[Bug tree-optimization/81555] Wrong code at -O1

[glisse at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81555

--- Comment #3 from Marc Glisse <glisse at gcc dot gnu.org> ---
(In reply to Dmitry Babokin from comment #2)
> Hmmm, but this one is triggered at -O1, another only at -O2.

-fno-tree-reassoc should help both.

It is often a combination of optimizations that causes the bug. Reassoc is
doing a good transformation, but it leaves wrong information around, which only
matters if some other pass (rightfully) takes advantage of that information.
Still, it was good to report both, and I expect we may add (a modified version
of) both to the testsuite once this is fixed, thanks.