On 18 March 2014 14:47, Peter Maydell <peter.mayd...@linaro.org> wrote: > On 18 March 2014 14:39, Richard Henderson <r...@twiddle.net> wrote: >> On 03/18/2014 07:25 AM, Peter Maydell wrote: >>> Why do you think this? tcg/README says out of >>> range shifts are undefined behaviour. That means we >>> mustn't execute them, and this code doesn't attempt >>> to branch around or otherwise avoid the shift by -1. >> >> Bah. Stuff and nonsense. None of our backends are so >> stupid as to start WWIII with an out of range input. > > Then we should document that this case is an > unspecified-result, not use the same term we > do for division-by-zero or division-overflow (which > really can cause things to blow up).
Mailing thread from last time around: http://lists.gnu.org/archive/html/qemu-devel/2012-09/msg02562.html I don't particularly object to changing to "undefined result" if you want to audit the backends and the optimizer... thanks -- PMM
