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Do not remove dead variables' LVT records

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Also, extend liveness of alive variable to nearest suspension points
 #KT-44714
This commit is contained in:
Ilmir Usmanov
2021-03-01 22:30:20 +01:00
parent ee11202db5
commit e17b7f01b6
10 changed files with 89 additions and 14 deletions
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compiler/backend/src/org/jetbrains/kotlin/codegen/coroutines/CoroutineTransformerMethodVisitor.kt
+56 -5
View File
@@ -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]
if (recordToExtend != null && InsnSequence(recordToExtend.end, startLabel).none { isBeforeSuspendMarker(it) }) {
val recordToExtend: LocalVariableNode? = oldLvtNodeToLatestNewLvtNode[lvtRecord]
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
)
)
}
}
}