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%-----------------------------------------------------------------------------%
% Copyright (C) 1998-1999 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: pd_cost.m
% Main author: stayl
%
% pd_cost__goal gives a very rough guess as to how much work a given goal
% will cause at runtime. This only counts the local cost not including
% the time taken by called predicates.
%
%-----------------------------------------------------------------------------%
:- module pd_cost.
:- interface.
:- import_module hlds_goal.
:- pred pd_cost__goal(hlds_goal::in, int::out) is det.
:- pred pd_cost__reg_assign(int::out) is det.
:- pred pd_cost__heap_assign(int::out) is det.
:- pred pd_cost__simple_test(int::out) is det.
:- pred pd_cost__heap_incr(int::out) is det.
:- pred pd_cost__stack_flush(int::out) is det.
:- pred pd_cost__builtin_call(int::out) is det.
:- pred pd_cost__call(int::out) is det.
:- pred pd_cost__higher_order_call(int::out) is det.
:- pred pd_cost__eliminate_switch(int::out) is det.
:- pred pd_cost__fold(int::out) is det.
:- pred pd_cost__recursive_fold(int::out) is det.
%-----------------------------------------------------------------------------%
:- implementation.
:- import_module hlds_data, prog_data.
:- import_module int, list, set, std_util, require.
%-----------------------------------------------------------------------------%
pd_cost__goal(conj(Goals) - _, Cost) :-
pd_cost__goals(Goals, 0, Cost).
pd_cost__goal(par_conj(Goals, _SM) - _, Cost) :-
pd_cost__goals(Goals, 0, Cost).
pd_cost__goal(disj(Goals, _) - _, Cost) :-
pd_cost__goals(Goals, 0, Cost0),
pd_cost__stack_flush(Cost1),
Cost is Cost0 + Cost1.
pd_cost__goal(switch(_, _, Cases, _) - _, Cost) :-
pd_cost__simple_test(Cost0),
pd_cost__cases(Cases, Cost0, Cost).
pd_cost__goal(if_then_else(_, Cond, Then, Else, _) - _, Cost) :-
pd_cost__goal(Cond, Cost1),
pd_cost__goal(Then, Cost2),
pd_cost__goal(Else, Cost3),
Cost is Cost1 + Cost2 + Cost3.
pd_cost__goal(call(_, _, Args, BuiltinState, _, _) - _, Cost) :-
( BuiltinState = inline_builtin ->
pd_cost__builtin_call(Cost)
;
pd_cost__stack_flush(Cost1),
list__length(Args, Arity),
InputArgs is Arity // 2, % rough
pd_cost__reg_assign(AssignCost),
pd_cost__call(Cost2),
Cost is Cost1 + Cost2 + AssignCost * InputArgs
).
pd_cost__goal(not(Goal) - _, Cost) :-
pd_cost__goal(Goal, Cost).
pd_cost__goal(some(_, _, Goal) - _, Cost) :-
pd_cost__goal(Goal, Cost).
pd_cost__goal(generic_call(_, Args, _, _) - _, Cost) :-
list__length(Args, Arity),
pd_cost__reg_assign(AssignCost),
Cost0 = AssignCost * Arity // 2,
pd_cost__stack_flush(Cost1),
pd_cost__higher_order_call(Cost2),
Cost is Cost0 + Cost1 + Cost2.
pd_cost__goal(unify(_, _, _, Unification, _) - GoalInfo, Cost) :-
goal_info_get_nonlocals(GoalInfo, NonLocals),
pd_cost__unify(NonLocals, Unification, Cost).
pd_cost__goal(pragma_c_code(Attributes, _, _, Args, _, _, _) - _, Cost) :-
( may_call_mercury(Attributes, will_not_call_mercury) ->
Cost1 = 0
;
pd_cost__stack_flush(Cost1)
),
pd_cost__call(Cost2),
list__length(Args, Arity),
InputArgs is Arity // 2, % rough
pd_cost__reg_assign(AssignCost),
Cost is Cost1 + Cost2 + AssignCost * InputArgs.
pd_cost__goal(bi_implication(_, _) - _, _) :-
% these should have been expanded out by now
error("pd_cost__goal: unexpected bi_implication").
:- pred pd_cost__unify(set(prog_var)::in, unification::in, int::out) is det.
pd_cost__unify(_, assign(_, _), 0).
pd_cost__unify(_, complicated_unify(_, _, _), Cost) :-
pd_cost__stack_flush(Cost).
pd_cost__unify(_, simple_test(_, _), Cost) :-
pd_cost__simple_test(Cost).
pd_cost__unify(NonLocals, construct(Var, _, Args, _, _, _, _), Cost) :-
( set__member(Var, NonLocals) ->
list__length(Args, Arity),
pd_cost__heap_incr(Cost1),
pd_cost__heap_assign(Cost2),
Cost = Cost1 + Arity * Cost2
;
Cost = 0
).
pd_cost__unify(NonLocals, deconstruct(_, _, Args, _, CanFail), Cost) :-
( CanFail = can_fail ->
pd_cost__simple_test(Cost0)
;
Cost0 = 0
),
list__filter(
lambda([X::in] is semidet,
set__member(X, NonLocals)
), Args, NonLocalArgs),
list__length(NonLocalArgs, NumAssigns),
pd_cost__heap_incr(Cost1),
pd_cost__heap_assign(Cost2),
Cost = Cost0 + Cost1 + NumAssigns * Cost2.
:- pred pd_cost__goals(list(hlds_goal)::in, int::in, int::out) is det.
pd_cost__goals([], Cost, Cost).
pd_cost__goals([Goal | Goals], Cost0, Cost) :-
pd_cost__goal(Goal, Cost1),
Cost2 is Cost0 + Cost1,
pd_cost__goals(Goals, Cost2, Cost).
:- pred pd_cost__cases(list(case)::in, int::in, int::out) is det.
pd_cost__cases([], Cost, Cost).
pd_cost__cases([case(_, Goal) | Cases], Cost0, Cost) :-
pd_cost__goal(Goal, Cost1),
Cost2 is Cost0 + Cost1,
pd_cost__cases(Cases, Cost2, Cost).
%-----------------------------------------------------------------------------%
pd_cost__reg_assign(1).
pd_cost__heap_assign(2).
pd_cost__simple_test(3).
pd_cost__heap_incr(3). % Depends on GC, want to penalise mem usage.
pd_cost__stack_flush(5).
pd_cost__builtin_call(3). % very rough - int:'+' == float:'/' !.
pd_cost__call(3).
pd_cost__higher_order_call(8).
pd_cost__eliminate_switch(5).
pd_cost__fold(15). % reward folding
pd_cost__recursive_fold(25). % reward recursive folding more
%-----------------------------------------------------------------------------%
%-----------------------------------------------------------------------------%
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