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Re: Fix ipa-devirt WRT type variants


On Sat, Jun 28, 2014 at 8:26 PM, Jan Hubicka <hubicka@ucw.cz> wrote:
> Hi,
> this is another bug noticed.  Here ipa-devirt attempts to merge binfos of two representations
> of the same ODR type, but forgets about variants.
>
> I also noticed that using variant instead of the type may end up in incomplete type and/or
> we may waste polymorphic call target cache by duplicated entries.  I made the contextes to
> be always main variants thus.
>
> Bootstrapped, lto-bootstrapped/regtested x86_64-linux, comitted.
>
>         * ipa-devirt.c (set_type_binfo): New function.
>         (add_type_duplicate): Use it.
>         (get_odr_type): Sanity check that binfos points to main variants.
>         (get_class_context): Be sure the context's outer_type is main variant.
>         (contains_type_p): Walk main variant.
>         (get_polymorphic_call_info_for_decl): Set outer_type to be main variant.
>         (get_polymorphic_call_info): Likewise.
>         (possible_polymorphic_call_targets): Sanity check that we operate on main
>         variant.
> Index: ipa-devirt.c
> ===================================================================
> --- ipa-devirt.c        (revision 212098)
> +++ ipa-devirt.c        (working copy)
> @@ -334,6 +334,17 @@ static odr_hash_type *odr_hash;
>  static GTY(()) vec <odr_type, va_gc> *odr_types_ptr;
>  #define odr_types (*odr_types_ptr)
>
> +/* Set TYPE_BINFO of TYPE and its variants to BINFO.  */
> +void
> +set_type_binfo (tree type, tree binfo)
> +{
> +  for (; type; type = TYPE_NEXT_VARIANT (type))
> +    if (COMPLETE_TYPE_P (type))
> +      TYPE_BINFO (type) = binfo;
> +    else
> +      gcc_assert (!TYPE_BINFO (type));
> +}

Btw - this points to the "obvious" opportunity to make variant types
a lot smaller (with the caveat to require an indirection to the main
variant to access shared bits).  That would also automagically
help LTO streaming ....

Richard.

>  /* TYPE is equivalent to VAL by ODR, but its tree representation differs
>     from VAL->type.  This may happen in LTO where tree merging did not merge
>     all variants of the same type.  It may or may not mean the ODR violation.
> @@ -446,16 +457,17 @@ add_type_duplicate (odr_type val, tree t
>             {
>               unsigned int i;
>
> -             TYPE_BINFO (val->type) = TYPE_BINFO (type);
> +             set_type_binfo (val->type, TYPE_BINFO (type));
>               for (i = 0; i < val->types->length (); i++)
>                 {
>                   if (TYPE_BINFO ((*val->types)[i])
>                       == master_binfo)
> -                   TYPE_BINFO ((*val->types)[i]) = TYPE_BINFO (type);
> +                   set_type_binfo ((*val->types)[i], TYPE_BINFO (type));
>                 }
> +             BINFO_TYPE (TYPE_BINFO (type)) = val->type;
>             }
>           else
> -           TYPE_BINFO (type) = master_binfo;
> +           set_type_binfo (type, master_binfo);
>         }
>      }
>  }
> @@ -495,6 +507,7 @@ get_odr_type (tree type, bool insert)
>
>        val = ggc_cleared_alloc<odr_type_d> ();
>        val->type = type;
> +      gcc_assert (BINFO_TYPE (TYPE_BINFO (val->type)) = type);
>        val->bases = vNULL;
>        val->derived_types = vNULL;
>        val->anonymous_namespace = type_in_anonymous_namespace_p (type);
> @@ -1102,7 +1115,7 @@ get_class_context (ipa_polymorphic_call_
>           if (!fld)
>             goto give_up;
>
> -         type = TREE_TYPE (fld);
> +         type = TYPE_MAIN_VARIANT (TREE_TYPE (fld));
>           offset -= pos;
>           /* DECL_ARTIFICIAL represents a basetype.  */
>           if (!DECL_ARTIFICIAL (fld))
> @@ -1116,7 +1129,7 @@ get_class_context (ipa_polymorphic_call_
>         }
>        else if (TREE_CODE (type) == ARRAY_TYPE)
>         {
> -         tree subtype = TREE_TYPE (type);
> +         tree subtype = TYPE_MAIN_VARIANT (TREE_TYPE (type));
>
>           /* Give up if we don't know array size.  */
>           if (!tree_fits_shwi_p (TYPE_SIZE (subtype))
> @@ -1159,7 +1172,8 @@ static bool
>  contains_type_p (tree outer_type, HOST_WIDE_INT offset,
>                  tree otr_type)
>  {
> -  ipa_polymorphic_call_context context = {offset, outer_type,
> +  ipa_polymorphic_call_context context = {offset,
> +                                         TYPE_MAIN_VARIANT (outer_type),
>                                           false, true};
>    return get_class_context (&context, otr_type);
>  }
> @@ -1272,7 +1286,7 @@ get_polymorphic_call_info_for_decl (ipa_
>  {
>    gcc_assert (DECL_P (base));
>
> -  context->outer_type = TREE_TYPE (base);
> +  context->outer_type = TYPE_MAIN_VARIANT (TREE_TYPE (base));
>    context->offset = offset;
>    /* Make very conservative assumption that all objects
>       may be in construction.
> @@ -1329,7 +1343,7 @@ get_polymorphic_call_info (tree fndecl,
>    *otr_token = tree_to_uhwi (OBJ_TYPE_REF_TOKEN (ref));
>
>    /* Set up basic info in case we find nothing interesting in the analysis.  */
> -  context->outer_type = *otr_type;
> +  context->outer_type = TYPE_MAIN_VARIANT (*otr_type);
>    context->offset = 0;
>    base_pointer = OBJ_TYPE_REF_OBJECT (ref);
>    context->maybe_derived_type = true;
> @@ -1415,7 +1429,8 @@ get_polymorphic_call_info (tree fndecl,
>        if (TREE_CODE (TREE_TYPE (fndecl)) == METHOD_TYPE
>           && SSA_NAME_VAR (base_pointer) == DECL_ARGUMENTS (fndecl))
>         {
> -         context->outer_type = TREE_TYPE (TREE_TYPE (base_pointer));
> +         context->outer_type
> +            = TYPE_MAIN_VARIANT (TREE_TYPE (TREE_TYPE (base_pointer)));
>           gcc_assert (TREE_CODE (context->outer_type) == RECORD_TYPE);
>
>           /* Dynamic casting has possibly upcasted the type
> @@ -1450,7 +1465,8 @@ get_polymorphic_call_info (tree fndecl,
>          object.  */
>        if (DECL_BY_REFERENCE (SSA_NAME_VAR (base_pointer)))
>         {
> -         context->outer_type = TREE_TYPE (TREE_TYPE (base_pointer));
> +         context->outer_type
> +            = TYPE_MAIN_VARIANT (TREE_TYPE (TREE_TYPE (base_pointer)));
>           gcc_assert (!POINTER_TYPE_P (context->outer_type));
>           /* Only type inconsistent programs can have otr_type that is
>              not part of outer type.  */
> @@ -1599,6 +1615,8 @@ possible_polymorphic_call_targets (tree
>    bool can_refer;
>    bool skipped = false;
>
> +  otr_type = TYPE_MAIN_VARIANT (otr_type);
> +
>    /* If ODR is not initialized, return empty incomplete list.  */
>    if (!odr_hash)
>      {
> @@ -1625,6 +1643,10 @@ possible_polymorphic_call_targets (tree
>
>    type = get_odr_type (otr_type, true);
>
> +  /* Recording type variants would wast results cache.  */
> +  gcc_assert (!context.outer_type
> +             || TYPE_MAIN_VARIANT (context.outer_type) == context.outer_type);
> +
>    /* Lookup the outer class type we want to walk.  */
>    if (context.outer_type
>        && !get_class_context (&context, otr_type))
> @@ -1638,6 +1660,10 @@ possible_polymorphic_call_targets (tree
>        return nodes;
>      }
>
> +  /* Check that get_class_context kept the main variant.  */
> +  gcc_assert (!context.outer_type
> +             || TYPE_MAIN_VARIANT (context.outer_type) == context.outer_type);
> +
>    /* We canonicalize our query, so we do not need extra hashtable entries.  */
>
>    /* Without outer type, we have no use for offset.  Just do the


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