On 4/20/20 8:10 AM, Stephen Long wrote:
> +#define DO_FP_MATRIX_MUL(NAME, TYPE, H) \
> +void HELPER(NAME)(void *vd, void *va, void *vn, void *vm, \
> + void *status, uint32_t desc) \
> +{ \
> + intptr_t s, i, j; \
> + intptr_t opr_sz = simd_oprsz(desc) / (sizeof(TYPE) >> 2); \
> + \
> + for (s = 0; s < opr_sz; ++s) { \
> + TYPE *n = vn + s * (sizeof(TYPE) >> 2); \
> + TYPE *m = vm + s * (sizeof(TYPE) >> 2); \
> + TYPE *a = va + s * (sizeof(TYPE) >> 2); \
> + TYPE *d = vd + s * (sizeof(TYPE) >> 2); \
> + \
> + for (i = 0; i < 1; ++i) { \
> + for (j = 0; j < 1; ++j) { \
> + TYPE addend = a[H(2*i + j)]; \
> + \
> + TYPE nn0 = n[H(2*i)]; \
> + TYPE mm0 = m[H(2*j)]; \
> + TYPE prod0 = TYPE##_mul(nn0, mm0, status); \
> + \
> + TYPE nn1 = n[H4(2*i + 1)]; \
> + TYPE mm1 = m[H4(2*j + 1)]; \
> + TYPE prod1 = TYPE##_mul(nn1, mm1, status); \
> + \
> + TYPE sum = TYPE##_add(prod0, prod1, status); \
> + d[H(2*i + j)] = TYPE##_add(sum, addend, status); \
> + } \
> + } \
This has a read-after-write problem, when D overlaps any of the inputs. You
need to read all of the inputs before writing anything.
It might be easiest to just unroll these two inner loops:
TYPE n00 = n[0], n01 = n[1], n10 = n[2], n11 = n[3];
TYPE m00 = m[0], m01 = m[1], m10 = m[2], m11 = m[3];
TYPE p0, p1;
// i = 0, j = 0
p0 = mul(n00, m00, status);
p1 = mul(n01, m01, status);
a[0] = add(a[0], add(p0, p1, status), status);
// i = 0, j = 1
p0 = mul(n00, m10, status);
p1 = mul(n01, m11, status);
a[1] = add(a[1], add(p0, p1, status), status);
...
r~
