IV39402: INFINITE LOOP WITH -QIPA AND RELINK

XL C/C++ for AIX Fix Pack 4 (June 2013 PTF) for 12.1
XL C/C++ for AIX Fix Pack 5 (September 2013 PTF) for 12.1
XL C/C++ for AIX Fix Pack 7 (January 2014 PTF) for 12.1
XL C for AIX Fix Pack 8 (March 2014 PTF) for 12.1
XL C/C++ for AIX Fix Pack 8 (March 2014 PTF) for 12.1
XL C/C++ for AIX Fix Pack 11 (February 2015 PTF) for 12.1
XL C for AIX Fix Pack 12 (May 2015 PTF) for 12.1
XL C/C++ for AIX Fix Pack 12 (May 2015 PTF) for 12.1
XL C/C++ for AIX Fix Pack 13 (August 2015 Update) for 12.1
XL C/C++ for AIX Fix Pack 14 (December 2015 Update) for 12.1
XL C for AIX Fix Pack 15 (April 2016 Update) for 12.1
XL C/C++ for AIX Fix Pack 15 (April 2016 Update) for 12.1
XL C for AIX Fix Pack 16 (July 2016 Update) for 12.1
XL C/C++ for AIX Fix Pack 16 (July 2016 Update) for 12.1
XL C/C++ for AIX Fix Pack 17 (November 2016 Update) for 12.1
XL C for AIX Fix Pack 17 (November 2016 Update) for 12.1
XL C for AIX Fix Pack 18 (February 2017 Update) for 12.1
XL C/C++ for AIX Fix Pack 18 (February 2017 Update) for 12.1
XL C for AIX Fix Pack 19 (August 2017 Update) for 12.1
XL C/C++ for AIX Fix Pack 19 (August 2017 Update) for 12.1
XL C for AIX Fix Pack 20 (March 2018 Update) for 12.1
XL C/C++ for AIX Fix Pack 20 (March 2018 Update) for 12.1
XL C for AIX Fix Pack 4 (June 2013 PTF) for 12.1
XL C for AIX Fix Pack 5 (September 2013 PTF) for 12.1
XL C for AIX Fix Pack 6 (December 2013 PTF) for 12.1
XL C/C++ for AIX Fix Pack 6 (December 2013 PTF) for 12.1
XL C for AIX Fix Pack 7 (January 2014 PTF) for 12.1
XL C for AIX Fix Pack 9 (July 2014 PTF) for 12.1
XL C/C++ for AIX Fix Pack 9 (July 2014 PTF) for 12.1
XL C for AIX Fix Pack 10 (October 2014 PTF) for 12.1
XL C/C++ for AIX Fix Pack 10 (October 2014 PTF) for 12.1
XL C for AIX Fix Pack 11 (February 2015 PTF) for 12.1
XL C for AIX Fix Pack 13 (August 2015 Update) for 12.1
XL C for AIX Fix Pack 14 (December 2015 Update) for 12.1
XL C/C++ for AIX Fix Pack 21 (January 2019 Update) for 12.1
XL C for AIX Fix Pack 21 (January 2019 Update) for 12.1

APAR status

• Closed as program error.

Error description

• When compiling and linking with -qipa and relink, the comparison
  in the while loop (in the test case below) is not being
  satisfied which leads to an infinite loop.
  
  
  ===== COMPILE COMMAND:
  
  xlc_r -qutf -qcpluscmt  -O -qfdpr -qstrict -qlibansi
  -qinlglue -qmaxmem=8192 -qarch=ppc -qtune=balanced -qspill=2560
  -qsaveopt -qipa=level=0:inline=noauto -qlanglvl=stdc89
  -qlonglong -bcdtors:mbr::s -bweaklocal -q64 -brtl  -bbigtoc
  -qipa=relink -qdebug=timing -qpdf1=pdfname=test.pdf1
  -qipa=level=0 -lperfstat -lrt -lwlm -lpthread -lm test.c
  
  ===== TESTCASE:
  $ cat test.c
  #include <stdio.h>
  
  int main (int argc, const char* argv[] )
  {
          unsigned char a = 254;
          while( a != (unsigned char)255){
                  printf("counter: %d\n", (unsigned int)a);
                  a--;
          }
  }
  $
  
  
  ===== ACTUAL OUTPUT:
  Infinite loop
  
  
  ===== EXPECTED OUTPUT:
  No infinite loop
  

Local fix

• N/A
  

Problem summary

• USERS AFFECTED:
  Any user that has loop counters less than size int that
  overflow and the user invokes TPO via  -O3, -O4, -O5 or -qipa
  can be affected by this issue.
  
  PROBLEM DESCRIPTION:
  Loop normalization does not expect loop counters to overflow,
  and thus generates bad code.
  

Problem conclusion

• The above issue has been corrected within the IPA component of
  the compiler.
  

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:

  IV40225 LI77596

Fix information

• Fixed component name

  XL C FOR AIX

• Fixed component ID

  5725C7100

Applicable component levels

• RC10 PSY UP

     C