[Bug tree-optimization/96807] Division by zero produces zero with gcc -O2

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96807

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Division by zero is undefined behavior so we simplify 1/x to 0 if x is known
to be not one [unless there's literal 1/0 which is sometimes used to generate
traps].