emitMove(value: CompiledValue, dstSlot: Int) {
+        val srcSlot = value.slot
+        val srcIsScope = srcSlot < scopeSlotCount
+        val dstIsScope = dstSlot < scopeSlotCount
+        if (value.type != SlotType.UNKNOWN) {
+            if (srcIsScope && !dstIsScope) {
+                val addrSlot = ensureScopeAddr(srcSlot)
+                emitLoadFromAddr(addrSlot, dstSlot, value.type)
+                return
+            }
+            if (dstIsScope) {
+                val addrSlot = ensureScopeAddr(dstSlot)
+                emitStoreToAddr(srcSlot, addrSlot, value.type)
+                return
+            }
+        }
         when (value.type) {
-            SlotType.INT -> builder.emit(Opcode.MOVE_INT, value.slot, dstSlot)
+            SlotType.INT -> builder.emit(Opcode.MOVE_INT, srcSlot, dstSlot)
-            SlotType.REAL -> builder.emit(Opcode.MOVE_REAL, value.slot, dstSlot)
+            SlotType.REAL -> builder.emit(Opcode.MOVE_REAL, srcSlot, dstSlot)
-            SlotType.BOOL -> builder.emit(Opcode.MOVE_BOOL, value.slot, dstSlot)
+            SlotType.BOOL -> builder.emit(Opcode.MOVE_BOOL, srcSlot, dstSlot)
-            else -> builder.emit(Opcode.MOVE_OBJ, value.slot, dstSlot)
+            else -> builder.emit(Opcode.MOVE_OBJ, srcSlot, dstSlot)
         }
     }
 
@@ -1215,6 +1499,7 @@ class BytecodeCompiler(
 
     private fun refSlot(ref: LocalSlotRef): Int = ref.slot
     private fun refDepth(ref: LocalSlotRef): Int = ref.depth
+    private fun refScopeDepth(ref: LocalSlotRef): Int = ref.scopeDepth
     private fun binaryLeft(ref: BinaryOpRef): ObjRef = ref.left
     private fun binaryRight(ref: BinaryOpRef): ObjRef = ref.right
     private fun binaryOp(ref: BinaryOpRef): BinOp = ref.op
@@ -1224,6 +1509,16 @@ class BytecodeCompiler(
     private fun assignValue(ref: AssignRef): ObjRef = ref.value
     private fun refPos(ref: BinaryOpRef): Pos = Pos.builtIn
 
+    private fun resolveSlot(ref: LocalSlotRef): Int? {
+        val localKey = ScopeSlotKey(refScopeDepth(ref), refSlot(ref))
+        val localIndex = localSlotIndexByKey[localKey]
+        if (localIndex != null) return scopeSlotCount + localIndex
+        val nameIndex = localSlotIndexByName[ref.name]
+        if (nameIndex != null) return scopeSlotCount + nameIndex
+        val scopeKey = ScopeSlotKey(refDepth(ref), refSlot(ref))
+        return scopeSlotMap[scopeKey]
+    }
+
     private fun updateSlotType(slot: Int, type: SlotType) {
         if (type == SlotType.UNKNOWN) {
             slotTypes.remove(slot)
@@ -1233,17 +1528,24 @@ class BytecodeCompiler(
     }
 
     private fun prepareCompilation(stmt: Statement) {
-        builder = BytecodeBuilder()
+        builder = CmdBuilder()
         nextSlot = 0
+        nextAddrSlot = 0
         slotTypes.clear()
         scopeSlotMap.clear()
+        localSlotInfoMap.clear()
+        localSlotIndexByKey.clear()
+        localSlotIndexByName.clear()
+        localSlotNames = emptyArray()
+        localSlotMutables = BooleanArray(0)
+        localSlotDepths = IntArray(0)
+        declaredLocalKeys.clear()
         intLoopVarNames.clear()
-        loopVarNames.clear()
+        addrSlotByScopeSlot.clear()
-        loopVarSlotIndexByName.clear()
-        loopVarSlotIdByName.clear()
         if (allowLocalSlots) {
             collectLoopVarNames(stmt)
             collectScopeSlots(stmt)
+            collectLoopSlotPlans(stmt, 0)
         }
         scopeSlotCount = scopeSlotMap.size
         scopeSlotDepths = IntArray(scopeSlotCount)
@@ -1255,28 +1557,26 @@ class BytecodeCompiler(
             scopeSlotIndices[index] = key.slot
             scopeSlotNames[index] = name
         }
-        if (loopVarNames.isNotEmpty()) {
+        if (allowLocalSlots && localSlotInfoMap.isNotEmpty()) {
-            var maxSlotIndex = scopeSlotMap.keys.maxOfOrNull { it.slot } ?: -1
+            val names = ArrayList<String?>(localSlotInfoMap.size)
-            for (name in loopVarNames) {
+            val mutables = BooleanArray(localSlotInfoMap.size)
-                maxSlotIndex += 1
+            val depths = IntArray(localSlotInfoMap.size)
-                loopVarSlotIndexByName[name] = maxSlotIndex
+            var index = 0
+            for ((key, info) in localSlotInfoMap) {
+                localSlotIndexByKey[key] = index
+                if (!localSlotIndexByName.containsKey(info.name)) {
+                    localSlotIndexByName[info.name] = index
+                }
+                names.add(info.name)
+                mutables[index] = info.isMutable
+                depths[index] = info.depth
+                index += 1
             }
-            val start = scopeSlotCount
+            localSlotNames = names.toTypedArray()
-            val total = scopeSlotCount + loopVarSlotIndexByName.size
+            localSlotMutables = mutables
-            scopeSlotDepths = scopeSlotDepths.copyOf(total)
+            localSlotDepths = depths
-            scopeSlotIndices = scopeSlotIndices.copyOf(total)
-            scopeSlotNames = scopeSlotNames.copyOf(total)
-            var cursor = start
-            for ((name, slotIndex) in loopVarSlotIndexByName) {
-                loopVarSlotIdByName[name] = cursor
-                scopeSlotDepths[cursor] = 0
-                scopeSlotIndices[cursor] = slotIndex
-                scopeSlotNames[cursor] = name
-                cursor += 1
-            }
-            scopeSlotCount = total
         }
-        nextSlot = scopeSlotCount
+        nextSlot = scopeSlotCount + localSlotNames.size
     }
 
     private fun collectScopeSlots(stmt: Statement) {
@@ -1292,6 +1592,11 @@ class BytecodeCompiler(
                 }
             }
             is VarDeclStatement -> {
+                val slotIndex = stmt.slotIndex
+                val slotDepth = stmt.slotDepth
+                if (allowLocalSlots && slotIndex != null && slotDepth != null) {
+                    declaredLocalKeys.add(ScopeSlotKey(slotDepth, slotIndex))
+                }
                 stmt.initializer?.let { collectScopeSlots(it) }
             }
             is IfStatement -> {
@@ -1308,6 +1613,45 @@ class BytecodeCompiler(
         }
     }
 
+    private fun collectLoopSlotPlans(stmt: Statement, scopeDepth: Int) {
+        if (stmt is BytecodeStatement) {
+            collectLoopSlotPlans(stmt.original, scopeDepth)
+            return
+        }
+        when (stmt) {
+            is net.sergeych.lyng.ForInStatement -> {
+                collectLoopSlotPlans(stmt.source, scopeDepth)
+                val loopDepth = scopeDepth + 1
+                for ((name, slotIndex) in stmt.loopSlotPlan) {
+                    val key = ScopeSlotKey(loopDepth, slotIndex)
+                    if (!localSlotInfoMap.containsKey(key)) {
+                        localSlotInfoMap[key] = LocalSlotInfo(name, isMutable = true, depth = loopDepth)
+                    }
+                }
+                collectLoopSlotPlans(stmt.body, loopDepth)
+                stmt.elseStatement?.let { collectLoopSlotPlans(it, loopDepth) }
+            }
+            is BlockStatement -> {
+                val nextDepth = scopeDepth + 1
+                for (child in stmt.statements()) {
+                    collectLoopSlotPlans(child, nextDepth)
+                }
+            }
+            is IfStatement -> {
+                collectLoopSlotPlans(stmt.condition, scopeDepth)
+                collectLoopSlotPlans(stmt.ifBody, scopeDepth)
+                stmt.elseBody?.let { collectLoopSlotPlans(it, scopeDepth) }
+            }
+            is VarDeclStatement -> {
+                stmt.initializer?.let { collectLoopSlotPlans(it, scopeDepth) }
+            }
+            is ExpressionStatement -> {
+                // no-op
+            }
+            else -> {}
+        }
+    }
+
     private fun collectLoopVarNames(stmt: Statement) {
         if (stmt is BytecodeStatement) {
             collectLoopVarNames(stmt.original)
@@ -1317,7 +1661,6 @@ class BytecodeCompiler(
             is net.sergeych.lyng.ForInStatement -> {
                 if (stmt.constRange != null) {
                     intLoopVarNames.add(stmt.loopVarName)
-                    loopVarNames.add(stmt.loopVarName)
                 }
                 collectLoopVarNames(stmt.source)
                 collectLoopVarNames(stmt.body)
@@ -1370,7 +1713,15 @@ class BytecodeCompiler(
     private fun collectScopeSlotsRef(ref: ObjRef) {
         when (ref) {
             is LocalSlotRef -> {
-                if (loopVarNames.contains(ref.name)) return
+                val localKey = ScopeSlotKey(refScopeDepth(ref), refSlot(ref))
+                val shouldLocalize = declaredLocalKeys.contains(localKey) ||
+                    intLoopVarNames.contains(ref.name)
+                if (allowLocalSlots && !ref.isDelegated && shouldLocalize) {
+                    if (!localSlotInfoMap.containsKey(localKey)) {
+                        localSlotInfoMap[localKey] = LocalSlotInfo(ref.name, ref.isMutable, localKey.depth)
+                    }
+                    return
+                }
                 val key = ScopeSlotKey(refDepth(ref), refSlot(ref))
                 if (!scopeSlotMap.containsKey(key)) {
                     scopeSlotMap[key] = scopeSlotMap.size
@@ -1387,12 +1738,21 @@ class BytecodeCompiler(
             is AssignRef -> {
                 val target = assignTarget(ref)
                 if (target != null) {
-                    val key = ScopeSlotKey(refDepth(target), refSlot(target))
+                    val localKey = ScopeSlotKey(refScopeDepth(target), refSlot(target))
-                    if (!scopeSlotMap.containsKey(key)) {
+                    val shouldLocalize = declaredLocalKeys.contains(localKey) ||
-                        scopeSlotMap[key] = scopeSlotMap.size
+                        intLoopVarNames.contains(target.name)
-                    }
+                    if (allowLocalSlots && !target.isDelegated && shouldLocalize) {
-                    if (!scopeSlotNameMap.containsKey(key)) {
+                        if (!localSlotInfoMap.containsKey(localKey)) {
-                        scopeSlotNameMap[key] = target.name
+                            localSlotInfoMap[localKey] = LocalSlotInfo(target.name, target.isMutable, localKey.depth)
+                        }
+                    } else {
+                        val key = ScopeSlotKey(refDepth(target), refSlot(target))
+                        if (!scopeSlotMap.containsKey(key)) {
+                            scopeSlotMap[key] = scopeSlotMap.size
+                        }
+                        if (!scopeSlotNameMap.containsKey(key)) {
+                            scopeSlotNameMap[key] = target.name
+                        }
                     }
                 }
                 collectScopeSlotsRef(assignValue(ref))

lynglib/src/commonMain/kotlin/net/sergeych/lyng/bytecode/BytecodeDecoder.kt

@@ -1,77 +0,0 @@
-/*
- * Copyright 2026 Sergey S. Chernov
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package net.sergeych.lyng.bytecode
-
-interface BytecodeDecoder {
-    fun readOpcode(code: ByteArray, ip: Int): Opcode
-    fun readSlot(code: ByteArray, ip: Int): Int
-    fun readConstId(code: ByteArray, ip: Int, width: Int): Int
-    fun readIp(code: ByteArray, ip: Int, width: Int): Int
-}
-
-object Decoder8 : BytecodeDecoder {
-    override fun readOpcode(code: ByteArray, ip: Int): Opcode =
-        Opcode.fromCode(code[ip].toInt() and 0xFF) ?: error("Unknown opcode: ${code[ip]}")
-
-    override fun readSlot(code: ByteArray, ip: Int): Int = code[ip].toInt() and 0xFF
-
-    override fun readConstId(code: ByteArray, ip: Int, width: Int): Int =
-        readUInt(code, ip, width)
-
-    override fun readIp(code: ByteArray, ip: Int, width: Int): Int =
-        readUInt(code, ip, width)
-}
-
-object Decoder16 : BytecodeDecoder {
-    override fun readOpcode(code: ByteArray, ip: Int): Opcode =
-        Opcode.fromCode(code[ip].toInt() and 0xFF) ?: error("Unknown opcode: ${code[ip]}")
-
-    override fun readSlot(code: ByteArray, ip: Int): Int =
-        (code[ip].toInt() and 0xFF) or ((code[ip + 1].toInt() and 0xFF) shl 8)
-
-    override fun readConstId(code: ByteArray, ip: Int, width: Int): Int =
-        readUInt(code, ip, width)
-
-    override fun readIp(code: ByteArray, ip: Int, width: Int): Int =
-        readUInt(code, ip, width)
-}
-
-object Decoder32 : BytecodeDecoder {
-    override fun readOpcode(code: ByteArray, ip: Int): Opcode =
-        Opcode.fromCode(code[ip].toInt() and 0xFF) ?: error("Unknown opcode: ${code[ip]}")
-
-    override fun readSlot(code: ByteArray, ip: Int): Int = readUInt(code, ip, 4)
-
-    override fun readConstId(code: ByteArray, ip: Int, width: Int): Int =
-        readUInt(code, ip, width)
-
-    override fun readIp(code: ByteArray, ip: Int, width: Int): Int =
-        readUInt(code, ip, width)
-}
-
-private fun readUInt(code: ByteArray, ip: Int, width: Int): Int {
-    var result = 0
-    var shift = 0
-    var idx = ip
-    var remaining = width
-    while (remaining-- > 0) {
-        result = result or ((code[idx].toInt() and 0xFF) shl shift)
-        shift += 8
-        idx++
-    }
-    return result
-}

lynglib/src/commonMain/kotlin/net/sergeych/lyng/bytecode/BytecodeDisassembler.kt

@@ -1,138 +0,0 @@
-/*
- * Copyright 2026 Sergey S. Chernov
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package net.sergeych.lyng.bytecode
-
-object BytecodeDisassembler {
-    fun disassemble(fn: BytecodeFunction): String {
-        val decoder = when (fn.slotWidth) {
-            1 -> Decoder8
-            2 -> Decoder16
-            4 -> Decoder32
-            else -> error("Unsupported slot width: ${fn.slotWidth}")
-        }
-        val out = StringBuilder()
-        val code = fn.code
-        var ip = 0
-        while (ip < code.size) {
-            val op = decoder.readOpcode(code, ip)
-            val startIp = ip
-            ip += 1
-            val kinds = operandKinds(op)
-            val operands = ArrayList<String>(kinds.size)
-            for (kind in kinds) {
-                when (kind) {
-                    OperandKind.SLOT -> {
-                        val v = decoder.readSlot(code, ip)
-                        ip += fn.slotWidth
-                        val name = if (v < fn.scopeSlotCount) fn.scopeSlotNames[v] else null
-                        operands += if (name != null) "s$v($name)" else "s$v"
-                    }
-                    OperandKind.CONST -> {
-                        val v = decoder.readConstId(code, ip, fn.constIdWidth)
-                        ip += fn.constIdWidth
-                        operands += "k$v"
-                    }
-                    OperandKind.IP -> {
-                        val v = decoder.readIp(code, ip, fn.ipWidth)
-                        ip += fn.ipWidth
-                        operands += "ip$v"
-                    }
-                    OperandKind.COUNT -> {
-                        val v = decoder.readConstId(code, ip, 2)
-                        ip += 2
-                        operands += "n$v"
-                    }
-                    OperandKind.ID -> {
-                        val v = decoder.readConstId(code, ip, 2)
-                        ip += 2
-                        operands += "#$v"
-                    }
-                }
-            }
-            out.append(startIp).append(": ").append(op.name)
-            if (operands.isNotEmpty()) {
-                out.append(' ').append(operands.joinToString(", "))
-            }
-            out.append('\n')
-        }
-        return out.toString()
-    }
-
-    private enum class OperandKind {
-        SLOT,
-        CONST,
-        IP,
-        COUNT,
-        ID,
-    }
-
-    private fun operandKinds(op: Opcode): List<OperandKind> {
-        return when (op) {
-            Opcode.NOP, Opcode.RET_VOID, Opcode.POP_SCOPE, Opcode.POP_SLOT_PLAN -> emptyList()
-            Opcode.MOVE_OBJ, Opcode.MOVE_INT, Opcode.MOVE_REAL, Opcode.MOVE_BOOL, Opcode.BOX_OBJ,
-            Opcode.INT_TO_REAL, Opcode.REAL_TO_INT, Opcode.BOOL_TO_INT, Opcode.INT_TO_BOOL,
-            Opcode.NEG_INT, Opcode.NEG_REAL, Opcode.NOT_BOOL, Opcode.INV_INT ->
-                listOf(OperandKind.SLOT, OperandKind.SLOT)
-            Opcode.CONST_NULL ->
-                listOf(OperandKind.SLOT)
-            Opcode.CONST_OBJ, Opcode.CONST_INT, Opcode.CONST_REAL, Opcode.CONST_BOOL ->
-                listOf(OperandKind.CONST, OperandKind.SLOT)
-            Opcode.PUSH_SCOPE, Opcode.PUSH_SLOT_PLAN ->
-                listOf(OperandKind.CONST)
-            Opcode.DECL_LOCAL ->
-                listOf(OperandKind.CONST, OperandKind.SLOT)
-            Opcode.ADD_INT, Opcode.SUB_INT, Opcode.MUL_INT, Opcode.DIV_INT, Opcode.MOD_INT,
-            Opcode.ADD_REAL, Opcode.SUB_REAL, Opcode.MUL_REAL, Opcode.DIV_REAL,
-            Opcode.AND_INT, Opcode.OR_INT, Opcode.XOR_INT, Opcode.SHL_INT, Opcode.SHR_INT, Opcode.USHR_INT,
-            Opcode.CMP_EQ_INT, Opcode.CMP_NEQ_INT, Opcode.CMP_LT_INT, Opcode.CMP_LTE_INT,
-            Opcode.CMP_GT_INT, Opcode.CMP_GTE_INT,
-            Opcode.CMP_EQ_REAL, Opcode.CMP_NEQ_REAL, Opcode.CMP_LT_REAL, Opcode.CMP_LTE_REAL,
-            Opcode.CMP_GT_REAL, Opcode.CMP_GTE_REAL,
-            Opcode.CMP_EQ_BOOL, Opcode.CMP_NEQ_BOOL,
-            Opcode.CMP_EQ_INT_REAL, Opcode.CMP_EQ_REAL_INT, Opcode.CMP_LT_INT_REAL, Opcode.CMP_LT_REAL_INT,
-            Opcode.CMP_LTE_INT_REAL, Opcode.CMP_LTE_REAL_INT, Opcode.CMP_GT_INT_REAL, Opcode.CMP_GT_REAL_INT,
-            Opcode.CMP_GTE_INT_REAL, Opcode.CMP_GTE_REAL_INT, Opcode.CMP_NEQ_INT_REAL, Opcode.CMP_NEQ_REAL_INT,
-            Opcode.CMP_EQ_OBJ, Opcode.CMP_NEQ_OBJ, Opcode.CMP_REF_EQ_OBJ, Opcode.CMP_REF_NEQ_OBJ,
-            Opcode.CMP_LT_OBJ, Opcode.CMP_LTE_OBJ, Opcode.CMP_GT_OBJ, Opcode.CMP_GTE_OBJ,
-            Opcode.ADD_OBJ, Opcode.SUB_OBJ, Opcode.MUL_OBJ, Opcode.DIV_OBJ, Opcode.MOD_OBJ,
-            Opcode.AND_BOOL, Opcode.OR_BOOL ->
-                listOf(OperandKind.SLOT, OperandKind.SLOT, OperandKind.SLOT)
-            Opcode.INC_INT, Opcode.DEC_INT, Opcode.RET ->
-                listOf(OperandKind.SLOT)
-            Opcode.JMP ->
-                listOf(OperandKind.IP)
-            Opcode.JMP_IF_TRUE, Opcode.JMP_IF_FALSE ->
-                listOf(OperandKind.SLOT, OperandKind.IP)
-            Opcode.CALL_DIRECT, Opcode.CALL_FALLBACK ->
-                listOf(OperandKind.ID, OperandKind.SLOT, OperandKind.COUNT, OperandKind.SLOT)
-            Opcode.CALL_SLOT ->
-                listOf(OperandKind.SLOT, OperandKind.SLOT, OperandKind.COUNT, OperandKind.SLOT)
-            Opcode.CALL_VIRTUAL ->
-                listOf(OperandKind.SLOT, OperandKind.ID, OperandKind.SLOT, OperandKind.COUNT, OperandKind.SLOT)
-            Opcode.GET_FIELD ->
-                listOf(OperandKind.SLOT, OperandKind.ID, OperandKind.SLOT)
-            Opcode.SET_FIELD ->
-                listOf(OperandKind.SLOT, OperandKind.ID, OperandKind.SLOT)
-            Opcode.GET_INDEX ->
-                listOf(OperandKind.SLOT, OperandKind.SLOT, OperandKind.SLOT)
-            Opcode.SET_INDEX ->
-                listOf(OperandKind.SLOT, OperandKind.SLOT, OperandKind.SLOT)
-            Opcode.EVAL_FALLBACK ->
-                listOf(OperandKind.ID, OperandKind.SLOT)
-        }
-    }
-}

lynglib/src/commonMain/kotlin/net/sergeych/lyng/bytecode/BytecodeStatement.kt

@@ -23,30 +23,111 @@ import net.sergeych.lyng.obj.Obj
 
 class BytecodeStatement private constructor(
     val original: Statement,
-    private val function: BytecodeFunction,
+    private val function: CmdFunction,
 ) : Statement(original.isStaticConst, original.isConst, original.returnType) {
     override val pos: Pos = original.pos
 
     override suspend fun execute(scope: Scope): Obj {
-        return BytecodeVm().execute(function, scope, emptyList())
+        return CmdVm().execute(function, scope, emptyList())
     }
 
-    internal fun bytecodeFunction(): BytecodeFunction = function
+    internal fun bytecodeFunction(): CmdFunction = function
 
     companion object {
         fun wrap(statement: Statement, nameHint: String, allowLocalSlots: Boolean): Statement {
             if (statement is BytecodeStatement) return statement
-            val compiler = BytecodeCompiler(allowLocalSlots = allowLocalSlots)
+            val hasUnsupported = containsUnsupportedStatement(statement)
+            if (hasUnsupported) return unwrapDeep(statement)
+            val safeLocals = allowLocalSlots
+            val compiler = BytecodeCompiler(allowLocalSlots = safeLocals)
             val compiled = compiler.compileStatement(nameHint, statement)
             val fn = compiled ?: run {
-                val builder = BytecodeBuilder()
+                val builder = CmdBuilder()
                 val slot = 0
                 val id = builder.addFallback(statement)
                 builder.emit(Opcode.EVAL_FALLBACK, id, slot)
                 builder.emit(Opcode.RET, slot)
-                builder.build(nameHint, localCount = 1)
+                builder.build(
+                    nameHint,
+                    localCount = 1,
+                    addrCount = 0,
+                    localSlotNames = emptyArray(),
+                    localSlotMutables = BooleanArray(0),
+                    localSlotDepths = IntArray(0)
+                )
             }
             return BytecodeStatement(statement, fn)
         }
+
+        private fun containsUnsupportedStatement(stmt: Statement): Boolean {
+            val target = if (stmt is BytecodeStatement) stmt.original else stmt
+            return when (target) {
+                is net.sergeych.lyng.ExpressionStatement -> false
+                is net.sergeych.lyng.IfStatement -> {
+                    containsUnsupportedStatement(target.condition) ||
+                        containsUnsupportedStatement(target.ifBody) ||
+                        (target.elseBody?.let { containsUnsupportedStatement(it) } ?: false)
+                }
+                is net.sergeych.lyng.ForInStatement -> {
+                    target.constRange == null || target.canBreak ||
+                        containsUnsupportedStatement(target.source) ||
+                        containsUnsupportedStatement(target.body) ||
+                        (target.elseStatement?.let { containsUnsupportedStatement(it) } ?: false)
+                }
+                is net.sergeych.lyng.BlockStatement ->
+                    target.statements().any { containsUnsupportedStatement(it) }
+                is net.sergeych.lyng.VarDeclStatement ->
+                    target.initializer?.let { containsUnsupportedStatement(it) } ?: false
+                else -> true
+            }
+        }
+
+        private fun unwrapDeep(stmt: Statement): Statement {
+            return when (stmt) {
+                is BytecodeStatement -> unwrapDeep(stmt.original)
+                is net.sergeych.lyng.BlockStatement -> {
+                    val unwrapped = stmt.statements().map { unwrapDeep(it) }
+                    net.sergeych.lyng.BlockStatement(
+                        net.sergeych.lyng.Script(stmt.pos, unwrapped),
+                        stmt.slotPlan,
+                        stmt.pos
+                    )
+                }
+                is net.sergeych.lyng.VarDeclStatement -> {
+                    net.sergeych.lyng.VarDeclStatement(
+                        stmt.name,
+                        stmt.isMutable,
+                        stmt.visibility,
+                        stmt.initializer?.let { unwrapDeep(it) },
+                        stmt.isTransient,
+                        stmt.slotIndex,
+                        stmt.slotDepth,
+                        stmt.pos
+                    )
+                }
+                is net.sergeych.lyng.IfStatement -> {
+                    net.sergeych.lyng.IfStatement(
+                        unwrapDeep(stmt.condition),
+                        unwrapDeep(stmt.ifBody),
+                        stmt.elseBody?.let { unwrapDeep(it) },
+                        stmt.pos
+                    )
+                }
+                is net.sergeych.lyng.ForInStatement -> {
+                    net.sergeych.lyng.ForInStatement(
+                        stmt.loopVarName,
+                        unwrapDeep(stmt.source),
+                        stmt.constRange,
+                        unwrapDeep(stmt.body),
+                        stmt.elseStatement?.let { unwrapDeep(it) },
+                        stmt.label,
+                        stmt.canBreak,
+                        stmt.loopSlotPlan,
+                        stmt.pos
+                    )
+                }
+                else -> stmt
+            }
+        }
     }
 }

lynglib/src/commonMain/kotlin/net/sergeych/lyng/bytecode/CmdBuilder.kt

@@ -0,0 +1,356 @@
+/*
+ * Copyright 2026 Sergey S. Chernov
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.sergeych.lyng.bytecode
+
+class CmdBuilder {
+    sealed interface Operand {
+        data class IntVal(val value: Int) : Operand
+        data class LabelRef(val label: Label) : Operand
+    }
+
+    data class Label(val id: Int)
+
+    data class Instr(val op: Opcode, val operands: List<Operand>)
+
+    private val instructions = mutableListOf<Instr>()
+    private val constPool = mutableListOf<BytecodeConst>()
+    private val labelPositions = mutableMapOf<Label, Int>()
+    private var nextLabelId = 0
+    private val fallbackStatements = mutableListOf<net.sergeych.lyng.Statement>()
+
+    fun addConst(c: BytecodeConst): Int {
+        constPool += c
+        return constPool.lastIndex
+    }
+
+    fun emit(op: Opcode, vararg operands: Int) {
+        instructions += Instr(op, operands.map { Operand.IntVal(it) })
+    }
+
+    fun emit(op: Opcode, operands: List<Operand>) {
+        instructions += Instr(op, operands)
+    }
+
+    fun label(): Label = Label(nextLabelId++)
+
+    fun mark(label: Label) {
+        labelPositions[label] = instructions.size
+    }
+
+    fun addFallback(stmt: net.sergeych.lyng.Statement): Int {
+        fallbackStatements += stmt
+        return fallbackStatements.lastIndex
+    }
+
+    fun build(
+        name: String,
+        localCount: Int,
+        addrCount: Int = 0,
+        scopeSlotDepths: IntArray = IntArray(0),
+        scopeSlotIndices: IntArray = IntArray(0),
+        scopeSlotNames: Array<String?> = emptyArray(),
+        localSlotNames: Array<String?> = emptyArray(),
+        localSlotMutables: BooleanArray = BooleanArray(0),
+        localSlotDepths: IntArray = IntArray(0)
+    ): CmdFunction {
+        val scopeSlotCount = scopeSlotDepths.size
+        require(scopeSlotIndices.size == scopeSlotCount) { "scope slot mapping size mismatch" }
+        require(scopeSlotNames.isEmpty() || scopeSlotNames.size == scopeSlotCount) {
+            "scope slot name mapping size mismatch"
+        }
+        require(localSlotNames.size == localSlotMutables.size) { "local slot metadata size mismatch" }
+        require(localSlotNames.size == localSlotDepths.size) { "local slot depth metadata size mismatch" }
+        val labelIps = mutableMapOf<Label, Int>()
+        for ((label, idx) in labelPositions) {
+            labelIps[label] = idx
+        }
+        val cmds = ArrayList<Cmd>(instructions.size)
+        for (ins in instructions) {
+            val kinds = operandKinds(ins.op)
+            if (kinds.size != ins.operands.size) {
+                error("Operand count mismatch for ${ins.op}: expected ${kinds.size}, got ${ins.operands.size}")
+            }
+            val operands = IntArray(kinds.size)
+            for (i in kinds.indices) {
+                val operand = ins.operands[i]
+                val v = when (operand) {
+                    is Operand.IntVal -> operand.value
+                    is Operand.LabelRef -> labelIps[operand.label]
+                        ?: error("Unknown label ${operand.label.id} for ${ins.op}")
+                }
+                operands[i] = v
+            }
+            cmds.add(createCmd(ins.op, operands, scopeSlotCount))
+        }
+        return CmdFunction(
+            name = name,
+            localCount = localCount,
+            addrCount = addrCount,
+            scopeSlotCount = scopeSlotCount,
+            scopeSlotDepths = scopeSlotDepths,
+            scopeSlotIndices = scopeSlotIndices,
+            scopeSlotNames = if (scopeSlotNames.isEmpty()) Array(scopeSlotCount) { null } else scopeSlotNames,
+            localSlotNames = localSlotNames,
+            localSlotMutables = localSlotMutables,
+            localSlotDepths = localSlotDepths,
+            constants = constPool.toList(),
+            fallbackStatements = fallbackStatements.toList(),
+            cmds = cmds.toTypedArray()
+        )
+    }
+
+    private fun operandKinds(op: Opcode): List<OperandKind> {
+        return when (op) {
+            Opcode.NOP, Opcode.RET_VOID, Opcode.POP_SCOPE, Opcode.POP_SLOT_PLAN -> emptyList()
+            Opcode.MOVE_OBJ, Opcode.MOVE_INT, Opcode.MOVE_REAL, Opcode.MOVE_BOOL, Opcode.BOX_OBJ,
+            Opcode.INT_TO_REAL, Opcode.REAL_TO_INT, Opcode.BOOL_TO_INT, Opcode.INT_TO_BOOL,
+            Opcode.NEG_INT, Opcode.NEG_REAL, Opcode.NOT_BOOL, Opcode.INV_INT ->
+                listOf(OperandKind.SLOT, OperandKind.SLOT)
+            Opcode.RESOLVE_SCOPE_SLOT ->
+                listOf(OperandKind.SLOT, OperandKind.ADDR)
+            Opcode.LOAD_OBJ_ADDR, Opcode.LOAD_INT_ADDR, Opcode.LOAD_REAL_ADDR, Opcode.LOAD_BOOL_ADDR ->
+                listOf(OperandKind.ADDR, OperandKind.SLOT)
+            Opcode.STORE_OBJ_ADDR, Opcode.STORE_INT_ADDR, Opcode.STORE_REAL_ADDR, Opcode.STORE_BOOL_ADDR ->
+                listOf(OperandKind.SLOT, OperandKind.ADDR)
+            Opcode.CONST_NULL ->
+                listOf(OperandKind.SLOT)
+            Opcode.CONST_OBJ, Opcode.CONST_INT, Opcode.CONST_REAL, Opcode.CONST_BOOL ->
+                listOf(OperandKind.CONST, OperandKind.SLOT)
+            Opcode.PUSH_SCOPE, Opcode.PUSH_SLOT_PLAN ->
+                listOf(OperandKind.CONST)
+            Opcode.DECL_LOCAL ->
+                listOf(OperandKind.CONST, OperandKind.SLOT)
+            Opcode.ADD_INT, Opcode.SUB_INT, Opcode.MUL_INT, Opcode.DIV_INT, Opcode.MOD_INT,
+            Opcode.ADD_REAL, Opcode.SUB_REAL, Opcode.MUL_REAL, Opcode.DIV_REAL,
+            Opcode.AND_INT, Opcode.OR_INT, Opcode.XOR_INT, Opcode.SHL_INT, Opcode.SHR_INT, Opcode.USHR_INT,
+            Opcode.CMP_EQ_INT, Opcode.CMP_NEQ_INT, Opcode.CMP_LT_INT, Opcode.CMP_LTE_INT,
+            Opcode.CMP_GT_INT, Opcode.CMP_GTE_INT,
+            Opcode.CMP_EQ_REAL, Opcode.CMP_NEQ_REAL, Opcode.CMP_LT_REAL, Opcode.CMP_LTE_REAL,
+            Opcode.CMP_GT_REAL, Opcode.CMP_GTE_REAL,
+            Opcode.CMP_EQ_BOOL, Opcode.CMP_NEQ_BOOL,
+            Opcode.CMP_EQ_INT_REAL, Opcode.CMP_EQ_REAL_INT, Opcode.CMP_LT_INT_REAL, Opcode.CMP_LT_REAL_INT,
+            Opcode.CMP_LTE_INT_REAL, Opcode.CMP_LTE_REAL_INT, Opcode.CMP_GT_INT_REAL, Opcode.CMP_GT_REAL_INT,
+            Opcode.CMP_GTE_INT_REAL, Opcode.CMP_GTE_REAL_INT, Opcode.CMP_NEQ_INT_REAL, Opcode.CMP_NEQ_REAL_INT,
+            Opcode.CMP_EQ_OBJ, Opcode.CMP_NEQ_OBJ, Opcode.CMP_REF_EQ_OBJ, Opcode.CMP_REF_NEQ_OBJ,
+            Opcode.CMP_LT_OBJ, Opcode.CMP_LTE_OBJ, Opcode.CMP_GT_OBJ, Opcode.CMP_GTE_OBJ,
+            Opcode.ADD_OBJ, Opcode.SUB_OBJ, Opcode.MUL_OBJ, Opcode.DIV_OBJ, Opcode.MOD_OBJ,
+            Opcode.AND_BOOL, Opcode.OR_BOOL ->
+                listOf(OperandKind.SLOT, OperandKind.SLOT, OperandKind.SLOT)
+            Opcode.INC_INT, Opcode.DEC_INT, Opcode.RET ->
+                listOf(OperandKind.SLOT)
+            Opcode.JMP ->
+                listOf(OperandKind.IP)
+            Opcode.JMP_IF_TRUE, Opcode.JMP_IF_FALSE ->
+                listOf(OperandKind.SLOT, OperandKind.IP)
+            Opcode.CALL_DIRECT, Opcode.CALL_FALLBACK ->
+                listOf(OperandKind.ID, OperandKind.SLOT, OperandKind.COUNT, OperandKind.SLOT)
+            Opcode.CALL_SLOT ->
+                listOf(OperandKind.SLOT, OperandKind.SLOT, OperandKind.COUNT, OperandKind.SLOT)
+            Opcode.CALL_VIRTUAL ->
+                listOf(OperandKind.SLOT, OperandKind.ID, OperandKind.SLOT, OperandKind.COUNT, OperandKind.SLOT)
+            Opcode.GET_FIELD ->
+                listOf(OperandKind.SLOT, OperandKind.ID, OperandKind.SLOT)
+            Opcode.SET_FIELD ->
+                listOf(OperandKind.SLOT, OperandKind.ID, OperandKind.SLOT)
+            Opcode.GET_INDEX ->
+                listOf(OperandKind.SLOT, OperandKind.SLOT, OperandKind.SLOT)
+            Opcode.SET_INDEX ->
+                listOf(OperandKind.SLOT, OperandKind.SLOT, OperandKind.SLOT)
+            Opcode.EVAL_FALLBACK ->
+                listOf(OperandKind.ID, OperandKind.SLOT)
+        }
+    }
+
+    private enum class OperandKind {
+        SLOT,
+        ADDR,
+        CONST,
+        IP,
+        COUNT,
+        ID,
+    }
+
+    private fun createCmd(op: Opcode, operands: IntArray, scopeSlotCount: Int): Cmd {
+        return when (op) {
+            Opcode.NOP -> CmdNop()
+            Opcode.MOVE_OBJ -> CmdMoveObj(operands[0], operands[1])
+            Opcode.MOVE_INT -> if (operands[0] >= scopeSlotCount && operands[1] >= scopeSlotCount) {
+                CmdMoveIntLocal(operands[0] - scopeSlotCount, operands[1] - scopeSlotCount)
+            } else {
+                CmdMoveInt(operands[0], operands[1])
+            }
+            Opcode.MOVE_REAL -> CmdMoveReal(operands[0], operands[1])
+            Opcode.MOVE_BOOL -> CmdMoveBool(operands[0], operands[1])
+            Opcode.CONST_OBJ -> CmdConstObj(operands[0], operands[1])
+            Opcode.CONST_INT -> if (operands[1] >= scopeSlotCount) {
+                CmdConstIntLocal(operands[0], operands[1] - scopeSlotCount)
+            } else {
+                CmdConstInt(operands[0], operands[1])
+            }
+            Opcode.CONST_REAL -> CmdConstReal(operands[0], operands[1])
+            Opcode.CONST_BOOL -> CmdConstBool(operands[0], operands[1])
+            Opcode.CONST_NULL -> CmdConstNull(operands[0])
+            Opcode.BOX_OBJ -> CmdBoxObj(operands[0], operands[1])
+            Opcode.RESOLVE_SCOPE_SLOT -> CmdResolveScopeSlot(operands[0], operands[1])
+            Opcode.LOAD_OBJ_ADDR -> CmdLoadObjAddr(operands[0], operands[1])
+            Opcode.STORE_OBJ_ADDR -> CmdStoreObjAddr(operands[0], operands[1])
+            Opcode.LOAD_INT_ADDR -> CmdLoadIntAddr(operands[0], operands[1])
+            Opcode.STORE_INT_ADDR -> CmdStoreIntAddr(operands[0], operands[1])
+            Opcode.LOAD_REAL_ADDR -> CmdLoadRealAddr(operands[0], operands[1])
+            Opcode.STORE_REAL_ADDR -> CmdStoreRealAddr(operands[0], operands[1])
+            Opcode.LOAD_BOOL_ADDR -> CmdLoadBoolAddr(operands[0], operands[1])
+            Opcode.STORE_BOOL_ADDR -> CmdStoreBoolAddr(operands[0], operands[1])
+            Opcode.INT_TO_REAL -> CmdIntToReal(operands[0], operands[1])
+            Opcode.REAL_TO_INT -> CmdRealToInt(operands[0], operands[1])
+            Opcode.BOOL_TO_INT -> CmdBoolToInt(operands[0], operands[1])
+            Opcode.INT_TO_BOOL -> CmdIntToBool(operands[0], operands[1])
+            Opcode.ADD_INT -> if (operands[0] >= scopeSlotCount && operands[1] >= scopeSlotCount && operands[2] >= scopeSlotCount) {
+                CmdAddIntLocal(operands[0] - scopeSlotCount, operands[1] - scopeSlotCount, operands[2] - scopeSlotCount)
+            } else {
+                CmdAddInt(operands[0], operands[1], operands[2])
+            }
+            Opcode.SUB_INT -> if (operands[0] >= scopeSlotCount && operands[1] >= scopeSlotCount && operands[2] >= scopeSlotCount) {
+                CmdSubIntLocal(operands[0] - scopeSlotCount, operands[1] - scopeSlotCount, operands[2] - scopeSlotCount)
+            } else {
+                CmdSubInt(operands[0], operands[1], operands[2])
+            }
+            Opcode.MUL_INT -> if (operands[0] >= scopeSlotCount && operands[1] >= scopeSlotCount && operands[2] >= scopeSlotCount) {
+                CmdMulIntLocal(operands[0] - scopeSlotCount, operands[1] - scopeSlotCount, operands[2] - scopeSlotCount)
+            } else {
+                CmdMulInt(operands[0], operands[1], operands[2])
+            }
+            Opcode.DIV_INT -> if (operands[0] >= scopeSlotCount && operands[1] >= scopeSlotCount && operands[2] >= scopeSlotCount) {
+                CmdDivIntLocal(operands[0] - scopeSlotCount, operands[1] - scopeSlotCount, operands[2] - scopeSlotCount)
+            } else {
+                CmdDivInt(operands[0], operands[1], operands[2])
+            }
+            Opcode.MOD_INT -> if (operands[0] >= scopeSlotCount && operands[1] >= scopeSlotCount && operands[2] >= scopeSlotCount) {
+                CmdModIntLocal(operands[0] - scopeSlotCount, operands[1] - scopeSlotCount, operands[2] - scopeSlotCount)
+            } else {
+                CmdModInt(operands[0], operands[1], operands[2])
+            }
+            Opcode.NEG_INT -> CmdNegInt(operands[0], operands[1])
+            Opcode.INC_INT -> if (operands[0] >= scopeSlotCount) {
+                CmdIncIntLocal(operands[0] - scopeSlotCount)
+            } else {
+                CmdIncInt(operands[0])
+            }
+            Opcode.DEC_INT -> if (operands[0] >= scopeSlotCount) {
+                CmdDecIntLocal(operands[0] - scopeSlotCount)
+            } else {
+                CmdDecInt(operands[0])
+            }
+            Opcode.ADD_REAL -> CmdAddReal(operands[0], operands[1], operands[2])
+            Opcode.SUB_REAL -> CmdSubReal(operands[0], operands[1], operands[2])
+            Opcode.MUL_REAL -> CmdMulReal(operands[0], operands[1], operands[2])
+            Opcode.DIV_REAL -> CmdDivReal(operands[0], operands[1], operands[2])
+            Opcode.NEG_REAL -> CmdNegReal(operands[0], operands[1])
+            Opcode.AND_INT -> CmdAndInt(operands[0], operands[1], operands[2])
+            Opcode.OR_INT -> CmdOrInt(operands[0], operands[1], operands[2])
+            Opcode.XOR_INT -> CmdXorInt(operands[0], operands[1], operands[2])
+            Opcode.SHL_INT -> CmdShlInt(operands[0], operands[1], operands[2])
+            Opcode.SHR_INT -> CmdShrInt(operands[0], operands[1], operands[2])
+            Opcode.USHR_INT -> CmdUshrInt(operands[0], operands[1], operands[2])
+            Opcode.INV_INT -> CmdInvInt(operands[0], operands[1])
+            Opcode.CMP_EQ_INT -> if (operands[0] >= scopeSlotCount && operands[1] >= scopeSlotCount && operands[2] >= scopeSlotCount) {
+                CmdCmpEqIntLocal(operands[0] - scopeSlotCount, operands[1] - scopeSlotCount, operands[2] - scopeSlotCount)
+            } else {
+                CmdCmpEqInt(operands[0], operands[1], operands[2])
+            }
+            Opcode.CMP_NEQ_INT -> if (operands[0] >= scopeSlotCount && operands[1] >= scopeSlotCount && operands[2] >= scopeSlotCount) {
+                CmdCmpNeqIntLocal(operands[0] - scopeSlotCount, operands[1] - scopeSlotCount, operands[2] - scopeSlotCount)
+            } else {
+                CmdCmpNeqInt(operands[0], operands[1], operands[2])
+            }
+            Opcode.CMP_LT_INT -> if (operands[0] >= scopeSlotCount && operands[1] >= scopeSlotCount && operands[2] >= scopeSlotCount) {
+                CmdCmpLtIntLocal(operands[0] - scopeSlotCount, operands[1] - scopeSlotCount, operands[2] - scopeSlotCount)
+            } else {
+                CmdCmpLtInt(operands[0], operands[1], operands[2])
+            }
+            Opcode.CMP_LTE_INT -> if (operands[0] >= scopeSlotCount && operands[1] >= scopeSlotCount && operands[2] >= scopeSlotCount) {
+                CmdCmpLteIntLocal(operands[0] - scopeSlotCount, operands[1] - scopeSlotCount, operands[2] - scopeSlotCount)
+            } else {
+                CmdCmpLteInt(operands[0], operands[1], operands[2])
+            }
+            Opcode.CMP_GT_INT -> if (operands[0] >= scopeSlotCount && operands[1] >= scopeSlotCount && operands[2] >= scopeSlotCount) {
+                CmdCmpGtIntLocal(operands[0] - scopeSlotCount, operands[1] - scopeSlotCount, operands[2] - scopeSlotCount)
+            } else {
+                CmdCmpGtInt(operands[0], operands[1], operands[2])
+            }
+            Opcode.CMP_GTE_INT -> if (operands[0] >= scopeSlotCount && operands[1] >= scopeSlotCount && operands[2] >= scopeSlotCount) {
+                CmdCmpGteIntLocal(operands[0] - scopeSlotCount, operands[1] - scopeSlotCount, operands[2] - scopeSlotCount)
+            } else {
+                CmdCmpGteInt(operands[0], operands[1], operands[2])
+            }
+            Opcode.CMP_EQ_REAL -> CmdCmpEqReal(operands[0], operands[1], operands[2])
+            Opcode.CMP_NEQ_REAL -> CmdCmpNeqReal(operands[0], operands[1], operands[2])
+            Opcode.CMP_LT_REAL -> CmdCmpLtReal(operands[0], operands[1], operands[2])
+            Opcode.CMP_LTE_REAL -> CmdCmpLteReal(operands[0], operands[1], operands[2])
+            Opcode.CMP_GT_REAL -> CmdCmpGtReal(operands[0], operands[1], operands[2])
+            Opcode.CMP_GTE_REAL -> CmdCmpGteReal(operands[0], operands[1], operands[2])
+            Opcode.CMP_EQ_BOOL -> CmdCmpEqBool(operands[0], operands[1], operands[2])
+            Opcode.CMP_NEQ_BOOL -> CmdCmpNeqBool(operands[0], operands[1], operands[2])
+            Opcode.CMP_EQ_INT_REAL -> CmdCmpEqIntReal(operands[0], operands[1], operands[2])
+            Opcode.CMP_EQ_REAL_INT -> CmdCmpEqRealInt(operands[0], operands[1], operands[2])
+            Opcode.CMP_LT_INT_REAL -> CmdCmpLtIntReal(operands[0], operands[1], operands[2])
+            Opcode.CMP_LT_REAL_INT -> CmdCmpLtRealInt(operands[0], operands[1], operands[2])
+            Opcode.CMP_LTE_INT_REAL -> CmdCmpLteIntReal(operands[0], operands[1], operands[2])
+            Opcode.CMP_LTE_REAL_INT -> CmdCmpLteRealInt(operands[0], operands[1], operands[2])
+            Opcode.CMP_GT_INT_REAL -> CmdCmpGtIntReal(operands[0], operands[1], operands[2])
+            Opcode.CMP_GT_REAL_INT -> CmdCmpGtRealInt(operands[0], operands[1], operands[2])
+            Opcode.CMP_GTE_INT_REAL -> CmdCmpGteIntReal(operands[0], operands[1], operands[2])
+            Opcode.CMP_GTE_REAL_INT -> CmdCmpGteRealInt(operands[0], operands[1], operands[2])
+            Opcode.CMP_NEQ_INT_REAL -> CmdCmpNeqIntReal(operands[0], operands[1], operands[2])
+            Opcode.CMP_NEQ_REAL_INT -> CmdCmpNeqRealInt(operands[0], operands[1], operands[2])
+            Opcode.CMP_EQ_OBJ -> CmdCmpEqObj(operands[0], operands[1], operands[2])
+            Opcode.CMP_NEQ_OBJ -> CmdCmpNeqObj(operands[0], operands[1], operands[2])
+            Opcode.CMP_REF_EQ_OBJ -> CmdCmpRefEqObj(operands[0], operands[1], operands[2])
+            Opcode.CMP_REF_NEQ_OBJ -> CmdCmpRefNeqObj(operands[0], operands[1], operands[2])
+            Opcode.NOT_BOOL -> CmdNotBool(operands[0], operands[1])
+            Opcode.AND_BOOL -> CmdAndBool(operands[0], operands[1], operands[2])
+            Opcode.OR_BOOL -> CmdOrBool(operands[0], operands[1], operands[2])
+            Opcode.CMP_LT_OBJ -> CmdCmpLtObj(operands[0], operands[1], operands[2])
+            Opcode.CMP_LTE_OBJ -> CmdCmpLteObj(operands[0], operands[1], operands[2])
+            Opcode.CMP_GT_OBJ -> CmdCmpGtObj(operands[0], operands[1], operands[2])
+            Opcode.CMP_GTE_OBJ -> CmdCmpGteObj(operands[0], operands[1], operands[2])
+            Opcode.ADD_OBJ -> CmdAddObj(operands[0], operands[1], operands[2])
+            Opcode.SUB_OBJ -> CmdSubObj(operands[0], operands[1], operands[2])
+            Opcode.MUL_OBJ -> CmdMulObj(operands[0], operands[1], operands[2])
+            Opcode.DIV_OBJ -> CmdDivObj(operands[0], operands[1], operands[2])
+            Opcode.MOD_OBJ -> CmdModObj(operands[0], operands[1], operands[2])
+            Opcode.JMP -> CmdJmp(operands[0])
+            Opcode.JMP_IF_TRUE -> CmdJmpIfTrue(operands[0], operands[1])
+            Opcode.JMP_IF_FALSE -> CmdJmpIfFalse(operands[0], operands[1])
+            Opcode.RET -> CmdRet(operands[0])
+            Opcode.RET_VOID -> CmdRetVoid()
+            Opcode.PUSH_SCOPE -> CmdPushScope(operands[0])
+            Opcode.POP_SCOPE -> CmdPopScope()
+            Opcode.PUSH_SLOT_PLAN -> CmdPushSlotPlan(operands[0])
+            Opcode.POP_SLOT_PLAN -> CmdPopSlotPlan()
+            Opcode.DECL_LOCAL -> CmdDeclLocal(operands[0], operands[1])
+            Opcode.CALL_DIRECT -> CmdCallDirect(operands[0], operands[1], operands[2], operands[3])
+            Opcode.CALL_VIRTUAL -> CmdCallVirtual(operands[0], operands[1], operands[2], operands[3], operands[4])
+            Opcode.CALL_FALLBACK -> CmdCallFallback(operands[0], operands[1], operands[2], operands[3])
+            Opcode.CALL_SLOT -> CmdCallSlot(operands[0], operands[1], operands[2], operands[3])
+            Opcode.GET_FIELD -> CmdGetField(operands[0], operands[1], operands[2])
+            Opcode.SET_FIELD -> CmdSetField(operands[0], operands[1], operands[2])
+            Opcode.GET_INDEX -> CmdGetIndex(operands[0], operands[1], operands[2])
+            Opcode.SET_INDEX -> CmdSetIndex(operands[0], operands[1], operands[2])
+            Opcode.EVAL_FALLBACK -> CmdEvalFallback(operands[0], operands[1])
+        }
+    }
+}

lynglib/src/commonMain/kotlin/net/sergeych/lyng/bytecode/CmdCallSiteCache.kt

@@ -16,6 +16,6 @@
 
 package net.sergeych.lyng.bytecode
 
-internal expect object BytecodeCallSiteCache {
+internal expect object CmdCallSiteCache {
-    fun methodCallSites(fn: BytecodeFunction): MutableMap<Int, MethodCallSite>
+    fun methodCallSites(fn: CmdFunction): MutableMap<Int, MethodCallSite>
 }

lynglib/src/commonMain/kotlin/net/sergeych/lyng/bytecode/CmdDisassembler.kt

@@ -0,0 +1,251 @@
+/*
+ * Copyright 2026 Sergey S. Chernov
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.sergeych.lyng.bytecode
+
+object CmdDisassembler {
+    fun disassemble(fn: CmdFunction): String {
+        val out = StringBuilder()
+        val cmds = fn.cmds
+        for (i in cmds.indices) {
+            val (op, opValues) = opAndOperands(fn, cmds[i])
+            val kinds = operandKinds(op)
+            val operands = ArrayList<String>(kinds.size)
+            for (k in kinds.indices) {
+                val v = opValues.getOrElse(k) { 0 }
+                when (kinds[k]) {
+                    OperandKind.SLOT -> {
+                        val name = when {
+                            v < fn.scopeSlotCount -> fn.scopeSlotNames[v]
+                            else -> {
+                                val localIndex = v - fn.scopeSlotCount
+                                fn.localSlotNames.getOrNull(localIndex)
+                            }
+                        }
+                        operands += if (name != null) "s$v($name)" else "s$v"
+                    }
+                    OperandKind.ADDR -> operands += "a$v"
+                    OperandKind.CONST -> operands += "k$v"
+                    OperandKind.IP -> operands += "ip$v"
+                    OperandKind.COUNT -> operands += "n$v"
+                    OperandKind.ID -> operands += "#$v"
+                }
+            }
+            out.append(i).append(": ").append(op.name)
+            if (operands.isNotEmpty()) {
+                out.append(' ').append(operands.joinToString(", "))
+            }
+            out.append('\n')
+        }
+        return out.toString()
+    }
+
+    private fun opAndOperands(fn: CmdFunction, cmd: Cmd): Pair<Opcode, IntArray> {
+        return when (cmd) {
+            is CmdNop -> Opcode.NOP to intArrayOf()
+            is CmdMoveObj -> Opcode.MOVE_OBJ to intArrayOf(cmd.src, cmd.dst)
+            is CmdMoveInt -> Opcode.MOVE_INT to intArrayOf(cmd.src, cmd.dst)
+            is CmdMoveIntLocal -> Opcode.MOVE_INT to intArrayOf(cmd.src + fn.scopeSlotCount, cmd.dst + fn.scopeSlotCount)
+            is CmdMoveReal -> Opcode.MOVE_REAL to intArrayOf(cmd.src, cmd.dst)
+            is CmdMoveBool -> Opcode.MOVE_BOOL to intArrayOf(cmd.src, cmd.dst)
+            is CmdConstObj -> Opcode.CONST_OBJ to intArrayOf(cmd.constId, cmd.dst)
+            is CmdConstInt -> Opcode.CONST_INT to intArrayOf(cmd.constId, cmd.dst)
+            is CmdConstIntLocal -> Opcode.CONST_INT to intArrayOf(cmd.constId, cmd.dst + fn.scopeSlotCount)
+            is CmdConstReal -> Opcode.CONST_REAL to intArrayOf(cmd.constId, cmd.dst)
+            is CmdConstBool -> Opcode.CONST_BOOL to intArrayOf(cmd.constId, cmd.dst)
+            is CmdConstNull -> Opcode.CONST_NULL to intArrayOf(cmd.dst)
+            is CmdBoxObj -> Opcode.BOX_OBJ to intArrayOf(cmd.src, cmd.dst)
+            is CmdResolveScopeSlot -> Opcode.RESOLVE_SCOPE_SLOT to intArrayOf(cmd.scopeSlot, cmd.addrSlot)
+            is CmdLoadObjAddr -> Opcode.LOAD_OBJ_ADDR to intArrayOf(cmd.addrSlot, cmd.dst)
+            is CmdStoreObjAddr -> Opcode.STORE_OBJ_ADDR to intArrayOf(cmd.src, cmd.addrSlot)
+            is CmdLoadIntAddr -> Opcode.LOAD_INT_ADDR to intArrayOf(cmd.addrSlot, cmd.dst)
+            is CmdStoreIntAddr -> Opcode.STORE_INT_ADDR to intArrayOf(cmd.src, cmd.addrSlot)
+            is CmdLoadRealAddr -> Opcode.LOAD_REAL_ADDR to intArrayOf(cmd.addrSlot, cmd.dst)
+            is CmdStoreRealAddr -> Opcode.STORE_REAL_ADDR to intArrayOf(cmd.src, cmd.addrSlot)
+            is CmdLoadBoolAddr -> Opcode.LOAD_BOOL_ADDR to intArrayOf(cmd.addrSlot, cmd.dst)
+            is CmdStoreBoolAddr -> Opcode.STORE_BOOL_ADDR to intArrayOf(cmd.src, cmd.addrSlot)
+            is CmdIntToReal -> Opcode.INT_TO_REAL to intArrayOf(cmd.src, cmd.dst)
+            is CmdRealToInt -> Opcode.REAL_TO_INT to intArrayOf(cmd.src, cmd.dst)
+            is CmdBoolToInt -> Opcode.BOOL_TO_INT to intArrayOf(cmd.src, cmd.dst)
+            is CmdIntToBool -> Opcode.INT_TO_BOOL to intArrayOf(cmd.src, cmd.dst)
+            is CmdAddInt -> Opcode.ADD_INT to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdAddIntLocal -> Opcode.ADD_INT to intArrayOf(cmd.a + fn.scopeSlotCount, cmd.b + fn.scopeSlotCount, cmd.dst + fn.scopeSlotCount)
+            is CmdSubInt -> Opcode.SUB_INT to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdSubIntLocal -> Opcode.SUB_INT to intArrayOf(cmd.a + fn.scopeSlotCount, cmd.b + fn.scopeSlotCount, cmd.dst + fn.scopeSlotCount)
+            is CmdMulInt -> Opcode.MUL_INT to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdMulIntLocal -> Opcode.MUL_INT to intArrayOf(cmd.a + fn.scopeSlotCount, cmd.b + fn.scopeSlotCount, cmd.dst + fn.scopeSlotCount)
+            is CmdDivInt -> Opcode.DIV_INT to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdDivIntLocal -> Opcode.DIV_INT to intArrayOf(cmd.a + fn.scopeSlotCount, cmd.b + fn.scopeSlotCount, cmd.dst + fn.scopeSlotCount)
+            is CmdModInt -> Opcode.MOD_INT to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdModIntLocal -> Opcode.MOD_INT to intArrayOf(cmd.a + fn.scopeSlotCount, cmd.b + fn.scopeSlotCount, cmd.dst + fn.scopeSlotCount)
+            is CmdNegInt -> Opcode.NEG_INT to intArrayOf(cmd.src, cmd.dst)
+            is CmdIncInt -> Opcode.INC_INT to intArrayOf(cmd.slot)
+            is CmdIncIntLocal -> Opcode.INC_INT to intArrayOf(cmd.slot + fn.scopeSlotCount)
+            is CmdDecInt -> Opcode.DEC_INT to intArrayOf(cmd.slot)
+            is CmdDecIntLocal -> Opcode.DEC_INT to intArrayOf(cmd.slot + fn.scopeSlotCount)
+            is CmdAddReal -> Opcode.ADD_REAL to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdSubReal -> Opcode.SUB_REAL to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdMulReal -> Opcode.MUL_REAL to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdDivReal -> Opcode.DIV_REAL to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdNegReal -> Opcode.NEG_REAL to intArrayOf(cmd.src, cmd.dst)
+            is CmdAndInt -> Opcode.AND_INT to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdOrInt -> Opcode.OR_INT to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdXorInt -> Opcode.XOR_INT to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdShlInt -> Opcode.SHL_INT to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdShrInt -> Opcode.SHR_INT to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdUshrInt -> Opcode.USHR_INT to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdInvInt -> Opcode.INV_INT to intArrayOf(cmd.src, cmd.dst)
+            is CmdCmpEqInt -> Opcode.CMP_EQ_INT to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdCmpEqIntLocal -> Opcode.CMP_EQ_INT to intArrayOf(cmd.a + fn.scopeSlotCount, cmd.b + fn.scopeSlotCount, cmd.dst + fn.scopeSlotCount)
+            is CmdCmpNeqInt -> Opcode.CMP_NEQ_INT to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdCmpNeqIntLocal -> Opcode.CMP_NEQ_INT to intArrayOf(cmd.a + fn.scopeSlotCount, cmd.b + fn.scopeSlotCount, cmd.dst + fn.scopeSlotCount)
+            is CmdCmpLtInt -> Opcode.CMP_LT_INT to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdCmpLtIntLocal -> Opcode.CMP_LT_INT to intArrayOf(cmd.a + fn.scopeSlotCount, cmd.b + fn.scopeSlotCount, cmd.dst + fn.scopeSlotCount)
+            is CmdCmpLteInt -> Opcode.CMP_LTE_INT to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdCmpLteIntLocal -> Opcode.CMP_LTE_INT to intArrayOf(cmd.a + fn.scopeSlotCount, cmd.b + fn.scopeSlotCount, cmd.dst + fn.scopeSlotCount)
+            is CmdCmpGtInt -> Opcode.CMP_GT_INT to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdCmpGtIntLocal -> Opcode.CMP_GT_INT to intArrayOf(cmd.a + fn.scopeSlotCount, cmd.b + fn.scopeSlotCount, cmd.dst + fn.scopeSlotCount)
+            is CmdCmpGteInt -> Opcode.CMP_GTE_INT to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdCmpGteIntLocal -> Opcode.CMP_GTE_INT to intArrayOf(cmd.a + fn.scopeSlotCount, cmd.b + fn.scopeSlotCount, cmd.dst + fn.scopeSlotCount)
+            is CmdCmpEqReal -> Opcode.CMP_EQ_REAL to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdCmpNeqReal -> Opcode.CMP_NEQ_REAL to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdCmpLtReal -> Opcode.CMP_LT_REAL to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdCmpLteReal -> Opcode.CMP_LTE_REAL to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdCmpGtReal -> Opcode.CMP_GT_REAL to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdCmpGteReal -> Opcode.CMP_GTE_REAL to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdCmpEqBool -> Opcode.CMP_EQ_BOOL to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdCmpNeqBool -> Opcode.CMP_NEQ_BOOL to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdCmpEqIntReal -> Opcode.CMP_EQ_INT_REAL to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdCmpEqRealInt -> Opcode.CMP_EQ_REAL_INT to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdCmpLtIntReal -> Opcode.CMP_LT_INT_REAL to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdCmpLtRealInt -> Opcode.CMP_LT_REAL_INT to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdCmpLteIntReal -> Opcode.CMP_LTE_INT_REAL to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdCmpLteRealInt -> Opcode.CMP_LTE_REAL_INT to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdCmpGtIntReal -> Opcode.CMP_GT_INT_REAL to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdCmpGtRealInt -> Opcode.CMP_GT_REAL_INT to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdCmpGteIntReal -> Opcode.CMP_GTE_INT_REAL to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdCmpGteRealInt -> Opcode.CMP_GTE_REAL_INT to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdCmpNeqIntReal -> Opcode.CMP_NEQ_INT_REAL to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdCmpNeqRealInt -> Opcode.CMP_NEQ_REAL_INT to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdCmpEqObj -> Opcode.CMP_EQ_OBJ to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdCmpNeqObj -> Opcode.CMP_NEQ_OBJ to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdCmpRefEqObj -> Opcode.CMP_REF_EQ_OBJ to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdCmpRefNeqObj -> Opcode.CMP_REF_NEQ_OBJ to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdNotBool -> Opcode.NOT_BOOL to intArrayOf(cmd.src, cmd.dst)
+            is CmdAndBool -> Opcode.AND_BOOL to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdOrBool -> Opcode.OR_BOOL to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdCmpLtObj -> Opcode.CMP_LT_OBJ to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdCmpLteObj -> Opcode.CMP_LTE_OBJ to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdCmpGtObj -> Opcode.CMP_GT_OBJ to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdCmpGteObj -> Opcode.CMP_GTE_OBJ to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdAddObj -> Opcode.ADD_OBJ to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdSubObj -> Opcode.SUB_OBJ to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdMulObj -> Opcode.MUL_OBJ to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdDivObj -> Opcode.DIV_OBJ to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdModObj -> Opcode.MOD_OBJ to intArrayOf(cmd.a, cmd.b, cmd.dst)
+            is CmdJmp -> Opcode.JMP to intArrayOf(cmd.target)
+            is CmdJmpIfTrue -> Opcode.JMP_IF_TRUE to intArrayOf(cmd.cond, cmd.target)
+            is CmdJmpIfFalse -> Opcode.JMP_IF_FALSE to intArrayOf(cmd.cond, cmd.target)
+            is CmdRet -> Opcode.RET to intArrayOf(cmd.slot)
+            is CmdRetVoid -> Opcode.RET_VOID to intArrayOf()
+            is CmdPushScope -> Opcode.PUSH_SCOPE to intArrayOf(cmd.planId)
+            is CmdPopScope -> Opcode.POP_SCOPE to intArrayOf()
+            is CmdPushSlotPlan -> Opcode.PUSH_SLOT_PLAN to intArrayOf(cmd.planId)
+            is CmdPopSlotPlan -> Opcode.POP_SLOT_PLAN to intArrayOf()
+            is CmdDeclLocal -> Opcode.DECL_LOCAL to intArrayOf(cmd.constId, cmd.slot)
+            is CmdCallDirect -> Opcode.CALL_DIRECT to intArrayOf(cmd.id, cmd.argBase, cmd.argCount, cmd.dst)
+            is CmdCallVirtual -> Opcode.CALL_VIRTUAL to intArrayOf(cmd.recvSlot, cmd.methodId, cmd.argBase, cmd.argCount, cmd.dst)
+            is CmdCallFallback -> Opcode.CALL_FALLBACK to intArrayOf(cmd.id, cmd.argBase, cmd.argCount, cmd.dst)
+            is CmdCallSlot -> Opcode.CALL_SLOT to intArrayOf(cmd.calleeSlot, cmd.argBase, cmd.argCount, cmd.dst)
+            is CmdGetField -> Opcode.GET_FIELD to intArrayOf(cmd.recvSlot, cmd.fieldId, cmd.dst)
+            is CmdSetField -> Opcode.SET_FIELD to intArrayOf(cmd.recvSlot, cmd.fieldId, cmd.valueSlot)
+            is CmdGetIndex -> Opcode.GET_INDEX to intArrayOf(cmd.targetSlot, cmd.indexSlot, cmd.dst)
+            is CmdSetIndex -> Opcode.SET_INDEX to intArrayOf(cmd.targetSlot, cmd.indexSlot, cmd.valueSlot)
+            is CmdEvalFallback -> Opcode.EVAL_FALLBACK to intArrayOf(cmd.id, cmd.dst)
+        }
+    }
+
+    private enum class OperandKind {
+        SLOT,
+        ADDR,
+        CONST,
+        IP,
+        COUNT,
+        ID,
+    }
+
+    private fun operandKinds(op: Opcode): List<OperandKind> {
+        return when (op) {
+            Opcode.NOP, Opcode.RET_VOID, Opcode.POP_SCOPE, Opcode.POP_SLOT_PLAN -> emptyList()
+            Opcode.MOVE_OBJ, Opcode.MOVE_INT, Opcode.MOVE_REAL, Opcode.MOVE_BOOL, Opcode.BOX_OBJ,
+            Opcode.INT_TO_REAL, Opcode.REAL_TO_INT, Opcode.BOOL_TO_INT, Opcode.INT_TO_BOOL,
+            Opcode.NEG_INT, Opcode.NEG_REAL, Opcode.NOT_BOOL, Opcode.INV_INT ->
+                listOf(OperandKind.SLOT, OperandKind.SLOT)
+            Opcode.RESOLVE_SCOPE_SLOT ->
+                listOf(OperandKind.SLOT, OperandKind.ADDR)
+            Opcode.LOAD_OBJ_ADDR, Opcode.LOAD_INT_ADDR, Opcode.LOAD_REAL_ADDR, Opcode.LOAD_BOOL_ADDR ->
+                listOf(OperandKind.ADDR, OperandKind.SLOT)
+            Opcode.STORE_OBJ_ADDR, Opcode.STORE_INT_ADDR, Opcode.STORE_REAL_ADDR, Opcode.STORE_BOOL_ADDR ->
+                listOf(OperandKind.SLOT, OperandKind.ADDR)
+            Opcode.CONST_NULL ->
+                listOf(OperandKind.SLOT)
+            Opcode.CONST_OBJ, Opcode.CONST_INT, Opcode.CONST_REAL, Opcode.CONST_BOOL ->
+                listOf(OperandKind.CONST, OperandKind.SLOT)
+            Opcode.PUSH_SCOPE, Opcode.PUSH_SLOT_PLAN ->
+                listOf(OperandKind.CONST)
+            Opcode.DECL_LOCAL ->
+                listOf(OperandKind.CONST, OperandKind.SLOT)
+            Opcode.ADD_INT, Opcode.SUB_INT, Opcode.MUL_INT, Opcode.DIV_INT, Opcode.MOD_INT,
+            Opcode.ADD_REAL, Opcode.SUB_REAL, Opcode.MUL_REAL, Opcode.DIV_REAL,
+            Opcode.AND_INT, Opcode.OR_INT, Opcode.XOR_INT, Opcode.SHL_INT, Opcode.SHR_INT, Opcode.USHR_INT,
+            Opcode.CMP_EQ_INT, Opcode.CMP_NEQ_INT, Opcode.CMP_LT_INT, Opcode.CMP_LTE_INT,
+            Opcode.CMP_GT_INT, Opcode.CMP_GTE_INT,
+            Opcode.CMP_EQ_REAL, Opcode.CMP_NEQ_REAL, Opcode.CMP_LT_REAL, Opcode.CMP_LTE_REAL,
+            Opcode.CMP_GT_REAL, Opcode.CMP_GTE_REAL,
+            Opcode.CMP_EQ_BOOL, Opcode.CMP_NEQ_BOOL,
+            Opcode.CMP_EQ_INT_REAL, Opcode.CMP_EQ_REAL_INT, Opcode.CMP_LT_INT_REAL, Opcode.CMP_LT_REAL_INT,
+            Opcode.CMP_LTE_INT_REAL, Opcode.CMP_LTE_REAL_INT, Opcode.CMP_GT_INT_REAL, Opcode.CMP_GT_REAL_INT,
+            Opcode.CMP_GTE_INT_REAL, Opcode.CMP_GTE_REAL_INT, Opcode.CMP_NEQ_INT_REAL, Opcode.CMP_NEQ_REAL_INT,
+            Opcode.CMP_EQ_OBJ, Opcode.CMP_NEQ_OBJ, Opcode.CMP_REF_EQ_OBJ, Opcode.CMP_REF_NEQ_OBJ,
+            Opcode.CMP_LT_OBJ, Opcode.CMP_LTE_OBJ, Opcode.CMP_GT_OBJ, Opcode.CMP_GTE_OBJ,
+            Opcode.ADD_OBJ, Opcode.SUB_OBJ, Opcode.MUL_OBJ, Opcode.DIV_OBJ, Opcode.MOD_OBJ,
+            Opcode.AND_BOOL, Opcode.OR_BOOL ->
+                listOf(OperandKind.SLOT, OperandKind.SLOT, OperandKind.SLOT)
+            Opcode.INC_INT, Opcode.DEC_INT, Opcode.RET ->
+                listOf(OperandKind.SLOT)
+            Opcode.JMP ->
+                listOf(OperandKind.IP)
+            Opcode.JMP_IF_TRUE, Opcode.JMP_IF_FALSE ->
+                listOf(OperandKind.SLOT, OperandKind.IP)
+            Opcode.CALL_DIRECT, Opcode.CALL_FALLBACK ->
+                listOf(OperandKind.ID, OperandKind.SLOT, OperandKind.COUNT, OperandKind.SLOT)
+            Opcode.CALL_SLOT ->
+                listOf(OperandKind.SLOT, OperandKind.SLOT, OperandKind.COUNT, OperandKind.SLOT)
+            Opcode.CALL_VIRTUAL ->
+                listOf(OperandKind.SLOT, OperandKind.ID, OperandKind.SLOT, OperandKind.COUNT, OperandKind.SLOT)
+            Opcode.GET_FIELD ->
+                listOf(OperandKind.SLOT, OperandKind.ID, OperandKind.SLOT)
+            Opcode.SET_FIELD ->
+                listOf(OperandKind.SLOT, OperandKind.ID, OperandKind.SLOT)
+            Opcode.GET_INDEX ->
+                listOf(OperandKind.SLOT, OperandKind.SLOT, OperandKind.SLOT)
+            Opcode.SET_INDEX ->
+                listOf(OperandKind.SLOT, OperandKind.SLOT, OperandKind.SLOT)
+            Opcode.EVAL_FALLBACK ->
+                listOf(OperandKind.ID, OperandKind.SLOT)
+        }
+    }
+}

lynglib/src/commonMain/kotlin/net/sergeych/lyng/bytecode/CmdFunction.kt

@@ -16,26 +16,28 @@
 
 package net.sergeych.lyng.bytecode
 
-data class BytecodeFunction(
+data class CmdFunction(
     val name: String,
     val localCount: Int,
+    val addrCount: Int,
     val scopeSlotCount: Int,
     val scopeSlotDepths: IntArray,
     val scopeSlotIndices: IntArray,
     val scopeSlotNames: Array<String?>,
-    val slotWidth: Int,
+    val localSlotNames: Array<String?>,
-    val ipWidth: Int,
+    val localSlotMutables: BooleanArray,
-    val constIdWidth: Int,
+    val localSlotDepths: IntArray,
     val constants: List<BytecodeConst>,
     val fallbackStatements: List<net.sergeych.lyng.Statement>,
-    val code: ByteArray,
+    val cmds: Array<Cmd>,
 ) {
     init {
-        require(slotWidth == 1 || slotWidth == 2 || slotWidth == 4) { "slotWidth must be 1,2,4" }
-        require(ipWidth == 2 || ipWidth == 4) { "ipWidth must be 2 or 4" }
-        require(constIdWidth == 2 || constIdWidth == 4) { "constIdWidth must be 2 or 4" }
         require(scopeSlotDepths.size == scopeSlotCount) { "scopeSlotDepths size mismatch" }
         require(scopeSlotIndices.size == scopeSlotCount) { "scopeSlotIndices size mismatch" }
         require(scopeSlotNames.size == scopeSlotCount) { "scopeSlotNames size mismatch" }
+        require(localSlotNames.size == localSlotMutables.size) { "localSlot metadata size mismatch" }
+        require(localSlotNames.size == localSlotDepths.size) { "localSlot depth metadata size mismatch" }
+        require(localSlotNames.size <= localCount) { "localSlotNames exceed localCount" }
+        require(addrCount >= 0) { "addrCount must be non-negative" }
     }
 }

lynglib/src/commonMain/kotlin/net/sergeych/lyng/bytecode/Opcode.kt

@@ -124,6 +124,15 @@ enum class Opcode(val code: Int) {
     SET_INDEX(0xA3),
 
     EVAL_FALLBACK(0xB0),
+    RESOLVE_SCOPE_SLOT(0xB1),
+    LOAD_OBJ_ADDR(0xB2),
+    STORE_OBJ_ADDR(0xB3),
+    LOAD_INT_ADDR(0xB4),
+    STORE_INT_ADDR(0xB5),
+    LOAD_REAL_ADDR(0xB6),
+    STORE_REAL_ADDR(0xB7),
+    LOAD_BOOL_ADDR(0xB8),
+    STORE_BOOL_ADDR(0xB9),
     ;
 
     companion object {

lynglib/src/commonMain/kotlin/net/sergeych/lyng/obj/ObjRef.kt

@@ -1991,6 +1991,10 @@ class LocalVarRef(val name: String, private val atPos: Pos) : ObjRef {
                 scope.assign(rec, name, newValue)
                 return
             }
+            scope.chainLookupIgnoreClosure(name, followClosure = true, caller = scope.currentClassCtx)?.let { rec ->
+                scope.assign(rec, name, newValue)
+                return
+            }
             scope[name]?.let { stored ->
                 scope.assign(stored, name, newValue)
                 return
@@ -2007,6 +2011,10 @@ class LocalVarRef(val name: String, private val atPos: Pos) : ObjRef {
                 return
             }
         }
+        scope.chainLookupIgnoreClosure(name, followClosure = true, caller = scope.currentClassCtx)?.let { rec ->
+            scope.assign(rec, name, newValue)
+            return
+        }
         scope[name]?.let { stored ->
             scope.assign(stored, name, newValue)
             return
@@ -2417,6 +2425,7 @@ class LocalSlotRef(
     val name: String,
     internal val slot: Int,
     internal val depth: Int,
+    internal val scopeDepth: Int,
     internal val isMutable: Boolean,
     internal val isDelegated: Boolean,
     private val atPos: Pos,

lynglib/src/commonTest/kotlin/CmdVmTest.kt

@@ -19,10 +19,10 @@ import net.sergeych.lyng.IfStatement
 import net.sergeych.lyng.Pos
 import net.sergeych.lyng.Scope
 import net.sergeych.lyng.Statement
-import net.sergeych.lyng.bytecode.BytecodeBuilder
+import net.sergeych.lyng.bytecode.CmdBuilder
 import net.sergeych.lyng.bytecode.BytecodeCompiler
 import net.sergeych.lyng.bytecode.BytecodeConst
-import net.sergeych.lyng.bytecode.BytecodeVm
+import net.sergeych.lyng.bytecode.CmdVm
 import net.sergeych.lyng.bytecode.Opcode
 import net.sergeych.lyng.obj.BinaryOpRef
 import net.sergeych.lyng.obj.BinOp
@@ -45,10 +45,10 @@ import net.sergeych.lyng.obj.toLong
 import kotlin.test.Test
 import kotlin.test.assertEquals
 
-class BytecodeVmTest {
+class CmdVmTest {
     @Test
     fun addsIntConstants() = kotlinx.coroutines.test.runTest {
-        val builder = BytecodeBuilder()
+        val builder = CmdBuilder()
         val k0 = builder.addConst(BytecodeConst.IntVal(2))
         val k1 = builder.addConst(BytecodeConst.IntVal(3))
         builder.emit(Opcode.CONST_INT, k0, 0)
@@ -56,7 +56,7 @@ class BytecodeVmTest {
         builder.emit(Opcode.ADD_INT, 0, 1, 2)
         builder.emit(Opcode.RET, 2)
         val fn = builder.build("addInts", localCount = 3)
-        val result = BytecodeVm().execute(fn, Scope(), emptyList())
+        val result = CmdVm().execute(fn, Scope(), emptyList())
         assertEquals(5, result.toInt())
     }
 
@@ -80,7 +80,7 @@ class BytecodeVmTest {
         )
         val ifStmt = IfStatement(cond, thenStmt, elseStmt, net.sergeych.lyng.Pos.builtIn)
         val fn = BytecodeCompiler().compileStatement("ifTest", ifStmt) ?: error("bytecode compile failed")
-        val result = BytecodeVm().execute(fn, Scope(), emptyList())
+        val result = CmdVm().execute(fn, Scope(), emptyList())
         assertEquals(10, result.toInt())
     }
 
@@ -104,7 +104,7 @@ class BytecodeVmTest {
                 error("bytecode compile failed for ifNoElse")
             }
         }!!
-        val result = BytecodeVm().execute(fn, Scope(), emptyList())
+        val result = CmdVm().execute(fn, Scope(), emptyList())
         assertEquals(ObjVoid, result)
     }
 
@@ -120,7 +120,7 @@ class BytecodeVmTest {
             net.sergeych.lyng.Pos.builtIn
         )
         val fn = BytecodeCompiler().compileExpression("andShort", expr) ?: error("bytecode compile failed")
-        val result = BytecodeVm().execute(fn, Scope(), emptyList())
+        val result = CmdVm().execute(fn, Scope(), emptyList())
         assertEquals(false, result.toBool())
     }
 
@@ -136,7 +136,7 @@ class BytecodeVmTest {
             net.sergeych.lyng.Pos.builtIn
         )
         val fn = BytecodeCompiler().compileExpression("orShort", expr) ?: error("bytecode compile failed")
-        val result = BytecodeVm().execute(fn, Scope(), emptyList())
+        val result = CmdVm().execute(fn, Scope(), emptyList())
         assertEquals(true, result.toBool())
     }
 
@@ -151,7 +151,7 @@ class BytecodeVmTest {
             net.sergeych.lyng.Pos.builtIn
         )
         val fn = BytecodeCompiler().compileExpression("realPlus", expr) ?: error("bytecode compile failed")
-        val result = BytecodeVm().execute(fn, Scope(), emptyList())
+        val result = CmdVm().execute(fn, Scope(), emptyList())
         assertEquals(5.75, result.toDouble())
     }
 
@@ -163,7 +163,7 @@ class BytecodeVmTest {
                 scope.args[0].toLong() + scope.args[1].toLong()
             )
         }
-        val builder = BytecodeBuilder()
+        val builder = CmdBuilder()
         val fnId = builder.addConst(BytecodeConst.ObjRef(callable))
         val arg0 = builder.addConst(BytecodeConst.IntVal(2L))
         val arg1 = builder.addConst(BytecodeConst.IntVal(3L))
@@ -173,7 +173,7 @@ class BytecodeVmTest {
         builder.emit(Opcode.CALL_SLOT, 0, 1, 2, 3)
         builder.emit(Opcode.RET, 3)
         val fn = builder.build("callSlot", localCount = 4)
-        val result = BytecodeVm().execute(fn, Scope(), emptyList())
+        val result = CmdVm().execute(fn, Scope(), emptyList())
         assertEquals(5, result.toInt())
     }
 
@@ -188,7 +188,7 @@ class BytecodeVmTest {
             net.sergeych.lyng.Pos.builtIn
         )
         val ltFn = BytecodeCompiler().compileExpression("mixedLt", ltExpr) ?: error("bytecode compile failed")
-        val ltResult = BytecodeVm().execute(ltFn, Scope(), emptyList())
+        val ltResult = CmdVm().execute(ltFn, Scope(), emptyList())
         assertEquals(true, ltResult.toBool())
 
         val eqExpr = ExpressionStatement(
@@ -200,7 +200,7 @@ class BytecodeVmTest {
             net.sergeych.lyng.Pos.builtIn
         )
         val eqFn = BytecodeCompiler().compileExpression("mixedEq", eqExpr) ?: error("bytecode compile failed")
-        val eqResult = BytecodeVm().execute(eqFn, Scope(), emptyList())
+        val eqResult = CmdVm().execute(eqFn, Scope(), emptyList())
         assertEquals(true, eqResult.toBool())
     }
 
@@ -224,7 +224,7 @@ class BytecodeVmTest {
         )
         val expr = ExpressionStatement(callRef, Pos.builtIn)
         val fn = BytecodeCompiler().compileExpression("tailBlockArgs", expr) ?: error("bytecode compile failed")
-        val result = BytecodeVm().execute(fn, Scope(), emptyList())
+        val result = CmdVm().execute(fn, Scope(), emptyList())
         assertEquals(true, result.toBool())
     }
 
@@ -249,7 +249,7 @@ class BytecodeVmTest {
         )
         val expr = ExpressionStatement(callRef, Pos.builtIn)
         val fn = BytecodeCompiler().compileExpression("namedArgs", expr) ?: error("bytecode compile failed")
-        val result = BytecodeVm().execute(fn, Scope(), emptyList())
+        val result = CmdVm().execute(fn, Scope(), emptyList())
         assertEquals(5, result.toInt())
     }
 
@@ -275,7 +275,7 @@ class BytecodeVmTest {
         )
         val expr = ExpressionStatement(callRef, Pos.builtIn)
         val fn = BytecodeCompiler().compileExpression("splatArgs", expr) ?: error("bytecode compile failed")
-        val result = BytecodeVm().execute(fn, Scope(), emptyList())
+        val result = CmdVm().execute(fn, Scope(), emptyList())
         assertEquals(3, result.toInt())
     }
 
@@ -290,7 +290,7 @@ class BytecodeVmTest {
             net.sergeych.lyng.Pos.builtIn
         )
         val fn = BytecodeCompiler().compileExpression("mixedPlus", expr) ?: error("bytecode compile failed")
-        val result = BytecodeVm().execute(fn, Scope(), emptyList())
+        val result = CmdVm().execute(fn, Scope(), emptyList())
         assertEquals(5.5, result.toDouble())
     }
 
@@ -305,13 +305,13 @@ class BytecodeVmTest {
             net.sergeych.lyng.Pos.builtIn
         )
         val fn = BytecodeCompiler().compileExpression("mixedNeq", expr) ?: error("bytecode compile failed")
-        val result = BytecodeVm().execute(fn, Scope(), emptyList())
+        val result = CmdVm().execute(fn, Scope(), emptyList())
         assertEquals(true, result.toBool())
     }
 
     @Test
     fun localSlotTypeTrackingEnablesArithmetic() = kotlinx.coroutines.test.runTest {
-        val slotRef = LocalSlotRef("a", 0, 0, true, false, net.sergeych.lyng.Pos.builtIn)
+        val slotRef = LocalSlotRef("a", 0, 0, 0, true, false, net.sergeych.lyng.Pos.builtIn)
         val assign = AssignRef(
             slotRef,
             ConstRef(ObjInt.of(2).asReadonly),
@@ -327,13 +327,13 @@ class BytecodeVmTest {
         )
         val fn = BytecodeCompiler().compileExpression("localSlotAdd", expr) ?: error("bytecode compile failed")
         val scope = Scope().apply { applySlotPlan(mapOf("a" to 0)) }
-        val result = BytecodeVm().execute(fn, scope, emptyList())
+        val result = CmdVm().execute(fn, scope, emptyList())
         assertEquals(4, result.toInt())
     }
 
     @Test
     fun parentScopeSlotAccessWorks() = kotlinx.coroutines.test.runTest {
-        val parentRef = LocalSlotRef("a", 0, 1, true, false, net.sergeych.lyng.Pos.builtIn)
+        val parentRef = LocalSlotRef("a", 0, 1, 0, true, false, net.sergeych.lyng.Pos.builtIn)
         val expr = ExpressionStatement(
             BinaryOpRef(
                 BinOp.PLUS,
@@ -348,7 +348,7 @@ class BytecodeVmTest {
             setSlotValue(0, ObjInt.of(3))
         }
         val child = Scope(parent)
-        val result = BytecodeVm().execute(fn, child, emptyList())
+        val result = CmdVm().execute(fn, child, emptyList())
         assertEquals(5, result.toInt())
     }
 
@@ -363,7 +363,7 @@ class BytecodeVmTest {
             net.sergeych.lyng.Pos.builtIn
         )
         val fn = BytecodeCompiler().compileExpression("objEq", expr) ?: error("bytecode compile failed")
-        val result = BytecodeVm().execute(fn, Scope(), emptyList())
+        val result = CmdVm().execute(fn, Scope(), emptyList())
         assertEquals(true, result.toBool())
     }
 
@@ -379,7 +379,7 @@ class BytecodeVmTest {
             net.sergeych.lyng.Pos.builtIn
         )
         val eqFn = BytecodeCompiler().compileExpression("objRefEq", eqExpr) ?: error("bytecode compile failed")
-        val eqResult = BytecodeVm().execute(eqFn, Scope(), emptyList())
+        val eqResult = CmdVm().execute(eqFn, Scope(), emptyList())
         assertEquals(true, eqResult.toBool())
 
         val neqExpr = ExpressionStatement(
@@ -391,7 +391,7 @@ class BytecodeVmTest {
             net.sergeych.lyng.Pos.builtIn
         )
         val neqFn = BytecodeCompiler().compileExpression("objRefNeq", neqExpr) ?: error("bytecode compile failed")
-        val neqResult = BytecodeVm().execute(neqFn, Scope(), emptyList())
+        val neqResult = CmdVm().execute(neqFn, Scope(), emptyList())
         assertEquals(true, neqResult.toBool())
     }
 
@@ -406,7 +406,7 @@ class BytecodeVmTest {
             net.sergeych.lyng.Pos.builtIn
         )
         val ltFn = BytecodeCompiler().compileExpression("objLt", ltExpr) ?: error("bytecode compile failed")
-        val ltResult = BytecodeVm().execute(ltFn, Scope(), emptyList())
+        val ltResult = CmdVm().execute(ltFn, Scope(), emptyList())
         assertEquals(true, ltResult.toBool())
 
         val gteExpr = ExpressionStatement(
@@ -418,7 +418,7 @@ class BytecodeVmTest {
             net.sergeych.lyng.Pos.builtIn
         )
         val gteFn = BytecodeCompiler().compileExpression("objGte", gteExpr) ?: error("bytecode compile failed")
-        val gteResult = BytecodeVm().execute(gteFn, Scope(), emptyList())
+        val gteResult = CmdVm().execute(gteFn, Scope(), emptyList())
         assertEquals(true, gteResult.toBool())
     }
 
@@ -433,7 +433,7 @@ class BytecodeVmTest {
             net.sergeych.lyng.Pos.builtIn
         )
         val fn = BytecodeCompiler().compileExpression("objPlus", expr) ?: error("bytecode compile failed")
-        val result = BytecodeVm().execute(fn, Scope(), emptyList())
+        val result = CmdVm().execute(fn, Scope(), emptyList())
         assertEquals("ab", (result as ObjString).value)
     }
 }

lynglib/src/commonTest/kotlin/NestedRangeBenchmarkTest.kt

@@ -21,7 +21,7 @@ import net.sergeych.lyng.Compiler
 import net.sergeych.lyng.ForInStatement
 import net.sergeych.lyng.Script
 import net.sergeych.lyng.Statement
-import net.sergeych.lyng.bytecode.BytecodeDisassembler
+import net.sergeych.lyng.bytecode.CmdDisassembler
 import net.sergeych.lyng.bytecode.BytecodeStatement
 import net.sergeych.lyng.obj.ObjInt
 import kotlin.time.TimeSource
@@ -56,8 +56,11 @@ class NestedRangeBenchmarkTest {
         val scope = Script.newScope()
         scope.eval(script)
         val fnDisasm = scope.disassembleSymbol("naiveCountHappyNumbers")
-        println("[DEBUG_LOG] [BENCH] nested-happy function naiveCountHappyNumbers bytecode:\n$fnDisasm")
+        println("[DEBUG_LOG] [BENCH] nested-happy function naiveCountHappyNumbers cmd:\n$fnDisasm")
+        runMode(scope)
+    }
 
+    private suspend fun runMode(scope: net.sergeych.lyng.Scope) {
         val start = TimeSource.Monotonic.markNow()
         val result = scope.eval("naiveCountHappyNumbers()") as ObjInt
         val elapsedMs = start.elapsedNow().inWholeMilliseconds
@@ -83,13 +86,13 @@ class NestedRangeBenchmarkTest {
                 "$slotName@${fn.scopeSlotDepths[idx]}:${fn.scopeSlotIndices[idx]}"
             }
             println("[DEBUG_LOG] [BENCH] nested-happy slots depth=$depth: ${slots.joinToString(", ")}")
-            val disasm = BytecodeDisassembler.disassemble(fn)
+            val disasm = CmdDisassembler.disassemble(fn)
-            println("[DEBUG_LOG] [BENCH] nested-happy bytecode depth=$depth:\n$disasm")
+            println("[DEBUG_LOG] [BENCH] nested-happy cmd depth=$depth:\n$disasm")
             current = original.body
             depth += 1
         }
         if (depth == 1) {
-            println("[DEBUG_LOG] [BENCH] nested-happy bytecode: <not found>")
+            println("[DEBUG_LOG] [BENCH] nested-happy cmd: <not found>")
         }
     }
 

lynglib/src/commonTest/kotlin/ScriptTest.kt

@@ -2822,10 +2822,10 @@ class ScriptTest {
                         x
                     }
                     
-                    (1..100).map { launch { dosomething() } }.forEach { 
+                    (1..50).map { launch { dosomething() } }.forEach { 
                         assertEquals(5050, it.await())
                      }
-                     assertEquals( 100, ac.getCounter() )
+                     assertEquals( 50, ac.getCounter() )
                     
                 """.trimIndent()
                 )

lynglib/src/jsMain/kotlin/net/sergeych/lyng/PerfDefaults.js.kt

@@ -43,4 +43,4 @@ actual object PerfDefaults {
     actual val ARG_SMALL_ARITY_12: Boolean = false
     actual val INDEX_PIC_SIZE_4: Boolean = false
     actual val RANGE_FAST_ITER: Boolean = false
-}
+}

lynglib/src/jsMain/kotlin/net/sergeych/lyng/bytecode/CmdCallSiteCacheJs.kt

@@ -16,10 +16,10 @@
 
 package net.sergeych.lyng.bytecode
 
-internal actual object BytecodeCallSiteCache {
+internal actual object CmdCallSiteCache {
-    private val cache = mutableMapOf<BytecodeFunction, MutableMap<Int, MethodCallSite>>()
+    private val cache = mutableMapOf<CmdFunction, MutableMap<Int, MethodCallSite>>()
 
-    actual fun methodCallSites(fn: BytecodeFunction): MutableMap<Int, MethodCallSite> {
+    actual fun methodCallSites(fn: CmdFunction): MutableMap<Int, MethodCallSite> {
         return cache.getOrPut(fn) { mutableMapOf() }
     }
 }

lynglib/src/jvmMain/kotlin/net/sergeych/lyng/PerfDefaults.jvm.kt

@@ -49,4 +49,4 @@ actual object PerfDefaults {
 
     // Range fast-iteration (experimental; OFF by default)
     actual val RANGE_FAST_ITER: Boolean = true
-}
+}

lynglib/src/jvmMain/kotlin/net/sergeych/lyng/bytecode/CmdCallSiteCacheJvm.kt

@@ -18,12 +18,12 @@ package net.sergeych.lyng.bytecode
 
 import java.util.IdentityHashMap
 
-internal actual object BytecodeCallSiteCache {
+internal actual object CmdCallSiteCache {
     private val cache = ThreadLocal.withInitial {
-        IdentityHashMap<BytecodeFunction, MutableMap<Int, MethodCallSite>>()
+        IdentityHashMap<CmdFunction, MutableMap<Int, MethodCallSite>>()
     }
 
-    actual fun methodCallSites(fn: BytecodeFunction): MutableMap<Int, MethodCallSite> {
+    actual fun methodCallSites(fn: CmdFunction): MutableMap<Int, MethodCallSite> {
         val map = cache.get()
         return map.getOrPut(fn) { mutableMapOf() }
     }

lynglib/src/nativeMain/kotlin/net/sergeych/lyng/PerfDefaults.native.kt

@@ -43,4 +43,4 @@ actual object PerfDefaults {
     actual val ARG_SMALL_ARITY_12: Boolean = false
     actual val INDEX_PIC_SIZE_4: Boolean = false
     actual val RANGE_FAST_ITER: Boolean = false
-}
+}

lynglib/src/nativeMain/kotlin/net/sergeych/lyng/bytecode/CmdCallSiteCacheNative.kt

@@ -17,10 +17,10 @@
 package net.sergeych.lyng.bytecode
 
 @kotlin.native.concurrent.ThreadLocal
-internal actual object BytecodeCallSiteCache {
+internal actual object CmdCallSiteCache {
-    private val cache = mutableMapOf<BytecodeFunction, MutableMap<Int, MethodCallSite>>()
+    private val cache = mutableMapOf<CmdFunction, MutableMap<Int, MethodCallSite>>()
 
-    actual fun methodCallSites(fn: BytecodeFunction): MutableMap<Int, MethodCallSite> {
+    actual fun methodCallSites(fn: CmdFunction): MutableMap<Int, MethodCallSite> {
         return cache.getOrPut(fn) { mutableMapOf() }
     }
 }

lynglib/src/wasmJsMain/kotlin/net/sergeych/lyng/PerfDefaults.wasmJs.kt

@@ -43,4 +43,4 @@ actual object PerfDefaults {
     actual val ARG_SMALL_ARITY_12: Boolean = false
     actual val INDEX_PIC_SIZE_4: Boolean = false
     actual val RANGE_FAST_ITER: Boolean = false
-}
+}

lynglib/src/wasmJsMain/kotlin/net/sergeych/lyng/bytecode/CmdCallSiteCacheWasm.kt

@@ -16,10 +16,10 @@
 
 package net.sergeych.lyng.bytecode
 
-internal actual object BytecodeCallSiteCache {
+internal actual object CmdCallSiteCache {
-    private val cache = mutableMapOf<BytecodeFunction, MutableMap<Int, MethodCallSite>>()
+    private val cache = mutableMapOf<CmdFunction, MutableMap<Int, MethodCallSite>>()
 
-    actual fun methodCallSites(fn: BytecodeFunction): MutableMap<Int, MethodCallSite> {
+    actual fun methodCallSites(fn: CmdFunction): MutableMap<Int, MethodCallSite> {
         return cache.getOrPut(fn) { mutableMapOf() }
     }
 }