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mercury/compiler/cse_detection.m
Zoltan Somogyi 77a6a6c10c Implement several more changes that together speed up compilation time 
Estimated hours taken: 16
Branches: main

Implement several more changes that together speed up compilation time
on training_cars_full by 12%, and also improve tools/speedtest -h by 7.2%
and tools/speedtest by 1.6%.

The first change is designed to eliminate the time that the compiler spends
constructing error messages that are then ignored. The working predicates of
prog_io_sym_name used to always return a single result, which either gave
a description of the thing being looked, or an error message. However,
in many places, the caller did not consider not finding the thing being looked
for to be an error, and thus threw away the error message, keeping only
the "not found" indication. For each predicate with such callers, this diff
provides a parallel predicate that indicates "not found" simply by failing.
This allows us to eliminate the construction of the error message, the
preparation for the construction of the error message (usually by describing
the context), and the construction of the "ok" wrapper.

The second change is to specialize the handling of from_ground_term_construct
scopes in the termination analyzer. To make this easier, I also cleaned up
of the infrastructure of the termination analyzer.

The third change is to avoid traversing from_ground_term_construct scopes
in quantification.m when finding the variables in a goal, since termination
analysis no longer needs the information it gathers.

The fourth change is to avoid traversing second and later conjuncts in
conjunctions twice. The first step in handling conjunctions is to call
implicitly_quantify_conj, which builds up a data structure that pairs each
conjunct with the variables that occur free in all the conjuncts following it.
However, after this was done and each conjunct was annotated with its
nonlocals, we used to compute the variables that occur free in the conjunction
as a whole from scratch. This diff changes the code so that we now compute that
set based on the information we gathered earlier, avoiding a redundant
traversal.

The fifth change is to create specialized, lower-arity versions of many of
the predicates in quantification.m. These versions are intended for traversals
that take place after the compiler has replaced lambda expressions with
references to separate procedures. These traversals do not need to pass around
arguments representing the variables occurring free in the (now non-existent)
lambda expressions.

compiler/prog_io_sym_name.m:
	Make the first change described above.

	Change some predicate names to adopt a consistent naming scheme
	in which predicates that do the same job and differ only in how they
	handle errors have names that differ only in a "try_" prefix.

	Add some predicate versions that do common tests on the output
	of the base versions. For example, try_parse_sym_name_and_no_args
	is a version of try_parse_sym_name_and_args that insists on finding
	an empty argument list.

	Remove the unused "error term" argument that we used to need a while
	ago.

	Move some predicate definitions to make their order match the order of
	their declarations.

	Turn a predicate into a function for its caller's convenience.

compiler/term_constr_build.m:
	Make the second change described above by modeling each
	from_ground_term_construct scope as a single unification,
	assigning the total size of the ground term to the variable being
	built.

compiler/term_constr_util.m:
	Put the arguments of some predicates into a more standard order.

compiler/lp_rational.m:
	Change the names of some function symbols to avoid both the use of
	graphic characters that require quoting and clashes with other types.

	Change the names of some predicates to make their purpose clear,
	and to avoid ambiguity.

compiler/quantification.m:
	Make the third, fourth and fifth changes described above.

compiler/*.m:
	Conform to the changes above.
2009-09-08 02:43:41 +00:00

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%-----------------------------------------------------------------------------%
% vim: ft=mercury ts=4 sw=4 et
%-----------------------------------------------------------------------------%
% Copyright (C) 1995-2009 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: cse_detection.m.
% Main author: zs.
% Much of the code is based on switch_detection.m by fjh.
%
% Common subexpression detection - hoist common subexpression goals out of
% branched structures. This can enable us to find more indexing opportunities
% and hence can make the code more deterministic.
% This code is switched on/off with the `--common-goal' option.
%
%-----------------------------------------------------------------------------%
:- module check_hlds.cse_detection.
:- interface.
:- import_module hlds.
:- import_module hlds.hlds_module.
:- import_module hlds.hlds_pred.
:- pred detect_cse_in_module(module_info::in, module_info::out) is det.
:- pred detect_cse_in_proc(proc_id::in, pred_id::in,
module_info::in, module_info::out) is det.
%-----------------------------------------------------------------------------%
%-----------------------------------------------------------------------------%
:- implementation.
:- import_module check_hlds.inst_match.
:- import_module check_hlds.modes.
:- import_module check_hlds.switch_detection.
:- import_module check_hlds.switch_detection.
:- import_module check_hlds.type_util.
:- import_module hlds.goal_util.
:- import_module hlds.hlds_goal.
:- import_module hlds.hlds_out.
:- import_module hlds.hlds_rtti.
:- import_module hlds.instmap.
:- import_module hlds.quantification.
:- import_module libs.
:- import_module libs.compiler_util.
:- import_module libs.file_util.
:- import_module libs.globals.
:- import_module libs.options.
:- import_module parse_tree.
:- import_module parse_tree.error_util.
:- import_module parse_tree.prog_data.
:- import_module parse_tree.prog_type_subst.
:- import_module assoc_list.
:- import_module bool.
:- import_module int.
:- import_module io.
:- import_module list.
:- import_module map.
:- import_module maybe.
:- import_module pair.
:- import_module set.
:- import_module string.
:- import_module svmap.
:- import_module term.
:- import_module varset.
%-----------------------------------------------------------------------------%
detect_cse_in_module(!ModuleInfo) :-
% Traverse the module structure, calling `detect_cse_in_goal'
% for each procedure body.
module_info_predids(PredIds, !ModuleInfo),
detect_cse_in_preds(PredIds, !ModuleInfo).
:- pred detect_cse_in_preds(list(pred_id)::in,
module_info::in, module_info::out) is det.
detect_cse_in_preds([], !ModuleInfo).
detect_cse_in_preds([PredId | PredIds], !ModuleInfo) :-
module_info_preds(!.ModuleInfo, PredTable),
map.lookup(PredTable, PredId, PredInfo),
detect_cse_in_pred(PredId, PredInfo, !ModuleInfo),
detect_cse_in_preds(PredIds, !ModuleInfo).
:- pred detect_cse_in_pred(pred_id::in, pred_info::in,
module_info::in, module_info::out) is det.
detect_cse_in_pred(PredId, PredInfo, !ModuleInfo) :-
ProcIds = pred_info_non_imported_procids(PredInfo),
detect_cse_in_procs(ProcIds, PredId, !ModuleInfo).
:- pred detect_cse_in_procs(list(proc_id)::in, pred_id::in,
module_info::in, module_info::out) is det.
detect_cse_in_procs([], _PredId, !ModuleInfo).
detect_cse_in_procs([ProcId | ProcIds], PredId, !ModuleInfo) :-
detect_cse_in_proc(ProcId, PredId, !ModuleInfo),
detect_cse_in_procs(ProcIds, PredId, !ModuleInfo).
detect_cse_in_proc(ProcId, PredId, !ModuleInfo) :-
module_info_get_globals(!.ModuleInfo, Globals),
globals.lookup_bool_option(Globals, very_verbose, VeryVerbose),
(
VeryVerbose = yes,
trace [io(!IO)] (
io.write_string("% Detecting common deconstructions for ", !IO),
hlds_out.write_pred_id(!.ModuleInfo, PredId, !IO),
io.write_string("\n", !IO)
)
;
VeryVerbose = no
),
detect_cse_in_proc_pass(ProcId, PredId, Redo, !ModuleInfo),
globals.lookup_bool_option(Globals, detailed_statistics, Statistics),
trace [io(!IO)] (
maybe_report_stats(Statistics, !IO)
),
(
Redo = no
;
Redo = yes,
(
VeryVerbose = yes,
trace [io(!IO)] (
io.write_string("% Repeating mode check for ", !IO),
hlds_out.write_pred_id(!.ModuleInfo, PredId, !IO),
io.write_string("\n", !IO)
)
;
VeryVerbose = no
),
modecheck_proc(ProcId, PredId, !ModuleInfo, ModeSpecs, _Changed),
trace [io(!IO)] (
maybe_report_stats(Statistics, !IO)
),
ContainsErrors = contains_errors(Globals, ModeSpecs),
(
ContainsErrors = yes,
unexpected(this_file, "mode check fails when repeated")
;
ContainsErrors = no
% There is no point in returning any warnings and/or informational
% messages to our caller, since any such messages should already
% have been gathered during the initial mode analysis pass.
),
(
VeryVerbose = yes,
trace [io(!IO)] (
io.write_string("% Repeating switch detection for ", !IO),
hlds_out.write_pred_id(!.ModuleInfo, PredId, !IO),
io.write_string("\n", !IO)
)
;
VeryVerbose = no
),
detect_switches_in_proc(ProcId, PredId, !ModuleInfo),
trace [io(!IO)] (
maybe_report_stats(Statistics, !IO)
),
(
VeryVerbose = yes,
trace [io(!IO)] (
io.write_string("% Repeating common " ++
"deconstruction detection for ", !IO),
hlds_out.write_pred_id(!.ModuleInfo, PredId, !IO),
io.write_string("\n", !IO)
)
;
VeryVerbose = no
),
detect_cse_in_proc(ProcId, PredId, !ModuleInfo)
).
:- type cse_info
---> cse_info(
csei_varset :: prog_varset,
csei_vartypes :: vartypes,
csei_rtti_varmaps :: rtti_varmaps,
csei_module_info :: module_info
).
:- pred detect_cse_in_proc_pass(proc_id::in, pred_id::in, bool::out,
module_info::in, module_info::out) is det.
detect_cse_in_proc_pass(ProcId, PredId, Redo, ModuleInfo0, ModuleInfo) :-
module_info_preds(ModuleInfo0, PredTable0),
map.lookup(PredTable0, PredId, PredInfo0),
pred_info_get_procedures(PredInfo0, ProcTable0),
map.lookup(ProcTable0, ProcId, ProcInfo0),
% To process each ProcInfo, we get the goal, initialize the instmap
% based on the modes of the head vars, and pass these to
% `detect_cse_in_goal'.
proc_info_get_goal(ProcInfo0, Goal0),
proc_info_get_initial_instmap(ProcInfo0, ModuleInfo0, InstMap0),
proc_info_get_varset(ProcInfo0, Varset0),
proc_info_get_vartypes(ProcInfo0, VarTypes0),
proc_info_get_rtti_varmaps(ProcInfo0, RttiVarMaps0),
CseInfo0 = cse_info(Varset0, VarTypes0, RttiVarMaps0, ModuleInfo0),
detect_cse_in_goal(Goal0, Goal1, CseInfo0, CseInfo, InstMap0, Redo),
(
Redo = no,
ModuleInfo = ModuleInfo0
;
Redo = yes,
% ModuleInfo should not be changed by detect_cse_in_goal.
CseInfo = cse_info(VarSet1, VarTypes1, RttiVarMaps1, _),
proc_info_get_headvars(ProcInfo0, HeadVars),
implicitly_quantify_clause_body_general(
ordinary_nonlocals_maybe_lambda,
HeadVars, _Warnings,
Goal1, Goal, VarSet1, VarSet, VarTypes1, VarTypes,
RttiVarMaps1, RttiVarMaps),
proc_info_set_goal(Goal, ProcInfo0, ProcInfo1),
proc_info_set_varset(VarSet, ProcInfo1, ProcInfo2),
proc_info_set_vartypes(VarTypes, ProcInfo2, ProcInfo3),
proc_info_set_rtti_varmaps(RttiVarMaps, ProcInfo3, ProcInfo),
map.det_update(ProcTable0, ProcId, ProcInfo, ProcTable),
pred_info_set_procedures(ProcTable, PredInfo0, PredInfo),
map.det_update(PredTable0, PredId, PredInfo, PredTable),
module_info_set_preds(PredTable, ModuleInfo0, ModuleInfo)
).
%-----------------------------------------------------------------------------%
% Given a goal, and the instmap on entry to that goal,
% find disjunctions that contain common subexpressions
% and hoist these out of the disjunction. At the moment
% we only look for cses that are deconstruction unifications.
%
:- pred detect_cse_in_goal(hlds_goal::in, hlds_goal::out,
cse_info::in, cse_info::out, instmap::in, bool::out) is det.
detect_cse_in_goal(Goal0, Goal, !CseInfo, InstMap0, Redo) :-
detect_cse_in_goal_update_instmap(Goal0, Goal, !CseInfo,
InstMap0, _InstMap, Redo).
% This version is the same as the above except that it returns
% the resulting instmap on exit from the goal, which is computed by
% applying the instmap delta specified in the goal's goalinfo.
%
:- pred detect_cse_in_goal_update_instmap(hlds_goal::in, hlds_goal::out,
cse_info::in, cse_info::out, instmap::in, instmap::out, bool::out) is det.
detect_cse_in_goal_update_instmap(Goal0, Goal, !CseInfo, InstMap0, InstMap,
Redo) :-
Goal0 = hlds_goal(GoalExpr0, GoalInfo),
detect_cse_in_goal_expr(GoalExpr0, GoalExpr, !CseInfo, GoalInfo,
InstMap0, Redo),
Goal = hlds_goal(GoalExpr, GoalInfo),
InstMapDelta = goal_info_get_instmap_delta(GoalInfo),
instmap.apply_instmap_delta(InstMap0, InstMapDelta, InstMap).
% Here we process each of the different sorts of goals.
%
:- pred detect_cse_in_goal_expr(hlds_goal_expr::in, hlds_goal_expr::out,
cse_info::in, cse_info::out, hlds_goal_info::in,
instmap::in, bool::out) is det.
detect_cse_in_goal_expr(GoalExpr0, GoalExpr, !CseInfo, GoalInfo, InstMap0,
Redo) :-
(
( GoalExpr0 = call_foreign_proc(_, _, _, _, _, _, _)
; GoalExpr0 = generic_call(_, _, _, _)
; GoalExpr0 = plain_call(_, _, _, _, _, _)
),
GoalExpr = GoalExpr0,
Redo = no
;
GoalExpr0 = unify(LHS, RHS0, Mode, Unify, UnifyContext),
(
RHS0 = rhs_lambda_goal(Purity, Groundness, PredOrFunc, EvalMethod,
NonLocalVars, Vars, Modes, Det, LambdaGoal0),
ModuleInfo = !.CseInfo ^ csei_module_info,
instmap.pre_lambda_update(ModuleInfo, Vars, Modes,
InstMap0, InstMap1),
detect_cse_in_goal(LambdaGoal0, LambdaGoal, !CseInfo,
InstMap1, Redo),
RHS = rhs_lambda_goal(Purity, Groundness, PredOrFunc, EvalMethod,
NonLocalVars, Vars, Modes, Det, LambdaGoal)
;
( RHS0 = rhs_var(_)
; RHS0 = rhs_functor(_, _, _)
),
RHS = RHS0,
Redo = no
),
GoalExpr = unify(LHS, RHS, Mode,Unify, UnifyContext)
;
GoalExpr0 = negation(SubGoal0),
detect_cse_in_goal(SubGoal0, SubGoal, !CseInfo, InstMap0, Redo),
GoalExpr = negation(SubGoal)
;
GoalExpr0 = scope(Reason, SubGoal0),
( Reason = from_ground_term(_, from_ground_term_construct) ->
% There are no deconstructions at all inside these scopes.
GoalExpr = GoalExpr0,
Redo = no
;
detect_cse_in_goal(SubGoal0, SubGoal, !CseInfo, InstMap0, Redo),
GoalExpr = scope(Reason, SubGoal)
)
;
GoalExpr0 = conj(ConjType, Goals0),
detect_cse_in_conj(Goals0, Goals, !CseInfo, ConjType, InstMap0, Redo),
GoalExpr = conj(ConjType, Goals)
;
GoalExpr0 = disj(Goals0),
(
Goals0 = [],
Redo = no,
GoalExpr = disj([])
;
Goals0 = [_ | _],
NonLocals = goal_info_get_nonlocals(GoalInfo),
set.to_sorted_list(NonLocals, NonLocalsList),
detect_cse_in_disj(NonLocalsList, Goals0, GoalInfo,
InstMap0, !CseInfo, Redo, GoalExpr)
)
;
GoalExpr0 = switch(Var, CanFail, Cases0),
NonLocals = goal_info_get_nonlocals(GoalInfo),
set.to_sorted_list(NonLocals, NonLocalsList),
detect_cse_in_cases(NonLocalsList, Var, CanFail, Cases0, GoalInfo,
InstMap0, !CseInfo, Redo, GoalExpr)
;
GoalExpr0 = if_then_else(Vars, Cond0, Then0, Else0),
NonLocals = goal_info_get_nonlocals(GoalInfo),
set.to_sorted_list(NonLocals, NonLocalsList),
detect_cse_in_ite(NonLocalsList, Vars, Cond0, Then0, Else0, GoalInfo,
InstMap0, !CseInfo, Redo, GoalExpr)
;
GoalExpr0 = shorthand(ShortHand0),
(
ShortHand0 = atomic_goal(AtomicGoalType, Outer, Inner,
MaybeOutputVars, MainGoal0, OrElseGoals0, OrElseInners),
detect_cse_in_goal(MainGoal0, MainGoal, !CseInfo, InstMap0, Redo1),
detect_cse_in_independent_goals(OrElseGoals0, OrElseGoals,
!CseInfo, InstMap0, Redo2),
ShortHand = atomic_goal(AtomicGoalType, Outer, Inner,
MaybeOutputVars, MainGoal, OrElseGoals, OrElseInners),
bool.or(Redo1, Redo2, Redo)
;
ShortHand0 = bi_implication(_, _),
% These should have been expanded out by now.
unexpected(this_file, "detect_cse_in_goal_expr: bi_implication")
;
ShortHand0 = try_goal(MaybeIO, ResultVar, SubGoal0),
% XXX not sure about this as SubGoal0 is not in its final form.
% Also, mightn't the try "Goal" part get hoisted out?
detect_cse_in_goal(SubGoal0, SubGoal, !CseInfo, InstMap0, Redo),
ShortHand = try_goal(MaybeIO, ResultVar, SubGoal)
),
GoalExpr = shorthand(ShortHand)
).
%-----------------------------------------------------------------------------%
:- pred detect_cse_in_conj(list(hlds_goal)::in, list(hlds_goal)::out,
cse_info::in, cse_info::out, conj_type::in, instmap::in, bool::out) is det.
detect_cse_in_conj([], [], !CseInfo, _ConjType, _InstMap, no).
detect_cse_in_conj([Goal0 | Goals0], Goals, !CseInfo, ConjType, !.InstMap,
Redo) :-
detect_cse_in_goal_update_instmap(Goal0, Goal, !CseInfo, !InstMap, Redo1),
detect_cse_in_conj(Goals0, TailGoals, !CseInfo, ConjType, !.InstMap,
Redo2),
% Flatten any non-flat conjunctions we create.
(
Goal = hlds_goal(conj(InnerConjType, ConjGoals), _),
ConjType = InnerConjType
->
Goals = ConjGoals ++ TailGoals
;
Goals = [Goal | TailGoals]
),
bool.or(Redo1, Redo2, Redo).
%-----------------------------------------------------------------------------%
% These are the interesting bits - we've found a non-empty branched
% structure, and we've got a list of the non-local variables of that
% structure. Now for each non-local variable, we check whether each
% branch matches that variable against the same functor.
%
:- pred detect_cse_in_disj(list(prog_var)::in, list(hlds_goal)::in,
hlds_goal_info::in, instmap::in, cse_info::in,
cse_info::out, bool::out, hlds_goal_expr::out) is det.
detect_cse_in_disj([], Goals0, _, InstMap, !CseInfo, Redo, disj(Goals)) :-
detect_cse_in_independent_goals(Goals0, Goals, !CseInfo, InstMap, Redo).
detect_cse_in_disj([Var | Vars], Goals0, GoalInfo0, InstMap0,
!CseInfo, Redo, GoalExpr) :-
(
instmap_lookup_var(InstMap0, Var, VarInst0),
ModuleInfo = !.CseInfo ^ csei_module_info,
% XXX We only need inst_is_bound, but leave this as it is until
% mode analysis can handle aliasing between free variables.
inst_is_ground_or_any(ModuleInfo, VarInst0),
common_deconstruct(Goals0, Var, !CseInfo, Unify,
FirstOldNew, LaterOldNew, Goals)
->
maybe_update_existential_data_structures(Unify,
FirstOldNew, LaterOldNew, !CseInfo),
GoalExpr = conj(plain_conj,
[Unify, hlds_goal(disj(Goals), GoalInfo0)]),
Redo = yes
;
detect_cse_in_disj(Vars, Goals0, GoalInfo0, InstMap0,
!CseInfo, Redo, GoalExpr)
).
:- pred detect_cse_in_independent_goals(
list(hlds_goal)::in, list(hlds_goal)::out,
cse_info::in, cse_info::out, instmap::in, bool::out) is det.
detect_cse_in_independent_goals([], [], !CseInfo, _, no).
detect_cse_in_independent_goals([Goal0 | Goals0], [Goal | Goals], !CseInfo,
InstMap0, Redo) :-
detect_cse_in_goal(Goal0, Goal, !CseInfo, InstMap0, Redo1),
detect_cse_in_independent_goals(Goals0, Goals, !CseInfo, InstMap0, Redo2),
bool.or(Redo1, Redo2, Redo).
:- pred detect_cse_in_cases(list(prog_var)::in, prog_var::in, can_fail::in,
list(case)::in, hlds_goal_info::in, instmap::in,
cse_info::in, cse_info::out, bool::out, hlds_goal_expr::out) is det.
detect_cse_in_cases([], SwitchVar, CanFail, Cases0, _GoalInfo, InstMap0,
!CseInfo, Redo, switch(SwitchVar, CanFail, Cases)) :-
detect_cse_in_cases_arms(Cases0, Cases, !CseInfo, InstMap0, Redo).
detect_cse_in_cases([Var | Vars], SwitchVar, CanFail, Cases0, GoalInfo,
InstMap0, !CseInfo, Redo, GoalExpr) :-
(
Var \= SwitchVar,
instmap_lookup_var(InstMap0, Var, VarInst0),
ModuleInfo = !.CseInfo ^ csei_module_info,
% XXX We only need inst_is_bound, but leave this as it is until
% mode analysis can handle aliasing between free variables.
inst_is_ground_or_any(ModuleInfo, VarInst0),
common_deconstruct_cases(Cases0, Var, !CseInfo,
Unify, FirstOldNew, LaterOldNew, Cases)
->
maybe_update_existential_data_structures(Unify,
FirstOldNew, LaterOldNew, !CseInfo),
GoalExpr = conj(plain_conj,
[Unify, hlds_goal(switch(SwitchVar, CanFail, Cases), GoalInfo)]),
Redo = yes
;
detect_cse_in_cases(Vars, SwitchVar, CanFail, Cases0, GoalInfo,
InstMap0, !CseInfo, Redo, GoalExpr)
).
:- pred detect_cse_in_cases_arms(list(case)::in, list(case)::out,
cse_info::in, cse_info::out, instmap::in, bool::out) is det.
detect_cse_in_cases_arms([], [], !CseInfo, _, no).
detect_cse_in_cases_arms([Case0 | Cases0], [Case | Cases], !CseInfo, InstMap0,
Redo) :-
Case0 = case(MainConsId, OtherConsIds, Goal0),
detect_cse_in_goal(Goal0, Goal, !CseInfo, InstMap0, Redo1),
Case = case(MainConsId, OtherConsIds, Goal),
detect_cse_in_cases_arms(Cases0, Cases, !CseInfo, InstMap0, Redo2),
bool.or(Redo1, Redo2, Redo).
:- pred detect_cse_in_ite(list(prog_var)::in, list(prog_var)::in,
hlds_goal::in, hlds_goal::in, hlds_goal::in, hlds_goal_info::in,
instmap::in, cse_info::in, cse_info::out, bool::out,
hlds_goal_expr::out) is det.
detect_cse_in_ite([], IfVars, Cond0, Then0, Else0, _, InstMap, !CseInfo,
Redo, if_then_else(IfVars, Cond, Then, Else)) :-
detect_cse_in_ite_arms(Cond0, Cond, Then0, Then, Else0, Else, !CseInfo,
InstMap, Redo).
detect_cse_in_ite([Var | Vars], IfVars, Cond0, Then0, Else0, GoalInfo,
InstMap, !CseInfo, Redo, GoalExpr) :-
(
ModuleInfo = !.CseInfo ^ csei_module_info,
instmap_lookup_var(InstMap, Var, VarInst0),
% XXX We only need inst_is_bound, but leave this as it is until
% mode analysis can handle aliasing between free variables.
inst_is_ground_or_any(ModuleInfo, VarInst0),
common_deconstruct([Then0, Else0], Var, !CseInfo,
Unify, FirstOldNew, LaterOldNew, Goals),
Goals = [Then, Else]
->
maybe_update_existential_data_structures(Unify,
FirstOldNew, LaterOldNew, !CseInfo),
IfGoal = hlds_goal(if_then_else(IfVars, Cond0, Then, Else), GoalInfo),
GoalExpr = conj(plain_conj, [Unify, IfGoal]),
Redo = yes
;
detect_cse_in_ite(Vars, IfVars, Cond0, Then0, Else0, GoalInfo,
InstMap, !CseInfo, Redo, GoalExpr)
).
:- pred detect_cse_in_ite_arms(hlds_goal::in, hlds_goal::out,
hlds_goal::in, hlds_goal::out, hlds_goal::in, hlds_goal::out,
cse_info::in, cse_info::out, instmap::in, bool::out) is det.
detect_cse_in_ite_arms(Cond0, Cond, Then0, Then, Else0, Else, !CseInfo,
InstMap0, Redo) :-
detect_cse_in_goal_update_instmap(Cond0, Cond, !CseInfo,
InstMap0, InstMap1, Redo1),
detect_cse_in_goal(Then0, Then, !CseInfo, InstMap1, Redo2),
detect_cse_in_goal(Else0, Else, !CseInfo, InstMap0, Redo3),
bool.or(Redo1, Redo2, Redo12),
bool.or(Redo12, Redo3, Redo).
%-----------------------------------------------------------------------------%
% common_deconstruct(Goals0, Var, !CseInfo, Unify, Goals):
% input vars:
% Goals0 is a list of parallel goals in a branched structure
% (disjunction, if-then-else, or switch).
% Var is the variable we are looking for a common deconstruction on.
% !.CseInfo contains the original varset and type map.
% output vars:
% !:CseInfo has a varset and a type map reflecting the new variables
% we have introduced.
% Goals is the modified version of Goals0 after the common deconstruction
% has been hoisted out, with the new variables as the functor arguments.
% Unify is the unification that was hoisted out.
%
:- pred common_deconstruct(list(hlds_goal)::in, prog_var::in, cse_info::in,
cse_info::out, hlds_goal::out, assoc_list(prog_var)::out,
list(assoc_list(prog_var))::out, list(hlds_goal)::out) is semidet.
common_deconstruct(Goals0, Var, !CseInfo, Unify, FirstOldNew, LaterOldNew,
Goals) :-
common_deconstruct_2(Goals0, Var, before_candidate,
have_candidate(Unify, FirstOldNew, LaterOldNew), !CseInfo, Goals),
LaterOldNew = [_ | _].
:- pred common_deconstruct_2(list(hlds_goal)::in, prog_var::in,
cse_state::in, cse_state::out, cse_info::in, cse_info::out,
list(hlds_goal)::out) is semidet.
common_deconstruct_2([], _Var, !CseState, !CseInfo, []).
common_deconstruct_2([Goal0 | Goals0], Var, !CseState, !CseInfo,
[Goal | Goals]) :-
find_bind_var(Var, find_bind_var_for_cse_in_deconstruct, Goal0, Goal,
!CseState, !CseInfo, did_find_deconstruct),
!.CseState = have_candidate(_, _, _),
common_deconstruct_2(Goals0, Var, !CseState, !CseInfo, Goals).
%-----------------------------------------------------------------------------%
:- pred common_deconstruct_cases(list(case)::in, prog_var::in,
cse_info::in, cse_info::out, hlds_goal::out, assoc_list(prog_var)::out,
list(assoc_list(prog_var))::out, list(case)::out) is semidet.
common_deconstruct_cases(Cases0, Var, !CseInfo, Unify,
FirstOldNew, LaterOldNew, Cases) :-
common_deconstruct_cases_2(Cases0, Var, before_candidate,
have_candidate(Unify, FirstOldNew, LaterOldNew), !CseInfo, Cases),
LaterOldNew = [_ | _].
:- pred common_deconstruct_cases_2(list(case)::in, prog_var::in,
cse_state::in, cse_state::out, cse_info::in, cse_info::out,
list(case)::out) is semidet.
common_deconstruct_cases_2([], _Var, !CseState, !CseInfo, []).
common_deconstruct_cases_2([Case0 | Cases0], Var, !CseState, !CseInfo,
[Case | Cases]) :-
Case0 = case(MainConsId, OtherConsIds, Goal0),
find_bind_var(Var, find_bind_var_for_cse_in_deconstruct, Goal0, Goal,
!CseState, !CseInfo, did_find_deconstruct),
Case = case(MainConsId, OtherConsIds, Goal),
!.CseState = have_candidate(_, _, _),
common_deconstruct_cases_2(Cases0, Var, !CseState, !CseInfo, Cases).
%-----------------------------------------------------------------------------%
% This data structure represents the state of the search for
% deconstructions in all the branches of a branched control structure
% that deconstruct a given variable with the same functor.
% Initially, we don't know what unification we will hoist out, so the
% state is before_candidate. When we find a unification we want to
% hoist out, this fixes the functor, and the state is have_candidate.
% If we find that some branches unify that variable with some other
% functor, we have multiple_candidates, which means that we don't hoist
% out any of them. (Although our caller may try again with another
% variable.)
%
% The goal field contains the unification we are proposing to put
% before the branched control structure. The first_old_new field
% gives the mapping from argument variables in the old unification
% in the first branch to the freshly created variables in the goal
% being hoisted before the branched control structure. The
% later_old_new field contains the same information for the second
% and later branches.
:- type cse_state
---> before_candidate
; have_candidate(
goal :: hlds_goal,
first_old_new :: assoc_list(prog_var),
later_old_new :: list(assoc_list(prog_var))
)
; multiple_candidates.
:- pred find_bind_var_for_cse_in_deconstruct(prog_var::in, hlds_goal::in,
list(hlds_goal)::out, cse_state::in, cse_state::out,
cse_info::in, cse_info::out) is det.
find_bind_var_for_cse_in_deconstruct(Var, Goal0, Goals,
!CseState, !CseInfo) :-
(
!.CseState = before_candidate,
construct_common_unify(Var, Goal0, !CseInfo, OldNewVars,
HoistedGoal, Goals),
!:CseState = have_candidate(HoistedGoal, OldNewVars, [])
;
!.CseState = have_candidate(HoistedGoal,
FirstOldNewVars, LaterOldNewVars0),
Goal0 = hlds_goal(_, GoalInfo),
Context = goal_info_get_context(GoalInfo),
(
find_similar_deconstruct(HoistedGoal,
Goal0, Context, OldNewVars, Goals0)
->
Goals = Goals0,
LaterOldNewVars = [OldNewVars | LaterOldNewVars0],
!:CseState = have_candidate(HoistedGoal,
FirstOldNewVars, LaterOldNewVars)
;
Goals = [Goal0],
!:CseState = multiple_candidates
)
;
!.CseState = multiple_candidates,
Goals = [Goal0],
!:CseState = multiple_candidates
).
:- pred construct_common_unify(prog_var::in, hlds_goal::in,
cse_info::in, cse_info::out, assoc_list(prog_var)::out,
hlds_goal::out, list(hlds_goal)::out) is det.
construct_common_unify(Var, hlds_goal(GoalExpr0, GoalInfo), !CseInfo,
OldNewVars, HoistedGoal, Replacements) :-
(
GoalExpr0 = unify(_, RHS, Umode, Unif0, Ucontext),
Unif0 = deconstruct(_, Consid, Args, Submodes, CanFail, CanCGC)
->
Unif = deconstruct(Var, Consid, Args, Submodes, CanFail, CanCGC),
(
RHS = rhs_functor(_, _, _),
GoalExpr1 = unify(Var, RHS, Umode, Unif, Ucontext)
;
( RHS = rhs_var(_)
; RHS = rhs_lambda_goal(_, _, _, _, _, _, _, _, _)
),
unexpected(this_file,
"non-functor unify in construct_common_unify")
),
Context = goal_info_get_context(GoalInfo),
create_parallel_subterms(Args, Context, Ucontext, !CseInfo,
OldNewVars, Replacements),
map.from_assoc_list(OldNewVars, Sub),
rename_some_vars_in_goal(Sub, hlds_goal(GoalExpr1, GoalInfo),
HoistedGoal)
;
unexpected(this_file, "non-unify goal in construct_common_unify")
).
:- pred create_parallel_subterms(list(prog_var)::in, prog_context::in,
unify_context::in, cse_info::in, cse_info::out,
assoc_list(prog_var)::out, list(hlds_goal)::out) is det.
create_parallel_subterms([], _, _, !CseInfo, [], []).
create_parallel_subterms([OFV | OFV0], Context, UnifyContext, !CseInfo,
OldNewVars, Replacements) :-
create_parallel_subterms(OFV0, Context, UnifyContext, !CseInfo,
OldNewVars1, Replacements1),
create_parallel_subterm(OFV, Context, UnifyContext, !CseInfo,
OldNewVars1, OldNewVars, Goal),
Replacements = [Goal | Replacements1].
:- pred create_parallel_subterm(prog_var::in, prog_context::in,
unify_context::in, cse_info::in, cse_info::out,
assoc_list(prog_var)::in, assoc_list(prog_var)::out,
hlds_goal::out) is det.
create_parallel_subterm(OFV, Context, UnifyContext, !CseInfo, !OldNewVar,
Goal) :-
VarSet0 = !.CseInfo ^ csei_varset,
VarTypes0 = !.CseInfo ^ csei_vartypes,
varset.new_var(VarSet0, NFV, VarSet),
map.lookup(VarTypes0, OFV, Type),
map.det_insert(VarTypes0, NFV, Type, VarTypes),
!:OldNewVar = [OFV - NFV | !.OldNewVar],
UnifyContext = unify_context(MainCtxt, SubCtxt),
% It is ok to create complicated unifications here, because we rerun
% mode analysis on the resulting goal. It would be nicer to generate
% the right assignment unification directly, but that would require keeping
% track of the inst of OFV.
create_pure_atomic_complicated_unification(OFV, rhs_var(NFV),
Context, MainCtxt, SubCtxt, Goal),
!:CseInfo = !.CseInfo ^ csei_varset := VarSet,
!:CseInfo = !.CseInfo ^ csei_vartypes := VarTypes.
%-----------------------------------------------------------------------------%
:- pred find_similar_deconstruct(hlds_goal::in, hlds_goal::in,
prog_context::in, assoc_list(prog_var)::out, list(hlds_goal)::out)
is semidet.
find_similar_deconstruct(HoistedUnifyGoal, OldUnifyGoal, Context,
OldHoistedVars, Replacements) :-
(
HoistedUnifyGoal = hlds_goal(unify(_, _, _, HoistedUnifyInfo, OC), _),
HoistedUnifyInfo = deconstruct(_, HoistedFunctor,
HoistedVars, _, _, _),
OldUnifyGoal = hlds_goal(unify(_, _, _, OldUnifyInfo, _NC), _),
OldUnifyInfo = deconstruct(_, OldFunctor, OldVars, _, _, _)
->
HoistedFunctor = OldFunctor,
list.length(HoistedVars, HoistedVarsCount),
list.length(OldVars, OldVarsCount),
HoistedVarsCount = OldVarsCount,
assoc_list.from_corresponding_lists(OldVars, HoistedVars,
OldHoistedVars),
pair_subterms(OldHoistedVars, Context, OC, Replacements)
;
unexpected(this_file,
"find_similar_deconstruct: non-deconstruct unify")
).
:- pred pair_subterms(assoc_list(prog_var)::in, prog_context::in,
unify_context::in, list(hlds_goal)::out) is det.
pair_subterms([], _Context, _UnifyContext, []).
pair_subterms([OldVar - HoistedVar | OldHoistedVars], Context, UnifyContext,
Replacements) :-
pair_subterms(OldHoistedVars, Context, UnifyContext, Replacements1),
( OldVar = HoistedVar ->
Replacements = Replacements1
;
UnifyContext = unify_context(MainCtxt, SubCtxt),
% It is ok to create complicated unifications here, because we rerun
% mode analysis on the resulting goal. It would be nicer to generate
% the right assignment unification directly, but that would require
% keeping track of the inst of OldVar.
create_pure_atomic_complicated_unification(HoistedVar, rhs_var(OldVar),
Context, MainCtxt, SubCtxt, Goal),
Replacements = [Goal | Replacements1]
).
%-----------------------------------------------------------------------------%
% This section handles the case where the functor involved in the
% common subexpression contains existentially typed arguments,
% whether or not they are constrained to belong to a typeclass.
% In such cases, what the compiler used to consider several distinct
% types (the types of say the first the existentially typed argument
% in the deconstructions in the different branches) become one (in this
% case, the type of the first existentially typed argument in the
% hoisted out deconstruction). The prog_vars describing the types
% of the existentially typed arguments (i.e. containing their
% typeinfos) change as well, from being some of the variables in
% in the original deconstructions to being the corresponding variables
% in the hoisted out deconstruction.
%
% As an example, consider a disjunction such as
%
% (
% HeadVar.g2_2 = x:u(TypeClassInfo_for_v_8, V_4),
% ...
% ;
% HeadVar.g2_2 = x:u(TypeClassInfo_for_v_14, V_6)
% ...
% )
%
% The main part of cse_detection will replace this with
%
% HeadVar.g2_2 = x:u(V_17, V_16)
% (
% TypeClassInfo_for_v_8 = V_17,
% V_4 = V_16,
% ...
% ;
% TypeClassInfo_for_v_14 = V_17,
% V_6 = V_16,
% ...
% )
%
% However, this is not enough. Since TypeClassInfo_for_v_8 and
% TypeClassInfo_for_v_14 may (and probably will) be eliminated later,
% it is imperative that the data structures in the proc_info that refer
% to them be updated to eliminate references to those variables.
% Those data structures may originally contain something like this:
%
% type_info varmap:
% T_1 (number 1) -> typeclass_info(TypeClassInfo_for_v_8, 1)
% T_3 (number 3) -> typeclass_info(TypeClassInfo_for_v_14, 1)
% typeclass_info varmap:
% x:v(T_1) -> TypeClassInfo_for_v_8
% x:v(T_3) -> TypeClassInfo_for_v_14
% variable types map:
% V_4 (number 4) :: T_1
% V_6 (number 6) :: T_3
%
% They must be updated like this:
%
% type_info varmap:
% T_1 (number 1) -> typeclass_info(V_17, 1)
% typeclass_info varmap:
% x:v(T_1) -> V_17
% variable types map:
% V_4 (number 4) :: T_1
% V_6 (number 6) :: T_1
:- pred maybe_update_existential_data_structures(hlds_goal::in,
assoc_list(prog_var)::in, list(assoc_list(prog_var))::in,
cse_info::in, cse_info::out) is det.
maybe_update_existential_data_structures(Unify, FirstOldNew, LaterOldNew,
!CseInfo) :-
(
Unify = hlds_goal(unify(_, _, _, UnifyInfo, _), _),
UnifyInfo = deconstruct(Var, ConsId, _, _, _, _),
ModuleInfo = !.CseInfo ^ csei_module_info,
VarTypes = !.CseInfo ^ csei_vartypes,
map.lookup(VarTypes, Var, Type),
type_util.is_existq_cons(ModuleInfo, Type, ConsId)
->
update_existential_data_structures(FirstOldNew, LaterOldNew, !CseInfo)
;
true
).
:- pred update_existential_data_structures(
assoc_list(prog_var)::in, list(assoc_list(prog_var))::in,
cse_info::in, cse_info::out) is det.
update_existential_data_structures(FirstOldNew, LaterOldNews, !CseInfo) :-
list.condense(LaterOldNews, LaterOldNew),
map.from_assoc_list(FirstOldNew, FirstOldNewMap),
map.from_assoc_list(LaterOldNew, LaterOldNewMap),
RttiVarMaps0 = !.CseInfo ^ csei_rtti_varmaps,
VarTypes0 = !.CseInfo ^ csei_vartypes,
% Build a map for all locations in the rtti_varmaps that are changed
% by the application of FirstOldNewMap. The keys of this map are the
% new locations, and the values are the tvars (from the first branch)
% that have had their locations moved.
rtti_varmaps_tvars(RttiVarMaps0, TvarsList),
list.foldl(find_type_info_locn_tvar_map(RttiVarMaps0, FirstOldNewMap),
TvarsList, map.init, NewTvarMap),
% Traverse TVarsList again, this time looking for locations in later
% branches that merge with locations in the first branch. When we find one,
% add a type substitution which represents the type variables that were
% merged.
list.foldl(find_merged_tvars(RttiVarMaps0, LaterOldNewMap, NewTvarMap),
TvarsList, map.init, Renaming),
% Apply the full old->new map and the type substitution to the
% rtti_varmaps, and apply the type substitution to the vartypes.
list.append(FirstOldNew, LaterOldNew, OldNew),
map.from_assoc_list(OldNew, OldNewMap),
apply_substitutions_to_rtti_varmaps(Renaming, map.init, OldNewMap,
RttiVarMaps0, RttiVarMaps),
map.map_values_only(apply_variable_renaming_to_type(Renaming),
VarTypes0, VarTypes),
!:CseInfo = !.CseInfo ^ csei_rtti_varmaps := RttiVarMaps,
!:CseInfo = !.CseInfo ^ csei_vartypes := VarTypes.
:- pred find_type_info_locn_tvar_map(rtti_varmaps::in,
map(prog_var, prog_var)::in, tvar::in,
map(type_info_locn, tvar)::in, map(type_info_locn, tvar)::out) is det.
find_type_info_locn_tvar_map(RttiVarMaps, FirstOldNewMap, Tvar, !NewTvarMap) :-
rtti_lookup_type_info_locn(RttiVarMaps, Tvar, TypeInfoLocn0),
type_info_locn_var(TypeInfoLocn0, Old),
( map.search(FirstOldNewMap, Old, New) ->
type_info_locn_set_var(New, TypeInfoLocn0, TypeInfoLocn),
svmap.det_insert(TypeInfoLocn, Tvar, !NewTvarMap)
;
true
).
:- pred find_merged_tvars(rtti_varmaps::in, map(prog_var, prog_var)::in,
map(type_info_locn, tvar)::in, tvar::in,
tvar_renaming::in, tvar_renaming::out) is det.
find_merged_tvars(RttiVarMaps, LaterOldNewMap, NewTvarMap, Tvar, !Renaming) :-
rtti_lookup_type_info_locn(RttiVarMaps, Tvar, TypeInfoLocn0),
type_info_locn_var(TypeInfoLocn0, Old),
( map.search(LaterOldNewMap, Old, New) ->
type_info_locn_set_var(New, TypeInfoLocn0, TypeInfoLocn),
map.lookup(NewTvarMap, TypeInfoLocn, NewTvar),
( NewTvar = Tvar ->
true
;
svmap.det_insert(Tvar, NewTvar, !Renaming)
)
;
true
).
%-----------------------------------------------------------------------------%
:- func this_file = string.
this_file = "cse_detection.m".
%-----------------------------------------------------------------------------%
:- end_module cse_detection.
%-----------------------------------------------------------------------------%
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