IJ39592: INCORRECT CARRY BIT OPTIMIZATION CAUSING INCORRECT RESULT

APAR status

• Closed as program error.

Error description

• An arithmetic/bitwise shift value calculation is incorrectly
  optimized at optimization level -O2 due to an incorrect usage
  of the carry bit (CA) by the code optimizer.  The carry bit is
  not considered by the code optimization.
  
  An example calculation that may invoke this code optimization
  may look like:
  
   val = ((input + 1)>>1) - (out ? 2 : 1);
  

Local fix

• Use a lower optimization level.
  

Problem summary

• PROBLEM DESCRIPTION:
  An incorrect result is calculated in some cases when
  optimization is used and the calculation involves a bitwise
  shift.
  
  USERS AFFECTED:
  Those using bitwise calculations and optimization.
  

Problem conclusion

• The optimization has now been corrected.
  

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:

Fix information

• Fixed component name

  XL C/C++ FOR AI

• Fixed component ID

  5725C7200

Applicable component levels