Remove unreachable instructions

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

@@ -573,11 +573,9 @@ class CoroutineTransformerMethodVisitor(
             return false
         }
 
-        val starts = methodNode.instructions.asSequence().filter {
+        return methodNode.instructions.asSequence().filter {
-            isBeforeSuspendMarker(it) &&
+            isBeforeSuspendMarker(it)
-                    cfg.getPredecessorsIndices(it).isNotEmpty() // Ignore unreachable start markers
+        }.mapNotNull { start ->
-        }.toList()
-        return starts.mapNotNull { start ->
             val ends = mutableSetOf<AbstractInsnNode>()
             if (collectSuspensionPointEnds(start, mutableSetOf(), ends)) return@mapNotNull null
             // Ignore suspension points, if the suspension call begin is alive and suspension call end is dead
@@ -586,7 +584,7 @@ class CoroutineTransformerMethodVisitor(
             // this is an exit point for the corresponding coroutine.
             val end = ends.find { isAfterSuspendMarker(it) } ?: return@mapNotNull null
             SuspensionPoint(start.previous, end)
-        }
+        }.toList()
     }
 
     private fun dropSuspensionMarkers(methodNode: MethodNode) {
@@ -983,7 +981,7 @@ private class MethodNodeExaminer(
         val typedFrames = basicAnalyser.frames
 
         val isReferenceMap = popsBeforeSafeUnitInstances
-            .map { it to (!isUnreachable(it.index(), sourceFrames) && typedFrames[it.index()]?.top()?.isReference == true) }
+            .map { it to (typedFrames[it.index()]?.top()?.isReference == true) }
             .toMap()
 
         for (pop in popsBeforeSafeUnitInstances) {
@@ -1008,8 +1006,6 @@ private class MethodNodeExaminer(
             val beginIndex = instructions.indexOf(suspensionPoint.suspensionCallBegin)
             val endIndex = instructions.indexOf(suspensionPoint.suspensionCallEnd)
 
-            if (isUnreachable(endIndex, sourceFrames)) return@all true
-
             val insideTryBlock = methodNode.tryCatchBlocks.any { block ->
                 val tryBlockStartIndex = instructions.indexOf(block.start)
                 val tryBlockEndIndex = instructions.indexOf(block.end)
@@ -1043,7 +1039,6 @@ private class MethodNodeExaminer(
             val insn = insns[index]
 
             if (insn.opcode == Opcodes.ARETURN && !insn.isAreturnAfterSafeUnitInstance()) {
-                if (isUnreachable(index, sourceFrames)) return@init null
                 return@init setOf(index)
             }
 
@@ -1215,10 +1210,6 @@ internal class IgnoringCopyOperationSourceInterpreter : SourceInterpreter(Opcode
     override fun copyOperation(insn: AbstractInsnNode?, value: SourceValue?) = value
 }
 
-// Check whether this instruction is unreachable, i.e. there is no path leading to this instruction
-internal fun <T : Value> isUnreachable(index: Int, sourceFrames: Array<out Frame<out T>?>): Boolean =
-    sourceFrames.size <= index || sourceFrames[index] == null
-
 private fun AbstractInsnNode?.isInvisibleInDebugVarInsn(methodNode: MethodNode): Boolean {
     val insns = methodNode.instructions
     val index = insns.indexOf(this)

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

@@ -121,6 +121,16 @@ internal class RedundantLocalsEliminationMethodTransformer(private val suspensio
             }
         }
 
+        // Remove unreachable instructions to simplify further analyses
+        for (index in frames.indices) {
+            if (frames[index] == null) {
+                val insn = methodNode.instructions[index]
+                if (insn !is LabelNode) {
+                    toDelete.add(insn)
+                }
+            }
+        }
+
         methodNode.instructions.removeAll(toDelete)
     }