feature/labelInLoop

[Yi2255]

According to feedback from #467, I reimplemented the feature of the label statement under the context of loop structure. The design ideas are as follows：

1. The operations BreakNested and ContinueNested are added. The two JS instructions both require a number input that represents the depth of the loop that the instruction wants to break or continue, and if the number exceeds the actual loop depth, then the actual loop depth is equal to depth %= actualLoopDepth.

2. In JSLifter, any loop structure has a begin and end block. For example, beginWhileLoopBody. Each time it is loaded, actualLoopDepth is incremented, and the start position of this loop in the overall code string is recorded. When endWhileLoop is loaded, actualLoopDepth is decremented, and the recorded position for the current loop is popped.

3. During the breakNested lifting process, the expected depth of the target loop to break is first determined using input % actualLoopDepth. Then, the starting position of the target loop is obtained from the recorded loop stack. Simultaneously, it is checked whether a label already exists at that position. If not, the label will be inserted, all subsequent loop starting positions are updated, and the position is marked as inserted. The continueNested process follows the same steps.

[saelo]

Thanks for working on this! First high-level round of feedback

[saelo]

Having the depth as input will be tricky, again because the mutator will change inputs around arbitrarily and you'll quickly get strings or objects or other stuff as depth. Instead, I'd recommend making the depth a property of this operation:

final class BreakNested: JsOperation {
    override var opcode: Opcode { .breakNested(self) }

    let depth: Int

    init(depth: Int) {
        ...
    }

[saelo]

We can then also let the OperationMutator mutate the depth property of these.

[Yi2255]

Your analysis has been very helpful to me. Thank you so much! I will complete the revisions as soon as possible.

[saelo]

Is my understanding correct that these can only be used inside loops? Or are they also usable outside of loops in certain circumstances?

If they must always be in a loop: maybe we should also call these LoopBreakNested or something like that to stay consistent with LoopBreak

If they can also appear elsewhere: should we drop the .loop context requirement?

[Yi2255]

Yes, these can only be used in loops. This is an inappropriate naming issue, and I will later rename it to LoopBreakNested and LoopContinueNested.

[Yi2255]

Hi @saelo, I have made improvements in the following three aspects based on your insightful feedback:

1. Rename label operation name to LoopBreakNested & LoopContinueNested;
2. Update implement of LoopBreakNested & LoopContinueNested JsOperation, made the depth a property of these.
3. Update operationMutator, mutate the depth property of these.