For loops lowering improvements (#2191)

* Reduce descriptors and KotlinType usage * Add Array.indices lowering. * Added IrCallMatcher and IrFunctionMatcher * Added benchmarks
2018-10-18 18:01:09 +07:00
parent 70e6b71134
commit 4c61454ea5
10 changed files with 891 additions and 560 deletions
@@ -13,6 +13,7 @@ import org.jetbrains.kotlin.backend.konan.lower.FinallyBlocksLowering
 import org.jetbrains.kotlin.backend.konan.lower.InitializersLowering
 import org.jetbrains.kotlin.backend.konan.lower.LateinitLowering
 import org.jetbrains.kotlin.backend.konan.lower.SharedVariablesLowering
+import org.jetbrains.kotlin.backend.konan.lower.loops.ForLoopsLowering
 import org.jetbrains.kotlin.ir.declarations.IrFile
 import org.jetbrains.kotlin.ir.declarations.IrModuleFragment
 import org.jetbrains.kotlin.ir.util.checkDeclarationParents
@@ -36,6 +36,7 @@ import org.jetbrains.kotlin.ir.util.*
 import org.jetbrains.kotlin.name.ClassId
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.Name
+import org.jetbrains.kotlin.resolve.scopes.MemberScope
 import org.jetbrains.kotlin.types.KotlinType
 import org.jetbrains.kotlin.types.TypeUtils
 import kotlin.properties.Delegates
@@ -289,15 +290,14 @@ internal class KonanSymbols(context: Context, val symbolTable: SymbolTable, val
            { findArrayExtension(it.descriptor, "contentHashCode") }
    )

-    fun findArrayExtension(descriptor: ClassDescriptor, name: String): IrSimpleFunctionSymbol {
+    private fun findArrayExtension(descriptor: ClassDescriptor, name: String): IrSimpleFunctionSymbol {
        val functionDescriptor = builtInsPackage("kotlin", "collections")
                .getContributedFunctions(Name.identifier(name), NoLookupLocation.FROM_BACKEND)
                .singleOrNull {
                    it.valueParameters.isEmpty()
                            && it.extensionReceiverParameter?.type?.constructor?.declarationDescriptor == descriptor
                            && !it.isExpect
-                }
-                ?: throw Error(descriptor.toString())
+                } ?: error(descriptor.toString())
        return symbolTable.referenceSimpleFunction(functionDescriptor)
    }

@@ -319,6 +319,15 @@ internal class KonanSymbols(context: Context, val symbolTable: SymbolTable, val
            .getContributedFunctions(Name.identifier("set"), NoLookupLocation.FROM_BACKEND)
            .single().let { symbolTable.referenceSimpleFunction(it) }

+    val arraySize = arrays.associateBy(
+            { it },
+            { it.descriptor.unsubstitutedMemberScope
+                    .getContributedVariables(Name.identifier("size"), NoLookupLocation.FROM_BACKEND)
+                    .single().let { symbolTable.referenceSimpleFunction(it.getter!!) } }
+    )
+
+
+
    val valuesForEnum = symbolTable.referenceSimpleFunction(
            context.getInternalFunctions("valuesForEnum").single())

@@ -1,557 +0,0 @@
-/*
- * Copyright 2010-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
- * that can be found in the LICENSE file.
- */
-
-package org.jetbrains.kotlin.backend.konan.lower
-
-import org.jetbrains.kotlin.backend.common.FileLoweringPass
-import org.jetbrains.kotlin.backend.common.IrElementTransformerVoidWithContext
-import org.jetbrains.kotlin.backend.common.lower.DeclarationIrBuilder
-import org.jetbrains.kotlin.backend.common.lower.createIrBuilder
-import org.jetbrains.kotlin.backend.common.lower.irIfThen
-import org.jetbrains.kotlin.backend.konan.Context
-import org.jetbrains.kotlin.ir.util.isSimpleTypeWithQuestionMark
-import org.jetbrains.kotlin.builtins.KotlinBuiltIns
-import org.jetbrains.kotlin.descriptors.SimpleFunctionDescriptor
-import org.jetbrains.kotlin.incremental.components.NoLookupLocation
-import org.jetbrains.kotlin.ir.IrElement
-import org.jetbrains.kotlin.ir.IrStatement
-import org.jetbrains.kotlin.ir.builders.*
-import org.jetbrains.kotlin.ir.declarations.IrDeclarationOrigin
-import org.jetbrains.kotlin.ir.declarations.IrFile
-import org.jetbrains.kotlin.ir.declarations.IrVariable
-import org.jetbrains.kotlin.ir.expressions.*
-import org.jetbrains.kotlin.ir.expressions.impl.*
-import org.jetbrains.kotlin.ir.symbols.IrClassSymbol
-import org.jetbrains.kotlin.ir.symbols.IrFunctionSymbol
-import org.jetbrains.kotlin.ir.symbols.IrVariableSymbol
-import org.jetbrains.kotlin.ir.types.makeNotNull
-import org.jetbrains.kotlin.ir.types.toKotlinType
-import org.jetbrains.kotlin.ir.util.*
-import org.jetbrains.kotlin.ir.visitors.*
-import org.jetbrains.kotlin.name.FqName
-import org.jetbrains.kotlin.name.Name
-import org.jetbrains.kotlin.types.KotlinType
-import org.jetbrains.kotlin.types.SimpleType
-import org.jetbrains.kotlin.types.typeUtil.isSubtypeOf
-import org.jetbrains.kotlin.types.typeUtil.makeNotNullable
-import org.jetbrains.kotlin.types.typeUtil.replaceArgumentsWithStarProjections
-import org.jetbrains.kotlin.util.OperatorNameConventions
-
-/**  This lowering pass optimizes range-based for loops. */
-internal class ForLoopsLowering(val context: Context) : FileLoweringPass {
-    override fun lower(irFile: IrFile) {
-        val transformer = ForLoopsTransformer(context)
-        // Lower loops
-        irFile.transformChildrenVoid(transformer)
-
-        // Update references in break/continue.
-        irFile.transformChildrenVoid(object: IrElementTransformerVoid() {
-            override fun visitBreakContinue(jump: IrBreakContinue): IrExpression {
-                transformer.oldLoopToNewLoop[jump.loop]?.let { jump.loop = it }
-                return jump
-            }
-        })
-    }
-}
-
-private class ForLoopsTransformer(val context: Context) : IrElementTransformerVoidWithContext() {
-
-    private val symbols = context.ir.symbols
-    private val iteratorToLoopInfo = mutableMapOf<IrVariableSymbol, ForLoopInfo>()
-    internal val oldLoopToNewLoop = mutableMapOf<IrLoop, IrLoop>()
-
-    private val iteratorType = symbols.iterator.descriptor.defaultType.replaceArgumentsWithStarProjections()
-
-    private val scopeOwnerSymbol
-        get() = currentScope!!.scope.scopeOwnerSymbol
-
-    private val progressionElementClasses: List<IrClassSymbol> = mutableListOf(symbols.char).apply {
-        addAll(symbols.integerClasses)
-    }
-
-    private val progressionElementClassesTypes: List<SimpleType> = mutableListOf<SimpleType>().apply {
-        progressionElementClasses.mapTo(this) { it.descriptor.defaultType }
-    }
-
-    private val progressionElementClassesNullableTypes: List<SimpleType> = mutableListOf<SimpleType>().apply {
-        progressionElementClassesTypes.mapTo(this) { it.makeNullableAsSpecified(true) }
-    }
-
-    //region Symbols for progression building functions ================================================================
-    private fun getProgressionBuildingMethods(name: String): Set<IrFunctionSymbol> =
-            getMethodsForProgressionElements(name) {
-                it.valueParameters.size == 1 && it.valueParameters[0].type in progressionElementClassesTypes
-            }
-
-    private fun getProgressionBuildingExtensions(name: String, pkg: FqName): Set<IrFunctionSymbol> =
-            getExtensionsForProgressionElements(name, pkg) {
-                it.extensionReceiverParameter?.type in progressionElementClassesTypes &&
-                it.valueParameters.size == 1 &&
-                it.valueParameters[0].type in progressionElementClassesTypes
-            }
-
-    private fun getMethodsForProgressionElements(name: String,
-                                                 filter: (SimpleFunctionDescriptor) -> Boolean): Set<IrFunctionSymbol> =
-            mutableSetOf<IrFunctionSymbol>().apply {
-                progressionElementClasses.flatMapTo(this) { receiver ->
-                    receiver.descriptor.unsubstitutedMemberScope
-                            .getContributedFunctions(Name.identifier(name), NoLookupLocation.FROM_BACKEND)
-                            .filter(filter).map { symbols.symbolTable.referenceFunction(it) }
-                }
-            }
-
-    private fun getExtensionsForProgressionElements(name: String,
-                                                    pkg: FqName,
-                                                    filter: (SimpleFunctionDescriptor) -> Boolean): Set<IrFunctionSymbol> =
-            mutableSetOf<IrFunctionSymbol>().apply {
-                progressionElementClasses.flatMapTo(this) { _ /* receiver */ ->
-                    context.builtIns.builtInsModule.getPackage(pkg).memberScope
-                            .getContributedFunctions(Name.identifier(name), NoLookupLocation.FROM_BACKEND)
-                            .filter(filter).map { symbols.symbolTable.referenceFunction(it) }
-                }
-            }
-
-    private val rangeToSymbols by lazy { getProgressionBuildingMethods("rangeTo") }
-    private val untilSymbols by lazy { getProgressionBuildingExtensions("until", FqName("kotlin.ranges")) }
-    private val downToSymbols by lazy { getProgressionBuildingExtensions("downTo", FqName("kotlin.ranges")) }
-    private val stepSymbols by lazy {
-        getExtensionsForProgressionElements("step", FqName("kotlin.ranges")) {
-            it.extensionReceiverParameter?.type in symbols.progressionClassesTypes &&
-                    it.valueParameters.size == 1 &&
-                    (KotlinBuiltIns.isLong(it.valueParameters[0].type) || KotlinBuiltIns.isInt(it.valueParameters[0].type))
-        }
-    }
-    //endregion
-
-    //region Util methods ==============================================================================================
-    private fun IrExpression.castIfNecessary(progressionType: ProgressionType): IrExpression {
-        val type = this.type.toKotlinType()
-        assert(type in progressionElementClassesTypes || type in progressionElementClassesNullableTypes)
-        return if (type == progressionType.elementType) {
-            this
-        } else {
-            val function = symbols.getFunction(progressionType.numberCastFunctionName, type)
-            IrCallImpl(startOffset, endOffset, function.owner.returnType, function)
-                    .apply { dispatchReceiver = this@castIfNecessary }
-        }
-    }
-
-    private fun DeclarationIrBuilder.ensureNotNullable(expression: IrExpression): IrExpression {
-        return if (expression.type.isSimpleTypeWithQuestionMark) {
-            irImplicitCast(expression, expression.type.makeNotNull())
-        } else {
-            expression
-        }
-    }
-
-    private fun IrExpression.unaryMinus(): IrExpression {
-        val unaryOperator = symbols.getUnaryOperator(OperatorNameConventions.UNARY_MINUS, type.toKotlinType())
-        return IrCallImpl(startOffset, endOffset, unaryOperator.owner.returnType, unaryOperator).apply {
-            dispatchReceiver = this@unaryMinus
-        }
-    }
-
-    private fun ProgressionInfo.defaultStep(startOffset: Int, endOffset: Int): IrExpression =
-        progressionType.elementType.let { type ->
-            val step = if (increasing) 1 else -1
-            when {
-                KotlinBuiltIns.isInt(type) || KotlinBuiltIns.isChar(type) ->
-                    IrConstImpl.int(startOffset, endOffset, context.irBuiltIns.intType, step)
-                KotlinBuiltIns.isLong(type) ->
-                    IrConstImpl.long(startOffset, endOffset, context.irBuiltIns.longType, step.toLong())
-                else -> throw IllegalArgumentException()
-            }
-        }
-
-    private fun IrConst<*>.isOne() =
-        when (kind) {
-            IrConstKind.Long -> value as Long == 1L
-            IrConstKind.Int  -> value as Int == 1
-            else -> false
-        }
-
-    // Used only by the assert.
-    private fun stepHasRightType(step: IrExpression, progressionType: ProgressionType) =
-            ((progressionType.isCharProgression() || progressionType.isIntProgression()) &&
-                    KotlinBuiltIns.isInt(step.type.toKotlinType().makeNotNullable())) ||
-            (progressionType.isLongProgression() &&
-                    KotlinBuiltIns.isLong(step.type.toKotlinType().makeNotNullable()))
-
-    private fun irCheckProgressionStep(progressionType: ProgressionType,
-                                       step: IrExpression): Pair<IrExpression, Boolean> {
-        if (step is IrConst<*> &&
-            ((step.kind == IrConstKind.Long && step.value as Long > 0) ||
-            (step.kind == IrConstKind.Int && step.value as Int > 0))) {
-            return step to !step.isOne()
-        }
-        // The frontend checks if the step has a right type (Long for LongProgression and Int for {Int/Char}Progression)
-        // so there is no need to cast it.
-        assert(stepHasRightType(step, progressionType))
-
-        val symbol = symbols.checkProgressionStep[step.type.toKotlinType().makeNotNullable()]
-                ?: throw IllegalArgumentException("Unknown progression element type: ${step.type}")
-        return IrCallImpl(step.startOffset, step.endOffset, symbol.owner.returnType, symbol).apply {
-            putValueArgument(0, step)
-        } to true
-    }
-
-    private fun irGetProgressionLast(progressionType: ProgressionType,
-                                     first: IrVariable,
-                                     lastExpression: IrExpression,
-                                     step: IrVariable): IrExpression {
-        val symbol = symbols.getProgressionLast[progressionType.elementType]
-                ?: throw IllegalArgumentException("Unknown progression element type: ${lastExpression.type}")
-        val startOffset = lastExpression.startOffset
-        val endOffset = lastExpression.endOffset
-        return IrCallImpl(startOffset, lastExpression.endOffset, symbol.owner.returnType, symbol).apply {
-            putValueArgument(0, IrGetValueImpl(startOffset, endOffset, first.type, first.symbol))
-            putValueArgument(1, lastExpression.castIfNecessary(progressionType))
-            putValueArgument(2, IrGetValueImpl(startOffset, endOffset, step.type, step.symbol))
-        }
-    }
-    //endregion
-
-    //region Util classes ==============================================================================================
-    // TODO: Replace with a cast when such support is added in the boxing lowering.
-    private data class ProgressionType(val elementType: KotlinType, val numberCastFunctionName: Name) {
-        fun isIntProgression()  = KotlinBuiltIns.isInt(elementType)
-        fun isLongProgression() = KotlinBuiltIns.isLong(elementType)
-        fun isCharProgression() = KotlinBuiltIns.isChar(elementType)
-    }
-
-    private data class ProgressionInfo(
-            val progressionType: ProgressionType,
-            val first: IrExpression,
-            val bound: IrExpression,
-            val step: IrExpression? = null,
-            val increasing: Boolean = true,
-            var needLastCalculation: Boolean = false,
-            val closed: Boolean = true)
-
-    /** Contains information about variables used in the loop. */
-    private data class ForLoopInfo(
-            val progressionInfo: ProgressionInfo,
-            val inductionVariable: IrVariable,
-            val bound: IrVariable,
-            val last: IrVariable,
-            val step: IrVariable,
-            var loopVariable: IrVariable? = null)
-
-    private inner class ProgressionInfoBuilder : IrElementVisitor<ProgressionInfo?, Nothing?> {
-
-        val INT_PROGRESSION = ProgressionType(context.builtIns.intType, Name.identifier("toInt"))
-        val LONG_PROGRESSION = ProgressionType(context.builtIns.longType, Name.identifier("toLong"))
-        val CHAR_PROGRESSION = ProgressionType(context.builtIns.charType, Name.identifier("toChar"))
-
-        private fun buildRangeTo(expression: IrCall, progressionType: ProgressionType) =
-                ProgressionInfo(progressionType,
-                        expression.dispatchReceiver!!,
-                        expression.getValueArgument(0)!!)
-
-        private fun buildUntil(expression: IrCall, progressionType: ProgressionType): ProgressionInfo =
-                ProgressionInfo(progressionType,
-                        expression.extensionReceiver!!,
-                        expression.getValueArgument(0)!!,
-                        closed = false)
-
-        private fun buildDownTo(expression: IrCall, progressionType: ProgressionType) =
-                ProgressionInfo(progressionType,
-                        expression.extensionReceiver!!,
-                        expression.getValueArgument(0)!!,
-                        increasing = false)
-
-        private fun buildStep(expression: IrCall, progressionType: ProgressionType) =
-                expression.extensionReceiver!!.accept(this, null)?.let {
-                    val newStep = expression.getValueArgument(0)!!
-                    val (newStepCheck, needBoundCalculation) = irCheckProgressionStep(progressionType, newStep)
-                    val step = when {
-                        it.step == null -> newStepCheck
-                        // There were step calls before. Just add our check in the container or create a new one.
-                        it.step is IrStatementContainer -> {
-                            it.step.statements.add(newStepCheck)
-                            it.step
-                        }
-                        else -> IrCompositeImpl(expression.startOffset, expression.endOffset, newStep.type).apply {
-                            statements.add(it.step)
-                            statements.add(newStepCheck)
-                        }
-                    }
-                    ProgressionInfo(progressionType, it.first, it.bound, step, it.increasing, needBoundCalculation, it.closed)
-                }
-
-        override fun visitElement(element: IrElement, data: Nothing?): ProgressionInfo? = null
-
-        override fun visitCall(expression: IrCall, data: Nothing?): ProgressionInfo? {
-            val type = expression.type.toKotlinType()
-            val progressionType = when {
-                type.isSubtypeOf(symbols.charProgression.descriptor.defaultType) -> CHAR_PROGRESSION
-                type.isSubtypeOf(symbols.intProgression.descriptor.defaultType) -> INT_PROGRESSION
-                type.isSubtypeOf(symbols.longProgression.descriptor.defaultType) -> LONG_PROGRESSION
-                else -> return null
-            }
-
-            // TODO: Process constructors and other factory functions.
-            return when (expression.symbol) {
-                in rangeToSymbols -> buildRangeTo(expression, progressionType)
-                in untilSymbols -> buildUntil(expression, progressionType)
-                in downToSymbols -> buildDownTo(expression, progressionType)
-                in stepSymbols -> buildStep(expression, progressionType)
-                else -> null
-            }
-        }
-    }
-    //endregion
-
-    //region Lowering ==================================================================================================
-    // Lower a loop header.
-    private fun processHeader(variable: IrVariable, initializer: IrCall): IrStatement? {
-        assert(variable.origin == IrDeclarationOrigin.FOR_LOOP_ITERATOR)
-        val symbol = variable.symbol
-        if (!variable.descriptor.type.isSubtypeOf(iteratorType)) {
-            return null
-        }
-        assert(symbol !in iteratorToLoopInfo)
-
-        val builder = context.createIrBuilder(scopeOwnerSymbol, variable.startOffset, variable.endOffset)
-        // Collect loop info and form the loop header composite.
-        val progressionInfo = initializer.dispatchReceiver?.accept(ProgressionInfoBuilder(), null) ?: return null
-
-        with(builder) {
-            with(progressionInfo) {
-                // Due to features of PSI2IR we can obtain nullable arguments here while actually
-                // they are non-nullable (the frontend takes care about this). So we need to cast them to non-nullable.
-                val statements = mutableListOf<IrStatement>()
-
-                /**
-                 * For this loop:
-                 * `for (i in a() .. b() step c() step d())`
-                 * We need to call functions in the following order: a, b, c, d.
-                 * So we call b() before step calculations and then call last element calculation function (if required).
-                 */
-                val inductionVariable = scope.createTemporaryVariable(first.castIfNecessary(progressionType),
-                        nameHint = "inductionVariable",
-                        isMutable = true,
-                        origin = IrDeclarationOrigin.FOR_LOOP_IMPLICIT_VARIABLE).also {
-                    statements.add(it)
-                }
-
-                val boundValue = scope.createTemporaryVariable(bound.castIfNecessary(progressionType),
-                        nameHint = "bound",
-                        origin = IrDeclarationOrigin.FOR_LOOP_IMPLICIT_VARIABLE)
-                        .also { statements.add(it) }
-
-
-                val stepExpression = (if (increasing) step else step?.unaryMinus()) ?: defaultStep(startOffset, endOffset)
-                val stepValue = scope.createTemporaryVariable(ensureNotNullable(stepExpression),
-                        nameHint = "step",
-                        origin = IrDeclarationOrigin.FOR_LOOP_IMPLICIT_VARIABLE).also {
-                    statements.add(it)
-                }
-
-                // Calculate the last element of the progression
-                // The last element can be:
-                //    boundValue, if step is 1 and the range is closed.
-                //    boundValue - 1, if step is 1 and the range is open.
-                //    getProgressionLast(inductionVariable, boundValue, step), if step != 1 and the range is closed.
-                //    getProgressionLast(inductionVariable, boundValue - 1, step), if step != 1 and the range is open.
-                var lastExpression: IrExpression? = null
-                if (!closed) {
-                    val decrementSymbol = symbols.getUnaryOperator(OperatorNameConventions.DEC, boundValue.descriptor.type)
-                    lastExpression = irCall(decrementSymbol.owner).apply {
-                        dispatchReceiver = irGet(boundValue)
-                    }
-                }
-                if (needLastCalculation) {
-                    lastExpression = irGetProgressionLast(progressionType,
-                            inductionVariable,
-                            lastExpression ?: irGet(boundValue),
-                            stepValue)
-                }
-                val lastValue = if (lastExpression != null) {
-                    scope.createTemporaryVariable(lastExpression,
-                            nameHint = "last",
-                            origin = IrDeclarationOrigin.FOR_LOOP_IMPLICIT_VARIABLE).also {
-                        statements.add(it)
-                    }
-                } else {
-                    boundValue
-                }
-
-                iteratorToLoopInfo[symbol] = ForLoopInfo(progressionInfo,
-                        inductionVariable,
-                        boundValue,
-                        lastValue,
-                        stepValue)
-
-                return IrCompositeImpl(startOffset, endOffset, context.irBuiltIns.unitType, null, statements)
-            }
-        }
-    }
-
-    // Lower getting a next induction variable value.
-    private fun processNext(variable: IrVariable, initializer: IrCall): IrExpression? {
-        assert(variable.origin == IrDeclarationOrigin.FOR_LOOP_VARIABLE
-                || variable.origin == IrDeclarationOrigin.FOR_LOOP_IMPLICIT_VARIABLE)
-        val irIteratorAccess = initializer.dispatchReceiver as? IrGetValue ?: throw AssertionError()
-        val forLoopInfo = iteratorToLoopInfo[irIteratorAccess.symbol] ?: return null  // If we didn't lower a corresponding header.
-        val builder = context.createIrBuilder(scopeOwnerSymbol, initializer.startOffset, initializer.endOffset)
-
-        val plusOperator = symbols.getBinaryOperator(
-                OperatorNameConventions.PLUS,
-                forLoopInfo.inductionVariable.descriptor.type,
-                forLoopInfo.step.descriptor.type
-        )
-        forLoopInfo.loopVariable = variable
-
-        with(builder) {
-            variable.initializer = irGet(forLoopInfo.inductionVariable)
-            val increment = irSetVar(forLoopInfo.inductionVariable,
-                    irCallOp(plusOperator.owner, irGet(forLoopInfo.inductionVariable), irGet(forLoopInfo.step)))
-            return IrCompositeImpl(variable.startOffset,
-                    variable.endOffset,
-                    context.irBuiltIns.unitType,
-                    IrStatementOrigin.FOR_LOOP_NEXT,
-                    listOf(variable, increment))
-        }
-    }
-
-    private fun DeclarationIrBuilder.buildMinValueCondition(forLoopInfo: ForLoopInfo): IrExpression {
-        // Condition for a corner case: for (i in a until Int.MIN_VALUE) {}.
-        // Check if forLoopInfo.bound > MIN_VALUE.
-        val progressionType = forLoopInfo.progressionInfo.progressionType
-        return irCall(context.irBuiltIns.greaterFunByOperandType[context.irBuiltIns.int]?.symbol!!).apply {
-            val minConst = when {
-                progressionType.isIntProgression() -> IrConstImpl
-                        .int(startOffset, endOffset, context.irBuiltIns.intType, Int.MIN_VALUE)
-                progressionType.isCharProgression() -> IrConstImpl
-                        .char(startOffset, endOffset, context.irBuiltIns.charType, 0.toChar())
-                progressionType.isLongProgression() -> IrConstImpl
-                        .long(startOffset, endOffset, context.irBuiltIns.longType, Long.MIN_VALUE)
-                else -> throw IllegalArgumentException("Unknown progression type")
-            }
-            val compareToCall = irCall(symbols.getBinaryOperator(OperatorNameConventions.COMPARE_TO,
-                    forLoopInfo.bound.descriptor.type,
-                    minConst.type.toKotlinType())).apply {
-                dispatchReceiver = irGet(forLoopInfo.bound)
-                putValueArgument(0, minConst)
-            }
-            putValueArgument(0, compareToCall)
-            putValueArgument(1, irInt(0))
-        }
-    }
-
-    // TODO: Eliminate the loop if we can prove that it will not be executed.
-    private fun DeclarationIrBuilder.buildEmptyCheck(loop: IrLoop, forLoopInfo: ForLoopInfo): IrExpression {
-        val builtIns = context.irBuiltIns
-        val increasing = forLoopInfo.progressionInfo.increasing
-        val comparingBuiltIn = if (increasing) builtIns.lessOrEqualFunByOperandType[builtIns.int]?.symbol
-        else builtIns.greaterOrEqualFunByOperandType[builtIns.int]?.symbol
-
-        // Check if inductionVariable <= last.
-        val compareTo = symbols.getBinaryOperator(OperatorNameConventions.COMPARE_TO,
-                forLoopInfo.inductionVariable.descriptor.type,
-                forLoopInfo.last.descriptor.type)
-
-        val check: IrExpression = irCall(comparingBuiltIn!!).apply {
-            putValueArgument(0, irCallOp(compareTo.owner, irGet(forLoopInfo.inductionVariable), irGet(forLoopInfo.last)))
-            putValueArgument(1, irInt(0))
-        }
-
-        // Process closed and open ranges in different manners.
-        return if (forLoopInfo.progressionInfo.closed) {
-            irIfThen(check, loop)   // if (inductionVariable <= last) { loop }
-        } else {
-            // Take into account a corner case: for (i in a until Int.MIN_VALUE) {}.
-            // if (inductionVariable <= last && bound > MIN_VALUE) { loop }
-            return irIfThen(check, irIfThen(buildMinValueCondition(forLoopInfo), loop))
-        }
-    }
-
-    private fun DeclarationIrBuilder.buildNewCondition(oldCondition: IrExpression): Pair<IrExpression, ForLoopInfo>? {
-        if (oldCondition !is IrCall || oldCondition.origin != IrStatementOrigin.FOR_LOOP_HAS_NEXT) {
-            return null
-        }
-
-        val irIteratorAccess = oldCondition.dispatchReceiver as? IrGetValue ?: throw AssertionError()
-        // Return null if we didn't lower a corresponding header.
-        val forLoopInfo = iteratorToLoopInfo[irIteratorAccess.symbol] ?: return null
-        assert(forLoopInfo.loopVariable != null)
-
-        return irCall(context.irBuiltIns.booleanNotSymbol).apply {
-            val eqeqCall = irCall(context.irBuiltIns.eqeqSymbol).apply {
-                putValueArgument(0, irGet(forLoopInfo.loopVariable!!))
-                putValueArgument(1, irGet(forLoopInfo.last))
-            }
-            putValueArgument(0, eqeqCall)
-        } to forLoopInfo
-    }
-
-    /**
-     * This loop
-     *
-     * for (i in first..last step foo) { ... }
-     *
-     * is represented in IR in such a manner:
-     *
-     * val it = (first..last step foo).iterator()
-     * while (it.hasNext()) {
-     *     val i = it.next()
-     *     ...
-     * }
-     *
-     * We transform it into the following loop:
-     *
-     * var it = first
-     * if (it <= last) {  // (it >= last if the progression is decreasing)
-     *     do {
-     *         val i = it++
-     *         ...
-     *     } while (i != last)
-     * }
-     */
-    // TODO:  Lower `for (i in a until b)` to loop with precondition: for (i = a; i < b; a++);
-    override fun visitWhileLoop(loop: IrWhileLoop): IrExpression {
-        if (loop.origin != IrStatementOrigin.FOR_LOOP_INNER_WHILE) {
-            return super.visitWhileLoop(loop)
-        }
-
-        with(context.createIrBuilder(scopeOwnerSymbol, loop.startOffset, loop.endOffset)) {
-            // Transform accesses to the old iterator (see visitVariable method). Store loopVariable in loopInfo.
-            // Replace not transparent containers with transparent ones (IrComposite)
-            val newBody = loop.body?.transform(this@ForLoopsTransformer, null)?.let {
-                if (it is IrContainerExpression && !it.isTransparentScope) {
-                    with(it) { IrCompositeImpl(startOffset, endOffset, type, origin, statements) }
-                } else {
-                    it
-                }
-            }
-            val (newCondition, forLoopInfo) = buildNewCondition(loop.condition) ?: return super.visitWhileLoop(loop)
-
-            val newLoop = IrDoWhileLoopImpl(loop.startOffset, loop.endOffset, loop.type, loop.origin).apply {
-                label = loop.label
-                condition = newCondition
-                body = newBody
-            }
-            oldLoopToNewLoop[loop] = newLoop
-            // Build a check for an empty progression before the loop.
-            return buildEmptyCheck(newLoop, forLoopInfo)
-        }
-    }
-
-    override fun visitVariable(declaration: IrVariable): IrStatement {
-        val initializer = declaration.initializer
-        if (initializer == null || initializer !is IrCall) {
-            return super.visitVariable(declaration)
-        }
-        val result = when (initializer.origin) {
-            IrStatementOrigin.FOR_LOOP_ITERATOR -> processHeader(declaration, initializer)
-            IrStatementOrigin.FOR_LOOP_NEXT -> processNext(declaration, initializer)
-            else -> null
-        }
-        return result ?: super.visitVariable(declaration)
-    }
-    //endregion
-}
-
@@ -0,0 +1,395 @@
+/*
+ * Copyright 2010-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
+ * that can be found in the LICENSE file.
+ */
+
+package org.jetbrains.kotlin.backend.konan.lower.loops
+
+import org.jetbrains.kotlin.backend.common.FileLoweringPass
+import org.jetbrains.kotlin.backend.common.IrElementTransformerVoidWithContext
+import org.jetbrains.kotlin.backend.common.lower.DeclarationIrBuilder
+import org.jetbrains.kotlin.backend.common.lower.createIrBuilder
+import org.jetbrains.kotlin.backend.common.lower.irIfThen
+import org.jetbrains.kotlin.backend.konan.Context
+import org.jetbrains.kotlin.backend.konan.irasdescriptors.isSubtypeOf
+import org.jetbrains.kotlin.backend.konan.irasdescriptors.typeWithStarProjections
+import org.jetbrains.kotlin.ir.util.isSimpleTypeWithQuestionMark
+import org.jetbrains.kotlin.ir.IrStatement
+import org.jetbrains.kotlin.ir.builders.*
+import org.jetbrains.kotlin.ir.declarations.IrDeclarationOrigin
+import org.jetbrains.kotlin.ir.declarations.IrFile
+import org.jetbrains.kotlin.ir.declarations.IrVariable
+import org.jetbrains.kotlin.ir.expressions.*
+import org.jetbrains.kotlin.ir.expressions.impl.*
+import org.jetbrains.kotlin.ir.symbols.IrVariableSymbol
+import org.jetbrains.kotlin.ir.types.*
+import org.jetbrains.kotlin.ir.util.*
+import org.jetbrains.kotlin.ir.visitors.*
+import org.jetbrains.kotlin.util.OperatorNameConventions
+
+/**  This lowering pass optimizes range-based for loops.
+ *
+ *   NB! not implemented yet.
+ *   Process `for (elem in array) { f(elem) }` construct first.
+ *   Replace with `for (i in array.indices) { f(array.get(i)) }`.
+ *
+ *   Next replace iteration over ranges (X.indices, a..b, etc.) with
+ *   simple while loop over primitive induction variable.
+ */
+internal class ForLoopsLowering(val context: Context) : FileLoweringPass {
+
+    private val progressionInfoBuilder = ProgressionInfoBuilder(context)
+
+    override fun lower(irFile: IrFile) {
+        val transformer = ForLoopsTransformer(context, progressionInfoBuilder)
+        // Lower loops
+        irFile.transformChildrenVoid(transformer)
+
+        // Update references in break/continue.
+        irFile.transformChildrenVoid(object: IrElementTransformerVoid() {
+            override fun visitBreakContinue(jump: IrBreakContinue): IrExpression {
+                transformer.oldLoopToNewLoop[jump.loop]?.let { jump.loop = it }
+                return jump
+            }
+        })
+    }
+}
+
+/** Contains information about variables used in the loop. */
+internal data class ForLoopInfo(
+        val progressionInfo: ProgressionInfo,
+        val inductionVariable: IrVariable,
+        val bound: IrVariable,
+        val last: IrVariable,
+        val step: IrVariable,
+        var loopVariable: IrVariable? = null)
+
+private fun ProgressionType.elementType(context: Context): IrType = when (this) {
+    ProgressionType.INT_PROGRESSION -> context.irBuiltIns.intType
+    ProgressionType.LONG_PROGRESSION -> context.irBuiltIns.longType
+    ProgressionType.CHAR_PROGRESSION -> context.irBuiltIns.charType
+}
+
+private class ForLoopsTransformer(val context: Context, val progressionInfoBuilder: ProgressionInfoBuilder) : IrElementTransformerVoidWithContext() {
+
+    private val symbols = context.ir.symbols
+    private val iteratorToLoopInfo = mutableMapOf<IrVariableSymbol, ForLoopInfo>()
+    internal val oldLoopToNewLoop = mutableMapOf<IrLoop, IrLoop>()
+
+    private val progressionElementClasses =
+            (symbols.integerClasses + symbols.char).toSet()
+
+    private val scopeOwnerSymbol
+        get() = currentScope!!.scope.scopeOwnerSymbol
+
+    //region Util methods ==============================================================================================
+    private fun IrExpression.castIfNecessary(progressionType: ProgressionType): IrExpression {
+        assert(type.classifierOrNull in progressionElementClasses)
+        return if (type.classifierOrNull == progressionType.elementType(context).classifierOrNull) {
+            this
+        } else {
+            val function = symbols.getFunction(progressionType.numberCastFunctionName, type.toKotlinType())
+            IrCallImpl(startOffset, endOffset, function.owner.returnType, function)
+                    .apply { dispatchReceiver = this@castIfNecessary }
+        }
+    }
+
+    private fun DeclarationIrBuilder.ensureNotNullable(expression: IrExpression): IrExpression {
+        return if (expression.type.isSimpleTypeWithQuestionMark) {
+            irImplicitCast(expression, expression.type.makeNotNull())
+        } else {
+            expression
+        }
+    }
+
+    private fun IrExpression.unaryMinus(): IrExpression {
+        val unaryOperator = symbols.getUnaryOperator(OperatorNameConventions.UNARY_MINUS, type.toKotlinType())
+        return IrCallImpl(startOffset, endOffset, unaryOperator.owner.returnType, unaryOperator).apply {
+            dispatchReceiver = this@unaryMinus
+        }
+    }
+
+    private fun ProgressionInfo.defaultStep(startOffset: Int, endOffset: Int): IrExpression {
+        val type = progressionType.elementType(context)
+        val step = if (increasing) 1 else -1
+        return when {
+            type.isInt() || type.isChar() ->
+                IrConstImpl.int(startOffset, endOffset, context.irBuiltIns.intType, step)
+            type.isLong() ->
+                IrConstImpl.long(startOffset, endOffset, context.irBuiltIns.longType, step.toLong())
+            else -> throw IllegalArgumentException()
+        }
+    }
+
+    private fun irGetProgressionLast(progressionType: ProgressionType,
+                                     first: IrVariable,
+                                     lastExpression: IrExpression,
+                                     step: IrVariable): IrExpression {
+        val symbol = symbols.getProgressionLast[progressionType.elementType(context).toKotlinType()]
+                ?: throw IllegalArgumentException("No `getProgressionLast` for type ${step.type} ${lastExpression.type}")
+        val startOffset = lastExpression.startOffset
+        val endOffset = lastExpression.endOffset
+        return IrCallImpl(startOffset, lastExpression.endOffset, symbol.owner.returnType, symbol).apply {
+            putValueArgument(0, IrGetValueImpl(startOffset, endOffset, first.type, first.symbol))
+            putValueArgument(1, lastExpression.castIfNecessary(progressionType))
+            putValueArgument(2, IrGetValueImpl(startOffset, endOffset, step.type, step.symbol))
+        }
+    }
+    //endregion
+
+    //region Lowering ==================================================================================================
+    // Lower a loop header.
+    private fun processHeader(variable: IrVariable, initializer: IrCall): IrStatement? {
+        assert(variable.origin == IrDeclarationOrigin.FOR_LOOP_ITERATOR)
+        val symbol = variable.symbol
+        val iteratorType = symbols.iterator.typeWithStarProjections
+
+        if (!variable.type.isSubtypeOf(iteratorType)) {
+            return null
+        }
+        assert(symbol !in iteratorToLoopInfo)
+
+        val builder = context.createIrBuilder(scopeOwnerSymbol, variable.startOffset, variable.endOffset)
+        // Collect loop info and form the loop header composite.
+        val progressionInfo = initializer.dispatchReceiver?.accept(progressionInfoBuilder, null)
+                ?: return null
+
+        with(builder) {
+            with(progressionInfo) {
+                // Due to features of PSI2IR we can obtain nullable arguments here while actually
+                // they are non-nullable (the frontend takes care about this). So we need to cast them to non-nullable.
+                val statements = mutableListOf<IrStatement>()
+
+                /**
+                 * For this loop:
+                 * `for (i in a() .. b() step c() step d())`
+                 * We need to call functions in the following order: a, b, c, d.
+                 * So we call b() before step calculations and then call last element calculation function (if required).
+                 */
+                val inductionVariable = scope.createTemporaryVariable(first.castIfNecessary(progressionType),
+                        nameHint = "inductionVariable",
+                        isMutable = true,
+                        origin = IrDeclarationOrigin.FOR_LOOP_IMPLICIT_VARIABLE).also {
+                    statements.add(it)
+                }
+
+                val boundValue = scope.createTemporaryVariable(ensureNotNullable(bound.castIfNecessary(progressionType)),
+                        nameHint = "bound",
+                        origin = IrDeclarationOrigin.FOR_LOOP_IMPLICIT_VARIABLE)
+                        .also { statements.add(it) }
+
+                val stepExpression = if (step != null) {
+                    if (increasing) step else step.unaryMinus()
+                } else {
+                    defaultStep(startOffset, endOffset)
+                }
+
+                val stepValue = scope.createTemporaryVariable(ensureNotNullable(stepExpression),
+                        nameHint = "step",
+                        origin = IrDeclarationOrigin.FOR_LOOP_IMPLICIT_VARIABLE).also {
+                    statements.add(it)
+                }
+
+                // Calculate the last element of the progression
+                // The last element can be:
+                //    boundValue, if step is 1 and the range is closed.
+                //    boundValue - 1, if step is 1 and the range is open.
+                //    getProgressionLast(inductionVariable, boundValue, step), if step != 1 and the range is closed.
+                //    getProgressionLast(inductionVariable, boundValue - 1, step), if step != 1 and the range is open.
+                var lastExpression: IrExpression = if (!closed) {
+                    val decrementSymbol = symbols.getUnaryOperator(OperatorNameConventions.DEC, boundValue.type.toKotlinType())
+                    irCall(decrementSymbol.owner).apply {
+                        dispatchReceiver = irGet(boundValue)
+                    }
+                } else {
+                    irGet(boundValue)
+                }
+                if (needLastCalculation) {
+                    lastExpression = irGetProgressionLast(progressionType,
+                            inductionVariable,
+                            lastExpression,
+                            stepValue)
+                }
+
+                val lastValue = scope.createTemporaryVariable(lastExpression,
+                        nameHint = "last",
+                        origin = IrDeclarationOrigin.FOR_LOOP_IMPLICIT_VARIABLE).also {
+                    statements.add(it)
+                }
+
+                iteratorToLoopInfo[symbol] = ForLoopInfo(progressionInfo,
+                        inductionVariable,
+                        boundValue,
+                        lastValue,
+                        stepValue)
+
+                return IrCompositeImpl(startOffset, endOffset, context.irBuiltIns.unitType, null, statements)
+            }
+        }
+    }
+
+    // Lower getting a next induction variable value.
+    private fun processNext(variable: IrVariable, initializer: IrCall): IrExpression? {
+        assert(variable.origin == IrDeclarationOrigin.FOR_LOOP_VARIABLE
+                || variable.origin == IrDeclarationOrigin.FOR_LOOP_IMPLICIT_VARIABLE)
+        val irIteratorAccess = initializer.dispatchReceiver as? IrGetValue ?: throw AssertionError()
+        val forLoopInfo = iteratorToLoopInfo[irIteratorAccess.symbol] ?: return null  // If we didn't lower a corresponding header.
+        val builder = context.createIrBuilder(scopeOwnerSymbol, initializer.startOffset, initializer.endOffset)
+
+        val plusOperator = symbols.getBinaryOperator(
+                OperatorNameConventions.PLUS,
+                forLoopInfo.inductionVariable.type.toKotlinType(),
+                forLoopInfo.step.type.toKotlinType()
+        )
+        forLoopInfo.loopVariable = variable
+
+        with(builder) {
+            variable.initializer = irGet(forLoopInfo.inductionVariable)
+            val increment = irSetVar(forLoopInfo.inductionVariable,
+                    irCallOp(plusOperator.owner, irGet(forLoopInfo.inductionVariable), irGet(forLoopInfo.step)))
+            return IrCompositeImpl(variable.startOffset,
+                    variable.endOffset,
+                    context.irBuiltIns.unitType,
+                    IrStatementOrigin.FOR_LOOP_NEXT,
+                    listOf(variable, increment))
+        }
+    }
+
+    private fun DeclarationIrBuilder.buildMinValueCondition(forLoopInfo: ForLoopInfo): IrExpression {
+        // Condition for a corner case: for (i in a until Int.MIN_VALUE) {}.
+        // Check if forLoopInfo.bound > MIN_VALUE.
+        val progressionType = forLoopInfo.progressionInfo.progressionType
+        val irBuiltIns = context.irBuiltIns
+        val minConst = when (progressionType) {
+            ProgressionType.INT_PROGRESSION -> IrConstImpl
+                    .int(startOffset, endOffset, irBuiltIns.intType, Int.MIN_VALUE)
+            ProgressionType.CHAR_PROGRESSION -> IrConstImpl
+                    .char(startOffset, endOffset, irBuiltIns.charType, 0.toChar())
+            ProgressionType.LONG_PROGRESSION -> IrConstImpl
+                    .long(startOffset, endOffset, irBuiltIns.longType, Long.MIN_VALUE)
+        }
+        val compareTo = symbols.getBinaryOperator(OperatorNameConventions.COMPARE_TO,
+                forLoopInfo.bound.type.toKotlinType(),
+                minConst.type.toKotlinType())
+        return irCall(irBuiltIns.greaterFunByOperandType[irBuiltIns.int]?.symbol!!).apply {
+            val compareToCall = irCall(compareTo).apply {
+                dispatchReceiver = irGet(forLoopInfo.bound)
+                putValueArgument(0, minConst)
+            }
+            putValueArgument(0, compareToCall)
+            putValueArgument(1, irInt(0))
+        }
+    }
+
+    // TODO: Eliminate the loop if we can prove that it will not be executed.
+    private fun DeclarationIrBuilder.buildEmptinessCheck(loop: IrLoop, forLoopInfo: ForLoopInfo): IrExpression {
+        val builtIns = context.irBuiltIns
+        val increasing = forLoopInfo.progressionInfo.increasing
+        val comparingBuiltIn = if (increasing) builtIns.lessOrEqualFunByOperandType[builtIns.int]?.symbol
+        else builtIns.greaterOrEqualFunByOperandType[builtIns.int]?.symbol
+
+        // Check if inductionVariable <= last.
+        val compareTo = symbols.getBinaryOperator(OperatorNameConventions.COMPARE_TO,
+                forLoopInfo.inductionVariable.type.toKotlinType(),
+                forLoopInfo.last.type.toKotlinType())
+
+        val check: IrExpression = irCall(comparingBuiltIn!!).apply {
+            putValueArgument(0, irCallOp(compareTo.owner, irGet(forLoopInfo.inductionVariable), irGet(forLoopInfo.last)))
+            putValueArgument(1, irInt(0))
+        }
+
+        // Process closed and open ranges in different manners.
+        return if (forLoopInfo.progressionInfo.closed) {
+            irIfThen(check, loop)   // if (inductionVariable <= last) { loop }
+        } else {
+            // Take into account a corner case: for (i in a until Int.MIN_VALUE) {}.
+            // if (inductionVariable <= last && bound > MIN_VALUE) { loop }
+            irIfThen(check, irIfThen(buildMinValueCondition(forLoopInfo), loop))
+        }
+    }
+
+    private fun DeclarationIrBuilder.buildNewCondition(oldCondition: IrExpression): Pair<IrExpression, ForLoopInfo>? {
+        if (oldCondition !is IrCall || oldCondition.origin != IrStatementOrigin.FOR_LOOP_HAS_NEXT) {
+            return null
+        }
+
+        val irIteratorAccess = oldCondition.dispatchReceiver as? IrGetValue ?: throw AssertionError()
+        // Return null if we didn't lower a corresponding header.
+        val forLoopInfo = iteratorToLoopInfo[irIteratorAccess.symbol] ?: return null
+        assert(forLoopInfo.loopVariable != null)
+
+        return irCall(context.irBuiltIns.booleanNotSymbol).apply {
+            val eqeqCall = irCall(context.irBuiltIns.eqeqSymbol).apply {
+                putValueArgument(0, irGet(forLoopInfo.loopVariable!!))
+                putValueArgument(1, irGet(forLoopInfo.last))
+            }
+            putValueArgument(0, eqeqCall)
+        } to forLoopInfo
+    }
+
+    /**
+     * This loop
+     *
+     * for (i in first..last step foo) { ... }
+     *
+     * is represented in IR in such a manner:
+     *
+     * val it = (first..last step foo).iterator()
+     * while (it.hasNext()) {
+     *     val i = it.next()
+     *     ...
+     * }
+     *
+     * We transform it into the following loop:
+     *
+     * var it = first
+     * if (it <= last) {  // (it >= last if the progression is decreasing)
+     *     do {
+     *         val i = it++
+     *         ...
+     *     } while (i != last)
+     * }
+     */
+    // TODO:  Lower `for (i in a until b)` to loop with precondition: for (i = a; i < b; a++);
+    override fun visitWhileLoop(loop: IrWhileLoop): IrExpression {
+        if (loop.origin != IrStatementOrigin.FOR_LOOP_INNER_WHILE) {
+            return super.visitWhileLoop(loop)
+        }
+
+        with(context.createIrBuilder(scopeOwnerSymbol, loop.startOffset, loop.endOffset)) {
+            // Transform accesses to the old iterator (see visitVariable method). Store loopVariable in loopInfo.
+            // Replace not transparent containers with transparent ones (IrComposite)
+            val newBody = loop.body?.transform(this@ForLoopsTransformer, null)?.let {
+                if (it is IrContainerExpression && !it.isTransparentScope) {
+                    IrCompositeImpl(startOffset, endOffset, it.type, it.origin, it.statements)
+                } else {
+                    it
+                }
+            }
+            val (newCondition, forLoopInfo) = buildNewCondition(loop.condition) ?: return super.visitWhileLoop(loop)
+
+            val newLoop = IrDoWhileLoopImpl(loop.startOffset, loop.endOffset, loop.type, loop.origin).apply {
+                label = loop.label
+                condition = newCondition
+                body = newBody
+            }
+            oldLoopToNewLoop[loop] = newLoop
+            // Build a check for an empty progression before the loop.
+            return buildEmptinessCheck(newLoop, forLoopInfo)
+        }
+    }
+
+    override fun visitVariable(declaration: IrVariable): IrStatement {
+        val initializer = declaration.initializer
+        if (initializer == null || initializer !is IrCall) {
+            return super.visitVariable(declaration)
+        }
+        val result = when (initializer.origin) {
+            IrStatementOrigin.FOR_LOOP_ITERATOR -> processHeader(declaration, initializer)
+            IrStatementOrigin.FOR_LOOP_NEXT -> processNext(declaration, initializer)
+            else -> null
+        }
+        return result ?: super.visitVariable(declaration)
+    }
+    //endregion
+}
@@ -0,0 +1,147 @@
+package org.jetbrains.kotlin.backend.konan.lower.loops
+
+import org.jetbrains.kotlin.backend.common.lower.createIrBuilder
+import org.jetbrains.kotlin.backend.konan.Context
+import org.jetbrains.kotlin.backend.konan.ir.KonanSymbols
+import org.jetbrains.kotlin.backend.konan.lower.matchers.IrCallMatcher
+import org.jetbrains.kotlin.backend.konan.lower.matchers.SimpleCalleeMatcher
+import org.jetbrains.kotlin.backend.konan.lower.matchers.createIrCallMatcher
+import org.jetbrains.kotlin.backend.konan.lower.matchers.singleArgumentExtension
+import org.jetbrains.kotlin.ir.builders.irCall
+import org.jetbrains.kotlin.ir.expressions.*
+import org.jetbrains.kotlin.ir.expressions.impl.IrCallImpl
+import org.jetbrains.kotlin.ir.expressions.impl.IrConstImpl
+import org.jetbrains.kotlin.ir.symbols.IrClassSymbol
+import org.jetbrains.kotlin.ir.types.*
+import org.jetbrains.kotlin.ir.visitors.IrElementVisitor
+import org.jetbrains.kotlin.name.FqName
+import org.jetbrains.kotlin.name.Name
+
+internal class RangeToHandler(val progressionElementClasses: Collection<IrClassSymbol>) : ProgressionHandler {
+    override val matcher = SimpleCalleeMatcher {
+        dispatchReceiver { it != null && it.type.classifierOrNull in progressionElementClasses }
+        fqName { it.pathSegments().last() == Name.identifier("rangeTo") }
+        parameterCount { it == 1 }
+        parameter(0) { it.type.classifierOrNull in progressionElementClasses }
+    }
+
+    override fun build(call: IrCall, progressionType: ProgressionType) =
+            ProgressionInfo(progressionType, call.dispatchReceiver!!, call.getValueArgument(0)!!)
+}
+
+internal class DownToHandler(val progressionElementClasses: Collection<IrClassSymbol>) : ProgressionHandler {
+    override val matcher = SimpleCalleeMatcher {
+        singleArgumentExtension(FqName("kotlin.ranges.downTo"), progressionElementClasses)
+        parameter(0) { it.type.classifierOrNull in progressionElementClasses }
+    }
+
+    override fun build(call: IrCall, progressionType: ProgressionType): ProgressionInfo? =
+            ProgressionInfo(progressionType,
+                    call.extensionReceiver!!,
+                    call.getValueArgument(0)!!,
+                    increasing = false)
+}
+
+internal class UntilHandler(val progressionElementClasses: Collection<IrClassSymbol>) : ProgressionHandler {
+    override val matcher = SimpleCalleeMatcher {
+        singleArgumentExtension(FqName("kotlin.ranges.until"), progressionElementClasses)
+        parameter(0) { it.type.classifierOrNull in progressionElementClasses }
+    }
+
+    override fun build(call: IrCall, progressionType: ProgressionType): ProgressionInfo? =
+            ProgressionInfo(progressionType,
+                    call.extensionReceiver!!,
+                    call.getValueArgument(0)!!,
+                    closed = false)
+}
+
+internal class IndicesHandler(val context: Context) : ProgressionHandler {
+
+    private val symbols = context.ir.symbols
+
+    private val supportedArrays = symbols.primitiveArrays.values + symbols.array
+
+    override val matcher = createIrCallMatcher {
+        callee {
+            fqName { it == FqName("kotlin.collections.<get-indices>") }
+            parameterCount { it == 0 }
+        }
+        extensionReceiver { it != null && it.type.classifierOrNull in supportedArrays }
+    }
+
+    override fun build(call: IrCall, progressionType: ProgressionType): ProgressionInfo? {
+        val int0 = IrConstImpl.int(call.startOffset, call.endOffset, context.irBuiltIns.intType, 0)
+
+        val bound = with(context.createIrBuilder(call.symbol, call.startOffset, call.endOffset)) {
+            val clazz = call.extensionReceiver!!.type.classifierOrFail
+            val symbol = symbols.arraySize[clazz]!!
+            irCall(symbol).apply {
+                dispatchReceiver = call.extensionReceiver
+            }
+        }
+        return ProgressionInfo(progressionType, int0, bound, closed = false)
+    }
+}
+
+internal class StepHandler(context: Context, val visitor: IrElementVisitor<ProgressionInfo?, Nothing?>) : ProgressionHandler {
+    private val symbols = context.ir.symbols
+
+    override val matcher: IrCallMatcher = SimpleCalleeMatcher {
+        singleArgumentExtension(FqName("kotlin.ranges.step"), symbols.progressionClasses)
+        parameter(0) { it.type.isInt() || it.type.isLong() }
+    }
+
+    override fun build(call: IrCall, progressionType: ProgressionType): ProgressionInfo? {
+        val nestedInfo = call.extensionReceiver!!.accept(visitor, null)
+                ?: return null
+
+        // Due to KT-27607 nested non-default steps could lead to incorrect behaviour.
+        // So disable optimization of such rare cases for now.
+        if (nestedInfo.step != null) {
+            return null
+        }
+
+        val newStep = call.getValueArgument(0)!!
+        val (newStepCheck, needBoundCalculation) = irCheckProgressionStep(symbols, progressionType, newStep)
+        return ProgressionInfo(
+                progressionType,
+                nestedInfo.first,
+                nestedInfo.bound,
+                newStepCheck, nestedInfo.increasing,
+                needBoundCalculation,
+                nestedInfo.closed)
+    }
+
+    private fun IrConst<*>.stepIsOne() = when (kind) {
+        IrConstKind.Long -> value as Long == 1L
+        IrConstKind.Int -> value as Int == 1
+        else -> false
+    }
+
+    private fun IrExpression.isPositiveConst() = this is IrConst<*> &&
+            ((kind == IrConstKind.Long && value as Long > 0) || (kind == IrConstKind.Int && value as Int > 0))
+
+    // Used only by the assert.
+    private fun stepHasRightType(step: IrExpression, progressionType: ProgressionType) = when (progressionType) {
+
+        ProgressionType.CHAR_PROGRESSION,
+        ProgressionType.INT_PROGRESSION -> step.type.makeNotNull().isInt()
+
+        ProgressionType.LONG_PROGRESSION -> step.type.makeNotNull().isLong()
+    }
+
+    private fun irCheckProgressionStep(symbols: KonanSymbols, progressionType: ProgressionType, step: IrExpression) =
+            if (step.isPositiveConst()) {
+                step to !(step as IrConst<*>).stepIsOne()
+            } else {
+                // The frontend checks if the step has a right type (Long for LongProgression and Int for {Int/Char}Progression)
+                // so there is no need to cast it.
+                assert(stepHasRightType(step, progressionType))
+
+                val symbol = symbols.checkProgressionStep[step.type.makeNotNull().toKotlinType()]
+                        ?: throw IllegalArgumentException("No `checkProgressionStep` for type ${step.type}")
+                IrCallImpl(step.startOffset, step.endOffset, symbol.owner.returnType, symbol).apply {
+                    putValueArgument(0, step)
+                } to true
+            }
+}
@@ -0,0 +1,70 @@
+package org.jetbrains.kotlin.backend.konan.lower.loops
+
+import org.jetbrains.kotlin.backend.konan.Context
+import org.jetbrains.kotlin.backend.konan.irasdescriptors.isSubtypeOf
+import org.jetbrains.kotlin.backend.konan.lower.matchers.*
+import org.jetbrains.kotlin.ir.IrElement
+import org.jetbrains.kotlin.ir.expressions.*
+import org.jetbrains.kotlin.ir.types.*
+import org.jetbrains.kotlin.ir.util.defaultType
+import org.jetbrains.kotlin.ir.visitors.IrElementVisitor
+import org.jetbrains.kotlin.name.Name
+import org.jetbrains.kotlin.utils.addToStdlib.firstNotNullResult
+
+enum class ProgressionType(val numberCastFunctionName: Name) {
+    INT_PROGRESSION(Name.identifier("toInt")),
+    LONG_PROGRESSION(Name.identifier("toLong")),
+    CHAR_PROGRESSION(Name.identifier("toChar"));
+}
+
+internal data class ProgressionInfo(
+        val progressionType: ProgressionType,
+        val first: IrExpression,
+        val bound: IrExpression,
+        val step: IrExpression? = null,
+        val increasing: Boolean = true,
+        var needLastCalculation: Boolean = false,
+        val closed: Boolean = true)
+
+internal interface ProgressionHandler {
+    val matcher: IrCallMatcher
+
+    fun build(call: IrCall, progressionType: ProgressionType): ProgressionInfo?
+
+    fun handle(irCall: IrCall, progressionType: ProgressionType) = if (matcher(irCall)) {
+        build(irCall, progressionType)
+    } else {
+        null
+    }
+}
+
+internal class ProgressionInfoBuilder(val context: Context) : IrElementVisitor<ProgressionInfo?, Nothing?> {
+
+    private val symbols = context.ir.symbols
+
+    private val progressionElementClasses = symbols.integerClasses + symbols.char
+
+    private val handlers = listOf(
+            IndicesHandler(context),
+            UntilHandler(progressionElementClasses),
+            DownToHandler(progressionElementClasses),
+            StepHandler(context, this),
+            RangeToHandler(progressionElementClasses)
+    )
+
+    private fun IrType.getProgressionType(): ProgressionType? = when {
+        isSubtypeOf(symbols.charProgression.owner.defaultType) -> ProgressionType.CHAR_PROGRESSION
+        isSubtypeOf(symbols.intProgression.owner.defaultType) -> ProgressionType.INT_PROGRESSION
+        isSubtypeOf(symbols.longProgression.owner.defaultType) -> ProgressionType.LONG_PROGRESSION
+        else -> null
+    }
+
+    override fun visitElement(element: IrElement, data: Nothing?): ProgressionInfo? = null
+
+    override fun visitCall(expression: IrCall, data: Nothing?): ProgressionInfo? {
+        val progressionType = expression.type.getProgressionType()
+                ?: return null
+
+        return handlers.firstNotNullResult { it.handle(expression, progressionType) }
+    }
+}
@@ -0,0 +1,47 @@
+package org.jetbrains.kotlin.backend.konan.lower.matchers
+
+import org.jetbrains.kotlin.ir.expressions.IrCall
+import org.jetbrains.kotlin.ir.expressions.IrExpression
+
+
+internal interface IrCallMatcher : (IrCall) -> Boolean
+
+/**
+ * IrCallMatcher that puts restrictions only on its callee.
+ */
+internal class SimpleCalleeMatcher(
+        restrictions: IrFunctionMatcherContainer.() -> Unit
+) : IrCallMatcher {
+
+    private val calleeRestriction: IrFunctionMatcher
+            = createIrFunctionRestrictions(restrictions)
+
+    override fun invoke(call: IrCall) = calleeRestriction(call.symbol.owner)
+}
+
+internal class IrCallExtensionReceiverMatcher(
+        val restriction: (IrExpression?) -> Boolean
+) : IrCallMatcher {
+    override fun invoke(call: IrCall) = restriction(call.extensionReceiver)
+}
+
+internal open class IrCallMatcherContainer : IrCallMatcher {
+
+    private val matchers = mutableListOf<IrCallMatcher>()
+
+    fun add(matcher: IrCallMatcher) {
+        matchers += matcher
+    }
+
+    fun extensionReceiver(restriction: (IrExpression?) -> Boolean) =
+            add(IrCallExtensionReceiverMatcher(restriction))
+
+    fun callee(restrictions: IrFunctionMatcherContainer.() -> Unit) {
+        add(SimpleCalleeMatcher(restrictions))
+    }
+
+    override fun invoke(call: IrCall) = matchers.all { it(call) }
+}
+
+internal fun createIrCallMatcher(restrictions: IrCallMatcherContainer.() -> Unit) =
+        IrCallMatcherContainer().apply(restrictions)
@@ -0,0 +1,96 @@
+package org.jetbrains.kotlin.backend.konan.lower.matchers
+
+import org.jetbrains.kotlin.backend.konan.irasdescriptors.fqNameSafe
+import org.jetbrains.kotlin.ir.declarations.IrFunction
+import org.jetbrains.kotlin.ir.declarations.IrValueParameter
+import org.jetbrains.kotlin.ir.symbols.IrClassSymbol
+import org.jetbrains.kotlin.ir.types.classifierOrNull
+import org.jetbrains.kotlin.name.FqName
+
+internal interface IrFunctionMatcher : (IrFunction) -> Boolean
+
+internal class ParameterMatcher(
+        val index: Int,
+        val restriction: (IrValueParameter) -> Boolean
+) : IrFunctionMatcher {
+
+    override fun invoke(function: IrFunction): Boolean {
+        val params = function.valueParameters
+        return params.size > index && restriction(params[index])
+    }
+}
+
+internal class DispatchReceiverMatcher(
+        val restriction: (IrValueParameter?) -> Boolean
+) : IrFunctionMatcher {
+
+    override fun invoke(function: IrFunction): Boolean {
+        return restriction(function.dispatchReceiverParameter)
+    }
+}
+
+internal class ExtensionReceiverMatcher(
+        val restriction: (IrValueParameter?) -> Boolean
+) : IrFunctionMatcher {
+
+    override fun invoke(function: IrFunction): Boolean {
+        return restriction(function.extensionReceiverParameter)
+    }
+}
+
+internal class ParameterCountMatcher(
+        val restriction: (Int) -> Boolean
+) : IrFunctionMatcher {
+
+    override fun invoke(function: IrFunction): Boolean {
+        return restriction(function.valueParameters.size)
+    }
+}
+
+internal class FqNameMatcher(
+        val restriction: (FqName) -> Boolean
+) : IrFunctionMatcher {
+
+    override fun invoke(function: IrFunction): Boolean {
+        return restriction(function.fqNameSafe)
+    }
+}
+
+internal open class IrFunctionMatcherContainer : IrFunctionMatcher {
+    private val restrictions = mutableListOf<IrFunctionMatcher>()
+
+    fun add(restriction: IrFunctionMatcher) {
+        restrictions += restriction
+    }
+
+    fun fqName(restriction: (FqName) -> Boolean) =
+            add(FqNameMatcher(restriction))
+
+    fun parameterCount(restriction: (Int) -> Boolean) =
+            add(ParameterCountMatcher(restriction))
+
+    fun extensionReceiver(restriction: (IrValueParameter?) -> Boolean) =
+            add(ExtensionReceiverMatcher(restriction))
+
+    fun dispatchReceiver(restriction: (IrValueParameter?) -> Boolean) =
+            add(DispatchReceiverMatcher(restriction))
+
+    fun parameter(index: Int, restriction: (IrValueParameter) -> Boolean) =
+            add(ParameterMatcher(index, restriction))
+
+    override fun invoke(function: IrFunction) = restrictions.all { it(function) }
+}
+
+internal fun createIrFunctionRestrictions(restrictions: IrFunctionMatcherContainer.() -> Unit) =
+        IrFunctionMatcherContainer().apply(restrictions)
+
+internal fun IrFunctionMatcherContainer.singleArgumentExtension(
+        fqName: FqName,
+        classes: Collection<IrClassSymbol>
+): IrFunctionMatcherContainer {
+    extensionReceiver { it != null && it.type.classifierOrNull in classes }
+    parameterCount { it == 1 }
+    fqName { it == fqName }
+    return this
+}
+
@@ -0,0 +1,104 @@
+package org.jetbrains.ring
+
+class ForLoopsBenchmark {
+
+    private val array: Array<Int> = Array(BENCHMARK_SIZE) {
+        it
+    }
+
+    private val intArray: IntArray = IntArray(BENCHMARK_SIZE) {
+        it
+    }
+
+    private val charArray: CharArray = CharArray(BENCHMARK_SIZE) {
+        it.toChar()
+    }
+
+    private val string: String = charArray.joinToString()
+
+    private val floatArray: FloatArray = FloatArray(BENCHMARK_SIZE) {
+        it.toFloat()
+    }
+
+    fun arrayLoop(): Long {
+        var sum = 0L
+        for (e in array) {
+            sum += e
+        }
+        return sum
+    }
+
+    fun intArrayLoop(): Long {
+        var sum = 0L
+        for (e in intArray) {
+            sum += e
+        }
+        return sum
+    }
+
+    fun charArrayLoop(): Long {
+        var sum = 0L
+        for (e in charArray) {
+            sum += e.toLong()
+        }
+        return sum
+    }
+
+    fun stringLoop(): Long {
+        var sum = 0L
+        for (e in string) {
+            sum += e.hashCode()
+        }
+        return sum
+    }
+
+    fun floatArrayLoop(): Double {
+        var sum = 0.0
+        for (e in array) {
+            sum += e
+        }
+        return sum
+    }
+
+    // Iterations over .indices
+
+    fun arrayIndicesLoop(): Long {
+        var sum = 0L
+        for (i in array.indices) {
+            sum += array[i]
+        }
+        return sum
+    }
+
+    fun intArrayIndicesLoop(): Long {
+        var sum = 0L
+        for (i in intArray.indices) {
+            sum += intArray[i]
+        }
+        return sum
+    }
+
+    fun charArrayIndicesLoop(): Long {
+        var sum = 0L
+        for (i in charArray.indices) {
+            sum += charArray[i].toLong()
+        }
+        return sum
+    }
+
+    fun stringIndicesLoop(): Long {
+        var sum = 0L
+        for (i in string.indices) {
+            sum += string[i].hashCode()
+        }
+        return sum
+    }
+
+    fun floatArrayIndicesLoop(): Double {
+        var sum = 0.0
+        for (i in floatArray.indices) {
+            sum += floatArray[i]
+        }
+        return sum
+    }
+}
@@ -79,6 +79,7 @@ class Launcher(val numWarmIterations: Int) {
        runElvisBenchmark()
        runEulerBenchmark()
        runFibonacciBenchmark()
+        runForLoopBenchmark()
        runInlineBenchmark()
        runIntArrayBenchmark()
        runIntBaselineBenchmark()
@@ -267,6 +268,24 @@ class Launcher(val numWarmIterations: Int) {

    //-------------------------------------------------------------------------//

+    fun runForLoopBenchmark() {
+        val benchmark = ForLoopsBenchmark()
+
+        results["ForLoops.arrayLoop"] = launch(benchmark::arrayLoop)
+        results["ForLoops.intArrayLoop"] = launch(benchmark::intArrayLoop)
+        results["ForLoops.floatArrayLoop"] = launch(benchmark::floatArrayLoop)
+        results["ForLoops.charArrayLoop"] = launch(benchmark::charArrayLoop)
+        results["ForLoops.stringLoop"] = launch(benchmark::stringLoop)
+
+        results["ForLoops.arrayIndicesLoop"] = launch(benchmark::arrayIndicesLoop)
+        results["ForLoops.intArrayIndicesLoop"] = launch(benchmark::intArrayIndicesLoop)
+        results["ForLoops.floatArrayIndicesLoop"] = launch(benchmark::floatArrayIndicesLoop)
+        results["ForLoops.charArrayIndicesLoop"] = launch(benchmark::charArrayIndicesLoop)
+        results["ForLoops.stringIndicesLoop"] = launch(benchmark::stringIndicesLoop)
+    }
+
+    //-------------------------------------------------------------------------//
+
    fun runInlineBenchmark() {
        val benchmark = InlineBenchmark()
        results["Inline.calculate"]              = launch(benchmark::calculate)