Fixes are available
APAR status
Closed as program error.
Error description
A performance degradation is seen with the __popcnt4 and __popcnt8 population count functions when POWER7 hardware is targeted with the -qarch/-qtune options, and -qhot/IPA optimization is used. Slower code is generated using the popcntb instruction instead of the popcntw/popcntd instructions.
Local fix
- Do not use higher -qhot levels, use -qhot=level=0
Problem summary
PROBLEM DESCRIPTION: Performance degradation with popcnt optimization. USERS AFFECTED: Customers who use popcnt instructions on POWER7.
Problem conclusion
The popcnt optimization on POWER7 has been disabled, since it is not profitable on POWER7.
Temporary fix
Comments
APAR Information
APAR number
LI77452
Reported component name
XL C/C++ FOR LI
Reported component ID
5724X1400
Reported release
B10
Status
CLOSED PER
PE
NoPE
HIPER
NoHIPER
Special Attention
NoSpecatt / Xsystem
Submitted date
2013-06-11
Closed date
2013-06-11
Last modified date
2013-06-11
APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:
Fix information
Fixed component name
XL C/C++ FOR LI
Fixed component ID
5724X1400
Applicable component levels
RB10 PSN IV29519
UP06/09/13
[{"Business Unit":{"code":"BU058","label":"IBM Infrastructure w\/TPS"},"Product":{"code":"SSXVZZ","label":"XL C\/C++ for Linux"},"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"B10","Line of Business":{"code":"LOB57","label":"Power"}}]
Document Information
Modified date:
14 October 2021