[Bug tree-optimization/81573] [8 Regression] wrong code at -O3 on x86_64-linux-gnu

[rguenther at suse dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81573

--- Comment #8 from rguenther at suse dot de <rguenther at suse dot de> ---
On July 27, 2017 4:39:45 PM GMT+02:00, "seurer at gcc dot gnu.org"
<gcc-bugzilla@gcc.gnu.org> wrote:
>https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81573
>
>--- Comment #7 from seurer at gcc dot gnu.org ---
>The problem in the test case is that the code assumes "char" is signed.
> On
>power it is not.  So "b" starts at 0, is decremented to 255, and
>...etc...  
>The for loop will run forever.

Sorry.  Can you commit the obvious fix making it explicitly signed char?