[Bug c/84121] optimizer breaks code without -frwapv, but -Wall -Wextra show no warnings

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84121

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |INVALID

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
    int fac = 1-x, prod = 1+fac;
    while (fac) {
        printf("fac=%d\n",fac);
        prod *= 1 + (fac*=fac);
    }

this loop will never exit because if fac is not zero at entry and fac *= fac
will
never make it zero because we can assume that overflow will not happen.