In our case we're building some xcframeworks which contain all architectures (including visionOS btw)- excluding DriverKit. Prior to adding macros one xcframework takes 257.7 seconds (4.3 minutes) to build. After adding macros it takes 2004.5 seconds (33.4 minutes). This is a 7.76x increase. This is with one macro implemented in one location in code, so it's not related to how many times the macro is used.
This speed decrease makes the macros support currently unusable for us. Given that this is on some level just text substitution, this really should be solvable.
There's also a secondary issue, which because of the speed issue I don't really need to take it further at this point, but it's that tests do not support these macros for some reason when run from the command line. The tests work fine in the IDE. When at the command line it says:
Please file a bug at https://feedbackassistant.apple.com with this warning message and any useful information you can provide.
/Users/johnbushnell/Code/Kochava/Apple-KochavaSDK-Source/Apple-SwiftPackage-KochavaNetworking-Source/Sources/KochavaNetworking/Adapter.swift:494:9: external macro implementation type 'KochavaNetworkingMacrosMacros.ExecutionSynchronizeMacro' could not be found for macro 'let_execution_synchronize(executor:)'
This is running on the latest command line tools:
Xcode 15.2
Build version 15C500b