IV69565: MISSED COMPLEX TYPE SIMD OPPORTUNITY CAUSING PERFORMANCE ISSUE

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/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

• A loop compiled with -qsimd=auto containing complex data types
  is not vectorized.
  
  
  
     === EXAMPLE ===
  
  double _Complex shl[val];
  
  while(cnt++<100000000)
  {
    for(int s = 0; s < 8; s++)
    {
      shl[0 + 3*(s)] += tmp[s] * Factor;
      shl[1 + 3*(s)] += tmp[s] * Factor;
    }
  }
  
  $ xlC_r test.C -q64 -O3 -qhot -qsimd=auto
  
  1586-551 (I) Loop (loop index 6) at test.C <line 20> was not
  SIMD vectorized because it contains unsupported vector data
  types.
  
  (Note:  example is not a compilable source)
  

Local fix

Problem summary

• PROBLEM DESCRIPTION:
  Some auto-SIMD optimization opportunities are missed for double
  complex multiply and converts.
  
  USERS AFFECTED:
  Double complex users using auto-SIMD.
  

Problem conclusion

• Double complex multiply and convert operations (taking 2 double
  values and creating a double complex from them) are now
  automatically vectorized.
  

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

• RD10 PSY

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