IZ99375: Performance Degradation due to load/store motion

August 2011 PTF for XL Fortran for AIX, V13.1
January 2012 PTF for XL Fortran for AIX, V13.1
April 2012 PTF for XL Fortran for AIX, V13.1
July 2012 PTF for XL Fortran for AIX, V13.1
October 2012 PTF for XL Fortran for AIX, V13.1
February 2013 PTF for XL Fortran for AIX, V13.1
May 2013 PTF for XL Fortran for AIX, V13.1
XL Fortran for AIX Fix Pack 15 (August 2013 PTF) for 13.1
XL Fortran for AIX Fix Pack 16 (November 2013 PTF) for 13.1
XL Fortran for AIX Fix Pack 17 (February 2014 PTF) for 13.1
XL Fortran for AIX Fix Pack 21 (April 2015 PTF) for 13.1
XL Fortran for AIX Fix Pack 22 (September 2015 PTF) for 13.1
XL Fortran for AIX Fix Pack 23 (March 2016 PTF) for 13.1
XL Fortran for AIX Fix Pack 24 (September 2016 PTF) for 13.1

APAR status

• Closed as program error.

Error description

• This is a performance degradation caused by a limitation in
  load/store motion in optimizer. Optimizer is no longer marking
  the multiplication by a literal value as invariant, which leaves
  additional computation inside of a hot loop.
  

Local fix

• -qstrict=association might fix the problem, although it
  shouldn't to be considered as a general solution to the problem.
  

Problem summary

• This is a performance degradation caused by a limitation in
  load/store motion in optimizer. Optimizer is no longer marking
  the multiplication by a literal value as invariant, which
  leaves additional computation inside of a hot loop.
  

Problem conclusion

• Extended the existing load/store motion optimization to handle
  literal values. The net effect of this is that we can now
  consistently detect constant values as invariant code and move
  them outside of loops (if it is profitable to do so).
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

  LI76303

Fix information

• Fixed component name

  XL FORTRAN FOR

• Fixed component ID

  5724X1500

Applicable component levels

• RD10 PSY U844586

     UP C