IZ90712: SUPERFLUOUS EXTSW WITH POPCNT INTRINSIC

March 2011 PTF for XL Fortran for AIX, V13.1
August 2011 PTF for XL Fortran for AIX, V13.1
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 using the POPCNT compiler intrinsic, the Fortran
  compiler is generating an unnecessary sign extension EXTSW
  instruction when using 64-bit mode.
  
  
  =============== Example ================
  
  logical(4):: a4B
  integer(4):: r4B
  logical(8):: a8B
  integer(4):: r8B
  
  ...
  
  r4B = popcnt (a4B)
  r8B = popcnt (a8B)
  
     ----- Generated Code -----
  
   popcntw  7C0002F4   1     POPCNT4   gr0=gr0
   extsw    7C0007B4   1     EXTS4     gr0=gr0
   stw      90010074   1     ST4A      r4b(gr1,116)=gr0
  
   popcntd  7C0003F4   1     POPCNT8   gr0=gr0
   extsw    7C0007B4   1     EXTS4     gr0=gr0
   stw      90010080   1     ST4A      r8b(gr1,128)=gr0
  

Local fix

• N/A
  

Problem summary

• PROBLEM DESCRIPTION:
  In 64 bit mode, each POPCNT instruction was followed by an
  unneeded EXTS4 extend sign instruction.
  
  USERS AFFECTED:
  Users calling one of the __popcnt... built in functions.
  

Problem conclusion

• EXTS4 is unneeded because POPCNT can only produce values from 0
  to 64, the sign bit can never be set, and extending it will
  leave the value unchanged.  EXTS4 after POPCNT is now
  discarded.
  

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:

  LI75814

Fix information

• Fixed component name

  XL FORTRAN FOR

• Fixed component ID

  5724X1500

Applicable component levels

• RD10 PSY U842152

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