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 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.

AFAICT the first error is:
*** No rule to make target '/build/string/stamp.os', needed by
'/build/libc_pic.a'.

I saw that issue earlier when I was working on just supporting bcmp for the
first
commit:

[PATCH 1/5] x86_64: Add support for bcmp using sse2, sse4_1, avx2, and evex

So I think I missed/messed up something there regarding the necessary
changes
to the  Makefile/build infrastructure to support the change.

While it doesn't appear to be an issue on my local machine I left the
redirect in
string/memcmp.c:

https://sourceware.org/git/?p=glibc.git;a=blob;f=string/memcmp.c;h=9b46d7a905c8b7886f046b7660f63df10dc4573c;hb=HEAD#l360

But was one area where I didn't really know the right answer.


Does anyone know if there is anything special that needs to be done for the
32 bit
build when adding a new implementation?

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.

For my completely fresh build / testing I ran:

rm -rf /path/to/build/glibc; mkdir -p /path/to/build/glibc; (cd
/path/to/build/glibc/; unset LD_LIBRARY_PATH; /path/to/src/glibc/configure
--prefix=/usr; make --silent; make xcheck; make -r -C
/path/to/src/glibc/string/ objdir=`pwd` check; make -r -C
/path/to/src/glibc/wcsmbs/ objdir=`pwd` check)

which doesn't appear to have cut it.


>
> --
> Cheers,
> Carlos.
>
>