[Bug rtl-optimization/110791] [12/13/14 Regression] arm: Wrong code with -Os -march=armv8.1-m.main

[acoplan at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110791

--- Comment #2 from Alex Coplan <acoplan at gcc dot gnu.org> ---
(In reply to Xi Ruoyao from comment #1)
> Isn't this a UB?
> 
>   while (p >= path && *p != '/')
>     p--;
> 
> This will cause p to become "&main::path[0] - 1".  C23 6.5.6p9:

In this case, with the input given in main, I think p should end up pointing to
main::path + 1 (since we pass in main::path + 2, and foo can only ever
decrement p at most one below its parameter path).