Does rewriting memcpy/memcmp/… with SIMD instructions make sense?

Question

Does rewriting memcpy/memcmp/... with SIMD instructions make sense in a large scale software?

If so, why doesn\'t GCC generate SIMD instructions for these library functi

Answer 1

Yes, these functions are much faster with SSE instructions. It would be nice if your runtime library/compiler instrinsics would include optimized versions, but that doesn't seem to be pervasive.

I have a custom SIMD memchr which is a hell-of-a-lot faster than the library version. Especially when I'm finding the first of 2 or 3 characters (example, I want to know if there's an equation in this line of text, I search for the first of =, \n, \r).

On the other hand, the library functions are well tested, so it's only worth writing your own if you call them a lot and a profiler shows they're a significant fraction of your CPU time.