%-----------------------------------------------------------------------------% % vim: ft=mercury ts=4 sw=4 et %-----------------------------------------------------------------------------% % Copyright (C) 2000-2005 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: unneeded_code.m. % Author: zs. % This module implements two related source-to-source transforms, % both of which focus on goals that produce some variables, where these % variables are not always required by the following computation. % % If there are no computation paths on which the variables produced by a goal % may be needed, then the first transform deletes that goal. % % If the variables produced by a goal may be needed on some but not all % computation paths, then the second transform moves that goal to the starts % of those computation paths, thus avoiding the cost of executing the goal % on all other computation paths. (This is related to the concept of partial % redundancy elimination (PRE) for imperative languages.) % % Mercury has two constructs that make it possible for a variable to be needed % on some computation paths but not others: switches and if-then-elses. % % In the case of switches, the alternative computation paths are those % corresponding to the possible values of the switched-on variable, and % not just the switch arms. Even if all switch arms need a variable, it % is an optimization to copy the code generating that variable to the starts of % all the switch arms if the switch is can_fail, i.e. there are some function % symbols that the switched-on variable can be bound to that do not have arms. % % In the case of if-then-elses, the alternatives are the then part and % the else part. Any variable needed by the condition is needed in both those % computation paths. % % From the point of view of this transform, disjunctions are not branched % control structures, because entering a disjunct does not preclude later % entering another disjunct. Any variable needed by any disjunct must therefore % be produced before control enters the disjunction. (In theory, a disjunct % that cannot fail in a model_semi disjunction prevents entry to the following % disjuncts, but any such following disjuncts will have been removed long ago % by simplification.) % % Note that by avoiding the execution of a goal that appears in the original % source code of the program, both these transforms can in general change the % operational semantics of the program. Therefore a goal can only be eliminated % or moved if the goal is has no observable effect except the result it % generates (i.e is pure, cannot fail, cannot loop, cannot raise an exception), % which is usually true only of goals composed entirely of builtins, or if % the semantics options explicitly permit the change in the operational % semantics, which will usually be an improvement (e.g. avoiding an infinite % loop or an unnecessary exception). %-----------------------------------------------------------------------------% :- module transform_hlds__unneeded_code. :- interface. :- import_module hlds.hlds_module. :- import_module hlds.hlds_pred. :- import_module io. %-----------------------------------------------------------------------------% :- pred process_proc_msg(pred_id::in, proc_id::in, proc_info::in, proc_info::out, module_info::in, module_info::out, io::di, io::uo) is det. %-----------------------------------------------------------------------------% %-----------------------------------------------------------------------------% :- implementation. :- import_module check_hlds.goal_path. :- import_module check_hlds.inst_match. :- import_module check_hlds.mode_util. :- import_module hlds.goal_form. :- import_module hlds.hlds_goal. :- import_module hlds.hlds_out. :- import_module hlds.instmap. :- import_module hlds.passes_aux. :- import_module hlds.quantification. :- import_module libs.compiler_util. :- import_module libs.globals. :- import_module libs.options. :- import_module parse_tree.prog_data. :- import_module assoc_list. :- import_module bool. :- import_module int. :- import_module list. :- import_module map. :- import_module set. :- import_module std_util. :- import_module svmap. %-----------------------------------------------------------------------------% % The branch_alts and branch_point types record the information the % transform needs to know about a particular branched control % structure: where it is, what kind it is, and how many alternatives % it has. % :- type branch_point ---> branch_point( goal_path, % The position of the branch point. branch_alts % What kind of goal the branch point % is, and many branches it has. % Note that the second argument is a % function of the first. ). :- type branch_alts ---> ite % If-then-elses always have two alternatives: % the then branch (numbered 1) and the else branch % (numbered 2). ; switch(int). % The number of alternatives in a switch is equal % to the number of function symbols in the type of % the switched-on variable; this number is given by % the argument. If the switch cannot_fail, then % this will be equal to the number of cases; if % the switch can_fail, there will be strictly % fewer cases than this. % The location type identifies one arm of a branched control structure. % The branched control structure id is a branch_point instead of a % simple goal_path because without the branch_alts info, the % transformation cannot tell if a given set of branches of a branched % control structure covers all possible execution paths or not. % :- type location ---> location( branch_point, % To which branched control structure % does the location belong. int % The branch within that control structure. ). % The where_needed_map type maps each variable to the set of % computation branches where it is needed. If a variable is needed % everywhere, then the computation producing it cannot be eliminated % or moved. If it is not needed at all, its producer can be eliminated. % If it is needed on some but not all branches, then the producer % can be moved to the starts of those branches. % % The set of branches to whose starts the producer can be moved % is represented as a map from the id of the branched control % structure to the set of branch numbers within that branched control % structure. If the branched control structure at goal path gp is % mapped to a set including N, then the producer of that variable % may be moved to the start of the goal with goal path ;sN; % (if the control structure is a switch) or ;t; or ;e; % (if the control structure is an if-then-else). % % Since ;sN; is conjoined with e.g. ;sN;;sM; % it would be a mode error (variable having two conjoined producers) % for the transformed code to have the producer of some variable % inserted at the start of both those goals. It is therefore an % invariant that a where_needed structure mapping gp to N % will not contain any keys whose goal_path includes ;sN; % or its if-then-else equivalent. % % An example: % % % switch on X at goal path gp % ( % s1 % X = a, % ... code that needs Y and Z ... % ; % s2 % X = b, % ( Y = f -> % ... code that needs only Z ... % ; % ... code that does not need Y or Z ... % ) % ) % % X is needed everywhere, since even if X is bound to c, its value must % be tested. % % Y is needed everywhere iff the type of X contains only a and b, % otherwise it is needed only in the ;s1; and ;s2; switch arms. % % Z is needed in ;s1; and ;s2;t; but is not needed in the % ;s2;e; else arm. Therefore the where_needed_branches map for Z % will map gp to 1 and ;s2; to 1. % :- type where_needed_map == map(prog_var, where_needed). :- type where_needed ---> everywhere ; branches(where_needed_branches). :- type where_needed_branches == map(branch_point, set(int)). % The refined_goal_map structure maps branch goals to the list of % producers that should be moved to the start of that branch. % The order is important, since some of the producers in such a list % may depend on variables produced by other goals that precede them % in the list. :- type refined_goal_map == map(pair(goal_path, int), list(hlds_goal)). %-----------------------------------------------------------------------------% process_proc_msg(PredId, ProcId, !ProcInfo, !ModuleInfo, !IO) :- % The transformation considers every nonlocal variable of a goal % that is bound on entry to be consumed by that goal. If the nonlocal set % contains any such variables that are not actually needed by the goal, % then the transformation will not be as effective as it could be. % Therefore we preprocess the procedure body to ensure that the nonlocals % sets are accurate reflections of the true needs of goals. globals__io_lookup_bool_option(very_verbose, VeryVerbose, !IO), ( VeryVerbose = yes, io__write_string("% Removing dead code in ", !IO), hlds_out__write_pred_proc_id(!.ModuleInfo, PredId, ProcId, !IO), io__write_string(": ", !IO), pre_process_proc(!ProcInfo), process_proc(!ProcInfo, !ModuleInfo, Successful), ( Successful = yes, io__write_string("done.\n", !IO) ; Successful = no, io__write_string("none found.\n", !IO) ) ; VeryVerbose = no, pre_process_proc(!ProcInfo), process_proc(!ProcInfo, !ModuleInfo, _) ). :- pred pre_process_proc(proc_info::in, proc_info::out) is det. pre_process_proc(!ProcInfo) :- proc_info_headvars(!.ProcInfo, HeadVars), proc_info_goal(!.ProcInfo, Goal0), proc_info_varset(!.ProcInfo, Varset0), proc_info_vartypes(!.ProcInfo, VarTypes0), implicitly_quantify_clause_body(HeadVars, _Warnings, Goal0, Goal, Varset0, Varset, VarTypes0, VarTypes), proc_info_set_goal(Goal, !ProcInfo), proc_info_set_varset(Varset, !ProcInfo), proc_info_set_vartypes(VarTypes, !ProcInfo). % The source-to-source transform operates in two phases. % % The first phase traverses the procedure body, keeping track of which % variables are needed where. When it finds a goal that can be deleted, % it deletes it by replacing it with the goal `true' (i.e. conj([])). % When it finds a goal that can be moved, it does the same, but also % records in the RefinedGoalsMap that the deleted goal must later be % inserted at the starts of the branches where its outputs may be needed, % and accordingly notes that its own inputs are needed in those branches. % % The second phase traverses the modified problem body, and inserts the % goals in the RefinedGoalsMap at the starts of the indicated branches. % This phase identified the indicated branches by the goal_path annotations % on their parents. These may be out of date since the first phase will have % deleted some goals, but since neither phase modifies the goal_path annotation % on a goal once that goal has been inserted into the RefinedGoalsMap, % this does not matter. % % Neither phase traverses the internals of a goal that has been moved. % To make sure that such goals are optimized whenever possible, the algorithm % invokes itself recursively whenever it was able to successfully (delete or) % move a goal. This cannot lead to infinite recursion, since each iteration % will strictly reduce the number of computation paths on which a subgoal % of the procedure body is executed. Since both the number of subgoals and % computation paths are finite, the recursion must end. :- type option_values ---> option_values( fully_strict :: bool, reorder_conj :: bool, copy_limit :: int ). :- pred process_proc(proc_info::in, proc_info::out, module_info::in, module_info::out, bool::out) is det. process_proc(!ProcInfo, !ModuleInfo, Successful) :- goal_path__fill_slots(!.ModuleInfo, !ProcInfo), proc_info_goal(!.ProcInfo, Goal0), proc_info_varset(!.ProcInfo, Varset0), proc_info_vartypes(!.ProcInfo, VarTypes0), proc_info_get_initial_instmap(!.ProcInfo, !.ModuleInfo, InitInstMap), Goal0 = _ - GoalInfo0, goal_info_get_instmap_delta(GoalInfo0, InstMapDelta), instmap__apply_instmap_delta(InitInstMap, InstMapDelta, FinalInstMap), proc_info_instantiated_head_vars(!.ModuleInfo, !.ProcInfo, NeededVarsList), map__init(WhereNeededMap0), NeededEverywhere = (pred(Var::in, NeededMap0::in, NeededMap::out) is det :- map__det_insert(NeededMap0, Var, everywhere, NeededMap) ), list__foldl(NeededEverywhere, NeededVarsList, WhereNeededMap0, WhereNeededMap1), module_info_get_globals(!.ModuleInfo, Globals), globals__lookup_bool_option(Globals, reorder_conj, ReorderConj), globals__lookup_bool_option(Globals, fully_strict, FullyStrict), globals__lookup_int_option(Globals, unneeded_code_copy_limit, Limit), Options = option_values(FullyStrict, ReorderConj, Limit), process_goal(Goal0, Goal1, InitInstMap, FinalInstMap, VarTypes0, !.ModuleInfo, Options, WhereNeededMap1, _, map__init, RefinedGoals1, no, Changed), refine_goal(Goal1, Goal2, RefinedGoals1, RefinedGoals), expect(map__is_empty(RefinedGoals), this_file, "process_proc: goal reattachment unsuccessful"), ( Changed = yes, % We need to fix up the goal_info by recalculating % the nonlocal vars and the non-atomic instmap deltas. proc_info_headvars(!.ProcInfo, HeadVars), proc_info_inst_varset(!.ProcInfo, InstVarSet), implicitly_quantify_clause_body(HeadVars, _Warnings, Goal2, Goal3, Varset0, Varset, VarTypes0, VarTypes), recompute_instmap_delta(no, Goal3, Goal, VarTypes, InstVarSet, InitInstMap, !ModuleInfo), proc_info_set_goal(Goal, !ProcInfo), proc_info_set_varset(Varset, !ProcInfo), proc_info_set_vartypes(VarTypes, !ProcInfo), process_proc(!ProcInfo, !ModuleInfo, _), Successful = yes ; Changed = no, Successful = no ). :- pred process_goal(hlds_goal::in, hlds_goal::out, instmap::in, instmap::in, vartypes::in, module_info::in, option_values::in, where_needed_map::in, where_needed_map::out, refined_goal_map::in, refined_goal_map::out, bool::in, bool::out) is det. process_goal(Goal0, Goal, InitInstMap, FinalInstMap, VarTypes, ModuleInfo, Options, !WhereNeededMap, !RefinedGoals, !Changed) :- can_eliminate_or_move(Goal0, InitInstMap, FinalInstMap, VarTypes, ModuleInfo, Options, !.WhereNeededMap, WhereInfo), ( WhereInfo = everywhere, process_goal_internal(Goal0, Goal, InitInstMap, FinalInstMap, VarTypes, ModuleInfo, Options, !WhereNeededMap, !RefinedGoals, !Changed) ; WhereInfo = branches(Branches), demand_inputs(Goal0, ModuleInfo, InitInstMap, WhereInfo, !WhereNeededMap), map__to_assoc_list(Branches, BranchList), list__foldl(insert_branch_into_refined_goals(Goal0), BranchList, !RefinedGoals), true_goal(Goal), !:Changed = yes ), undemand_virgin_outputs(Goal0, ModuleInfo, InitInstMap, !WhereNeededMap), ( Goal = _ - GoalInfo, goal_info_get_features(GoalInfo, Features), set__member(impure_goal, Features) -> % By saying that all vars that are live before the impure goal are % needed everywhere, we prevent the movement of the goals producing % those vars across the impure goal. % % This code requires compound goals containing impure code % to also be marked impure. map__map_values(demand_var_everywhere, !WhereNeededMap) ; true ). :- pred insert_branch_into_refined_goals(hlds_goal::in, pair(branch_point, set(int))::in, refined_goal_map::in, refined_goal_map::out) is det. insert_branch_into_refined_goals(Goal, BranchPoint - BranchNumSet, !RefinedGoals) :- BranchPoint = branch_point(GoalPath, _), set__to_sorted_list(BranchNumSet, BranchNums), list__foldl(insert_branch_arm_into_refined_goals(Goal, GoalPath), BranchNums, !RefinedGoals). :- pred insert_branch_arm_into_refined_goals(hlds_goal::in, goal_path::in, int::in, refined_goal_map::in, refined_goal_map::out) is det. insert_branch_arm_into_refined_goals(Goal, GoalPath, BranchNum, !RefinedGoals) :- Key = GoalPath - BranchNum, ( map__search(!.RefinedGoals, Key, Goals0) -> Goals = [Goal | Goals0], map__det_update(!.RefinedGoals, Key, Goals, !:RefinedGoals) ; map__det_insert(!.RefinedGoals, Key, [Goal], !:RefinedGoals) ). %-----------------------------------------------------------------------------% :- pred can_eliminate_or_move(hlds_goal::in, instmap::in, instmap::in, vartypes::in, module_info::in, option_values::in, where_needed_map::in, where_needed::out) is det. can_eliminate_or_move(Goal, InitInstMap, FinalInstMap, VarTypes, ModuleInfo, Options, WhereNeededMap, !:WhereInfo) :- instmap_changed_vars(InitInstMap, FinalInstMap, VarTypes, ModuleInfo, ChangedVarSet), set__to_sorted_list(ChangedVarSet, ChangedVars), map__init(Empty), !:WhereInfo = branches(Empty), Goal = _ - GoalInfo, goal_info_get_goal_path(GoalInfo, CurrentPath), list__foldl(collect_where_needed(CurrentPath, WhereNeededMap), ChangedVars, !WhereInfo), adjust_where_needed(Goal, Options, !WhereInfo). :- pred collect_where_needed(goal_path::in, where_needed_map::in, prog_var::in, where_needed::in, where_needed::out) is det. collect_where_needed(CurrentPath, WhereNeededMap, ChangedVar, !WhereInfo) :- ( map__search(WhereNeededMap, ChangedVar, Where) -> where_needed_upper_bound(CurrentPath, Where, !WhereInfo) ; true ). % This is the predicate responsible for ensuring that the act of optimizing % away the execution of a goal on some or all computation paths changes the % operational semantics only in ways that are explicitly permitted by the % programmer. % :- pred adjust_where_needed(hlds_goal::in, option_values::in, where_needed::in, where_needed::out) is det. adjust_where_needed(Goal, Options, !WhereInfo) :- ( Goal = GoalExpr - GoalInfo, ( % Do not move goals that can fail, since doing so can cause % execution to reach goals it shouldn't, and those goals may have % undesirable behavior (e.g. infinite loops). goal_info_get_determinism(GoalInfo, Detism), detism_is_moveable(Detism, no) ; % Do not move impure or semipure goals, since their ordering % wrt other such goals must be preserved. goal_info_get_features(GoalInfo, Features), set__member(impure_goal, Features) ; % With --fully-strict, we cannot optimize away infinite loops % or exceptions. Options ^ fully_strict = yes, goal_can_loop_or_throw(Goal) ; % With --no-reorder-conj, we cannot move infinite loops or % exceptions, but we can delete them. Options ^ reorder_conj = no, goal_can_loop_or_throw(Goal), !.WhereInfo = branches(BranchMap), \+ map__is_empty(BranchMap) ; % Do not delete the `true' goal, since deleting it is a no-op, % and thus does *not* strictly reduce the number of computation % paths on which a subgoal of the procedure body is executed. GoalExpr = conj([]) ; !.WhereInfo = branches(BranchMap), map__values(BranchMap, BranchArms), list__map(set__count, BranchArms, BranchArmCounts), BranchArmCount = list__foldl(int__plus, BranchArmCounts, 0), BranchArmCount > Options ^ copy_limit % We may also want to add other space time tradeoffs. E.g. if % profiling shows that Goal is required in 10 branches that % account for 99% of all executions and is not required in 5 % branches that account for the remaining 1%, and Goal itself % is sufficiently cheap to execute, then not moving Goal may cost % a small slowdown in 1% of cases but avoid 9 extra copies of Goal. % Due to better instruction cache behavior, not moving Goal % may in fact yield faster code after all. ) -> !:WhereInfo = everywhere ; true ). :- pred detism_is_moveable(determinism::in, bool::out) is det. detism_is_moveable(det, yes). detism_is_moveable(semidet, no). detism_is_moveable(nondet, no). detism_is_moveable(multidet, yes). detism_is_moveable(erroneous, no). detism_is_moveable(failure, no). detism_is_moveable(cc_nondet, no). detism_is_moveable(cc_multidet, yes). %---------------------------------------------------------------------------% :- pred demand_inputs(hlds_goal::in, module_info::in, instmap::in, where_needed::in, where_needed_map::in, where_needed_map::out) is det. demand_inputs(Goal, ModuleInfo, InitInstMap, WhereNeeded, !WhereNeededMap) :- Goal = _ - GoalInfo, goal_info_get_nonlocals(GoalInfo, NonLocalSet), goal_info_get_goal_path(GoalInfo, GoalPath), set__to_sorted_list(NonLocalSet, NonLocals), list__filter(nonlocal_may_be_input(ModuleInfo, InitInstMap), NonLocals, Inputs), list__foldl(demand_var(GoalPath, WhereNeeded), Inputs, !WhereNeededMap). :- pred nonlocal_may_be_input(module_info::in, instmap::in, prog_var::in) is semidet. nonlocal_may_be_input(ModuleInfo, InstMap, Var) :- instmap__lookup_var(InstMap, Var, Inst), inst_is_bound(ModuleInfo, Inst). %---------------------------------------------------------------------------% :- pred undemand_virgin_outputs(hlds_goal::in, module_info::in, instmap::in, where_needed_map::in, where_needed_map::out) is det. undemand_virgin_outputs(Goal, ModuleInfo, InstMap, !WhereNeededMap) :- Goal = _ - GoalInfo, goal_info_get_nonlocals(GoalInfo, NonLocalSet), set__to_sorted_list(NonLocalSet, NonLocals), list__filter(nonlocal_is_virgin_output(ModuleInfo, InstMap), NonLocals, VirginOutputs), list__foldl(undemand_var, VirginOutputs, !WhereNeededMap). :- pred nonlocal_is_virgin_output(module_info::in, instmap::in, prog_var::in) is semidet. nonlocal_is_virgin_output(ModuleInfo, InstMap, Var) :- instmap__lookup_var(InstMap, Var, Inst), \+ inst_is_bound(ModuleInfo, Inst). %---------------------------------------------------------------------------% :- pred demand_var(goal_path::in, where_needed::in, prog_var::in, where_needed_map::in, where_needed_map::out) is det. demand_var(CurrentPath, WhereNeeded, Var, !WhereNeededMap) :- ( map__search(!.WhereNeededMap, Var, Where0) -> where_needed_upper_bound(CurrentPath, WhereNeeded, Where0, Where), svmap__det_update(Var, Where, !WhereNeededMap) ; svmap__det_insert(Var, WhereNeeded, !WhereNeededMap) ). :- pred undemand_var(prog_var::in, where_needed_map::in, where_needed_map::out) is det. undemand_var(Var, WhereNeededMap0, WhereNeededMap) :- map__delete(WhereNeededMap0, Var, WhereNeededMap). %---------------------------------------------------------------------------% :- pred demand_var_everywhere(prog_var::in, where_needed::in, where_needed::out) is det. demand_var_everywhere(_Var, _WhereNeeded0, everywhere). %---------------------------------------------------------------------------% :- pred process_goal_internal(hlds_goal::in, hlds_goal::out, instmap::in, instmap::in, vartypes::in, module_info::in, option_values::in, where_needed_map::in, where_needed_map::out, refined_goal_map::in, refined_goal_map::out, bool::in, bool::out) is det. process_goal_internal(Goal0, Goal, InitInstMap, FinalInstMap, VarTypes, ModuleInfo, Options, !WhereNeededMap, !RefinedGoals, !Changed) :- Goal0 = GoalExpr0 - GoalInfo0, ( GoalExpr0 = unify(_, _, _, _, _), Goal = Goal0, demand_inputs(Goal, ModuleInfo, InitInstMap, everywhere, !WhereNeededMap) ; GoalExpr0 = call(_, _, _, _, _, _), Goal = Goal0, demand_inputs(Goal, ModuleInfo, InitInstMap, everywhere, !WhereNeededMap) ; GoalExpr0 = generic_call(_, _, _, _), Goal = Goal0, demand_inputs(Goal, ModuleInfo, InitInstMap, everywhere, !WhereNeededMap) ; GoalExpr0 = foreign_proc(_, _, _, _, _, _), Goal = Goal0, demand_inputs(Goal, ModuleInfo, InitInstMap, everywhere, !WhereNeededMap) ; GoalExpr0 = par_conj(_), Goal = Goal0, demand_inputs(Goal, ModuleInfo, InitInstMap, everywhere, !WhereNeededMap) ; GoalExpr0 = conj(Conjuncts0), process_conj(Conjuncts0, Conjuncts, InitInstMap, FinalInstMap, VarTypes, ModuleInfo, Options, !WhereNeededMap, !RefinedGoals, !Changed), GoalExpr = conj(Conjuncts), Goal = GoalExpr - GoalInfo0 ; GoalExpr0 = switch(SwitchVar, CanFail, Cases0), ( Cases0 = [case(_, _ - FirstCaseGoalInfo) | _], goal_info_get_goal_path(FirstCaseGoalInfo, FirstCaseGoalPath), FirstCaseGoalPath = [SwitchStep | _], SwitchStep = switch(_, NumCases) -> NumAlt = NumCases ; unexpected(this_file, "process_goal_internal: switch count") ), goal_info_get_goal_path(GoalInfo0, GoalPath), BranchPoint = branch_point(GoalPath, switch(NumAlt)), map__map_values(demand_var_everywhere, !WhereNeededMap), map__init(BranchNeededMap0), process_cases(Cases0, Cases, BranchPoint, 1, InitInstMap, FinalInstMap, VarTypes, ModuleInfo, Options, GoalPath, !.WhereNeededMap, BranchNeededMap0, BranchNeededMap, !RefinedGoals, !Changed), merge_where_needed_maps(GoalPath, !.WhereNeededMap, BranchNeededMap, !:WhereNeededMap), demand_var(GoalPath, everywhere, SwitchVar, !WhereNeededMap), GoalExpr = switch(SwitchVar, CanFail, Cases), Goal = GoalExpr - GoalInfo0 ; GoalExpr0 = disj(Disjuncts0), goal_info_get_goal_path(GoalInfo0, GoalPath), map__map_values(demand_var_everywhere, !WhereNeededMap), process_disj(Disjuncts0, Disjuncts, InitInstMap, FinalInstMap, VarTypes, ModuleInfo, Options, GoalPath, !.WhereNeededMap, !.WhereNeededMap, !:WhereNeededMap, !RefinedGoals, !Changed), GoalExpr = disj(Disjuncts), Goal = GoalExpr - GoalInfo0 ; GoalExpr0 = if_then_else(Quant, Cond0, Then0, Else0), goal_info_get_goal_path(GoalInfo0, GoalPath), BranchPoint = branch_point(GoalPath, ite), map__map_values(demand_var_everywhere, !WhereNeededMap), process_ite(Cond0, Cond, Then0, Then, Else0, Else, BranchPoint, InitInstMap, FinalInstMap, VarTypes, ModuleInfo, Options, GoalPath, !WhereNeededMap, !RefinedGoals, !Changed), GoalExpr = if_then_else(Quant, Cond, Then, Else), Goal = GoalExpr - GoalInfo0 ; GoalExpr0 = not(NegGoal0), process_goal(NegGoal0, NegGoal, InitInstMap, FinalInstMap, VarTypes, ModuleInfo, Options, !WhereNeededMap, !RefinedGoals, !Changed), GoalExpr = not(NegGoal), Goal = GoalExpr - GoalInfo0 ; GoalExpr0 = scope(Reason, SomeGoal0), process_goal(SomeGoal0, SomeGoal, InitInstMap, FinalInstMap, VarTypes, ModuleInfo, Options, !WhereNeededMap, !RefinedGoals, !Changed), GoalExpr = scope(Reason, SomeGoal), Goal = GoalExpr - GoalInfo0 ; GoalExpr0 = shorthand(_), unexpected(this_file, "shorthand in process_goal_internal") ). %---------------------------------------------------------------------------% :- type bracketed_goal ---> bracketed_goal(hlds_goal, instmap, instmap). :- pred process_conj(list(hlds_goal)::in, list(hlds_goal)::out, instmap::in, instmap::in, vartypes::in, module_info::in, option_values::in, where_needed_map::in, where_needed_map::out, refined_goal_map::in, refined_goal_map::out, bool::in, bool::out) is det. process_conj(Goals0, Goals, InitInstMap, _FinalInstMap, VarTypes, ModuleInfo, Options, !WhereNeededMap, !RefinedGoals, !Changed) :- build_bracketed_conj(Goals0, InitInstMap, BracketedGoals), list__reverse(BracketedGoals, RevBracketedGoals), process_rev_bracketed_conj(RevBracketedGoals, RevGoals, VarTypes, ModuleInfo, Options, !WhereNeededMap, !RefinedGoals, !Changed), list__reverse(RevGoals, Goals). :- pred build_bracketed_conj(list(hlds_goal)::in, instmap::in, list(bracketed_goal)::out) is det. build_bracketed_conj([], _, []). build_bracketed_conj([Goal | Goals], InitInstMap, BracketedGoals) :- ( instmap__is_unreachable(InitInstMap) -> BracketedGoals = [] ; Goal = _ - GoalInfo, goal_info_get_instmap_delta(GoalInfo, InstMapDelta), instmap__apply_instmap_delta(InitInstMap, InstMapDelta, FinalInstMap), build_bracketed_conj(Goals, FinalInstMap, BracketedTail), BracketedGoal = bracketed_goal(Goal, InitInstMap, FinalInstMap), BracketedGoals = [BracketedGoal | BracketedTail] ). :- pred process_rev_bracketed_conj(list(bracketed_goal)::in, list(hlds_goal)::out, vartypes::in, module_info::in, option_values::in, where_needed_map::in, where_needed_map::out, refined_goal_map::in, refined_goal_map::out, bool::in, bool::out) is det. process_rev_bracketed_conj([], [], _, _, _, !WhereNeededMap, !RefinedGoals, !Changed). process_rev_bracketed_conj([BracketedGoal | BracketedGoals], Goals, VarTypes, ModuleInfo, Options, !WhereNeededMap, !RefinedGoals, !Changed) :- BracketedGoal = bracketed_goal(Goal0, InitInstMap, FinalInstMap), process_goal(Goal0, Goal1, InitInstMap, FinalInstMap, VarTypes, ModuleInfo, Options, !WhereNeededMap, !RefinedGoals, !Changed), process_rev_bracketed_conj(BracketedGoals, Goals1, VarTypes, ModuleInfo, Options, !WhereNeededMap, !RefinedGoals, !Changed), ( true_goal(Goal1) -> Goals = Goals1 ; Goals = [Goal1 | Goals1] ). %---------------------------------------------------------------------------% :- pred process_disj(list(hlds_goal)::in, list(hlds_goal)::out, instmap::in, instmap::in, vartypes::in, module_info::in, option_values::in, goal_path::in, where_needed_map::in, where_needed_map::in, where_needed_map::out, refined_goal_map::in, refined_goal_map::out, bool::in, bool::out) is det. process_disj([], [], _, _, _, _, _, _, _, !WhereNeededMap, !RefinedGoals, !Changed). process_disj([Goal0 | Goals0], [Goal | Goals], InitInstMap, FinalInstMap, VarTypes, ModuleInfo, Options, CurrentPath, StartWhereNeededMap, !WhereNeededMap, !RefinedGoals, !Changed) :- process_goal(Goal0, Goal, InitInstMap, FinalInstMap, VarTypes, ModuleInfo, Options, StartWhereNeededMap, WhereNeededMapFirst, !RefinedGoals, !Changed), map__to_assoc_list(WhereNeededMapFirst, WhereNeededList), add_where_needed_list(WhereNeededList, CurrentPath, !WhereNeededMap), process_disj(Goals0, Goals, InitInstMap, FinalInstMap, VarTypes, ModuleInfo, Options, CurrentPath, StartWhereNeededMap, !WhereNeededMap, !RefinedGoals, !Changed). %---------------------------------------------------------------------------% :- pred process_cases(list(case)::in, list(case)::out, branch_point::in, int::in, instmap::in, instmap::in, vartypes::in, module_info::in, option_values::in, goal_path::in, where_needed_map::in, where_needed_map::in, where_needed_map::out, refined_goal_map::in, refined_goal_map::out, bool::in, bool::out) is det. process_cases([], [], _, _, _, _, _, _, _, _, _, !WhereNeededMap, !RefinedGoals, !Changed). process_cases([case(Var, Goal0) | Cases0], [case(Var, Goal) | Cases], BranchPoint, BranchNum, InitInstMap, FinalInstMap, VarTypes, ModuleInfo, Options, CurrentPath, StartWhereNeededMap, !WhereNeededMap, !RefinedGoals, !Changed) :- process_goal(Goal0, Goal, InitInstMap, FinalInstMap, VarTypes, ModuleInfo, Options, StartWhereNeededMap, WhereNeededMapFirst, !RefinedGoals, !Changed), map__to_assoc_list(WhereNeededMapFirst, WhereNeededList), add_alt_start(WhereNeededList, BranchPoint, BranchNum, CurrentPath, !WhereNeededMap), process_cases(Cases0, Cases, BranchPoint, BranchNum + 1, InitInstMap, FinalInstMap, VarTypes, ModuleInfo, Options, CurrentPath, StartWhereNeededMap, !WhereNeededMap, !RefinedGoals, !Changed). %---------------------------------------------------------------------------% :- pred process_ite(hlds_goal::in, hlds_goal::out, hlds_goal::in, hlds_goal::out, hlds_goal::in, hlds_goal::out, branch_point::in, instmap::in, instmap::in, vartypes::in, module_info::in, option_values::in, goal_path::in, where_needed_map::in, where_needed_map::out, refined_goal_map::in, refined_goal_map::out, bool::in, bool::out) is det. process_ite(Cond0, Cond, Then0, Then, Else0, Else, BranchPoint, InitInstMap, FinalInstMap, VarTypes, ModuleInfo, Options, CurrentPath, !WhereNeededMap, !RefinedGoals, !Changed) :- Cond0 = _ - CondInfo0, goal_info_get_instmap_delta(CondInfo0, InstMapDelta), instmap__apply_instmap_delta(InitInstMap, InstMapDelta, InstMapCond), process_goal(Else0, Else, InitInstMap, FinalInstMap, VarTypes, ModuleInfo, Options, !.WhereNeededMap, WhereNeededMapElse, !RefinedGoals, !Changed), process_goal(Then0, Then, InstMapCond, FinalInstMap, VarTypes, ModuleInfo, Options, !.WhereNeededMap, WhereNeededMapThen, !RefinedGoals, !Changed), map__init(BranchNeededMap0), map__to_assoc_list(WhereNeededMapElse, WhereNeededListElse), add_alt_start(WhereNeededListElse, BranchPoint, 2, CurrentPath, BranchNeededMap0, BranchNeededMap1), map__to_assoc_list(WhereNeededMapThen, WhereNeededListThen), add_alt_start(WhereNeededListThen, BranchPoint, 1, CurrentPath, BranchNeededMap1, BranchNeededMap), merge_where_needed_maps(CurrentPath, !.WhereNeededMap, BranchNeededMap, WhereNeededMapCond), process_goal(Cond0, Cond, InitInstMap, InstMapCond, VarTypes, ModuleInfo, Options, WhereNeededMapCond, !:WhereNeededMap, !RefinedGoals, !Changed). %---------------------------------------------------------------------------% % Merge two where_needed_maps, so that if var V is needed at branch B % in the resulting where_needed_map iff it is needed there in one of % the input maps. % :- pred merge_where_needed_maps(goal_path::in, where_needed_map::in, where_needed_map::in, where_needed_map::out) is det. merge_where_needed_maps(CurrentPath, WhereNeededMap1, WhereNeededMap2, WhereNeededMap) :- map__to_assoc_list(WhereNeededMap1, WhereNeededList1), add_where_needed_list(WhereNeededList1, CurrentPath, WhereNeededMap2, WhereNeededMap). :- pred add_where_needed_list(assoc_list(prog_var, where_needed)::in, goal_path::in, where_needed_map::in, where_needed_map::out) is det. add_where_needed_list([], _, !WhereNeededMap). add_where_needed_list([Var - BranchWhere | WhereNeededList], CurrentPath, !WhereNeededMap) :- ( map__search(!.WhereNeededMap, Var, OldWhere) -> where_needed_upper_bound(CurrentPath, BranchWhere, OldWhere, CombinedWhere), svmap__det_update(Var, CombinedWhere, !WhereNeededMap) ; svmap__det_insert(Var, BranchWhere, !WhereNeededMap) ), add_where_needed_list(WhereNeededList, CurrentPath, !WhereNeededMap). % Given a where_needed_map, add to it the where_needed information for the % start of an alternative in a branched goal. This source is important, % because if the analysis *at the start of an alternative* says that the % variable is needed everywhere, the scope of this "everywhere" is only % that alternative. % :- pred add_alt_start(assoc_list(prog_var, where_needed)::in, branch_point::in, int::in, goal_path::in, where_needed_map::in, where_needed_map::out) is det. add_alt_start([], _, _, _, !WhereNeededMap). add_alt_start([Var - BranchWhere0 | WhereNeededList], BranchPoint, BranchNum, CurrentPath, !WhereNeededMap) :- ( BranchWhere0 = everywhere, map__init(Empty), set__singleton_set(BranchNumSet, BranchNum), map__det_insert(Empty, BranchPoint, BranchNumSet, BranchMap), BranchWhere = branches(BranchMap) ; BranchWhere0 = branches(_), BranchWhere = BranchWhere0 ), ( map__search(!.WhereNeededMap, Var, OldWhere) -> where_needed_upper_bound(CurrentPath, BranchWhere, OldWhere, CombinedWhere), svmap__det_update(Var, CombinedWhere, !WhereNeededMap) ; svmap__det_insert(Var, BranchWhere, !WhereNeededMap) ), add_alt_start(WhereNeededList, BranchPoint, BranchNum, CurrentPath, !WhereNeededMap). %---------------------------------------------------------------------------% :- pred refine_goal(hlds_goal::in, hlds_goal::out, refined_goal_map::in, refined_goal_map::out) is det. refine_goal(Goal0, Goal, !RefinedGoals) :- Goal0 = GoalExpr0 - GoalInfo0, ( GoalExpr0 = unify(_, _, _, _, _), Goal = Goal0 ; GoalExpr0 = call(_, _, _, _, _, _), Goal = Goal0 ; GoalExpr0 = generic_call(_, _, _, _), Goal = Goal0 ; GoalExpr0 = foreign_proc(_, _, _, _, _, _), Goal = Goal0 ; GoalExpr0 = par_conj(_), Goal = Goal0 ; GoalExpr0 = conj(Conjuncts0), refine_conj(Conjuncts0, Conjuncts, !RefinedGoals), GoalExpr = conj(Conjuncts), Goal = GoalExpr - GoalInfo0 ; GoalExpr0 = switch(SwitchVar, CanFail, Cases0), goal_info_get_goal_path(GoalInfo0, GoalPath), refine_cases(Cases0, Cases, !RefinedGoals, GoalPath, 1), GoalExpr = switch(SwitchVar, CanFail, Cases), Goal = GoalExpr - GoalInfo0 ; GoalExpr0 = disj(Disjuncts0), goal_info_get_goal_path(GoalInfo0, GoalPath), refine_disj(Disjuncts0, Disjuncts, !RefinedGoals, GoalPath, 1), GoalExpr = disj(Disjuncts), Goal = GoalExpr - GoalInfo0 ; GoalExpr0 = if_then_else(Quant, Cond0, Then0, Else0), goal_info_get_goal_path(GoalInfo0, GoalPath), refine_ite(Cond0, Cond, Then0, Then, Else0, Else, !RefinedGoals, GoalPath), GoalExpr = if_then_else(Quant, Cond, Then, Else), Goal = GoalExpr - GoalInfo0 ; GoalExpr0 = not(NegGoal0), refine_goal(NegGoal0, NegGoal, !RefinedGoals), GoalExpr = not(NegGoal), Goal = GoalExpr - GoalInfo0 ; GoalExpr0 = scope(Reason, SomeGoal0), refine_goal(SomeGoal0, SomeGoal, !RefinedGoals), GoalExpr = scope(Reason, SomeGoal), Goal = GoalExpr - GoalInfo0 ; GoalExpr0 = shorthand(_), unexpected(this_file, "shorthand in refine_goal") ). :- pred refine_conj(list(hlds_goal)::in, list(hlds_goal)::out, refined_goal_map::in, refined_goal_map::out) is det. refine_conj([], [], !RefinedGoals). refine_conj([Goal0 | Goals0], Goals, !RefinedGoals) :- refine_goal(Goal0, HeadGoal, !RefinedGoals), refine_conj(Goals0, TailGoals, !RefinedGoals), ( HeadGoal = conj(HeadGoals) - _ -> list__append(HeadGoals, TailGoals, Goals) ; Goals = [HeadGoal | TailGoals] ). :- pred refine_cases(list(case)::in, list(case)::out, refined_goal_map::in, refined_goal_map::out, goal_path::in, int::in) is det. refine_cases([], [], !RefinedGoals, _, _). refine_cases([case(Var, Goal0) | Cases0], [case(Var, Goal) | Cases], !RefinedGoals, GoalPath, BranchNum) :- refine_goal(Goal0, Goal1, !RefinedGoals), ( map__search(!.RefinedGoals, GoalPath - BranchNum, ToInsertGoals) -> insert_refine_goals(ToInsertGoals, Goal1, Goal), svmap__delete(GoalPath - BranchNum, !RefinedGoals) ; Goal = Goal1 ), refine_cases(Cases0, Cases, !RefinedGoals, GoalPath, BranchNum + 1). :- pred refine_disj(list(hlds_goal)::in, list(hlds_goal)::out, refined_goal_map::in, refined_goal_map::out, goal_path::in, int::in) is det. refine_disj([], [], !RefinedGoals, _, _). refine_disj([Goal0 | Goals0], [Goal | Goals], !RefinedGoals, GoalPath, BranchNum) :- refine_goal(Goal0, Goal1, !RefinedGoals), ( map__search(!.RefinedGoals, GoalPath - BranchNum, ToInsertGoals) -> insert_refine_goals(ToInsertGoals, Goal1, Goal), svmap__delete(GoalPath - BranchNum, !RefinedGoals) ; Goal = Goal1 ), refine_disj(Goals0, Goals, !RefinedGoals, GoalPath, BranchNum + 1). :- pred refine_ite(hlds_goal::in, hlds_goal::out, hlds_goal::in, hlds_goal::out, hlds_goal::in, hlds_goal::out, refined_goal_map::in, refined_goal_map::out, goal_path::in) is det. refine_ite(Cond0, Cond, Then0, Then, Else0, Else, !RefinedGoals, GoalPath) :- refine_goal(Cond0, Cond, !RefinedGoals), refine_goal(Then0, Then1, !RefinedGoals), refine_goal(Else0, Else1, !RefinedGoals), ( map__search(!.RefinedGoals, GoalPath - 1, ToInsertGoalsThen) -> insert_refine_goals(ToInsertGoalsThen, Then1, Then), svmap__delete(GoalPath - 1, !RefinedGoals) ; Then = Then1 ), ( map__search(!.RefinedGoals, GoalPath - 2, ToInsertGoalsElse) -> insert_refine_goals(ToInsertGoalsElse, Else1, Else), svmap__delete(GoalPath - 2, !RefinedGoals) ; Else = Else1 ). :- pred insert_refine_goals(list(hlds_goal)::in, hlds_goal::in, hlds_goal::out) is det. insert_refine_goals(ToInsertGoals, Goal0, Goal) :- list__append(ToInsertGoals, [Goal0], Conj), % XXX GoalInfo0 Goal0 = _ - GoalInfo0, conj_list_to_goal(Conj, GoalInfo0, Goal). %-----------------------------------------------------------------------------% % Given two sets of requirements about where a goal is needed, return % a single requirement that contains all the demands. The main purpose % of this predicate is to discover when the union of two sets of % requirements (e.g. branch sets {b1,b2} and {b3} covers all % computation paths. % :- pred where_needed_upper_bound(goal_path::in, where_needed::in, where_needed::in, where_needed::out) is det. where_needed_upper_bound(CurrentPath, WhereNeededA, WhereNeededB, WhereNeeded) :- ( WhereNeededA = everywhere, WhereNeeded = everywhere ; WhereNeededA = branches(BranchesA), ( WhereNeededB = everywhere, WhereNeeded = everywhere ; WhereNeededB = branches(BranchesB), where_needed_branches_upper_bound(CurrentPath, BranchesA, BranchesB, WhereNeeded) ) ). :- pred where_needed_branches_upper_bound(goal_path::in, where_needed_branches::in, where_needed_branches::in, where_needed::out) is det. where_needed_branches_upper_bound(CurrentPath, BranchesA, BranchesB, WhereNeeded) :- % should select smaller map to convert to list map__to_assoc_list(BranchesA, BranchesList), where_needed_branches_upper_bound_2(CurrentPath, BranchesList, BranchesB, WhereNeeded). :- pred where_needed_branches_upper_bound_2(goal_path::in, assoc_list(branch_point, set(int))::in, where_needed_branches::in, where_needed::out) is det. where_needed_branches_upper_bound_2(_, [], Branches, branches(Branches)). where_needed_branches_upper_bound_2(CurrentPath, [First | Rest], Branches0, WhereNeeded) :- First = BranchPoint - NewAlts, ( map__search(Branches0, BranchPoint, OldAlts) -> set__union(OldAlts, NewAlts, Alts), BranchPoint = branch_point(GoalPath, BranchAlts), ( branch_point_is_complete(BranchAlts, Alts) -> ( get_parent_branch_point(GoalPath, ParentGoalPath, ParentGoalPathStep, ParentBranchAlt, ParentBranchNum), \+ list__remove_suffix(CurrentPath, [ParentGoalPathStep | ParentGoalPath], _) -> map__delete(Branches0, BranchPoint, Branches1), ParentBranchPoint = branch_point(ParentGoalPath, ParentBranchAlt), set__singleton_set(ParentAlts, ParentBranchNum), where_needed_branches_upper_bound_2(CurrentPath, [ParentBranchPoint - ParentAlts | Rest], Branches1, WhereNeeded) ; WhereNeeded = everywhere ) ; map__det_update(Branches0, BranchPoint, Alts, Branches1), where_needed_branches_upper_bound_2(CurrentPath, Rest, Branches1, WhereNeeded) ) ; map__det_insert(Branches0, BranchPoint, NewAlts, Branches1), where_needed_branches_upper_bound_2(CurrentPath, Rest, Branches1, WhereNeeded) ). :- pred get_parent_branch_point(goal_path::in, goal_path::out, goal_path_step::out, branch_alts::out, int::out) is semidet. get_parent_branch_point([First | Rest], Parent, ParentStep, BranchAlt, BranchNum) :- ( First = switch(Arm, NumAlts) -> Parent = Rest, ParentStep = First, BranchAlt = switch(NumAlts), BranchNum = Arm ; First = ite_then -> Parent = Rest, ParentStep = First, BranchAlt = ite, BranchNum = 1 ; First = ite_else -> Parent = Rest, ParentStep = First, BranchAlt = ite, BranchNum = 2 ; get_parent_branch_point(Rest, Parent, ParentStep, BranchAlt, BranchNum) ). :- pred branch_point_is_complete(branch_alts::in, set(int)::in) is semidet. branch_point_is_complete(ite, Alts) :- set__count(Alts, NumAlts), NumAlts = 2. branch_point_is_complete(switch(NumFunctors), Alts) :- set__count(Alts, NumAlts), NumAlts = NumFunctors. %---------------------------------------------------------------------------% :- func this_file = string. this_file = "unneeded_code.m". %---------------------------------------------------------------------------% :- end_module unneeded_code. %---------------------------------------------------------------------------%