[Bug middle-end/19874] ICE in emit_move_insn with __attribute__((mode (QI))) enum

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

------- Additional Comments From jakub at gcc dot gnu dot org  2005-02-21 14:28 -------
This is a regression from GCC 3.4.x and earlier btw.

The problem seems to be that STRIP_USELESS_TYPE_CONVERSION strips
E to E __attribute__ ((mode (__byte__))) conversion as useless, although
it has different TYPE_MODE and TYPE_PRECISION.
This is because both have the same TYPE_MAIN_VARIANT.
I tried following patch which cures this for C, but unfortunately breaks
C++ at the same time (C++ needs both enums to have the same main variant):
--- gcc/c-common.c.jj   2005-02-14 09:25:46.000000000 +0100
+++ gcc/c-common.c      2005-02-21 14:43:53.000000000 +0100
@@ -4364,7 +4364,7 @@ handle_mode_attribute (tree *node, tree
            }

          if (!(flags & (int) ATTR_FLAG_TYPE_IN_PLACE))
-           type = build_variant_type_copy (type);
+           type = build_distinct_type_copy (type);

          /* We cannot use layout_type here, because that will attempt
             to re-layout all variants, corrupting our original.  */
--- gcc/c-typeck.c.jj   2005-02-19 00:31:52.000000000 +0100
+++ gcc/c-typeck.c      2005-02-21 15:07:51.249019189 +0100
@@ -755,12 +755,19 @@ comptypes (tree type1, tree type2)
       if (c_dialect_objc () && objc_comptypes (t1, t2, 0) == 1)
        val = 1;

-    case ENUMERAL_TYPE:
     case UNION_TYPE:
       if (val != 1 && !same_translation_unit_p (t1, t2))
        val = tagged_types_tu_compatible_p (t1, t2);
       break;

+    /* Don't consider enum E { A, B } and enum E __attribute__((mode (byte)))
+       to be compatible.  */
+    case ENUMERAL_TYPE:
+      if (val != 1 && TYPE_MODE (t1) == TYPE_MODE (t2)
+          && !same_translation_unit_p (t1, t2))
+        val = tagged_types_tu_compatible_p (t1, t2);
+      break;
+
     case VECTOR_TYPE:
       val = TYPE_VECTOR_SUBPARTS (t1) == TYPE_VECTOR_SUBPARTS (t2)
            && comptypes (TREE_TYPE (t1), TREE_TYPE (t2));

Alternative would be e.g. to change c_types_compatible_p to special case
ENUMERAL_TYPEs and requiring there TYPE_MODE () to be compatible.


-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |rth at gcc dot gnu dot org
   Target Milestone|---                         |4.0.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19874