> xor rbp,rbp /* xoring a value with itself = 0 */
Is this faster than a (const) mov ?
Is this faster than a (const) mov ?
"Also, I like how returning 0 is "xor eax, eax"."
https://news.ycombinator.com/item?id=13052503
That led to multiple replies on it.
Also, the reason it is "faster" is that the encoding is 1 byte, vs. 9 bytes (in 64 bit) for "mov rbp, 0" - roughly, 1 for "mov rbp,", 8 more for a 64 bit "0".
Another reason why it was faster was that the processor recognized it and avoided partial flags stalls after an "inc". But in 64-bit code you rarely have "inc" at all, so it matters less. On the other hand, a few years ago XOR had a false dependency on the register you're clearing; I'm not sure it is still that way on more recent processors.