[Bug c++/81607] Conditional operator: "type mismatch in shift expression" error

["rguenth at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81607

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |wrong-code
             Status|ASSIGNED                    |NEW
          Component|tree-optimization           |c++
           Assignee|rguenth at gcc dot gnu.org         |unassigned at gcc dot gnu.org

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
0x000000000088d7d5 in cp_fold (x=<lshift_expr 0x7ffff69e6618>)
    at /tmp/trunk/gcc/cp/cp-gimplify.c:2251
2251                x = fold_build2_loc (loc, code, TREE_TYPE (x), op0, op1);
Value returned is $25 = (tree_node *) 0x7ffff69e6640
(gdb) p debug_generic_expr (op1)
a
$26 = void
(gdb) p debug_generic_expr (op0)
(long int) d.c
$27 = void
(gdb) p debug_generic_expr (x)
(1 ? (int) (long int) d.c : 0) << a
$28 = void

because we run into

static tree
cp_fold (tree x)
{
...
    case VEC_COND_EXPR:
    case COND_EXPR:
...
      /* A COND_EXPR might have incompatible types in branches if one or both
         arms are bitfields.  If folding exposed such a branch, fix it up.  */
      if (TREE_CODE (x) != code)
        if (tree type = is_bitfield_expr_with_lowered_type (x))
          x = fold_convert (type, x);

and fold (int) (long int) d.c to (long int) d.c here.

C++ FE bug.

Not sure why this isn't simply the following as we surely have to preserve
the type of the COND_EXPR when folding.

Index: gcc/cp/cp-gimplify.c
===================================================================
--- gcc/cp/cp-gimplify.c        (revision 250725)
+++ gcc/cp/cp-gimplify.c        (working copy)
@@ -2314,8 +2314,7 @@ cp_fold (tree x)
       /* A COND_EXPR might have incompatible types in branches if one or both
         arms are bitfields.  If folding exposed such a branch, fix it up.  */
       if (TREE_CODE (x) != code)
-       if (tree type = is_bitfield_expr_with_lowered_type (x))
-         x = fold_convert (type, x);
+       x = fold_convert (TREE_TYPE (org_x), x);

       break;


Leaving to C++ folks.