edx:eax = edx * 2^32 + eax (mod 2^32-1)= ((edx * 2^32) mod 2^32-1 + eax (mod 2^32-1)) mod 2^32-1= (edx + eax) mod 2^32-1There are some corner cases, however, that you might want to check. Example 3650476437 * 2908093780. While the result is correct mod 2^32-1, it is not reduced (i.e. [0, 2^32-2]).It's a cool trick, though.
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