To Reproduce:

1. Build the attached project (761024_SimpleReproProject.zip) on Unity 5.4, 5.3 & 5.1.
2. Observe that 'Fishlabs/GroundShader' is much slower on 5.4
(thee difference is more noticeable on A7 (tested mini 2 & Air 1) devices),
GPU frametimes:

--------5.1.4f1 | 5.3.1p2 | 5.4.0b2
iPad Air 1 - 5.3ms | 6.3ms | 14.9ms
iPhone 6s - 1.7ms | 1.3ms | 2.7ms

The only thing that seems to have been changed by the auto updater, when importing to 5.4:
// Upgrade NOTE: replaced '_Object2World' with 'unity_ObjectToWorld'

This can also be reproduced with other shader in 'Fishlabs' in the smaller repro project or using the full user project.

Tested with:

Version 5.4.0b2 (b1537386f494)
Sun, 10 Jan 2016 21:35:42 GMT
Branch: trunk