Re: x86 copy performance regression

From: Linus Torvalds
Date: Fri May 26 2023 - 13:00:47 EST

On Fri, May 26, 2023 at 9:56 AM Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
> Ahh, I tested it in an allmodconfig build, but only building that one
> file, and not trying to link it. And gas was apparent;y perfectly
> happy just leaving that undefined feature as a relocation.

Oh, never mind. Even with that fixed, objtool is very unhappy about my
hack, because it knows about short jumps, and despite me encoding it
as a sequence of bytes, objtool will just decode it anyway and say
"that's not right".

Grr, I tried so hard to get the exact asm I wanted, but our
sanity-checking catches my cleverness and stops me in my tracks.

Let me go look at it some more. I *really* didn't want to make the
code worse for ERSM.