[Bug rtl-optimization/90311] [9 Regression] wrong code with -O and __builtin_add_overflow() and compare

[rearnsha at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90311

--- Comment #10 from Richard Earnshaw <rearnsha at gcc dot gnu.org> ---
Initial commit in the series was r10-3970 but there were certainly follow-ups
after that.