#include <xmmintrin.h>

//~2.4x faster than non-SSE unrolled version.
//Uses row-major order (D3D or non-OpenGL layout).
void mul(float result[4][4], float a[4][4], float b[4][4])
{
    __m128 otherRow0 = _mm_loadu_ps(b[0]);
    __m128 otherRow1 = _mm_loadu_ps(b[1]);
    __m128 otherRow2 = _mm_loadu_ps(b[2]);
    __m128 otherRow3 = _mm_loadu_ps(b[3]);

    __m128 newRow0 = _mm_mul_ps(otherRow0, _mm_set1_ps(a[0][0]));
    newRow0 = _mm_add_ps(newRow0, _mm_mul_ps(otherRow1, _mm_set1_ps(a[0][1])));
    newRow0 = _mm_add_ps(newRow0, _mm_mul_ps(otherRow2, _mm_set1_ps(a[0][2])));
    newRow0 = _mm_add_ps(newRow0, _mm_mul_ps(otherRow3, _mm_set1_ps(a[0][3])));

    __m128 newRow1 = _mm_mul_ps(otherRow0, _mm_set1_ps(a[1][0]));
    newRow1 = _mm_add_ps(newRow1, _mm_mul_ps(otherRow1, _mm_set1_ps(a[1][1])));
    newRow1 = _mm_add_ps(newRow1, _mm_mul_ps(otherRow2, _mm_set1_ps(a[1][2])));
    newRow1 = _mm_add_ps(newRow1, _mm_mul_ps(otherRow3, _mm_set1_ps(a[1][3])));

    __m128 newRow2 = _mm_mul_ps(otherRow0, _mm_set1_ps(a[2][0]));
    newRow2 = _mm_add_ps(newRow2, _mm_mul_ps(otherRow1, _mm_set1_ps(a[2][1])));
    newRow2 = _mm_add_ps(newRow2, _mm_mul_ps(otherRow2, _mm_set1_ps(a[2][2])));
    newRow2 = _mm_add_ps(newRow2, _mm_mul_ps(otherRow3, _mm_set1_ps(a[2][3])));

    __m128 newRow3 = _mm_mul_ps(otherRow0, _mm_set1_ps(a[3][0]));
    newRow3 = _mm_add_ps(newRow3, _mm_mul_ps(otherRow1, _mm_set1_ps(a[3][1])));
    newRow3 = _mm_add_ps(newRow3, _mm_mul_ps(otherRow2, _mm_set1_ps(a[3][2])));
    newRow3 = _mm_add_ps(newRow3, _mm_mul_ps(otherRow3, _mm_set1_ps(a[3][3])));

    _mm_storeu_ps(result[0], newRow0);
    _mm_storeu_ps(result[1], newRow1);
    _mm_storeu_ps(result[2], newRow2);
    _mm_storeu_ps(result[3], newRow3);
}