mercury/compiler/inlining.m

%-----------------------------------------------------------------------------%
% Copyright (C) 1994-2002 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.
%-----------------------------------------------------------------------------%

% Main author: conway.

:- module transform_hlds__inlining.

	% This module inlines
	%
	%	* (--inline-simple and --inline-simple-threshold N)
	%	  procedures whose size is below the given threshold,
	%	  PLUS	  
	%	  procedures that are flat (ie contain no branched structures)
	%	  and are composed of inline builtins (eg arithmetic),
	%	  and whose size is less than three times the given threshold
	%	  (XXX shouldn't hard-code 3)
	%
	%	* (--inline-compound-threshold N)
	%	  procedures where the product of the number of calls to them
	%	  and their size is below a given threshold.
	%
	%	* (--inline-single-use)
	%	  procedures which are called only once
	%
	% 	* procedures which have a `:- pragma inline(name/arity).'
	%
	% It will not inline procedures which have a 
	% 	`:- pragma no_inline(name/arity).'
	%
	% If inlining a procedure takes the total number of variables over
	% a given threshold (from a command-line option), then the procedure
	% is not inlined - note that this means that some calls to a
	% procedure may inlined while others are not.
	%
	% It builds the call-graph (if necessary) works from the bottom of
	% the call-graph towards the top, first performing inlining on a
	% procedure then deciding if calls to it (higher in the call-graph)
	% should be inlined. SCCs get flattend and processed in the order
	% returned by hlds_dependency_info_get_dependency_ordering.
	%
	% There are a couple of classes of procedure that we clearly want
	% to inline because doing so *reduces* the size of the generated
	% code:
	%
	%	- access predicates that get or set one or more fields
	%	  of a structure (Inlining these is almost always a win
	%	  because the infrastructure for the call to the procedure
	%	  is almost always larger than the code to do the access.
	%	  In the case of `get' accessors, the call usually becomes
	%	  a single `field' expression to get the relevant field of
	%	  the structure. In the case of `set' accessors, it is a bit
	%	  more complicated since the code to copy the fields can be
	%	  quite big if there are lots of fields, however in the case
	%	  where several `set' accessors get called one after the other,
	%	  inlining them enables the code generator to avoid creating
	%	  the intermediate structures which is often a win).
	%
	%	- arithmetic predicates where as above, the cost of the
	%	  call will often outweigh the cost of the arithmetic.
	%
	%	- det or semi pragma C code, where often the C operation is
	%	  very small, inlining avoids a call and allows the C compiler
	%	  to do a better job of optimizing it.
	%
	% The threshold on the size of simple goals (which covers both of the
	% first two cases above), is to prevent the inlining of large goals
	% such as those that construct big terms where the duplication is
	% usually inappropriate (for example in nrev).
	%
	% The threshold on the number of variables in a procedure is to prevent
	% the problem of inlining lots of calls and having a resulting
	% procedure with so many variables that the back end of the compiler
	% gets bogged down (for example in the pseudoknot benchmark).
	%
	% Due to the way in which we generate code for model_non
	% pragma_foreign_code, procedures whose body is such a
	% pragma_foreign_code must NOT be inlined.

%-----------------------------------------------------------------------------%

:- interface.

:- import_module hlds__hlds_goal, hlds__hlds_module, hlds__hlds_pred.
:- import_module parse_tree__prog_data.
:- import_module bool, io, list, map.

:- pred inlining(module_info, module_info, io__state, io__state).
:- mode inlining(in, out, di, uo) is det.

:- pred inlining__is_simple_clause_list(list(clause), int).
:- mode inlining__is_simple_clause_list(in, in) is semidet.

:- pred inlining__is_simple_goal(hlds_goal, int).
:- mode inlining__is_simple_goal(in, in) is semidet.

	% inlining__do_inline_call(UnivQVars, Args,
	%	CalledPredInfo, CalledProcInfo,
	% 	VarSet0, VarSet, VarTypes0, VarTypes, TVarSet0, TVarSet,
	%	TypeInfoMap0, TypeInfoMap).
	%
	% Given the universally quantified type variables in the caller's
	% type, the arguments to the call, the pred_info and proc_info
	% for the called goal and various information about the variables
	% and types in the procedure currently being analysed, rename the
	% goal for the called procedure so that it can be inlined.
:- pred inlining__do_inline_call(list(tvar), list(prog_var),
		pred_info, proc_info, prog_varset, prog_varset,
		map(prog_var, type), map(prog_var, type),
		tvarset, tvarset, map(tvar, type_info_locn), 
		map(tvar, type_info_locn), hlds_goal).
:- mode inlining__do_inline_call(in, in, in, in, in, out, in, out,
	in, out, in, out, out) is det.

	% inlining__get_type_substitution(CalleeArgTypes, CallerArgTypes,
	%	HeadTypeParams, CalleeExistQTVars, TypeSubn).
	%
	% Work out a type substitution to map the callee's argument
	% types into the caller's.
:- pred inlining__get_type_substitution(list(type), list(type),
		head_type_params, list(tvar), map(tvar, type)).
:- mode inlining__get_type_substitution(in, in, in, in, out) is det.

	% inlining__rename_goal(CalledProcHeadVars, CallArgs,
	%	CallerVarSet0, CalleeVarSet, CallerVarSet,
	%	CallerVarTypes0, CalleeVarTypes, CallerVarTypes,
	%	VarRenaming, CalledGoal, RenamedGoal).
:- pred inlining__rename_goal(list(prog_var), list(prog_var), prog_varset,
		prog_varset, prog_varset, map(prog_var, type),
		map(prog_var, type), map(prog_var, type),
		map(prog_var, prog_var), hlds_goal, hlds_goal). 
:- mode inlining__rename_goal(in, in, in, in, out,
		in, in, out, out, in, out) is det.

	% inlining__can_inline_proc(PredId, ProcId, BuiltinState,
	% 	InlinePromisedPure, CallingPredMarkers, ModuleInfo).
	%
	% Determine whether a predicate can be inlined.
:- pred inlining__can_inline_proc(pred_id, proc_id, builtin_state,
		bool, pred_markers, module_info).
:- mode inlining__can_inline_proc(in, in, in, in, in, in) is semidet.

%-----------------------------------------------------------------------------%
%-----------------------------------------------------------------------------%

:- implementation.

% Parse tree modules
:- import_module parse_tree__prog_data.

% HLDS modules
:- import_module hlds__hlds_data, check_hlds__type_util.
:- import_module check_hlds__mode_util, hlds__goal_util.
:- import_module check_hlds__det_analysis.
:- import_module hlds__quantification, ll_backend__code_aux.
:- import_module transform_hlds__dead_proc_elim.
:- import_module transform_hlds__dependency_graph.
:- import_module hlds__passes_aux, check_hlds__purity.

% Misc
:- import_module libs__globals, libs__options, libs__trace_params.

% Standard library modules
:- import_module bool, int, list, assoc_list, set, std_util, require.
:- import_module term, varset.

%-----------------------------------------------------------------------------%

	% this structure holds option values, extracted from the globals
:- type inline_params
	--->	params(
			simple				:: bool,
			single_use			:: bool,
			size_threshold			:: int,
			simple_goal_threshold		:: int,
			var_threshold			:: int,
			highlevel_code			:: bool,
			tracing				:: bool
		).

inlining(ModuleInfo0, ModuleInfo) -->
		%
		% Package up all the inlining options
		% - whether to inline simple conj's of builtins
		% - whether to inline predicates that are
		%   only called once
		% - the threshold for determining whether to
		%   inline more complicated goals
		% - the threshold for determining whether to
		%   inline the simple conj's
		% - the upper limit on the number of variables
		%   we want in procedures - if inlining a procedure
		%   would cause the number of variables to exceed
		%   this threshold then we don't inline it.
		% - whether we're in an MLDS grade
		%
	globals__io_lookup_bool_option(inline_simple, Simple),
	globals__io_lookup_bool_option(inline_single_use, SingleUse),
	globals__io_lookup_int_option(inline_compound_threshold,
							CompoundThreshold),
	globals__io_lookup_int_option(inline_simple_threshold, SimpleThreshold),
	globals__io_lookup_int_option(inline_vars_threshold, VarThreshold),
	globals__io_lookup_bool_option(highlevel_code, HighLevelCode),
	globals__io_get_trace_level(TraceLevel),
	{ Tracing = bool__not(trace_level_is_none(TraceLevel)) },
	{ Params = params(Simple, SingleUse, CompoundThreshold,
		SimpleThreshold, VarThreshold, HighLevelCode, Tracing) },

		%
		% Get the usage counts for predicates
		% (but only if needed, i.e. only if --inline-single-use
		% or --inline-compound-threshold has been specified)
		%
	(
		( { SingleUse = yes }
		; { CompoundThreshold > 0 }
		)
	->
		{ dead_proc_elim__analyze(ModuleInfo0, NeededMap) }
	;
		{ map__init(NeededMap) }
	),

		% build the call graph and extract the topological sort
		% Note: the topological sort returns a list of SCCs.
		% Clearly, we want to process the SCCs bottom to top
		% (which is the order that they are returned), but it
		% is not easy to guess the best way to flatten each SCC
		% to achieve the best result. The current implementation
		% just uses the ordering of the list returned by the
		% topological sort. A more sophisticated approach would be
		% to break the cycle so that the procedure(s) that are called
		% by higher SCCs are processed last, but we do not implement
		% that yet.
	{ module_info_ensure_dependency_info(ModuleInfo0, ModuleInfo1) },
	{ module_info_dependency_info(ModuleInfo1, DepInfo) },
	{ hlds_dependency_info_get_dependency_ordering(DepInfo, SCCs) },
	{ list__condense(SCCs, PredProcs) },
	{ set__init(InlinedProcs0) },
	inlining__do_inlining(PredProcs, NeededMap, Params, InlinedProcs0,
		ModuleInfo1, ModuleInfo2),

		% The dependency graph is now out of date and 
		% needs to be rebuilt.
	{ module_info_clobber_dependency_info(ModuleInfo2, ModuleInfo) }.

:- pred inlining__do_inlining(list(pred_proc_id), needed_map, inline_params,
		set(pred_proc_id), module_info, module_info,
		io__state, io__state).
:- mode inlining__do_inlining(in, in, in, in, in, out, di, uo) is det.

inlining__do_inlining([], _Needed, _Params, _Inlined, Module, Module) --> [].
inlining__do_inlining([PPId | PPIds], Needed, Params, Inlined0,
		Module0, Module) -->
	inlining__in_predproc(PPId, Inlined0, Params, Module0, Module1),
	inlining__mark_predproc(PPId, Needed, Params, Module1,
		Inlined0, Inlined1),
	inlining__do_inlining(PPIds, Needed, Params, Inlined1, Module1, Module).

:- pred inlining__mark_predproc(pred_proc_id, needed_map, inline_params,
		module_info, set(pred_proc_id), set(pred_proc_id),
		io__state, io__state).
:- mode inlining__mark_predproc(in, in, in, in, in, out, di, uo) is det.

%
% This predicate effectively adds implicit `pragma inline'
% directives for procedures that match its heuristic.
%

inlining__mark_predproc(PredProcId, NeededMap, Params, ModuleInfo, 
		InlinedProcs0, InlinedProcs) -->
	(
		{ Simple = Params ^ simple },
		{ SingleUse = Params ^ single_use },
		{ CompoundThreshold = Params ^ size_threshold },
		{ SimpleThreshold = Params ^ simple_goal_threshold },
		{ PredProcId = proc(PredId, ProcId) },
		{ module_info_pred_info(ModuleInfo, PredId, PredInfo) },
		{ pred_info_procedures(PredInfo, Procs) },
		{ map__lookup(Procs, ProcId, ProcInfo) },
		{ proc_info_goal(ProcInfo, CalledGoal) },
		{ Entity = proc(PredId, ProcId) },

		%
		% the heuristic represented by the following code
		% could be improved
		%
		(
			{ Simple = yes },
			{ inlining__is_simple_goal(CalledGoal,
				SimpleThreshold) }
		;
			{ CompoundThreshold > 0 },
			{ map__search(NeededMap, Entity, Needed) },
			{ Needed = yes(NumUses) },
			{ goal_size(CalledGoal, Size) },
			{ Size * NumUses =< CompoundThreshold }
		;
			{ SingleUse = yes },
			{ map__search(NeededMap, Entity, Needed) },
			{ Needed = yes(NumUses) },
			{ NumUses = 1 }
		),
		% Don't inline recursive predicates
		% (unless explicitly requested)
		{ \+ goal_calls(CalledGoal, PredProcId) }
	->
		inlining__mark_proc_as_inlined(PredProcId, ModuleInfo,
			InlinedProcs0, InlinedProcs)
	;
		{ InlinedProcs = InlinedProcs0 }
	).

	% this heuristic is used for both local and intermodule inlining

inlining__is_simple_clause_list(Clauses, SimpleThreshold) :-
	clause_list_size(Clauses, Size),
	(
		Size < SimpleThreshold
	;
		Clauses = [clause(_, Goal, _, _)],
		Size < SimpleThreshold * 3,
		%
		% For flat goals, we are more likely to be able to
		% optimize stuff away, so we use a higher threshold.
		% XXX this should be a separate option, we shouldn't
		% hardcode the number `3' (which is just a guess).
		%
		inlining__is_flat_simple_goal(Goal)
	).
		
inlining__is_simple_goal(CalledGoal, SimpleThreshold) :-
	goal_size(CalledGoal, Size),
	(
		Size < SimpleThreshold
	;
		%
		% For flat goals, we are more likely to be able to
		% optimize stuff away, so we use a higher threshold.
		% XXX this should be a separate option, we shouldn't
		% hardcode the number `3' (which is just a guess).
		%
		Size < SimpleThreshold * 3,
		inlining__is_flat_simple_goal(CalledGoal)
	).

:- pred inlining__is_flat_simple_goal(hlds_goal::in) is semidet.

inlining__is_flat_simple_goal(conj(Goals) - _) :-
	inlining__is_flat_simple_goal_list(Goals).
inlining__is_flat_simple_goal(not(Goal) - _) :-
	inlining__is_flat_simple_goal(Goal).
inlining__is_flat_simple_goal(some(_, _, Goal) - _) :-
	inlining__is_flat_simple_goal(Goal).
inlining__is_flat_simple_goal(call(_, _, _, BuiltinState, _, _) - _) :-
	BuiltinState = inline_builtin.
inlining__is_flat_simple_goal(unify(_, _, _, _, _) - _).

:- pred inlining__is_flat_simple_goal_list(hlds_goals::in) is semidet.

inlining__is_flat_simple_goal_list([]).
inlining__is_flat_simple_goal_list([Goal | Goals]) :-
	inlining__is_flat_simple_goal(Goal),
	inlining__is_flat_simple_goal_list(Goals).

:- pred inlining__mark_proc_as_inlined(pred_proc_id, module_info,
	set(pred_proc_id), set(pred_proc_id), io__state, io__state).
:- mode inlining__mark_proc_as_inlined(in, in, in, out, di, uo) is det.

inlining__mark_proc_as_inlined(proc(PredId, ProcId), ModuleInfo,
		InlinedProcs0, InlinedProcs) -->
	{ set__insert(InlinedProcs0, proc(PredId, ProcId), InlinedProcs) },
	{ module_info_pred_info(ModuleInfo, PredId, PredInfo) },
	( { pred_info_requested_inlining(PredInfo) } ->
		[]
	;
		write_proc_progress_message("% Inlining ", PredId, ProcId,
			ModuleInfo)
	).

%-----------------------------------------------------------------------------%

		% inline_info contains the information that is changed
		% as a result of inlining. It is threaded through the
		% inlining process, and when finished, contains the
		% updated information associated with the new goal.
		%
		% It also stores some necessary information that is not
		% updated.

:- type inline_info	
	---> inline_info(
		int,			% variable threshold for inlining
		bool,			% highlevel_code option
		bool,			% is executing tracing enabled
		set(pred_proc_id),	% inlined procs
		module_info,		% module_info
		list(tvar),		% universally quantified type vars
					% occurring in the argument types
					% for this predicate (the caller,
					% not the callee).  These are the
					% ones that must not be bound.
		pred_markers,		% markers for the current predicate

			% the following fields are updated as a result
			% of inlining
		prog_varset,		% varset
		map(prog_var, type),	% variable types
		tvarset,		% type variables
		map(tvar, type_info_locn),% type_info varset, a mapping from 
					% type variables to variables
					% where their type_info is
					% stored.
		bool,			% Did we do any inlining in the proc?
		bool,			% Does the goal need to be
					% requantified?
		bool,			% Did we change the determinism
					% of any subgoal?
		bool			% Did we change the purity of
					% any subgoal.
	).

:- pred inlining__in_predproc(pred_proc_id, set(pred_proc_id), inline_params,
		module_info, module_info, io__state, io__state).
:- mode inlining__in_predproc(in, in, in, in, out, di, uo) is det.

inlining__in_predproc(PredProcId, InlinedProcs, Params,
		ModuleInfo0, ModuleInfo, IoState0, IoState) :-
	VarThresh = Params^var_threshold,
	HighLevelCode = Params^highlevel_code,
	Tracing = Params^tracing,

	PredProcId = proc(PredId, ProcId),

	module_info_preds(ModuleInfo0, PredTable0),
	map__lookup(PredTable0, PredId, PredInfo0),
	pred_info_procedures(PredInfo0, ProcTable0),
	map__lookup(ProcTable0, ProcId, ProcInfo0),

	pred_info_get_univ_quant_tvars(PredInfo0, UnivQTVars),
	pred_info_typevarset(PredInfo0, TypeVarSet0),
	pred_info_get_markers(PredInfo0, Markers),

	proc_info_goal(ProcInfo0, Goal0),
	proc_info_varset(ProcInfo0, VarSet0),
	proc_info_vartypes(ProcInfo0, VarTypes0),
	proc_info_typeinfo_varmap(ProcInfo0, TypeInfoVarMap0),

	DidInlining0 = no,
	Requantify0 = no,
	DetChanged0 = no,
	PurityChanged0 = no,

	InlineInfo0 = inline_info(VarThresh, HighLevelCode, Tracing,
		InlinedProcs, ModuleInfo0, UnivQTVars, Markers,
		VarSet0, VarTypes0, TypeVarSet0, TypeInfoVarMap0,
		DidInlining0, Requantify0, DetChanged0, PurityChanged0),

	inlining__inlining_in_goal(Goal0, Goal, InlineInfo0, InlineInfo),

	InlineInfo = inline_info(_, _, _, _, _, _, _, VarSet, VarTypes,
		TypeVarSet, TypeInfoVarMap, DidInlining, Requantify,
		DetChanged, PurityChanged),

	pred_info_set_typevarset(PredInfo0, TypeVarSet, PredInfo1),

	proc_info_set_varset(ProcInfo0, VarSet, ProcInfo1),
	proc_info_set_vartypes(ProcInfo1, VarTypes, ProcInfo2),
	proc_info_set_typeinfo_varmap(ProcInfo2, TypeInfoVarMap, ProcInfo3),
	proc_info_set_goal(ProcInfo3, Goal, ProcInfo4),

	(
		Requantify = yes,
		requantify_proc(ProcInfo4, ProcInfo5)
	;
		Requantify = no,
		ProcInfo5 = ProcInfo4
	),

	(
		DidInlining = yes,
		recompute_instmap_delta_proc(yes, ProcInfo5, ProcInfo,
			ModuleInfo0, ModuleInfo1)
	;
		DidInlining = no,
		ProcInfo = ProcInfo5,
		ModuleInfo1 = ModuleInfo0
	),

	map__det_update(ProcTable0, ProcId, ProcInfo, ProcTable),
	pred_info_set_procedures(PredInfo1, ProcTable, PredInfo2),

	(
		PurityChanged = yes,
		repuritycheck_proc(ModuleInfo1, PredProcId,
			PredInfo2, PredInfo)
	;
		PurityChanged = no,
		PredInfo = PredInfo2
	),

	map__det_update(PredTable0, PredId, PredInfo, PredTable),
	module_info_set_preds(ModuleInfo1, PredTable, ModuleInfo2),

		% If the determinism of some sub-goals has changed,
		% then we re-run determinism analysis, because
		% propagating the determinism information through
		% the procedure may lead to more efficient code.
	globals__io_get_globals(Globals, IoState0, IoState),
	(
		DetChanged = yes,	
		det_infer_proc(PredId, ProcId, ModuleInfo2, ModuleInfo,
			Globals, _, _, _)
	;
		DetChanged = no,
		ModuleInfo = ModuleInfo2
	).

%-----------------------------------------------------------------------------%

:- pred inlining__inlining_in_goal(hlds_goal, hlds_goal, inline_info,
		inline_info).
:- mode inlining__inlining_in_goal(in, out, in, out) is det.

inlining__inlining_in_goal(conj(Goals0) - GoalInfo, conj(Goals) - GoalInfo) -->
	inlining__inlining_in_conj(Goals0, Goals).

inlining__inlining_in_goal(par_conj(Goals0) - GoalInfo,
		par_conj(Goals) - GoalInfo) -->
	inlining__inlining_in_disj(Goals0, Goals).

inlining__inlining_in_goal(disj(Goals0) - GoalInfo, disj(Goals) - GoalInfo) -->
	inlining__inlining_in_disj(Goals0, Goals).

inlining__inlining_in_goal(switch(Var, Det, Cases0) - GoalInfo,
		switch(Var, Det, Cases) - GoalInfo) -->
	inlining__inlining_in_cases(Cases0, Cases).

inlining__inlining_in_goal(
		if_then_else(Vars, Cond0, Then0, Else0) - GoalInfo,
		if_then_else(Vars, Cond, Then, Else) - GoalInfo) -->
	inlining__inlining_in_goal(Cond0, Cond),
	inlining__inlining_in_goal(Then0, Then),
	inlining__inlining_in_goal(Else0, Else).

inlining__inlining_in_goal(not(Goal0) - GoalInfo, not(Goal) - GoalInfo) -->
	inlining__inlining_in_goal(Goal0, Goal).

inlining__inlining_in_goal(some(Vars, CanRemove, Goal0) - GoalInfo,
		some(Vars, CanRemove, Goal) - GoalInfo) -->
	inlining__inlining_in_goal(Goal0, Goal).

inlining__inlining_in_goal(call(PredId, ProcId, ArgVars, Builtin, Context,
		Sym) - GoalInfo0, Goal - GoalInfo, InlineInfo0, InlineInfo) :-

	InlineInfo0 = inline_info(VarThresh, HighLevelCode, Tracing,
		InlinedProcs, ModuleInfo, HeadTypeParams, Markers,
		VarSet0, VarTypes0, TypeVarSet0, TypeInfoVarMap0,
		DidInlining0, Requantify0, DetChanged0, PurityChanged0),

	% should we inline this call?
	(
		inlining__should_inline_proc(PredId, ProcId, Builtin,
			HighLevelCode, Tracing, InlinedProcs, Markers,
			ModuleInfo),
			% okay, but will we exceed the number-of-variables
			% threshold?
		varset__vars(VarSet0, ListOfVars),
		list__length(ListOfVars, ThisMany),
			% We need to find out how many variables the
			% Callee has
		module_info_pred_proc_info(ModuleInfo, PredId, ProcId,
			PredInfo, ProcInfo),
        	proc_info_varset(ProcInfo, CalleeVarSet),
		varset__vars(CalleeVarSet, CalleeListOfVars),
		list__length(CalleeListOfVars, CalleeThisMany),
		TotalVars is ThisMany + CalleeThisMany,
		TotalVars =< VarThresh
	->
		inlining__do_inline_call(HeadTypeParams, ArgVars, PredInfo, 
			ProcInfo, VarSet0, VarSet, VarTypes0, VarTypes,
			TypeVarSet0, TypeVarSet, TypeInfoVarMap0, 
			TypeInfoVarMap, Goal - GoalInfo),

			%
			% If some of the output variables are not used in
			% the calling procedure, requantify the procedure.
			%
		goal_info_get_nonlocals(GoalInfo0, NonLocals),
		( set__list_to_set(ArgVars) = NonLocals ->
			Requantify = Requantify0
		;
			Requantify = yes
		),

		(
			infer_goal_info_purity(GoalInfo0, Purity),
			infer_goal_info_purity(GoalInfo, Purity)
		->
			PurityChanged = PurityChanged0
		;
			PurityChanged = yes
		),
			
			% If the inferred determinism of the called
			% goal differs from the declared determinism,
			% flag that we should re-run determinism analysis
			% on this proc.
		goal_info_get_determinism(GoalInfo0, Determinism0),
		goal_info_get_determinism(GoalInfo, Determinism),
		DidInlining = yes,
		( Determinism0 = Determinism ->
			DetChanged = DetChanged0
		;
			DetChanged = yes
		)
	;
		Goal = call(PredId, ProcId, ArgVars, Builtin, Context, Sym),
		GoalInfo = GoalInfo0,
		VarSet = VarSet0,
		VarTypes = VarTypes0,
		TypeVarSet = TypeVarSet0,
		TypeInfoVarMap = TypeInfoVarMap0,
		DidInlining = DidInlining0,
		Requantify = Requantify0,
		DetChanged = DetChanged0,
		PurityChanged = PurityChanged0
	),
	InlineInfo = inline_info(VarThresh, HighLevelCode, Tracing,
		InlinedProcs, ModuleInfo, HeadTypeParams, Markers,
		VarSet, VarTypes, TypeVarSet, TypeInfoVarMap, DidInlining,
		Requantify, DetChanged, PurityChanged).

inlining__inlining_in_goal(generic_call(A, B, C, D) - GoalInfo,
		generic_call(A, B, C, D) - GoalInfo) --> [].

inlining__inlining_in_goal(unify(A, B, C, D, E) - GoalInfo,
		unify(A, B, C, D, E) - GoalInfo) --> [].

inlining__inlining_in_goal(
		foreign_proc(A, B, C, D, E, F, G) - GoalInfo,
		foreign_proc(A, B, C, D, E, F, G) - GoalInfo) --> [].

inlining__inlining_in_goal(shorthand(_) - _, _) -->
	% these should have been expanded out by now
	{ error("inlining__inlining_in_goal: unexpected shorthand") }.

%-----------------------------------------------------------------------------%

inlining__do_inline_call(HeadTypeParams, ArgVars, PredInfo, ProcInfo, 
		VarSet0, VarSet, VarTypes0, VarTypes, TypeVarSet0, TypeVarSet, 
		TypeInfoVarMap0, TypeInfoVarMap, Goal) :-

	proc_info_goal(ProcInfo, CalledGoal),

	% look up the rest of the info for the called procedure.

	pred_info_typevarset(PredInfo, CalleeTypeVarSet),
	proc_info_headvars(ProcInfo, HeadVars),
	proc_info_vartypes(ProcInfo, CalleeVarTypes0),
	proc_info_varset(ProcInfo, CalleeVarSet),
	proc_info_typeinfo_varmap(ProcInfo, CalleeTypeInfoVarMap0),

	% Substitute the appropriate types into the type
	% mapping of the called procedure.  For example, if we
	% call `:- pred foo(T)' with an argument of type
	% `int', then we need to replace all occurrences of
	% type `T' with type `int' when we inline it.
	% Conversely, in the case of existentially typed preds,
	% we may need to bind type variables in the caller.
	% For example, if we call `:- pred some [T] foo(T)',
	% and the definition of `foo' binds `T' to `int',
	% then we need to replace all occurrences of type `T'
	% with type `int' in the caller.

	% first, rename apart the type variables in the callee.
	% (we can almost throw away the new typevarset, since we
	% are about to substitute away any new type variables,
	% but any unbound type variables in the callee will not
	% be substituted away)

	varset__merge_subst(TypeVarSet0, CalleeTypeVarSet,
		TypeVarSet, TypeRenaming),
	apply_substitution_to_type_map(CalleeVarTypes0, TypeRenaming,
		CalleeVarTypes1),

	% next, compute the type substitution and then apply it

	% Note: there's no need to update the type_info locations maps,
	% either for the caller or callee, since for any type vars in the
	% callee which get bound to type vars in the caller, the type_info
	% location will be given by the entry in the caller's
	% type_info locations map (and vice versa).  It doesn't matter if the
	% final type_info locations map contains some entries
	% for type variables which have been substituted away,
	% because those entries simply won't be used.

	map__apply_to_list(HeadVars, CalleeVarTypes1, HeadTypes),
	map__apply_to_list(ArgVars, VarTypes0, ArgTypes),

	pred_info_get_exist_quant_tvars(PredInfo, CalleeExistQVars),
	inlining__get_type_substitution(HeadTypes, ArgTypes, HeadTypeParams,
		CalleeExistQVars, TypeSubn),

	% handle the common case of non-existentially typed preds specially,
	% since we can do things more efficiently in that case
	( CalleeExistQVars = [] ->
		% update types in callee only
		apply_rec_substitution_to_type_map(CalleeVarTypes1,
			TypeSubn, CalleeVarTypes),
		VarTypes1 = VarTypes0
	;
		% update types in callee
		apply_rec_substitution_to_type_map(CalleeVarTypes1,
			TypeSubn, CalleeVarTypes),
		% update types in caller
		apply_rec_substitution_to_type_map(VarTypes0,
			TypeSubn, VarTypes1)
	),

	% Now rename apart the variables in the called goal.
	inlining__rename_goal(HeadVars, ArgVars, VarSet0, CalleeVarSet,
		VarSet, VarTypes1, CalleeVarTypes, VarTypes, Subn,
		CalledGoal, Goal),

	apply_substitutions_to_var_map(CalleeTypeInfoVarMap0, 
		TypeRenaming, TypeSubn, Subn, CalleeTypeInfoVarMap1),
	map__merge(TypeInfoVarMap0, CalleeTypeInfoVarMap1,
		TypeInfoVarMap).

inlining__get_type_substitution(HeadTypes, ArgTypes,
		HeadTypeParams, CalleeExistQVars, TypeSubn) :-
	( CalleeExistQVars = [] ->
		( type_list_subsumes(HeadTypes, ArgTypes, TypeSubn0) ->
			TypeSubn = TypeSubn0 
		;
			% The head types should always be unifiable with the
			% actual argument types, otherwise it is a type error
			% that should have been detected by typechecking.
			% But polymorphism.m introduces type-incorrect code --
			% e.g. compare(Res, EnumA, EnumB) gets converted
			% into builtin_compare_int(Res, EnumA, EnumB), which
			% is a type error since it assumes that an enumeration
			% is an int.  In those cases, we don't need to
			% worry about the type substitution.
			% (Perhaps it would be better if polymorphism introduced
			% calls to unsafe_type_cast/2 for such cases.)
			map__init(TypeSubn)
		)
	;
		    % for calls to existentially type preds, we may need to
		    % bind type variables in the caller, not just those in
		    % the callee
		(
			map__init(TypeSubn0),
			type_unify_list(HeadTypes, ArgTypes, HeadTypeParams,
				TypeSubn0, TypeSubn1)
		->
			TypeSubn = TypeSubn1
		;
			error("inlining.m: type unification failed")
		)
	).

inlining__rename_goal(HeadVars, ArgVars, VarSet0, CalleeVarSet,
		VarSet, VarTypes1, CalleeVarTypes, VarTypes, Subn,
		CalledGoal, Goal) :-
	map__from_corresponding_lists(HeadVars, ArgVars, Subn0),
	varset__vars(CalleeVarSet, CalleeListOfVars),
	goal_util__create_variables(CalleeListOfVars, VarSet0,
		VarTypes1, Subn0, CalleeVarTypes, CalleeVarSet,
		VarSet, VarTypes, Subn),
	goal_util__must_rename_vars_in_goal(CalledGoal, Subn, Goal).

%-----------------------------------------------------------------------------%

	% inlining__inlining_in_disj is used for both disjunctions and
	% parallel conjunctions.

:- pred inlining__inlining_in_disj(list(hlds_goal), list(hlds_goal), 
		inline_info, inline_info).
:- mode inlining__inlining_in_disj(in, out, in, out) is det.

inlining__inlining_in_disj([], []) --> [].
inlining__inlining_in_disj([Goal0 | Goals0], [Goal | Goals]) -->
	inlining__inlining_in_goal(Goal0, Goal),
	inlining__inlining_in_disj(Goals0, Goals).

%-----------------------------------------------------------------------------%

:- pred inlining__inlining_in_cases(list(case), list(case), inline_info, 
		inline_info).
:- mode inlining__inlining_in_cases(in, out, in, out) is det.

inlining__inlining_in_cases([], []) --> [].
inlining__inlining_in_cases([case(Cons, Goal0) | Goals0],
		[case(Cons, Goal) | Goals]) -->
	inlining__inlining_in_goal(Goal0, Goal),
	inlining__inlining_in_cases(Goals0, Goals).

%-----------------------------------------------------------------------------%

:- pred inlining__inlining_in_conj(list(hlds_goal), list(hlds_goal),
		inline_info, inline_info).
:- mode inlining__inlining_in_conj(in, out, in, out) is det.

	% Since a single goal may become a conjunction,
	% we flatten the conjunction as we go.

inlining__inlining_in_conj([], []) --> [].
inlining__inlining_in_conj([Goal0 | Goals0], Goals) -->
	inlining__inlining_in_goal(Goal0, Goal1),
	{ goal_to_conj_list(Goal1, Goal1List) },
	inlining__inlining_in_conj(Goals0, Goals1),
	{ list__append(Goal1List, Goals1, Goals) }.

%-----------------------------------------------------------------------------%

	% Check to see if we should inline a call.
	%
	% Fails if the called predicate cannot be inlined,
	% e.g. because it is a builtin, we don't have code for it,
	% it uses nondet pragma c_code, etc.
	%
	% It succeeds if the called procedure is inlinable,
	% and in addition either there was a `pragma inline'
	% for this procedure, or the procedure was marked by
	% inlining__mark_predproc as having met its heuristic.

:- pred inlining__should_inline_proc(pred_id, proc_id, builtin_state,
	bool, bool, set(pred_proc_id), pred_markers, module_info).
:- mode inlining__should_inline_proc(in, in, in, in, in, in, in, in)
	is semidet.

inlining__should_inline_proc(PredId, ProcId, BuiltinState, HighLevelCode,
		Tracing, InlinedProcs, CallingPredMarkers, ModuleInfo) :-
	InlinePromisedPure = yes,
	inlining__can_inline_proc(PredId, ProcId, BuiltinState,
		HighLevelCode, Tracing, InlinePromisedPure,
		CallingPredMarkers, ModuleInfo),

	% OK, we could inline it - but should we?  Apply our heuristic.

	(
		module_info_pred_info(ModuleInfo, PredId, PredInfo),
		pred_info_requested_inlining(PredInfo)
	;
		set__member(proc(PredId, ProcId), InlinedProcs)
	).

inlining__can_inline_proc(PredId, ProcId, BuiltinState, InlinePromisedPure,
		CallingPredMarkers, ModuleInfo) :-
	module_info_globals(ModuleInfo, Globals),
	globals__lookup_bool_option(Globals, highlevel_code, HighLevelCode), 
	globals__get_trace_level(Globals, TraceLevel),
	Tracing = bool__not(trace_level_is_none(TraceLevel)),
	inlining__can_inline_proc(PredId, ProcId, BuiltinState,
		HighLevelCode, Tracing, InlinePromisedPure,
		CallingPredMarkers, ModuleInfo).

:- pred inlining__can_inline_proc(pred_id, proc_id, builtin_state, bool,
	bool, bool, pred_markers, module_info).
:- mode inlining__can_inline_proc(in, in, in, in, in, in, in, in) is semidet.

inlining__can_inline_proc(PredId, ProcId, BuiltinState, HighLevelCode,
		Tracing, InlinePromisedPure, CallingPredMarkers, ModuleInfo) :-

	% don't inline builtins, the code generator will handle them
	BuiltinState = not_builtin,

	module_info_pred_proc_info(ModuleInfo, PredId, ProcId, PredInfo, 
		ProcInfo),

	% don't try to inline imported predicates, since we don't
	% have the code for them.
	\+ pred_info_is_imported(PredInfo),

	% this next line catches the case of locally defined
	% unification predicates for imported types.
	\+ (
		pred_info_is_pseudo_imported(PredInfo),
		hlds_pred__in_in_unification_proc_id(ProcId)
	),

	% Only try to inline procedures which are evaluated using
	% normal evaluation. Currently we can't inline procs evaluated
	% using any of the other methods because the code generator for
	% the methods can only handle whole procedures not code 
	% fragments.
	proc_info_eval_method(ProcInfo, eval_normal),
	
	% Don't inlining anything we have been specifically requested
	% not to inline.
	\+ pred_info_requested_no_inlining(PredInfo),

	% For the LLDS back-end,
	% under no circumstances inline model_non pragma c codes.
	% The resulting code would not work properly.
	proc_info_goal(ProcInfo, CalledGoal),
	\+ (
		HighLevelCode = no,
		CalledGoal = foreign_proc(_,_,_,_,_,_,_) - _,
		proc_info_interface_determinism(ProcInfo, Detism),
		( Detism = nondet ; Detism = multidet )
	),

	% XXX:
	% If tracing is enabled, then the code generator will need to figure
	% out the locations of typeinfos inside typeclass_infos. At the moment,
	% due to a bug, the algorithm for doing this figuring can cause a
	% compiler abort if we inline calls that have typeclass constraints.
	(
		Tracing = yes
	=>
		(
			pred_info_clauses_info(PredInfo, ClausesInfo),
			TypeClassInfoVarMap = ClausesInfo ^
				clause_typeclass_info_varmap,
			map__is_empty(TypeClassInfoVarMap)
		)
	),

	% Only inline foreign_code if it is appropriate for
	% the target language.
	module_info_globals(ModuleInfo, Globals),
	globals__get_target(Globals, Target),
	(
		(
		CalledGoal = foreign_proc(ForeignAttributes,
			_,_,_,_,_,_) - _,
		foreign_language(ForeignAttributes, ForeignLanguage)
		)
	=>
		ok_to_inline_language(ForeignLanguage, Target)
	),

	% Don't inline memoed Aditi predicates.
	pred_info_get_markers(PredInfo, CalledPredMarkers),
	\+ check_marker(CalledPredMarkers, aditi_memo),

	% Don't inline Aditi procedures into non-Aditi procedures,
	% since this could result in joins being performed by
	% backtracking rather than by more efficient methods in
	% the database.
	pred_info_get_markers(PredInfo, CalledPredMarkers),
	\+ (
		\+ check_marker(CallingPredMarkers, aditi),
		check_marker(CalledPredMarkers, aditi)
	),
	
	(
		InlinePromisedPure = yes
	;
		%
		% For some optimizations (such as deforestation)
		% we don't want to inline predicates which are
		% promised pure because the extra impurity propagated
		% through the goal will defeat any attempts at
		% optimization.
		%
		InlinePromisedPure = no,
		pred_info_get_promised_purity(PredInfo, (impure))
	).

	% Succeed iff it is appropriate to inline `pragma foreign_code'
	% in the specified language for the given compilation_target.
	% Generally that will only be the case if the target directly
	% supports inline code in that language.
:- pred ok_to_inline_language(foreign_language::in, compilation_target::in)
	is semidet.
ok_to_inline_language(c, c).
% ok_to_inline_language(il, il). % 
% XXX we need to fix the handling of parameter marhsalling for inlined code
% before we can enable this -- see the comments in
% ml_gen_ordinary_pragma_il_proc in ml_code_gen.m.
%
% ok_to_inline_language(java, java). % foreign_language = java not implemented
% ok_to_inline_language(asm, asm).   % foreign_language = asm not implemented
% We could define a language "C/C++" (c_slash_cplusplus) which was the
% intersection of "C" and "C++", and then we'd have
%	ok_to_inline_language(c_slash_cplusplus, c).
%	ok_to_inline_language(c_slash_cplusplus, cplusplus).

%-----------------------------------------------------------------------------%
%-----------------------------------------------------------------------------%