6 * In 2's complement arithmetric, -x == (~x + 1), so
7 * -{h,l} = (~{h,l} + {0,1)
8 * -{h,l} = {~h,~l} + {0,1}
9 * -{h,l} = {~h + cy, ~l + 1}
10 * ... where cy = (l == 0)
11 * -{h,l} = {~h + cy, -l}
16 .type __negdi2,@function
25 .size __negdi2, .-__negdi2