Allow merging tracked values in ReferenceTrackingInterpreter subclasses

This is required for things like detupling.

compiler/backend/src/org/jetbrains/kotlin/codegen/optimization/captured/ReferenceTrackingInterpreter.kt

@@ -29,25 +29,42 @@ abstract class ReferenceTrackingInterpreter : OptimizationBasicInterpreter() {
                     if (v.descriptor == w.descriptor)
                         v
                     else
-                        TaintedTrackedReferenceValue(
-                                getTaintedValueType(v.type, w.type),
-                                setOf(v.descriptor, w.descriptor)
-                        )
+                        createTaintedValue(v, w)
+
+                v is TrackedReferenceValue && w is TrackedReferenceValue ->
+                    createPossiblyMergedValue(v, w)
 
                 v is TrackedReferenceValue || w is TrackedReferenceValue ->
-                    TaintedTrackedReferenceValue(
-                            getTaintedValueType(v.type, w.type),
-                            v.referenceValueDescriptors + w.referenceValueDescriptors
-                    )
+                    createTaintedValue(v, w)
 
                 else ->
                     super.merge(v, w)
             }
 
+    protected fun createTaintedValue(v: BasicValue, w: BasicValue) : TrackedReferenceValue =
+            TaintedTrackedReferenceValue(
+                    getMergedValueType(v.type, w.type),
+                    mergeDescriptors(v, w).also {
+                        assert(it.isNotEmpty()) { "At least one of ($v, $w) should be a tracked reference" }
+                    }
+            )
+
+    protected fun createMergedValue(v: TrackedReferenceValue, w: TrackedReferenceValue): TrackedReferenceValue =
+            if (v is TaintedTrackedReferenceValue || w is TaintedTrackedReferenceValue)
+                createTaintedValue(v, w)
+            else
+                MergedTrackedReferenceValue(getMergedValueType(v.type, w.type), mergeDescriptors(v, w))
+
+    protected open fun createPossiblyMergedValue(v: TrackedReferenceValue, w: TrackedReferenceValue): TrackedReferenceValue =
+            createTaintedValue(v, w)
+
+    private fun mergeDescriptors(v: BasicValue, w: BasicValue) =
+            v.referenceValueDescriptors + w.referenceValueDescriptors
+
     private val BasicValue.referenceValueDescriptors: Set<ReferenceValueDescriptor>
         get() = if (this is TrackedReferenceValue) this.descriptors else emptySet()
 
-    private fun getTaintedValueType(type1: Type?, type2: Type?): Type =
+    protected fun getMergedValueType(type1: Type?, type2: Type?): Type =
             when {
                 type1 == null || type2 == null -> AsmTypes.OBJECT_TYPE
                 type1 == type2 -> type1

compiler/backend/src/org/jetbrains/kotlin/codegen/optimization/captured/TrackedReferenceValue.kt

@@ -23,7 +23,7 @@ interface ReferenceValueDescriptor {
     fun onUseAsTainted()
 }
 
-abstract class TrackedReferenceValue(type: Type): StrictBasicValue(type) {
+sealed class TrackedReferenceValue(type: Type): StrictBasicValue(type) {
     abstract val descriptors: Set<ReferenceValueDescriptor>
 }
 
@@ -42,6 +42,20 @@ class ProperTrackedReferenceValue(type: Type, val descriptor: ReferenceValueDesc
             "[$descriptor]"
 }
 
+
+class MergedTrackedReferenceValue(type: Type, override val descriptors: Set<ReferenceValueDescriptor>) : TrackedReferenceValue(type) {
+    override fun equals(other: Any?): Boolean =
+            other === this ||
+            other is MergedTrackedReferenceValue && other.descriptors == this.descriptors
+
+    override fun hashCode(): Int =
+            descriptors.hashCode()
+
+    override fun toString(): String =
+            descriptors.toString()
+}
+
+
 class TaintedTrackedReferenceValue(type: Type, override val descriptors: Set<ReferenceValueDescriptor>) : TrackedReferenceValue(type) {
     override fun equals(other: Any?): Boolean =
             other === this ||
@@ -49,7 +63,6 @@ class TaintedTrackedReferenceValue(type: Type, override val descriptors: Set<Ref
 
     override fun hashCode(): Int =
             descriptors.hashCode()
-
     override fun toString(): String =
             "!$descriptors"
 }