SSE2 intrinsics: gcc46 vs. clang contradiction

[Dimitry Andric]

On 02 Nov 2013, at 01:07, Dimitry Andric <dim at freebsd.org> wrote:
> On 01 Nov 2013, at 22:45, C. Bergström <cbergstrom at pathscale.com> wrote:
>> On 11/ 1/13 10:43 PM, Alexey Dokuchaev wrote:
>>> On Fri, Nov 01, 2013 at 07:46:45PM +0700, Alexey Dokuchaev wrote:
>>>> What adds to confusion, in their manual [1] Intel spells them differently
>>>> themselves: first, in the table, it says:
>>>> 
>>>>  _mm_movpi64_epi64		Move		MOVDQ2Q
>>>>              ^^^^^
>>>> 
>>>> Then later, when they describe what it does, it says:
>>>> 
>>>>  __m128i _mm_movpi64_pi64(__m64 a)
>>>>                      ^^^^
>>>>  Moves the 64 bits of a to the lower 64 bits of the result, zeroing the
>>>>  upper bits.
>>> Microsoft (http://msdn.microsoft.com/en-us/library/has3d153(v=vs.90).aspx)
>>> defines these two:
>>> 
>>>  _mm_movepi64_pi64		MOVDQ2Q			Move
>>>  _mm_movpi64_epi64		MOVQ2DQ			Move
>>> 
>>> That is:
>>> 
>>>  __m64 _mm_movepi64_pi64 (__m128i a);
>>>  MOVDQ2Q
>>>  r0 := a0 ;
>>> 
>>>  __m128i _mm_movpi64_epi64 (__m64 a);
>>>  MOVDQ2Q
>>>  r0 := a0 ; r1 := 0X0 ;
>>> 
>>> Cf. Intel's:
>>> 
>>>  _mm_movepi64_pi64		Move			MOVDQ2Q
>>>  _mm_movpi64_epi64		Move			MOVDQ2Q
>>> 
>>>  __m64 _mm_movepi64_pi64(__m128i a)
>>>  Returns the lower 64 bits of a as an __m64 type:	R0 := a0
>>> 
>>>  __m128i _mm_movpi64_pi64(__m64 a)
>>>  Moves the 64 bits of a to the lower 64 bits
>>>  of the result, zeroing the upper bits:		R0 := a0, R1 = 0X0
>>> 
>>> Assuming that both documents correctly assign instructions to function
>>> names (bonus clue: it also makes them symmetrical), then _mm_movpi64_pi64
>>> is indeed a typo and Clang's header is wrong, while GCC's is correct: it
>>> should read _mm_movpi64_epi64(), not _mm_movpi64_pi64().
>> Why isn't this being asked on the clang or llvm mailing list? Wouldn't this impact upstream as well?
> 
> Indeed, so redirecting to the cfe-commits list.  It looks like this incorrect function name has been in emmintrin.h since clang r61443 (by andersca).  Basically, we need the typo fixed as follows:
> 
> Index: tools/clang/lib/Headers/emmintrin.h
> ===================================================================
> --- tools/clang/lib/Headers/emmintrin.h (revision 193039)
> +++ tools/clang/lib/Headers/emmintrin.h (working copy)
> @@ -1366,7 +1366,7 @@ _mm_movepi64_pi64(__m128i __a)
> }
> 
> static __inline__ __m128i __attribute__((__always_inline__, __nodebug__))
> -_mm_movpi64_pi64(__m64 __a)
> +_mm_movpi64_epi64(__m64 __a)
> {
>   return (__m128i){ (long long)__a, 0 };
> }
> 
> Is this OK?

Ping... this is a one-character fix, please apply. :-)


-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 203 bytes
Desc: Message signed with OpenPGP using GPGMail
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20131106/eb143a25/attachment.sig>