On Tue, Sep 1, 2020 at 8:13 PM Jason A. Donenfeld <Jason@xxxxxxxxx> wrote: > operands are the same. Also, have you seen any measurable differences > when benching this? I can stick it into kbench9000 to see if you > haven't looked yet. On a Skylake server (Xeon Gold 5120), I'm unable to see any measurable difference with this, at all, no matter how much I median or mean or reduce noise by disabling interrupts. One thing that sticks out is that all the replacements of r8-r15 by their %r8d-r15d counterparts still have the REX prefix, as is necessary to access those registers. The only ones worth changing, then, are the legacy registers, and on a whole, this amounts to only 48 bytes of difference.
