%-----------------------------------------------------------------------------% % vim: ft=mercury ts=4 sw=4 et %-----------------------------------------------------------------------------% % Copyright (C) 2004-2012 The University of Melbourne. % Copyright (C) 2017 The Mercury Team. % This file may only be copied under the terms of the GNU General % Public License - see the file COPYING in the Mercury distribution. %-----------------------------------------------------------------------------% % % File: exception_analysis.m. % Author: juliensf. % % This module performs an exception tracing analysis. The aim is to annotate % the HLDS with information about whether each procedure might or will not % throw an exception. % % This information can be useful to the compiler when applying certain types % of optimization. % % After running the analysis the exception behaviour of each procedure % is one of: % % (1) will_not_throw_exception % (2) may_throw_an_exception % (3) conditional % % (1) guarantees that, for all inputs, the procedure will not throw an % exception. % % (2) means that a call to that procedure might result in an exception % being thrown for at least some inputs. % % We distinguish between two kinds of exception. Those that % are ultimately a result of a call to exception.throw/1, which % we refer to as "user exceptions" and those that result from a % unification or comparison where one of the types involved has % a user-defined equality/comparison predicate that throws % an exception. We refer to the latter kind, as "type exceptions". % % This means that for some polymorphic procedures we cannot % say what will happen until we know the values of the type variables. % And so we have ... % % (3) means that the exception status of the procedure is dependent upon the % values of some higher-order variables, or the values of some type % variables or both. This means that we cannot say anything definite % about the procedure but for calls to the procedure where have the % necessary information we can say what will happen. % % In the event that we cannot determine the exception status we just assume % the worst and mark the procedure as maybe throwing a user exception. % % For procedures that are defined using the FFI we currently assume that if a % procedure will not make calls back to Mercury then it cannot throw % a Mercury exception; if it does make calls to Mercury then it might % throw an exception. % % NOTE: Some backends, e.g the Java backend, use exceptions in the target % language for various things but we're not interested in that here. % % TODO: % - improve handling of polymorphic procedures (requires type features % analysis) % - higher order stuff % - check what user-defined equality and comparison preds % actually do rather than assuming that they always % may throw exceptions. % - handle existential and solver types - currently we just % assume that any call to unify or compare for these types % might result in an exception being thrown. % - Fix optimizations to use exception information from the analysis % registry correctly - predicates in goal_form.m and the optimizations % that use them need to be updated. % % XXX We need to be a bit careful with transformations like tabling that % might add calls to exception.throw - at the moment this isn't a problem % because exception analysis takes place after the tabling transformation. % %----------------------------------------------------------------------------% :- module transform_hlds.exception_analysis. :- interface. :- import_module analysis. :- import_module hlds. :- import_module hlds.hlds_module. :- import_module hlds.hlds_pred. :- import_module parse_tree. :- import_module parse_tree.prog_data_pragma. %----------------------------------------------------------------------------% % Perform the exception analysis on a module. % :- pred analyse_exceptions_in_module(module_info::in, module_info::out) is det. % Look the exception status of the given procedure. This predicate % is intended to be used by optimisations that use exception analysis % information, *not* for use within the exception analysis itself. % This predicate abstracts away differences between % intermodule-optimization and intermodule-analysis. % % NOTE: if intermodule-analysis is enabled then this procedure will % update the IMDG as well. % :- pred lookup_exception_analysis_result(pred_proc_id::in, exception_status::out, module_info::in, module_info::out) is det. %----------------------------------------------------------------------------% % % Types and instances for the intermodule analysis framework % :- type exception_analysis_answer. :- instance analysis(no_func_info, any_call, exception_analysis_answer). :- instance partial_order(no_func_info, exception_analysis_answer). :- instance answer_pattern(no_func_info, exception_analysis_answer). :- instance to_term(exception_analysis_answer). %----------------------------------------------------------------------------% %----------------------------------------------------------------------------% :- implementation. :- import_module check_hlds. :- import_module check_hlds.type_util. :- import_module hlds.hlds_dependency_graph. :- import_module hlds.hlds_goal. :- import_module hlds.vartypes. :- import_module libs. :- import_module libs.dependency_graph. :- import_module libs.globals. :- import_module libs.op_mode. :- import_module libs.options. :- import_module mdbcomp. :- import_module mdbcomp.builtin_modules. :- import_module mdbcomp.prim_data. :- import_module mdbcomp.sym_name. :- import_module parse_tree.prog_data. :- import_module parse_tree.prog_data_foreign. :- import_module parse_tree.prog_type. :- import_module transform_hlds.intermod. :- import_module transform_hlds.mmc_analysis. :- import_module bool. :- import_module list. :- import_module map. :- import_module maybe. :- import_module require. :- import_module set. :- import_module term. %----------------------------------------------------------------------------% % % Perform exception analysis on a module. % analyse_exceptions_in_module(!ModuleInfo) :- module_info_ensure_dependency_info(!ModuleInfo, DepInfo), SCCs = dependency_info_get_bottom_up_sccs(DepInfo), list.foldl(check_scc_for_exceptions, SCCs, !ModuleInfo), module_info_get_proc_analysis_kinds(!.ModuleInfo, ProcAnalysisKinds0), set.insert(pak_exception, ProcAnalysisKinds0, ProcAnalysisKinds), module_info_set_proc_analysis_kinds(ProcAnalysisKinds, !ModuleInfo), module_info_get_globals(!.ModuleInfo, Globals), globals.get_op_mode(Globals, OpMode), ( if OpMode = opm_top_args(opma_augment(opmau_make_analysis_registry)) then % Record results if making the analysis registry. We do this in a % separate pass so that we record results for exported % `:- pragma external_{pred/func}' procedures, which don't get % analysed because we don't have clauses for them. module_info_get_analysis_info(!.ModuleInfo, AnalysisInfo0), module_info_get_valid_pred_ids(!.ModuleInfo, PredIds), list.foldl(maybe_record_exception_result(!.ModuleInfo), PredIds, AnalysisInfo0, AnalysisInfo), module_info_set_analysis_info(AnalysisInfo, !ModuleInfo) else true ). %----------------------------------------------------------------------------% % % Perform exception analysis on a SCC. % :- type excp_proc_result ---> excp_proc_result( % The ppid of the procedure whose analysis results are % stored in this structure. epr_ppid :: pred_proc_id, % Exception status of this procedure not counting any input % from (mutually-)recursive inputs. epr_status :: exception_status, % The collective type status of the types of the terms that % are arguments of (mutually-)recursive calls. epr_rec_calls :: type_excp_status, % The analysis status used for intermodule-analysis. % This should be `no' if we are not compiling with % intermodule analysis enabled. epr_maybe_analysis_status :: maybe(analysis_status) ). :- pred check_scc_for_exceptions(scc::in, module_info::in, module_info::out) is det. check_scc_for_exceptions(SCC, !ModuleInfo) :- check_procs_for_exceptions(SCC, ProcResults, !ModuleInfo), % The `Results' above are the results of analysing each individual % procedure in the SCC - we now have to combine them in a meaningful way. excp_combine_individual_proc_results(ProcResults, Status, MaybeAnalysisStatus), ProcExceptionInfo = proc_exception_info(Status, MaybeAnalysisStatus), set.foldl(set_exception_info(ProcExceptionInfo), SCC, !ModuleInfo). :- pred set_exception_info(proc_exception_info::in, pred_proc_id::in, module_info::in, module_info::out) is det. set_exception_info(ProcExceptionInfo, PPId, !ModuleInfo) :- module_info_pred_proc_info(!.ModuleInfo, PPId, PredInfo0, ProcInfo0), proc_info_set_exception_info(yes(ProcExceptionInfo), ProcInfo0, ProcInfo), module_info_set_pred_proc_info(PPId, PredInfo0, ProcInfo, !ModuleInfo). % Check each procedure in the SCC individually. % :- pred check_procs_for_exceptions(scc::in, list(excp_proc_result)::out, module_info::in, module_info::out) is det. check_procs_for_exceptions(SCC, Result, !ModuleInfo) :- set.foldl2(check_proc_for_exceptions(SCC), SCC, [], Result, !ModuleInfo). % Examine how procedures interact with other procedures that are % mutually-recursive to them. % :- pred excp_combine_individual_proc_results(list(excp_proc_result)::in, exception_status::out, maybe(analysis_status)::out) is det. excp_combine_individual_proc_results([], _, _) :- unexpected($module, $pred, "Empty SCC during exception analysis."). excp_combine_individual_proc_results(ProcResults @ [_ | _], SCC_Result, MaybeAnalysisStatus) :- ( if % If none of the procedures may throw an exception or are conditional % then the SCC cannot throw an exception either. all [ProcResult] ( list.member(ProcResult, ProcResults) => ProcResult ^ epr_status = will_not_throw ) then SCC_Result = will_not_throw else if % If none of the procedures may throw an exception but at least one of % them is conditional then somewhere in the SCC there is a call to % unify or compare that may rely on the types of the polymorphically % typed arguments. % % We need to check that any recursive calls do not introduce types % that might have user-defined equality or comparison predicate that % throw exceptions. % all [EResult] ( list.member(EResult, ProcResults) => EResult ^ epr_status \= may_throw(_) ), some [CResult] ( list.member(CResult, ProcResults), CResult ^ epr_status = throw_conditional ) then SCC_Result = handle_mixed_conditional_scc(ProcResults) else if % If none of the procedures can throw a user_exception but one or more % can throw a type_exception then mark the SCC as maybe throwing a % type_exception. all [EResult] ( list.member(EResult, ProcResults) => EResult ^ epr_status \= may_throw(user_exception) ), some [TResult] ( list.member(TResult, ProcResults), TResult ^ epr_status = may_throw(type_exception) ) then SCC_Result = may_throw(type_exception) else SCC_Result = may_throw(user_exception) ), excp_combine_proc_result_maybe_analysis_statuses(ProcResults, MaybeAnalysisStatus). % XXX There is some code duplication with trailing_analysis.m here ... % we should factor out this code into a utility module for % intermodule-analysis at some point. % :- pred excp_combine_proc_result_maybe_analysis_statuses( list(excp_proc_result)::in, maybe(analysis_status)::out) is det. excp_combine_proc_result_maybe_analysis_statuses(ProcResults, MaybeAnalysisStatus) :- list.map(maybe_analysis_status, ProcResults, MaybeAnalysisStatuses), list.foldl(combine_maybe_analysis_status, MaybeAnalysisStatuses, yes(optimal), MaybeAnalysisStatus). :- pred maybe_analysis_status(excp_proc_result::in, maybe(analysis_status)::out) is det. maybe_analysis_status(ProcResult, ProcResult ^ epr_maybe_analysis_status). %----------------------------------------------------------------------------% % % Process individual procedures. % :- pred check_proc_for_exceptions(scc::in, pred_proc_id::in, list(excp_proc_result)::in, list(excp_proc_result)::out, module_info::in, module_info::out) is det. check_proc_for_exceptions(SCC, PPId, !Results, !ModuleInfo) :- module_info_pred_proc_info(!.ModuleInfo, PPId, _, ProcInfo), proc_info_get_goal(ProcInfo, Body), proc_info_get_vartypes(ProcInfo, VarTypes), module_info_get_globals(!.ModuleInfo, Globals), globals.lookup_bool_option(Globals, intermodule_analysis, IntermodAnalysis), MaybeAnalysisStatus0 = maybe_optimal(IntermodAnalysis), Result0 = excp_proc_result(PPId, will_not_throw, type_will_not_throw, MaybeAnalysisStatus0), check_goal_for_exceptions(SCC, VarTypes, Body, Result0, Result, !ModuleInfo), list.cons(Result, !Results). :- pred check_goal_for_exceptions(scc::in, vartypes::in, hlds_goal::in, excp_proc_result::in, excp_proc_result::out, module_info::in, module_info::out) is det. check_goal_for_exceptions(SCC, VarTypes, hlds_goal(GoalExpr, GoalInfo), !Result, !ModuleInfo) :- ( if goal_info_get_determinism(GoalInfo) = detism_erroneous then !Result ^ epr_status := may_throw(user_exception) else check_goal_for_exceptions_2(SCC, VarTypes, GoalExpr, GoalInfo, !Result, !ModuleInfo) ). :- pred check_goal_for_exceptions_2(scc::in, vartypes::in, hlds_goal_expr::in, hlds_goal_info::in, excp_proc_result::in, excp_proc_result::out, module_info::in, module_info::out) is det. check_goal_for_exceptions_2(SCC, VarTypes, GoalExpr, GoalInfo, !Result, !ModuleInfo) :- ( GoalExpr = unify(_, _, _, Kind, _), ( Kind = complicated_unify(_, _, _), unexpected($module, $pred, "complicated unify during exception analysis.") ; ( Kind = construct(_, _, _, _, _, _, _) ; Kind = deconstruct(_, _, _, _, _, _) ; Kind = assign(_, _) ; Kind = simple_test(_, _) ) ) ; GoalExpr = plain_call(CallPredId, CallProcId, Args, _, _, _), check_goal_for_exceptions_plain_call(SCC, VarTypes, CallPredId, CallProcId, Args, !Result, !ModuleInfo) ; GoalExpr = generic_call(Details, Args, _, _, _), check_goal_for_exceptions_generic_call(VarTypes, Details, Args, GoalInfo, !Result, !ModuleInfo) ; GoalExpr = call_foreign_proc(Attributes, _, _, _, _, _, _), % NOTE: for --intermodule-analysis the results for for foreign_procs % will *always* be optimal (since we always rely on user annotation), % so there's nothing to do here. MayCallMercury = get_may_call_mercury(Attributes), ( MayCallMercury = proc_may_call_mercury, get_may_throw_exception(Attributes) = MayThrowException, % We do not need to deal with erroneous predicates here because % they will have already been processed. ( MayThrowException = default_exception_behaviour, !Result ^ epr_status := may_throw(user_exception) ; MayThrowException = proc_will_not_throw_exception ) ; MayCallMercury = proc_will_not_call_mercury ) ; ( GoalExpr = disj(Goals) ; GoalExpr = conj(_, Goals) ), check_goals_for_exceptions(SCC, VarTypes, Goals, !Result, !ModuleInfo) ; GoalExpr = switch(_, _, Cases), CaseGoals = list.map((func(case(_, _, CaseGoal)) = CaseGoal), Cases), check_goals_for_exceptions(SCC, VarTypes, CaseGoals, !Result, !ModuleInfo) ; GoalExpr = if_then_else(_, If, Then, Else), check_goals_for_exceptions(SCC, VarTypes, [If, Then, Else], !Result, !ModuleInfo) ; GoalExpr = negation(SubGoal), check_goal_for_exceptions(SCC, VarTypes, SubGoal, !Result, !ModuleInfo) ; GoalExpr = scope(Reason, SubGoal), ( if Reason = from_ground_term(_, FGT), ( FGT = from_ground_term_construct ; FGT = from_ground_term_deconstruct ) then true else check_goal_for_exceptions(SCC, VarTypes, SubGoal, !Result, !ModuleInfo) ) ; GoalExpr = shorthand(_), % These should have been expanded out by now. unexpected($module, $pred, "shorthand goal encountered during exception analysis.") ). :- pred check_goal_for_exceptions_plain_call(scc::in, vartypes::in, pred_id::in, proc_id::in, list(prog_var)::in, excp_proc_result::in, excp_proc_result::out, module_info::in, module_info::out) is det. check_goal_for_exceptions_plain_call(SCC, VarTypes, CallPredId, CallProcId, CallArgs, !Result, !ModuleInfo) :- CallPPId = proc(CallPredId, CallProcId), module_info_pred_info(!.ModuleInfo, CallPredId, CallPredInfo), ( if % Handle (mutually-)recursive calls. set.member(CallPPId, SCC) then lookup_var_types(VarTypes, CallArgs, Types), TypeStatus = excp_check_types(!.ModuleInfo, Types), excp_combine_type_status(TypeStatus, !.Result ^ epr_rec_calls, NewTypeStatus), !Result ^ epr_rec_calls := NewTypeStatus else if pred_info_is_builtin(CallPredInfo) then % Builtins won't throw exceptions. true else if % Handle unify and compare. ( ModuleName = pred_info_module(CallPredInfo), any_mercury_builtin_module(ModuleName), Name = pred_info_name(CallPredInfo), Arity = pred_info_orig_arity(CallPredInfo), ( SpecialPredId = spec_pred_compare ; SpecialPredId = spec_pred_unify ), special_pred_name_arity(SpecialPredId, Name, _, Arity) ; pred_info_get_origin(CallPredInfo, Origin), Origin = origin_special_pred(SpecialPredId, _), ( SpecialPredId = spec_pred_compare ; SpecialPredId = spec_pred_unify ) ) then % For unification/comparison the exception status depends upon the % types of the arguments. In particular whether some component of % that type has a user-defined equality/comparison predicate that % throws an exception. module_info_get_globals(!.ModuleInfo, Globals), globals.lookup_bool_option(Globals, intermodule_analysis, IntermodAnalysis), MaybeAnalysisStatus = maybe_optimal(IntermodAnalysis), excp_check_vars(!.ModuleInfo, VarTypes, CallArgs, MaybeAnalysisStatus, !Result) else excp_check_nonrecursive_call(VarTypes, CallPPId, CallArgs, CallPredInfo, !Result, !ModuleInfo) ). :- pred check_goal_for_exceptions_generic_call(vartypes::in, generic_call::in, list(prog_var)::in, hlds_goal_info::in, excp_proc_result::in, excp_proc_result::out, module_info::in, module_info::out) is det. check_goal_for_exceptions_generic_call(VarTypes, Details, Args, GoalInfo, !Result, !ModuleInfo) :- module_info_get_globals(!.ModuleInfo, Globals), globals.lookup_bool_option(Globals, intermodule_analysis, IntermodAnalysis), ( Details = higher_order(Var, _, _, _), ClosureValueMap = goal_info_get_ho_values(GoalInfo), ( if map.search(ClosureValueMap, Var, ClosureValues) then get_closures_exception_status(IntermodAnalysis, ClosureValues, MaybeWillNotThrow, MaybeAnalysisStatus, !ModuleInfo), ( MaybeWillNotThrow = maybe_will_not_throw(ConditionalProcs), ( ConditionalProcs = [] % The possible values of the higher-order variable are all % procedures that are known not to throw exceptions. ; ConditionalProcs = [_ | _], % For 'conditional' procedures we need to make sure that % if any type variables are bound at the generic_call % site, then this does not cause the closure to throw an % exception (because of a user-defined equality or % comparison predicate that throws an exception.) % % If we can resolve all of the polymorphism at this % generic_call site, then we can reach a definite % conclusion about it. % % If we cannot do so, then we propagate the 'conditional' % status to the current predicate if all the type % variables involved are universally quantified, or mark % it as throwing an exception if some of them are % existentially quantified. % % XXX This is too conservative but we don't currently % perform a fine-grained enough analysis of where % out-of-line unifications/comparisons occur to be able to % do better. excp_check_vars(!.ModuleInfo, VarTypes, Args, MaybeAnalysisStatus, !Result) ) ; MaybeWillNotThrow = may_throw, !Result ^ epr_status := may_throw(user_exception) ) else !Result ^ epr_status := may_throw(user_exception) ) ; % XXX We could do better with class methods. Details = class_method(_, _, _, _), !Result ^ epr_status := may_throw(user_exception) ; Details = event_call(_) ; Details = cast(_) ). :- pred check_goals_for_exceptions(scc::in, vartypes::in, list(hlds_goal)::in, excp_proc_result::in, excp_proc_result::out, module_info::in, module_info::out) is det. check_goals_for_exceptions(_, _, [], !Result, !ModuleInfo). check_goals_for_exceptions(SCC, VarTypes, [Goal | Goals], !Result, !ModuleInfo) :- check_goal_for_exceptions(SCC, VarTypes, Goal, !Result, !ModuleInfo), % We can stop searching if we find a user exception. However if we find % a type exception then we still need to check that there is not a user % exception somewhere in the rest of the SCC. CurrentStatus = !.Result ^ epr_status, ( CurrentStatus = may_throw(user_exception) ; ( CurrentStatus = will_not_throw ; CurrentStatus = throw_conditional ; CurrentStatus = may_throw(type_exception) ), check_goals_for_exceptions(SCC, VarTypes, Goals, !Result, !ModuleInfo) ). %----------------------------------------------------------------------------% % % Further code to handle higher-order variables. % % The exception status of a collection of procedures that can be called % through a higher-order variable. % :- type closures_exception_status ---> may_throw % One or more of the closures throws an exception. ; maybe_will_not_throw(list(pred_proc_id)). % None of the procedures throws a user exception, but the ones in % the list are conditional. Any polymorphic/higher-order args % needed to either be checked at the generic_call site or % the conditional status needs to be propagated up the call-graph % to a point where it can be resolved. % For the set of procedures that might be called through a particular % higher-order variable at a particular program point (as determined by % closure analysis), work out what the overall exception and analysis % status is going to be. % :- pred get_closures_exception_status(bool::in, set(pred_proc_id)::in, closures_exception_status::out, maybe(analysis_status)::out, module_info::in, module_info::out) is det. get_closures_exception_status(IntermodAnalysis, Closures, Conditionals, AnalysisStatus, !ModuleInfo) :- AnalysisStatus0 = maybe_optimal(IntermodAnalysis), set.fold3( get_closure_exception_status(IntermodAnalysis), Closures, maybe_will_not_throw([]), Conditionals, AnalysisStatus0, AnalysisStatus, !ModuleInfo). :- pred get_closure_exception_status(bool::in, pred_proc_id::in, closures_exception_status::in, closures_exception_status::out, maybe(analysis_status)::in, maybe(analysis_status)::out, module_info::in, module_info::out) is det. get_closure_exception_status(IntermodAnalysis, PPId, !MaybeWillNotThrow, !AS, !ModuleInfo) :- module_info_pred_proc_info(!.ModuleInfo, PPId, PredInfo, ProcInfo), ( if IntermodAnalysis = yes, pred_info_is_imported_not_external(PredInfo) then search_excp_analysis_status(PPId, ExceptionStatus, AnalysisStatus, !ModuleInfo), MaybeAnalysisStatus = yes(AnalysisStatus) else proc_info_get_exception_info(ProcInfo, MaybeExceptionInfo), ( MaybeExceptionInfo = yes(ProcExceptionInfo), ProcExceptionInfo = proc_exception_info(ExceptionStatus, MaybeAnalysisStatus) ; MaybeExceptionInfo = no, ExceptionStatus = may_throw(user_exception), MaybeAnalysisStatus = maybe_optimal(IntermodAnalysis) ) ), ( !.MaybeWillNotThrow = may_throw ; !.MaybeWillNotThrow = maybe_will_not_throw(Conditionals), ( ExceptionStatus = throw_conditional, !:MaybeWillNotThrow = maybe_will_not_throw([PPId | Conditionals]) ; ExceptionStatus = will_not_throw ; ExceptionStatus = may_throw(_), !:MaybeWillNotThrow = may_throw ) ), combine_maybe_analysis_status(MaybeAnalysisStatus, !AS). %----------------------------------------------------------------------------% :- pred update_excp_proc_result(exception_status::in, maybe(analysis_status)::in, excp_proc_result::in, excp_proc_result::out) is det. update_excp_proc_result(CurrentStatus, CurrentAnalysisStatus, !Result) :- OldStatus = !.Result ^ epr_status, OldAnalysisStatus = !.Result ^ epr_maybe_analysis_status, NewStatus = combine_exception_status(CurrentStatus, OldStatus), combine_maybe_analysis_status(CurrentAnalysisStatus, OldAnalysisStatus, NewAnalysisStatus), !Result ^ epr_status := NewStatus, !Result ^ epr_maybe_analysis_status := NewAnalysisStatus. :- func combine_exception_status(exception_status, exception_status) = exception_status. combine_exception_status(will_not_throw, Y) = Y. combine_exception_status(X @ may_throw(user_exception), _) = X. combine_exception_status(X @ may_throw(type_exception), will_not_throw) = X. combine_exception_status(X @ may_throw(type_exception), throw_conditional) = X. combine_exception_status(may_throw(type_exception), Y @ may_throw(_)) = Y. combine_exception_status(throw_conditional, throw_conditional) = throw_conditional. combine_exception_status(throw_conditional, will_not_throw) = throw_conditional. combine_exception_status(throw_conditional, Y @ may_throw(_)) = Y. :- pred combine_maybe_analysis_status(maybe(analysis_status)::in, maybe(analysis_status)::in, maybe(analysis_status)::out) is det. combine_maybe_analysis_status(MaybeStatusA, MaybeStatusB, MaybeStatus) :- ( if MaybeStatusA = yes(StatusA), MaybeStatusB = yes(StatusB) then MaybeStatus = yes(analysis.lub(StatusA, StatusB)) else MaybeStatus = no ). %----------------------------------------------------------------------------% % % Extra procedures for handling calls. % :- pred excp_check_nonrecursive_call(vartypes::in, pred_proc_id::in, prog_vars::in, pred_info::in, excp_proc_result::in, excp_proc_result::out, module_info::in, module_info::out) is det. excp_check_nonrecursive_call(VarTypes, PPId, Args, PredInfo, !Result, !ModuleInfo) :- module_info_get_globals(!.ModuleInfo, Globals), globals.lookup_bool_option(Globals, intermodule_analysis, IntermodAnalysis), ( if % If we are using `--intermodule-analysis' then use the analysis % framework for imported procedures. IntermodAnalysis = yes, pred_info_is_imported_not_external(PredInfo) then search_excp_analysis_status(PPId, CalleeResult, AnalysisStatus, !ModuleInfo), MaybeAnalysisStatus = yes(AnalysisStatus), update_excp_proc_result(CalleeResult, MaybeAnalysisStatus, !Result) else PPId = proc(_, ProcId), pred_info_proc_info(PredInfo, ProcId, ProcInfo), proc_info_get_exception_info(ProcInfo, MaybeCalleeExceptionInfo), ( MaybeCalleeExceptionInfo = yes(CalleeExceptionInfo), CalleeExceptionInfo = proc_exception_info(CalleeExceptionStatus, MaybeAnalysisStatus), ( CalleeExceptionStatus = will_not_throw, update_excp_proc_result(will_not_throw, MaybeAnalysisStatus, !Result) ; CalleeExceptionStatus = may_throw(ExceptionType), update_excp_proc_result(may_throw(ExceptionType), MaybeAnalysisStatus, !Result) ; CalleeExceptionStatus = throw_conditional, excp_check_vars(!.ModuleInfo, VarTypes, Args, MaybeAnalysisStatus, !Result) ) ; MaybeCalleeExceptionInfo = no, % If we do not have any information about the callee procedure % then assume that it might throw an exception. % Analysis statuses on individual results are meaningless now. MaybeAnalysisStatus = maybe_optimal(IntermodAnalysis), update_excp_proc_result(may_throw(user_exception), MaybeAnalysisStatus, !Result) ) ). :- pred excp_check_vars(module_info::in, vartypes::in, prog_vars::in, maybe(analysis_status)::in, excp_proc_result::in, excp_proc_result::out) is det. excp_check_vars(ModuleInfo, VarTypes, Vars, MaybeAnalysisStatus, !Result) :- lookup_var_types(VarTypes, Vars, Types), TypeStatus = excp_check_types(ModuleInfo, Types), ( TypeStatus = type_will_not_throw ; TypeStatus = type_may_throw, update_excp_proc_result(may_throw(type_exception), MaybeAnalysisStatus, !Result) ; TypeStatus = type_conditional, update_excp_proc_result(throw_conditional, MaybeAnalysisStatus, !Result) ). %----------------------------------------------------------------------------% % % Predicates for checking mixed SCCs. % % A "mixed SCC" is one where at least one of the procedures in the SCC is % known not to throw an exception, at least one of them is conditional and % none of them may throw an exception (of either sort). % % In order to determine the status of such a SCC, we also need to take the % effect of the recursive calls into account. This is because calls to a % conditional procedure from a procedure that is mutually recursive to it may % introduce types that could cause a type_exception to be thrown. % % We currently assume that if these types are introduced somewhere in the SCC % then they may be propagated around the entire SCC - hence if a part of the % SCC is conditional we need to make sure other parts don't supply it with % input whose types may have user-defined equality/comparison predicates. % NOTE: it is possible to write rather contrived programs that can exhibit % rather strange behaviour which is why all this is necessary. :- func handle_mixed_conditional_scc(list(excp_proc_result)) = exception_status. handle_mixed_conditional_scc(Results) = ( if all [TypeStatus] ( list.member(Result, Results) => Result ^ epr_rec_calls \= type_may_throw ) then throw_conditional else % Somewhere a type that causes an exception is being passed around % the SCC via one or more of the recursive calls. may_throw(type_exception) ). %----------------------------------------------------------------------------% % % Stuff for processing types. % % This is used in the analysis of calls to polymorphic procedures. % % By saying a `type can throw an exception' we mean that an exception might be % thrown as a result of a unification or comparison involving the type because % it has a user-defined equality/comparison predicate that may throw an % exception. % % XXX We don't actually need to examine all the types, just those that are % potentially going to be involved in unification/comparisons. At the moment % we don't keep track of that information so the current procedure is as % follows: % % Examine the functor and then recursively examine the arguments. % * If everything will not throw then the type will not throw % * If at least one of the types may_throw then the type will throw % * If at least one of the types is conditional and none of them throw then % the type is conditional. :- type type_excp_status ---> type_will_not_throw % This type does not have user-defined equality % or comparison predicates. % XXX (Or it has ones that are known not to throw exceptions). ; type_may_throw % This type has a user-defined equality or comparison predicate % that is known to throw an exception. ; type_conditional. % This type is polymorphic. We cannot say anything about it % until we know the values of the type-variables. % Return the collective type status of a list of types. % :- func excp_check_types(module_info, list(mer_type)) = type_excp_status. excp_check_types(ModuleInfo, Types) = Status :- list.foldl(excp_check_type(ModuleInfo), Types, type_will_not_throw, Status). :- pred excp_check_type(module_info::in, mer_type::in, type_excp_status::in, type_excp_status::out) is det. excp_check_type(ModuleInfo, Type, !Status) :- excp_combine_type_status(excp_check_type(ModuleInfo, Type), !Status). :- pred excp_combine_type_status(type_excp_status::in, type_excp_status::in, type_excp_status::out) is det. excp_combine_type_status(type_will_not_throw, type_will_not_throw, type_will_not_throw). excp_combine_type_status(type_will_not_throw, type_conditional, type_conditional). excp_combine_type_status(type_will_not_throw, type_may_throw, type_may_throw). excp_combine_type_status(type_conditional, type_will_not_throw, type_conditional). excp_combine_type_status(type_conditional, type_conditional, type_conditional). excp_combine_type_status(type_conditional, type_may_throw, type_may_throw). excp_combine_type_status(type_may_throw, _, type_may_throw). % Return the type status of an individual type. % :- func excp_check_type(module_info, mer_type) = type_excp_status. excp_check_type(ModuleInfo, Type) = Status :- ( if ( type_is_solver_type(ModuleInfo, Type) ; type_is_existq_type(ModuleInfo, Type) ) then % XXX At the moment we just assume that existential types and % solver types result in a type exception being thrown. Status = type_may_throw else TypeCategory = classify_type(ModuleInfo, Type), Status = excp_check_type_2(ModuleInfo, Type, TypeCategory) ). :- func excp_check_type_2(module_info, mer_type, type_ctor_category) = type_excp_status. excp_check_type_2(ModuleInfo, Type, CtorCat) = WillThrow :- ( ( CtorCat = ctor_cat_builtin(_) ; CtorCat = ctor_cat_higher_order ; CtorCat = ctor_cat_system(_) ; CtorCat = ctor_cat_void ; CtorCat = ctor_cat_builtin_dummy ), WillThrow = type_will_not_throw ; CtorCat = ctor_cat_variable, WillThrow = type_conditional ; CtorCat = ctor_cat_tuple, type_to_ctor_and_args_det(Type, _TypeCtor, Args), WillThrow = excp_check_types(ModuleInfo, Args) ; CtorCat = ctor_cat_enum(_), ( if type_has_user_defined_equality_pred(ModuleInfo, Type, _UC) then % XXX This is very conservative. WillThrow = type_may_throw else WillThrow = type_will_not_throw ) ; CtorCat = ctor_cat_user(_), type_to_ctor_and_args_det(Type, TypeCtor, Args), ( if type_has_user_defined_equality_pred(ModuleInfo, Type, _UC) then % XXX We can do better than this by examining what these preds % actually do. Something similar needs to be sorted out for % termination analysis as well, so we'll wait until that is done. WillThrow = type_may_throw else if excp_type_ctor_is_safe(TypeCtor) then WillThrow = excp_check_types(ModuleInfo, Args) else WillThrow = type_may_throw ) ). % Succeeds if the exception status of the type represented by the given % type_ctor can be determined by examining the exception status of the % arguments, if any. % % NOTE: This list does not need to include enumerations since they are % already handled above. Also, this list does not need to include % non-abstract equivalence types. % :- pred excp_type_ctor_is_safe(type_ctor::in) is semidet. excp_type_ctor_is_safe(TypeCtor) :- TypeCtor = type_ctor(qualified(unqualified(ModuleName), CtorName), Arity), excp_type_ctor_is_safe_2(ModuleName, CtorName, Arity). :- pred excp_type_ctor_is_safe_2(string::in, string::in, arity::in) is semidet. excp_type_ctor_is_safe_2("assoc_list", "assoc_list", 1). excp_type_ctor_is_safe_2("bag", "bag", 1). excp_type_ctor_is_safe_2("bimap", "bimap", 2). excp_type_ctor_is_safe_2("builtin", "c_pointer", 0). excp_type_ctor_is_safe_2("cord", "cord", 1). excp_type_ctor_is_safe_2("eqvclass", "eqvclass", 1). excp_type_ctor_is_safe_2("injection", "injection", 2). excp_type_ctor_is_safe_2("integer", "integer", 0). excp_type_ctor_is_safe_2("io", "input_stream", 0). excp_type_ctor_is_safe_2("io", "output_stream", 0). excp_type_ctor_is_safe_2("io", "binary_stream", 0). excp_type_ctor_is_safe_2("io", "stream_id", 0). excp_type_ctor_is_safe_2("io", "res", 0). excp_type_ctor_is_safe_2("io", "res", 1). excp_type_ctor_is_safe_2("io", "maybe_partial_res", 1). excp_type_ctor_is_safe_2("io", "result", 0). excp_type_ctor_is_safe_2("io", "result", 1). excp_type_ctor_is_safe_2("io", "read_result", 1). excp_type_ctor_is_safe_2("io", "error", 0). excp_type_ctor_is_safe_2("list", "list", 1). excp_type_ctor_is_safe_2("map", "map", 2). excp_type_ctor_is_safe_2("maybe", "maybe", 1). excp_type_ctor_is_safe_2("maybe_error", "maybe_error", 1). excp_type_ctor_is_safe_2("multi_map", "multi_map", 2). excp_type_ctor_is_safe_2("pair", "pair", 2). excp_type_ctor_is_safe_2("pqueue", "pqueue", 2). excp_type_ctor_is_safe_2("queue", "queue", 1). excp_type_ctor_is_safe_2("rational", "rational", 0). excp_type_ctor_is_safe_2("rbtree", "rbtree", 2). excp_type_ctor_is_safe_2("rtree", "rtree", 2). excp_type_ctor_is_safe_2("set", "set", 1). excp_type_ctor_is_safe_2("set_bbbtree", "set_bbbtree", 1). excp_type_ctor_is_safe_2("set_ctree234", "set_ctree234", 1). excp_type_ctor_is_safe_2("set_ordlist", "set_ordlist", 1). excp_type_ctor_is_safe_2("set_tree234", "set_tree234", 1). excp_type_ctor_is_safe_2("set_unordlist", "set_unordlist", 1). excp_type_ctor_is_safe_2("stack", "stack", 1). excp_type_ctor_is_safe_2("string", "poly_type", 0). excp_type_ctor_is_safe_2("string", "justified_column", 0). excp_type_ctor_is_safe_2("term", "term", 1). excp_type_ctor_is_safe_2("term", "const", 0). excp_type_ctor_is_safe_2("term", "context", 0). excp_type_ctor_is_safe_2("term", "var", 1). excp_type_ctor_is_safe_2("term", "var_supply", 1). excp_type_ctor_is_safe_2("varset", "varset", 1). %----------------------------------------------------------------------------% % % Types and instances for the intermodule analysis framework. % :- type exception_analysis_answer ---> exception_analysis_answer(exception_status). :- func excp_analysis_name = string. excp_analysis_name = "exception_analysis". :- instance analysis(no_func_info, any_call, exception_analysis_answer) where [ analysis_name(_, _) = excp_analysis_name, analysis_version_number(_, _) = 1, preferred_fixpoint_type(_, _) = least_fixpoint, bottom(_, _) = exception_analysis_answer(will_not_throw), top(_, _) = exception_analysis_answer(may_throw(user_exception)), get_func_info(_, _, _, _, _, no_func_info) ]. :- instance answer_pattern(no_func_info, exception_analysis_answer) where []. :- instance partial_order(no_func_info, exception_analysis_answer) where [ ( more_precise_than(no_func_info, Answer1, Answer2) :- Answer1 = exception_analysis_answer(Status1), Answer2 = exception_analysis_answer(Status2), exception_status_more_precise_than(Status1, Status2) ), equivalent(no_func_info, Status, Status) ]. :- pred exception_status_more_precise_than(exception_status::in, exception_status::in) is semidet. exception_status_more_precise_than(StatusA, StatusB) :- require_complete_switch [StatusA] ( StatusA = will_not_throw, require_complete_switch [StatusB] ( StatusB = will_not_throw, AMorePreciseThanB = no ; ( StatusB = throw_conditional ; StatusB = may_throw(_) ), AMorePreciseThanB = yes ), AMorePreciseThanB = yes ; StatusA = throw_conditional, require_complete_switch [StatusB] ( ( StatusB = will_not_throw ; StatusB = throw_conditional ), AMorePreciseThanB = no ; StatusB = may_throw(_), AMorePreciseThanB = yes ), AMorePreciseThanB = yes ; StatusA = may_throw(ExceptionTypeA), require_complete_switch [StatusB] ( ( StatusB = will_not_throw ; StatusB = throw_conditional ), AMorePreciseThanB = no ; StatusB = may_throw(ExceptionTypeB), ( ExceptionTypeA = type_exception, ( ExceptionTypeB = type_exception, AMorePreciseThanB = no ; ExceptionTypeB = user_exception, AMorePreciseThanB = yes ) ; ExceptionTypeA = user_exception, AMorePreciseThanB = no ) ), AMorePreciseThanB = yes ). :- instance to_term(exception_analysis_answer) where [ func(to_term/1) is excp_answer_to_term, pred(from_term/2) is excp_answer_from_term ]. :- func excp_answer_to_term(exception_analysis_answer) = term. excp_answer_to_term(Answer) = Term :- Answer = exception_analysis_answer(Status), exception_status_to_string(Status, String), Term = term.functor(atom(String), [], context_init). :- pred excp_answer_from_term(term::in, exception_analysis_answer::out) is semidet. excp_answer_from_term(Term, exception_analysis_answer(Status)) :- Term = term.functor(atom(String), [], _), exception_status_to_string(Status, String). :- pred exception_status_to_string(exception_status, string). :- mode exception_status_to_string(in, out) is det. :- mode exception_status_to_string(out, in) is semidet. exception_status_to_string(will_not_throw, "will_not_throw"). exception_status_to_string(throw_conditional, "conditional"). exception_status_to_string(may_throw(type_exception), "may_throw_type_exception"). exception_status_to_string(may_throw(user_exception), "may_throw_user_exception"). %----------------------------------------------------------------------------% % % Additional predicates used for intermodule analysis. % :- pred search_excp_analysis_status(pred_proc_id::in, exception_status::out, analysis_status::out, module_info::in, module_info::out) is det. search_excp_analysis_status(PPId, Result, AnalysisStatus, !ModuleInfo) :- module_info_get_analysis_info(!.ModuleInfo, AnalysisInfo0), search_excp_analysis_status_2(!.ModuleInfo, PPId, Result, AnalysisStatus, AnalysisInfo0, AnalysisInfo), module_info_set_analysis_info(AnalysisInfo, !ModuleInfo). :- pred search_excp_analysis_status_2(module_info::in, pred_proc_id::in, exception_status::out, analysis_status::out, analysis_info::in, analysis_info::out) is det. search_excp_analysis_status_2(ModuleInfo, PPId, Result, AnalysisStatus, !AnalysisInfo) :- module_name_func_id(ModuleInfo, PPId, ModuleName, FuncId), Call = any_call, lookup_best_result(!.AnalysisInfo, ModuleName, FuncId, no_func_info, Call, MaybeBestResult), ( MaybeBestResult = yes(analysis_result(BestCall, BestAnswer, AnalysisStatus)), BestAnswer = exception_analysis_answer(Result), record_dependency(ModuleName, FuncId, no_func_info, BestCall, _ : exception_analysis_answer, !AnalysisInfo) ; MaybeBestResult = no, % If we do not have any information about the callee procedure then % assume that it throws an exception. top(no_func_info, Call) = Answer, Answer = exception_analysis_answer(Result), AnalysisStatus = optimal, record_request(excp_analysis_name, ModuleName, FuncId, Call, !AnalysisInfo) ). :- pred maybe_record_exception_result(module_info::in, pred_id::in, analysis_info::in, analysis_info::out) is det. maybe_record_exception_result(ModuleInfo, PredId, !AnalysisInfo) :- module_info_pred_info(ModuleInfo, PredId, PredInfo), ProcIds = pred_info_procids(PredInfo), list.foldl(maybe_record_exception_result_2(ModuleInfo, PredId, PredInfo), ProcIds, !AnalysisInfo). :- pred maybe_record_exception_result_2(module_info::in, pred_id::in, pred_info::in, proc_id::in, analysis_info::in, analysis_info::out) is det. maybe_record_exception_result_2(ModuleInfo, PredId, PredInfo, ProcId, !AnalysisInfo) :- should_write_exception_info(ModuleInfo, PredId, ProcId, PredInfo, for_analysis_framework, ShouldWrite), ( ShouldWrite = should_write, PPId = proc(PredId, ProcId), lookup_proc_exception_info(ModuleInfo, PPId, Status, ResultStatus), module_name_func_id(ModuleInfo, PPId, ModuleName, FuncId), record_result(ModuleName, FuncId, any_call, exception_analysis_answer(Status), ResultStatus, !AnalysisInfo) ; ShouldWrite = should_not_write ). :- pred lookup_proc_exception_info(module_info::in, pred_proc_id::in, exception_status::out, analysis_status::out) is det. lookup_proc_exception_info(ModuleName, PPId, Status, ResultStatus) :- module_info_pred_proc_info(ModuleName, PPId, _PredInfo, ProcInfo), proc_info_get_exception_info(ProcInfo, MaybeExceptionInfo), ( MaybeExceptionInfo = yes(ProcExceptionInfo), ProcExceptionInfo = proc_exception_info(Status, MaybeResultStatus), ( MaybeResultStatus = yes(ResultStatus) ; MaybeResultStatus = no, unexpected($module, $pred, "no result status") ) ; MaybeExceptionInfo = no, % Probably an exported `:- pragma external_{pred/func}' procedure. Status = may_throw(user_exception), ResultStatus = optimal ). :- func maybe_optimal(bool) = maybe(analysis_status). maybe_optimal(no) = no. maybe_optimal(yes) = yes(optimal). %----------------------------------------------------------------------------% % % External interface to exception analysis information. % lookup_exception_analysis_result(PPId, ExceptionStatus, !ModuleInfo) :- PPId = proc(PredId, ProcId), module_info_pred_proc_info(!.ModuleInfo, PredId, ProcId, PredInfo, ProcInfo), IsImported = pred_to_bool(pred_info_is_imported_not_external(PredInfo)), module_info_get_globals(!.ModuleInfo, Globals), globals.lookup_bool_option(Globals, intermodule_analysis, IntermodAnalysis), globals.lookup_bool_option(Globals, analyse_exceptions, ExceptionAnalysis), % If we the procedure we are calling is imported and we are using % intermodule-analysis then we need to look up the exception status in the % analysis registry; otherwise we look it up in the exception_info table. UseAnalysisRegistry = IsImported `bool.and` IntermodAnalysis `bool.and` ExceptionAnalysis, ( % If the procedure is not imported then its exception_status % will be in the exception_info table. UseAnalysisRegistry = no, proc_info_get_exception_info(ProcInfo, MaybeProcExceptionInfo), ( MaybeProcExceptionInfo = yes(ProcExceptionInfo), ProcExceptionInfo = proc_exception_info(ExceptionStatus, _) ; MaybeProcExceptionInfo = no, ExceptionStatus = may_throw(user_exception) ) ; UseAnalysisRegistry = yes, some [!AnalysisInfo] ( module_info_get_analysis_info(!.ModuleInfo, !:AnalysisInfo), module_name_func_id(!.ModuleInfo, PPId, ModuleName, FuncId), lookup_best_result(!.AnalysisInfo, ModuleName, FuncId, no_func_info, any_call, MaybeBestResult), ( MaybeBestResult = yes(BestResult), BestResult = analysis_result(_Call, Answer, AnalysisStatus), ( AnalysisStatus = invalid, unexpected($module, $pred, "invalid exception_analysis answer") ; ( AnalysisStatus = optimal ; AnalysisStatus = suboptimal ), Answer = exception_analysis_answer(ExceptionStatus) ) ; MaybeBestResult = no, ExceptionStatus = may_throw(user_exception) ), record_dependency(ModuleName, FuncId, no_func_info, any_call, _ : exception_analysis_answer, !AnalysisInfo), module_info_set_analysis_info(!.AnalysisInfo, !ModuleInfo) ) ). %----------------------------------------------------------------------------% :- end_module transform_hlds.exception_analysis. %----------------------------------------------------------------------------%