IV77965: MISSING INLINE ASM STATEMENT WITH OPTIMIZATION

XL C/C++ for AIX Fix Pack 14 (December 2015 Update) for 12.1
XL C/C++ for AIX Fix Pack 15 (April 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/C++ for AIX Fix Pack 18 (February 2017 Update) for 12.1
XL C/C++ for AIX Fix Pack 19 (August 2017 Update) for 12.1
XL C/C++ for AIX Fix Pack 20 (March 2018 Update) for 12.1
XL C/C++ for AIX Fix Pack 21 (January 2019 Update) for 12.1

APAR status

• Closed as program error.

Error description

• When using optimization with inlining, an inline ASM statement
  is not being inserted into the generated code.  The cause seems
  related to code function inlining efforts and optimization by
  the compiler.
  
  
     === EXAMPLE ===
  
  (Note:  example is not compilable)
  
  ----------------------------
  
  __asm__ ("sld %0,%1,%2" : "=r"(a) : "r"(a), "r"(z) : );
  
  Uint64 c, d;
  
  __asm__("srd %0,%1,%2" : "=r"(c) : "r"(b),"r"(z) : );
  __asm__("sld %0,%1,%2" : "=r"(d) : "r"(b),"r"(z) : );
  
  a |= (c | d);
  
  __asm__("sld %0,%1,%2" : "=r"(b) : "r"(b), "r"(z) : );
  
  ----------------------------
  
  In this case, the last inline ASM statement is not being
  generated in the compiled code:
  
  ----------------------------
  
   661| 0034C4 sld      7D663036   1
            ASM gr6='sld %0,%1,%2'r r r:,1,gr11,gr6
  
   911| 0034C8 ori      612A0000   1 LR  gr10=gr9
  1235| 0034CC rlwinm   54BFFF3E   1 RN4 gr31=gr5,31,0xF
   667| 0034D0 srd      7D284436   1
            ASM gr8='srd %0,%1,%2,'r r r:,2,gr9,gr8
  
   668| 0034D4 sld      7D296036   1
            ASM gr9='sld   %0,%1,%2,'r r r:,3,gr9,gr12
  
  # LOGICAL "OR" OPERATIONS FOR 'a'
   669| 0034D8 or       7D084B78   1 O   gr8=gr8,gr9
   911| 0034DC ori      6149000C   1 OIL gr9=gr10,0xC
   669| 0034E0 or       7CC64378   1 O   gr6=gr6,gr8
  
  # BUT NO 4TH ASM STATEMENT
   912| 0034E4 or       7C004B78   1 O   gr0=gr0,gr9
   669| 0034E8 std      F8C1FFA0   1 ST8 <a5:d112:l8>(gr1,-96)=gr6
   465| 0034EC cntlzd   7CC80074   1 CNTLZ8  gr8=gr6
   465| 0034F0 cntlzd   7C0A0074   1 CNTLZ8  gr10=gr0
  
  ----------------------------
  

Local fix

• Do not use optimization.
  

Problem summary

• USERS AFFECTED:
  Users who have ASM statemetns and compile with inlining or any
  optimization related to inlining could be affected by this
  issue.
  
  PROBLEM DESCRIPTION:
  The compiler was failing to generate an extra ASM statement in
  the object code listing resulting in undefined behavior.
  

Problem conclusion

• The compiler 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:

  IV77968

Fix information

• Fixed component name

  XL C/C++ FOR AI

• Fixed component ID

  5725C7200

Applicable component levels

• RC10 PSY

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