[Bug tree-optimization/59387] [4.9 Regression] wrong code (hangs) at -Os on x86_64-linux-gnu

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59387

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Note already the chrec is {c_lsm.11_15, +, -1}_2 with char type everywhere (but
the 2 which is int, but that is irrelevant), so the information that the
decrement was performed carefully in non-wrapping type is lost at that point.
Dunno if we want and whether it would be possible to generate a chrec with
unsigned char type in that case instead
(i.e. (char) {(unsigned char)c_lsm.11_15, +, 255}_2 instead), or some special
bit on the chrec to tell us that it is wrapping.