Prerequisites:
You'll need a Mac M1 Apple Silicon machine and Arm64-based Editor installed.

Steps to repro:
1. Download the attached project and open "Sponza" scene on the macOS with Apple Silicon architecture;
2. In the Preferences window (Unity>Preferences>GI Cache) press Clean Cache button;
3. Drag and drop "SponzaLightingDay" scene to the Hierarchy;
4. In the Hierarchy double-click on the SponzaLightingDay scene to make it active scene;
5. In the Lighting window (Window>Rendering>Lighting) press Generate Lighting button;
6. Wait until the GI baking is completed and observe Scene and Game views.

Expected result:
The scene is rendered smoothly without artifacts.

Actual result:
There are various artifacts around the scene geometry after baking GI. See attached screenshots.

Notes:
- Reproducible in Version 2021.2.0a20;
- Reproducible only on Apple Silicon machine; could not reproduce on the Intel based Mac machine or on Windows;
- Not reproducible when using only A-Trous filtering;
- Not reproducible when using only Gaussian filtering;
- The artifacts shown on the screeshots might look different while reproducing the case on another machine or even between GI rebakes; please pay attention to the rendering of the scene's columns and arcs;
- The issue might not reproduce consistently; if it doesn't try reopening the project and rebaking the lighting.