[Bug target/104188] gcc omitting AVX-512 broadcast instruction

[kvr000 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104188

--- Comment #4 from Zbynek Vyskovsky <kvr000 at gmail dot com> ---
Sure, the code:

#include <stdio.h>

#ifndef NO_VECTORIZE
#ifdef __x86_64__
#include <immintrin.h>
#include <x86intrin.h>
#endif
#ifdef __aarch64__
#include <arm_neon.h>
#endif
#endif

typedef union Mat44 {
        float m[4][4];
#ifndef NO_VECTORIZE
#ifdef __x86_64__
        __m128 row[4];
        __m256 rowDuet[2];
        __m512 rowQuad;
#endif
#ifdef __aarch64__
        float32x4_t row[4];
#endif
#endif
} Mat44;

__attribute__((noipa)) void matmult_avx512(union Mat44 *out, const Mat44 *a,
const Mat44 *b)
{
        __m512 a0123 = _mm512_loadu_ps(a->m[0]);
        __m512 b0000 = _mm512_broadcast_f32x4(b->row[0]);
        __m512 b1111 = _mm512_broadcast_f32x4(b->row[1]);
        __m512 b2222 = _mm512_broadcast_f32x4(b->row[2]);
        __m512 b3333 = _mm512_broadcast_f32x4(b->row[3]);

        __m512 result = _mm512_mul_ps(_mm512_permute_ps(a0123, 0x00), b0000);
        result = _mm512_fmadd_ps(_mm512_permute_ps(a0123, 0x55), b1111,
result);
        result = _mm512_fmadd_ps(_mm512_permute_ps(a0123, 0xaa), b2222,
result);
        result = _mm512_fmadd_ps(_mm512_permute_ps(a0123, 0xff), b3333,
result);

        _mm512_storeu_ps(out->m[0], result);
}

__attribute__((noipa)) void matmult_ref(Mat44 *out, const Mat44 *a, const Mat44
*b)
{
        Mat44 t;
        for (int i = 0; i < 4; i++) {
                for (int j = 0; j < 4; j++) {
                        t.m[i][j] = a->m[i][0]*b->m[0][j] +
a->m[i][1]*b->m[1][j] + a->m[i][2]*b->m[2][j] + a->m[i][3]*b->m[3][j];
                }
        }

        *out = t;
}

int main(void)
{
        Mat44 in = { m: { { 1, 2, 3, 4 }, { 5, 6, 7, 8 }, { 9, 10, 11, 12 }, {
13, 14, 15, 16 } } };
        Mat44 avx512_out;
        Mat44 ref_out;
        matmult_ref(&ref_out, &in, &in);
        matmult_avx512(&avx512_out, &in, &in);
        for (int r = 0; r < 4; ++r) {
                printf("%5.0f %5.0f %5.0f %5.0f      %5.0f %5.0f %5.0f
%5.0f\n", avx512_out.m[r][0], avx512_out.m[r][1], avx512_out.m[r][2],
avx512_out.m[r][3], ref_out.m[r][0], ref_out.m[r][1], ref_out.m[r][2],
ref_out.m[r][3]);
        }
        return 0;
}


Output (note the repeating first column on first side, caused by duplicating
single element instead of four):

  90    90    90    90         90   100   110   120
 202   202   202   202        202   228   254   280
 314   314   314   314        314   356   398   440
 426   426   426   426        426   484   542   600