[LLVMdev] [clang] SSE2 intrinsics (emmintrin.h): _mm_movpi64_pi64 should be _mm_movpi64_epi64?

[Alexey Dokuchaev]

Hi there,

I've recently encountered a piece of code that uses some SSE2 intrinsics
and builds with gcc46, but not clang: clang can't find _mm_movpi64_epi64(),
while gcc46 defines it in its lib/gcc46/gcc/.../4.6.3/include/emmintrin.h:

  extern __inline __m128i __attribute__((__gnu_inline__, __always_inline__, __artificial__))
  _mm_movpi64_epi64 (__m64 __A)
  {
    return _mm_set_epi64 ((__m64)0LL, __A);
  }

  extern __inline __m128i __attribute__((__gnu_inline__, __always_inline__, __artificial__))
  _mm_set_epi64x (long long __q1, long long __q0)
  {
    return __extension__ (__m128i)(__v2di){ __q0, __q1 };
  }

Now, Clang in /usr/include/clang/3.3/emmintrin.h defines similar function,
but without the `e', _mm_movpi64_pi64():

  static __inline__ __m128i __attribute__((__always_inline__, __nodebug__))
  _mm_movpi64_pi64(__m64 __a)
  {
    return (__m128i){ (long long)__a, 0 };
  }

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 manual [1]:

  _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)			<<< TYPO?!
  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().

./danfe

[1] http://software.intel.com/sites/products/documentation/doclib/iss/2013/compiler/cpp-lin/GUID-AFA947A7-8490-443B-9946-C7B16C8E6244.htm