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672f77c4ec
Estimated hours taken: 20 Branches: main Add a new compiler option. --inform-ite-instead-of-switch. If this is enabled, the compiler will generate informational messages about if-then-elses that it thinks should be converted to switches for the sake of program reliability. Act on the output generated by this option. compiler/simplify.m: Implement the new option. Fix an old bug that could cause us to generate warnings about code that was OK in one duplicated copy but not in another (where a switch arm's code is duplicated due to the case being selected for more than one cons_id). compiler/options.m: Add the new option. Add a way to test for the bug fix in simplify. doc/user_guide.texi: Document the new option. NEWS: Mention the new option. library/*.m: mdbcomp/*.m: browser/*.m: compiler/*.m: deep_profiler/*.m: Convert if-then-elses to switches at most of the sites suggested by the new option. At the remaining sites, switching to switches would have nontrivial downsides. This typically happens with the switched-on type has many functors, and we treat one or two specially (e.g. cons/2 in the cons_id type). Perform misc cleanups in the vicinity of the if-then-else to switch conversions. In a few cases, improve the error messages generated. compiler/accumulator.m: compiler/hlds_goal.m: (Rename and) move insts for particular kinds of goal from accumulator.m to hlds_goal.m, to allow them to be used in other modules. Using these insts allowed us to eliminate some if-then-elses entirely. compiler/exprn_aux.m: Instead of fixing some if-then-elses, delete the predicates containing them, since they aren't used, and (as pointed out by the new option) would need considerable other fixing if they were ever needed again. compiler/lp_rational.m: Add prefixes to the names of the function symbols on some types, since without those prefixes, it was hard to figure out what type the switch corresponding to an old if-then-else was switching on. tests/invalid/reserve_tag.err_exp: Expect a new, improved error message.
771 lines
29 KiB
Mathematica
771 lines
29 KiB
Mathematica
%-----------------------------------------------------------------------------%
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% vim: ft=mercury ts=4 sw=4 et
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%-----------------------------------------------------------------------------%
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% Copyright (C) 1994-2007 The University of Melbourne.
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% This file may only be copied under the terms of the GNU General
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% Public License - see the file COPYING in the Mercury distribution.
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%-----------------------------------------------------------------------------%
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%
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% File: switch_detection.m.
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% Main author: fjh.
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%
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% Switch detection - when a disjunction contains disjuncts that unify the
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% same input variable with different function symbols, replace (part of)
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% the disjunction with a switch.
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%
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%-----------------------------------------------------------------------------%
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:- module check_hlds.switch_detection.
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:- interface.
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:- import_module hlds.
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:- import_module hlds.hlds_goal.
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:- import_module hlds.hlds_module.
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:- import_module hlds.hlds_pred.
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:- import_module parse_tree.
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:- import_module parse_tree.prog_data.
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:- import_module bool.
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:- import_module io.
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:- import_module list.
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%-----------------------------------------------------------------------------%
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:- pred detect_switches(module_info::in, module_info::out,
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io::di, io::uo) is det.
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:- pred detect_switches_in_proc(proc_id::in, pred_id::in,
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module_info::in, module_info::out) is det.
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% find_bind_var(Var, ProcessUnify, Goal0, Goal, !Result, !Info,
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% FoundDeconstruct):
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%
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% Used by both switch_detection and cse_detection. Searches through
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% `Goal0' looking for the first deconstruction unification with `Var'
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% or an alias of `Var'. If a deconstruction unification of the
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% variable is found, `ProcessUnify' is called to handle it (which may
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% replace the unification with some other goals, which is why we return
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% Goal), and searching is stopped. If we don't find such a deconstruction,
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% `!Result' is unchanged.
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%
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:- pred find_bind_var(prog_var::in,
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process_unify(Result, Info)::in(process_unify),
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hlds_goal::in, hlds_goal::out, Result::in, Result::out,
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Info::in, Info::out, bool::out) is det.
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:- type process_unify(Result, Info) ==
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pred(prog_var, hlds_goal, list(hlds_goal), Result, Result, Info, Info).
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:- inst process_unify == (pred(in, in, out, in, out, in, out) is det).
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%-----------------------------------------------------------------------------%
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%-----------------------------------------------------------------------------%
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:- implementation.
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:- import_module check_hlds.det_util.
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:- import_module check_hlds.inst_match.
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:- import_module check_hlds.type_util.
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:- import_module hlds.goal_util.
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:- import_module hlds.hlds_goal.
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:- import_module hlds.instmap.
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:- import_module hlds.passes_aux.
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:- import_module hlds.quantification.
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:- import_module libs.
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:- import_module libs.compiler_util.
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:- import_module parse_tree.prog_data.
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:- import_module parse_tree.prog_mode.
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:- import_module assoc_list.
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:- import_module int.
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:- import_module map.
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:- import_module maybe.
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:- import_module pair.
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:- import_module set.
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:- import_module term.
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:- import_module unit.
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%-----------------------------------------------------------------------------%
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detect_switches(!ModuleInfo, !IO) :-
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% Traverse the module structure, calling `detect_switches_in_goal'
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% for each procedure body.
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module_info_predids(PredIds, !ModuleInfo),
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detect_switches_in_preds(PredIds, !ModuleInfo, !IO).
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:- pred detect_switches_in_preds(list(pred_id)::in,
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module_info::in, module_info::out, io::di, io::uo) is det.
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detect_switches_in_preds([], !ModuleInfo, !IO).
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detect_switches_in_preds([PredId | PredIds], !ModuleInfo, !IO) :-
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module_info_preds(!.ModuleInfo, PredTable),
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map.lookup(PredTable, PredId, PredInfo),
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detect_switches_in_pred(PredId, PredInfo, !ModuleInfo, !IO),
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detect_switches_in_preds(PredIds, !ModuleInfo, !IO).
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:- pred detect_switches_in_pred(pred_id::in, pred_info::in,
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module_info::in, module_info::out, io::di, io::uo) is det.
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detect_switches_in_pred(PredId, PredInfo0, !ModuleInfo, !IO) :-
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ProcIds = pred_info_non_imported_procids(PredInfo0),
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(
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ProcIds = [_ | _],
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write_pred_progress_message("% Detecting switches in ", PredId,
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!.ModuleInfo, !IO),
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detect_switches_in_procs(ProcIds, PredId, !ModuleInfo)
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% This is where we should print statistics, if we ever need
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% to debug the performance of switch detection.
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;
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ProcIds = []
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).
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:- pred detect_switches_in_procs(list(proc_id)::in, pred_id::in,
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module_info::in, module_info::out) is det.
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detect_switches_in_procs([], _PredId, !ModuleInfo).
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detect_switches_in_procs([ProcId | ProcIds], PredId, !ModuleInfo) :-
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detect_switches_in_proc(ProcId, PredId, !ModuleInfo),
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detect_switches_in_procs(ProcIds, PredId, !ModuleInfo).
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detect_switches_in_proc(ProcId, PredId, !ModuleInfo) :-
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module_info_preds(!.ModuleInfo, PredTable0),
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map.lookup(PredTable0, PredId, PredInfo0),
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pred_info_get_procedures(PredInfo0, ProcTable0),
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map.lookup(ProcTable0, ProcId, ProcInfo0),
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% To process each ProcInfo, we get the goal, initialize the instmap
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% based on the modes of the head vars, and pass these to
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% `detect_switches_in_goal'.
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proc_info_get_goal(ProcInfo0, Goal0),
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proc_info_get_vartypes(ProcInfo0, VarTypes),
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proc_info_get_initial_instmap(ProcInfo0, !.ModuleInfo, InstMap0),
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detect_switches_in_goal(!.ModuleInfo, VarTypes, InstMap0, Goal0, Goal,
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no, Requant),
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proc_info_set_goal(Goal, ProcInfo0, ProcInfo1),
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(
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Requant = yes,
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requantify_proc(ProcInfo1, ProcInfo)
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;
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Requant = no,
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ProcInfo = ProcInfo1
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),
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map.det_update(ProcTable0, ProcId, ProcInfo, ProcTable),
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pred_info_set_procedures(ProcTable, PredInfo0, PredInfo),
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map.det_update(PredTable0, PredId, PredInfo, PredTable),
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module_info_set_preds(PredTable, !ModuleInfo).
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%-----------------------------------------------------------------------------%
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% Given a goal, and the instmap on entry to that goal,
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% replace disjunctions with switches whereever possible.
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%
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:- pred detect_switches_in_goal(module_info::in, vartypes::in,
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instmap::in, hlds_goal::in, hlds_goal::out, bool::in, bool::out) is det.
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detect_switches_in_goal(ModuleInfo, VarTypes, InstMap0, !Goal, !Requant) :-
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detect_switches_in_goal_1(ModuleInfo, VarTypes, InstMap0, _InstMap,
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!Goal, !Requant).
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% This version is the same as the above except that it returns the
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% resulting instmap on exit from the goal, which is computed by applying
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% the instmap delta specified in the goal's goalinfo.
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%
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:- pred detect_switches_in_goal_1(module_info::in, vartypes::in,
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instmap::in, instmap::out, hlds_goal::in, hlds_goal::out,
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bool::in, bool::out) is det.
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detect_switches_in_goal_1(ModuleInfo, VarTypes, !InstMap,
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Goal0, Goal, !Requant) :-
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Goal0 = hlds_goal(GoalExpr0, GoalInfo),
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detect_switches_in_goal_2(ModuleInfo, VarTypes, !.InstMap, GoalInfo,
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GoalExpr0, GoalExpr, !Requant),
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Goal = hlds_goal(GoalExpr, GoalInfo),
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update_instmap(Goal0, !InstMap).
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% Here we process each of the different sorts of goals.
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%
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:- pred detect_switches_in_goal_2(module_info::in, vartypes::in, instmap::in,
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hlds_goal_info::in, hlds_goal_expr::in, hlds_goal_expr::out,
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bool::in, bool::out) is det.
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detect_switches_in_goal_2(ModuleInfo, VarTypes, InstMap0, GoalInfo,
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Goal0, Goal, !Requant) :-
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(
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Goal0 = disj(Goals0),
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(
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Goals0 = [],
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Goal = disj([])
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;
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Goals0 = [_ | _],
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NonLocals = goal_info_get_nonlocals(GoalInfo),
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set.to_sorted_list(NonLocals, NonLocalsList),
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detect_switches_in_disj(NonLocalsList, Goals0, GoalInfo, InstMap0,
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VarTypes, NonLocalsList, ModuleInfo, [], Goal, !Requant)
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)
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;
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Goal0 = conj(ConjType, Goals0),
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detect_switches_in_conj(ModuleInfo, VarTypes, InstMap0,
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Goals0, Goals, !Requant),
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Goal = conj(ConjType, Goals)
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;
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Goal0 = negation(SubGoal0),
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detect_switches_in_goal(ModuleInfo, VarTypes, InstMap0,
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SubGoal0, SubGoal, !Requant),
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Goal = negation(SubGoal)
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;
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Goal0 = if_then_else(Vars, Cond0, Then0, Else0),
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detect_switches_in_goal_1(ModuleInfo, VarTypes, InstMap0, InstMap1,
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Cond0, Cond, !Requant),
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detect_switches_in_goal(ModuleInfo, VarTypes, InstMap1, Then0, Then,
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!Requant),
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detect_switches_in_goal(ModuleInfo, VarTypes, InstMap0, Else0, Else,
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!Requant),
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Goal = if_then_else(Vars, Cond, Then, Else)
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;
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Goal0 = switch(Var, CanFail, Cases0),
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detect_switches_in_cases(ModuleInfo, VarTypes, InstMap0,
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Cases0, Cases, !Requant),
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Goal = switch(Var, CanFail, Cases)
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;
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Goal0 = scope(Reason, SubGoal0),
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detect_switches_in_goal(ModuleInfo, VarTypes, InstMap0,
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SubGoal0, SubGoal, !Requant),
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Goal = scope(Reason, SubGoal)
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;
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Goal0 = unify(_, RHS0, _, _, _),
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(
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RHS0 = rhs_lambda_goal(_, _, _, _, Vars, Modes, _, LambdaGoal0),
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% We need to insert the initial insts for the lambda variables
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% in the instmap before processing the lambda goal.
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instmap.pre_lambda_update(ModuleInfo, Vars, Modes,
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InstMap0, InstMap1),
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detect_switches_in_goal(ModuleInfo, VarTypes, InstMap1,
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LambdaGoal0, LambdaGoal, !Requant),
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RHS = RHS0 ^ rhs_lambda_goal := LambdaGoal,
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Goal = Goal0 ^ unify_rhs := RHS
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;
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( RHS0 = rhs_var(_)
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; RHS0 = rhs_functor(_, _, _)
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),
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Goal = Goal0
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)
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;
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Goal0 = generic_call(_, _, _, _),
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Goal = Goal0
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;
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Goal0 = plain_call(_, _, _, _, _, _),
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Goal = Goal0
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;
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Goal0 = call_foreign_proc(_, _, _, _, _, _, _),
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Goal = Goal0
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;
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Goal0 = shorthand(_),
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% These should have been expanded out by now.
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unexpected(this_file, "detect_switches_in_goal_2: shorthand")
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).
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%-----------------------------------------------------------------------------%
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:- type cases == map(cons_id, list(hlds_goal)).
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:- type sorted_case_list == list(case).
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% The sorted_case_list should always be sorted on cons_id -
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% `delete_unreachable_cases' relies on this.
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:- type again
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---> again(prog_var, list(hlds_goal), sorted_case_list).
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% This is the interesting bit - we've found a non-empty disjunction,
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% and we've got a list of the non-local variables of that disjunction.
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% Now for each non-local variable, we check whether there is a partition
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% of the disjuncts such that each group of disjunctions can only succeed
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% if the variable is bound to a different functor.
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%
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:- pred detect_switches_in_disj(list(prog_var)::in, list(hlds_goal)::in,
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hlds_goal_info::in, instmap::in, vartypes::in,
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list(prog_var)::in, module_info::in, list(again)::in,
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hlds_goal_expr::out, bool::in, bool::out) is det.
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detect_switches_in_disj([Var | Vars], Goals0, GoalInfo, InstMap,
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VarTypes, AllVars, ModuleInfo, Again0, Goal, !Requant) :-
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% Can we do at least a partial switch on this variable?
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(
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instmap.lookup_var(InstMap, Var, VarInst0),
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inst_is_bound(ModuleInfo, VarInst0),
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partition_disj(Goals0, Var, GoalInfo, Left, CasesList, !Requant)
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->
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% A switch needs to have at least two cases.
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%
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% But, if there is a complete one-case switch for a goal, we must leave
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% it as a disjunction rather than doing an incomplete switch on a
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% different variable, because otherwise we might get determinism
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% analysis wrong. (The complete one-case switch may be decomposable
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% into other complete sub-switches on the functor's arguments)
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(
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% Are there any disjuncts that are not part of the switch? No.
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Left = [],
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( CasesList = [_, _ | _] ->
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cases_to_switch(CasesList, Var, VarTypes, GoalInfo, InstMap,
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ModuleInfo, Goal, !Requant)
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;
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detect_sub_switches_in_disj(ModuleInfo, VarTypes, InstMap,
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Goals0, Goals, !Requant),
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Goal = disj(Goals)
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)
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;
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% Are there any disjuncts that are not part of the switch? Yes.
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Left = [_ | _],
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% Insert this switch into the list of incomplete switches
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% only if it has at least two cases.
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( CasesList = [_, _ | _] ->
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Again1 = [again(Var, Left, CasesList) | Again0]
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;
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Again1 = Again0
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),
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% Try to find a switch.
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detect_switches_in_disj(Vars, Goals0, GoalInfo, InstMap, VarTypes,
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AllVars, ModuleInfo, Again1, Goal, !Requant)
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)
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;
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detect_switches_in_disj(Vars, Goals0, GoalInfo, InstMap,
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VarTypes, AllVars, ModuleInfo, Again0, Goal, !Requant)
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).
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detect_switches_in_disj([], Goals0, GoalInfo, InstMap,
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VarTypes, AllVars, ModuleInfo, AgainList0, disj(Goals), !Requant) :-
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(
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AgainList0 = [],
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detect_sub_switches_in_disj(ModuleInfo, VarTypes, InstMap,
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Goals0, Goals, !Requant)
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;
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AgainList0 = [Again | AgainList1],
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select_best_switch(AgainList1, Again, BestAgain),
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BestAgain = again(Var, Left0, CasesList),
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cases_to_switch(CasesList, Var, VarTypes, GoalInfo, InstMap,
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ModuleInfo, SwitchGoal, !Requant),
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detect_switches_in_disj(AllVars, Left0, GoalInfo, InstMap,
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VarTypes, AllVars, ModuleInfo, [], Left, !Requant),
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goal_to_disj_list(hlds_goal(Left, GoalInfo), LeftList),
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Goals = [hlds_goal(SwitchGoal, GoalInfo) | LeftList]
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).
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:- pred select_best_switch(list(again)::in, again::in, again::out) is det.
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select_best_switch([], BestAgain, BestAgain).
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select_best_switch([Again | AgainList], BestAgain0, BestAgain) :-
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(
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Again = again(_, _, CasesList),
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BestAgain0 = again(_, _, BestCasesList),
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list.length(CasesList, Length),
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list.length(BestCasesList, BestLength),
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Length < BestLength
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->
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BestAgain1 = BestAgain0
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;
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BestAgain1 = Again
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),
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select_best_switch(AgainList, BestAgain1, BestAgain).
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:- pred detect_sub_switches_in_disj(module_info::in, vartypes::in, instmap::in,
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list(hlds_goal)::in, list(hlds_goal)::out, bool::in, bool::out) is det.
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detect_sub_switches_in_disj(_ModuleInfo, _VarTypes, _InstMap, [], [],
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!Requant).
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detect_sub_switches_in_disj(ModuleInfo, VarTypes, InstMap,
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[Goal0 | Goals0], [Goal | Goals], !Requant) :-
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detect_switches_in_goal(ModuleInfo, VarTypes, InstMap, Goal0, Goal,
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!Requant),
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detect_sub_switches_in_disj(ModuleInfo, VarTypes, InstMap,
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Goals0, Goals, !Requant).
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:- pred detect_switches_in_cases(module_info::in, vartypes::in, instmap::in,
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list(case)::in, list(case)::out, bool::in, bool::out) is det.
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detect_switches_in_cases(_, _, _, [], [], !Requant).
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detect_switches_in_cases(ModuleInfo, VarTypes, InstMap,
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[Case0 | Cases0], [Case | Cases], !Requant) :-
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Case0 = case(Functor, Goal0),
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detect_switches_in_goal(ModuleInfo, VarTypes, InstMap, Goal0, Goal,
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!Requant),
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Case = case(Functor, Goal),
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detect_switches_in_cases(ModuleInfo, VarTypes, InstMap, Cases0, Cases,
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!Requant).
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:- pred detect_switches_in_conj(module_info::in, vartypes::in, instmap::in,
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list(hlds_goal)::in, list(hlds_goal)::out, bool::in, bool::out) is det.
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detect_switches_in_conj(_, _, _, [], [], !Requant).
|
|
detect_switches_in_conj(ModuleInfo, VarTypes, InstMap0,
|
|
[Goal0 | Goals0], [Goal | Goals], !Requant) :-
|
|
detect_switches_in_goal_1(ModuleInfo, VarTypes, InstMap0, InstMap1,
|
|
Goal0, Goal, !Requant),
|
|
detect_switches_in_conj(ModuleInfo, VarTypes, InstMap1, Goals0, Goals,
|
|
!Requant).
|
|
|
|
%-----------------------------------------------------------------------------%
|
|
|
|
% partition_disj(Goals, Var, GoalInfo, VarTypes, ModuleInfo, Left, Cases):
|
|
%
|
|
% Attempts to partition the disjunction `Goals' into a switch on `Var'.
|
|
% If at least partially successful, returns the resulting `Cases', with
|
|
% any disjunction goals not fitting into the switch in Left.
|
|
%
|
|
% Given the list of goals in a disjunction, and an input variable to switch
|
|
% on, we attempt to partition the goals into a switch. For each constructor
|
|
% id, we record the list of disjuncts which unify the variable with that
|
|
% constructor. We partition the goals by abstractly interpreting the
|
|
% unifications at the start of each disjunction, to build up a
|
|
% substitution.
|
|
%
|
|
:- pred partition_disj(list(hlds_goal)::in, prog_var::in, hlds_goal_info::in,
|
|
list(hlds_goal)::out, sorted_case_list::out, bool::in, bool::out)
|
|
is semidet.
|
|
|
|
partition_disj(Goals0, Var, GoalInfo, Left, CasesList, !Requant) :-
|
|
map.init(Cases0),
|
|
partition_disj_trial(Goals0, Var, [], Left1, Cases0, Cases1),
|
|
map.to_assoc_list(Cases1, CasesAssocList1),
|
|
(
|
|
Left1 = [],
|
|
CasesAssocList1 = [_ | _], % There must be at least one case.
|
|
Left = Left1,
|
|
fix_case_list(CasesAssocList1, GoalInfo, CasesList)
|
|
;
|
|
Left1 = [_ | _],
|
|
% We don't insist on CasesAssocList1 not being empty, to allow for
|
|
% switches in which *all* cases contain subsidiary disjunctions.
|
|
( expand_sub_disjs(Var, Left1, Cases1, Cases) ->
|
|
Left = [],
|
|
map.to_assoc_list(Cases, CasesAssocList),
|
|
CasesAssocList = [_ | _], % There must be at least one case.
|
|
fix_case_list(CasesAssocList, GoalInfo, CasesList),
|
|
!:Requant = yes
|
|
;
|
|
Left = Left1,
|
|
fix_case_list(CasesAssocList1, GoalInfo, CasesList)
|
|
)
|
|
).
|
|
|
|
%-----------------------------------------------------------------------------%
|
|
|
|
:- pred expand_sub_disjs(prog_var::in, list(hlds_goal)::in,
|
|
cases::in, cases::out) is semidet.
|
|
|
|
expand_sub_disjs(_Var, [], !Cases).
|
|
expand_sub_disjs(Var, [LeftGoal | LeftGoals], !Cases) :-
|
|
expand_sub_disj(Var, LeftGoal, !Cases),
|
|
expand_sub_disjs(Var, LeftGoals, !Cases).
|
|
|
|
:- pred expand_sub_disj(prog_var::in, hlds_goal::in, cases::in, cases::out)
|
|
is semidet.
|
|
|
|
expand_sub_disj(Var, Goal, !Cases) :-
|
|
Goal = hlds_goal(GoalExpr, GoalInfo0),
|
|
goal_info_add_feature(feature_duplicated_for_switch, GoalInfo0, GoalInfo),
|
|
( GoalExpr = conj(plain_conj, SubGoals) ->
|
|
expand_sub_disj_process_conj(Var, SubGoals, [], GoalInfo, !Cases)
|
|
; GoalExpr = disj(_) ->
|
|
expand_sub_disj_process_conj(Var, [Goal], [], GoalInfo, !Cases)
|
|
;
|
|
fail
|
|
).
|
|
|
|
:- pred expand_sub_disj_process_conj(prog_var::in, list(hlds_goal)::in,
|
|
list(hlds_goal)::in, hlds_goal_info::in, cases::in, cases::out) is semidet.
|
|
|
|
expand_sub_disj_process_conj(Var, ConjGoals, !.RevUnifies, GoalInfo,
|
|
!Cases) :-
|
|
(
|
|
ConjGoals = [],
|
|
fail
|
|
;
|
|
ConjGoals = [FirstGoal | RestGoals],
|
|
FirstGoal = hlds_goal(FirstGoalExpr, _),
|
|
(
|
|
FirstGoalExpr = unify(_, _, _, _, _),
|
|
!:RevUnifies = [FirstGoal | !.RevUnifies],
|
|
expand_sub_disj_process_conj(Var, RestGoals, !.RevUnifies,
|
|
GoalInfo, !Cases)
|
|
;
|
|
FirstGoalExpr = disj(Disjuncts),
|
|
Disjuncts = [_ | _],
|
|
list.reverse(!.RevUnifies, Unifies),
|
|
list.map(
|
|
create_expanded_conjunction(Unifies, RestGoals, GoalInfo),
|
|
Disjuncts, ExpandedConjunctions),
|
|
partition_disj_trial(ExpandedConjunctions, Var, [], Left, !Cases),
|
|
Left = []
|
|
)
|
|
).
|
|
|
|
:- pred create_expanded_conjunction(list(hlds_goal)::in, list(hlds_goal)::in,
|
|
hlds_goal_info::in, hlds_goal::in, hlds_goal::out) is det.
|
|
|
|
create_expanded_conjunction(Unifies, RestGoals, GoalInfo, Disjunct, Goal) :-
|
|
( Disjunct = hlds_goal(conj(plain_conj, DisjunctGoals), _) ->
|
|
Conjuncts = Unifies ++ DisjunctGoals ++ RestGoals
|
|
;
|
|
Conjuncts = Unifies ++ [Disjunct] ++ RestGoals
|
|
),
|
|
Goal = hlds_goal(conj(plain_conj, Conjuncts), GoalInfo).
|
|
|
|
%-----------------------------------------------------------------------------%
|
|
|
|
:- pred partition_disj_trial(list(hlds_goal)::in, prog_var::in,
|
|
list(hlds_goal)::in, list(hlds_goal)::out,
|
|
cases::in, cases::out) is det.
|
|
|
|
partition_disj_trial([], _Var, !Left, !Cases).
|
|
partition_disj_trial([Goal0 | Goals], Var, !Left, !Cases) :-
|
|
find_bind_var(Var, find_bind_var_for_switch_in_deconstruct, Goal0, Goal,
|
|
no, MaybeFunctor, unit, _, _),
|
|
(
|
|
MaybeFunctor = yes(Functor),
|
|
( map.search(!.Cases, Functor, DisjList0) ->
|
|
DisjList = [Goal | DisjList0],
|
|
map.det_update(!.Cases, Functor, DisjList, !:Cases)
|
|
;
|
|
DisjList = [Goal],
|
|
map.det_insert(!.Cases, Functor, DisjList, !:Cases)
|
|
)
|
|
;
|
|
MaybeFunctor = no,
|
|
!:Left = [Goal0 | !.Left]
|
|
),
|
|
partition_disj_trial(Goals, Var, !Left, !Cases).
|
|
|
|
:- pred find_bind_var_for_switch_in_deconstruct(prog_var::in, hlds_goal::in,
|
|
list(hlds_goal)::out, maybe(cons_id)::in, maybe(cons_id)::out,
|
|
unit::in, unit::out) is det.
|
|
|
|
find_bind_var_for_switch_in_deconstruct(SwitchVar, Goal0, Goals,
|
|
_Result0, Result, _, unit) :-
|
|
(
|
|
Goal0 = hlds_goal(GoalExpr0, GoalInfo),
|
|
UnifyInfo0 = GoalExpr0 ^ unify_kind,
|
|
UnifyInfo0 = deconstruct(UnifyVar, Functor, ArgVars, _, _, _)
|
|
->
|
|
Result = yes(Functor),
|
|
(
|
|
ArgVars = [],
|
|
SwitchVar = UnifyVar
|
|
->
|
|
% The test will get carried out in the switch, there are no
|
|
% argument values to pick up, and the test was on the switch
|
|
% variable (not on one of its aliases), so the unification
|
|
% serve no further purpose. We delete it here, so simplify
|
|
% doesn't have to.
|
|
Goals = []
|
|
;
|
|
% The deconstruction unification now becomes deterministic, since
|
|
% the test will get carried out in the switch.
|
|
UnifyInfo = UnifyInfo0 ^ deconstruct_can_fail := cannot_fail,
|
|
GoalExpr = GoalExpr0 ^ unify_kind := UnifyInfo,
|
|
Goal = hlds_goal(GoalExpr, GoalInfo),
|
|
Goals = [Goal]
|
|
)
|
|
;
|
|
unexpected(this_file, "find_bind_var_for_switch_in_deconstruct")
|
|
).
|
|
|
|
%-----------------------------------------------------------------------------%
|
|
|
|
find_bind_var(Var, ProcessUnify, !Goal, !Result, !Info, FoundDeconstruct) :-
|
|
map.init(Subst),
|
|
find_bind_var_2(Var, ProcessUnify, !Goal, Subst, _, !Result, !Info,
|
|
DeconstructSearch),
|
|
(
|
|
DeconstructSearch = before_deconstruct,
|
|
FoundDeconstruct = no
|
|
;
|
|
DeconstructSearch = found_deconstruct,
|
|
FoundDeconstruct = yes
|
|
;
|
|
DeconstructSearch = given_up_search,
|
|
FoundDeconstruct = no
|
|
).
|
|
|
|
:- type deconstruct_search
|
|
---> before_deconstruct
|
|
; found_deconstruct
|
|
; given_up_search.
|
|
|
|
:- pred find_bind_var_2(prog_var::in,
|
|
process_unify(Result, Info)::in(process_unify),
|
|
hlds_goal::in, hlds_goal::out,
|
|
prog_substitution::in, prog_substitution::out, Result::in, Result::out,
|
|
Info::in, Info::out, deconstruct_search::out) is det.
|
|
|
|
find_bind_var_2(Var, ProcessUnify, Goal0, Goal, !Subst, !Result, !Info,
|
|
FoundDeconstruct) :-
|
|
Goal0 = hlds_goal(GoalExpr0, GoalInfo),
|
|
(
|
|
GoalExpr0 = scope(Reason, SubGoal0),
|
|
find_bind_var_2(Var, ProcessUnify, SubGoal0, SubGoal, !Subst,
|
|
!Result, !Info, FoundDeconstruct),
|
|
Goal = hlds_goal(scope(Reason, SubGoal), GoalInfo)
|
|
;
|
|
GoalExpr0 = conj(ConjType, SubGoals0),
|
|
(
|
|
ConjType = plain_conj,
|
|
(
|
|
SubGoals0 = [],
|
|
Goal = Goal0,
|
|
FoundDeconstruct = before_deconstruct
|
|
;
|
|
SubGoals0 = [_ | _],
|
|
conj_find_bind_var(Var, ProcessUnify, SubGoals0, SubGoals,
|
|
!Subst, !Result, !Info, FoundDeconstruct),
|
|
Goal = hlds_goal(conj(ConjType, SubGoals), GoalInfo)
|
|
)
|
|
;
|
|
ConjType = parallel_conj,
|
|
Goal = Goal0,
|
|
FoundDeconstruct = given_up_search
|
|
)
|
|
;
|
|
GoalExpr0 = unify(LHS, RHS, _, UnifyInfo0, _),
|
|
(
|
|
% Check whether the unification is a deconstruction unification
|
|
% on either Var or on a variable aliased to Var.
|
|
UnifyInfo0 = deconstruct(UnifyVar, _, _, _, _, _),
|
|
term.apply_rec_substitution(term.variable(Var, context_init),
|
|
!.Subst, term.variable(SubstVar, context_init)),
|
|
term.apply_rec_substitution(term.variable(UnifyVar, context_init),
|
|
!.Subst, term.variable(SubstUnifyVar, context_init)),
|
|
SubstVar = SubstUnifyVar
|
|
->
|
|
call(ProcessUnify, Var, Goal0, Goals, !Result, !Info),
|
|
conj_list_to_goal(Goals, GoalInfo, Goal),
|
|
FoundDeconstruct = found_deconstruct
|
|
;
|
|
Goal = Goal0,
|
|
FoundDeconstruct = before_deconstruct,
|
|
% Otherwise abstractly interpret the unification.
|
|
( interpret_unify(LHS, RHS, !.Subst, NewSubst) ->
|
|
!:Subst = NewSubst
|
|
;
|
|
% The unification must fail - just ignore it.
|
|
true
|
|
)
|
|
)
|
|
;
|
|
( GoalExpr0 = plain_call(_, _, _, _, _, _)
|
|
; GoalExpr0 = generic_call(_, _, _, _)
|
|
; GoalExpr0 = call_foreign_proc(_, _, _, _, _, _, _)
|
|
; GoalExpr0 = disj(_)
|
|
; GoalExpr0 = switch(_, _, _)
|
|
; GoalExpr0 = negation(_)
|
|
; GoalExpr0 = if_then_else(_, _, _, _)
|
|
),
|
|
Goal = Goal0,
|
|
( goal_info_has_feature(GoalInfo, feature_from_head) ->
|
|
FoundDeconstruct = before_deconstruct
|
|
;
|
|
FoundDeconstruct = given_up_search
|
|
)
|
|
;
|
|
GoalExpr0 = shorthand(_),
|
|
unexpected(this_file, "find_bind_var_2: shorthand")
|
|
).
|
|
|
|
:- pred conj_find_bind_var(prog_var::in,
|
|
process_unify(Result, Info)::in(process_unify),
|
|
list(hlds_goal)::in, list(hlds_goal)::out,
|
|
prog_substitution::in, prog_substitution::out, Result::in, Result::out,
|
|
Info::in, Info::out, deconstruct_search::out) is det.
|
|
|
|
conj_find_bind_var(_Var, _, [], [], !Subst, !Result, !Info,
|
|
before_deconstruct).
|
|
conj_find_bind_var(Var, ProcessUnify, [Goal0 | Goals0], [Goal | Goals],
|
|
!Subst, !Result, !Info, FoundDeconstruct) :-
|
|
find_bind_var_2(Var, ProcessUnify, Goal0, Goal, !Subst,
|
|
!Result, !Info, FoundDeconstruct1),
|
|
(
|
|
FoundDeconstruct1 = before_deconstruct,
|
|
conj_find_bind_var(Var, ProcessUnify, Goals0, Goals,
|
|
!Subst, !Result, !Info, FoundDeconstruct)
|
|
;
|
|
( FoundDeconstruct1 = found_deconstruct
|
|
; FoundDeconstruct1 = given_up_search
|
|
),
|
|
FoundDeconstruct = FoundDeconstruct1,
|
|
Goals = Goals0
|
|
).
|
|
|
|
%-----------------------------------------------------------------------------%
|
|
|
|
:- pred cases_to_switch(sorted_case_list::in, prog_var::in, vartypes::in,
|
|
hlds_goal_info::in, instmap::in, module_info::in, hlds_goal_expr::out,
|
|
bool::in, bool::out) is det.
|
|
|
|
cases_to_switch(CasesList, Var, VarTypes, _GoalInfo, InstMap, ModuleInfo,
|
|
Goal, !Requant) :-
|
|
instmap.lookup_var(InstMap, Var, VarInst),
|
|
( inst_is_bound_to_functors(ModuleInfo, VarInst, Functors) ->
|
|
functors_to_cons_ids(Functors, ConsIds0),
|
|
list.sort(ConsIds0, ConsIds),
|
|
delete_unreachable_cases(CasesList, ConsIds, CasesList1),
|
|
( list.same_length(Functors, CasesList1) ->
|
|
CanFail = cannot_fail
|
|
;
|
|
CanFail = can_fail
|
|
)
|
|
;
|
|
map.lookup(VarTypes, Var, Type),
|
|
CasesList1 = CasesList,
|
|
( switch_covers_all_cases(ModuleInfo, Type, CasesList1) ->
|
|
CanFail = cannot_fail
|
|
;
|
|
CanFail = can_fail
|
|
)
|
|
),
|
|
detect_switches_in_cases(ModuleInfo, VarTypes, InstMap,
|
|
CasesList1, Cases, !Requant),
|
|
|
|
% We turn switches with no arms into fail, since this avoids having
|
|
% the code generator flush the control variable of the switch.
|
|
% We can't easily eliminate switches with one arm, since the
|
|
% code of the arm will have the unification between the variable
|
|
% and the function symbol as det. The gain would be minimal to
|
|
% nonexistent anyway.
|
|
(
|
|
Cases = [],
|
|
Goal = disj([])
|
|
;
|
|
Cases = [_ | _],
|
|
Goal = switch(Var, CanFail, Cases)
|
|
).
|
|
|
|
% Check whether a switch handles all the possible constants/functors
|
|
% for the type.
|
|
%
|
|
:- pred switch_covers_all_cases(module_info::in, mer_type::in,
|
|
sorted_case_list::in) is semidet.
|
|
|
|
switch_covers_all_cases(ModuleInfo, Type, CasesList) :-
|
|
switch_type_num_functors(ModuleInfo, Type, NumFunctors),
|
|
list.length(CasesList, NumCases),
|
|
NumCases = NumFunctors.
|
|
|
|
% Convert the assoc_list(cons_id, list(hlds_goal)) back into a plain
|
|
% list(case).
|
|
%
|
|
:- pred fix_case_list(assoc_list(cons_id, list(hlds_goal))::in,
|
|
hlds_goal_info::in, list(case)::out) is det.
|
|
|
|
fix_case_list([], _, []).
|
|
fix_case_list([Functor - DisjList0 | Cases0], GoalInfo,
|
|
[case(Functor, Goal) | Cases]) :-
|
|
% We need to put the list back the right way around.
|
|
list.reverse(DisjList0, DisjList),
|
|
disj_list_to_goal(DisjList, GoalInfo, Goal),
|
|
fix_case_list(Cases0, GoalInfo, Cases).
|
|
|
|
%-----------------------------------------------------------------------------%
|
|
|
|
:- func this_file = string.
|
|
|
|
this_file = "switch_detection.m".
|
|
|
|
%-----------------------------------------------------------------------------%
|