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LI77797: MISSING LOAD WITH -O3

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APAR status

  • Closed as program error.

Error description

  • There are certain scenarios where the compiler might remove a
    necessary load 'after' a sync() instruction before its
    used.
    
    
    An example is the following:
    
    .L1629:
     lwz         r3,96(r31)
     lwz         r6,104(r31)    <---- load of r6
     subf        r4,r6,r3
     addi        r0,r3,-1
     rlwinm.     r3,r4,0,15,31
     beq         .L2014
    
     rlwinm      r4,r0,0,15,31
     stw         r4,96(r31)
     sync                      <---- sync instruction
     ld          r3,144(r31)
     rlwinm      r5,r0,3,12,28
     subf        r0,r6,r0      <---- r6 is being used in subf
    without it being loaded again after the sync instruction
     rlwinm      r0,r0,0,15,31
     cmplw       cr0,r0,r27
     ldx         r3,r3,r5
     std         r3,112(r1)
     beq         .L1655
    
     cmpdi       cr0,r0,0
     bne         .L173
    

Local fix

  • N/A
    

Problem summary

  • USERS AFFECTED:
    Users coding in assembly and those who use the sync instruction
    may be affected by this issue.
    
    PROBLEM DESCRIPTION:
    The compiler forgets to generate a load after the sync
    instruction.
    

Problem conclusion

  • The compiler has been fixed to invalidate all aliasing symbols
    before sync the instruction so that they will be reloaded after
    sync instruction.
    

Temporary fix

Comments

APAR Information

  • APAR number

    LI77797

  • Reported component name

    XL C/C++ SLES10

  • Reported component ID

    5724U8300

  • Reported release

    A10

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2014-01-15

  • Closed date

    2014-01-15

  • Last modified date

    2014-01-15

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

    IV51008

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

Fix information

  • Fixed component name

    XL C/C++ SLES10

  • Fixed component ID

    5724U8300

Applicable component levels



Document information

More support for: XL C/C++

Software version: A.1

Reference #: LI77797

Modified date: 15 January 2014