IV68828: INEFFICIENT CODE FOR __VEC_STRMB

XL C/C++ for AIX Fix Pack 3 (April 2015 PTF) for 13.1
XL C/C++ for AIX Fix Pack 4 (July 2015 PTF) for 13.1
XL C for AIX Fix Pack 5 (November 2015 Update) for 13.1
XL C/C++ for AIX Fix Pack 5 (November 2015 PTF) for 13.1
XL C/C++ for AIX Fix Pack 6 (February 2016 PTF) for 13.1
XL C for AIX Fix Pack 6 (February 2016 Update) for 13.1
XL C for AIX Fix Pack 7 (May 2016 Update) for 13.1
XL C/C++ for AIX Fix Pack 7 (May 2016 PTF) for 13.1
XL C for AIX Fix Pack 8 (August 2016 Update) for 13.1
XL C/C++ for AIX Fix Pack 8 (August 2016 PTF) for 13.1
XL C for AIX Fix Pack 9 (June 2017 Update) for 13.1
XL C/C++ for AIX Fix Pack 9 (June 2017 PTF) for 13.1
XL C for AIX Fix Pack 10 (February 2018 Update) for 13.1
XL C/C++ for AIX Fix Pack 10 (February 2018 PTF) for 13.1
XL C for AIX Fix Pack 3 (April 2015 PTF) for 13.1
XL C for AIX Fix Pack 4 (July 2015 PTF) for 13.1
XL C/C++ for AIX Fix Pack 11 (November 2018 PTF) for 13.1
XL C for AIX Fix Pack 11 (November 2018) for 13.1

APAR status

• Closed as program error.

Error description

• When compiling code that looks similar to the following:
  void store16(vector unsigned char v, char* p)
  {
     return __vec_strmb(p, 16, v);
  }
  
  the compiler generates a listing that looks similar to the
  following:
  __vec_strmb(p, 16, v):
       | 000000                           PDEF     store16(vector
  unsigned char, char *)
       | 000000                           AKA       store16__FacPc
     58|                                  PROC      v,p,vs34,gr3
     60| 000154 addi     38000010   1     LI        gr0=16
     60| 000158 lvx      7C2300CE   1     VLQ
  vs33=(char)(gr3,gr0,0)
     60| 00015C lvx      7C6018CE   1     VLQ
  vs35=(char)(gr3,0)
     60| 000160 lvsr     7C80184C   1     LVSR
  vs36=(char)(gr3,0)
     60| 000164 xxlxor   F00004D7   1     VXOR      vs32=vs32,vs32
     60| 000168 vspltisb 10BF030C   1     VSPLTISB  vs37=-1
     60| 00016C vperm    10C0292B   1     VPERM
  vs38=vs32,vs37,vs36
     60| 000170 vperm    1042112B   1     VPERM
  vs34=vs34,vs34,vs36
     60| 000174 vperm    1005012B   1     VPERM
  vs32=vs37,vs32,vs36
     60| 000178 xxsel    F001103F   1     VSEL
  vs32=vs33,vs34,vs32
     60| 00017C xxsel    F02311BF   1     VSEL
  vs33=vs35,vs34,vs38
     60| 000180 stvx     7C2019CE   1     VSTQ
  (char)(gr3,0)=vs33
     60| 000184 stvx     7C0301CE   1     VSTQ
  (char)(gr3,gr0,0)=vs32
     61| 000188 bclr     4E800020   0     BA        lr
  
  
  The expected output in the listings is to have single stvd2x.
  

Local fix

• N/A
  

Problem summary

• USERS AFFECTED:
  Users who use the __vec_strmb() builtin may be affected by this
  issue.
  
  PROBLEM DESCRIPTION:
  When observing the listing file generated for the __vec_strmb()
  section, the compiler generates unnecessary stvd2x instructions.
  

Problem conclusion

• The compiler has been changed to not produce the unnecessary
  stvd2x instructions anymore.
  

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 FOR AIX

• Fixed component ID

  5725C7100

Applicable component levels