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LI78451: ADDI+STXVD2X NOT SCHEDULED TOGETHER

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You can track all active APARs for this component.

APAR status

  • Closed as program error.

Error description

  • In some scenarios, code tuned for POWER8 does not schedule
    paired addi+stxvd2x instructions together.  This may cause
    less-than-ideal performance.
    
    
       === EXAMPLE ===
    
    
      1863| 00099C ori      60420000 1 ASM    'ori 2,2,0 #7 ,'
    * 1448| 0009A0 addi     3A400080 1 LI     gr18=128
      1866| 0009A4 add      7D6BEA14 1 A      gr11=gr11,gr29
      1867| 0009A8 add      7D4ADA14 1 A      gr10=gr10,gr27
    * 1448| 0009AC stxvd2x  7C019799 1 VSTQD  (gr1,gr18,0)=vs32
      1448| 0009B0 xvcpsgnd F0000781 1 LRVS   vs32=vs0
    
    The instructions marked with '*' should be scheduled together.
    

Local fix

Problem summary

  • PROBLEM DESCRIPTION:
    addi + stxvd2x instructions were not scheduled together to take
    advantage of POWER8 instruction fusion.
    
    USERS AFFECTED:
    Users who use -qarch=pwr8 with -O2 and above.
    

Problem conclusion

  • An issue with the instruction scheduler missed instruction
    fusion opportunities for vector store.  It has now been fixed.
    

Temporary fix

Comments

APAR Information

  • APAR number

    LI78451

  • Reported component name

    XL C/C++ FOR LI

  • Reported component ID

    5725C7300

  • Reported release

    D10

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2015-02-25

  • Closed date

    2015-02-25

  • Last modified date

    2015-02-25

  • APAR is sysrouted FROM one or more of the following:

    IV62232

  • APAR is sysrouted TO one or more of the following:

Fix information

  • Fixed component name

    XL C/C++ FOR LI

  • Fixed component ID

    5725C7300

Applicable component levels

  • RD10 PSY

       UP



Document information

More support for: XL C/C++ for Linux
Compiler

Software version: 13.1

Reference #: LI78451

Modified date: 25 February 2015