IV07685: QSIMD=AUTO CAUSING ERROR FOR QARCH=PWR7

January 2012 PTF for XL Fortran for AIX, V13.1
April 2012 PTF for XL Fortran for AIX, V13.1
July 2012 PTF for XL Fortran for AIX, V13.1
October 2012 PTF for XL Fortran for AIX, V13.1
February 2013 PTF for XL Fortran for AIX, V13.1
May 2013 PTF for XL Fortran for AIX, V13.1
XL Fortran for AIX Fix Pack 15 (August 2013 PTF) for 13.1
XL Fortran for AIX Fix Pack 16 (November 2013 PTF) for 13.1
XL Fortran for AIX Fix Pack 17 (February 2014 PTF) for 13.1
XL Fortran for AIX Fix Pack 21 (April 2015 PTF) for 13.1
XL Fortran for AIX Fix Pack 22 (September 2015 PTF) for 13.1
XL Fortran for AIX Fix Pack 23 (March 2016 PTF) for 13.1
XL Fortran for AIX Fix Pack 24 (September 2016 PTF) for 13.1

APAR status

• Closed as program error.

Error description

• When compiling the following test case with -qsimd=auto and
  targeting the POWER7 architecture with -qarch=pwr7, the compiler
  is encountering an internal error when -qnostrict is enabled
  
  The -qnostrict option is enabled automatically when compiling
  with -O3, or can be set manually at -O2.  The -qnostrict
  suboptions causing the issue are
  -qstrict=noprecision:noexceptions
  
  
  
     ======  TEST CASE  ======
  
  SUBROUTINE test (arr, A, B, num)
  IMPLICIT NONE
  
  Integer, intent(in) :: num
  Real, intent(in)    :: A(num), B(num)
  Real, intent(out)   :: arr(num)
  
  Real :: result1, result2
  
  Integer :: I, II
  
  Do i = 1, num-1,2
  
    result1 = 1.0+1.0*B(I) * (1.0+1.0*(A(I)-0) * (A(I)-0))
    result2 = 1.0+1.0*B(I+1) * (1.0+1.0*(A(I+1)-0) * (A(I+1)-0))
  
    arr(I)   = arr(I)   * result1
    arr(I+1) = arr(I+1) * result2
  
    arr(I)   = (1*arr(I)) / (MAX(B(I),1.0*arr(I))-arr(I))
    arr(I+1) = (1*arr(I+1)) / (MAX(B(I+1),1.0*arr(I+1))-arr(I+1))
  
  End Do
  
  RETURN
  END SUBROUTINE test
  
  
     ======  COMPILE  ======
  $ xlf90_r -q64 -qrealsize=8 -c -qsimd=auto -O2 -qhot -qarch=pwr7
  -qstrict=noprecision:noexceptions test.f90
  ** test   === End of Compilation 1 ===
  "test.f90", 1500-004 (U) INTERNAL COMPILER ERROR while compiling
  test.  Compilation ended.  Contact your Service Representative
  and provide the following information: Internal abort. 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.
  1501-511  Compilation failed for file test.f90.
  $
  

Local fix

• Any one of the following options may work around the issue:
  
  - Compile with -qsimd=noauto
  - Compile with -qnohot
  - Compile for POWER6 instead with -qarch=pwr6
  - Compile explicitly with -qstrict
  - Move the order of your code around.  This issue appears to be
  sensitive to code position.
  

Problem summary

• USERS AFFECTED:
  Users who compile with -qsimd=auto at -O2 may encounter this
  issue.
  
  PROBLEM DESCRIPTION:
  -qsimd=auto makes use of vector RCP instructions which the
  compiler was taught how to handle.
  As a result, the compiler produced an internal compiler error.
  

Problem conclusion

• The compiler has been fixed to support vector RCP instructions
  and no longer produces an internal compiler error.
  

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:

  LI76619

Fix information

• Fixed component name

  XL FORTRAN FOR

• Fixed component ID

  5724X1500

Applicable component levels

• RD10 PSY U848520

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