Re: [PATCH 5/5] x86_64: Add evex optimized bcmp implementation in bcmp-evex.S

[Noah Goldstein via Libc-alpha <libc-alpha@sourceware.org>]

On Mon, Sep 13, 2021 at 9:35 PM Carlos O'Donell <carlos@redhat.com> wrote:

> On 9/13/21 10:05 PM, Noah Goldstein wrote:
> > On Mon, Sep 13, 2021 at 8:18 PM Carlos O'Donell <carlos@redhat.com>
> wrote:
> >
> >> On 9/13/21 7:05 PM, Noah Goldstein via Libc-alpha wrote:
> >>> No bug. This commit adds new optimized bcmp implementation for evex.
> >>>
> >>> The primary optimizations are 1) skipping the logic to find the
> >>> difference of the first mismatched byte and 2) not updating src/dst
> >>> addresses as the non-equals logic does not need to be reused by
> >>> different areas.
> >>>
> >>> The entry alignment has been fixed at 64. In throughput sensitive
> >>> functions which bcmp can potentially be frontend loop performance is
> >>> important to opimized for. This is impossible/difficult to do/maintain
> >>> with only 16 byte fixed alignment.
> >>>
> >>> test-memcmp, test-bcmp, and test-wmemcmp are all passing.
> >>
> >> This series fails in the containerized 32-bit x86 CI/CD regression
> tester.
> >>
> >>
> https://patchwork.sourceware.org/project/glibc/patch/20210913230506.546749-5-goldstein.w.n@gmail.com/
> >
> >
> > Shoot.
>
> No worries! That's what the CI/CD system is there for :-)
>
> > AFAICT the first error is:
> > *** No rule to make target '/build/string/stamp.os', needed by
> > '/build/libc_pic.a'.
>
> I think a normal 32-bit x86 builds should show this issue.
>
> You need a gcc that accepts -m32.
>

Was able to get it with DJ's command.

>
> I minimally set:
> export CC="gcc -m32 -Wl,--build-id=none"
> export CXX="g++ -m32 -Wl,--build-id=none"
> export CFLAGS="-g -O2 -march=i686 -Wl,--build-id=none"
> export CXXFLAGS="-g -O2 -march=i686 -Wl,--build-id=none"
> export CPPFLAGS="-g -O2 -march=i686 -Wl,--build-id=none"
>
> Then build with --host.
>
> e.g.
>
> /home/carlos/src/glibc-work/configure --host i686-pc-linux-gnu CC=gcc -m32
> -Wl,--build-id=none CFLAGS=-g -O2 -march=i686 -Wl,--build-id=none
> CPPFLAGS=-g -O2 -march=i686 -Wl,--build-id=none CXX=g++ -m32
> -Wl,--build-id=none CXXFLAGS=-g -O2 -march=i686 -Wl,--build-id=none
> --prefix=/usr
> --with-headers=/home/carlos/build/glibc-headers-work-i686/include
> --with-selinux --disable-nss-crypt --enable-bind-now --enable-static-pie
> --enable-systemtap --enable-hardcoded-path-in-tests --enable-tunables=yes
> --enable-add-ons


Thanks for the help!


>


> > Also, does anyone know what make/configure commands I need to reproduce
> > this on a x86_64-Linux machine? The build log doesn't appear to have the
> command.
>
> DJ, Should the trybot log the configure step?
>
>
So I think I was able to fix the build by making a new file in
glibc/string/bcmp.c
and just having bcmp call memcmp

Is there another/better way to fix the build?  I don't think it's really
fair that every
arch other than x86_64 should have to pay an extra function call cost to
use bcmp.


> --
> Cheers,
> Carlos.
>
>