What does GCC_FAST_OBJC_DISPATCH "Accelerated Objective-C Dispatch" actually do (or used to do)? [duplicate]

Question

For years I have seen this in Xcode's build settings list but never gotten round to researching what it does. Today I tried to do so and found Google is highly lacking in any info on the topic. Can any Objective-C veterans (I'm guessing of the late PPC era) shed any light on what this setting does (or did do)?

Answer 1

There's a Greg Parker reply here:

Accelerated Objective-C dispatch on PPC is faster because it avoids the dyld stub (which is otherwise used for all cross-library calls). On i386 the dyld stub is much faster than the ppc equivalent, so we didn’t bother doing extra work to bypass it.

https://www.mikeash.com/pyblog/performance-comparisons-of-common-operations.html#comment-63429be30b1123e8a78b7b37bbeb10fe