JVM represent uninitialized values explicitly in stack normalization

compiler/backend/src/org/jetbrains/kotlin/codegen/optimization/fixStack/FixStackAnalyzer.kt

@@ -19,7 +19,6 @@ package org.jetbrains.kotlin.codegen.optimization.fixStack
 import com.intellij.util.containers.Stack
 import org.jetbrains.kotlin.codegen.inline.isAfterInlineMarker
 import org.jetbrains.kotlin.codegen.inline.isBeforeInlineMarker
-import org.jetbrains.kotlin.codegen.inline.isMarkedReturn
 import org.jetbrains.kotlin.codegen.pseudoInsns.PseudoInsn
 import org.jetbrains.kotlin.utils.SmartList
 import org.jetbrains.org.objectweb.asm.Opcodes
@@ -132,10 +131,8 @@ internal class FixStackAnalyzer(
                         executeBeforeInlineCallMarker(insn)
                     isAfterInlineMarker(insn) ->
                         executeAfterInlineCallMarker(insn)
-                    isMarkedReturn(insn) -> {
-                        // KT-9644: might throw "Incompatible return type" on non-local return, in fact we don't care.
-                        if (insn.opcode == Opcodes.RETURN) return
-                    }
+                    insn.opcode == Opcodes.RETURN ->
+                        return
                 }
 
                 super.execute(insn, interpreter)
@@ -151,6 +148,9 @@ internal class FixStackAnalyzer(
             }
 
             override fun push(value: FixStackValue) {
+                if (value == FixStackValue.UNINITIALIZED) {
+                    throw AnalyzerException(null, "Uninitialized value on stack")
+                }
                 if (super.getStackSize() < maxStackSize) {
                     super.push(value)
                 } else {

compiler/backend/src/org/jetbrains/kotlin/codegen/optimization/fixStack/FixStackInterpreter.kt

@@ -14,8 +14,9 @@ import org.jetbrains.org.objectweb.asm.tree.analysis.Interpreter
 
 open class FixStackInterpreter : Interpreter<FixStackValue>(API_VERSION) {
 
-    override fun newValue(type: Type?): FixStackValue? =
+    override fun newValue(type: Type?): FixStackValue =
         type?.toFixStackValue()
+            ?: FixStackValue.UNINITIALIZED
 
     override fun newOperation(insn: AbstractInsnNode): FixStackValue? =
         when (insn.opcode) {

compiler/backend/src/org/jetbrains/kotlin/codegen/optimization/fixStack/FixStackValue.kt

@@ -19,7 +19,8 @@ enum class FixStackValue(
     LONG(2, Opcodes.LLOAD, Opcodes.LSTORE, Opcodes.POP2),
     FLOAT(1, Opcodes.FLOAD, Opcodes.FSTORE, Opcodes.POP),
     DOUBLE(2, Opcodes.DLOAD, Opcodes.DSTORE, Opcodes.POP2),
-    OBJECT(1, Opcodes.ALOAD, Opcodes.ASTORE, Opcodes.POP)
+    OBJECT(1, Opcodes.ALOAD, Opcodes.ASTORE, Opcodes.POP),
+    UNINITIALIZED(1, -1, -1, -1)
     ;
 
     override fun getSize(): Int = _size