Bug Description

There is a significant performance drop using cloneDeep of lodash, it takes approximately 25-45 times longer to execute when running with Hermes on android.

• I have run gradle clean and confirmed this bug does not occur with JSC

Hermes version: hermes-engine: 0.5.1
React Native version (if any): 0.63.4
OS version (if any): Android 10 x86 Pixel 3 simulator
Platform (most likely one of arm64-v8a, armeabi-v7a, x86, x86_64): x86_64

Minimal reproducing repository

https://github.com/karol-bisztyga/hermes-repro
There are 2 commits:

• init - use it to test without Hermes
• with hermes - use it to test with Hermes

For reproducing this I used a randomly generated JSON file, which is here, it is a 1MB file(just FYI, you don't have to worry about this, it's hardcoded in the repro already).

Tests results

Running sample code from the repro provided I got following results(that stand for times of execution of doing JSON.parse, clondeDeep and both combined):

- no hermes:
{ parse: [ 32, 11, 16, 14, 17, 15, 14, 17, 14, 12 ],
      clone: [ 218, 209, 114, 122, 117, 114, 117, 123, 111, 118 ],
      parseClone: [ 235, 137, 141, 132, 125, 142, 131, 131, 141, 136 ] }
- with hermes:
{ parse: [ 24, 18, 22, 17, 17, 13, 18, 13, 18, 12 ],
      clone: [ 5667, 5318, 5500, 5395, 5576, 5760, 5553, 5349, 5669, 5455 ],
      parseClone: [ 5405, 5388, 5787, 5452, 5426, 5360, 5381, 5364, 5455, 5390 ] }

The Expected Behavior

Similar time of execution of clondeDeep with and without Hermes

Note

I didn't know how to categorize it so I went for the Bug, sorry if that's not the best way, I couldn't find a category for the performance drop.