question on verify_ssa failure due to ccp in dom3 (PR30784)

[Dorit Nuzman]

Hi,

We have a '{2,2}' expression (vector initializer) propagated by dom into a
BIT_FIELD_REF:

before (bug.c.105t.vrp2):

      vector long int vect_cst_.47;
      vect_cst_.47_66 = {2, 2};
      D.2103_79 = BIT_FIELD_REF <vect_cst_.47_66, 64, 0>;

after (bug.c.106t.dom3):
      "
      Optimizing block #7

      Optimizing statement <L0>:;
      Optimizing statement D.2102_78 = BIT_FIELD_REF <vect_vec_iv_.48_67,
64, 0>;
      Optimizing statement D.2103_79 = BIT_FIELD_REF <vect_cst_.47_66, 64,
0>;
      Replaced 'vect_cst_.47_66' with constant '{2, 2}'
      "

      D.2103_79 = BIT_FIELD_REF <{2, 2}, 64, 0>;


...which causes he following ICE:
"
   bug.c:8: error: invalid reference prefix
   {2, 2}
   bug.c:8: internal compiler error: verify_stmts failed
"

Several testcases are available in the bugzilla report (PR30784).

So, the question is - what needs to be fixed - is it copy propagation that
allows propagating the initializer into a BIT_FIELD_REF? or vect_lower pass
that creates these BIT_FIELD_REFs after vectorization?

thanks,
dorit