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* [Bug c/46419] New: xmmintrin.h: _mm_cvtpu16_ps (and hence _mm_cvtpu8_ps) returns false result in gcc >= 4.4
@ 2010-11-10 20:39 release_candidate at yahoo dot com
  2010-11-10 22:14 ` [Bug target/46419] [4.4, 4.5, 4.6 Regression] _mm_cvtpu16_ps (and hence _mm_cvtpu8_ps) returns false result ubizjak at gmail dot com
                   ` (5 more replies)
  0 siblings, 6 replies; 7+ messages in thread
From: release_candidate at yahoo dot com @ 2010-11-10 20:39 UTC (permalink / raw)
  To: gcc-bugs

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46419

           Summary: xmmintrin.h: _mm_cvtpu16_ps (and hence _mm_cvtpu8_ps)
                    returns false result in gcc >= 4.4
           Product: gcc
           Version: 4.4.5
            Status: UNCONFIRMED
          Severity: critical
          Priority: P3
         Component: c
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: release_candidate@yahoo.com


Created attachment 22367
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=22367
example code

Dear GCC developers,

I guess the patch set
<http://gcc.gnu.org/viewcvs?view=revision&revision=134558> broke the
_mm_cvtpu16_ps() and _mm_cvtpu8_ps() intrinsics.

For demonstration, please refer to the attached example. It is intended to
convert four chars (1,2,3,4) into a SSE float vector type (__m128) by using the
Intel intrinsics _mm_cvtpu8_ps() and _mm_setr_pi8().

The output of the program compiled with gcc-4.3 is:
    image: 1 2 3 4
    out4:  1 2 3 4
This result is correct, and complies with Intel's intrinsic docs 
<http://software.intel.com/sites/products/documentation/studio/composer/en-us/2011/compiler_c/intref_cls/common/intref_mmx_set.htm>
//
<http://software.intel.com/sites/products/documentation/studio/composer/en-us/2011/compiler_c/intref_cls/common/intref_sse_conversion.htm>,
as well as the output of icc compilation.

The output of gcc-4.4 and gcc-4.5 compilation is:
    image: 1 2 3 4
    out4:  3 4 1 2


I was able to trace this back the change set referred above. If I include the
old xmmintrin.h instead of the new header when using gcc-4.4, the result is
correct again. I didn't study the changes of rev. 134558  in detail, and I do
not know if the new algorithm is theoretically correct at all.


Could you please fix this bug?
I don't know about the other intrinsics touched by that patch.
Within this context, concerning the bug
<http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37496> might also be worth while.


Thanks,

Dirk


^ permalink raw reply	[flat|nested] 7+ messages in thread
end of thread, other threads:[~2011-03-09 16:42 UTC | newest]

Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2010-11-10 20:39 [Bug c/46419] New: xmmintrin.h: _mm_cvtpu16_ps (and hence _mm_cvtpu8_ps) returns false result in gcc >= 4.4 release_candidate at yahoo dot com
2010-11-10 22:14 ` [Bug target/46419] [4.4, 4.5, 4.6 Regression] _mm_cvtpu16_ps (and hence _mm_cvtpu8_ps) returns false result ubizjak at gmail dot com
2010-11-10 23:00 ` uros at gcc dot gnu.org
2010-11-10 23:27 ` uros at gcc dot gnu.org
2010-11-10 23:28 ` uros at gcc dot gnu.org
2010-11-10 23:30 ` ubizjak at gmail dot com
2011-03-09 16:42 ` ubizjak at gmail dot com

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