Hi,
the patch below might be useful for testcase preparation and debugging
compiler bugs such as PR 60965. When
-ftrap-on-impossible-devirtualization is supplied on the command line,
it makes the devirtualization produce __builtin_trap instead of
__builtin_unreachable when it comes to the conclusion that there is no
legal target of a virtual call.
Apart from dealing with our bugs, it may be even useful to debug
compiled programs when a user triggers some sort of illegal
devirtualization, typically by missing a type check somewhere.
Currently the compiled program might simply take a wrong branch, with
the patch it will abort.
Bootstrapped and tested (with the option on) on x86_64-linux, I have
also successfully LTO built Firefox with it. If I add some
documentation, would like to see this in trunk?
Thanks,
Martin
2014-04-03 Martin Jambor <mjam...@suse.cz>
* cgraph.c (verify_edge_corresponds_to_fndecl): Also always accept
builtin_trap.
* cgraphclones.c (cgraph_clone_node): Do not redirect calls to
builtin_trap.
* cgraphunit.c (walk_polymorphic_call_targets): Use
ipa_impossible_devirt_target_node.
* common.opt (ftrap-on-impossible-devirtualization): New option.
* gimple-fold.c (fold_gimple_assign): Use
ipa_impossible_devirt_target_decl.
(gimple_fold_call): Likewise.
(gimple_get_virt_method_for_vtable): Likewise.
* ipa-cp.c (ipa_get_indirect_edge_target_1): Check also for
builtin_trap, use ipa_impossible_devirt_target_decl.
* ipa-devirt.c (ipa_impossible_devirt_target_decl): New function.
(ipa_impossible_devirt_target_node): Likewise.
* ipa-prop.c (ipa_make_edge_direct_to_target): Use
ipa_impossible_devirt_target_decl.
(try_make_edge_direct_virtual_call): Check also for builtin_trap, use
ipa_impossible_devirt_target_decl.
* ipa-utils.h (ipa_impossible_devirt_target_decl): Declare.
(ipa_impossible_devirt_target_node): Likewise.
* ipa.c (walk_polymorphic_call_targets): Use
ipa_impossible_devirt_target_node.
diff --git a/gcc/cgraph.c b/gcc/cgraph.c
index be3661a..25e0775 100644
--- a/gcc/cgraph.c
+++ b/gcc/cgraph.c
@@ -2664,9 +2664,10 @@ verify_edge_corresponds_to_fndecl (struct cgraph_edge
*e, tree decl)
return false;
/* Optimizers can redirect unreachable calls or calls triggering undefined
- behaviour to builtin_unreachable. */
+ behaviour to builtin_unreachable or builtin_trap. */
if (DECL_BUILT_IN_CLASS (e->callee->decl) == BUILT_IN_NORMAL
- && DECL_FUNCTION_CODE (e->callee->decl) == BUILT_IN_UNREACHABLE)
+ && (DECL_FUNCTION_CODE (e->callee->decl) == BUILT_IN_UNREACHABLE
+ || DECL_FUNCTION_CODE (e->callee->decl) == BUILT_IN_TRAP))
return false;
node = cgraph_function_or_thunk_node (node, NULL);
diff --git a/gcc/cgraphclones.c b/gcc/cgraphclones.c
index cd2d73d..e7bebe3 100644
--- a/gcc/cgraphclones.c
+++ b/gcc/cgraphclones.c
@@ -449,8 +449,9 @@ cgraph_clone_node (struct cgraph_node *n, tree decl,
gcov_type count, int freq,
be unreachable during the clonning procedure. */
if (!e->callee
|| DECL_BUILT_IN_CLASS (e->callee->decl) != BUILT_IN_NORMAL
- || DECL_FUNCTION_CODE (e->callee->decl) != BUILT_IN_UNREACHABLE)
- redirect_edge_duplicating_thunks (e, new_node, args_to_skip);
+ || (DECL_FUNCTION_CODE (e->callee->decl) != BUILT_IN_UNREACHABLE
+ && DECL_FUNCTION_CODE (e->callee->decl) != BUILT_IN_TRAP))
+ cgraph_redirect_edge_callee (e, new_node);
}
diff --git a/gcc/cgraphunit.c b/gcc/cgraphunit.c
index 06283fc..6c56c90 100644
--- a/gcc/cgraphunit.c
+++ b/gcc/cgraphunit.c
@@ -892,8 +892,7 @@ walk_polymorphic_call_targets (pointer_set_t
*reachable_call_targets,
if (targets.length () == 1)
target = targets[0];
else
- target = cgraph_get_create_node
- (builtin_decl_implicit (BUILT_IN_UNREACHABLE));
+ target = ipa_impossible_devirt_target_node ();
if (cgraph_dump_file)
{
diff --git a/gcc/common.opt b/gcc/common.opt
index da275e5..3e8b359 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -1019,6 +1019,10 @@ fdevirtualize
Common Report Var(flag_devirtualize) Optimization
Try to convert virtual calls to direct ones.
+ftrap-on-impossible-devirtualization
+Common Report Var(flag_trap_impossible_devirt)
+Convert virtual calls that cannot have any target to builtin_trap.
+
fdiagnostics-show-location=
Common Joined RejectNegative Enum(diagnostic_prefixing_rule)
-fdiagnostics-show-location=[once|every-line] How often to emit source
location at the beginning of line-wrapped diagnostics
diff --git a/gcc/gimple-fold.c b/gcc/gimple-fold.c
index 6402cce..e0dfcb9 100644
--- a/gcc/gimple-fold.c
+++ b/gcc/gimple-fold.c
@@ -392,7 +392,7 @@ fold_gimple_assign (gimple_stmt_iterator *si)
if (targets.length () == 1)
fndecl = targets[0]->decl;
else
- fndecl = builtin_decl_implicit (BUILT_IN_UNREACHABLE);
+ fndecl = ipa_impossible_devirt_target_decl ();
val = fold_convert (TREE_TYPE (val), fndecl);
STRIP_USELESS_TYPE_CONVERSION (val);
return val;
@@ -1146,7 +1146,7 @@ gimple_fold_call (gimple_stmt_iterator *gsi, bool inplace)
}
else
{
- tree fndecl = builtin_decl_implicit (BUILT_IN_UNREACHABLE);
+ tree fndecl = ipa_impossible_devirt_target_decl ();
gimple new_stmt = gimple_build_call (fndecl, 0);
gimple_set_location (new_stmt, gimple_location (stmt));
if (lhs && TREE_CODE (lhs) == SSA_NAME)
@@ -3332,7 +3332,7 @@ gimple_get_virt_method_for_vtable (HOST_WIDE_INT token,
if (!fn
|| (TREE_CODE (fn) != ADDR_EXPR && TREE_CODE (fn) != FDESC_EXPR)
|| TREE_CODE (TREE_OPERAND (fn, 0)) != FUNCTION_DECL)
- fn = builtin_decl_implicit (BUILT_IN_UNREACHABLE);
+ fn = ipa_impossible_devirt_target_decl ();
else
{
fn = TREE_OPERAND (fn, 0);
diff --git a/gcc/ipa-cp.c b/gcc/ipa-cp.c
index 479963c..124f31d 100644
--- a/gcc/ipa-cp.c
+++ b/gcc/ipa-cp.c
@@ -1584,7 +1584,8 @@ ipa_get_indirect_edge_target_1 (struct cgraph_edge *ie,
if (target)
{
if ((TREE_CODE (TREE_TYPE (target)) == FUNCTION_TYPE
- && DECL_FUNCTION_CODE (target) == BUILT_IN_UNREACHABLE)
+ && (DECL_FUNCTION_CODE (target) == BUILT_IN_UNREACHABLE
+ || DECL_FUNCTION_CODE (target) == BUILT_IN_TRAP))
|| !possible_polymorphic_call_target_p
(ie, cgraph_get_node (target)))
{
@@ -1593,7 +1594,7 @@ ipa_get_indirect_edge_target_1 (struct cgraph_edge *ie,
"Type inconsident devirtualization: %s/%i->%s\n",
ie->caller->name (), ie->caller->order,
IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (target)));
- target = builtin_decl_implicit (BUILT_IN_UNREACHABLE);
+ target = ipa_impossible_devirt_target_decl ();
cgraph_get_create_node (target);
}
return target;
@@ -1629,7 +1630,7 @@ ipa_get_indirect_edge_target_1 (struct cgraph_edge *ie,
if (targets.length () == 1)
target = targets[0]->decl;
else
- target = builtin_decl_implicit (BUILT_IN_UNREACHABLE);
+ target = ipa_impossible_devirt_target_decl ();
}
else
{
@@ -1649,7 +1650,7 @@ ipa_get_indirect_edge_target_1 (struct cgraph_edge *ie,
"Type inconsident devirtualization: %s/%i->%s\n",
ie->caller->name (), ie->caller->order,
IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (target)));
- target = builtin_decl_implicit (BUILT_IN_UNREACHABLE);
+ target = ipa_impossible_devirt_target_decl ();
cgraph_get_create_node (target);
}
diff --git a/gcc/ipa-devirt.c b/gcc/ipa-devirt.c
index d484b20..600836d 100644
--- a/gcc/ipa-devirt.c
+++ b/gcc/ipa-devirt.c
@@ -2148,4 +2148,26 @@ make_pass_ipa_devirt (gcc::context *ctxt)
return new pass_ipa_devirt (ctxt);
}
+/* Return function declaration that we want to generate call to when
+ encountering a a virtual call which cannot have any valid target. */
+
+tree
+ipa_impossible_devirt_target_decl (void)
+{
+ if (flag_trap_impossible_devirt)
+ return builtin_decl_implicit (BUILT_IN_TRAP);
+ else
+ return builtin_decl_implicit (BUILT_IN_UNREACHABLE);
+}
+
+/* Return call graph node of a function that we want to generate call to when
+ encountering a a virtual call which cannot have any valid target. */
+
+cgraph_node *
+ipa_impossible_devirt_target_node (void)
+{
+ return cgraph_get_create_node (ipa_impossible_devirt_target_decl ());
+}
+
+
#include "gt-ipa-devirt.h"
diff --git a/gcc/ipa-prop.c b/gcc/ipa-prop.c
index 9f144fa..42623f4 100644
--- a/gcc/ipa-prop.c
+++ b/gcc/ipa-prop.c
@@ -2494,7 +2494,7 @@ ipa_make_edge_direct_to_target (struct cgraph_edge *ie,
tree target)
fprintf (dump_file, "ipa-prop: Discovered direct call to
non-function"
" in %s/%i, making it unreachable.\n",
ie->caller->name (), ie->caller->order);
- target = builtin_decl_implicit (BUILT_IN_UNREACHABLE);
+ target = ipa_impossible_devirt_target_decl ();
callee = cgraph_get_create_node (target);
unreachable = true;
}
@@ -2732,7 +2732,8 @@ try_make_edge_direct_virtual_call (struct cgraph_edge *ie,
if (target)
{
if ((TREE_CODE (TREE_TYPE (target)) == FUNCTION_TYPE
- && DECL_FUNCTION_CODE (target) == BUILT_IN_UNREACHABLE)
+ && (DECL_FUNCTION_CODE (target) == BUILT_IN_UNREACHABLE
+ || DECL_FUNCTION_CODE (target) == BUILT_IN_TRAP))
|| !possible_polymorphic_call_target_p
(ie, cgraph_get_node (target)))
{
@@ -2741,7 +2742,7 @@ try_make_edge_direct_virtual_call (struct cgraph_edge *ie,
"Type inconsident devirtualization: %s/%i->%s\n",
ie->caller->name (), ie->caller->order,
IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (target)));
- target = builtin_decl_implicit (BUILT_IN_UNREACHABLE);
+ target = ipa_impossible_devirt_target_decl ();
cgraph_get_create_node (target);
}
return ipa_make_edge_direct_to_target (ie, target);
@@ -2774,7 +2775,7 @@ try_make_edge_direct_virtual_call (struct cgraph_edge *ie,
target = targets[0]->decl;
else
{
- target = builtin_decl_implicit (BUILT_IN_UNREACHABLE);
+ target = ipa_impossible_devirt_target_decl ();
cgraph_get_create_node (target);
}
}
diff --git a/gcc/ipa-utils.h b/gcc/ipa-utils.h
index a2c985a..81c7983 100644
--- a/gcc/ipa-utils.h
+++ b/gcc/ipa-utils.h
@@ -186,6 +186,10 @@ possible_polymorphic_call_target_p (tree call,
ipa_dummy_polymorphic_call_context,
n);
}
+
+tree ipa_impossible_devirt_target_decl (void);
+cgraph_node *ipa_impossible_devirt_target_node (void);
+
#endif /* GCC_IPA_UTILS_H */
diff --git a/gcc/ipa.c b/gcc/ipa.c
index 8b65abd..e8fd04d 100644
--- a/gcc/ipa.c
+++ b/gcc/ipa.c
@@ -219,8 +219,7 @@ walk_polymorphic_call_targets (pointer_set_t
*reachable_call_targets,
if (targets.length () == 1)
target = targets[0];
else
- target = cgraph_get_create_node
- (builtin_decl_implicit (BUILT_IN_UNREACHABLE));
+ target = ipa_impossible_devirt_target_node ();
if (dump_file)
fprintf (dump_file,
