backend: improve type operators support:

* add initial support for casts with generics;
* optimize out the casts to subtypes

Also add tests unchecked_cast{1,2}, the latter is disabled.

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/common/lower/LowerUtils.kt

@@ -18,28 +18,28 @@ import org.jetbrains.kotlin.utils.Printer
 
 class IrLoweringContext(backendContext: BackendContext) : IrGeneratorContext(backendContext.irBuiltIns)
 
-class FunctionIrGenerator(backendContext: BackendContext, functionDescriptor: FunctionDescriptor) : IrGeneratorWithScope {
-    override val context = IrLoweringContext(backendContext)
-    override val scope = Scope(functionDescriptor)
-}
+class FunctionIrBuilder(backendContext: BackendContext, functionDescriptor: FunctionDescriptor) :
+        IrBuilderWithScope(
+                IrLoweringContext(backendContext),
+                Scope(functionDescriptor),
+                UNDEFINED_OFFSET,
+                UNDEFINED_OFFSET
+        )
 
-fun BackendContext.createFunctionIrGenerator(functionDescriptor: FunctionDescriptor) =
-        FunctionIrGenerator(this, functionDescriptor)
+fun BackendContext.createFunctionIrBuilder(functionDescriptor: FunctionDescriptor) =
+        FunctionIrBuilder(this, functionDescriptor)
 
-class FunctionIrBuilder(context: IrLoweringContext, scope: Scope, startOffset: Int, endOffset: Int) :
-        IrBuilderWithScope(context, scope, startOffset, endOffset)
-
-fun FunctionIrGenerator.createIrBuilder() = FunctionIrBuilder(context, scope, UNDEFINED_OFFSET, UNDEFINED_OFFSET)
+fun <T : IrBuilder> T.at(element: IrElement) = this.at(element.startOffset, element.endOffset)
 
 /**
  * Builds [IrBlock] to be used instead of given expression.
  */
-inline fun FunctionIrGenerator.irBlock(expression: IrExpression, origin: IrStatementOrigin? = null,
-                                       resultType: KotlinType? = expression.type,
-                                       body: IrBlockBuilder.() -> Unit) =
+inline fun IrGeneratorWithScope.irBlock(expression: IrExpression, origin: IrStatementOrigin? = null,
+                                        resultType: KotlinType? = expression.type,
+                                        body: IrBlockBuilder.() -> Unit) =
         this.irBlock(expression.startOffset, expression.endOffset, origin, resultType, body)
 
-inline fun FunctionIrGenerator.irBlockBody(irElement: IrElement, body: IrBlockBodyBuilder.() -> Unit) =
+inline fun IrGeneratorWithScope.irBlockBody(irElement: IrElement, body: IrBlockBodyBuilder.() -> Unit) =
         this.irBlockBody(irElement.startOffset, irElement.endOffset, body)
 
 fun computeOverrides(current: ClassDescriptor, functionsFromCurrent: List<CallableMemberDescriptor>): List<DeclarationDescriptor> {

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/lower/CallableReferenceLowering.kt

@@ -1,7 +1,7 @@
 package org.jetbrains.kotlin.backend.konan.lower
 
 import org.jetbrains.kotlin.backend.common.DeclarationContainerLoweringPass
-import org.jetbrains.kotlin.backend.common.lower.createFunctionIrGenerator
+import org.jetbrains.kotlin.backend.common.lower.createFunctionIrBuilder
 import org.jetbrains.kotlin.backend.konan.*
 import org.jetbrains.kotlin.backend.konan.descriptors.*
 import org.jetbrains.kotlin.backend.konan.ir.*
@@ -136,8 +136,8 @@ private class CallableReferencesUnbinder(val lower: CallableReferenceLowering,
         // Create new function descriptor:
         val newDescriptor = createSimpleFunctionImplTargetDescriptor(descriptor, unboundParams)
 
-        val generator = lower.context.createFunctionIrGenerator(newDescriptor)
-        val blockBody = generator.irBlockBody(startOffset, endOffset) {
+        val builder = lower.context.createFunctionIrBuilder(newDescriptor)
+        val blockBody = builder.irBlockBody(startOffset, endOffset) {
             val boundArgsGet = irCall(simpleFunctionImplBoundArgsGetter).apply {
                 dispatchReceiver = irGet(newDescriptor.valueParameters[0])
             }

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/lower/DefaultParameterStubGenerator.kt

@@ -2,8 +2,8 @@ package org.jetbrains.kotlin.backend.konan.lower
 
 import org.jetbrains.kotlin.backend.common.BodyLoweringPass
 import org.jetbrains.kotlin.backend.common.DeclarationContainerLoweringPass
-import org.jetbrains.kotlin.backend.common.lower.createFunctionIrGenerator
-import org.jetbrains.kotlin.backend.common.lower.createIrBuilder
+import org.jetbrains.kotlin.backend.common.lower.createFunctionIrBuilder
+import org.jetbrains.kotlin.backend.common.lower.irBlockBody
 import org.jetbrains.kotlin.backend.konan.Context
 import org.jetbrains.kotlin.backend.konan.KonanPlatform
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns
@@ -61,14 +61,9 @@ class DefaultParameterStubGenerator internal constructor(val context: Context):
 
         val functionDescriptor = irFunction.descriptor
         if (bodies.isNotEmpty()) {
-          val (descriptor, mask, extension, dispatch) = functionDescriptor.generateDefaultsDescriptor()
-            val generator = context.createFunctionIrGenerator(descriptor)
-            val builder = generator.createIrBuilder()
-            builder.apply {
-                startOffset = irFunction.startOffset
-                endOffset   = irFunction.endOffset
-            }
-            val body = generator.irBlockBody {
+            val (descriptor, mask, extension, dispatch) = functionDescriptor.generateDefaultsDescriptor()
+            val builder = context.createFunctionIrBuilder(descriptor)
+            val body = builder.irBlockBody(irFunction) {
                 val params = mutableListOf<VariableDescriptor>()
                 val variables = mutableMapOf<VariableDescriptor, VariableDescriptor>()
 

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/lower/TypeOperatorLowering.kt

@@ -1,10 +1,10 @@
 package org.jetbrains.kotlin.backend.konan.lower
 
 import org.jetbrains.kotlin.backend.common.FunctionLoweringPass
-import org.jetbrains.kotlin.backend.common.lower.createFunctionIrGenerator
-import org.jetbrains.kotlin.backend.common.lower.irBlock
+import org.jetbrains.kotlin.backend.common.lower.*
 import org.jetbrains.kotlin.backend.konan.Context
 import org.jetbrains.kotlin.descriptors.FunctionDescriptor
+import org.jetbrains.kotlin.descriptors.TypeParameterDescriptor
 import org.jetbrains.kotlin.ir.IrStatement
 import org.jetbrains.kotlin.ir.builders.*
 import org.jetbrains.kotlin.ir.declarations.IrFunction
@@ -13,6 +13,8 @@ import org.jetbrains.kotlin.ir.expressions.IrTypeOperator
 import org.jetbrains.kotlin.ir.expressions.IrTypeOperatorCall
 import org.jetbrains.kotlin.ir.visitors.IrElementTransformerVoid
 import org.jetbrains.kotlin.ir.visitors.transformChildrenVoid
+import org.jetbrains.kotlin.types.KotlinType
+import org.jetbrains.kotlin.types.typeUtil.isSubtypeOf
 
 /**
  * This lowering pass lowers some [IrTypeOperatorCall]s.
@@ -27,19 +29,45 @@ internal class TypeOperatorLowering(val context: Context) : FunctionLoweringPass
 
 private class TypeOperatorTransformer(val context: Context, val function: FunctionDescriptor) : IrElementTransformerVoid() {
 
-    private val generator = context.createFunctionIrGenerator(function)
+    private val builder = context.createFunctionIrBuilder(function)
 
     override fun visitFunction(declaration: IrFunction): IrStatement {
         // ignore inner functions during this pass
         return declaration
     }
 
+    private tailrec fun KotlinType.erasure(): KotlinType {
+        val descriptor = this.constructor.declarationDescriptor
+        return if (descriptor is TypeParameterDescriptor) {
+            val upperBound = descriptor.upperBounds.singleOrNull() ?:
+                TODO("$descriptor : ${descriptor.upperBounds}")
+
+            upperBound.erasure()
+        } else {
+            this
+        }
+    }
+
+    private fun lowerCast(expression: IrTypeOperatorCall): IrExpression {
+        val typeOperand = expression.typeOperand.erasure()
+        return if (expression.argument.type.isSubtypeOf(typeOperand)) {
+            // TODO: consider the case when expression type is wrong e.g. due to generics-related unchecked casts.
+            expression.argument
+        } else if (typeOperand == expression.typeOperand) {
+            expression
+        } else {
+            builder.at(expression).irAs(expression.argument, typeOperand)
+        }
+    }
+
     private fun lowerSafeCast(expression: IrTypeOperatorCall): IrExpression {
-        return generator.irBlock(expression) {
+        val typeOperand = expression.typeOperand.erasure()
+
+        return builder.irBlock(expression) {
             +irLet(expression.argument) { variable ->
                 irIfThenElse(expression.type,
-                        condition = irIs(irGet(variable), expression.typeOperand),
-                        thenPart = irImplicitCast(irGet(variable), expression.typeOperand),
+                        condition = irIs(irGet(variable), typeOperand),
+                        thenPart = irImplicitCast(irGet(variable), typeOperand),
                         elsePart = irNull())
             }
         }
@@ -50,6 +78,7 @@ private class TypeOperatorTransformer(val context: Context, val function: Functi
 
         return when (expression.operator) {
             IrTypeOperator.SAFE_CAST -> lowerSafeCast(expression)
+            IrTypeOperator.CAST -> lowerCast(expression)
             else -> expression
         }
     }

backend.native/tests/build.gradle

@@ -208,6 +208,17 @@ task cast_simple(type: RunKonanTest) {
     source = "codegen/basics/cast_simple.kt"
 }
 
+task unchecked_cast1(type: RunKonanTest) {
+    goldValue = "17\n17\n42\n42\n"
+    source = "codegen/basics/unchecked_cast1.kt"
+}
+
+task unchecked_cast2(type: RunKonanTest) {
+    disabled = true
+    goldValue = "Ok\n"
+    source = "codegen/basics/unchecked_cast2.kt"
+}
+
 task null_check(type: RunKonanTest) {
     source = "codegen/basics/null_check.kt"
 }

backend.native/tests/codegen/basics/unchecked_cast1.kt

@@ -0,0 +1,16 @@
+fun main(args: Array<String>) {
+    foo<String>("17")
+    bar<String>("17")
+    foo<String>(42)
+    bar<String>(42)
+}
+
+fun <T> foo(x: Any?) {
+    val y = x as T
+    println(y.toString())
+}
+
+fun <T> bar(x: Any?) {
+    val y = x as? T
+    println(y.toString())
+}

backend.native/tests/codegen/basics/unchecked_cast2.kt

@@ -0,0 +1,10 @@
+fun main(args: Array<String>) {
+    try {
+        val x = cast<String>(Any())
+        println(x.length)
+    } catch (e: Throwable) {
+        println("Ok")
+    }
+}
+
+fun <T> cast(x: Any?) = x as T