[Bug 1932010] Comment bridged from LTC Bugzilla

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------- Comment From iii at de.ibm.com 2021-08-11 10:36 EDT-------
I think it rather has to do with glibc - ifunc are normally called quite early and therefore cannot use the dynamically resolved symbols, but maybe newer glibcs tolerate that. Unfortunately I couldn't find more information on this subject. The code seems to work, but just to be on the safe side I'd rather switch to the "old way" of doing things, that involves the hwcap argument:

https://bugzilla.linux.ibm.com/attachment.cgi?id=150618&action=diff#a/crc32.c_sec1
https://bugzilla.linux.ibm.com/attachment.cgi?id=150618&action=diff#a/crc32.c_sec3

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https://bugs.launchpad.net/bugs/1932010

Title:
  [21.10 FEAT] zlib CRC32 optimization for s390x

Status in Ubuntu on IBM z Systems:
  In Progress
Status in zlib package in Ubuntu:
  In Progress

Bug description:
  Use SIMD instructions to accelerate the zlib CRC32 implementation.
  Business value: Performance improvement in database area

  The zlib CRC32 optimization for IBM Z is currently being discussed for inclusion into zlib-ng:
  https://github.com/zlib-ng/zlib-ng/pull/912

  The patch for zlib will be based on that.

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