error C2719: 'a': formal parameter with __declspec(align('16')) won't be aligned

Question

I try to use the mmx to implement the sse2 intrinsics functions because my code has a heavy call to them while I must make it run on old cpu.

typedef __declspec(align(16)) struct {
    __m64 v64[2];
} ___m128i;

#define __m128i ___m128i

__inline __m128i
dcm_add_epi8(__m128i a, __m128i b)
{
    __m128i x;
    x.v64[0] = _mm_add_pi8(a.v64[0], b.v64[0]);
    x.v64[1] = _mm_add_pi8(a.v64[1], b.v64[1]);
    return x;
}

but when I compile the code, the vc2008 compiler reports:

error C2719: 'a': formal parameter with __declspec(align('16')) won't be aligned

error C2719: 'b': formal parameter with __declspec(align('16')) won't be aligned

Answer 1

Hello hurric,

Error C2719 specifies that 'The align __declspec modifier is not permitted on function parameters'. [http://msdn.microsoft.com/en-us/library/373ak2y1(VS.71).aspx]

Hence instead of passing the parameters as objects, you can pass them as pointers to objects.

i.e.

typedef __declspec(align(16)) struct {
    __m64 v64[2];
} ___m128i;

#define __m128i ___m128i

__inline __m128i
dcm_add_epi8(__m128i* a, __m128i* b) 
{
    __m128i x;
    x.v64[0] = _mm_add_pi8(a->v64[0], b->v64[0]);
    x.v64[1] = _mm_add_pi8(a->v64[1], b->v64[1]);
    return x;
}

 

Hope this helps