https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103440
--- Comment #3 from Andrew Macleod <amacleod at redhat dot com> --- I need to adjust the original patch, I shouldn't have continued the loop when dealing with equivalences. An equivalence is not the same as an undefined value... we might be able to ignore the range from it for calculation purposes, but we cannot ignore the fact that it is a different SSA_NAME and may contain a different value that we do care about. There are other checks in then loop which will allow us to assign an equivalence between the DEF and an argument if we are ignoring the other ssa_names.. such as when there are undefined values. a_3 = PHI <a_1(4), a_2(6)> if a_2 is undefined, we can create an equivalence between a_3 and a_1 as the value of a_2 is irrelevant and can be whatever we want it to be. if a_2 is instead an equivalence with a_3, we do not want to create an equivalence between a_3 and a_1 in this block as we may then turn it into a copy.. we'd only be able to do this if there was an equivalence between a_1 and a_2, and we are not checking that. Although we are may not be adding the range for a_2 into the cumulative knowledge of a_3's range, we do need to keep the edge to retain the copy as its value is important and could be different than the other argument... and we need to retain the copy when we go out of ssa.
