Why does this code execute more slowly after strength-reducing multiplications?
In the post, multiplications and 2 additions are not faster than 2 additions.The post compares (1) loop code that can be vectorized, as loop rounds are independent and do not depend on the result from the previous round, and (2) an "optimization" that makes calculations shorter, but also makes each loop round depend on the result of the previous round, so this cannot be vectorized.