Simplified Report

Denoising passes like Albedo and Normal are darkened when denoising is enabled when rendering using multiple devices.
This is most likely because the passes are scaled in-place during denoising and then scaled again in the pixel accessor.

Original report

System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: NVIDIA GeForce GTX 1050 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 512.77

Blender Version
Broken: version: 3.3.0, branch: master, commit date: 2022-09-06 15:39, hash: rB0759f671ce1f
Worked: 3.2.2

Short description of error
When rendering a scene using Cycles with the Denoise option enabled, the Denoising Normal and Denoising Albedo passes don't render correctly, the images correspondent to those passes are much darker than they should be.

Exact steps for others to reproduce the error

1. Open attached file or
   • Open Blender.
   • Delete the default cube.
   • Add an icosphere and set it shade smooth.
   • With the icosphere selected, go to the Shading workspace and add a material to it.
   • In Principled BSDF of the icosphere's material, go to base color and add a color (any color other than black, white or gray).
   • Go to Render Properties and select Cycles as render engine and GPU as Device.
   • In the Render section of the Render Properties, disable Denoise (it is enabled by default).
   • Go to View Layer Properties.
   • In the View Layer Properties, go to Passes section, Data sub-section and enable Denoising Data.
   • Go to the Compositing workspace and enable Use Nodes.
2. Render the image (Press F12).
3. In the Render Layers node, visualize the Denoising Normal and Denoising Albedo outputs (Ctrl+Shift+LeftClick with the Node Wrangler Add-on enabled).
4. In the Properties Editor Go to Sampling → Render and re-enable Denoise.
5. Render the image again (Press F12 or use the small buttom at the bottom right of the Render Layers node).
6. Repeat step 3.

By comparing the images from step 3 and step 6, the difference is clear, the images from step 6 (Cycles' denoise enabled) are much darker than they should be;
I tested with a more complex scene and noticed that the darker images do remove noise when used with the Denoise node in the compositor, so it may not be a big problem for Blender, but it may affect someone using other softwares in a pipeline, unfortunally, I can not tested it because I don't have acess to external compositing softwares, I only use Blender.

Thank you, have a nice day :).