Do not remove dead variables' LVT records

Also, extend liveness of alive variable to nearest suspension points
 #KT-44714

compiler/backend/src/org/jetbrains/kotlin/codegen/coroutines/CoroutineTransformerMethodVisitor.kt

@@ -1217,6 +1217,27 @@ private fun updateLvtAccordingToLiveness(method: MethodNode, isForNamedFunction:
     fun isAlive(insnIndex: Int, variableIndex: Int): Boolean =
         liveness[insnIndex].isAlive(variableIndex)
 
+    fun nextSuspensionPointLabel(insn: AbstractInsnNode): LabelNode {
+        val suspensionPoint =
+            InsnSequence(insn, method.instructions.last).firstOrNull { isBeforeSuspendMarker(it) } ?: method.instructions.last
+        return suspensionPoint as? LabelNode ?: suspensionPoint.findPreviousOrNull { it is LabelNode } as LabelNode
+    }
+
+    fun previousSuspensionPointLabel(insn: AbstractInsnNode): LabelNode {
+        val suspensionPoint =
+            InsnSequence(method.instructions.first, insn).lastOrNull { isAfterSuspendMarker(it) } ?: method.instructions.first
+        return suspensionPoint as? LabelNode ?: suspensionPoint.findNextOrNull { it is LabelNode } as LabelNode
+    }
+
+    fun min(a: LabelNode, b: LabelNode): LabelNode =
+        if (method.instructions.indexOf(a) < method.instructions.indexOf(b)) a else b
+
+    fun max(a: LabelNode, b: LabelNode): LabelNode =
+        if (method.instructions.indexOf(a) < method.instructions.indexOf(b)) b else a
+
+    fun containsSuspensionPoint(a: LabelNode, b: LabelNode): Boolean =
+        InsnSequence(min(a, b), max(a, b)).none { isBeforeSuspendMarker(it) }
+
     val oldLvt = arrayListOf<LocalVariableNode>()
     for (record in method.localVariables) {
         oldLvt += record
@@ -1231,29 +1252,43 @@ private fun updateLvtAccordingToLiveness(method: MethodNode, isForNamedFunction:
         for (insnIndex in 0 until (method.instructions.size() - 1)) {
             val insn = method.instructions[insnIndex]
             if (!isAlive(insnIndex, variableIndex) && isAlive(insnIndex + 1, variableIndex)) {
-                startLabel = insn as? LabelNode ?: insn.findNextOrNull { it is LabelNode } as? LabelNode
+                val lvtRecord = oldLvt.findRecord(insnIndex, variableIndex) ?: continue
+                startLabel = max(lvtRecord.start, previousSuspensionPointLabel(insn))
             }
             if (isAlive(insnIndex, variableIndex) && !isAlive(insnIndex + 1, variableIndex)) {
                 // No variable in LVT -> do not add one
                 val lvtRecord = oldLvt.findRecord(insnIndex, variableIndex) ?: continue
                 if (lvtRecord.name == CONTINUATION_VARIABLE_NAME) continue
-                val endLabel = insn as? LabelNode ?: insn.findNextOrNull { it is LabelNode } as? LabelNode ?: continue
+                // Extend lvt record to the next suspension point
+                val endLabel = min(lvtRecord.end, nextSuspensionPointLabel(insn))
                 // startLabel can be null in case of parameters
                 @Suppress("NAME_SHADOWING") val startLabel = startLabel ?: lvtRecord.start
                 // Attempt to extend existing local variable node corresponding to the record in
                 // the original local variable table.
-                var recordToExtend: LocalVariableNode? = oldLvtNodeToLatestNewLvtNode[lvtRecord]
+                val recordToExtend: LocalVariableNode? = oldLvtNodeToLatestNewLvtNode[lvtRecord]
-                if (recordToExtend != null && InsnSequence(recordToExtend.end, startLabel).none { isBeforeSuspendMarker(it) }) {
+                if (recordToExtend != null && containsSuspensionPoint(recordToExtend.end, startLabel)) {
                     recordToExtend.end = endLabel
                 } else {
                     val node = LocalVariableNode(lvtRecord.name, lvtRecord.desc, lvtRecord.signature, startLabel, endLabel, lvtRecord.index)
-                    method.localVariables.add(node)
+                    if (lvtRecord !in oldLvtNodeToLatestNewLvtNode) {
+                        method.localVariables.add(node)
+                    }
                     oldLvtNodeToLatestNewLvtNode[lvtRecord] = node
                 }
             }
         }
     }
 
+    val deadVariables = arrayListOf<Int>()
+    outer@for (variableIndex in start until method.maxLocals) {
+        if (oldLvt.none { it.index == variableIndex }) continue
+        if (oldLvt.none { it.index == variableIndex }) continue
+        for (insnIndex in 0 until (method.instructions.size() - 1)) {
+            if (isAlive(insnIndex, variableIndex)) continue@outer
+        }
+        deadVariables += variableIndex
+    }
+
     for (variable in oldLvt) {
         // $continuation and $result are dead, but they are used by debugger, as well as fake inliner variables
         // For example, $continuation is used to create async stack trace
@@ -1262,10 +1297,26 @@ private fun updateLvtAccordingToLiveness(method: MethodNode, isForNamedFunction:
             isFakeLocalVariableForInline(variable.name)
         ) {
             method.localVariables.add(variable)
+            continue
         }
         // this acts like $continuation for lambdas. For example, it is used by debugger to create async stack trace. Keep it.
         if (variable.name == "this" && !isForNamedFunction) {
             method.localVariables.add(variable)
+            continue
+        }
+
+        // Shrink LVT records of dead variables to the next suspension point
+        if (variable.index in deadVariables) {
+            method.localVariables.add(
+                LocalVariableNode(
+                    variable.name,
+                    variable.desc,
+                    variable.signature,
+                    variable.start,
+                    nextSuspensionPointLabel(variable.start),
+                    variable.index
+                )
+            )
         }
     }
 }

compiler/testData/checkLocalVariablesTable/suspendFunctionDeadVariables.kt

@@ -0,0 +1,14 @@
+// WITH_RUNTIME
+
+suspend fun dummy() {}
+
+suspend fun test() {
+    dummy()
+    val a = 0
+}
+
+// METHOD : SuspendFunctionDeadVariablesKt.test(Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
+
+// VARIABLE : NAME=a TYPE=I INDEX=1
+// VARIABLE : NAME=$continuation TYPE=Lkotlin/coroutines/Continuation; INDEX=3
+// VARIABLE : NAME=$result TYPE=Ljava/lang/Object; INDEX=2

compiler/testData/codegen/bytecodeText/coroutines/debug/localVariableCorrectLabel.kt

@@ -15,7 +15,7 @@ fun main(args: Array<String>) {
 suspend fun SequenceScope<Int>.awaitSeq(): Int = 42
 
 
-// 1 LOCALVARIABLE a I L[0-9]+ L18
+// 1 LOCALVARIABLE a I L[0-9]+ L4
 
 /* TODO: JVM_IR does not generate LINENUMBER at the end of the lambda */
 // JVM_TEMPLATES

compiler/testData/debug/localVariables/suspend/completion/nonStaticStateMachine.kt

@@ -36,6 +36,6 @@ suspend fun box() {
 // test.kt:5 foo: $completion:kotlin.coroutines.Continuation=A$foo1$1
 // test.kt:8 foo1: $continuation:kotlin.coroutines.Continuation=A$foo1$1, $result:java.lang.Object=null, l:long=42:long
 // test.kt:9 foo1: $continuation:kotlin.coroutines.Continuation=A$foo1$1, $result:java.lang.Object=null, l:long=42:long
-// test.kt:10 foo1: $continuation:kotlin.coroutines.Continuation=A$foo1$1, $result:java.lang.Object=null
+// test.kt:10 foo1: $continuation:kotlin.coroutines.Continuation=A$foo1$1, $result:java.lang.Object=null, l:long=42:long, dead:long=42:long
 // test.kt:14 box: $completion:kotlin.coroutines.Continuation=helpers.ResultContinuation
 // test.kt:15 box: $completion:kotlin.coroutines.Continuation=helpers.ResultContinuation

compiler/testData/debug/localVariables/suspend/completion/staticStateMachine.kt

@@ -32,6 +32,6 @@ suspend fun box() {
 // test.kt:4 foo: $completion:kotlin.coroutines.Continuation=TestKt$foo1$1
 // test.kt:7 foo1: $continuation:kotlin.coroutines.Continuation=TestKt$foo1$1, $result:java.lang.Object=null, l:long=42:long
 // test.kt:8 foo1: $continuation:kotlin.coroutines.Continuation=TestKt$foo1$1, $result:java.lang.Object=null, l:long=42:long
-// test.kt:9 foo1: $continuation:kotlin.coroutines.Continuation=TestKt$foo1$1, $result:java.lang.Object=null
+// test.kt:9 foo1: $continuation:kotlin.coroutines.Continuation=TestKt$foo1$1, $result:java.lang.Object=null, l:long=42:long, dead:long=42:long
 // test.kt:12 box: $completion:kotlin.coroutines.Continuation=helpers.ResultContinuation
 // test.kt:13 box: $completion:kotlin.coroutines.Continuation=helpers.ResultContinuation

compiler/testData/debug/localVariables/suspend/completion/staticStateMachineReceiver.kt

@@ -36,6 +36,6 @@ suspend fun box() {
 // test.kt:6 foo: $this$foo:A=A, $completion:kotlin.coroutines.Continuation=TestKt$foo1$1
 // test.kt:9 foo1: $continuation:kotlin.coroutines.Continuation=TestKt$foo1$1, $result:java.lang.Object=null, l:long=42:long
 // test.kt:10 foo1: $continuation:kotlin.coroutines.Continuation=TestKt$foo1$1, $result:java.lang.Object=null, l:long=42:long
-// test.kt:11 foo1: $continuation:kotlin.coroutines.Continuation=TestKt$foo1$1, $result:java.lang.Object=null
+// test.kt:11 foo1: $continuation:kotlin.coroutines.Continuation=TestKt$foo1$1, $result:java.lang.Object=null, l:long=42:long, dead:long=42:long
 // test.kt:14 box: $completion:kotlin.coroutines.Continuation=helpers.ResultContinuation
 // test.kt:15 box: $completion:kotlin.coroutines.Continuation=helpers.ResultContinuation

compiler/testData/debug/localVariables/suspend/localsStateMachineTransform.kt

@@ -31,19 +31,19 @@ suspend fun box() {
 // test.kt:11 box: $continuation:kotlin.coroutines.Continuation=TestKt$box$1, $result:java.lang.Object=null, x:int=0:int
 // test.kt:5 f: x:int=0:int
 // test.kt:11 box: $continuation:kotlin.coroutines.Continuation=TestKt$box$1, $result:java.lang.Object=null, x:int=0:int
-// test.kt:10 box: $continuation:kotlin.coroutines.Continuation=TestKt$box$1, $result:java.lang.Object=null
+// test.kt:10 box: $continuation:kotlin.coroutines.Continuation=TestKt$box$1, $result:java.lang.Object=null, x:int=0:int
 // test.kt:11 box: $continuation:kotlin.coroutines.Continuation=TestKt$box$1, $result:java.lang.Object=null, x:int=1:int
 // test.kt:5 f: x:int=1:int
 // test.kt:11 box: $continuation:kotlin.coroutines.Continuation=TestKt$box$1, $result:java.lang.Object=null, x:int=1:int
-// test.kt:10 box: $continuation:kotlin.coroutines.Continuation=TestKt$box$1, $result:java.lang.Object=null
+// test.kt:10 box: $continuation:kotlin.coroutines.Continuation=TestKt$box$1, $result:java.lang.Object=null, x:int=1:int
 // test.kt:14 box: $continuation:kotlin.coroutines.Continuation=TestKt$box$1, $result:java.lang.Object=null
 // test.kt:15 box: $continuation:kotlin.coroutines.Continuation=TestKt$box$1, $result:java.lang.Object=null
 // test.kt:16 box: $continuation:kotlin.coroutines.Continuation=TestKt$box$1, $result:java.lang.Object=null, x:int=0:int
 // test.kt:5 f: x:int=0:int
 // test.kt:16 box: $continuation:kotlin.coroutines.Continuation=TestKt$box$1, $result:java.lang.Object=null, x:int=0:int
-// test.kt:15 box: $continuation:kotlin.coroutines.Continuation=TestKt$box$1, $result:java.lang.Object=null
+// test.kt:15 box: $continuation:kotlin.coroutines.Continuation=TestKt$box$1, $result:java.lang.Object=null, x:int=0:int
 // test.kt:16 box: $continuation:kotlin.coroutines.Continuation=TestKt$box$1, $result:java.lang.Object=null, x:int=1:int
 // test.kt:5 f: x:int=1:int
 // test.kt:16 box: $continuation:kotlin.coroutines.Continuation=TestKt$box$1, $result:java.lang.Object=null, x:int=1:int
-// test.kt:15 box: $continuation:kotlin.coroutines.Continuation=TestKt$box$1, $result:java.lang.Object=null
+// test.kt:15 box: $continuation:kotlin.coroutines.Continuation=TestKt$box$1, $result:java.lang.Object=null, x:int=1:int
 // test.kt:18 box: $continuation:kotlin.coroutines.Continuation=TestKt$box$1, $result:java.lang.Object=null

compiler/testData/debug/localVariables/suspend/underscoreNames.kt

@@ -45,7 +45,7 @@ suspend fun box() = foo(A()) { (x_param, _, y_param) ->
 // test.kt:12 invokeSuspend: $result:java.lang.Object=kotlin.Unit, $dstr$x_param$_u24__u24$y_param:A=A, x_param:java.lang.String="O":java.lang.String
 
 // LOCAL VARIABLES
-// test.kt:13 invokeSuspend: $result:java.lang.Object=kotlin.Unit, x_param:java.lang.String="O":java.lang.String, y_param:java.lang.String="K":java.lang.String
+// test.kt:13 invokeSuspend: $result:java.lang.Object=kotlin.Unit, $dstr$x_param$_u24__u24$y_param:A=A, x_param:java.lang.String="O":java.lang.String, y_param:java.lang.String="K":java.lang.String
 
 // LOCAL VARIABLES JVM
 // test.kt:-1 invoke:

compiler/tests-gen/org/jetbrains/kotlin/codegen/CheckLocalVariablesTableTestGenerated.java

@@ -80,6 +80,11 @@ public class CheckLocalVariablesTableTestGenerated extends AbstractCheckLocalVar
         runTest("compiler/testData/checkLocalVariablesTable/objectInLocalPropertyDelegate.kt");
     }
 
+    @TestMetadata("suspendFunctionDeadVariables.kt")
+    public void testSuspendFunctionDeadVariables() throws Exception {
+        runTest("compiler/testData/checkLocalVariablesTable/suspendFunctionDeadVariables.kt");
+    }
+
     @TestMetadata("underscoreNames.kt")
     public void testUnderscoreNames() throws Exception {
         runTest("compiler/testData/checkLocalVariablesTable/underscoreNames.kt");

compiler/tests-gen/org/jetbrains/kotlin/codegen/ir/IrCheckLocalVariablesTableTestGenerated.java

@@ -80,6 +80,11 @@ public class IrCheckLocalVariablesTableTestGenerated extends AbstractIrCheckLoca
         runTest("compiler/testData/checkLocalVariablesTable/objectInLocalPropertyDelegate.kt");
     }
 
+    @TestMetadata("suspendFunctionDeadVariables.kt")
+    public void testSuspendFunctionDeadVariables() throws Exception {
+        runTest("compiler/testData/checkLocalVariablesTable/suspendFunctionDeadVariables.kt");
+    }
+
     @TestMetadata("underscoreNames.kt")
     public void testUnderscoreNames() throws Exception {
         runTest("compiler/testData/checkLocalVariablesTable/underscoreNames.kt");