Sse segfault on _mm_load_si128

I have a segmentation fault when I try to use _mm_load_si128 in C for inline functions. I've seen that the data needs to be 16-bit aligned, and that concatenation does it right. But that doesn't solve my problem.

#include <xmmintrin.h>

int main(void){
    const int N = 8;
    short int  matrice1[] = {
        10, 11, 12, 13, 14, 15, 16, 17,
        20, 21, 22, 23, 24, 25, 26, 27,
        30, 31, 32, 33, 34, 35, 36, 37,
        40, 41, 42, 43, 44, 45, 46, 47,
        50, 51, 52, 53, 54, 55, 56, 57,
        60, 61, 62, 63, 64, 65, 66, 67,
        70, 71, 72, 73, 74, 75, 76, 77,
        80, 81, 82, 83, 84, 85, 86, 87
    };

    transpose_simd(matrice1, N);

 return 0;
}

union Line{
    short int* row;
    __m128i sRow;
};

void transpose_simd(short int * matrice1, int N){
    short int i, n, j;

    union Line line1, line2; //matrix line

    __m128i sLine1, sLine2; //sse version of the matrix line
    __m128i sLine3, sLine4;

    /*
    There will be a loop surrounding the following code, but first I kept it simple
    */
            // THE NEXT LINE GIVES A SEGMENTATION FAULT
            sLine1 = _mm_load_si128((__m128i*) line1.row); //loads 1 matrix line (8 shorts of 16 bits = 128)
            sLine2 = _mm_load_si128((__m128i*) line2.row);

            sLine3 = _mm_unpackhi_epi16 ( sLine1, sLine2 ); //shuffle the first 4 elements
            sLine4 = _mm_unpackhi_epi16 ( sLine1, sLine2 ); //shuffle the last 4 elements

            _mm_store_si128((__m128i*)line1.row, sLine3);
            _mm_store_si128((__m128i*)line2.row, sLine4);
}

      

        
        
        
      

    

So I got the solution from the answers. It works great after properly implementing two loops:

void transpose_simd(short int * matrice1, short int* matrice2, int N){
    short int i=0, n=0;

    short int* __attribute__ ((aligned (16))) line1; //ligne de matrice
    short int* __attribute__ ((aligned (16))) line2;

    __m128i sLine1, sLine2; //ligne en version sse
    __m128i sLine3, sLine4;

    /*
    There will be a loop surrounding the following code, but first I kept it simple
    */

            line1 = matrice1 + N*i;
            line2 = matrice1 + N*(N/2 + i);

            sLine1 = _mm_loadu_si128((__m128i*) line1); //charge 1 ligne (8 nombres de 16 bits = 128, "coup de bol")
            sLine2 = _mm_loadu_si128((__m128i*) line2);

            sLine3 = _mm_unpacklo_epi16 ( sLine1, sLine2 ); //shuffle les 4 premiers chiffres de line1, voir p74
            sLine4 = _mm_unpackhi_epi16 ( sLine1, sLine2 ); //shuffle les 4 premiers chiffres de line1, voir p74

            _mm_storeu_si128((__m128i*) (matrice2 + N*2*i), sLine3);
            _mm_storeu_si128((__m128i*) (matrice2 + N*(2*i+1)), sLine4);

}

      

        
        
        
      

    

Basically, __attribute__ ((aligned (16)))

aligns my variables, as the union retains the offset but does not set the alignment. In addition, asymmetric functions _mm_storeu_si128

and _mm_loadu_si128 are used for greater security . However, I don't know if this is slower than the alignment-dependent version of these methods.