-;
-; If b' is 1, we need to do other adjustements. The first thought is the
-; following (note that r' will not always have the right value, but an
-; adjustement follows further down):
-;
-; if (b' == 1)
-; {
-; q' = q''
-; r' = a - q'*b
-;
-; However, one can note the folowing relationship:
-;
-; r'' = a2 - q''*b2
-; => 2*r'' = 2*a2 - 2*q''*b2
-; = { a = 2*a2 + a', b = 2*b2 + b' = 2*b2 + 1,
-; q' = q'' }
-; = a - a' - q'*(b - 1)
-; = a - q'*b - a' + q'
-; = r' - a' + q'
-; => r' = 2*r'' - q' + a'
-;
-; This enables us to use r'' instead of discarding and calculating another
-; modulo:
-;
-; if (b' == 1)