JVM_IR: default-initialize variables visible in the LVT

See KT-36812. Aside from the problem stated there, D8 will throw out the
entire LVT if it sees a variable that has not been written to (and will
generate incorrect SSA if the slot is reused with a different type).

Note: this only fixes a FIR test because it's missing an `else -> throw`
branch, and default initialization satisfies the verifier and masks the
incorrect control flow.

compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/codegen/ExpressionCodegen.kt

@@ -322,18 +322,14 @@ class ExpressionCodegen(
         }
     }
 
+    private val IrVariable.isVisibleInLVT: Boolean
+        get() = origin != IrDeclarationOrigin.IR_TEMPORARY_VARIABLE &&
+                origin != IrDeclarationOrigin.FOR_LOOP_ITERATOR
+
     private fun writeLocalVariablesInTable(info: BlockInfo, endLabel: Label) {
         info.variables.forEach {
-            when (it.declaration.origin) {
+            if (it.declaration.isVisibleInLVT) {
-                IrDeclarationOrigin.IR_TEMPORARY_VARIABLE,
+                mv.visitLocalVariable(it.declaration.name.asString(), it.type.descriptor, null, it.startLabel, endLabel, it.index)
-                IrDeclarationOrigin.FOR_LOOP_ITERATOR -> {
-                    // Ignore implicitly created variables
-                }
-                else -> {
-                    mv.visitLocalVariable(
-                        it.declaration.name.asString(), it.type.descriptor, null, it.startLabel, endLabel, it.index
-                    )
-                }
             }
         }
 
@@ -485,9 +481,13 @@ class ExpressionCodegen(
 
         declaration.markLineNumber(startOffset = true)
 
-        declaration.initializer?.let {
+        val initializer = declaration.initializer
-            it.accept(this, data).coerce(varType, declaration.type).materialize()
+        if (initializer != null) {
-            it.markLineNumber(startOffset = true)
+            initializer.accept(this, data).coerce(varType, declaration.type).materialize()
+            initializer.markLineNumber(startOffset = true)
+            mv.store(index, varType)
+        } else if (declaration.isVisibleInLVT) {
+            pushDefaultValueOnStack(varType, mv)
             mv.store(index, varType)
         }
 

compiler/testData/codegen/box/when/sealedWhenInitialization.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND_FIR: JVM_IR
 sealed class A {
     object B : A()
 

compiler/testData/codegen/bytecodeText/coroutines/varValueConflictsWithTableSameSort.kt

@@ -1,6 +1,3 @@
-// This test checks, that different variables occupy the same slot
-// In JVM_IR, however, loop variable's lifetime goes beyond the loop itself, thus the test has no sense in JVM_IR
-// IGNORE_BACKEND: JVM_IR
 // WITH_COROUTINES
 
 import helpers.*

compiler/testData/codegen/bytecodeText/localInitializationLVT/boxing.kt

@@ -1,6 +1,5 @@
 // IGNORE_BACKEND: JVM_IR
 // TODO KT-36648 Captured variables not optimized in JVM_IR
-// TODO KT-36812 Generate proper lifetime intervals for local variables in JVM_IR
 
 fun test(): java.lang.Integer {
     val c: java.lang.Integer

compiler/testData/codegen/bytecodeText/localInitializationLVT/contract.kt

@@ -1,5 +1,3 @@
-// IGNORE_BACKEND: JVM_IR
-// TODO KT-36812 Generate proper lifetime intervals for local variables in JVM_IR
 import kotlin.contracts.ExperimentalContracts
 import kotlin.contracts.InvocationKind
 import kotlin.contracts.contract
@@ -22,4 +20,4 @@ fun doIt(block: () -> Unit) {
 }
 
 // 0 ISTORE 0
-// 1 LOCALVARIABLE c Lkotlin/jvm/internal/Ref\$CharRef; L1 L3 0
+// 1 LOCALVARIABLE c Lkotlin/jvm/internal/Ref\$CharRef;

compiler/testData/codegen/bytecodeText/localInitializationLVT/contractVar.kt

@@ -1,5 +1,3 @@
-// IGNORE_BACKEND: JVM_IR
-// TODO KT-36812 Generate proper lifetime intervals for local variables in JVM_IR
 import kotlin.contracts.ExperimentalContracts
 import kotlin.contracts.InvocationKind
 import kotlin.contracts.contract
@@ -22,8 +20,8 @@ fun doIt(block: () -> Unit) {
 }
 
 // 0 ISTORE 0
-// 1 LOCALVARIABLE c Lkotlin/jvm/internal/Ref\$CharRef; L1 L3 0
+// 1 LOCALVARIABLE c Lkotlin/jvm/internal/Ref\$CharRef;
 
 // JVM_IR_TEMPLATES
 // 0 ISTORE 0
-// 1 LOCALVARIABLE c Lkotlin/jvm/internal/Ref\$CharRef; L1 L4 0
+// 1 LOCALVARIABLE c Lkotlin/jvm/internal/Ref\$CharRef;

compiler/testData/codegen/bytecodeText/localInitializationLVT/ifStatement.kt

@@ -1,6 +1,3 @@
-// IGNORE_BACKEND: JVM_IR
-// TODO KT-36812 Generate proper lifetime intervals for local variables in JVM_IR
-
 import kotlin.random.Random
 
 fun test(): Char {
@@ -14,4 +11,4 @@ fun test(): Char {
 }
 
 // 3 ISTORE 0
-// 1 LOCALVARIABLE c C L1 L7 0
+// 1 LOCALVARIABLE c C

compiler/testData/codegen/bytecodeText/localInitializationLVT/ifStatementVar.kt

@@ -1,6 +1,3 @@
-// IGNORE_BACKEND: JVM_IR
-// TODO KT-36812 Generate proper lifetime intervals for local variables in JVM_IR
-
 import kotlin.random.Random
 
 fun test(): Char {
@@ -14,4 +11,4 @@ fun test(): Char {
 }
 
 // 3 ISTORE 0
-// 1 LOCALVARIABLE c C L1 L7 0
+// 1 LOCALVARIABLE c C

compiler/testData/codegen/bytecodeText/localInitializationLVT/ifStatementWithoutBlock.kt

@@ -1,6 +1,3 @@
-// IGNORE_BACKEND: JVM_IR
-// TODO KT-36812 Generate proper lifetime intervals for local variables in JVM_IR
-
 import kotlin.random.Random
 
 fun test(): Char {

compiler/testData/codegen/bytecodeText/localInitializationLVT/ifStatementWithoutBlockVar.kt

@@ -1,6 +1,3 @@
-// IGNORE_BACKEND: JVM_IR
-// TODO KT-36812 Generate proper lifetime intervals for local variables in JVM_IR
-
 import kotlin.random.Random
 
 fun test(): Char {

compiler/testData/codegen/bytecodeText/localInitializationLVT/inlineClass.kt

@@ -1,6 +1,5 @@
 // IGNORE_BACKEND: JVM_IR
 // TODO KT-36648 Captured variables not optimized in JVM_IR
-// TODO KT-36812 Generate proper lifetime intervals for local variables in JVM_IR
 
 fun test(): UInt {
     val c: UInt

compiler/testData/codegen/bytecodeText/localInitializationLVT/inlineClassVar.kt

@@ -1,6 +1,5 @@
 // IGNORE_BACKEND: JVM_IR
 // TODO KT-36648 Captured variables not optimized in JVM_IR
-// TODO KT-36812 Generate proper lifetime intervals for local variables in JVM_IR
 
 fun test(): UInt {
     var c: UInt

compiler/testData/codegen/bytecodeText/localInitializationLVT/lateinit.kt

@@ -1,6 +1,5 @@
 // IGNORE_BACKEND: JVM_IR
 // TODO KT-36648 Captured variables not optimized in JVM_IR
-// TODO KT-36812 Generate proper lifetime intervals for local variables in JVM_IR
 
 fun test(): Char {
     lateinit var c: Any

compiler/testData/codegen/bytecodeText/localInitializationLVT/run.kt

@@ -1,6 +1,5 @@
 // IGNORE_BACKEND: JVM_IR
 // TODO KT-36648 Captured variables not optimized in JVM_IR
-// TODO KT-36812 Generate proper lifetime intervals for local variables in JVM_IR
 
 fun test(): Char {
     val c: Char

compiler/testData/codegen/bytecodeText/localInitializationLVT/singleBlock.kt

@@ -1,6 +1,3 @@
-// IGNORE_BACKEND: JVM_IR
-// TODO KT-36812 Generate proper lifetime intervals for local variables in JVM_IR
-
 fun test(): Char {
     val c: Char
     val l = Any()

compiler/testData/codegen/bytecodeText/localInitializationLVT/singleBlockVar.kt

@@ -1,6 +1,3 @@
-// IGNORE_BACKEND: JVM_IR
-// TODO KT-36812 Generate proper lifetime intervals for local variables in JVM_IR
-
 fun test(): Char {
     var c: Char
     val l = Any()

compiler/testData/codegen/bytecodeText/localInitializationLVT/whenStatement.kt

@@ -1,6 +1,3 @@
-// IGNORE_BACKEND: JVM_IR
-// TODO KT-36812 Generate proper lifetime intervals for local variables in JVM_IR
-
 fun test(i: Int): Char {
     val c: Char
     when (i) {
@@ -20,4 +17,4 @@ fun test(i: Int): Char {
 }
 
 // 12 ISTORE 1
-// 1 LOCALVARIABLE c C L1 L16 1
+// 1 LOCALVARIABLE c C

compiler/testData/codegen/bytecodeText/localInitializationLVT/whenStatementVar.kt

@@ -1,6 +1,3 @@
-// IGNORE_BACKEND: JVM_IR
-// TODO KT-36812 Generate proper lifetime intervals for local variables in JVM_IR
-
 fun test(i: Int): Char {
     var c: Char
     when (i) {
@@ -20,4 +17,4 @@ fun test(i: Int): Char {
 }
 
 // 12 ISTORE 1
-// 1 LOCALVARIABLE c C L1 L16 1
+// 1 LOCALVARIABLE c C