On Fri, Apr 25, 2014 at 5:35 PM, Martin Jambor <mjam...@suse.cz> wrote: > 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?
It's useful for debugging, so yes. Not sure about the option name though. Maybe we should have a generic -ftrap-on-unreachable flag instead and handle all __builtin_unreachable () like that (for example by folding or by simply make __builtin_unreachable () alias to __builtin_trap ()). Richard. > 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,