IV22269: BRANCH HINTS WITH EXECUTION_FREQUENCY IGNORED

July 2012 PTF for XL C/C++ for AIX, V11.1
July 2012 PTF for XL C for AIX, V11.1
October 2012 PTF for XL C/C++ for AIX, V11.1
October 2012 PTF for XL C for AIX, V11.1
February 2013 PTF for XL C for AIX, V11.1
February 2013 PTF for XL C/C++ for AIX, V11.1

APAR status

• Closed as program error.

Error description

• When a client specifically uses the
  _Pragma("execution_frequency(very_low)"), the compiler should
  respect it and set the hint bits accordingly.
  
  But, below is a section of a listing where the compiler was
  ignoring the user pragma:
  
  Listing file:
  
  
       | 000000                           PDEF
  sqlv_dec31_add_dec31(unsigned char *, const unsigned char *
  const, size_t)
       | 000000                           AKA
  sqlv_dec31_add_dec31__FPUcCPCUcUl
     36|                                  PROC
  sum,addend,addendLength,gr3-gr5
      0| 000000 std      FBE1FFF8   1     ST8
  #stack(gr1,-8)=gr31
   1444| 000004 cmpldi   28250010   1     CL8       cr0=gr5,16
   1444| 000008 ld       E8C20008   1     L8
  gr6=.$STATIC(gr2,0)
   1444| 00000C rlwinm   54A51E38   1     RN4       gr5=gr5,3,0xF8
   1444| 000010 ldx      7C06282A   1     L8
  gr0=$STATIC(gr6,gr5,0)
   1444| 000014 bc       41810018   1     BT
  CL.141,cr0,0x10/lgt,taken=50%(0,0) <---- Ignored here
   1444| 000018 mtspr    7C0903A6   1     LCTR      ctr=gr0
   1444| 00001C bcctr    4E800420   1     BA        ctr,*11182,147
  
  The indicated branch above is marked 50/50, but should be
  marked as taken rarely.
  

Local fix

• n/a
  

Problem summary

• USERS AFFECTED:
  Anyone using the pragma to indicate cold branches that are
  simple enough to transform into a SEL instruction are affected
  by this issue.
  TPO must be involved (-O3 or above).
  
  PROBLEM DESCRIPTION:
  pragma execution_frequency(very_low) is getting misplaced by
  TPO causing sub-optimal code-gen
  

Problem conclusion

• The issue has been fixed.
  

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:

  IV25666 LI76947

Fix information

• Fixed component name

  XL C FOR AIX

• Fixed component ID

  5724X1200

Applicable component levels

• RB10 PSY U852940

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