Steps to reproduce:
1) Download attached project 'ParallaxCloudSystem-1.zip' and open in Unity
2) Switch platform to Android
3) Build and run on a device with Mono2x Scripting backend
Check FPS on the screen
4) Build and run on a device with IL2CPP Scripting backend
Note that fps much lower than Mono2x

Expected result: Fps should be stable and same as Mono2x
Actual result: FPS is much lower than Mono2x

Reproduced with:
5.3.6p7, 5.4.1p4, 5.5.0b7