[Bug tree-optimization/82776] Unable to optimize the loop when iteration count is unavailable.

[glisse at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82776

--- Comment #1 from Marc Glisse <glisse at gcc dot gnu.org> ---
That could be because gcc sadly refuses to optimize away infinite loops
(happens for other cases, and cddce2 dump (the pass that removes the whole
thing when the macro is defined) says "can not prove finiteness of loop 2").
Although ++chunk_ should be enough to prove that the loop terminates (otherwise
chunk_ eventually overflows).

(the unaligned vector use in this code seems strange)