Add branches support in interpreter

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/interpreter/IrInterpreter.kt

@@ -44,14 +44,18 @@ class IrInterpreter : IrElementVisitor<State, Frame> {
             is IrGetField -> visitGetField(element, data)
             is IrGetValue -> visitGetValue(element, data)
             is IrConst<*> -> visitConst(element, data)
+            is IrWhen -> visitWhen(element, data)
             else -> TODO("${element.javaClass} not supported")
         }
     }
 
     override fun visitCall(expression: IrCall, data: Frame): State {
-        val newFrame = InterpreterFrame(convertValueParameters(expression, data))
+        val newFrame = InterpreterFrame() // it is important firstly to add receiver, then arguments
+        val valueParameters = convertValueParameters(expression, data)
+
         if (expression.symbol.owner.isFakeOverride) {
             expression.dispatchReceiver?.accept(this, data)?.let { newFrame.addVar(it) }
+            newFrame.addAll(valueParameters)
             return calculateOverridden(expression.symbol, newFrame)
         }
 
@@ -60,6 +64,7 @@ class IrInterpreter : IrElementVisitor<State, Frame> {
         val extensionReceiver = expression.extensionReceiver?.accept(this, data)
             ?.setDescriptor(expression.symbol.descriptor.extensionReceiverParameter!!)
         (dispatchReceiver ?: extensionReceiver)?.also { newFrame.addVar(it) }
+        newFrame.addAll(valueParameters)
 
         return if (expression.getBody() == null) {
             calculateBuiltIns(expression.symbol.descriptor, newFrame).toIrConst(expression).toPrimitive()
@@ -100,13 +105,14 @@ class IrInterpreter : IrElementVisitor<State, Frame> {
     }
 
     private fun visitStatements(statements: List<IrStatement>, data: Frame): State {
-        statements.forEach {
-            when (it) {
-                is IrReturn -> return it.accept(this, data)
-                else -> it.accept(this, data)
+        statements.forEachIndexed { index, statement ->
+            when {
+                statement is IrReturn || index == statements.lastIndex -> return statement.accept(this, data)
+                else -> statement.accept(this, data)
             }
         }
 
+        // unreachable state; method must return inside forEach
         return unit
     }
 
@@ -147,4 +153,13 @@ class IrInterpreter : IrElementVisitor<State, Frame> {
         }
         return unit
     }
+
+    override fun visitWhen(expression: IrWhen, data: Frame): State {
+        expression.branches.forEach {
+            if ((it.condition.accept(this, data) as? Primitive<*>)?.getIrConst()?.value == true) {
+                return it.result.accept(this, data)
+            }
+        }
+        return unit
+    }
 }

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/interpreter/Utils.kt

@@ -53,7 +53,7 @@ fun calculateBuiltIns(descriptor: FunctionDescriptor, frame: Frame): Any {
         2 -> {
             val function = binaryFunctions[signature]
                 ?: throw NoSuchMethodException("For given function $signature there is no entry in binary map")
-            function.invoke(argsValues[1], argsValues[0])
+            function.invoke(argsValues[0], argsValues[1])
         }
         else -> throw UnsupportedOperationException("Unsupported number of arguments")
     }

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/interpreter/stack/Frame.kt

@@ -10,6 +10,7 @@ import java.util.NoSuchElementException
 
 interface Frame {
     fun addVar(state: State)
+    fun addAll(states: List<State>)
     fun getVar(descriptor: DeclarationDescriptor): State
     fun getAll(): List<State>
     fun contains(descriptor: DeclarationDescriptor): Boolean
@@ -20,6 +21,10 @@ class InterpreterFrame(val pool: MutableList<State> = mutableListOf()) : Frame {
         pool.add(state)
     }
 
+    override fun addAll(states: List<State>) {
+        pool.addAll(states)
+    }
+
     override fun getVar(descriptor: DeclarationDescriptor): State {
         return pool.firstOrNull { it.isTypeOf(descriptor) }
             ?: throw NoSuchElementException("Frame pool doesn't contains variable with descriptor $descriptor")