There's some good info on that here: "Dissecting objc_msgSend on ARM64" https://www.mikeash.com/pyblog/friday-qa-2017-06-30-dissecting-objc_msgsend-on-arm64.ht

There's some good info on that here: "Dissecting objc_msgSend on ARM64" https://www.mikeash.com/pyblog/friday-qa-2017-06-30-dissecting-objc_msgsend-on-arm64.html https://www.mikeash.com/pyblog/friday-qa-2017-06-30-dissecti... "Let's Build objc_msgSend" https://www.mikeash.com/pyblog/friday-qa-2012-11-16-lets-build-objc_msgsend.html https://www.mikeash.com/pyblog/friday-qa-2012-11-16-lets-bui... There's also the "Illustrated history of objc_msgSend", although it appears a bit dated, it has some nice commentary on the evolution of this very performance-critical part of the objective-c runtime: http://sealiesoftware.com/msg/index.html http://sealiesoftware.com/msg/index.html