Add bytecode if support and test

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

@@ -2965,25 +2965,10 @@ class Compiler(
         return if (t2.type == Token.Type.ID && t2.value == "else") {
             val elseBody =
                 parseStatement() ?: throw ScriptError(pos, "Bad else statement: expected statement")
-            return object : Statement() {
+            IfStatement(condition, ifBody, elseBody, start)
-                override val pos: Pos = start
-                override suspend fun execute(scope: Scope): Obj {
-                    return if (condition.execute(scope).toBool())
-                        ifBody.execute(scope)
-                    else
-                        elseBody.execute(scope)
-                }
-            }
         } else {
             cc.previous()
-            object : Statement() {
+            IfStatement(condition, ifBody, null, start)
-                override val pos: Pos = start
-                override suspend fun execute(scope: Scope): Obj {
-                    if (condition.execute(scope).toBool())
-                        return ifBody.execute(scope)
-                    return ObjVoid
-                }
-            }
         }
     }
 

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

@@ -17,10 +17,19 @@
 package net.sergeych.lyng.bytecode
 
 class BytecodeBuilder {
-    data class Instr(val op: Opcode, val operands: IntArray)
+    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
 
     fun addConst(c: BytecodeConst): Int {
         constPool += c
@@ -28,7 +37,17 @@ class BytecodeBuilder {
     }
 
     fun emit(op: Opcode, vararg operands: Int) {
-        instructions += Instr(op, operands.copyOf())
+        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 build(name: String, localCount: Int): BytecodeFunction {
@@ -39,15 +58,32 @@ class BytecodeBuilder {
         }
         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.toInt() and 0xFF)
+            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 v = ins.operands[i]
+                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)
@@ -115,6 +151,16 @@ class BytecodeBuilder {
         }
     }
 
+    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,

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

@@ -17,12 +17,21 @@
 package net.sergeych.lyng.bytecode
 
 import net.sergeych.lyng.ExpressionStatement
+import net.sergeych.lyng.IfStatement
 import net.sergeych.lyng.obj.*
 
 class BytecodeCompiler {
     private val builder = BytecodeBuilder()
     private var nextSlot = 0
 
+    fun compileStatement(name: String, stmt: net.sergeych.lyng.Statement): BytecodeFunction? {
+        return when (stmt) {
+            is ExpressionStatement -> compileExpression(name, stmt)
+            is net.sergeych.lyng.IfStatement -> compileIf(name, stmt)
+            else -> null
+        }
+    }
+
     fun compileExpression(name: String, stmt: ExpressionStatement): BytecodeFunction? {
         val value = compileRef(stmt.ref) ?: return null
         builder.emit(Opcode.RET, value.slot)
@@ -241,27 +250,61 @@ class BytecodeCompiler {
         return CompiledValue(slot, value.type)
     }
 
-    private fun refSlot(ref: LocalSlotRef): Int = ref.slot
+    private fun compileIf(name: String, stmt: IfStatement): BytecodeFunction? {
+        val conditionStmt = stmt.condition as? ExpressionStatement ?: return null
+        val condValue = compileRef(conditionStmt.ref) ?: return null
+        if (condValue.type != SlotType.BOOL) return null
 
-    private fun refDepth(ref: LocalSlotRef): Int = refDepthAccessor(ref)
+        val resultSlot = allocSlot()
+        val elseLabel = builder.label()
+        val endLabel = builder.label()
 
-    private fun binaryLeft(ref: BinaryOpRef): ObjRef = binaryLeftAccessor(ref)
+        builder.emit(
-    private fun binaryRight(ref: BinaryOpRef): ObjRef = binaryRightAccessor(ref)
+            Opcode.JMP_IF_FALSE,
-    private fun binaryOp(ref: BinaryOpRef): BinOp = binaryOpAccessor(ref)
+            listOf(BytecodeBuilder.Operand.IntVal(condValue.slot), BytecodeBuilder.Operand.LabelRef(elseLabel))
+        )
+        val thenValue = compileStatementValue(stmt.ifBody) ?: return null
+        emitMove(thenValue, resultSlot)
+        builder.emit(Opcode.JMP, listOf(BytecodeBuilder.Operand.LabelRef(endLabel)))
 
-    private fun unaryOperand(ref: UnaryOpRef): ObjRef = unaryOperandAccessor(ref)
+        builder.mark(elseLabel)
-    private fun unaryOp(ref: UnaryOpRef): UnaryOp = unaryOpAccessor(ref)
+        if (stmt.elseBody != null) {
-
+            val elseValue = compileStatementValue(stmt.elseBody) ?: return null
-    private fun assignTarget(ref: AssignRef): LocalSlotRef? = assignTargetAccessor(ref)
+            emitMove(elseValue, resultSlot)
-    private fun assignValue(ref: AssignRef): ObjRef = assignValueAccessor(ref)
+        } else {
-
+            val id = builder.addConst(BytecodeConst.ObjRef(ObjVoid))
-    // Accessor helpers to avoid exposing fields directly in ObjRef classes.
+            builder.emit(Opcode.CONST_OBJ, id, resultSlot)
-    private fun refDepthAccessor(ref: LocalSlotRef): Int = ref.depth
+        }
-    private fun binaryLeftAccessor(ref: BinaryOpRef): ObjRef = ref.left
+
-    private fun binaryRightAccessor(ref: BinaryOpRef): ObjRef = ref.right
+        builder.mark(endLabel)
-    private fun binaryOpAccessor(ref: BinaryOpRef): BinOp = ref.op
+        builder.emit(Opcode.RET, resultSlot)
-    private fun unaryOperandAccessor(ref: UnaryOpRef): ObjRef = ref.a
+        val localCount = maxOf(nextSlot, resultSlot + 1)
-    private fun unaryOpAccessor(ref: UnaryOpRef): UnaryOp = ref.op
+        return builder.build(name, localCount)
-    private fun assignTargetAccessor(ref: AssignRef): LocalSlotRef? = ref.target as? LocalSlotRef
+    }
-    private fun assignValueAccessor(ref: AssignRef): ObjRef = ref.value
+
+    private fun compileStatementValue(stmt: net.sergeych.lyng.Statement): CompiledValue? {
+        return when (stmt) {
+            is ExpressionStatement -> compileRef(stmt.ref)
+            else -> null
+        }
+    }
+
+    private fun emitMove(value: CompiledValue, dstSlot: Int) {
+        when (value.type) {
+            SlotType.INT -> builder.emit(Opcode.MOVE_INT, value.slot, dstSlot)
+            SlotType.REAL -> builder.emit(Opcode.MOVE_REAL, value.slot, dstSlot)
+            SlotType.BOOL -> builder.emit(Opcode.MOVE_BOOL, value.slot, dstSlot)
+            else -> builder.emit(Opcode.MOVE_OBJ, value.slot, dstSlot)
+        }
+    }
+
+    private fun refSlot(ref: LocalSlotRef): Int = ref.slot
+    private fun refDepth(ref: LocalSlotRef): Int = ref.depth
+    private fun binaryLeft(ref: BinaryOpRef): ObjRef = ref.left
+    private fun binaryRight(ref: BinaryOpRef): ObjRef = ref.right
+    private fun binaryOp(ref: BinaryOpRef): BinOp = ref.op
+    private fun unaryOperand(ref: UnaryOpRef): ObjRef = ref.a
+    private fun unaryOp(ref: UnaryOpRef): UnaryOp = ref.op
+    private fun assignTarget(ref: AssignRef): LocalSlotRef? = ref.target as? LocalSlotRef
+    private fun assignValue(ref: AssignRef): ObjRef = ref.value
 }

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

@@ -109,6 +109,37 @@ class BytecodeVm {
                     ip += fn.slotWidth
                     frame.setInt(dst, frame.getInt(a) + frame.getInt(b))
                 }
+                Opcode.CMP_LT_INT -> {
+                    val a = decoder.readSlot(code, ip)
+                    ip += fn.slotWidth
+                    val b = decoder.readSlot(code, ip)
+                    ip += fn.slotWidth
+                    val dst = decoder.readSlot(code, ip)
+                    ip += fn.slotWidth
+                    frame.setBool(dst, frame.getInt(a) < frame.getInt(b))
+                }
+                Opcode.CMP_EQ_INT -> {
+                    val a = decoder.readSlot(code, ip)
+                    ip += fn.slotWidth
+                    val b = decoder.readSlot(code, ip)
+                    ip += fn.slotWidth
+                    val dst = decoder.readSlot(code, ip)
+                    ip += fn.slotWidth
+                    frame.setBool(dst, frame.getInt(a) == frame.getInt(b))
+                }
+                Opcode.JMP -> {
+                    val target = decoder.readIp(code, ip, fn.ipWidth)
+                    ip = target
+                }
+                Opcode.JMP_IF_FALSE -> {
+                    val cond = decoder.readSlot(code, ip)
+                    ip += fn.slotWidth
+                    val target = decoder.readIp(code, ip, fn.ipWidth)
+                    ip += fn.ipWidth
+                    if (!frame.getBool(cond)) {
+                        ip = target
+                    }
+                }
                 Opcode.RET -> {
                     val slot = decoder.readSlot(code, ip)
                     return slotToObj(frame, slot)

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

@@ -20,6 +20,7 @@ package net.sergeych.lyng
 import net.sergeych.lyng.obj.Obj
 import net.sergeych.lyng.obj.ObjClass
 import net.sergeych.lyng.obj.ObjVoid
+import net.sergeych.lyng.obj.toBool
 
 fun String.toSource(name: String = "eval"): Source = Source(name, this)
 
@@ -63,6 +64,21 @@ abstract class Statement(
 
 }
 
+class IfStatement(
+    val condition: Statement,
+    val ifBody: Statement,
+    val elseBody: Statement?,
+    override val pos: Pos,
+) : Statement() {
+    override suspend fun execute(scope: Scope): Obj {
+        return if (condition.execute(scope).toBool()) {
+            ifBody.execute(scope)
+        } else {
+            elseBody?.execute(scope) ?: ObjVoid
+        }
+    }
+}
+
 class ExpressionStatement(
     val ref: net.sergeych.lyng.obj.ObjRef,
     override val pos: Pos

lynglib/src/commonTest/kotlin/BytecodeVmTest.kt

@@ -14,11 +14,18 @@
  * limitations under the License.
  */
 
+import net.sergeych.lyng.ExpressionStatement
+import net.sergeych.lyng.IfStatement
 import net.sergeych.lyng.Scope
 import net.sergeych.lyng.bytecode.BytecodeBuilder
+import net.sergeych.lyng.bytecode.BytecodeCompiler
 import net.sergeych.lyng.bytecode.BytecodeConst
 import net.sergeych.lyng.bytecode.BytecodeVm
 import net.sergeych.lyng.bytecode.Opcode
+import net.sergeych.lyng.obj.BinaryOpRef
+import net.sergeych.lyng.obj.BinOp
+import net.sergeych.lyng.obj.ConstRef
+import net.sergeych.lyng.obj.ObjInt
 import net.sergeych.lyng.obj.toInt
 import kotlin.test.Test
 import kotlin.test.assertEquals
@@ -37,4 +44,28 @@ class BytecodeVmTest {
         val result = BytecodeVm().execute(fn, Scope(), emptyList())
         assertEquals(5, result.toInt())
     }
+
+    @Test
+    fun ifExpressionReturnsThenValue() = kotlinx.coroutines.test.runTest {
+        val cond = ExpressionStatement(
+            BinaryOpRef(
+                BinOp.LT,
+                ConstRef(ObjInt.of(2).asReadonly),
+                ConstRef(ObjInt.of(3).asReadonly),
+            ),
+            net.sergeych.lyng.Pos.builtIn
+        )
+        val thenStmt = ExpressionStatement(
+            ConstRef(ObjInt.of(10).asReadonly),
+            net.sergeych.lyng.Pos.builtIn
+        )
+        val elseStmt = ExpressionStatement(
+            ConstRef(ObjInt.of(20).asReadonly),
+            net.sergeych.lyng.Pos.builtIn
+        )
+        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())
+        assertEquals(10, result.toInt())
+    }
 }