[Bug c/59961] Use of size_t in leading term of computation with subtraction

[olaf at robots dot ox.ac.uk]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59961

--- Comment #3 from Olaf <olaf at robots dot ox.ac.uk> ---
Well... naive me found it quite surprising and unexpected that the following
two lines produce grossly different results:

double result1 = -s1*d1 + s2*d2;
double result2 =  s2*d2 - s1*d1;

...but never mind.