System Information
Operating system: Linux-5.14.0-4-amd64-x86_64-with-glibc2.32 64 Bits
Graphics card: NVIDIA GeForce RTX 3090/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 495.44

Blender Version
Broken version: 3.1.0 Alpha, branch: master, commit date: 2021-11-12 03:57, hash: rB1e1c87000150 and presumably Blender 3.0
Worked: Prior to rB440a3475b8f5: Cycles: Improve OptiX denoising with dark images and fix crash when denoiser is…

Short description of error
When rendering with a high sample count with the Albedo auxiliary pass enabled in specific scenes, some artifacts can occur. This issue was introduced by rB440a3475b8f5: Cycles: Improve OptiX denoising with dark images and fix crash when denoiser is… based on my bisecting. Here are some images showing what it looks like:

Prior to rB440a3475b8f5	After rB440a3475b8f5

Exact steps for others to reproduce the error

Option 1:

1. Download the attached scene and render the scene with a OptiX denoiser compatible device. (Either viewport rendering or final render works). If you use viewport rendering, you will notice the artifacts start to appear at high sample counts. With Adaptive Sampling on the issue doesn't appear to occur due to low sample counts.

Option 2:

1. Create a new .blend file and change the render engine to Cycles.
2. Disable Adaptive Sampling and enable the OptiX denoiser with the Albedo auxiliary pass in the relevant rendering mode (viewport or final render). It's important to disable the Adaptive Sampling here as this issue only appears to occur at high sample counts which Adaptive Sampling doesn't allow in simple scenes.
3. Change the World background to a Sky Texture.
4. Place the camera/view underneath the default cube and look up at it. Render the scene and once you reach a high sample count the issue will start to appear. It starts to appear at 1024 samples for me, but gets significantly more noticeable up to 4096 samples.