int64_t __int64_mul_asgn(int64_t *muliplicand, int64_t multiplier);
__int64_mul_asgn updates the 64-bit signed integer pointed to by multiplicand by multiplying it by multiplier. The product is returned as the result. As only the lower 64 bits of the product are returned, __int64_mul_asgn returns correct products, modulo 64 bits, for both signed and unsigned arguments.