[Bug middle-end/33780] different results between O3 and O0

[rguenth at gcc dot gnu dot org]

------- Comment #5 from rguenth at gcc dot gnu dot org  2008-02-05 11:08 -------
The difference with your last testcase is indeed that we unroll the loop
setting c[] and constant-fold the result by computing the integral powers
with 0.5ulp precision (and a single rounding(!)).  But all your other
computations involve intermediate roundings, so this is still invalid IMHO.

Or are you complaining that we constant fold integer powers as if they were
non-integer powers (not using the fact that Fortran would allow expansion
to multiple FLOPs)?


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33780