IV61656: INLINED MEMSET IMPROVEMENT FOR CONSTANT SIZE

XL C/C++ for AIX Fix Pack 1 (September 2014 PTF) for 13.1
XL C/C++ for AIX Fix Pack 2 (December 2014 PTF) for 13.1
XL C/C++ for AIX Fix Pack 3 (April 2015 PTF) for 13.1
XL C/C++ for AIX Fix Pack 4 (July 2015 PTF) for 13.1
XL C for AIX Fix Pack 5 (November 2015 Update) for 13.1
XL C/C++ for AIX Fix Pack 5 (November 2015 PTF) for 13.1
XL C/C++ for AIX Fix Pack 6 (February 2016 PTF) for 13.1
XL C for AIX Fix Pack 6 (February 2016 Update) for 13.1
XL C for AIX Fix Pack 7 (May 2016 Update) for 13.1
XL C/C++ for AIX Fix Pack 7 (May 2016 PTF) for 13.1
XL C for AIX Fix Pack 8 (August 2016 Update) for 13.1
XL C/C++ for AIX Fix Pack 8 (August 2016 PTF) for 13.1
XL C for AIX Fix Pack 9 (June 2017 Update) for 13.1
XL C/C++ for AIX Fix Pack 9 (June 2017 PTF) for 13.1
XL C for AIX Fix Pack 10 (February 2018 Update) for 13.1
XL C/C++ for AIX Fix Pack 10 (February 2018 PTF) for 13.1
XL C for AIX Fix Pack 1 (September 2014 PTF) for 13.1
XL C for AIX Fix Pack 2 (December 2014 PTF) for 13.1
XL C for AIX Fix Pack 3 (April 2015 PTF) for 13.1
XL C for AIX Fix Pack 4 (July 2015 PTF) for 13.1
XL C/C++ for AIX Fix Pack 11 (November 2018 PTF) for 13.1
XL C for AIX Fix Pack 11 (November 2018) for 13.1

APAR status

• Closed as program error.

Error description

• For memset() cases where the size/number of characters to write
  is constant, the inlined memset() code that is generated can be
  improved.
  
  
     === TEST CASE ===
  
  void set11(char *start, char c)
  {
    memset(start, c, 19);   // Size value (19) is constant
  }
  

Local fix

Problem summary

• PROBLEM DESCRIPTION:
  The memset() function uses 2 registers when the compile time
  length is known and it involves more than 1 different sized
  store.  This is a small performance issue.
  
  USERS AFFECTED:
  memset() users
  

Problem conclusion

• Use the longest value needed to generate for all the stores.
  

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:

  LI78224

Fix information

• Fixed component name

  XL C FOR AIX

• Fixed component ID

  5725C7100

Applicable component levels

• RD10 PSY

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