[Bug fortran/69368] [6 Regression] spec2006 test case 416.gamess fails with the g++ 6.0 compiler starting with r232508

[dominiq at lps dot ens.fr]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69368

--- Comment #65 from Dominique d'Humieres <dominiq at lps dot ens.fr> ---
> There is obviously no "rationale".  Fact is that we don't exploit the
> undefinedness explicitely but just as a side-effect of how CSE works in
> DOM now.  This means we don't propagate '1' as the only valid value of I
> but just CSE the last three loads to the first as we know they are the
> same (without knowing the actual value).

How can K(1) and K(2*1) be the same without using undefinedness explicitely?