On Tue, Sep 1, 2020 at 8:13 PM Jason A. Donenfeld <ja...@zx2c4.com> 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.

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