Fastest Inverse Square Root on iPhone

Question

I\'m working on an iPhone app that involves certain physics calculations that are done thousands of times per second. I am working on optimizing the code to improve the fra

Answer 1

https://code.google.com/p/math-neon/source/browse/trunk/math_sqrtf.c <- there's a neon implementation of invsqrt there, you should be able to copy the assembly bit as-is

Answer 2

The accepted answer of the question you've linked already provides the answer, but doesn't spell it out:

#import <arm_neon.h>

void foo() {
    float32x2_t inverseSqrt = vrsqrte_f32(someFloat);
}

Header and function are already provided by the iOS SDK.