IJ46674: INTERNAL COMPILER ERROR USING -O3 CAUSED BY ASSIGNMENT IN CONDITIONAL

APAR status

• Closed as program error.

Error description

• When compiling the testcase with -O3 an internal compiler error
  is caused by the assignment in the conditional i.e.
  
   19      if (x = t->cln)
  
  Below is the -O3 internal compiler error:
  
  $ xlc++_r -q64 -O3  -c -o mymodule.o mymodule.c
      1500-004: (U) INTERNAL COMPILER ERROR while compiling
  windex.  Compilation ended.  Contact your Service Representative
  and provide the following information: GRARNN: cr591 is used
  before it is defined. For more information visit:
  http://www.ibm.com/support/docview.wss?uid=swg21110810
  1586-346 (U) An error occurred during code generation.  The code
  generation return code was 1.
  $
  
  ===== TESTCASE:
  $ cat -n mymodule.c
       1  typedef unsigned short USHORT;
       2  typedef unsigned char UCHAR;
       3
       4
       5  typedef struct
       6  {
       7      UCHAR mln;
       8      UCHAR cln;
       9      USHORT wdata[1];
      10  } WIDE;
      11
      12  int windex(WIDE* t, WIDE* s)
      13  {
      14      int i;
      15      int j;
      16      int x;
      17      int y;
      18
      19      if (x = t->cln)
      20      {
      21          y = s->cln - x;
      22          for (i = 0; i <= y; i++)
      23          {
      24              for (j = 0; j < x && t->wdata[j] ==
  s->wdata[i + j]; j++)
      25              {
      26              }
      27              if (j == x)
      28              {
      29                  return (i + 1);
      30              }
      31          }
      32      }
      33      return (0);
      34  }
      35
  $
  

Local fix

• ===== WORKAROUND:
  Using -O2 optimization with the testcase passes compilation.
  

Problem summary

• USERS AFFECTED: XLC Users using the OPTIMIZE option.
  
  PROBLEM DESCRIPTION: The unswitch pass(invariant branch motion)
  may incorrectly move a branch together with its inputs to the
  outside of the loop.
  

Problem conclusion

• The compiler backend component has been fixed by aborting the
  compare process when register has more than 1 definition.
  

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