* Re: [PATCH] x86-64: Add Avoid_Short_Distance_REP_MOVSB
[not found] ` <CAFUsyfL-xLHMYw_4qHCsJJRL75Y7UKZ7Tx+Mhf4KoxKQ=XzYAg@mail.gmail.com>
@ 2022-04-28 0:15 ` Sunil Pandey
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From: Sunil Pandey @ 2022-04-28 0:15 UTC (permalink / raw)
To: Noah Goldstein, libc-stable; +Cc: Alexey Tourbin, GNU C Library
On Fri, Aug 27, 2021 at 7:58 PM Noah Goldstein via Libc-alpha
<libc-alpha@sourceware.org> wrote:
>
> On Fri, Aug 27, 2021 at 8:28 PM Alexey Tourbin via Libc-alpha <
> libc-alpha@sourceware.org> wrote:
>
> > On Mon, Jul 26, 2021 at 3:03 PM H.J. Lu via Libc-alpha
> > <libc-alpha@sourceware.org> wrote:
> > > --- a/sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S
> > > +++ b/sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S
> > > @@ -325,12 +325,16 @@ L(movsb):
> > > /* Avoid slow backward REP MOVSB. */
> > > jb L(more_8x_vec_backward)
> > > # if AVOID_SHORT_DISTANCE_REP_MOVSB
> > > + andl $X86_STRING_CONTROL_AVOID_SHORT_DISTANCE_REP_MOVSB,
> > __x86_string_control(%rip)
> > > + jz 3f
> > > movq %rdi, %rcx
> > > subq %rsi, %rcx
> > > jmp 2f
> > > # endif
> > > 1:
> > > # if AVOID_SHORT_DISTANCE_REP_MOVSB
> > > + andl $X86_STRING_CONTROL_AVOID_SHORT_DISTANCE_REP_MOVSB,
> > __x86_string_control(%rip)
> > > + jz 3f
> > > movq %rsi, %rcx
> > > subq %rdi, %rcx
> > > 2:
> >
> > Why "andl" rather than "testl"?
> >
>
> +1. I missed that before.
>
> My patches: [PATCH 5/5] X86-64: Optimize memmove-vec-unaligned-erms.S
>
> uses `testl` instead. Although my patch might not be checked in (and it may
> be a
> while) as we are still looking into the causes of the slowdown.
I would like to backport this patch to release branches.
Any comments or objections?
--Sunil
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2022-04-28 0:15 ` [PATCH] x86-64: Add Avoid_Short_Distance_REP_MOVSB Sunil Pandey
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