IV37628: USE LFIWAX/LFIWZX FOR INT TO FLOAT CONVERSION

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You can track all active APARs for this component.

APAR status

  • Closed as program error.

Error description

  • Compiler is not using lfiwax/lfiwzx assembler instruction
    for int to double conversion.
    
    Consider the following testcase:
    
    $cat intToDbl.C
    
    /******************************/
    
    double intToDbl(signed int *in)
    {
      return (double)(*in);
    }
    
    double intToDbl(signed int in)
    {
      return (double)(in);
    }
    
    double uintToDbl(unsigned int *in)
    {
      return (double)(*in);
    }
    
    double uintToDbl(unsigned int in)
    {
      return (double)(in);
    }
    /******************************/
    
    Compile the source file as:
    
    xlC -c -q64 -qlist -O2 intToDbl.C -qarch=pwr7
    
    
    Review output in intToDbl.lst file:
    
    ...
    ...
    
         | 000000                           PDEF     intToDbl(int *)
         | 000000                           AKA       intToDbl__FPi
        3|                                  PROC      in,gr3
        5| 000000 lwa      E8030002   1     L4A
    gr0=(int)(gr3,0)
        5| 000004 std      F801FFF0   1     ST8
    #MX_CONVF1_0(gr1,-16)=gr0
        5| 000008 lfd      C801FFF0   1     LFL
    vs0=#MX_CONVF1_0(gr1,-16)
        5| 00000C xscvsxdd F02005E0   1     FCFID     vs1=vs0,fcr
    
    
    Instead, the compiler should generate a lfiwax + xscvsxdd
    sequence:
    
    | 000000                           PDEF     intToDbl(int *)
         | 000000                           AKA       intToDbl__FPi
        1|                                  PROC      in,gr3
        3| 000000 lfiwax   7C001EAE   1     LFIWAX
    vs0=(int)(gr3,0)
        3| 000004 xscvsxdd F02005E0   1     FCFID     vs1=vs0,fcr
    

Local fix

  • Not applicable
    

Problem summary

  • compiler does not uses lfiwax/lfiwzx instructions for int to
    float conversion with -q64
    

Problem conclusion

  • Relaxing the opportunity check code to use new instruction with
    -q64
    

Temporary fix

Comments

APAR Information

  • APAR number

    IV37628

  • Reported component name

    XL C/C++ FOR AI

  • Reported component ID

    5725C7200

  • Reported release

    C10

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2013-03-05

  • Closed date

    2013-03-12

  • Last modified date

    2013-03-13

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

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

    LI77362 LI77420 IV44277 IV44284

Fix information

  • Fixed component name

    XL C FOR AIX

  • Fixed component ID

    5725C7100

Applicable component levels

  • RC10 PSY U858497

       UP C



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Document information


More support for:

XL C for AIX
Compiler

Software version:

12.1

Reference #:

IV37628

Modified date:

2013-03-13

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