IZ92726: PERFORMANCE DROP WITH -O2 -Q64

May 2012 PTF for XL C/C++ for AIX, V10.1
January 2013 PTF for XL C for AIX, V10.1
January 2013 PTF for XL C/C++ for AIX, V10.1
XL C/C++ for AIX Fix Pack 18 (July 2013 PTF) for 10.1
XL C/C++ for AIX Fix Pack 19 (October 2013 PTF) for 10.1
XL C/C++ for AIX Fix Pack 21 (October 2015 PTF) for 10.1
XL C for AIX Fix Pack 21 (October 2015 PTF) for 10.1
February 2011 PTF for XL C for AIX, V10.1
May 2011 PTF for XL C/C++ for AIX, V10.1
May 2011 PTF for XL C for AIX, V10.1
October 2011 PTF for XL C/C++ for AIX, V10.1
October 2011 PTF for XL C for AIX, V10.1
February 2012 PTF for XL C for AIX, V10.1
February 2012 PTF for XL C/C++ for AIX, V10.1
May 2012 PTF for XL C for AIX, V10.1
September 2012 PTF for XL C for AIX, V10.1
September 2012 PTF for XL C/C++ for AIX, V10.1
XL C for AIX Fix Pack 18 (July 2013 PTF) for 10.1
XL C for AIX Fix Pack 19 (October 2013 PTF) for 10.1
XL C for AIX Fix Pack 20 (October 2014 PTF) for 10.1
XL C/C++ for AIX Fix Pack 20 (October 2014 PTF) for 10.1

APAR status

• Closed as program error.

Error description

• A preformance drop is observed when compiling programs with -q64
  and -O2 (or higher) that contain loops with integer
  counters.
  

Local fix

• Compile with -q32 instead of -q64.
  

Problem summary

• PROBLEM DESCRIPTION:
  Poor performance for loops with 32-bit int control variables
  with -q64 at -O2 and up.
  
  USERS AFFECTED:
  Users with programs with for/do loops controlled by 32-bit
  integer variables concerned with performance.
  

Problem conclusion

• Fixed bug inhibiting loop optimization for loops with 32-bit
  integer control variables with -q64.
  

Temporary fix

Comments

APAR Information

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

  IZ87268

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

Fix information

• Fixed component name

  XL C AIX

• Fixed component ID

  5724U8000

Applicable component levels