[Bug 1793786] Re: libc6 2.27 lacks sse2 optimized strstr()

[Paul Stephen Borile]

Running /lib/x86_64-linux-gnu/libc.so.6 on my machine gives :

GNU C Library (Ubuntu GLIBC 2.27-3ubuntu1) stable release version 2.27.
Copyright (C) 2018 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE.
Compiled by GNU CC version 7.3.0.
libc ABIs: UNIQUE IFUNC
For bug reporting instructions, please see:
<https://bugs.launchpad.net/ubuntu/+source/glibc/+bugs>.

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https://bugs.launchpad.net/bugs/1793786

Title:
  libc6 2.27 lacks sse2 optimized strstr()

Status in glibc package in Ubuntu:
  New

Bug description:
  Looks like code using strstr() and libc-2.27 is running 4 times slower
  than was with libc-2.23. Having a look at profiled code executed in
  various moments show different versions of strstr :

  - libc-2.27.so: strstr.c, str-two-way.h - this is current version
  ubuntu 18.04.1

  Same code, profiled March 13, 2018 :

  - libc-2.23.so: strstr-sse2-unaligned.S

  Is the removal of sse2 optimized code from strstr() an error of some kind ?
  Best
  -Paul

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