In theory that would work but compilers and toolchains are far too clever now and always liable to change, so there's no way to know that in the future it won't be optimised back into shortcutting and revealing the timings.

I think that’s still affected by speculative execution. The CPU will process the step ahead assuming that a[i] != b[i] while it is doing the a[i] XOR b[i] check.

So it’ll be faster if: most characters match, most characters don’t match or there are runs of matching characters.

Have a read of this: https://stackoverflow.com/questions/11227809/why-is-processi...