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ipa-devirt.c (referenced_from_vtable_p): New predicate.

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* ipa-devirt.c (referenced_from_vtable_p): New predicate.
	(maybe_record_node, likely_target_p): Use it.

From-SVN: r209435
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Jan Hubicka 2014-04-15 23:01:04 +02:00 committed by Jan Hubicka
parent 33fbb3584a
commit ccb05ef2c3
2 changed files with 76 additions and 5 deletions
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gcc/ChangeLog
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@ -1,3 +1,8 @@
2014-04-15 Jan Hubicka <jh@suse.cz>
* ipa-devirt.c (referenced_from_vtable_p): New predicate.
(maybe_record_node, likely_target_p): Use it.
2014-04-15 Bill Schmidt <wschmidt@linux.vnet.ibm.com>
PR target/60839

76
gcc/ipa-devirt.c
View File

@ -598,6 +598,48 @@ build_type_inheritance_graph (void)
timevar_pop (TV_IPA_INHERITANCE);
}
/* Return true if N has reference from live virtual table
(and thus can be a destination of polymorphic call).
Be conservatively correct when callgraph is not built or
if the method may be referred externally. */
static bool
referenced_from_vtable_p (struct cgraph_node *node)
{
int i;
struct ipa_ref *ref;
bool found = false;
if (node->externally_visible
|| node->used_from_other_partition)
return true;
/* Keep this test constant time.
It is unlikely this can happen except for the case where speculative
devirtualization introduced many speculative edges to this node.
In this case the target is very likely alive anyway. */
if (node->ref_list.referring.length () > 100)
return true;
/* We need references built. */
if (cgraph_state <= CGRAPH_STATE_CONSTRUCTION)
return true;
for (i = 0; ipa_ref_list_referring_iterate (&node->ref_list,
i, ref); i++)
if ((ref->use == IPA_REF_ALIAS
&& referenced_from_vtable_p (cgraph (ref->referring)))
|| (ref->use == IPA_REF_ADDR
&& TREE_CODE (ref->referring->decl) == VAR_DECL
&& DECL_VIRTUAL_P (ref->referring->decl)))
{
found = true;
break;
}
return found;
}
/* If TARGET has associated node, record it in the NODES array.
CAN_REFER specify if program can refer to the target directly.
if TARGET is unknown (NULL) or it can not be inserted (for example because
@ -634,11 +676,29 @@ maybe_record_node (vec <cgraph_node *> &nodes,
target_node = cgraph_get_node (target);
if (target_node != NULL
&& ((TREE_PUBLIC (target)
|| DECL_EXTERNAL (target))
|| target_node->definition)
&& symtab_real_symbol_p (target_node))
/* Method can only be called by polymorphic call if any
of vtables refering to it are alive.
While this holds for non-anonymous functions, too, there are
cases where we want to keep them in the list; for example
inline functions with -fno-weak are static, but we still
may devirtualize them when instance comes from other unit.
The same holds for LTO.
Currently we ignore these functions in speculative devirtualization.
??? Maybe it would make sense to be more aggressive for LTO even
eslewhere. */
if (!flag_ltrans
&& type_in_anonymous_namespace_p (DECL_CONTEXT (target))
&& (!target_node
|| !referenced_from_vtable_p (target_node)))
;
/* See if TARGET is useful function we can deal with. */
else if (target_node != NULL
&& (TREE_PUBLIC (target)
|| DECL_EXTERNAL (target)
|| target_node->definition)
&& symtab_real_symbol_p (target_node))
{
gcc_assert (!target_node->global.inlined_to);
gcc_assert (symtab_real_symbol_p (target_node));
@ -1725,6 +1785,12 @@ likely_target_p (struct cgraph_node *n)
return false;
if (n->frequency < NODE_FREQUENCY_NORMAL)
return false;
/* If there are no virtual tables refering the target alive,
the only way the target can be called is an instance comming from other
compilation unit; speculative devirtualization is build around an
assumption that won't happen. */
if (!referenced_from_vtable_p (n))
return false;
return true;
}