Re: [PATCH 0/4] Improve generic strspn/strcspn/strpbrk

[Adhemerval Zanella <adhemerval dot zanella at linaro dot org>]

Besides latest Wilco's reviews regarding the __glibc_expect for
strcspn and Richard's note about using uintptr_t instead of
size_t for pointer manipulation, is there any more review
about this set? If not I will commit it this in upcoming hours.

On 31-03-2016 11:00, Adhemerval Zanella wrote:
> Changes from previous version:
> 
>  * Add some optimization on strspn implementation from Wilco
>    comments.
> 
>  * Move the inline __str{spn,cspn,brk}_* symbol from the string2.h
>    header to string-inlike and added compatibility version since
>    they will not be generated anymore.
> 
> ---
> 
> 
> This is a followup on previous Wilco patch [1] to optimize strcspn
> that also optimizes the generic strspn and strpbrk.  I used the
> same strategy Wilco has used on strcspn for strspn and rewrote
> strpbrk to just use strcspn instead.
> 
> I also tried to play with compiler options to check if it could
> omit the memset call generation when initializing the lookup
> table, but without success.  This is a similar strategy I used
> on powerpc64 str{c}spn optimization.
> 
> Wilco initial approach was to remove the __strcspn_c{1,2,3}
> inline function in string2.h header, however they are part of
> ABI (to support compilers that do not inline the calls) and it
> is not safe to remove then.  I have added it back, although the
> strcspn new macro does not uses them and I also used the same
> strategy for both strspn and strpbrk.
> 
> Performance-wise the algorithm is similar with current optimized
> assembly one already in GLIBC (x86 and powerpc).  In fact, for
> powerpc64 the algorithm performance is similar to assembly
> routines which lead me to remove them.  i686 default one
> is slight faster, while the SSE4.1 variant shows much better
> performance (through the use of SIMD instructions).
> 
> [1] https://sourceware.org/ml/libc-alpha/2016-01/msg00173.html
> 
> Adhemerval Zanella (3):
>   Improve generic strspn performance
>   Improve generic strpbrk performance
>   Remove powerpc64 strspn, strcspn, and strpbrk implementation
> 
> Wilco Dijkstra (1):
>   Improve generic strcspn performance
> 
>  ChangeLog                           |  46 ++++++++
>  string/Versions                     |   2 +
>  string/bits/string2.h               | 208 ++----------------------------------
>  string/strcspn.c                    |  44 ++++++--
>  string/string-inlines.c             |  97 +++++++++++++++++
>  string/strpbrk.c                    |  12 +--
>  string/strspn.c                     |  54 +++++++---
>  sysdeps/i386/string-inlines.c       |  19 +---
>  sysdeps/powerpc/powerpc64/strcspn.S | 127 ----------------------
>  sysdeps/powerpc/powerpc64/strpbrk.S | 135 -----------------------
>  sysdeps/powerpc/powerpc64/strspn.S  | 144 -------------------------
>  11 files changed, 233 insertions(+), 655 deletions(-)
>  delete mode 100644 sysdeps/powerpc/powerpc64/strcspn.S
>  delete mode 100644 sysdeps/powerpc/powerpc64/strpbrk.S
>  delete mode 100644 sysdeps/powerpc/powerpc64/strspn.S
>