# Friday Q&A 2017-06-30: Dissecting objc\_msgSend on ARM64

DevFeed: [Friday Q&A 2017-06-30: Dissecting objc\_msgSend on ARM64](<https://devfeed.tech/articles/friday-q-a-2017-06-30-dissecting-objc-msgsend-on-arm64-30617.md>)

Original publisher: [Read original article](<http://www.mikeash.com/pyblog/friday-qa-2017-06-30-dissecting-objc_msgsend-on-arm64.html>)

Author: Mike Ash

Published: 2017-07-01T04:23:00Z

Content type: article

Language: en

Sources: [Mike Ash](<https://devfeed.tech/sources/mike-ash.md>)

Topics: [Objective-C](<https://devfeed.tech/topics/objective-c.md>), [Assembly](<https://devfeed.tech/topics/assembly.md>), [Cache](<https://devfeed.tech/topics/cache.md>), [Code](<https://devfeed.tech/topics/code.md>), [implementation](<https://devfeed.tech/topics/implementation.md>)

Tags: [article](<https://devfeed.tech/tags/article.md>), [assembly](<https://devfeed.tech/tags/assembly.md>), [cache](<https://devfeed.tech/tags/cache.md>), [code](<https://devfeed.tech/tags/code.md>), [implementation](<https://devfeed.tech/tags/implementation.md>), [objective-c](<https://devfeed.tech/tags/objective-c.md>)

## AI overview

This article explains how Objective-C message dispatch works in the ARM64 implementation of objc_msgSend, including method lookup, caching, and the division between fast and slow paths.

## Source excerpt

We're back! During the week of WWDC, I spoke at CocoaConf Next Door, and one of my talks involved a dissection of objc_msgSend's ARM64 implementation. I thought that turning it into an article would make for a nice return to blogging for Friday Q&A. (Read More)