LI77059: INCORRECT OUTPUT WITH -O2

XL C/C++ for Linux Fix Pack 9 (August 2013 Update) for 11.1
October 2012 Update for XL C/C++ for Linux, V11.1
XL C/C++ for Linux Fix Pack 8 (June 2013 Update) for 11.1

APAR status

• Closed as program error.

Error description

• Consider the following testcase:
  
  
  /////////////////////// test.c //////////////////////////////
  #include <stdio.h>
  
  static unsigned long long f(unsigned b, unsigned long long ys)
  {
   unsigned long long y = b - (ys & 0xFFFFFFFFULL);
   return (y >> 32) & 1;
  }
  
  int main()
  {
   printf("%llu\n", f(0x75600000U, 0x1E0800000ULL));
   return 0;
  }
  //////////////////////////////////////////////////////////////
  
  
  Compile the source file with -O (-O2):
  
  xlc -O -q64 -o di3 di3.c&&  ./di3
  
  The compiler incorrectly outputs 0. The correct output should
  be: 1. The issue is not reproduced with higher optimization (-O3
  and up) or with no optimization turned on.
  

Local fix

• Do not turn optimization on, or use -O3 and higher.
  

Problem summary

• The compiler fixload problem.
  

Problem conclusion

• The problem is fixed
  

Temporary fix

Comments

APAR Information

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

  IV20818

• 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 IV20818

     UP06/09/13