[Bug middle-end/109849] suboptimal code for vector walking loop

[hubicka at ucw dot cz via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109849

--- Comment #5 from Jan Hubicka <hubicka at ucw dot cz> ---
> Actually why didn't we copy the loop header in the first place?
Because it is considered to be do-while loop already (thanks to
the in-loop conitional, do_while_loop_p is happy).