What happens at ARM64 function call level when Objective-C method is invoked?

Objective-C method calls are compiled into ARM64 registers-based function calls via objc_msgSend.

On ARM64, objc_msgSend is a highly optimized assembly function. 'self' is passed in x0, selector in x1, and arguments in subsequent registers. The function performs cache lookup and jumps directly to IMP using branch instructions. This avoids stack overhead in hot paths.