On August 12, 2015 8:07:13 PM GMT+02:00, Jeff Law <l...@redhat.com> wrote: >On 08/12/2015 11:12 AM, Richard Biener wrote: > >> >> Prec is almost never a constant and is heavily used from wide-int. >> >> We are not exploiting this undefined ness in C so I object to making >this so much slower. >> >> Can we instead do what we do for abs_hwi and add a checking assert so >we can move the tests to the callers that misbehave instead? >Given that ISO C++ is moving away from making shifting 1 into the sign >bit undefined behaviour, maybe we should make UBSan less strict in its >warning. That may eliminate the need for Mikael's patch.
We can also use an logical left shift followed by an arithmetic right shift. Or is the latter invoking undefined behaviour as well in some cases we hit? Richard. >jeff
