[JVM IR] Use reference equality when comparing enums.

compiler/backend/src/org/jetbrains/kotlin/codegen/BranchedValue.kt

@@ -240,8 +240,9 @@ class ObjectCompare(
 
     companion object {
         fun getObjectCompareOpcode(opToken: IElementType): Int = when (opToken) {
-            KtTokens.EQEQEQ -> IF_ACMPNE
-            KtTokens.EXCLEQEQEQ -> IF_ACMPEQ
+            // "==" and "!=" are here because enum values are compared using reference equality.
+            KtTokens.EQEQEQ, KtTokens.EQEQ -> IF_ACMPNE
+            KtTokens.EXCLEQEQEQ, KtTokens.EXCLEQ -> IF_ACMPEQ
             else -> throw UnsupportedOperationException("don't know how to generate this condjump")
         }
     }

compiler/fir/fir2ir/tests/org/jetbrains/kotlin/codegen/ir/FirBlackBoxCodegenTestGenerated.java

@@ -9797,6 +9797,11 @@ public class FirBlackBoxCodegenTestGenerated extends AbstractFirBlackBoxCodegenT
             runTest("compiler/testData/codegen/box/enum/kt18731.kt");
         }
 
+        @TestMetadata("kt18731_2.kt")
+        public void testKt18731_2() throws Exception {
+            runTest("compiler/testData/codegen/box/enum/kt18731_2.kt");
+        }
+
         @TestMetadata("kt20651.kt")
         public void testKt20651() throws Exception {
             runTest("compiler/testData/codegen/box/enum/kt20651.kt");

compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/intrinsics/Equals.kt

@@ -23,6 +23,8 @@ import org.jetbrains.kotlin.ir.types.IrType
 import org.jetbrains.kotlin.ir.types.classOrNull
 import org.jetbrains.kotlin.ir.types.isNullable
 import org.jetbrains.kotlin.ir.types.toKotlinType
+import org.jetbrains.kotlin.ir.util.isEnumClass
+import org.jetbrains.kotlin.ir.util.isEnumEntry
 import org.jetbrains.kotlin.ir.util.isNullConst
 import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.resolve.jvm.AsmTypes
@@ -80,10 +82,14 @@ class Equals(val operator: IElementType) : IntrinsicMethod() {
         val leftType = with(codegen) { a.asmType }
         val rightType = with(codegen) { b.asmType }
         val opToken = expression.origin
+        val aIsEnum = a.type.classOrNull?.owner?.run { isEnumClass || isEnumEntry } == true
+        val bIsEnum = b.type.classOrNull?.owner?.run { isEnumClass || isEnumEntry } == true
         val useEquals = opToken !== IrStatementOrigin.EQEQEQ && opToken !== IrStatementOrigin.EXCLEQEQ &&
                 // `==` is `equals` for objects and floating-point numbers. In the latter case, the difference
                 // is that `equals` is a total order (-0 < +0 and NaN == NaN) and `===` is IEEE754-compliant.
                 (!isPrimitive(leftType) || leftType != rightType || leftType == Type.FLOAT_TYPE || leftType == Type.DOUBLE_TYPE)
+                // Reference equality can be used for enums.
+                && !aIsEnum && !bIsEnum
         return if (useEquals) {
             a.accept(codegen, data).materializeAt(AsmTypes.OBJECT_TYPE, codegen.context.irBuiltIns.anyNType)
             b.accept(codegen, data).materializeAt(AsmTypes.OBJECT_TYPE, codegen.context.irBuiltIns.anyNType)

compiler/testData/codegen/box/enum/kt18731.kt

@@ -6,7 +6,7 @@ enum class Bar {
 fun isOne(i: Bar) = i == Bar.ONE
 
 fun box(): String {
-    return when (isOne(Bar.ONE) && !isOne(Bar.TWO)) {
+    return when (isOne(Bar.ONE) && !isOne(Bar.TWO) && Bar.ONE != Bar.TWO) {
         true -> "OK"
         else -> "Failure"
     }

compiler/testData/codegen/box/enum/kt18731_2.kt

@@ -0,0 +1,14 @@
+// IGNORE_BACKEND_FIR: JVM_IR
+
+enum class Bar {
+    ONE {
+        override fun toString(): String {
+            if (this != TWO && this == ONE) return "OK" else return "FAIL"
+        }
+    },
+    TWO;
+}
+
+fun box(): String {
+    return Bar.ONE.toString()
+}

compiler/testData/codegen/bytecodeText/enum/kt18731.kt

@@ -1,6 +1,3 @@
-// IGNORE_BACKEND: JVM_IR
-// TODO KT-36772 Equality compaison between enums should use reference equality in JVM_IR
-
 enum class Bar {
     ONE,
     TWO
@@ -9,11 +6,12 @@ enum class Bar {
 fun isOne(i: Bar) = i == Bar.ONE
 
 fun box(): String {
-    return when (isOne(Bar.ONE) && !isOne(Bar.TWO)) {
+    return when (isOne(Bar.ONE) && !isOne(Bar.TWO) && Bar.ONE != Bar.TWO) {
         true -> "OK"
         else -> "Failure"
     }
 }
 
 // 1 IF_ACMPNE
+// 1 IF_ACMPEQ
 // 0 INVOKESTATIC kotlin/jvm/internal/Intrinsics.areEqual \(Ljava/lang/Object;Ljava/lang/Object;\)Z

compiler/testData/codegen/bytecodeText/enum/kt18731_2.kt

@@ -0,0 +1,16 @@
+enum class Bar {
+    ONE {
+        override fun toString(): String {
+            if (this != TWO && this == ONE) return "OK" else return "FAIL"
+        }
+    },
+    TWO;
+}
+
+fun box(): String {
+    return Bar.ONE.toString()
+}
+
+// 1 IF_ACMPNE
+// 1 IF_ACMPEQ
+// 0 INVOKESTATIC kotlin/jvm/internal/Intrinsics.areEqual \(Ljava/lang/Object;Ljava/lang/Object;\)Z

compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java

@@ -10942,6 +10942,11 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             runTest("compiler/testData/codegen/box/enum/kt18731.kt");
         }
 
+        @TestMetadata("kt18731_2.kt")
+        public void testKt18731_2() throws Exception {
+            runTest("compiler/testData/codegen/box/enum/kt18731_2.kt");
+        }
+
         @TestMetadata("kt20651.kt")
         public void testKt20651() throws Exception {
             runTest("compiler/testData/codegen/box/enum/kt20651.kt");

compiler/tests/org/jetbrains/kotlin/codegen/BytecodeTextTestGenerated.java

@@ -1801,6 +1801,11 @@ public class BytecodeTextTestGenerated extends AbstractBytecodeTextTest {
         public void testKt18731() throws Exception {
             runTest("compiler/testData/codegen/bytecodeText/enum/kt18731.kt");
         }
+
+        @TestMetadata("kt18731_2.kt")
+        public void testKt18731_2() throws Exception {
+            runTest("compiler/testData/codegen/bytecodeText/enum/kt18731_2.kt");
+        }
     }
 
     @TestMetadata("compiler/testData/codegen/bytecodeText/exclExcl")

compiler/tests/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java

@@ -10942,6 +10942,11 @@ public class LightAnalysisModeTestGenerated extends AbstractLightAnalysisModeTes
             runTest("compiler/testData/codegen/box/enum/kt18731.kt");
         }
 
+        @TestMetadata("kt18731_2.kt")
+        public void testKt18731_2() throws Exception {
+            runTest("compiler/testData/codegen/box/enum/kt18731_2.kt");
+        }
+
         @TestMetadata("kt20651.kt")
         public void testKt20651() throws Exception {
             runTest("compiler/testData/codegen/box/enum/kt20651.kt");

compiler/tests/org/jetbrains/kotlin/codegen/ir/IrBlackBoxCodegenTestGenerated.java

@@ -9797,6 +9797,11 @@ public class IrBlackBoxCodegenTestGenerated extends AbstractIrBlackBoxCodegenTes
             runTest("compiler/testData/codegen/box/enum/kt18731.kt");
         }
 
+        @TestMetadata("kt18731_2.kt")
+        public void testKt18731_2() throws Exception {
+            runTest("compiler/testData/codegen/box/enum/kt18731_2.kt");
+        }
+
         @TestMetadata("kt20651.kt")
         public void testKt20651() throws Exception {
             runTest("compiler/testData/codegen/box/enum/kt20651.kt");

compiler/tests/org/jetbrains/kotlin/codegen/ir/IrBytecodeTextTestGenerated.java

@@ -1756,6 +1756,11 @@ public class IrBytecodeTextTestGenerated extends AbstractIrBytecodeTextTest {
         public void testKt18731() throws Exception {
             runTest("compiler/testData/codegen/bytecodeText/enum/kt18731.kt");
         }
+
+        @TestMetadata("kt18731_2.kt")
+        public void testKt18731_2() throws Exception {
+            runTest("compiler/testData/codegen/bytecodeText/enum/kt18731_2.kt");
+        }
     }
 
     @TestMetadata("compiler/testData/codegen/bytecodeText/exclExcl")

js/js.tests/test/org/jetbrains/kotlin/js/test/ir/semantics/IrJsCodegenBoxTestGenerated.java

@@ -8417,6 +8417,11 @@ public class IrJsCodegenBoxTestGenerated extends AbstractIrJsCodegenBoxTest {
             runTest("compiler/testData/codegen/box/enum/kt18731.kt");
         }
 
+        @TestMetadata("kt18731_2.kt")
+        public void testKt18731_2() throws Exception {
+            runTest("compiler/testData/codegen/box/enum/kt18731_2.kt");
+        }
+
         @TestMetadata("kt20651.kt")
         public void testKt20651() throws Exception {
             runTest("compiler/testData/codegen/box/enum/kt20651.kt");

js/js.tests/test/org/jetbrains/kotlin/js/test/semantics/JsCodegenBoxTestGenerated.java

@@ -8417,6 +8417,11 @@ public class JsCodegenBoxTestGenerated extends AbstractJsCodegenBoxTest {
             runTest("compiler/testData/codegen/box/enum/kt18731.kt");
         }
 
+        @TestMetadata("kt18731_2.kt")
+        public void testKt18731_2() throws Exception {
+            runTest("compiler/testData/codegen/box/enum/kt18731_2.kt");
+        }
+
         @TestMetadata("kt20651.kt")
         public void testKt20651() throws Exception {
             runTest("compiler/testData/codegen/box/enum/kt20651.kt");