[Bug ipa/98594] [11 Regression] IPA modref codegen bug

[hubicka at gcc dot gnu.org]

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?