XXH_get32bits
v1 = XXH32_round(v1, XXH_get32bits(p)); p+=4;
v2 = XXH32_round(v2, XXH_get32bits(p)); p+=4;
v3 = XXH32_round(v3, XXH_get32bits(p)); p+=4;
v4 = XXH32_round(v4, XXH_get32bits(p)); p+=4;
h32 += XXH_get32bits(p) * PRIME32_3;
h64 ^= (U64)(XXH_get32bits(p)) * PRIME64_1;