Compress unused slows down with deeply nested conditions

[dgreif]

Describe the bug

I'm working on updating SWC (from 1.2.205 to 1.3.4) and noticed that the latest version is very slow when trying to compress deeply nested conditions. We are using peggy.js which can quickly generate some very deep nesting. As the nesting approaches a depth of ~20, compression seems to slow down exponentially, and is on the order of many seconds even for a relatively small file size.

I was able to recreate the issue with some very basic peggy files - see https://github.com/dgreif/peggy-swc

The "large" file is only 600 lines long, but has over 20 levels of nesting here. This file takes ~20 seconds to compress. If I set compress.unused = false, it is almost instant.

I believe this is a duplicate of #5470, but that issue was closed because they were unable to provide a reproduction. I believe they were also using peggy, though they did not explicitly say so. They were also using deno, but I'm using Node.js.

Input code

No response

Config

{
  "$schema": "https://json.schemastore.org/swcrc",
  "minify": true,
  "jsc": {
    "minify": {
      "compress": {
        "unused": true
      },
      "mangle": true
    }
  }
}

Playground link

No response

Expected behavior

SWC is blazing fast with all of our other code. I would expect it to handle deeply nested conditional statements with similar speed.

Actual behavior

No response

Version

1.3.4

Additional context

No response

[kdy1]

I think the new DCE is the cause, although bisecting is required to verify it

[kdy1]

Okay it was a correct guess

[swc-bot]

This closed issue has been automatically locked because it had no new activity for a month. If you are running into a similar issue, please create a new issue with the steps to reproduce. Thank you.