%-----------------------------------------------------------------------------% % Copyright (C) 1996-2003 The University of Melbourne. % This file may only be copied under the terms of the GNU General % Public License - see the file COPYING in the Mercury distribution. %-----------------------------------------------------------------------------% % % File: modecheck_unify.m. % Main author: fjh. % % This module contains the code to modecheck a unification. % % Check that the unification doesn't attempt to unify two free variables % (or in general two free sub-terms) unless one of them is dead. (Also we % ought to split unifications up if necessary to avoid complicated % sub-unifications.) % %-----------------------------------------------------------------------------% %-----------------------------------------------------------------------------% :- module check_hlds__modecheck_unify. :- interface. :- import_module check_hlds__mode_info. :- import_module hlds__hlds_goal. :- import_module parse_tree__prog_data. :- import_module io. % Modecheck a unification :- pred modecheck_unification(prog_var::in, unify_rhs::in, unification::in, unify_context::in, hlds_goal_info::in, hlds_goal_expr::out, mode_info::in, mode_info::out, io::di, io::uo) is det. % Create a unification between the two given variables. % The goal's mode and determinism information is not filled in. :- pred modecheck_unify__create_var_var_unification(prog_var::in, prog_var::in, (type)::in, mode_info::in, hlds_goal::out) is det. %-----------------------------------------------------------------------------% %-----------------------------------------------------------------------------% :- implementation. :- import_module check_hlds__inst_match. :- import_module check_hlds__inst_util. :- import_module check_hlds__mode_debug. :- import_module check_hlds__mode_errors. :- import_module check_hlds__mode_info. :- import_module check_hlds__mode_util. :- import_module check_hlds__modecheck_call. :- import_module check_hlds__modes. :- import_module check_hlds__polymorphism. :- import_module check_hlds__type_util. :- import_module check_hlds__typecheck. :- import_module check_hlds__unify_proc. :- import_module check_hlds__unique_modes. :- import_module hlds__hlds_data. :- import_module hlds__hlds_goal. :- import_module hlds__hlds_module. :- import_module hlds__hlds_out. :- import_module hlds__hlds_pred. :- import_module hlds__instmap. :- import_module hlds__make_hlds. :- import_module hlds__quantification. :- import_module parse_tree__inst. :- import_module parse_tree__module_qual. :- import_module parse_tree__prog_util. :- import_module bool, list, map, std_util, int, set, require. :- import_module string, assoc_list. :- import_module term, varset. %-----------------------------------------------------------------------------% modecheck_unification(X, var(Y), Unification0, UnifyContext, _GoalInfo, Unify, !ModeInfo, !IO) :- mode_info_get_module_info(!.ModeInfo, ModuleInfo0), mode_info_get_instmap(!.ModeInfo, InstMap0), instmap__lookup_var(InstMap0, X, InstOfX), instmap__lookup_var(InstMap0, Y, InstOfY), mode_info_var_is_live(!.ModeInfo, X, LiveX), mode_info_var_is_live(!.ModeInfo, Y, LiveY), ( ( LiveX = live, LiveY = live -> BothLive = live ; BothLive = dead ), abstractly_unify_inst(BothLive, InstOfX, InstOfY, real_unify, ModuleInfo0, UnifyInst, Det1, ModuleInfo1), % Don't allow free-free unifications if both variables are % locked. (Normally the checks for binding locked variables % are done in modecheck_set_var_inst, which is called below, % but that won't catch this case, because the inst of the % variable will remain `free'. XXX are there other cases % like this one?) \+ ( UnifyInst = free, mode_info_var_is_locked(!.ModeInfo, X, _XLockedReason), mode_info_var_is_locked(!.ModeInfo, Y, _YLockedReason), % a unification of the form `X = X' doesn't bind X, % and thus should be allowed even if X is locked X \= Y ) -> Inst = UnifyInst, Det = Det1, mode_info_set_module_info(ModuleInfo1, !ModeInfo), modecheck_set_var_inst(X, Inst, yes(InstOfY), !ModeInfo), modecheck_set_var_inst(Y, Inst, yes(InstOfX), !ModeInfo), ModeOfX = (InstOfX -> Inst), ModeOfY = (InstOfY -> Inst), mode_info_get_var_types(!.ModeInfo, VarTypes), categorize_unify_var_var(ModeOfX, ModeOfY, LiveX, LiveY, X, Y, Det, UnifyContext, VarTypes, Unification0, Unify, !ModeInfo) ; set__list_to_set([X, Y], WaitingVars), mode_info_error(WaitingVars, mode_error_unify_var_var(X, Y, InstOfX, InstOfY), !ModeInfo), % If we get an error, set the inst to not_reached % to suppress follow-on errors % But don't call categorize_unification, because % that could cause an invalid call to % `unify_proc__request_unify' Inst = not_reached, modecheck_set_var_inst(X, Inst, no, !ModeInfo), modecheck_set_var_inst(Y, Inst, no, !ModeInfo), % return any old garbage Unification = assign(X, Y), ModeOfX = (InstOfX -> Inst), ModeOfY = (InstOfY -> Inst), Modes = ModeOfX - ModeOfY, Unify = unify(X, var(Y), Modes, Unification, UnifyContext) ). modecheck_unification(X0, functor(ConsId0, IsExistConstruction, ArgVars0), Unification0, UnifyContext, GoalInfo0, Goal, !ModeInfo, !IO) :- mode_info_get_module_info(!.ModeInfo, ModuleInfo0), mode_info_get_var_types(!.ModeInfo, VarTypes0), map__lookup(VarTypes0, X0, TypeOfX), % % We replace any unifications with higher-order pred constants % by lambda expressions. For example, we replace % % X = list__append(Y) % Y::in, X::out % % with % % X = lambda [A1::in, A2::out] (list__append(Y, A1, A2)) % % Normally this is done by polymorphism__process_unify_functor, % but if we're re-modechecking goals after lambda.m has been run % (e.g. for deforestation), then we may need to do it again here. % Note that any changes to this code here will probably need to be % duplicated there too. % ( % check if variable has a higher-order type type_is_higher_order(TypeOfX, Purity, _, EvalMethod, PredArgTypes), ConsId0 = pred_const(PredId, ProcId, _) -> % % convert the pred term to a lambda expression % mode_info_get_varset(!.ModeInfo, VarSet0), mode_info_get_context(!.ModeInfo, Context), convert_pred_to_lambda_goal(Purity, EvalMethod, X0, PredId, ProcId, ArgVars0, PredArgTypes, UnifyContext, GoalInfo0, Context, ModuleInfo0, Functor0, VarSet0, VarSet, VarTypes0, VarTypes), mode_info_set_varset(VarSet, !ModeInfo), mode_info_set_var_types(VarTypes, !ModeInfo), % % modecheck this unification in its new form % modecheck_unification(X0, Functor0, Unification0, UnifyContext, GoalInfo0, Goal, !ModeInfo, !IO) ; % % It's not a higher-order pred unification - just % call modecheck_unify_functor to do the ordinary thing. % modecheck_unify_functor(X0, TypeOfX, ConsId0, IsExistConstruction, ArgVars0, Unification0, UnifyContext, GoalInfo0, Goal, !ModeInfo, !IO) ). modecheck_unification(X, lambda_goal(Purity, PredOrFunc, EvalMethod, _, ArgVars, Vars, Modes0, Det, Goal0), Unification0, UnifyContext, _GoalInfo, unify(X, RHS, Mode, Unification, UnifyContext), !ModeInfo, !IO) :- % % First modecheck the lambda goal itself: % % initialize the initial insts of the lambda variables, % check that the non-local vars are ground (XXX or any), % mark the non-local vars as shared, % lock the non-local vars, % mark the non-clobbered lambda variables as live, % modecheck the goal, % check that the final insts are correct, % unmark the live vars, % unlock the non-local vars, % restore the original instmap. % % XXX or should we merge the original and the final instmaps??? % % The reason that we need to merge the original and final instmaps % is as follows. The lambda goal will not have bound any variables % (since they were locked), but it may have added some information % or lost some uniqueness. We cannot use the final instmap, % because that may have too much information. If we use the % initial instmap, variables will be considered as unique % even if they become shared or clobbered in the lambda goal! % % However even this may not be enough. If a unique non-local % variable is used in its unique inst (e.g. it's used in a ui % mode) and then shared within the lambda body, this is unsound. % This variable should be marked as shared at the _top_ of the % lambda goal. As for implementing this, it probably means that % the lambda goal should be re-modechecked, or even modechecked % to a fixpoint. % % For the moment, since doing all that properly seems too hard, % we just share all non-local variables at the top of the lambda goal. % This is safe, but perhaps too conservative. % mode_info_get_module_info(!.ModeInfo, ModuleInfo0), mode_info_get_how_to_check(!.ModeInfo, HowToCheckGoal), ( HowToCheckGoal = check_modes -> % This only needs to be done once. mode_info_get_types_of_vars(!.ModeInfo, Vars, VarTypes), propagate_types_into_mode_list(VarTypes, ModuleInfo0, Modes0, Modes) ; Modes = Modes0 ), % initialize the initial insts of the lambda variables mode_list_get_initial_insts(Modes, ModuleInfo0, VarInitialInsts), assoc_list__from_corresponding_lists(Vars, VarInitialInsts, VarInstAL), instmap_delta_from_assoc_list(VarInstAL, VarInstMapDelta), mode_info_get_instmap(!.ModeInfo, InstMap0), instmap__apply_instmap_delta(InstMap0, VarInstMapDelta, InstMap1), mode_info_set_instmap(InstMap1, !ModeInfo), % mark the non-clobbered lambda variables as live get_arg_lives(Modes, ModuleInfo0, ArgLives), get_live_vars(Vars, ArgLives, LiveVarsList), set__list_to_set(LiveVarsList, LiveVars), mode_info_add_live_vars(LiveVars, !ModeInfo), % lock the non-locals % (a lambda goal is not allowed to bind any of the non-local % variables, since it could get called more than once, or % from inside a negation) Goal0 = _ - GoalInfo0, goal_info_get_nonlocals(GoalInfo0, NonLocals0), set__delete_list(NonLocals0, Vars, NonLocals), set__to_sorted_list(NonLocals, NonLocalsList), instmap__lookup_vars(NonLocalsList, InstMap1, NonLocalInsts), mode_info_get_module_info(!.ModeInfo, ModuleInfo2), ( % XXX This test is too conservative. % % We should allow non-local variables to be non-ground % sometimes, possibly dependent on whether or not they % are dead after this unification. In addition, we % should not "share" a unique non-local variable if % these two conditions hold: % % - It is dead after this unification. % - It is not shared within the lambda body. % % Unfortunately, we can't test the latter condition % until after we've mode-checked the lambda body. % (See the above comment on merging the initial and % final instmaps.) % XXX This test is also not conservative enough! % % We should not allow non-local vars to have inst `any'; % because that can lead to unsoundness. % However, disallowing that idiom would break % extras/trailed_update/samples/vqueens.m, and % would make freeze/3 basically useless... % so for now at least, let's not disallow it, % even though it is unsafe. inst_list_is_ground_or_any(NonLocalInsts, ModuleInfo2) -> make_shared_inst_list(NonLocalInsts, ModuleInfo2, SharedNonLocalInsts, ModuleInfo3), instmap__set_vars(InstMap1, NonLocalsList, SharedNonLocalInsts, InstMap2), mode_info_set_module_info(ModuleInfo3, !ModeInfo), mode_info_set_instmap(InstMap2, !ModeInfo), mode_info_lock_vars(lambda(PredOrFunc), NonLocals, !ModeInfo), mode_checkpoint(enter, "lambda goal", !ModeInfo, !IO), % if we're being called from unique_modes.m, then we need to % call unique_modes__check_goal rather than modecheck_goal. ( HowToCheckGoal = check_unique_modes -> unique_modes__check_goal(Goal0, Goal, !ModeInfo, !IO) ; modecheck_goal(Goal0, Goal, !ModeInfo, !IO) ), mode_list_get_final_insts(Modes, ModuleInfo0, FinalInsts), modecheck_final_insts(Vars, FinalInsts, !ModeInfo), mode_checkpoint(exit, "lambda goal", !ModeInfo, !IO), mode_info_remove_live_vars(LiveVars, !ModeInfo), mode_info_unlock_vars(lambda(PredOrFunc), NonLocals, !ModeInfo), % % Ensure that the non-local vars are shared OUTSIDE the % lambda unification as well as inside. % instmap__set_vars(InstMap0, NonLocalsList, SharedNonLocalInsts, InstMap11), mode_info_set_instmap(InstMap11, !ModeInfo), % % Now modecheck the unification of X with the lambda-expression. % RHS0 = lambda_goal(Purity, PredOrFunc, EvalMethod, modes_are_ok, ArgVars, Vars, Modes, Det, Goal), modecheck_unify_lambda(X, PredOrFunc, ArgVars, Modes, Det, RHS0, RHS, Unification0, Unification, Mode, !ModeInfo) ; list__filter((pred(Var :: in) is semidet :- instmap__lookup_var(InstMap1, Var, Inst), \+ inst_is_ground(ModuleInfo2, Inst) ), NonLocalsList, NonGroundNonLocals), ( NonGroundNonLocals = [BadVar | _] -> instmap__lookup_var(InstMap1, BadVar, BadInst), set__singleton_set(WaitingVars, BadVar), mode_info_error(WaitingVars, mode_error_non_local_lambda_var(BadVar, BadInst), !ModeInfo) ; error("modecheck_unification(lambda): very strange var") ), % return any old garbage RHS = lambda_goal(Purity, PredOrFunc, EvalMethod, modes_are_ok, ArgVars, Vars, Modes0, Det, Goal0), Mode = (free -> free) - (free -> free), Unification = Unification0 ). :- pred modecheck_unify_lambda(prog_var::in, pred_or_func::in, list(prog_var)::in, list(mode)::in, determinism::in, unify_rhs::in, unify_rhs::out, unification::in, unification::out, pair(mode)::out, mode_info::in, mode_info::out) is det. modecheck_unify_lambda(X, PredOrFunc, ArgVars, LambdaModes, LambdaDet, RHS0, RHS, Unification0, Unification, Mode, !ModeInfo) :- mode_info_get_module_info(!.ModeInfo, ModuleInfo0), mode_info_get_instmap(!.ModeInfo, InstMap0), instmap__lookup_var(InstMap0, X, InstOfX), InstOfY = ground(unique, higher_order(LambdaPredInfo)), LambdaPredInfo = pred_inst_info(PredOrFunc, LambdaModes, LambdaDet), ( abstractly_unify_inst(dead, InstOfX, InstOfY, real_unify, ModuleInfo0, UnifyInst, _Det, ModuleInfo1) -> Inst = UnifyInst, mode_info_set_module_info(ModuleInfo1, !ModeInfo), ModeOfX = (InstOfX -> Inst), ModeOfY = (InstOfY -> Inst), Mode = ModeOfX - ModeOfY, % the lambda expression just maps its argument variables % from their current insts to the same inst instmap__lookup_vars(ArgVars, InstMap0, ArgInsts), inst_lists_to_mode_list(ArgInsts, ArgInsts, ArgModes), categorize_unify_var_lambda(ModeOfX, ArgModes, X, ArgVars, PredOrFunc, RHS0, RHS, Unification0, Unification, !ModeInfo), modecheck_set_var_inst(X, Inst, no, !ModeInfo) ; set__list_to_set([X], WaitingVars), mode_info_error(WaitingVars, mode_error_unify_var_lambda(X, InstOfX, InstOfY), !ModeInfo), % If we get an error, set the inst to not_reached % to avoid cascading errors % But don't call categorize_unification, because % that could cause an invalid call to % `unify_proc__request_unify' Inst = not_reached, modecheck_set_var_inst(X, Inst, no, !ModeInfo), ModeOfX = (InstOfX -> Inst), ModeOfY = (InstOfY -> Inst), Mode = ModeOfX - ModeOfY, % return any old garbage Unification = Unification0, RHS = RHS0 ). :- pred modecheck_unify_functor(prog_var::in, (type)::in, cons_id::in, is_existential_construction::in, list(prog_var)::in, unification::in, unify_context::in, hlds_goal_info::in, hlds_goal_expr::out, mode_info::in, mode_info::out, io::di, io::uo) is det. modecheck_unify_functor(X0, TypeOfX, ConsId0, IsExistConstruction, ArgVars0, Unification0, UnifyContext, GoalInfo0, Goal, !ModeInfo, !IO) :- mode_info_get_module_info(!.ModeInfo, ModuleInfo0), mode_info_get_how_to_check(!.ModeInfo, HowToCheckGoal), % % Fully module qualify all cons_ids % (except for builtins such as ints and characters). % qualify_cons_id(TypeOfX, ArgVars0, ConsId0, ConsId, InstConsId), mode_info_get_instmap(!.ModeInfo, InstMap0), instmap__lookup_var(InstMap0, X0, InstOfX0), instmap__lookup_vars(ArgVars0, InstMap0, InstArgs), mode_info_var_list_is_live(!.ModeInfo, ArgVars0, LiveArgs), InstOfY = bound(unique, [functor(InstConsId, InstArgs)]), ( % If the unification was originally of the form % X = 'new f'(Y) it must be classified as a % construction. If it were classified as a % deconstruction, the argument unifications would % be ill-typed. IsExistConstruction = yes, \+ inst_is_free(ModuleInfo0, InstOfX0) -> % To make sure the unification is classified as % a construction, if X is already bound, we must % add a unification with an extra variable: % Z = 'new f'(Y), % X = Z. InstOfX = free, LiveX = live, make_complicated_sub_unify(X0, X, ExtraGoals0, !ModeInfo) ; InstOfX = InstOfX0, X = X0, mode_info_var_is_live(!.ModeInfo, X, LiveX), ExtraGoals0 = no_extra_goals ), ( % The occur check: X = f(X) is considered a mode error % unless X is ground. (Actually it wouldn't be that % hard to generate code for it - it always fails! - % but it's most likely to be a programming error, % so it's better to report it.) list__member(X, ArgVars0), \+ inst_is_ground(ModuleInfo0, InstOfX) -> set__list_to_set([X], WaitingVars), mode_info_error(WaitingVars, mode_error_unify_var_functor(X, InstConsId, ArgVars0, InstOfX, InstArgs), !ModeInfo), Inst = not_reached, Det = erroneous, % If we get an error, set the inst to not_reached % to avoid cascading errors % But don't call categorize_unification, because % that could cause an invalid call to % `unify_proc__request_unify' ModeOfX = (InstOfX -> Inst), ModeOfY = (InstOfY -> Inst), Mode = ModeOfX - ModeOfY, modecheck_set_var_inst(X, Inst, no, !ModeInfo), NoArgInsts = list__duplicate(length(ArgVars0), no), ( bind_args(Inst, ArgVars0, NoArgInsts, !ModeInfo) -> true ; error("bind_args failed") ), % return any old garbage Unification = Unification0, ArgVars = ArgVars0, ExtraGoals1 = no_extra_goals ; abstractly_unify_inst_functor(LiveX, InstOfX, InstConsId, InstArgs, LiveArgs, real_unify, TypeOfX, ModuleInfo0, UnifyInst, Det1, ModuleInfo1) -> Inst = UnifyInst, Det = Det1, mode_info_set_module_info(ModuleInfo1, !ModeInfo), ModeOfX = (InstOfX -> Inst), ModeOfY = (InstOfY -> Inst), Mode = ModeOfX - ModeOfY, ( get_mode_of_args(Inst, InstArgs, ModeArgs0) -> ModeArgs = ModeArgs0 ; error("get_mode_of_args failed") ), ( inst_expand_and_remove_constrained_inst_vars( ModuleInfo1, InstOfX, InstOfX1), list__length(ArgVars0, Arity), get_arg_insts(InstOfX1, InstConsId, Arity, InstOfXArgs0), get_mode_of_args(Inst, InstOfXArgs0, ModeOfXArgs0) -> ModeOfXArgs = ModeOfXArgs0, InstOfXArgs = InstOfXArgs0 ; error("get_(inst/mode)_of_args failed") ), mode_info_get_var_types(!.ModeInfo, VarTypes), categorize_unify_var_functor(ModeOfX, ModeOfXArgs, ModeArgs, X, ConsId, ArgVars0, VarTypes, UnifyContext, Unification0, Unification1, !ModeInfo), split_complicated_subunifies(Unification1, Unification, ArgVars0, ArgVars, ExtraGoals1, !ModeInfo), modecheck_set_var_inst(X, Inst, yes(InstOfY), !ModeInfo), UnifyArgInsts = list__map(func(I) = yes(I), InstOfXArgs), ( bind_args(Inst, ArgVars, UnifyArgInsts, !ModeInfo) -> true ; error("bind_args failed") ) ; set__list_to_set([X | ArgVars0], WaitingVars), % conservative mode_info_error(WaitingVars, mode_error_unify_var_functor(X, InstConsId, ArgVars0, InstOfX, InstArgs), !ModeInfo), % If we get an error, set the inst to not_reached % to avoid cascading errors % But don't call categorize_unification, because % that could cause an invalid call to % `unify_proc__request_unify' Inst = not_reached, Det = erroneous, ModeOfX = (InstOfX -> Inst), ModeOfY = (InstOfY -> Inst), Mode = ModeOfX - ModeOfY, modecheck_set_var_inst(X, Inst, no, !ModeInfo), NoArgInsts = list__duplicate(length(ArgVars0), no), ( bind_args(Inst, ArgVars0, NoArgInsts, !ModeInfo) -> true ; error("bind_args failed") ), % return any old garbage Unification = Unification0, ArgVars = ArgVars0, ExtraGoals1 = no_extra_goals ), % % Optimize away construction of unused terms by % replacing the unification with `true'. Optimize % away unifications which always fail by replacing % them with `fail'. % ( Unification = construct(_, _, _, _, _, _, _), LiveX = dead -> Goal = conj([]), !:ModeInfo = !.ModeInfo % XXX deleting this exposes % a bug in the state variable % transformation ; Det = failure -> % This optimisation is safe because the only way that % we can analyse a unification as having no solutions % is that the unification always fails. %, % Unifying two preds is not erroneous as far as the % mode checker is concerned, but a mode _error_. Goal = disj([]), !:ModeInfo = !.ModeInfo % XXX deleting this exposes % a bug in the state variable % transformation ; Functor = functor(ConsId, IsExistConstruction, ArgVars), Unify = unify(X, Functor, Mode, Unification, UnifyContext), % % modecheck_unification sometimes needs to introduce % new goals to handle complicated sub-unifications % in deconstructions. The only time this can happen % during unique mode analysis is if the instmap is % unreachable, since inst_is_bound succeeds for not_reached. % (If it did in other cases, the code would be wrong since it % wouldn't have the correct determinism annotations.) % append_extra_goals(ExtraGoals0, ExtraGoals1, ExtraGoals), ( HowToCheckGoal = check_unique_modes, ExtraGoals \= no_extra_goals, instmap__is_reachable(InstMap0) -> error("unique_modes.m: re-modecheck of unification " ++ "encountered complicated sub-unifies") ; true ), handle_extra_goals(Unify, ExtraGoals, GoalInfo0, [X0 | ArgVars0], [X | ArgVars], InstMap0, Goal, !ModeInfo, !IO) ). %-----------------------------------------------------------------------------% % The argument unifications in a construction or deconstruction % unification must be simple assignments, they cannot be % complicated unifications. If they are, we split them out % into separate unifications by introducing fresh variables here. :- pred split_complicated_subunifies(unification::in, unification::out, list(prog_var)::in, list(prog_var)::out, extra_goals::out, mode_info::in, mode_info::out) is det. split_complicated_subunifies(Unification0, Unification, ArgVars0, ArgVars, ExtraGoals, !ModeInfo) :- ( Unification0 = deconstruct(X, ConsId, ArgVars0, ArgModes0, Det, CanCGC) -> ( split_complicated_subunifies_2(ArgVars0, ArgModes0, ArgVars1, ExtraGoals1, !ModeInfo) -> ExtraGoals = ExtraGoals1, ArgVars = ArgVars1, Unification = deconstruct(X, ConsId, ArgVars, ArgModes0, Det, CanCGC) ; error("split_complicated_subunifies_2 failed") ) ; Unification = Unification0, ArgVars = ArgVars0, ExtraGoals = no_extra_goals ). :- pred split_complicated_subunifies_2(list(prog_var)::in, list(uni_mode)::in, list(prog_var)::out, extra_goals::out, mode_info::in, mode_info::out) is semidet. split_complicated_subunifies_2([], [], [], no_extra_goals, !ModeInfo). split_complicated_subunifies_2([Var0 | Vars0], [UniMode0 | UniModes0], Vars, ExtraGoals, !ModeInfo) :- mode_info_get_module_info(!.ModeInfo, ModuleInfo), UniMode0 = (InitialInstX - InitialInstY -> FinalInstX - FinalInstY), ModeX = (InitialInstX -> FinalInstX), ModeY = (InitialInstY -> FinalInstY), mode_info_get_var_types(!.ModeInfo, VarTypes0), map__lookup(VarTypes0, Var0, VarType), ( mode_to_arg_mode(ModuleInfo, ModeX, VarType, top_in), mode_to_arg_mode(ModuleInfo, ModeY, VarType, top_in) -> make_complicated_sub_unify(Var0, Var, ExtraGoals0, !ModeInfo), % recursive call to handle the remaining variables... split_complicated_subunifies_2(Vars0, UniModes0, Vars1, ExtraGoals1, !ModeInfo), Vars = [Var | Vars1], append_extra_goals(ExtraGoals0, ExtraGoals1, ExtraGoals) ; split_complicated_subunifies_2(Vars0, UniModes0, Vars1, ExtraGoals, !ModeInfo), Vars = [Var0 | Vars1] ). :- pred make_complicated_sub_unify(prog_var::in, prog_var::out, extra_goals::out, mode_info::in, mode_info::out) is det. make_complicated_sub_unify(Var0, Var, ExtraGoals0, !ModeInfo) :- % introduce a new variable `Var' mode_info_get_varset(!.ModeInfo, VarSet0), mode_info_get_var_types(!.ModeInfo, VarTypes0), varset__new_var(VarSet0, Var, VarSet), map__lookup(VarTypes0, Var0, VarType), map__set(VarTypes0, Var, VarType, VarTypes), mode_info_set_varset(VarSet, !ModeInfo), mode_info_set_var_types(VarTypes, !ModeInfo), modecheck_unify__create_var_var_unification(Var0, Var, VarType, !.ModeInfo, ExtraGoal), % insert the new unification at % the start of the extra goals ExtraGoals0 = extra_goals([], [ExtraGoal]). modecheck_unify__create_var_var_unification(Var0, Var, Type, ModeInfo, Goal - GoalInfo) :- mode_info_get_context(ModeInfo, Context), mode_info_get_mode_context(ModeInfo, ModeContext), mode_context_to_unify_context(ModeInfo, ModeContext, UnifyContext), UnifyContext = unify_context(MainContext, SubContexts), create_atomic_unification(Var0, var(Var), Context, MainContext, SubContexts, Goal0 - GoalInfo0), % % compute the goal_info nonlocal vars for the newly created goal % (excluding the type_info vars -- they are added below). % N.B. This may overestimate the set of non-locals, % but that shouldn't cause any problems. % set__list_to_set([Var0, Var], NonLocals), goal_info_set_nonlocals(GoalInfo0, NonLocals, GoalInfo1), goal_info_set_context(GoalInfo1, Context, GoalInfo2), % % Look up the map(tvar, type_info_locn) in the proc_info, % since it is needed by polymorphism__unification_typeinfos % mode_info_get_module_info(ModeInfo, ModuleInfo), mode_info_get_predid(ModeInfo, PredId), mode_info_get_procid(ModeInfo, ProcId), module_info_pred_proc_info(ModuleInfo, PredId, ProcId, _PredInfo, ProcInfo), proc_info_typeinfo_varmap(ProcInfo, TypeInfoVarMap), % % Call polymorphism__unification_typeinfos to add the appropriate % type-info and type-class-info variables to the nonlocals % and to the unification. % ( Goal0 = unify(X, Y, Mode, Unification0, FinalUnifyContext) -> polymorphism__unification_typeinfos(Type, TypeInfoVarMap, Unification0, Unification, GoalInfo2, GoalInfo), Goal = unify(X, Y, Mode, Unification, FinalUnifyContext) ; error("modecheck_unify__create_var_var_unification") ). %-----------------------------------------------------------------------------% % Work out what kind of unification a var-var unification is. :- pred categorize_unify_var_var((mode)::in, (mode)::in, is_live::in, is_live::in, prog_var::in, prog_var::in, determinism::in, unify_context::in, map(prog_var, type)::in, unification::in, hlds_goal_expr::out, mode_info::in, mode_info::out) is det. % categorize_unify_var_var works out which category a unification % between a variable and another variable expression is - whether it is % an assignment, a simple test or a complicated unify. categorize_unify_var_var(ModeOfX, ModeOfY, LiveX, LiveY, X, Y, Det, UnifyContext, VarTypes, Unification0, Unify, !ModeInfo) :- mode_info_get_module_info(!.ModeInfo, ModuleInfo0), ( mode_is_output(ModuleInfo0, ModeOfX) -> Unification = assign(X, Y) ; mode_is_output(ModuleInfo0, ModeOfY) -> Unification = assign(Y, X) ; mode_is_unused(ModuleInfo0, ModeOfX), mode_is_unused(ModuleInfo0, ModeOfY) -> % For free-free unifications, we pretend for a moment that they % are an assignment to the dead variable - they will then % be optimized away. ( LiveX = dead -> Unification = assign(X, Y) ; LiveY = dead -> Unification = assign(Y, X) ; error("categorize_unify_var_var: free-free unify!") ) ; % % Check for unreachable unifications % ( mode_get_insts(ModuleInfo0, ModeOfX, not_reached, _) ; mode_get_insts(ModuleInfo0, ModeOfY, not_reached, _) ) -> % % For these, we can generate any old junk here -- % we just need to avoid calling modecheck_complicated_unify, % since that might abort. % Unification = simple_test(X, Y) ; map__lookup(VarTypes, X, Type), ( type_is_atomic(Type, ModuleInfo0), not type_has_user_defined_equality_pred(ModuleInfo0, Type, _) -> Unification = simple_test(X, Y) ; modecheck_complicated_unify(X, Y, Type, ModeOfX, ModeOfY, Det, UnifyContext, Unification0, Unification, !ModeInfo) ) ), % % Optimize away unifications with dead variables % and simple tests that cannot fail % by replacing them with `true'. % (The optimization of simple tests is necessary % because otherwise determinism analysis assumes they can fail. % The optimization of assignments to dead variables may be % necessary to stop the code generator from getting confused.) % Optimize away unifications which always fail by replacing % them with `fail'. % ( Unification = assign(AssignTarget, _), mode_info_var_is_live(!.ModeInfo, AssignTarget, dead) -> Unify = conj([]) ; Unification = simple_test(_, _), Det = det -> Unify = conj([]) ; Det = failure -> % This optimisation is safe because the only way that % we can analyse a unification as having no solutions % is that the unification always fails. % % Unifying two preds is not erroneous as far as the % mode checker is concerned, but a mode _error_. Unify = disj([]) ; Unify = unify(X, var(Y), ModeOfX - ModeOfY, Unification, UnifyContext) ). % % modecheck_complicated_unify does some extra checks that are needed % for mode-checking complicated unifications. % :- pred modecheck_complicated_unify(prog_var::in, prog_var::in, (type)::in, (mode)::in, (mode)::in, determinism::in, unify_context::in, unification::in, unification::out, mode_info::in, mode_info::out) is det. modecheck_complicated_unify(X, Y, Type, ModeOfX, ModeOfY, Det, UnifyContext, Unification0, Unification, !ModeInfo) :- % % Build up the unification % mode_info_get_module_info(!.ModeInfo, ModuleInfo0), mode_get_insts(ModuleInfo0, ModeOfX, InitialInstX, FinalInstX), mode_get_insts(ModuleInfo0, ModeOfY, InitialInstY, FinalInstY), UniMode = ((InitialInstX - InitialInstY) -> (FinalInstX - FinalInstY)), determinism_components(Det, CanFail, _), ( Unification0 = complicated_unify(_, _, UnifyTypeInfoVars0) -> UnifyTypeInfoVars = UnifyTypeInfoVars0 ; error("modecheck_complicated_unify") ), Unification = complicated_unify(UniMode, CanFail, UnifyTypeInfoVars), % % check that all the type_info or type_class_info variables used % by the polymorphic unification are ground. % ( UnifyTypeInfoVars = [] -> % optimize common case true ; list__length(UnifyTypeInfoVars, NumTypeInfoVars), list__duplicate(NumTypeInfoVars, ground(shared, none), ExpectedInsts), mode_info_set_call_context(unify(UnifyContext), !ModeInfo), NeedExactMatch = no, InitialArgNum = 0, modecheck_var_has_inst_list(UnifyTypeInfoVars, ExpectedInsts, NeedExactMatch, InitialArgNum, _InstVarSub, !ModeInfo), % We can ignore _InstVarSub since type_info variables % should not have variable insts. mode_info_unset_call_context(!ModeInfo) ), mode_info_get_module_info(!.ModeInfo, ModuleInfo3), ( mode_info_get_errors(!.ModeInfo, Errors), Errors \= [] -> true ; % % Check that we're not trying to do a polymorphic unification % in a mode other than (in, in). % [Actually we also allow `any' insts, since the (in, in) % mode of unification for types which have `any' insts must % also be able to handle (in(any), in(any)) unifications.] % Type = term__variable(_), \+ inst_is_ground_or_any(ModuleInfo3, InitialInstX) -> set__singleton_set(WaitingVars, X), mode_info_error(WaitingVars, mode_error_poly_unify(X, InitialInstX), !ModeInfo) ; Type = term__variable(_), \+ inst_is_ground_or_any(ModuleInfo3, InitialInstY) -> set__singleton_set(WaitingVars, Y), mode_info_error(WaitingVars, mode_error_poly_unify(Y, InitialInstY), !ModeInfo) ; % % check that we're not trying to do a higher-order unification % type_is_higher_order(Type, _, PredOrFunc, _, _) -> % We do not want to report this as an error % if it occurs in a compiler-generated % predicate - instead, we delay the error % until runtime so that it only occurs if % the compiler-generated predicate gets called. % not_reached is considered bound, so the % error message would be spurious if the % instmap is unreachable. mode_info_get_predid(!.ModeInfo, PredId), module_info_pred_info(ModuleInfo3, PredId, PredInfo), mode_info_get_instmap(!.ModeInfo, InstMap0), ( ( is_unify_or_compare_pred(PredInfo) ; instmap__is_unreachable(InstMap0) ) -> true ; set__init(WaitingVars), mode_info_error(WaitingVars, mode_error_unify_pred(X, error_at_var(Y), Type, PredOrFunc), !ModeInfo) ) ; % % Ensure that we will generate code for the unification % procedure that will be used to implement this complicated % unification. % type_to_ctor_and_args(Type, TypeCtor, _) -> mode_info_get_context(!.ModeInfo, Context), mode_info_get_instvarset(!.ModeInfo, InstVarSet), unify_proc__request_unify(TypeCtor - UniMode, InstVarSet, Det, Context, ModuleInfo3, ModuleInfo), mode_info_set_module_info(ModuleInfo, !ModeInfo) ; true ). % categorize_unify_var_lambda works out which category a unification % between a variable and a lambda expression is - whether it is a construction % unification or a deconstruction. It also works out whether it will % be deterministic or semideterministic. :- pred categorize_unify_var_lambda((mode)::in, list(mode)::in, prog_var::in, list(prog_var)::in, pred_or_func::in, unify_rhs::in, unify_rhs::out, unification::in, unification::out, mode_info::in, mode_info::out) is det. categorize_unify_var_lambda(ModeOfX, ArgModes0, X, ArgVars, PredOrFunc, RHS0, RHS, Unification0, Unification, !ModeInfo) :- % if we are re-doing mode analysis, preserve the existing cons_id list__length(ArgVars, Arity), ( Unification0 = construct(_, ConsId0, _, _, _, _, MaybeSize0) -> MaybeSize = MaybeSize0, ConsId = ConsId0 ; Unification0 = deconstruct(_, ConsId1, _, _, _, _) -> MaybeSize = no, ConsId = ConsId1 ; % the real cons_id will be computed by lambda.m; % we just put in a dummy one for now MaybeSize = no, ConsId = cons(unqualified("__LambdaGoal__"), Arity) ), mode_info_get_module_info(!.ModeInfo, ModuleInfo), mode_util__modes_to_uni_modes(ArgModes0, ArgModes0, ModuleInfo, ArgModes), mode_info_get_instmap(!.ModeInfo, InstMap), ( mode_is_output(ModuleInfo, ModeOfX) -> ( % If pred_consts are present, lambda expansion % has already been done. Rerunning mode analysis % should not produce a lambda_goal which cannot % be directly converted back into a higher-order % predicate constant. % If the instmap is not reachable, the call % may have been handled as an implied mode, % since not_reached is considered to be bound. % In this case the lambda_goal may not be % converted back to a predicate constant, but % that doesn't matter since the code will be % pruned away later by simplify.m. ConsId = pred_const(PredId, ProcId, EvalMethod), instmap__is_reachable(InstMap) -> ( RHS0 = lambda_goal(_, _, EvalMethod, _, _, _, _, _, Goal), Goal = call(PredId, ProcId, _, _, _, _) - _ -> module_info_pred_info(ModuleInfo, PredId, PredInfo), PredModule = pred_info_module(PredInfo), PredName = pred_info_name(PredInfo), RHS = functor( cons(qualified(PredModule, PredName), Arity), no, ArgVars) ; error("categorize_unify_var_lambda - \ reintroduced lambda goal") ) ; RHS = RHS0 ), Unification = construct(X, ConsId, ArgVars, ArgModes, construct_dynamically, cell_is_unique, MaybeSize) ; instmap__is_reachable(InstMap) -> % If it's a deconstruction, it is a mode error. % The error message would be incorrect in unreachable % code, since not_reached is considered bound. set__init(WaitingVars), mode_info_get_var_types(!.ModeInfo, VarTypes0), map__lookup(VarTypes0, X, Type), mode_info_error(WaitingVars, mode_error_unify_pred(X, error_at_lambda(ArgVars, ArgModes0), Type, PredOrFunc), !ModeInfo), % return any old garbage Unification = Unification0, RHS = RHS0 ; Unification = Unification0, RHS = RHS0 ). % categorize_unify_var_functor works out which category a unification % between a variable and a functor is - whether it is a construction % unification or a deconstruction. It also works out whether it will % be deterministic or semideterministic. :- pred categorize_unify_var_functor((mode)::in, list(mode)::in, list(mode)::in, prog_var::in, cons_id::in, list(prog_var)::in, map(prog_var, type)::in, unify_context::in, unification::in, unification::out, mode_info::in, mode_info::out) is det. categorize_unify_var_functor(ModeOfX, ModeOfXArgs, ArgModes0, X, NewConsId, ArgVars, VarTypes, UnifyContext, Unification0, Unification, !ModeInfo) :- mode_info_get_module_info(!.ModeInfo, ModuleInfo), map__lookup(VarTypes, X, TypeOfX), % if we are re-doing mode analysis, preserve the existing cons_id ( Unification0 = construct(_, ConsId0, _, _, _, _, MaybeSize0) -> MaybeSize = MaybeSize0, ConsId = ConsId0 ; Unification0 = deconstruct(_, ConsId1, _, _, _, _) -> MaybeSize = no, ConsId = ConsId1 ; MaybeSize = no, ConsId = NewConsId ), mode_util__modes_to_uni_modes(ModeOfXArgs, ArgModes0, ModuleInfo, ArgModes), ( mode_is_output(ModuleInfo, ModeOfX) -> % It's a construction. Unification = construct(X, ConsId, ArgVars, ArgModes, construct_dynamically, cell_is_unique, MaybeSize), % For existentially quantified data types, % check that any type_info or type_class_info variables in the % construction are ground. check_type_info_args_are_ground(ArgVars, VarTypes, UnifyContext, !ModeInfo) ; % It's a deconstruction. ( % If the variable was already known to be bound % to a single particular functor, then the % unification either always succeeds or always % fails. In the latter case, the final inst will % be `not_reached' or `bound([])'. So if both % the initial and final inst are `bound([_])', % then the unification must be deterministic. mode_get_insts(ModuleInfo, ModeOfX, InitialInst0, FinalInst0), inst_expand(ModuleInfo, InitialInst0, InitialInst), inst_expand(ModuleInfo, FinalInst0, FinalInst), InitialInst = bound(_, [_]), FinalInst = bound(_, [_]) -> CanFail = cannot_fail ; % If the type has only one constructor, % then the unification cannot fail type_constructors(TypeOfX, ModuleInfo, Constructors), Constructors = [_] -> CanFail = cannot_fail ; % Otherwise, it can fail CanFail = can_fail, mode_info_get_instmap(!.ModeInfo, InstMap0), ( type_is_higher_order(TypeOfX, _, PredOrFunc, _, _), instmap__is_reachable(InstMap0) -> set__init(WaitingVars), mode_info_error(WaitingVars, mode_error_unify_pred(X, error_at_functor(ConsId, ArgVars), TypeOfX, PredOrFunc), !ModeInfo) ; true ) ), Unification = deconstruct(X, ConsId, ArgVars, ArgModes, CanFail, no) ). % Check that any type_info or type_class_info variables % in the argument list are ground. :- pred check_type_info_args_are_ground(list(prog_var)::in, map(prog_var, type)::in, unify_context::in, mode_info::in, mode_info::out) is det. check_type_info_args_are_ground([], _VarTypes, _UnifyContext, !ModeInfo). check_type_info_args_are_ground([ArgVar | ArgVars], VarTypes, UnifyContext, !ModeInfo) :- ( map__lookup(VarTypes, ArgVar, ArgType), is_introduced_type_info_type(ArgType) -> mode_info_set_call_context(unify(UnifyContext), !ModeInfo), NeedExactMatch = no, InitialArgNum = 0, modecheck_var_has_inst_list([ArgVar], [ground(shared, none)], NeedExactMatch, InitialArgNum, _InstVarSub, !ModeInfo), check_type_info_args_are_ground(ArgVars, VarTypes, UnifyContext, !ModeInfo), mode_info_unset_call_context(!ModeInfo) ; true ). %-----------------------------------------------------------------------------% :- pred bind_args((inst)::in, list(prog_var)::in, list(maybe(inst))::in, mode_info::in, mode_info::out) is semidet. bind_args(not_reached, _, _, !ModeInfo) :- instmap__init_unreachable(InstMap), mode_info_set_instmap(InstMap, !ModeInfo). bind_args(ground(Uniq, none), Args, UnifyArgInsts, !ModeInfo) :- ground_args(Uniq, Args, UnifyArgInsts, !ModeInfo). bind_args(bound(_Uniq, List), Args, UnifyArgInsts, !ModeInfo) :- ( List = [] -> % the code is unreachable instmap__init_unreachable(InstMap), mode_info_set_instmap(InstMap, !ModeInfo) ; List = [functor(_, InstList)], bind_args_2(Args, InstList, UnifyArgInsts, !ModeInfo) ). bind_args(constrained_inst_vars(_, Inst), Args, UnifyArgInsts, !ModeInfo) :- bind_args(Inst, Args, UnifyArgInsts, !ModeInfo). :- pred bind_args_2(list(prog_var)::in, list(inst)::in, list(maybe(inst))::in, mode_info::in, mode_info::out) is semidet. bind_args_2([], [], [], !ModeInfo). bind_args_2([Arg | Args], [Inst | Insts], [UnifyArgInst | UnifyArgInsts], !ModeInfo) :- modecheck_set_var_inst(Arg, Inst, UnifyArgInst, !ModeInfo), bind_args_2(Args, Insts, UnifyArgInsts, !ModeInfo). :- pred ground_args(uniqueness::in, list(prog_var)::in, list(maybe(inst))::in, mode_info::in, mode_info::out) is semidet. ground_args(_Uniq, [], [], !ModeInfo). ground_args(Uniq, [Arg | Args], [UnifyArgInst | UnifyArgInsts], !ModeInfo) :- modecheck_set_var_inst(Arg, ground(Uniq, none), UnifyArgInst, !ModeInfo), ground_args(Uniq, Args, UnifyArgInsts, !ModeInfo). %-----------------------------------------------------------------------------% % get_mode_of_args(FinalInst, InitialArgInsts, ArgModes): % for a var-functor unification, % given the final inst of the var % and the initial insts of the functor arguments, % compute the modes of the functor arguments :- pred get_mode_of_args(inst, list(inst), list(mode)). :- mode get_mode_of_args(in, in, out) is semidet. get_mode_of_args(not_reached, ArgInsts, ArgModes) :- mode_set_args(ArgInsts, not_reached, ArgModes). get_mode_of_args(any(Uniq), ArgInsts, ArgModes) :- mode_set_args(ArgInsts, any(Uniq), ArgModes). get_mode_of_args(ground(Uniq, none), ArgInsts, ArgModes) :- mode_set_args(ArgInsts, ground(Uniq, none), ArgModes). get_mode_of_args(bound(_Uniq, List), ArgInstsA, ArgModes) :- ( List = [] -> % the code is unreachable mode_set_args(ArgInstsA, not_reached, ArgModes) ; List = [functor(_Name, ArgInstsB)], get_mode_of_args_2(ArgInstsA, ArgInstsB, ArgModes) ). get_mode_of_args(constrained_inst_vars(_, Inst), ArgInsts, ArgModes) :- get_mode_of_args(Inst, ArgInsts, ArgModes). :- pred get_mode_of_args_2(list(inst), list(inst), list(mode)). :- mode get_mode_of_args_2(in, in, out) is semidet. get_mode_of_args_2([], [], []). get_mode_of_args_2([InstA | InstsA], [InstB | InstsB], [Mode | Modes]) :- Mode = (InstA -> InstB), get_mode_of_args_2(InstsA, InstsB, Modes). :- pred mode_set_args(list(inst), inst, list(mode)). :- mode mode_set_args(in, in, out) is det. mode_set_args([], _, []). mode_set_args([Inst | Insts], FinalInst, [Mode | Modes]) :- Mode = (Inst -> FinalInst), mode_set_args(Insts, FinalInst, Modes). %-----------------------------------------------------------------------------% %-----------------------------------------------------------------------------%