https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98594
--- Comment #4 from rguenther at suse dot de <rguenther at suse dot de> --- On Wed, 27 Jan 2021, hubicka at gcc dot gnu.org wrote: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98594 > > --- Comment #3 from Jan Hubicka <hubicka at gcc dot gnu.org> --- > The initialization is removed by dse1 pass. We get: > ipa-modref: call stmt D.3199 = bitCount::bitCount_bitfield<1, int, > glm::packed_highp> (&D.3185); [return slot optimization] > ipa-modref: call to glm::vec<L, int, Q> bitCount::bitCount_bitfield(const > glm::vec<L, T, Q>&) [with int L = 1; T = int; glm::qualifier Q = > glm::packed_highp]/8 does not use ref: D.3185.D.3097.x alias sets: 3->1 > Deleted dead store: D.3185.D.3097.x = x_2(D); > > > ipa-modref: call stmt D.3199 = bitCount::bitCount_bitfield<1, int, > glm::packed_highp> (&D.3185); [return slot optimization] > ipa-modref: call to glm::vec<L, int, Q> bitCount::bitCount_bitfield(const > glm::vec<L, T, Q>&) [with int L = 1; T = int; glm::qualifier Q = > glm::packed_highp]/8 does not use ref: D.3185 alias sets: 3->3 > Deleted dead store: D.3185 ={v} {CLOBBER}; > > > Now the modref summary for function is > loads: > > Limits: 32 bases, 16 refs > > Base 0: alias set 5 > > Ref 0: alias set 5 > > access: Parm 0 param offset:0 offset:0 size:32 max_size:32 > > > alias set 5 correspond to const struct vec but diferent instantiation than > alias set 3 used in the store. > There is reinterpret cast: > > glm::vec<L, typename glm::detail::make_unsigned<T>::type, Q> x(*reinterpret_cast< glm::vec<L, typename glm::detail::make_unsigned<T>::type, Q> const *>(&v)); > > turning it to > > glm::vec<L, typename glm::detail::make_unsigned<T>::type, Q> x(*(&v)); > > makes the aliasing difference go away. So it seems to me that the testcase > simply includes TBAA violation? Not sure but if my visuals do not cheat me then the difference is only const qualification so it should not matter for TBAA? Of course the question is what type 'v' has since this maybe invokes a different CTOR?
