On 15 June 2012 20:04, Marc Glisse <marc.gli...@inria.fr> wrote: > On Fri, 15 Jun 2012, Ramana Radhakrishnan wrote: > >> On 15 June 2012 18:18, Marc Glisse <marc.gli...@inria.fr> wrote: >>> >>> On Fri, 15 Jun 2012, Ramana Radhakrishnan wrote: >>> >>>>> I just noticed this part. Rereading my comment in >>>>> >>>>> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51033#c22 >>>> >>>> >>>> >>>> I haven't been able to make it break with -std=c++11 . Is there >>>> something I'm missing here ? >>> >>> >>> >>> I don't remember. It might just be that trying to create a constexpr >>> vector >>> variable or calling __builtin_shuffle on it ICEs instead of giving an >>> error. >>> I can keep a note to make some tests at the end of July (I will be mostly >>> away until then), but I believe the code from comment 22 is safer than >>> the >>> one from comment 20, if memory serves. >> >> >> I'm not qualified enough to take a call on what's better in this case >> and will have to defer to Jason and the C++ maintainers on this one. >> >> Now that you've said this I decided to go back and throw more tests >> through it >> I've tried to chug through most of the testcases for __builtin_shuffle >> including a few of my own the simplest of which I show below trying to >> trigger this issue but can't seem to do so. > > > Maybe something like: > > #include <x86intrin.h> > int main(){ > constexpr __m128d x={1.,2.}; > constexpr __m128i y={1,0}; > constexpr __m128d z=__builtin_shuffle(x,y); > } > > ? > (sorry for the x86 specific code, should be easy to adapt)
Thanks for the example and your patience - just shows my ignorance with C++11 :( . I'll try to have a look at this later today and see if I can come up with something and possibly integrating that bit of your patch. > > See also: > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53094 > > Long term, vectors should be literals. But we need something to avoid > crashes on operator[] and __builtin_shuffle (ideally implementing the > constant version of them). Keeping vectors as non-literals (what I was > suggesting) is quite a crude hack. Maybe having them as literals now is a > good thing, but it would be good to avoid the ICEs. Agreed that the compiler shouldn't crash in these cases now that I understand finally what you meant. Have a good break. Thanks, Ramana > > -- > Marc Glisse
