https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91526
--- Comment #7 from joseph at codesourcery dot com <joseph at codesourcery dot com> --- There's more or less the same ABI question as in bug 91398 about whether there is any constraint on the called function writing to the return value slot in cases where it does not return normally. Supposing the ABI allows the return value slot (register or memory) to be written to by the called function even if it does not end up returning normally, then the optimization in this bug would be valid, while that in bug 91398 would not be valid if non-normal return is a possibility. (The example in the present bug also doesn't allow non-normal return, unless we say longjmp from a SIGFPE handler is OK - is -fnon-call-exceptions only needed for language exceptions or also for longjmp?) (Validity would also depend on it not affecting the observed address of the variable "result" in such a way as to make it equal to the observed address of some object in a calling function - but I expect the interesting cases for this optimization are where the variable is only stored to, not ones where addresses get compared, if it's even possible for the same return value slot to get used in more than one function on the call stack.)
