KT53100: Optimization: <T-unbox>(CONSTANT_PRIMITIVE(x: T?)) => x

Merge-request: KT-MR-6684
Merged-by: Vladimir Sukharev <Vladimir.Sukharev@jetbrains.com>

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

@@ -7,11 +7,9 @@ package org.jetbrains.kotlin.backend.konan.lower
 
 import org.jetbrains.kotlin.backend.common.FileLoweringPass
 import org.jetbrains.kotlin.backend.konan.Context
-import org.jetbrains.kotlin.backend.konan.DECLARATION_ORIGIN_INLINE_CLASS_SPECIAL_FUNCTION
 import org.jetbrains.kotlin.backend.konan.getInlinedClassNative
 import org.jetbrains.kotlin.backend.konan.ir.isBoxOrUnboxCall
 import org.jetbrains.kotlin.ir.IrElement
-import org.jetbrains.kotlin.ir.IrStatement
 import org.jetbrains.kotlin.ir.declarations.IrClass
 import org.jetbrains.kotlin.ir.declarations.IrFile
 import org.jetbrains.kotlin.ir.declarations.IrFunction
@@ -19,6 +17,7 @@ import org.jetbrains.kotlin.ir.expressions.*
 import org.jetbrains.kotlin.ir.expressions.impl.*
 import org.jetbrains.kotlin.ir.symbols.impl.IrReturnableBlockSymbolImpl
 import org.jetbrains.kotlin.ir.types.classifierOrFail
+import org.jetbrains.kotlin.ir.types.classifierOrNull
 import org.jetbrains.kotlin.ir.util.dump
 import org.jetbrains.kotlin.ir.util.getArgumentsWithIr
 import org.jetbrains.kotlin.ir.visitors.IrElementTransformerVoid
@@ -266,6 +265,16 @@ internal class RedundantCoercionsCleaner(val context: Context) : FileLoweringPas
                     }
                 }
 
+            is IrConstantPrimitive ->
+                if (expression.value.type == coercion.type) {
+                    // In case the initial and final types are equal, then
+                    // the whole sequence of transformations is no-op, and we can remove them all
+                    PossiblyFoldedExpression(expression.value, true)
+                } else {
+                    // Types are not equal for ex. in kt53100_casts.kt
+                    PossiblyFoldedExpression(expression.transformIfAsked(), false)
+                }
+
             else -> PossiblyFoldedExpression(expression.transformIfAsked(), false)
         }
     }

kotlin-native/backend.native/tests/build.gradle

@@ -2581,6 +2581,11 @@ task boxing15(type: KonanLocalTest) {
     source = "codegen/boxing/boxing15.kt"
 }
 
+task kt53100_casts(type: KonanLocalTest) {
+    useGoldenData = true
+    source = "codegen/boxing/kt53100_casts.kt"
+}
+
 task boxCache0(type: KonanLocalTest) {
     useGoldenData = true
     source = "codegen/boxing/box_cache0.kt"

kotlin-native/backend.native/tests/codegen/boxing/kt53100_casts.kt

@@ -0,0 +1,22 @@
+/*
+ * Copyright 2010-2022 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package codegen.boxing.kt53100_casts
+
+import kotlin.test.*
+
+// Reproducer is copied from FloatingPointParser.unaryMinus()
+inline fun <reified T> unaryMinus(value: T): T {
+    return when (value) {
+        is Float -> -value as T
+        is Double -> -value as T
+        else -> throw NumberFormatException()
+    }
+}
+
+@Test fun runTest(){
+    println(unaryMinus(0.0))
+    println(unaryMinus(0.0f))
+}

kotlin-native/backend.native/tests/codegen/boxing/kt53100_casts.out

@@ -0,0 +1,2 @@
+-0.0
+-0.0

kotlin-native/backend.native/tests/filecheck/kt49847_class.kt

@@ -9,8 +9,6 @@ class C {
 
 // CHECK-LABEL: define void @"kfun:#main(){}"()
 // CHECK-NOT: Int-box
-//   TODO Remove next check after fix of https://youtrack.jetbrains.com/issue/KT-53100/Optimization-needed-T-unboxCONSTANTPRIMITIVEx-T-x
-// CHECK: Int-unbox
 // CHECK-NOT: Int-unbox
 // CHECK: ret void
 fun main() {

kotlin-native/backend.native/tests/filecheck/kt49847_generic.kt

@@ -9,8 +9,6 @@ class C<T> {
 
 // CHECK-LABEL: define void @"kfun:#main(){}"()
 // CHECK-NOT: Int-box
-//   TODO Remove next check after fix of https://youtrack.jetbrains.com/issue/KT-53100/Optimization-needed-T-unboxCONSTANTPRIMITIVEx-T-x
-// CHECK: Int-unbox
 // CHECK-NOT: Int-unbox
 // CHECK: ret void
 fun main() {