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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/99919] [11/12/13/14 Regression] bogus
 -Wmaybe-uninitialized with a _Bool bit-field
Date: Fri, 15 Dec 2023 13:33:56 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D99919

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|2021-11-30 00:00:00         |2023-12-15
                 CC|                            |jamborm at gcc dot gnu.org

--- Comment #10 from Richard Biener <rguenth at gcc dot gnu.org> ---
This is also a missed SRA optimization.  SRA produces

  b$i_16 =3D b.i;
  b$j_17 =3D b.j;
  b.i =3D b$i_16;
  b.j =3D b$j_17;
  _1 =3D VIEW_CONVERT_EXPR<unsigned char>(b);
  _2 =3D _1 & 1;
...
  b.i =3D b$i_16;
  b.j =3D b$j_15;
  _4 =3D VIEW_CONVERT_EXPR<unsigned char>(b);
  _5 =3D _4 & 2;

which is sub-optimal - for some reason it chooses to create replacements
for i and j instead of a unsigned char replacement for the whole
aggregate driven by the V_C_E access

access { base =3D (2771)'b', offset =3D 0, size =3D 8, expr =3D b, type =3D=
 struct B,
reverse =3D 0, grp_read =3D 1, grp_write =3D 0, grp_assignment_read =3D 1,
grp_assignment_write =3D 0, grp_scalar_read =3D 0, grp_scalar_write =3D 0,
grp_total_scalarization =3D 0, grp_hint =3D 0, grp_covered =3D 0,
grp_unscalarizable_region =3D 0, grp_unscalarized_data =3D 1, grp_same_acce=
ss_path
=3D 1, grp_partial_lhs =3D 0, grp_to_be_replaced =3D 0, grp_to_be_debug_rep=
laced =3D 0}

is also odd because the access type is really 'unsigned char'?  That seems
to be because

  /* We need to dive through V_C_Es in order to get the size of its paramet=
er
     and not the result type.  Ada produces such statements.  We are also
     capable of handling the topmost V_C_E but not any of those buried in o=
ther
     handled components.  */
  if (TREE_CODE (expr) =3D=3D VIEW_CONVERT_EXPR)
    expr =3D TREE_OPERAND (expr, 0);

but I couldn't easily convince it to do sth here (and dumps turn out
empty as for reasoning of disqualification).=