e4fc33adfc
The issue has been introduced in 7ceb4495c5 by missing implementation
of the is_noop() callback for the CPU processor.
While it was not noticeable perceptually, an exact floating point value
might have changed due to un-premultiplication+premultiplication.
The fix needs to be ported to the Blender 4.5 LTS.
Pull Request: https://projects.blender.org/blender/blender/pulls/143998