Any references of the bug report to show here?

It looks like this issue was generally introduced with Xcode 13. On my side the issue was latent in my project as one of my units didn't have to build with Xcode 13. As soon as the build folder was cleaned, the issue happened. I also have to release for iOS15, but can't. So far no workaround is available or communicated. Should one have a workaround, please go ahead.

Xcode 13.2 RC fixes the issue in 2 separate projects (iOS/WatchOS). Hope this works for you all!

I do confirm: Version 13.2.1 (13C100) does not resolve my latest issues in complex project. Compile time is extreme and memory consumption is still > 40 GB!

Turning off canvas prevents to run in this situation, i.e. background activities do not lither the memory and lead to the experienced misbehaviour. However, latest when it come to compile the swift module causing the issue, the problem will occur. Forcing quit of 'swift-frontend' or 'SourceKitService' before starting a build activity helps doing some housekeeping and getting 'faster' through build process. However, be patient. my 32GB RAM and additional swap gets consumed by a simple swift module modification. Hope this is coming to an end soon.

Looks like the issues are all fixed in my case in Version 13.3 beta (13E5086k). They persisted eventhough Apple brought some 'intermediate' fix, not resolving all issues. I hope the fix is now persistent.