Re: [PATCH v5 00/17] Improve generic string routines

[Noah Goldstein <goldstein.w.n@gmail.com>]

On Thu, Jan 5, 2023 at 1:56 PM Adhemerval Zanella Netto via Libc-alpha
<libc-alpha@sourceware.org> wrote:
>
> Unfortunately no one worked on reviewing it.  It would be good to have
> it for 2.37, although I think it is too late.  However, since most
> architectures do use arch-specific routines, I think the possible disruption
> of using this patchset should be minimal.

I can start reviewing this. Not sure I can do all the arch headers but
can get up
to 11/17.
>
> On 05/12/22 14:07, Xi Ruoyao wrote:
> > Hi,
> >
> > Any status update on this series?
> >
> > On Mon, 2022-09-19 at 16:59 -0300, Adhemerval Zanella via Libc-alpha
> > wrote:
> >> It is done by:
> >>
> >>   1. parametrizing the internal routines (for instance the find zero
> >>      in a word) so each architecture can reimplement without the need
> >>      to reimplement the whole routine.
> >>
> >>   2. vectorizing more string implementations (for instance strcpy
> >>      and strcmp).
> >>
> >>   3. Change some implementations to use already possible optimized
> >>      ones (for instance strnlen).  It makes new ports to focus on
> >>      only provide optimized implementation of a hardful symbols
> >>      (for instance memchr) and make its improvement to be used in
> >>      a larger set of routines.
> >>
> >> For the rest of #5806 I think we can handle them later and if
> >> performance of generic implementation is closer I think it is better
> >> to just remove old assembly implementations.
> >>
> >> I also checked on x86_64-linux-gnu, i686-linux-gnu, powerpc-linux-gnu,
> >> and powerpc64-linux-gnu by removing the arch-specific assembly
> >> implementation and disabling multiarch (it covers both LE and BE
> >> for 64 and 32 bits). I also checked the string routines on alpha,
> >> hppa,
> >> and sh.
> >>
> >> Changes since v4:
> >>   * Removed __clz and __ctz in favor of count_leading_zero and
> >>     count_trailing_zeros from longlong.h.
> >>   * Use repeat_bytes more often.
> >>   * Added a comment on strcmp final_cmp on why index_first_zero_ne can
> >>     not be used.
> >>
> >> Changes since v3:
> >>   * Rebased against master.
> >>   * Dropped strcpy optimization.
> >>   * Refactor strcmp implementation.
> >>   * Some minor changes in comments.
> >>
> >> Changes since v2:
> >>   * Move string-fz{a,b,i} to its own patch.
> >>   * Add a inline implementation for __builtin_c{l,t}z to avoid using
> >>     compiler provided symbols.
> >>   * Add a new header, string-maskoff.h, to handle unaligned accesses
> >>     on some implementation.
> >>   * Fixed strcmp on LE machines.
> >>   * Added a unaligned strcpy variant for architecture that define
> >>     _STRING_ARCH_unaligned.
> >>   * Add SH string-fzb.h (which uses cmp/str instruction to find
> >>     a zero in word).
> >>
> >> Changes since v1:
> >>   * Marked ChangeLog entries with [BZ #5806], as appropriate.
> >>   * Reorganized the headers, so that armv6t2 and power6 need override
> >>     as little as possible to use their (integer) zero detection insns.
> >>   * Hopefully fixed all of the coding style issues.
> >>   * Adjusted the memrchr algorithm as discussed.
> >>   * Replaced the #ifdef STRRCHR etc that are used by the multiarch
> >>   * files.
> >>   * Tested on i386, i686, x86_64 (verified this is unused), ppc64,
> >>     ppc64le --with-cpu=power8 (to use power6 in multiarch), armv7,
> >>     aarch64, alpha (qemu) and hppa (qemu).
> >>
> >> Adhemerval Zanella (10):
> >>   Add string-maskoff.h generic header
> >>   Add string vectorized find and detection functions
> >>   string: Improve generic strlen
> >>   string: Improve generic strnlen
> >>   string: Improve generic strchr
> >>   string: Improve generic strchrnul
> >>   string: Improve generic strcmp
> >>   string: Improve generic memchr
> >>   string: Improve generic memrchr
> >>   sh: Add string-fzb.h
> >>
> >> Richard Henderson (7):
> >>   Parameterize op_t from memcopy.h
> >>   Parameterize OP_T_THRES from memcopy.h
> >>   hppa: Add memcopy.h
> >>   hppa: Add string-fzb.h and string-fzi.h
> >>   alpha: Add string-fzb.h and string-fzi.h
> >>   arm: Add string-fza.h
> >>   powerpc: Add string-fza.h
> >>
> >>  string/memchr.c                               | 168 ++++------------
> >>  string/memcmp.c                               |   4 -
> >>  string/memrchr.c                              | 189 +++--------------
> >> -
> >>  string/strchr.c                               | 172 +++-------------
> >>  string/strchrnul.c                            | 156 +++------------
> >>  string/strcmp.c                               | 119 +++++++++--
> >>  string/strlen.c                               |  90 ++-------
> >>  string/strnlen.c                              | 137 +------------
> >>  sysdeps/alpha/string-fzb.h                    |  51 +++++
> >>  sysdeps/alpha/string-fzi.h                    | 113 +++++++++++
> >>  sysdeps/arm/armv6t2/string-fza.h              |  70 +++++++
> >>  sysdeps/generic/memcopy.h                     |  10 +-
> >>  sysdeps/generic/string-extbyte.h              |  37 ++++
> >>  sysdeps/generic/string-fza.h                  | 106 ++++++++++
> >>  sysdeps/generic/string-fzb.h                  |  49 +++++
> >>  sysdeps/generic/string-fzi.h                  | 120 +++++++++++
> >>  sysdeps/generic/string-maskoff.h              |  73 +++++++
> >>  sysdeps/generic/string-opthr.h                |  25 +++
> >>  sysdeps/generic/string-optype.h               |  31 +++
> >>  sysdeps/hppa/memcopy.h                        |  42 ++++
> >>  sysdeps/hppa/string-fzb.h                     |  69 +++++++
> >>  sysdeps/hppa/string-fzi.h                     | 135 +++++++++++++
> >>  sysdeps/i386/i686/multiarch/strnlen-c.c       |  14 +-
> >>  sysdeps/i386/memcopy.h                        |   3 -
> >>  sysdeps/i386/string-opthr.h                   |  25 +++
> >>  sysdeps/m68k/memcopy.h                        |   3 -
> >>  sysdeps/powerpc/powerpc32/power4/memcopy.h    |   5 -
> >>  .../powerpc32/power4/multiarch/memchr-ppc32.c |  14 +-
> >>  .../power4/multiarch/strchrnul-ppc32.c        |   4 -
> >>  .../power4/multiarch/strnlen-ppc32.c          |  14 +-
> >>  .../powerpc64/multiarch/memchr-ppc64.c        |   9 +-
> >>  sysdeps/powerpc/string-fza.h                  |  70 +++++++
> >>  sysdeps/s390/strchr-c.c                       |  11 +-
> >>  sysdeps/s390/strchrnul-c.c                    |   2 -
> >>  sysdeps/s390/strlen-c.c                       |  10 +-
> >>  sysdeps/s390/strnlen-c.c                      |  14 +-
> >>  sysdeps/sh/string-fzb.h                       |  53 +++++
> >>  37 files changed, 1366 insertions(+), 851 deletions(-)
> >>  create mode 100644 sysdeps/alpha/string-fzb.h
> >>  create mode 100644 sysdeps/alpha/string-fzi.h
> >>  create mode 100644 sysdeps/arm/armv6t2/string-fza.h
> >>  create mode 100644 sysdeps/generic/string-extbyte.h
> >>  create mode 100644 sysdeps/generic/string-fza.h
> >>  create mode 100644 sysdeps/generic/string-fzb.h
> >>  create mode 100644 sysdeps/generic/string-fzi.h
> >>  create mode 100644 sysdeps/generic/string-maskoff.h
> >>  create mode 100644 sysdeps/generic/string-opthr.h
> >>  create mode 100644 sysdeps/generic/string-optype.h
> >>  create mode 100644 sysdeps/hppa/memcopy.h
> >>  create mode 100644 sysdeps/hppa/string-fzb.h
> >>  create mode 100644 sysdeps/hppa/string-fzi.h
> >>  create mode 100644 sysdeps/i386/string-opthr.h
> >>  create mode 100644 sysdeps/powerpc/string-fza.h
> >>  create mode 100644 sysdeps/sh/string-fzb.h
> >>
> >