JVM_IR: do not erase constant non-static field initializers...

...unless in 1.4 mode.

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

@@ -51,14 +51,21 @@ abstract class InitializersLoweringBase(open val context: CommonBackendContext)
             irClass.declarations.removeAll { it is IrAnonymousInitializer && filter(it) }
         }
 
+    protected open fun shouldEraseFieldInitializer(irField: IrField): Boolean = true
+
     private fun handleField(irClass: IrClass, declaration: IrField): IrStatement? =
         declaration.initializer?.run {
             val receiver = if (!declaration.isStatic) // TODO isStaticField
                 IrGetValueImpl(startOffset, endOffset, irClass.thisReceiver!!.type, irClass.thisReceiver!!.symbol)
             else
                 null
-            declaration.initializer = null
-            IrSetFieldImpl(startOffset, endOffset, declaration.symbol, receiver, expression, context.irBuiltIns.unitType)
+            val value = if (shouldEraseFieldInitializer(declaration)) {
+                declaration.initializer = null
+                expression
+            } else {
+                expression.deepCopyWithSymbols()
+            }
+            IrSetFieldImpl(startOffset, endOffset, declaration.symbol, receiver, value, context.irBuiltIns.unitType)
         }
 
     private fun handleAnonymousInitializer(declaration: IrAnonymousInitializer): IrStatement =

compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/JvmLower.kt

@@ -173,8 +173,13 @@ private val staticInitializersPhase = makeIrFilePhase(
     description = "Move code from object init blocks and static field initializers to a new <clinit> function"
 )
 
-private val initializersPhase = makeIrFilePhase(
-    ::InitializersLowering,
+private val initializersPhase = makeIrFilePhase<JvmBackendContext>(
+    { context ->
+        object : InitializersLowering(context) {
+            override fun shouldEraseFieldInitializer(irField: IrField): Boolean =
+                irField.constantValue(context) == null
+        }
+    },
     name = "Initializers",
     description = "Merge init blocks and field initializers into constructors",
     stickyPostconditions = setOf(fun(irFile: IrFile) {

compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/lower/ConstLowering.kt

@@ -33,12 +33,12 @@ fun IrField.constantValue(context: JvmBackendContext? = null): IrConst<*>? {
     // JVM has a ConstantValue attribute which does two things:
     //   1. allows the field to be inlined into other modules;
     //   2. implicitly generates an initialization of that field in <clinit>
-    // It is only allowed on static final fields of primitive/string types. Java and Kotlin < 1.4
+    // It is only allowed on final fields of primitive/string types. Java and Kotlin < 1.4
     // apply it whenever possible; Kotlin >= 1.4 only applies it to `const val`s to avoid making
     // values part of the library's ABI unless explicitly requested by the author.
     val allowImplicitConst =
         context != null && !context.state.languageVersionSettings.supportsFeature(LanguageFeature.NoConstantValueAttributeForNonConstVals)
-    val implicitConst = isStatic && isFinal && (origin == IrDeclarationOrigin.IR_EXTERNAL_JAVA_DECLARATION_STUB ||
+    val implicitConst = isFinal && ((isStatic && origin == IrDeclarationOrigin.IR_EXTERNAL_JAVA_DECLARATION_STUB) ||
             (allowImplicitConst && (type.isPrimitiveType() || type.isStringClassType())))
     return if (implicitConst || correspondingPropertySymbol?.owner?.isConst == true) value else null
 }

compiler/testData/codegen/bytecodeText/constProperty/nonConstValHasNoDefaultValue_before.kt

@@ -1,5 +1,4 @@
 // !LANGUAGE: -NoConstantValueAttributeForNonConstVals +JvmFieldInInterface
-// IGNORE_BACKEND: JVM_IR
 
 class C {
     val testClassVal = 100

compiler/testData/loadJava/compiledKotlin/prop/nonConstValWithConstantValueAttribute.kt

@@ -1,5 +1,4 @@
 // !LANGUAGE: -NoConstantValueAttributeForNonConstVals
-// IGNORE_BACKEND: JVM_IR
 //ALLOW_AST_ACCESS
 
 package test