IV37038: INEFFICIENT CODE FOR VEC_ANY

Fixes are available

APAR status

Closed as program error.

Error description

The following test case shows how the compiler produces
non-optimal code:

====Compile Line:
xlC -q64 -O2 -qarch=pwr7 -c -qlist -qaltivec test.C

====Testcase:
$ cat test.C
#include <builtins.h>

extern "C" bool vec_nan(vector double x)
{
  return vec_any_nan(x);
}
$

Generates:
     | 000000                           PDEF     vec_nan
    4|                                  PROC      x,vs34
    6| 000000 xvcmpeqd F002171E   1     VCDCEQ_R
vs0,cr6=vs34,vs34
    6| 000004 mfcr     7C102026   1     LFCR1     gr0=cr6,6
    6| 000008 rlwinm   5400CFFE   1     RN4       gr0=gr0,25,0x1
    6| 00000C subfic   20000001   1     SUBC      gr0,ca=1,gr0
    6| 000010 cntlzw   7C030034   1     CNTLZ4    gr3=gr0
    6| 000014 addi     3803FFE0   1     AI        gr0=gr3,-32
    6| 000018 rlwinm   54030FFE   1     SRL4      gr3=gr0,31
    7| 00001C bclr     4E800020   1     BA        lr

Optimal code:
     | 000000                           PDEF     vec_nan_opt
    9|                                  PROC      x,vs34
   11| 000030 xvcmpeqd F002171E   1     VCDCEQ_R
vs0,cr6=vs34,vs34
   11| 000034 addi     38600001   1     LI        gr3=1
   11| 000038 bclr     4C980020   1     BF
CL.3,cr6,0x1/lt,taken=50%(0,0)
   11| 00003C addi     38600000   1     LI        gr3=0
   12|                              CL.3:
   12| 000040 bclr     4E800020   1     BA        lr

Local fix

The optimal code can be created using:
extern "C" bool vec_nan_opt(vector double x)
{
  return vec_any_ne(x,x);
}

Problem summary

USERS AFFECTED:
Users that want peak performance using the vec_any_nan builtin
may be affected by this issue.

PROBLEM DESCRIPTION:
There have been minor performance issues for the vec_any_nan
builtin function that may not be noticable, but can potentially
add up if numerous calls are made.

Problem conclusion

The minor performance issues for vec_any_nan builtin have been
improved.

Temporary fix

Comments

APAR Information

APAR number
IV37038
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 / Xsystem
Submitted date
2013-02-20
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:

LI77366

Fix information

Fixed component name
XL C FOR AIX
Fixed component ID
5725C7100

Applicable component levels

RC10 PSY UP
C

[{"Business Unit":{"code":"BU048","label":"IBM Software"},"Product":{"code":"SSGH2K","label":"XL C for AIX"},"Component":"","ARM Category":[],"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"12.1","Edition":"","Line of Business":{"code":"LOB73","label":"Power TPS"}}]

Document Information

Modified date:
21 August 2024

Tips

IV37038: INEFFICIENT CODE FOR VEC_ANY_NAN

Fixes are available

Subscribe

APAR status

Closed as program error.

Error description

Local fix

Problem summary

Problem conclusion

Temporary fix

Comments

APAR Information

APAR number

Reported component name

Reported component ID

Reported release

Status

PE

HIPER

Special Attention

Submitted date

Closed date

Last modified date

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

Fixed component ID

Applicable component levels

RC10 PSY UP

Document Information

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