[Bug tree-optimization/79460] gcc fails to optimise out a trivial additive loop for seemingly arbitrary numbers of iterations

[segher at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79460

--- Comment #12 from Segher Boessenkool <segher at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #7)
> Shouldn't it (both in the vectorizer and in scev) be dependent not just on
> flag_fp_contract_mode but also on some -ffast-math subflag?  Doing several
> additions can e.g. raise different exceptions and have different roundings
> from doing it as just one multiply.

This needs -fassociative-math I think?