On Tue, Aug 11, 2015 at 9:49 PM, Jeff Law <l...@redhat.com> wrote: > On 08/06/2015 04:25 AM, Mikael Morin wrote: >> >> Hello, >> >> this avoids an error found with bootstrap-ubsan. >> Regression tested on x86_64-unknown-linux-gnu. OK for trunk? >> >> Mikael >> >> >> noub_sext.CL >> >> >> 2015-08-05 Mikael Morin<mik...@gcc.gnu.org> >> >> * hwint.h (sext_hwi): Rewrite without undefined behaviour on >> negative SRC. > > OK. Hopefully most of the time the precision is known at compile-time which > would allow for optimization of the resulting code back to the > pair-of-shifts form by combine.
I think it is not. The code also lacks a comment on why we do this kind of obfuscation. What kind of error does ubsan run into? That is, for which 'prec'? Richard. > > > > jeff >