[Bug testsuite/87739] new test case gcc.dg/tree-ssa/pr84436-5.c fails with its introduction in r265463

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87739

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
signed vs. unsigned char