mercury/compiler/code_info.m

%---------------------------------------------------------------------------%
% Copyright (C) 1994-1998 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: code_info.m
%
% Main authors: conway, zs.
%
% This file defines the code_info type and various operations on it.
% The code_info structure is the 'state' of the code generator.
%
% This file is organized into eight submodules:
%
%	- the code_info structure and its access predicates
%	- simple wrappers around access predicates
%	- handling failure continuations
%	- handling liveness issues
%	- saving and restoring heap pointers, trail tickets etc
%	- interfacing to code_exprn
%	- managing the info required by garbage collection and value numbering
%	- managing stack slots
%
% Note: Any new "state" arguments (eg counters) that should be strictly
% threaded (for example the counter used for allocating new labels) will
% require changes to code_info__slap_code_info/3.
%
%---------------------------------------------------------------------------%
%---------------------------------------------------------------------------%

:- module code_info.

:- interface.

:- import_module hlds_module, hlds_pred, hlds_goal, llds, instmap, trace.
:- import_module continuation_info, prog_data, hlds_data, globals.

:- import_module bool, set, varset, list, map, term, std_util, assoc_list.

:- implementation.

:- import_module code_util, code_exprn, prog_out.
:- import_module arg_info, type_util, mode_util, options.

:- import_module set, varset, stack.
:- import_module string, require, char, bimap, tree, int.

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

	% Submodule for the code_info type and its access predicates.
	%
	% This submodule has the following components:
	%
	%	declarations for exported access predicates
	%	declarations for non-exported access predicates
	%	the definition of the type and the init predicate
	%	the definition of the get access predicates
	%	the definition of the set access predicates
	%
	% Please keep the order of mention of the various fields
	% consistent in each of these five components.

:- interface.

:- type code_info.

		% Create a new code_info structure.
:- pred code_info__init(varset, set(var), stack_slots, bool, globals,
	pred_id, proc_id, proc_info, instmap, follow_vars, module_info,
	int /* cell number */, code_info).
:- mode code_info__init(in, in, in, in, in, in, in, in, in, in, in, in,
	out) is det.

		% Get the variables for the current procedure.
:- pred code_info__get_varset(varset, code_info, code_info).
:- mode code_info__get_varset(out, in, out) is det.

		% Get the id of the predicate we are generating code for.
:- pred code_info__get_pred_id(pred_id, code_info, code_info).
:- mode code_info__get_pred_id(out, in, out) is det.

		% Get the id of the procedure we are generating code for.
:- pred code_info__get_proc_id(proc_id, code_info, code_info).
:- mode code_info__get_proc_id(out, in, out) is det.

		% Get the HLDS of the procedure we are generating code for.
:- pred code_info__get_proc_info(proc_info, code_info, code_info).
:- mode code_info__get_proc_info(out, in, out) is det.

		% Get the flag that indicates whether succip is used or not.
:- pred code_info__get_succip_used(bool, code_info, code_info).
:- mode code_info__get_succip_used(out, in, out) is det.

		% Get the HLDS of the entire module.
:- pred code_info__get_module_info(module_info, code_info, code_info).
:- mode code_info__get_module_info(out, in, out) is det.

		% Get the set of currently forward-live variables.
:- pred code_info__get_forward_live_vars(set(var), code_info, code_info).
:- mode code_info__get_forward_live_vars(out, in, out) is det.

		% Set the set of currently forward-live variables.
:- pred code_info__set_forward_live_vars(set(var), code_info, code_info).
:- mode code_info__set_forward_live_vars(in, in, out) is det.

		% Get the table mapping variables to the current
		% instantiation states.
:- pred code_info__get_instmap(instmap, code_info, code_info).
:- mode code_info__get_instmap(out, in, out) is det.

		% Set the table mapping variables to the current
		% instantiation states.
:- pred code_info__set_instmap(instmap, code_info, code_info).
:- mode code_info__set_instmap(in, in, out) is det.

		% Get the globals table.
:- pred code_info__get_globals(globals, code_info, code_info).
:- mode code_info__get_globals(out, in, out) is det.

:- pred code_info__get_layout_info(map(label, internal_layout_info), 
		code_info, code_info).
:- mode code_info__get_layout_info(out, in, out) is det.

:- pred code_info__get_maybe_trace_info(maybe(trace_info),
		code_info, code_info).
:- mode code_info__get_maybe_trace_info(out, in, out) is det.

:- pred code_info__set_maybe_trace_info(maybe(trace_info), 
		code_info, code_info).
:- mode code_info__set_maybe_trace_info(in, in, out) is det.

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

:- implementation.

:- pred code_info__get_var_slot_count(int, code_info, code_info).
:- mode code_info__get_var_slot_count(out, in, out) is det.

:- pred code_info__get_label_count(int, code_info, code_info).
:- mode code_info__get_label_count(out, in, out) is det.

:- pred code_info__set_label_count(int, code_info, code_info).
:- mode code_info__set_label_count(in, in, out) is det.

:- pred code_info__set_cell_count(int, code_info, code_info).
:- mode code_info__set_cell_count(in, in, out) is det.

:- pred code_info__get_exprn_info(exprn_info, code_info, code_info).
:- mode code_info__get_exprn_info(out, in, out) is det.

:- pred code_info__set_exprn_info(exprn_info, code_info, code_info).
:- mode code_info__set_exprn_info(in, in, out) is det.

:- pred code_info__set_succip_used(bool, code_info, code_info).
:- mode code_info__set_succip_used(in, in, out) is det.

:- pred code_info__get_fail_stack(fail_stack, code_info, code_info).
:- mode code_info__get_fail_stack(out, in, out) is det.

:- pred code_info__set_fail_stack(fail_stack, code_info, code_info).
:- mode code_info__set_fail_stack(in, in, out) is det.

:- pred code_info__get_avail_temp_slots(set(lval), code_info, code_info).
:- mode code_info__get_avail_temp_slots(out, in, out) is det.

:- pred code_info__set_avail_temp_slots(set(lval), code_info, code_info).
:- mode code_info__set_avail_temp_slots(in, in, out) is det.

:- pred code_info__get_max_temp_slot_count(int, code_info, code_info).
:- mode code_info__get_max_temp_slot_count(out, in, out) is det.

:- pred code_info__set_max_temp_slot_count(int, code_info, code_info).
:- mode code_info__set_max_temp_slot_count(in, in, out) is det.

:- pred code_info__get_temps_in_use(map(lval, slot_contents),
	code_info, code_info).
:- mode code_info__get_temps_in_use(out, in, out) is det.

:- pred code_info__set_temps_in_use(map(lval, slot_contents),
	code_info, code_info).
:- mode code_info__set_temps_in_use(in, in, out) is det.

:- pred code_info__set_layout_info(map(label, internal_layout_info), 
		code_info, code_info).
:- mode code_info__set_layout_info(in, in, out) is det.

:- pred code_info__get_zombies(set(var), code_info, code_info).
:- mode code_info__get_zombies(out, in, out) is det.

:- pred code_info__set_zombies(set(var), code_info, code_info).
:- mode code_info__set_zombies(in, in, out) is det.

:- pred code_info__get_resume_point_stack(stack(set(var)),
	code_info, code_info).
:- mode code_info__get_resume_point_stack(out, in, out) is det.

:- pred code_info__set_resume_point_stack(stack(set(var)),
	code_info, code_info).
:- mode code_info__set_resume_point_stack(in, in, out) is det.

:- pred code_info__get_commit_triple_count(int, code_info, code_info).
:- mode code_info__get_commit_triple_count(out, in, out) is det.

:- pred code_info__set_commit_triple_count(int, code_info, code_info).
:- mode code_info__set_commit_triple_count(in, in, out) is det.

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

:- type code_info	--->
		code_info(
			int,		% The number of stack slots allocated.
					% for storing variables.
					% (Some extra stack slots are used
					% for saving and restoring registers.)
			int,		% Counter for the local labels used
					% by this procedure.
			varset,		% The variables in this procedure.
			pred_id,	% The label of the current predicate.
			proc_id,	% The label of the current procedure.
			int,		% Counter for cells in this proc.
			exprn_info,	% A map storing the information about
					% the status of each variable.
			proc_info,	% The proc_info for the this procedure.
			bool,		% do we need to store succip?
			fail_stack,	% The failure continuation stack
			module_info,	% The module_info structure - you just
					% never know when you might need it.
					% It should be read-only.
			set(var),	% Variables that are forward live
					% after this goal
			instmap,	% insts of variables
			set(lval),	% Stack variables that have been used
					% for temporaries and are now again
					% available for reuse.
			int,		% The maximum number of extra
					% temporary stackslots that have been
					% used during the procedure
			globals,	% code generation options
			map(lval, slot_contents),
					% The temp locations in use on the stack
					% and what they contain (for gc).
			map(label, internal_layout_info),	
					% Information on which values
					% are live and where at which labels,
					% for tracing and/or accurate gc.
			set(var),	% Zombie variables; variables that have
					% been killed but are protected by a
					% resume point.
			stack(set(var)),
					% Each resumption point has an
					% associated set of variables
					% whose values may be needed on
					% resumption at that point.
					% This field gives those variables
					% for a nested set of resumption
					% points. Each element must be
					% a superset of the ones below.
					% When a variable included in the top
					% set becomes no longer forward live,
					% we must save its value to the stack.
			int,
					% A count of how many triples of
					% curfr, maxfr and redoip are live on
					% the det stack. These triples are
					% pushed onto the det stack when
					% generating code for commits within
					% model_non procedures. The value
					% numbering pass and the accurate
					% garbage collector need to know about
					% these slots.  (Triple is a misnomer:
					% in grades with trailing, it is four.)
			maybe(trace_info)
					% Information about which stack slots
					% the call sequence number and depth
					% are stored, provided tracing is
					% switched on.
	).

:- type slot_contents 
	--->	ticket			% a ticket (trail pointer)
	;	ticket_counter		% a copy of the ticket counter
	;	trace_data
	;	lval(lval).

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

code_info__init(Varset, Liveness, StackSlots, SaveSuccip, Globals,
		PredId, ProcId, ProcInfo, Requests, FollowVars,
		ModuleInfo, CellCount, C) :-
	proc_info_headvars(ProcInfo, HeadVars),
	proc_info_arg_info(ProcInfo, ArgInfos),
	assoc_list__from_corresponding_lists(HeadVars, ArgInfos, Args),
	arg_info__build_input_arg_list(Args, ArgList),
	globals__get_options(Globals, Options),
	code_exprn__init_state(ArgList, Varset, StackSlots, FollowVars,
		Options, ExprnInfo),
	stack__init(Continue),
	stack__init(ResumeSetStack0),
	set__init(AvailSlots0),
	map__init(TempsInUse0),
	set__init(Zombies0),
	map__init(Shapes),
	code_info__max_var_slot(StackSlots, VarSlotCount0),
	proc_info_interface_code_model(ProcInfo, CodeModel),
	(
		CodeModel = model_non
	->
		VarSlotCount is VarSlotCount0 + 1
	;
		VarSlotCount = VarSlotCount0
	),
	C = code_info(
		VarSlotCount,
		0,
		Varset,
		PredId,
		ProcId,
		CellCount,
		ExprnInfo,
		ProcInfo,
		SaveSuccip,
		Continue,
		ModuleInfo,
		Liveness,
		Requests,
		AvailSlots0,
		0,
		Globals,
		TempsInUse0,
		Shapes,
		Zombies0,
		ResumeSetStack0,
		0,
		no
	).

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

code_info__get_var_slot_count(A, CI, CI) :-
	CI = code_info(A, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _,
		_, _, _).

code_info__get_label_count(B, CI, CI) :-
	CI = code_info(_, B, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _,
		_, _, _).

code_info__get_varset(C, CI, CI) :-
	CI = code_info(_, _, C, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _,
		_, _, _).

code_info__get_pred_id(D, CI, CI) :-
	CI = code_info(_, _, _, D, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _,
		_, _, _).

code_info__get_proc_id(E, CI, CI) :-
	CI = code_info(_, _, _, _, E, _, _, _, _, _, _, _, _, _, _, _, _, _, _,
		_, _, _).

code_info__get_cell_count(F, CI, CI) :-
	CI = code_info(_, _, _, _, _, F, _, _, _, _, _, _, _, _, _, _, _, _, _,
		_, _, _).

code_info__get_exprn_info(G, CI, CI) :-
	CI = code_info(_, _, _, _, _, _, G, _, _, _, _, _, _, _, _, _, _, _, _,
		_, _, _).

code_info__get_proc_info(H, CI, CI) :-
	CI = code_info(_, _, _, _, _, _, _, H, _, _, _, _, _, _, _, _, _, _, _,
		_, _, _).

code_info__get_succip_used(I, CI, CI) :-
	CI = code_info(_, _, _, _, _, _, _, _, I, _, _, _, _, _, _, _, _, _, _,
		_, _, _).

code_info__get_fail_stack(J, CI, CI) :-
	CI = code_info(_, _, _, _, _, _, _, _, _, J, _, _, _, _, _, _, _, _, _,
		_, _, _).

code_info__get_module_info(K, CI, CI) :-
	CI = code_info(_, _, _, _, _, _, _, _, _, _, K, _, _, _, _, _, _, _, _,
		_, _, _).

code_info__get_forward_live_vars(L, CI, CI) :-
	CI = code_info(_, _, _, _, _, _, _, _, _, _, _, L, _, _, _, _, _, _, _,
		_, _, _).

code_info__get_instmap(M, CI, CI) :-
	CI = code_info(_, _, _, _, _, _, _, _, _, _, _, _, M, _, _, _, _, _, _,
		_, _, _).

code_info__get_avail_temp_slots(N, CI, CI) :-
	CI = code_info(_, _, _, _, _, _, _, _, _, _, _, _, _, N, _, _, _, _, _,
		_, _, _).

code_info__get_max_temp_slot_count(O, CI, CI) :-
	CI = code_info(_, _, _, _, _, _, _, _, _, _, _, _, _, _, O, _, _, _, _,
		_, _, _).

code_info__get_globals(P, CI, CI) :-
	CI = code_info(_, _, _, _, _, _, _, _, _, _, _, _, _, _, _, P, _, _, _,
		_, _, _).

code_info__get_temps_in_use(Q, CI, CI) :-
	CI = code_info(_, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, Q, _, _,
		_, _, _).

code_info__get_layout_info(R, CI, CI) :-
	CI = code_info(_, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, R, _,
		_, _, _).

code_info__get_zombies(S, CI, CI) :-
	CI = code_info(_, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, S,
		_, _, _).

code_info__get_resume_point_stack(T, CI, CI) :-
	CI = code_info(_, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _,
		T, _, _).

code_info__get_commit_triple_count(U, CI, CI) :-
	CI = code_info(_, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _,
		_, U, _).

code_info__get_maybe_trace_info(V, CI, CI) :-
	CI = code_info(_, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _,
		_, _, V).

% :- type code_info	--->
%		code_info(
%	A		int,		% The number of stack slots allocated.
%					% for storing variables.
%					% (Some extra stack slots are used
%					% for saving and restoring registers.)
%	B		int,		% Counter for the local labels used
%					% by this procedure.
%	C		varset,		% The variables in this procedure.
%	D		pred_id,	% The label of the current predicate.
%	E		proc_id,	% The label of the current procedure.
%	F		int,		% Counter for cells in this proc.
%	G		exprn_info,	% A map storing the information about
%					% the status of each variable.
%	H		proc_info,	% The proc_info for the this procedure.
%	I		bool,		% do we need to store succip?
%	J		fail_stack,	% The failure continuation stack
%	K		module_info,	% The module_info structure - you just
%					% never know when you might need it.
%					% It should be read-only.
%	L		set(var),	% Variables that are forward live
%					% after this goal
%	M		instmap,	% insts of variables
%	N		set(lval),	% Stack variables that have been used
%					% for temporaries and are now again
%					% available for reuse.
%	O		int,		% The maximum number of extra
%					% temporary stackslots that have been
%					% used during the procedure
%	P		globals,	% code generation options
%	Q		map(lval, slot_contents),
%					% The temp locations in use on the stack
%					% and what they contain (for gc).
%	R		map(label, internal_layout_info),	
%					% Information on which values
%					% are live and where at which labels,
%					% for tracing and/or accurate gc.
%	S		set(var),	% Zombie variables; variables that have
%					% been killed but are protected by a
%					% resume point.
%	T		stack(set(var)),
%					% Each resumption point has an
%					% associated set of variables
%					% whose values may be needed on
%					% resumption at that point.
%					% This field gives those variables
%					% for a nested set of resumption
%					% points. Each element must be
%					% a superset of the ones below.
%					% When a variable included in the top
%					% set becomes no longer forward live,
%					% we must save its value to the stack.
%	U		int,
%					% A count of how many triples of
%					% curfr, maxfr and redoip are live on
%					% the det stack. These triples are
%					% pushed onto the det stack when
%					% generating code for commits within
%					% model_non procedures. The value
%					% numbering pass and the accurate
%					% garbage collector need to know about
%					% these slots.  (Triple is a misnomer:
%					% in grades with trailing, it is four.)
%	V		maybe(trace_info)
%					% Information about which stack slots
%					% the call sequence number and depth
%					% are stored, provided tracing is
%					% switched on.
%	).
%
% we don't need
% code_info__set_var_slot_count
% code_info__set_varset
% code_info__set_pred_id
% code_info__set_proc_id
% code_info__set_module_info
% code_info__set_globals
% code_info__set_code_model

code_info__set_label_count(B, CI0, CI) :-
	CI0 = code_info(A, _, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q,
		R, S, T, U, V),
	CI = code_info(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q,
		R, S, T, U, V).

code_info__set_cell_count(F, CI0, CI) :-
	CI0 = code_info(A, B, C, D, E, _, G, H, I, J, K, L, M, N, O, P, Q,
		R, S, T, U, V),
	CI = code_info(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q,
		R, S, T, U, V).

code_info__set_exprn_info(G, CI0, CI) :-
	CI0 = code_info(A, B, C, D, E, F, _, H, I, J, K, L, M, N, O, P, Q,
		R, S, T, U, V),
	CI = code_info(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q,
		R, S, T, U, V).

code_info__set_succip_used(I, CI0, CI) :-
	CI0 = code_info(A, B, C, D, E, F, G, H, _, J, K, L, M, N, O, P, Q,
		R, S, T, U, V),
	CI = code_info(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q,
		R, S, T, U, V).

code_info__set_fail_stack(J, CI0, CI) :-
	CI0 = code_info(A, B, C, D, E, F, G, H, I, _, K, L, M, N, O, P, Q,
		R, S, T, U, V),
	CI = code_info(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q,
		R, S, T, U, V).

code_info__set_forward_live_vars(L, CI0, CI) :-
	CI0 = code_info(A, B, C, D, E, F, G, H, I, J, K, _, M, N, O, P, Q,
		R, S, T, U, V),
	CI = code_info(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q,
		R, S, T, U, V).

code_info__set_instmap(M, CI0, CI) :-
	CI0 = code_info(A, B, C, D, E, F, G, H, I, J, K, L, _, N, O, P, Q,
		R, S, T, U, V),
	CI = code_info(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q,
		R, S, T, U, V).

code_info__set_avail_temp_slots(N, CI0, CI) :-
	CI0 = code_info(A, B, C, D, E, F, G, H, I, J, K, L, M, _, O, P, Q,
		R, S, T, U, V),
	CI = code_info(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q,
		R, S, T, U, V).

code_info__set_max_temp_slot_count(O, CI0, CI) :-
	CI0 = code_info(A, B, C, D, E, F, G, H, I, J, K, L, M, N, _, P, Q,
		R, S, T, U, V),
	CI = code_info(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q,
		R, S, T, U, V).

code_info__set_temps_in_use(Q, CI0, CI) :-
	CI0 = code_info(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, _,
		R, S, T, U, V),
	CI = code_info(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q,
		R, S, T, U, V).

code_info__set_layout_info(R, CI0, CI) :-
	CI0 = code_info(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q,
		_, S, T, U, V),
	CI = code_info(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q,
		R, S, T, U, V).

code_info__set_zombies(S, CI0, CI) :-
	CI0 = code_info(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q,
		R, _, T, U, V),
	CI = code_info(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q,
		R, S, T, U, V).

code_info__set_resume_point_stack(T, CI0, CI) :-
	CI0 = code_info(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q,
		R, S, _, U, V),
	CI = code_info(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q,
		R, S, T, U, V).

code_info__set_commit_triple_count(U, CI0, CI) :-
	CI0 = code_info(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q,
		R, S, T, _, V),
	CI = code_info(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q,
		R, S, T, U, V).

code_info__set_maybe_trace_info(V, CI0, CI) :-
	CI0 = code_info(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q,
		R, S, T, U, _),
	CI = code_info(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q,
		R, S, T, U, V).

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

	% Submodule for simple wrappers around access predicates.

:- interface.

		% Get the hlds mapping from variables to stack slots
:- pred code_info__get_stack_slots(stack_slots, code_info, code_info).
:- mode code_info__get_stack_slots(out, in, out) is det.

		% Get the table that contains advice about where
		% variables should be put.
:- pred code_info__get_follow_vars(follow_vars, code_info, code_info).
:- mode code_info__get_follow_vars(out, in, out) is det.

		% Set the table that contains advice about where
		% variables should be put.
:- pred code_info__set_follow_vars(follow_vars, code_info, code_info).
:- mode code_info__set_follow_vars(in, in, out) is det.

	% code_info__pre_goal_update(GoalInfo, Atomic, OldCodeInfo, NewCodeInfo)
	% updates OldCodeInfo to produce NewCodeInfo with the changes
	% specified by GoalInfo.
:- pred code_info__pre_goal_update(hlds_goal_info, bool, code_info, code_info).
:- mode code_info__pre_goal_update(in, in, in, out) is det.

	% code_info__post_goal_update(GoalInfo, OldCodeInfo, NewCodeInfo)
	% updates OldCodeInfo to produce NewCodeInfo with the changes described
	% by GoalInfo.
:- pred code_info__post_goal_update(hlds_goal_info, code_info, code_info).
:- mode code_info__post_goal_update(in, in, out) is det.

	% Find out the type of the given variable.
:- pred code_info__variable_type(var, type, code_info, code_info).
:- mode code_info__variable_type(in, out, in, out) is det.

:- pred code_info__lookup_type_defn(type, hlds_type_defn,
	code_info, code_info).
:- mode code_info__lookup_type_defn(in, out, in, out) is det.

	% Given a list of type variables, find the lvals where the
	% corresponding type_infos and typeclass_infos are being stored.
:- pred code_info__find_type_infos(list(var), assoc_list(var, lval), 
	code_info, code_info).
:- mode code_info__find_type_infos(in, out, in, out) is det.

	% Given a constructor id, and a variable (so that we can work out the
	% type of the constructor), determine correct tag (representation)
	% of that constructor.
:- pred code_info__cons_id_to_tag(var, cons_id, cons_tag, code_info, code_info).
:- mode code_info__cons_id_to_tag(in, in, out, in, out) is det.

	% Get the code model of the current procedure.
:- pred code_info__get_proc_model(code_model, code_info, code_info).
:- mode code_info__get_proc_model(out, in, out) is det.

:- pred code_info__get_headvars(list(var), code_info, code_info).
:- mode code_info__get_headvars(out, in, out) is det.

	% Get the call argument information for the current procedure
:- pred code_info__get_arginfo(list(arg_info), code_info, code_info).
:- mode code_info__get_arginfo(out, in, out) is det.

	% Get the call argument info for a given mode of a given predicate
:- pred code_info__get_pred_proc_arginfo(pred_id, proc_id, list(arg_info),
	code_info, code_info).
:- mode code_info__get_pred_proc_arginfo(in, in, out, in, out) is det.

	% Pop the failure continuation stack.
:- pred code_info__pop_failure_cont(code_info, code_info).
:- mode code_info__pop_failure_cont(in, out) is det.

:- pred code_info__push_resume_point_vars(set(var), code_info, code_info).
:- mode code_info__push_resume_point_vars(in, in, out) is det.

:- pred code_info__pop_resume_point_vars(code_info, code_info).
:- mode code_info__pop_resume_point_vars(in, out) is det.

:- pred code_info__variable_to_string(var, string, code_info, code_info).
:- mode code_info__variable_to_string(in, out, in, out) is det.

:- pred code_info__grab_code_info(code_info, code_info, code_info).
:- mode code_info__grab_code_info(out, in, out) is det.

:- pred code_info__slap_code_info(code_info, code_info, code_info).
:- mode code_info__slap_code_info(in, in, out) is det.

:- pred code_info__apply_instmap_delta(instmap_delta, code_info, code_info).
:- mode code_info__apply_instmap_delta(in, in, out) is det.

	% Create a code address which holds the address of the specified
	% procedure.
	% The fourth argument should be `no' if the the caller wants the
	% returned address to be valid from everywhere in the program.
	% If being valid from within the current procedure is enough,
	% this argument should be `yes' wrapped around the value of the
	% --procs-per-c-function option and the current procedure id.
	% Using an address that is only valid from within the current
	% procedure may make jumps more efficient.
	% XXX
:- pred code_info__make_entry_label(module_info, pred_id, proc_id, bool,
	code_addr, code_info, code_info).
:- mode code_info__make_entry_label(in, in, in, in, out, in, out) is det.

	% Generate the next local label in sequence.
:- pred code_info__get_next_label(label, code_info, code_info).
:- mode code_info__get_next_label(out, in, out) is det.

	% Generate the next cell number in sequence.
:- pred code_info__get_next_cell_number(int, code_info, code_info).
:- mode code_info__get_next_cell_number(out, in, out) is det.

	% Get the current cell number.
:- pred code_info__get_cell_count(int, code_info, code_info).
:- mode code_info__get_cell_count(out, in, out) is det.

:- pred code_info__succip_is_used(code_info, code_info).
:- mode code_info__succip_is_used(in, out) is det.

:- pred code_info__add_layout_for_label(label, internal_layout_info,
	code_info, code_info).
:- mode code_info__add_layout_for_label(in, in, in, out) is det.

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

:- implementation.

:- pred code_info__push_failure_cont(failure_cont, code_info, code_info).
:- mode code_info__push_failure_cont(in, in, out) is det.

	% Lookup the value on the top of the failure continuation stack

:- pred code_info__top_failure_cont(failure_cont, code_info, code_info).
:- mode code_info__top_failure_cont(out, in, out) is det.

:- pred code_info__current_resume_point_vars(set(var), code_info, code_info).
:- mode code_info__current_resume_point_vars(out, in, out) is det.

:- pred code_info__add_commit_triple(code_info, code_info).
:- mode code_info__add_commit_triple(in, out) is det.

:- pred code_info__rem_commit_triple(code_info, code_info).
:- mode code_info__rem_commit_triple(in, out) is det.

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

code_info__get_stack_slots(StackSlots, CI, CI) :-
	code_info__get_exprn_info(ExprnInfo, CI, _),
	code_exprn__get_stack_slots(StackSlots, ExprnInfo, _).

code_info__get_follow_vars(FollowVars, CI, CI) :-
	code_info__get_exprn_info(ExprnInfo, CI, _),
	code_exprn__get_follow_vars(FollowVars, ExprnInfo, _).

code_info__set_follow_vars(FollowVars, CI0, CI) :-
	code_info__get_exprn_info(ExprnInfo0, CI0, _),
	code_exprn__set_follow_vars(FollowVars, ExprnInfo0, ExprnInfo),
	code_info__set_exprn_info(ExprnInfo, CI0, CI).

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

	% Update the code info structure to be consistent
	% immediately prior to generating a goal
code_info__pre_goal_update(GoalInfo, Atomic) -->
	% The liveness pass puts resume_point annotations on some kinds
	% of goals. The parts of the code generator that handle those kinds
	% of goals should handle the resume point annotation as well;
	% when they do, they remove the annotation. The following code
	% is a sanity check to make sure that this has in fact been done.
	{ goal_info_get_resume_point(GoalInfo, ResumePoint) },
	(
		{ ResumePoint = no_resume_point }
	;
		{ ResumePoint = resume_point(_, _) },
		{ error("pre_goal_update with resume point") }
	),
	{ goal_info_get_follow_vars(GoalInfo, MaybeFollowVars) },
	(
		{ MaybeFollowVars = yes(FollowVars) },
		code_info__set_follow_vars(FollowVars)
	;
		{ MaybeFollowVars = no }
	),
	% note: we must be careful to apply deaths before births
	{ goal_info_get_pre_deaths(GoalInfo, PreDeaths) },
	code_info__rem_forward_live_vars(PreDeaths),
	code_info__make_vars_forward_dead(PreDeaths),
	{ goal_info_get_pre_births(GoalInfo, PreBirths) },
	code_info__add_forward_live_vars(PreBirths),
	( { Atomic = yes } ->
		{ goal_info_get_post_deaths(GoalInfo, PostDeaths) },
		code_info__rem_forward_live_vars(PostDeaths)
	;
		[]
	).

	% Update the code info structure to be consistent
	% immediately after generating a goal
code_info__post_goal_update(GoalInfo) -->
	% note: we must be careful to apply deaths before births
	{ goal_info_get_post_deaths(GoalInfo, PostDeaths) },
	code_info__rem_forward_live_vars(PostDeaths),
	code_info__make_vars_forward_dead(PostDeaths),
	{ goal_info_get_post_births(GoalInfo, PostBirths) },
	code_info__add_forward_live_vars(PostBirths),
	code_info__make_vars_forward_live(PostBirths),
	{ goal_info_get_instmap_delta(GoalInfo, InstMapDelta) },
	code_info__apply_instmap_delta(InstMapDelta).

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

code_info__variable_type(Var, Type) -->
	code_info__get_proc_info(ProcInfo),
	{ proc_info_vartypes(ProcInfo, VarTypes) },
	{ map__lookup(VarTypes, Var, Type) }.

code_info__lookup_type_defn(Type, TypeDefn) -->
	code_info__get_module_info(ModuleInfo),
	{ type_to_type_id(Type, TypeIdPrime, _) ->
		TypeId = TypeIdPrime
	;
		error("unknown type in code_aux__lookup_type_defn")
	},
	{ module_info_types(ModuleInfo, TypeTable) },
	{ map__lookup(TypeTable, TypeId, TypeDefn) }.

code_info__find_type_infos([], []) --> [].
code_info__find_type_infos([TVar | TVars], [TVar - Lval | Lvals]) -->
	code_info__get_proc_info(ProcInfo),
	{ proc_info_typeinfo_varmap(ProcInfo, TypeInfoMap) },
	{
		map__search(TypeInfoMap, TVar, Locn)
	->
		type_info_locn_var(Locn, Var)
	;
		error("cannot find var for type variable")
	},
	{ proc_info_stack_slots(ProcInfo, StackSlots) },
	(
		{ map__search(StackSlots, Var, Lval0) }
	->
		{ Lval = Lval0 }
	;
		code_info__variable_to_string(Var, VarString),
		{ string__format("code_info__find_type_infos: can't find lval for type_info var %s",
			[s(VarString)], ErrStr) },
		{ error(ErrStr) }
	),
	code_info__find_type_infos(TVars, Lvals).

code_info__cons_id_to_tag(Var, ConsId, ConsTag) -->
	code_info__variable_type(Var, Type),
	code_info__get_module_info(ModuleInfo),
	{ code_util__cons_id_to_tag(ConsId, Type, ModuleInfo, ConsTag) }.

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

code_info__get_proc_model(CodeModel) -->
	code_info__get_proc_info(ProcInfo),
	{ proc_info_interface_code_model(ProcInfo, CodeModel) }.

code_info__get_headvars(HeadVars) -->
	code_info__get_module_info(ModuleInfo),
	code_info__get_pred_id(PredId),
	code_info__get_proc_id(ProcId),
	{ module_info_preds(ModuleInfo, Preds) },
	{ map__lookup(Preds, PredId, PredInfo) },
	{ pred_info_procedures(PredInfo, Procs) },
	{ map__lookup(Procs, ProcId, ProcInfo) },
	{ proc_info_headvars(ProcInfo, HeadVars) }.

code_info__get_arginfo(ArgInfo) -->
	code_info__get_pred_id(PredId),
	code_info__get_proc_id(ProcId),
	code_info__get_pred_proc_arginfo(PredId, ProcId, ArgInfo).

code_info__get_pred_proc_arginfo(PredId, ProcId, ArgInfo) -->
	code_info__get_module_info(ModuleInfo),
	{ module_info_pred_proc_info(ModuleInfo, PredId, ProcId, _, ProcInfo) },
	{ proc_info_arg_info(ProcInfo, ArgInfo) }.

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

code_info__push_failure_cont(Cont) -->
	code_info__get_fail_stack(Fall0),
	{ stack__push(Fall0, Cont, Fall) },
	code_info__set_fail_stack(Fall).

code_info__pop_failure_cont -->
	code_info__get_fail_stack(Fall0),
	( { stack__pop(Fall0, _, Fall) } ->
		code_info__set_fail_stack(Fall)
	;
		{ error("code_info__pop_failure_cont: empty stack") }
	).

code_info__top_failure_cont(Cont) -->
	code_info__get_fail_stack(Fall),
	( { stack__top(Fall, Cont0) } ->
		{ Cont = Cont0 }
	;
		{ error("code_info__failure_cont: no failure continuation") }
	).

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

code_info__current_resume_point_vars(ResumeVars) -->
	code_info__get_resume_point_stack(ResumeStack),
	{ stack__top(ResumeStack, TopVars) ->
		ResumeVars = TopVars
	;
		set__init(ResumeVars)
	}.

code_info__push_resume_point_vars(ResumeVars) -->
	code_info__get_resume_point_stack(ResumeStack0),
	{ stack__top(ResumeStack0, OldTopVars) ->
		require(set__subset(OldTopVars, ResumeVars),
		"new resume point variable set does not include old one")
	;
		true
	},
	{ stack__push(ResumeStack0, ResumeVars, ResumeStack) },
	code_info__set_resume_point_stack(ResumeStack).

code_info__pop_resume_point_vars -->
	code_info__get_resume_point_stack(ResumeStack0),
	{ stack__pop_det(ResumeStack0, _, ResumeStack) },
	code_info__set_resume_point_stack(ResumeStack).

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

code_info__add_commit_triple -->
	code_info__get_commit_triple_count(Count0),
	{ Count is Count0 + 1 },
	code_info__set_commit_triple_count(Count).

code_info__rem_commit_triple -->
	code_info__get_commit_triple_count(Count0),
	{ Count is Count0 - 1 },
	code_info__set_commit_triple_count(Count).

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

code_info__variable_to_string(Var, Name) -->
	code_info__get_varset(Varset),
	{ varset__lookup_name(Varset, Var, Name) }.

code_info__grab_code_info(C, C, C).

code_info__slap_code_info(C0, C1, C) :-
	code_info__get_label_count(L, C1, _),
	code_info__set_label_count(L, C0, C2),
	code_info__get_succip_used(S, C1, _),
	code_info__set_succip_used(S, C2, C3),
	code_info__get_fail_stack(J, C0, _),
	code_info__set_fail_stack(J, C3, C4),
	code_info__get_max_temp_slot_count(PC, C1, _),
	code_info__set_max_temp_slot_count(PC, C4, C5),
	code_info__get_layout_info(LayoutInfo, C1, _),
	code_info__set_layout_info(LayoutInfo, C5, C6),
	code_info__get_cell_count(CellCount, C1, _),
	code_info__set_cell_count(CellCount, C6, C).

code_info__apply_instmap_delta(Delta) -->
	code_info__get_instmap(InstMap0),
	{ instmap__apply_instmap_delta(InstMap0, Delta, InstMap) },
	code_info__set_instmap(InstMap).

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

code_info__make_entry_label(ModuleInfo, PredId, ProcId, Immed0, PredAddress) -->
	(
		{ Immed0 = no },
		{ Immed = no }
	;
		{ Immed0 = yes },
		code_info__get_globals(Globals),
		{ globals__lookup_int_option(Globals, procs_per_c_function,
			ProcsPerFunc) },
		code_info__get_pred_id(CurPredId),
		code_info__get_proc_id(CurProcId),
		{ Immed = yes(ProcsPerFunc - proc(CurPredId, CurProcId)) }
	),
	{ code_util__make_entry_label(ModuleInfo, PredId, ProcId, Immed,
		PredAddress) }.

code_info__get_next_label(Label) -->
	code_info__get_module_info(ModuleInfo),
	code_info__get_pred_id(PredId),
	code_info__get_proc_id(ProcId),
	code_info__get_label_count(N0),
	{ N is N0 + 1 },
	code_info__set_label_count(N),
	{ code_util__make_internal_label(ModuleInfo, PredId, ProcId, N,
		Label) }.

code_info__get_next_cell_number(N) -->
	code_info__get_cell_count(N0),
	{ N is N0 + 1 },
	code_info__set_cell_count(N).

code_info__succip_is_used -->
	code_info__set_succip_used(yes).

code_info__add_layout_for_label(Label, LayoutInfo) -->
	code_info__get_layout_info(Internals0),
	( { map__contains(Internals0, Label) } ->
		{ error("adding layout for already known label") }
	;
		{ map__det_insert(Internals0, Label, LayoutInfo, Internals) },
		code_info__set_layout_info(Internals)
	).

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

	% Submodule for the handling of failure continuations.

:- interface.

	% We manufacture a failure cont when we start generating
	% code for a proc because on the failure of a procedure
	% we don't need to prepare for execution to resume in this
	% procedure.

:- pred code_info__manufacture_failure_cont(bool, code_info, code_info).
:- mode code_info__manufacture_failure_cont(in, in, out) is det.

	% make_known_failure_cont(ResumeVars, ResumeLocs, IsNondet, Code):
	% Push a new failure continuation onto the stack.

:- pred code_info__make_known_failure_cont(set(var), resume_locs, bool,
	code_tree, code_info, code_info).
:- mode code_info__make_known_failure_cont(in, in, in, out, in, out)
	is det.

	% Generate some code to restore the current redoip, by looking
	% at the top of the failure continuation stack.

:- pred code_info__restore_failure_cont(code_tree, code_info, code_info).
:- mode code_info__restore_failure_cont(out, in, out) is det.

	% XXX

:- pred code_info__failure_is_direct_branch(code_addr, code_info, code_info).
:- mode code_info__failure_is_direct_branch(out, in, out) is semidet.

	% XXX

:- pred code_info__generate_failure(code_tree, code_info, code_info).
:- mode code_info__generate_failure(out, in, out) is det.

	% XXX

:- pred code_info__fail_if_rval_is_false(rval, code_tree,
	code_info, code_info).
:- mode code_info__fail_if_rval_is_false(in, out, in, out) is det.

	% Set the topmost failure cont to `unknown' (e.g. after
	% a nondet call or after a disjunction).

:- pred code_info__unset_failure_cont(code_tree, code_info, code_info).
:- mode code_info__unset_failure_cont(out, in, out) is det.

	% Flush the variables needed for any current resumption point
	% to their stack slots.

:- pred code_info__flush_resume_vars_to_stack(code_tree, code_info, code_info).
:- mode code_info__flush_resume_vars_to_stack(out, in, out) is det.

	% XXX

:- pred code_info__may_use_nondet_tailcall(bool, code_info, code_info).
:- mode code_info__may_use_nondet_tailcall(out, in, out) is det.

	% do_soft_cut(NondetFrameLvalAddress, SoftCutCode, SoftCutContCode)
	% takes the lval where the address of the
	% failure frame is stored, and it returns code to
	% prune away the topmost choice point from that frame,
	% typically by setting the redoip of that frame to do_fail.
	% Note that the frame need not be the topmost frame -- a soft cut
	% can prune away a single choice point from the middle.
	% do_soft_cut also returns some additional code; in the case of
	% trailing, the redoip will be set to point to that additional code,
	% not to do_fail; the additional code will do a `discard_ticket'
	% before branching to the usual failure continuation (e.g. do_fail).

:- pred code_info__do_soft_cut(lval, code_tree, code_tree,
			code_info, code_info).
:- mode code_info__do_soft_cut(in, out, out, in, out) is det.

	% `generate_semi_pre_commit' and `generate_semi_commit' should be
	% called before and after generating the code for the nondet goal
	% being cut across. If the goal succeeds, the `commit' will cut
	% any choice points generated in the goal.
	%
	% `generate_semi_pre_commit' returns a label (a failure cont label)
	% and a tuple of stack slots; both of these should be passed to
	% `generate_semi_commit'.

:- pred code_info__generate_semi_pre_commit(label, commit_slots, code_tree,
	code_info, code_info).
:- mode code_info__generate_semi_pre_commit(out, out, out, in, out) is det.

:- pred code_info__generate_semi_commit(label, commit_slots, code_tree,
	code_info, code_info).
:- mode code_info__generate_semi_commit(in, in, out, in, out) is det.

	% `generate_det_pre_commit' and `generate_det_commit' should be
	% called before and after generating the code for the multi goal
	% being cut across. If the goal succeeds, the `commit' will cut
	% any choice points generated in the goal.
	%
	% `generate_det_pre_commit' returns a tuple of stack slots, which
	% should be passed to `generate_det_commit'.

:- pred code_info__generate_det_pre_commit(commit_slots, code_tree,
	code_info, code_info).
:- mode code_info__generate_det_pre_commit(out, out, in, out) is det.

:- pred code_info__generate_det_commit(commit_slots, code_tree,
	code_info, code_info).
:- mode code_info__generate_det_commit(in, out, in, out) is det.

:- type commit_slots
	--->	commit_slots(
			lval,		% curfr
			lval,		% maxfr
			lval,		% redoip
			maybe(pair(lval, lval)) % ticket counter, trail pointer
		).

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

:- implementation.

:- type fail_stack	==	stack(failure_cont).

:- type failure_cont
	--->	failure_cont(
			failure_cont_info,
			resume_maps
		).

:- type failure_cont_info
	--->	semidet
	;	nondet(
			is_known,	% Says whether on failure we can branch
					% directly to one of the labels in
					% the resume_maps, or if we must
					% instead execute a redo.

			maybe(label)	% The maybe(label) is yes if we have
					% created a temporary frame and we
					% must restore curfr after a redo().
		).

:- type is_known	--->	known ; unknown.

:- type resume_map	==	map(var, set(rval)).

:- type resume_maps
	--->	orig_only(resume_map, code_addr)
	;	stack_only(resume_map, code_addr)
	;	orig_and_stack(resume_map, code_addr, resume_map, code_addr)
	;	stack_and_orig(resume_map, code_addr, resume_map, code_addr).

:- pred code_info__fail_cont_is_known(failure_cont_info).
:- mode code_info__fail_cont_is_known(in) is semidet.

code_info__fail_cont_is_known(FailContInfo) :-
	FailContInfo \= nondet(unknown, _).

:- pred code_info__fail_cont_is_unknown(failure_cont_info).
:- mode code_info__fail_cont_is_unknown(in) is semidet.

code_info__fail_cont_is_unknown(FailContInfo) :-
	FailContInfo = nondet(unknown, _).

:- pred code_info__have_temp_frame(fail_stack).
:- mode code_info__have_temp_frame(in) is semidet.

	% have_temp_frame should succeed iff we have created
	% a temp frame on the nondet stack.  It traverses
	% the entire failure continuation stack, looking for
	% any failure continuations with the temp frame maybe(label)
	% set to yes(_).

code_info__have_temp_frame(FailStack0) :-
	stack__pop(FailStack0, FailContInfo, FailStack1),
	(
		FailContInfo = failure_cont(nondet(_, yes(_)), _)
	;
		code_info__have_temp_frame(FailStack1)
	).

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

code_info__manufacture_failure_cont(IsNondet) -->
	{ map__init(Empty) },
	(
		{ IsNondet = no },
		code_info__get_next_label(ContLab1),
		{ Address1 = label(ContLab1) },
		{ ResumeMap = stack_only(Empty, Address1) },
		{ ContInfo = semidet }
	;
		{ IsNondet = yes },
		{ Address1 = do_fail },
		{ ResumeMap = stack_only(Empty, Address1) },
		{ ContInfo = nondet(known, no) }
	),
	code_info__push_failure_cont(failure_cont(ContInfo, ResumeMap)).

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

code_info__make_known_failure_cont(ResumeVars, ResumeLocs, IsNondet,
		ModContCode) -->
	code_info__get_next_label(OrigLabel),
	code_info__get_next_label(StackLabel),
	{ OrigAddr = label(OrigLabel) },
	{ StackAddr = label(StackLabel) },
	(
		% In semidet continuations we don't use the redoip
		% of the top stack frame.

		{ IsNondet = no },
		{ TempFrameCode = empty },
		{ FailContInfo = semidet }
	;
		% In nondet continuations we may use the redoip
		% of the top stack frame. Therefore we must ensure
		% that this redoip is free for use, creating our own
		% frame if necessary.

		{ IsNondet = yes },
		code_info__top_failure_cont(FailureCont),
		{ FailureCont = failure_cont(OrigInfo, _) },
		(
			{ code_info__fail_cont_is_unknown(OrigInfo) }
		->
			%
			% If the failure continuation is unknown,
			% then we need to create a new temporary frame
			% so that we can make it known
			%
			code_info__get_next_label(RedoLabel),
			{ MaybeRedoLabel = yes(RedoLabel) },
			{ RedoAddr = label(RedoLabel) },
				% this code could be better
				% (mkframe is a bit of a sledge hammer)
			{ TempFrameCode = node([
				mkframe("temp frame", 1, no, RedoAddr)
					- "create a temporary frame",
				assign(curfr, lval(succfr(lval(maxfr))))
					- "restore curfr after mkframe"
			]) }
		;
			%
			% The failure continuation is known.
			% But did we create a temp frame?
			%
			code_info__get_fail_stack(FailStack),
			(
				{ code_info__have_temp_frame(FailStack) }
			->
				%
				% If we created a temp frame, then
				% we will need to restore curfr on redo,
				% so we set the failure continuation to
				% the RedoAddr rather than the usual
				% StackAddr.  (generate_failure_cont will
				% generate code for it that restores curfr.)
				%
				code_info__get_next_label(RedoLabel),
				{ MaybeRedoLabel = yes(RedoLabel) },
				{ RedoAddr = label(RedoLabel) },
				{ TempFrameCode = node([
					assign(redoip(lval(maxfr)),
					    const(code_addr_const(RedoAddr)))
				    - "Set failure continuation on temp frame"
				]) }
			;
				{ MaybeRedoLabel = no },
				{ TempFrameCode = node([
					assign(redoip(lval(maxfr)),
					    const(code_addr_const(StackAddr)))
				    - "Set failure continuation"
				]) }
			)
		),
		{ FailContInfo = nondet(known, MaybeRedoLabel) }
	),
	{ set__to_sorted_list(ResumeVars, VarList) },
	(
		{ ResumeLocs = orig_only },
		code_info__produce_resume_vars(VarList, OrigMap, OrigCode),
		{ ResumeMaps = orig_only(OrigMap, OrigAddr) }
	;
		{ ResumeLocs = stack_only },
		code_info__produce_resume_vars(VarList, _OrigMap, OrigCode),
		code_info__get_stack_slots(StackSlots),
		{ map__select(StackSlots, ResumeVars, StackMap0) },
		{ map__to_assoc_list(StackMap0, StackList0) },
		{ code_info__tweak_stacklist(StackList0, StackList) },
		{ map__from_assoc_list(StackList, StackMap) },
		{ ResumeMaps = stack_only(StackMap, StackAddr) }
	;
		{ ResumeLocs = orig_and_stack },
		code_info__produce_resume_vars(VarList, OrigMap, OrigCode),
		code_info__get_stack_slots(StackSlots),
		{ map__select(StackSlots, ResumeVars, StackMap0) },
		{ map__to_assoc_list(StackMap0, StackList0) },
		{ code_info__tweak_stacklist(StackList0, StackList) },
		{ map__from_assoc_list(StackList, StackMap) },
		{ ResumeMaps = orig_and_stack(OrigMap, OrigAddr,
			StackMap, StackAddr) }
	;
		{ ResumeLocs = stack_and_orig },
		code_info__produce_resume_vars(VarList, OrigMap, OrigCode),
		code_info__get_stack_slots(StackSlots),
		{ map__select(StackSlots, ResumeVars, StackMap0) },
		{ map__to_assoc_list(StackMap0, StackList0) },
		{ code_info__tweak_stacklist(StackList0, StackList) },
		{ map__from_assoc_list(StackList, StackMap) },
		{ ResumeMaps = stack_and_orig(StackMap, StackAddr,
			OrigMap, OrigAddr) }
	),
	code_info__push_failure_cont(failure_cont(FailContInfo, ResumeMaps)),
	{ ModContCode = tree(OrigCode, TempFrameCode) }.

:- pred code_info__produce_resume_vars(list(var), map(var, set(rval)),
	code_tree, code_info, code_info).
:- mode code_info__produce_resume_vars(in, out, out, in, out) is det.

code_info__produce_resume_vars([], Map, empty) -->
	{ map__init(Map) }.
code_info__produce_resume_vars([V | Vs], Map, Code) -->
	code_info__produce_resume_vars(Vs, Map0, Code0),
	code_info__produce_variable_in_reg_or_stack(V, Code1, Rval),
	{ set__singleton_set(Rvals, Rval) },
	{ map__set(Map0, V, Rvals, Map) },
	{ Code = tree(Code0, Code1) }.

:- pred code_info__tweak_stacklist(assoc_list(var, lval),
	assoc_list(var, set(rval))).
:- mode code_info__tweak_stacklist(in, out) is det.

code_info__tweak_stacklist([], []).
code_info__tweak_stacklist([V - L | Rest0], [V - Rs | Rest]) :-
	set__singleton_set(Rs, lval(L)),
	code_info__tweak_stacklist(Rest0, Rest).

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

% :- pred code_info__modify_failure_cont(code_tree, code_info, code_info).
% :- mode code_info__modify_failure_cont(out, in, out) is det.
% 
% code_info__modify_failure_cont(ModifyCode) -->
% 	code_info__top_failure_cont(FailureCont),
% 	{ FailureCont = failure_cont(OldCont, MaybeRedo0, FailureMap) },
% 	code_info__generate_failure_cont(FailureCont, FailureCode),
% 	code_info__pop_failure_cont,
% 	code_info__get_next_label(NewRegCont),
% 	code_info__get_next_label(NewStackCont),
% 	(
% 		{ OldCont = unknown ; OldCont = known(yes) }
% 	->
% 		{ NewCont = known(yes) },
% 		( { MaybeRedo0 = yes(_OldRedo) } ->
% 			code_info__get_next_label(NewRedoCont),
% 			{ MaybeRedo = yes(NewRedoCont) }
% 		;
% 			{ NewRedoCont = NewStackCont },
% 			{ MaybeRedo = no }
% 		),
% 		{ ResetCode = node([
% 			assign(redoip(lval(maxfr)),
% 				const(code_addr_const(label(NewRedoCont)))) -
% 				"modify failure cont"
% 		]) }
% 	;
% 		{ error("code_info__modify_failure_cont: semidet context") }
% 		% { NewCont = known(no) },
% 		% { ResetCode = empty },
% 		% { MaybeRedo = no }
% 	),
% 	(
% 		{ FailureMap = [RegMap - _RegCont, StackMap - _StackCont] }
% 	->
% 		code_info__push_failure_cont(failure_cont(NewCont, MaybeRedo,
% 			[RegMap - label(NewRegCont),
% 			StackMap - label(NewStackCont)]))
% 	;
% 		{ error("code_info__modify_failure_cont: bad failure map.") }
% 	),
% 	{ ModifyCode = tree(FailureCode, ResetCode) }.

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

code_info__restore_failure_cont(Code) -->
	code_info__top_failure_cont(CurFailureCont),
	{ CurFailureCont = failure_cont(CurContInfo, _FailureMap) },
	code_info__generate_failure_cont(CurFailureCont, FailureCode),
	code_info__pop_failure_cont,
		% Fixup the redoip of the top frame if necessary
	(
		{ CurContInfo = semidet },
		{ ResetCode = empty }
	;
		{ CurContInfo = nondet(_, _) },
		code_info__top_failure_cont(EnclosingFailureCont),
		{ EnclosingFailureCont = failure_cont(EnclosingContInfo, _) },
		{
			EnclosingContInfo = semidet,
			ResetCode = empty
		;
			EnclosingContInfo = nondet(unknown, _),
			ResetCode = node([
				assign(redoip(lval(maxfr)),
					const(code_addr_const(do_fail))) -
					"restore failure cont"
			])
		;
			EnclosingContInfo = nondet(known, _),
			code_info__find_first_resume_label(
				EnclosingFailureCont, RedoAddress),
			ResetCode = node([
				assign(redoip(lval(maxfr)),
					const(code_addr_const(RedoAddress)))
					- "restore known failure cont"
			])
		}
	),
	{ Code = tree(FailureCode, ResetCode) }.

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

	% In establishing this resumption point, we may have pushed
	% a temporary frame onto the nondet stack. If we have done so,
	% we will have recorded this fact by setting the second argument
	% of the top failure continuation to yes, with the argument of
	% the yes giving the name of the label whose address was put
	% into the redoip slot of that frame.
	%
	% When control arrives at that label, curfr will point to the
	% temporary frame. However, the variables needed by the code
	% at the resumption point are in the main nondet frame of the
	% procedure. Since this was the current frame when we created
	% the temporary frame, we can find it by following the succfr
	% link in the temporary frame.
	%
	% The code we generate in general is
	%
	% label(RedoLabel)
	% <reset curfr>
	% label(StackLabel)
	% <assume variables are where StackMap says they are>
	% <copy variables to their locations according to OrigMap>
	% label(OrigLabel)
	% <assume variables are where OrigMap says they are>
	%
	% If, in establishing this resumption point, we did not create
	% a temporary frame, then curfr will be OK when code to the right
	% does a fail(), and hence the first label and the resetting of
	% the curfr register can be omitted.
	%
	% Failures at different points may cause control to arrive at
	% the resumption point via any one of these each labels.
	% The last line above is necessary since it may arrive at OrigLabel
	% without going through StackLabel first.
	%
	% The first two lines above are generated in this predicate;
	% the others are generated in code_info__generate_resume_setup.
	% It may not generate some of these other lines if it knows that
	% they won't be needed.

:- pred code_info__generate_failure_cont(failure_cont, code_tree,
	code_info, code_info).
:- mode code_info__generate_failure_cont(in, out, in, out) is det.

code_info__generate_failure_cont(FailureCont, Code) -->
	{ FailureCont = failure_cont(ContInfo, ResumeMap) },

		% Did we create a temp nondet frame for this continuation?
		% If not, then curfr will be right when we arrive here.
		% If yes, it will be wrong, pointing to the temp frame,
		% so we must restore curfr before continuing.
	{
		ContInfo = nondet(_, MaybeRedoLabel),
		MaybeRedoLabel = yes(RedoLabel)
	->
		FixCurFrCode = node([
			label(RedoLabel) -
				"redo entry point",
			assign(curfr, lval(succfr(lval(maxfr)))) -
				"restore curfr"
		]),
		(
			( ResumeMap = orig_only(_, _)
			; ResumeMap = orig_and_stack(_, _, _, _)
			)
		->
			error("redo entry before an orig resume point")
		;
			true
		)
	;
		FixCurFrCode = empty
	},
	code_info__generate_resume_setup(ResumeMap, ResumeCode),
	{ Code = tree(FixCurFrCode, ResumeCode) }.

:- pred code_info__generate_resume_setup(resume_maps, code_tree,
	code_info, code_info).
:- mode code_info__generate_resume_setup(in, out, in, out) is det.

code_info__generate_resume_setup(ResumeMaps, Code) -->
	(
		{ ResumeMaps = orig_only(Map1, Addr1) },
		{ extract_label_from_code_addr(Addr1, Label1) },
		{ Code = node([
			label(Label1) -
				"orig only failure continuation"
		]) },
		code_info__set_var_locations(Map1)
	;
		{ ResumeMaps = stack_only(Map1, Addr1) },
		{ extract_label_from_code_addr(Addr1, Label1) },
		{ Code = node([
			label(Label1) -
				"stack only failure continuation"
		]) },
		code_info__set_var_locations(Map1)
	;
		{ ResumeMaps = stack_and_orig(Map1, Addr1, Map2, Addr2) },
		{ extract_label_from_code_addr(Addr1, Label1) },
		{ extract_label_from_code_addr(Addr2, Label2) },
		{ Label1Code = node([
			label(Label1) -
				"stack failure continuation before orig"
		]) },
		code_info__set_var_locations(Map1),
		{ map__to_assoc_list(Map2, AssocList2) },
		code_info__place_resume_vars(AssocList2, PlaceCode),
		{ Label2Code = node([
			label(Label2) -
				"orig failure continuation after stack"
		]) },
		code_info__set_var_locations(Map2),
		{ Code = tree(Label1Code, tree(PlaceCode, Label2Code)) }
	;
		{ ResumeMaps = orig_and_stack(Map1, Addr1, Map2, Addr2) },
		{ extract_label_from_code_addr(Addr1, Label1) },
		{ extract_label_from_code_addr(Addr2, Label2) },
		{ Label1Code = node([
			label(Label1) -
				"orig failure continuation before stack"
		]) },
		code_info__set_var_locations(Map1),
		{ map__to_assoc_list(Map2, AssocList2) },
		code_info__place_resume_vars(AssocList2, PlaceCode),
		{ Label2Code = node([
			label(Label2) -
				"stack failure continuation after orig"
		]) },
		code_info__set_var_locations(Map2),
		{ Code = tree(Label1Code, tree(PlaceCode, Label2Code)) }
	).

:- pred extract_label_from_code_addr(code_addr, label).
:- mode extract_label_from_code_addr(in, out) is det.

extract_label_from_code_addr(CodeAddr, Label) :-
	( CodeAddr = label(Label0) ->
		Label = Label0
	;
		error("code_info__generate_resume_setup: non-label!")
	).

:- pred code_info__place_resume_vars(assoc_list(var, set(rval)), code_tree,
	code_info, code_info).
:- mode code_info__place_resume_vars(in, out, in, out) is det.

code_info__place_resume_vars([], empty) --> [].
code_info__place_resume_vars([Var - TargetSet | Rest], Code) -->
	{ set__to_sorted_list(TargetSet, Targets) },
	code_info__place_resume_var(Var, Targets, FirstCode),
	{ Code = tree(FirstCode, RestCode) },
	code_info__place_resume_vars(Rest, RestCode).

:- pred code_info__place_resume_var(var, list(rval), code_tree,
	code_info, code_info).
:- mode code_info__place_resume_var(in, in, out, in, out) is det.

code_info__place_resume_var(_Var, [], empty) --> [].
code_info__place_resume_var(Var, [Target | Targets], Code) -->
	( { Target = lval(TargetLval) } ->
		code_info__place_var(Var, TargetLval, FirstCode)
	;
		{ error("code_info__place_resume_var: not lval") }
	),
	{ Code = tree(FirstCode, RestCode) },
	code_info__place_resume_var(Var, Targets, RestCode).

	% Reset the code generator's database of what is where.
	% Remember that the variables in the map are available in their
	% associated rvals; forget about all other variables.

:- pred code_info__set_var_locations(map(var, set(rval)), code_info, code_info).
:- mode code_info__set_var_locations(in, in, out) is det.

code_info__set_var_locations(Map) -->
	{ map__to_assoc_list(Map, List0) },
	{ code_info__flatten_varlval_list(List0, List) },
	code_info__get_exprn_info(Exprn0),
	{ code_exprn__reinit_state(List, Exprn0, Exprn) },
	code_info__set_exprn_info(Exprn).

:- pred code_info__flatten_varlval_list(assoc_list(var, set(rval)),
						assoc_list(var, rval)).
:- mode code_info__flatten_varlval_list(in, out) is det.

code_info__flatten_varlval_list([], []).
code_info__flatten_varlval_list([V - Rvals | Rest0], All) :-
	code_info__flatten_varlval_list(Rest0, Rest),
	set__to_sorted_list(Rvals, RvalList),
	code_info__flatten_varlval_list_2(RvalList, V, Rest1),
	list__append(Rest1, Rest, All).

:- pred code_info__flatten_varlval_list_2(list(rval), var,
	assoc_list(var, rval)).
:- mode code_info__flatten_varlval_list_2(in, in, out) is det.

code_info__flatten_varlval_list_2([], _V, []).
code_info__flatten_varlval_list_2([R | Rs], V, [V - R | Rest]) :-
	code_info__flatten_varlval_list_2(Rs, V, Rest).

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

code_info__failure_is_direct_branch(CodeAddr) -->
	code_info__top_failure_cont(FailureCont),
	{ FailureCont = failure_cont(ContInfo, FailureMap) },
	{ code_info__fail_cont_is_known(ContInfo) },
	code_info__pick_matching_resume_addr(FailureMap, CodeAddr).

code_info__generate_failure(Code) -->
	code_info__top_failure_cont(FailureCont),
	{ FailureCont = failure_cont(ContInfo, FailureMap) },
	(
		{ code_info__fail_cont_is_known(ContInfo) }
	->
		(
			code_info__pick_matching_resume_addr(FailureMap,
				FailureAddress0)
		->
			{ FailureAddress = FailureAddress0 },
			{ PlaceCode = empty }
		;
			{ code_info__pick_first_resume_point(FailureMap,
				Map, FailureAddress) },
			{ map__to_assoc_list(Map, AssocList) },
			code_info__grab_code_info(CodeInfo),
			code_info__place_vars(AssocList, PlaceCode),
			code_info__slap_code_info(CodeInfo)
		),
		{ BranchCode = node([goto(FailureAddress) - "fail"]) },
		{ Code = tree(PlaceCode, BranchCode) }
	;
		{ Code = node([goto(do_redo) - "fail"]) }
	).

code_info__fail_if_rval_is_false(Rval0, Code) -->
	code_info__top_failure_cont(FailureCont),
	{ FailureCont = failure_cont(ContInfo, FailureMap) },
	(
		{ code_info__fail_cont_is_known(ContInfo) }
	->
		(
			code_info__pick_matching_resume_addr(FailureMap,
				FailureAddress0)
		->
				% We branch away if the test *fails*
			{ code_util__neg_rval(Rval0, Rval) },
			{ Code = node([
				if_val(Rval, FailureAddress0) -
					"Test for failure"
			]) }
		;
			{ code_info__pick_first_resume_point(FailureMap,
				Map, FailureAddress) },
			{ map__to_assoc_list(Map, AssocList) },
			code_info__get_next_label(SuccessLabel),
			code_info__grab_code_info(CodeInfo),
			code_info__place_vars(AssocList, PlaceCode),
			code_info__slap_code_info(CodeInfo),
			{ SuccessAddress = label(SuccessLabel) },
				% We branch away if the test *fails*,
				% therefore we branch around the code
				% that moves variables to their failure
				% locations and branches away
				% if the test succeeds
			{ TestCode = node([
				if_val(Rval0, SuccessAddress) -
					"Test for failure"
			]) },
			{ TailCode = node([
				goto(FailureAddress) -
					"Goto failure",
				label(SuccessLabel) -
					"Success continuation"
			]) },
			{ Code = tree(TestCode, tree(PlaceCode, TailCode)) }
		)
	;
		{ FailureAddress = do_redo },
			% We branch away if the test *fails*
		{ code_util__neg_rval(Rval0, Rval) },
		{ Code = node([
			if_val(Rval, FailureAddress) -
				"Test for failure"
		]) }
	).

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

	% See whether the current locations of variables match the locations
	% associated with any of the options in the given failure map.
	% If yes, return the code_addr of that option.

:- pred code_info__pick_matching_resume_addr(resume_maps, code_addr,
	code_info, code_info).
:- mode code_info__pick_matching_resume_addr(in, out, in, out) is semidet.

code_info__pick_matching_resume_addr(ResumeMaps, Addr) -->
	code_info__variable_locations(Locations),
	{
		ResumeMaps = orig_only(Map1, Addr1),
		( code_info__match_resume_loc(Map1, Locations) ->
			Addr = Addr1
		;
			fail
		)
	;
		ResumeMaps = stack_only(Map1, Addr1),
		( code_info__match_resume_loc(Map1, Locations) ->
			Addr = Addr1
		;
			fail
		)
	;
		ResumeMaps = orig_and_stack(Map1, Addr1, Map2, Addr2),
		( code_info__match_resume_loc(Map1, Locations) ->
			Addr = Addr1
		; code_info__match_resume_loc(Map2, Locations) ->
			Addr = Addr2
		;
			fail
		)
	;
		ResumeMaps = stack_and_orig(Map1, Addr1, Map2, Addr2),
		( code_info__match_resume_loc(Map1, Locations) ->
			Addr = Addr1
		; code_info__match_resume_loc(Map2, Locations) ->
			Addr = Addr2
		;
			fail
		)
	}.

:- pred code_info__match_resume_loc(resume_map, resume_map).
:- mode code_info__match_resume_loc(in, in) is semidet.

code_info__match_resume_loc(Map, Locations0) :-
	map__keys(Map, KeyList),
	set__list_to_set(KeyList, Keys),
	map__select(Locations0, Keys, Locations),
	map__to_assoc_list(Locations, List),
	\+ (
		list__member(Thingy, List),
		\+ (
			Thingy = Var - Actual,
			map__search(Map, Var, Rvals),
			set__subset(Rvals, Actual)
		)
	).

	% Find the first label that will be generated for the
	% given failure continuation based on the scheme used by
	% code_info__generate_failure_cont.

:- pred code_info__find_first_resume_label(failure_cont, code_addr).
:- mode code_info__find_first_resume_label(in, out) is det.

code_info__find_first_resume_label(FailureCont, Address) :-
	FailureCont = failure_cont(ContInfo, FailMap),
	(
		ContInfo = nondet(_, MaybeRedoLabel),
		MaybeRedoLabel = yes(RedoLabel)
	->
		Address = label(RedoLabel)
	;
		code_info__pick_first_resume_point(FailMap, _, Address)
	).

:- pred code_info__pick_first_resume_point(resume_maps, resume_map, code_addr).
:- mode code_info__pick_first_resume_point(in, out, out) is det.

code_info__pick_first_resume_point(orig_only(Map, Addr), Map, Addr).
code_info__pick_first_resume_point(stack_only(Map, Addr), Map, Addr).
code_info__pick_first_resume_point(orig_and_stack(Map, Addr, _, _), Map, Addr).
code_info__pick_first_resume_point(stack_and_orig(Map, Addr, _, _), Map, Addr).

:- pred code_info__pick_last_resume_point(resume_maps, resume_map, code_addr).
:- mode code_info__pick_last_resume_point(in, out, out) is det.

code_info__pick_last_resume_point(orig_only(Map, Addr), Map, Addr).
code_info__pick_last_resume_point(stack_only(Map, Addr), Map, Addr).
code_info__pick_last_resume_point(orig_and_stack( _, _, Map, Addr), Map, Addr).
code_info__pick_last_resume_point(stack_and_orig( _, _, Map, Addr), Map, Addr).

:- pred code_info__pick_stack_resume_point(resume_maps, resume_map, code_addr).
:- mode code_info__pick_stack_resume_point(in, out, out) is det.

code_info__pick_stack_resume_point(orig_only(_, _), _, _) :-
	error("no stack resume point").
code_info__pick_stack_resume_point(stack_only(Map, Addr), Map, Addr).
code_info__pick_stack_resume_point(orig_and_stack(_, _, Map, Addr), Map, Addr).
code_info__pick_stack_resume_point(stack_and_orig(Map, Addr, _, _), Map, Addr).

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

code_info__unset_failure_cont(Code) -->
	code_info__flush_resume_vars_to_stack(Code),
	code_info__top_failure_cont(FailureCont0),
	{ FailureCont0 = failure_cont(ContInfo0, FailureMap) },
	code_info__pop_failure_cont,
	{
		ContInfo0 = semidet,
		error("unset of semidet failure cont")
	;
		ContInfo0 = nondet(_, MaybeRedoLabel),
		ContInfo = nondet(unknown, MaybeRedoLabel)
	},
	{ FailureCont = failure_cont(ContInfo, FailureMap) },
	code_info__push_failure_cont(FailureCont).

code_info__flush_resume_vars_to_stack(Code) -->
	code_info__top_failure_cont(FailureCont0),
	{ FailureCont0 = failure_cont(_, FailureMap) },
	{ code_info__pick_stack_resume_point(FailureMap, StackMap, _) },
	{ map__to_assoc_list(StackMap, StackLocs) },
	code_info__place_resume_vars(StackLocs, Code).

code_info__may_use_nondet_tailcall(MayTailCall) -->
	code_info__top_failure_cont(FailureCont),
	{ FailureCont = failure_cont(ContInfo, FailureMap) },
	(
		{ code_info__fail_cont_is_known(ContInfo) },
		{ FailureMap = stack_only(_, do_fail) }
	->
		{ MayTailCall = yes }
	;
		{ MayTailCall = no }
	).

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

code_info__do_soft_cut(TheFrame, Code, ContCode) -->
	code_info__top_failure_cont(FailureCont),
	{ FailureCont = failure_cont(ContInfo, _) },
	(
		{ code_info__fail_cont_is_known(ContInfo) }
	->
		{ code_info__find_first_resume_label(FailureCont, Address) }
	;
			% If the newly uncovered cont is unknown then
			% we must have created a new frame before the
			% condition which we no longer need, so we
			% set its redoip to do_fail.
		{ Address = do_fail }
	),
	code_info__get_globals(Globals),
	{ globals__lookup_bool_option(Globals, use_trail, UseTrail) },
	( { UseTrail = yes } ->
		code_info__get_next_label(ContLabel),
		{ ContAddress = label(ContLabel) },
		{ ContCode = node([
			label(ContLabel) - "soft cut failure cont entry point",
			discard_ticket - "pop ticket stack",
			goto(Address) - "branch to prev failure continuation"
		]) }
	;
		{ ContAddress = Address },
		{ ContCode = empty }
	),
	{ Code = node([
		assign(redoip(lval(TheFrame)),
			const(code_addr_const(ContAddress)))
		- "prune away the `else' case of the if-then-else"
	]) }.

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

code_info__generate_semi_pre_commit(RedoLabel, Slots, PreCommit) -->
	code_info__generate_pre_commit_saves(Slots, SaveCode),
	code_info__get_next_label(ResumeLabel),
	code_info__top_failure_cont(FailureCont0),
	{ FailureCont0 = failure_cont(_, FailureMap0) },
	{ code_info__pick_stack_resume_point(FailureMap0, StackMap, _) },
	{ FailureCont = failure_cont(nondet(known, no),
		stack_only(StackMap, label(ResumeLabel))) },
	code_info__push_failure_cont(FailureCont),
	code_info__get_next_label(RedoLabel),
	{ HijackCode = node([
		assign(redoip(lval(maxfr)),
			const(code_addr_const(label(RedoLabel)))) -
			"Hijack the failure cont"
	]) },
	{ PreCommit = tree(SaveCode, HijackCode) }.

code_info__generate_semi_commit(RedoLabel, Slots, Commit) -->
	code_info__get_next_label(SuccLabel),
	{ GotoSuccLabel = node([
		goto(label(SuccLabel)) - "Jump to success continuation"
	]) },
	{ SuccLabelCode = node([
		label(SuccLabel) - "Success continuation"
	]) },
	{ RedoLabelCode = node([
		label(RedoLabel) - "Failure (redo) continuation"
	]) },

	code_info__grab_code_info(CodeInfo0),
	code_info__top_failure_cont(FailureCont),
	{ FailureCont = failure_cont(_, FailureMaps) },
	code_info__generate_resume_setup(FailureMaps, FailureContCode),
	code_info__pop_failure_cont,
	code_info__generate_failure(Fail),
	code_info__slap_code_info(CodeInfo0),
	code_info__pop_failure_cont,

	code_info__undo_pre_commit_saves(Slots, RestoreMaxfr, RestoreRedoip,
		RestoreCurfr, SuccPopCode, FailPopCode),

	{ SuccessCode =
		tree(RestoreMaxfr,
		tree(RestoreRedoip,
		tree(RestoreCurfr,
		     SuccPopCode)))
	},
	{ FailCode =
		tree(RedoLabelCode,
		tree(RestoreCurfr,
		tree(FailureContCode,
		tree(RestoreRedoip,
		tree(FailPopCode,
		     Fail)))))
	},
	{ Commit =
		tree(SuccessCode,
		tree(GotoSuccLabel,
		tree(FailCode,
		     SuccLabelCode)))
	}.

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

code_info__generate_det_pre_commit(Slots, PreCommit) -->
	code_info__generate_pre_commit_saves(Slots, PreCommit),
	% Since the code we are cutting is model_non, it will call
	% unset_failure_cont. If the current top entry on the failure stack
	% at the time is semidet, this would cause unset_failure_cont to abort.
	% We therefore push a dummy nondet failure continuation onto the
	% failure stack. Since the code we are cutting across is multi,
	% the failure continuation will never actually be used.
	code_info__top_failure_cont(FailureCont0),
	{ FailureCont0 = failure_cont(_, FailureMap) },
	{ code_info__pick_stack_resume_point(FailureMap, StackMap, _) },
	{ FailureCont = failure_cont(nondet(known, no),
		stack_only(StackMap, do_fail)) },
	code_info__push_failure_cont(FailureCont).

code_info__generate_det_commit(Slots, Commit) -->
	% Remove the dummy failure continuation pushed by det_pre_commit.
	code_info__pop_failure_cont,
	code_info__undo_pre_commit_saves(Slots, RestoreMaxfr, RestoreRedoip,
		RestoreCurfr, SuccPopCode, _FailPopCode),
	{ Commit = tree(RestoreMaxfr,
		   tree(RestoreRedoip,
		   tree(RestoreCurfr,
		        SuccPopCode)))
	}.

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

:- pred code_info__generate_pre_commit_saves(commit_slots, code_tree,
	code_info, code_info).
:- mode code_info__generate_pre_commit_saves(out, out, in, out) is det.

code_info__generate_pre_commit_saves(Slots, Code) -->
	code_info__get_globals(Globals),
	{ globals__lookup_bool_option(Globals, use_trail, UseTrail) },
	( { UseTrail = yes } ->
		{ NumSlots = 5 },
		{ SaveMessage =
	"push space for curfr, maxfr, redoip, ticket_counter and trail_ptr" }
	;
		{ NumSlots = 3 },
		{ SaveMessage = "push space for curfr, maxfr, and redoip" }
	),
	code_info__get_proc_model(CodeModel),
	( { CodeModel = model_non } ->
		% the pushes and pops on the det stack below will cause
		% problems for accurate garbage collection. Hence we
		% make sure the commit vals are made live, so gc
		% can figure out what is going on later.
		code_info__get_module_info(ModuleInfo),
		code_info__get_pred_id(PredId),
		{ predicate_module(ModuleInfo, PredId, ModuleName) },
		{ predicate_name(ModuleInfo, PredId, PredName) },
		{ prog_out__sym_name_to_string(ModuleName, ModuleNameString) },
		{ string__append_list(["commit in ",
			ModuleNameString, ":", PredName], Message) },
		{ PushCode = node([
			incr_sp(NumSlots, Message) - SaveMessage
		]) },
		{ CurfrSlot = stackvar(1) },
		{ MaxfrSlot = stackvar(2) },
		{ RedoipSlot = stackvar(3) },
		( { UseTrail = yes } ->
			{ TicketCounterSlot = stackvar(4) },
			{ TrailPtrSlot = stackvar(5) },
			{ MaybeTrailSlots = yes(TicketCounterSlot -
						TrailPtrSlot) }
		;
			{ MaybeTrailSlots = no }
		),
		{ Slots = commit_slots(CurfrSlot, MaxfrSlot, RedoipSlot,
			MaybeTrailSlots) },
		code_info__add_commit_triple
	;
		{ PushCode = empty },
		code_info__acquire_temp_slot(lval(curfr), CurfrSlot),
		code_info__acquire_temp_slot(lval(maxfr), MaxfrSlot),
		code_info__acquire_temp_slot(lval(redoip(lval(maxfr))),
			RedoipSlot),
		( { UseTrail = yes } ->
			code_info__acquire_temp_slot(ticket_counter,
						TicketCounterSlot),
			code_info__acquire_temp_slot(ticket, TrailPtrSlot),
			{ MaybeTrailSlots = yes(TicketCounterSlot -
						TrailPtrSlot) }
		;
			{ MaybeTrailSlots = no }
		),
		{ Slots = commit_slots(CurfrSlot, MaxfrSlot, RedoipSlot,
			MaybeTrailSlots) }
	),
	{ SaveCode = node([
		assign(CurfrSlot, lval(curfr)) -
				"Save current nondet frame pointer",
		assign(MaxfrSlot, lval(maxfr)) -
				"Save top of nondet stack",
		assign(RedoipSlot, lval(redoip(lval(maxfr)))) -
				"Save the top redoip"
	]) },
	{ MaybeTrailSlots = yes(TheTicketCounterSlot - TheTrailPtrSlot) ->
		MaybeSaveTrailCode = node([
			mark_ticket_stack(TheTicketCounterSlot) -
				"Save the ticket counter",
			store_ticket(TheTrailPtrSlot) -
				"Save the trail pointer"
		])
	;
		MaybeSaveTrailCode = empty
	},
	{ Code = tree(PushCode, tree(SaveCode, MaybeSaveTrailCode)) }.

:- pred code_info__undo_pre_commit_saves(commit_slots, code_tree, code_tree,
	code_tree, code_tree, code_tree, code_info, code_info).
:- mode code_info__undo_pre_commit_saves(in, out, out, out, out, out, in, out)
	is det.

code_info__undo_pre_commit_saves(Slots, RestoreMaxfr, RestoreRedoip,
		RestoreCurfr, SuccPopCode, FailPopCode) -->
	{ Slots = commit_slots(CurfrSlot, MaxfrSlot, RedoipSlot,
		MaybeTrailSlots) },
	{ RestoreMaxfr = node([
		assign(maxfr, lval(MaxfrSlot)) -
			"Prune away unwanted choice-points"
	]) },
	{ RestoreRedoip = node([
		assign(redoip(lval(maxfr)), lval(RedoipSlot)) -
			"Restore the top redoip"
	]) },
	{ RestoreCurfr = node([
		assign(curfr, lval(CurfrSlot)) -
			"Restore nondet frame pointer"
	]) },
	code_info__get_proc_model(CodeModel),
	( { CodeModel = model_non } ->
		code_info__rem_commit_triple,
		( { MaybeTrailSlots = yes(TicketCounterSlot - TrailPtrSlot) } ->
			{ CommitTrail = node([
				reset_ticket(lval(TrailPtrSlot), commit) -
				"discard trail entries and restore trail ptr"
			]) },
			{ RestoreTrail = node([
				reset_ticket(lval(TrailPtrSlot), undo) -
				"apply trail entries and restore trail ptr"
			]) },
			{ RestoreTicketCounter = node([
				discard_tickets_to(lval(TicketCounterSlot)) -
				"restore the ticket counter"
			]) },
			{ NumSlots = 5 },
			{ PopMessage =
		     "pop curfr, maxfr, redoip, ticket_counter and trail_ptr" }
		;
			{ CommitTrail = empty },
			{ RestoreTrail = empty },
			{ RestoreTicketCounter = empty },
			{ NumSlots = 3 },
			{ PopMessage = "pop curfr, maxfr, and redoip" }
		),
		{ MainPopCode = node([
			decr_sp(NumSlots) - PopMessage
		]) }
	;
		code_info__release_temp_slot(CurfrSlot),
		code_info__release_temp_slot(MaxfrSlot),
		code_info__release_temp_slot(RedoipSlot),
		( { MaybeTrailSlots = yes(TicketCounterSlot - TrailPtrSlot) } ->
			{ CommitTrail = node([
				reset_ticket(lval(TrailPtrSlot), commit) -
				"discard trail entries and restore trail ptr"
			]) },
			{ RestoreTrail = node([
				reset_ticket(lval(TrailPtrSlot), undo) -
				"apply trail entries and restore trail ptr"
			]) },
			{ RestoreTicketCounter = node([
				discard_tickets_to(lval(TicketCounterSlot)) -
				"restore the ticket counter"
			]) },
			code_info__release_temp_slot(TicketCounterSlot),
			code_info__release_temp_slot(TrailPtrSlot)
		;
			{ CommitTrail = empty },
			{ RestoreTrail = empty },
			{ RestoreTicketCounter = empty }
		),
		{ MainPopCode = empty }
	),
	{ SuccPopCode =
		tree(CommitTrail,
		tree(RestoreTicketCounter,
		     MainPopCode)) },
	{ FailPopCode =
		tree(RestoreTrail,
		tree(RestoreTicketCounter,
		     MainPopCode)) }.

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

	% Submodule to deal with liveness issues.

:- interface.

:- pred code_info__get_known_variables(list(var), code_info, code_info).
:- mode code_info__get_known_variables(out, in, out) is det.

:- pred code_info__variable_is_forward_live(var, code_info, code_info).
:- mode code_info__variable_is_forward_live(in, in, out) is semidet.

:- pred code_info__make_vars_forward_dead(set(var), code_info, code_info).
:- mode code_info__make_vars_forward_dead(in, in, out) is det.

:- pred code_info__pickup_zombies(set(var), code_info, code_info).
:- mode code_info__pickup_zombies(out, in, out) is det.

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

:- implementation.

:- pred code_info__add_forward_live_vars(set(var), code_info, code_info).
:- mode code_info__add_forward_live_vars(in, in, out) is det.

:- pred code_info__rem_forward_live_vars(set(var), code_info, code_info).
:- mode code_info__rem_forward_live_vars(in, in, out) is det.

	% Make these variables appear magically live.
	% We don't care where they are put.

:- pred code_info__make_vars_forward_live(set(var), code_info, code_info).
:- mode code_info__make_vars_forward_live(in, in, out) is det.

code_info__get_known_variables(VarList) -->
	code_info__get_forward_live_vars(ForwardLiveVars),
	code_info__current_resume_point_vars(ResumeVars),
	{ set__union(ForwardLiveVars, ResumeVars, Vars) },
	{ set__to_sorted_list(Vars, VarList) }.

code_info__variable_is_forward_live(Var) -->
	code_info__get_forward_live_vars(Liveness),
	{ set__member(Var, Liveness) }.

code_info__add_forward_live_vars(Births) -->
	code_info__get_forward_live_vars(Liveness0),
	{ set__union(Liveness0, Births, Liveness) },
	code_info__set_forward_live_vars(Liveness).

code_info__rem_forward_live_vars(Deaths) -->
	code_info__get_forward_live_vars(Liveness0),
	{ set__difference(Liveness0, Deaths, Liveness) },
	code_info__set_forward_live_vars(Liveness).

code_info__make_vars_forward_live(Vars) -->
	code_info__get_stack_slots(StackSlots),
	code_info__get_exprn_info(Exprn0),
	{ set__to_sorted_list(Vars, VarList) },
	{ code_info__make_vars_forward_live_2(VarList, StackSlots, 1,
		Exprn0, Exprn) },
	code_info__set_exprn_info(Exprn).

:- pred code_info__make_vars_forward_live_2(list(var), stack_slots, int,
	exprn_info, exprn_info).
:- mode code_info__make_vars_forward_live_2(in, in, in, in, out) is det.

code_info__make_vars_forward_live_2([], _, _, Exprn, Exprn).
code_info__make_vars_forward_live_2([V | Vs], StackSlots, N0, Exprn0, Exprn) :-
	( map__search(StackSlots, V, Lval0) ->
		Lval = Lval0,
		N1 = N0
	;
		code_info__find_unused_reg(N0, Exprn0, N1),
		Lval = reg(r, N1)
	),
	code_exprn__maybe_set_var_location(V, Lval, Exprn0, Exprn1),
	code_info__make_vars_forward_live_2(Vs, StackSlots, N1, Exprn1, Exprn).

:- pred code_info__find_unused_reg(int, exprn_info, int).
:- mode code_info__find_unused_reg(in, in, out) is det.

code_info__find_unused_reg(N0, Exprn0, N) :-
	( code_exprn__lval_in_use(reg(r, N0), Exprn0, _) ->
		N1 is N0 + 1,
		code_info__find_unused_reg(N1, Exprn0, N)
	;
		N = N0
	).

code_info__make_vars_forward_dead(Vars0) -->
	code_info__current_resume_point_vars(ResumeVars),
	{ set__intersect(Vars0, ResumeVars, FlushVars) },
	code_info__get_zombies(Zombies0),
	{ set__union(Zombies0, FlushVars, Zombies) },
	code_info__set_zombies(Zombies),
	{ set__difference(Vars0, Zombies, Vars) },
	{ set__to_sorted_list(Vars, VarList) },
	code_info__make_vars_forward_dead_2(VarList).

:- pred code_info__make_vars_forward_dead_2(list(var), code_info, code_info).
:- mode code_info__make_vars_forward_dead_2(in, in, out) is det.

code_info__make_vars_forward_dead_2([]) --> [].
code_info__make_vars_forward_dead_2([V | Vs]) -->
	code_info__get_exprn_info(Exprn0),
	{ code_exprn__var_becomes_dead(V, Exprn0, Exprn) },
	code_info__set_exprn_info(Exprn),
	code_info__make_vars_forward_dead_2(Vs).

code_info__pickup_zombies(Zombies) -->
	code_info__get_zombies(Zombies),
	{ set__init(Empty) },
	code_info__set_zombies(Empty).

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

	% Submodule for handling the saving and restoration
	% of trail tickets, heap pointers, stack pointers etc.

:- interface.

:- pred code_info__save_hp(code_tree, lval, code_info, code_info).
:- mode code_info__save_hp(out, out, in, out) is det.

:- pred code_info__restore_hp(lval, code_tree, code_info, code_info).
:- mode code_info__restore_hp(in, out, in, out) is det.

:- pred code_info__restore_and_discard_hp(lval, code_tree,
	code_info, code_info).
:- mode code_info__restore_and_discard_hp(in, out, in, out) is det.

:- pred code_info__discard_hp(lval, code_info, code_info).
:- mode code_info__discard_hp(in, in, out) is det.

:- pred code_info__maybe_save_hp(bool, code_tree, maybe(lval),
	code_info, code_info).
:- mode code_info__maybe_save_hp(in, out, out, in, out) is det.

:- pred code_info__maybe_restore_hp(maybe(lval), code_tree,
	code_info, code_info).
:- mode code_info__maybe_restore_hp(in, out, in, out) is det.

:- pred code_info__maybe_restore_and_discard_hp(maybe(lval), code_tree,
	code_info, code_info).
:- mode code_info__maybe_restore_and_discard_hp(in, out, in, out) is det.

:- pred code_info__maybe_discard_hp(maybe(lval), code_info, code_info).
:- mode code_info__maybe_discard_hp(in, in, out) is det.

:- pred code_info__save_ticket(code_tree, lval, code_info, code_info).
:- mode code_info__save_ticket(out, out, in, out) is det.

:- pred code_info__reset_ticket(lval, reset_trail_reason, code_tree,
	code_info, code_info).
:- mode code_info__reset_ticket(in, in, out, in, out) is det.

:- pred code_info__reset_and_discard_ticket(lval, reset_trail_reason, code_tree,
	code_info, code_info).
:- mode code_info__reset_and_discard_ticket(in, in, out, in, out) is det.

:- pred code_info__discard_ticket(lval, code_tree, code_info, code_info).
:- mode code_info__discard_ticket(in, out, in, out) is det.

:- pred code_info__maybe_save_ticket(bool, code_tree, maybe(lval),
	code_info, code_info).
:- mode code_info__maybe_save_ticket(in, out, out, in, out) is det.

:- pred code_info__maybe_reset_ticket(maybe(lval), reset_trail_reason,
	code_tree, code_info, code_info).
:- mode code_info__maybe_reset_ticket(in, in, out, in, out) is det.

:- pred code_info__maybe_reset_and_discard_ticket(maybe(lval),
	reset_trail_reason, code_tree, code_info, code_info).
:- mode code_info__maybe_reset_and_discard_ticket(in, in, out, in, out) is det.

:- pred code_info__maybe_discard_ticket(maybe(lval), code_tree,
	code_info, code_info).
:- mode code_info__maybe_discard_ticket(in, out, in, out) is det.

:- pred code_info__save_maxfr(lval, code_tree, code_info, code_info).
:- mode code_info__save_maxfr(out, out, in, out) is det.

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

:- implementation.

code_info__save_hp(Code, HpSlot) -->
	code_info__acquire_temp_slot(lval(hp), HpSlot),
	{ Code = node([mark_hp(HpSlot) - "Save heap pointer"]) }.

code_info__restore_hp(HpSlot, Code) -->
	{ Code = node([restore_hp(lval(HpSlot)) - "Restore heap pointer"]) }.

code_info__discard_hp(HpSlot) -->
	code_info__release_temp_slot(HpSlot).

code_info__restore_and_discard_hp(HpSlot, Code) -->
	{ Code = node([restore_hp(lval(HpSlot)) - "Restore heap pointer"]) },
	code_info__discard_hp(HpSlot).

code_info__maybe_save_hp(Maybe, Code, MaybeHpSlot) -->
	( { Maybe = yes } ->
		code_info__save_hp(Code, HpSlot),
		{ MaybeHpSlot = yes(HpSlot) }
	;
		{ Code = empty },
		{ MaybeHpSlot = no }
	).

code_info__maybe_restore_hp(MaybeHpSlot, Code) -->
	( { MaybeHpSlot = yes(HpSlot) } ->
		code_info__restore_hp(HpSlot, Code)
	;
		{ Code = empty }
	).

code_info__maybe_restore_and_discard_hp(MaybeHpSlot, Code) -->
	( { MaybeHpSlot = yes(HpSlot) } ->
		code_info__restore_and_discard_hp(HpSlot, Code)
	;
		{ Code = empty }
	).

code_info__maybe_discard_hp(MaybeHpSlot) -->
	( { MaybeHpSlot = yes(HpSlot) } ->
		code_info__discard_hp(HpSlot)
	;
		[]
	).

code_info__save_ticket(Code, TicketSlot) -->
	code_info__acquire_temp_slot(ticket, TicketSlot),
	{ Code = node([store_ticket(TicketSlot) - "Save trail state"]) }.

code_info__reset_ticket(TicketSlot, Reason, Code) -->
	{ Code = node([reset_ticket(lval(TicketSlot), Reason) - "Reset trail"]) }.

code_info__reset_and_discard_ticket(TicketSlot, Reason, Code) -->
	code_info__release_temp_slot(TicketSlot),
	{ Code = node([
		reset_ticket(lval(TicketSlot), Reason) - "Restore trail",
		discard_ticket - "Pop ticket stack"
	]) }.

code_info__discard_ticket(TicketSlot, Code) -->
	code_info__release_temp_slot(TicketSlot),
	{ Code = node([discard_ticket - "Pop ticket stack"]) }.

code_info__maybe_save_ticket(Maybe, Code, MaybeTicketSlot) -->
	( { Maybe = yes } ->
		code_info__save_ticket(Code, TicketSlot),
		{ MaybeTicketSlot = yes(TicketSlot) }
	;
		{ Code = empty },
		{ MaybeTicketSlot = no }
	).

code_info__maybe_reset_ticket(MaybeTicketSlot, Reason, Code) -->
	( { MaybeTicketSlot = yes(TicketSlot) } ->
		code_info__reset_ticket(TicketSlot, Reason, Code)
	;
		{ Code = empty }
	).

code_info__maybe_reset_and_discard_ticket(MaybeTicketSlot, Reason, Code) -->
	( { MaybeTicketSlot = yes(TicketSlot) } ->
		code_info__reset_and_discard_ticket(TicketSlot, Reason, Code)
	;
		{ Code = empty }
	).

code_info__maybe_discard_ticket(MaybeTicketSlot, Code) -->
	( { MaybeTicketSlot = yes(TicketSlot) } ->
		code_info__discard_ticket(TicketSlot, Code)
	;
		{ Code = empty }
	).

code_info__save_maxfr(MaxfrSlot, Code) -->
	code_info__acquire_temp_slot(lval(maxfr), MaxfrSlot),
	{ Code = node([assign(MaxfrSlot, lval(maxfr)) - "Save maxfr"]) }.

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

	% Submodule to deal with code_exprn.

:- interface.

:- pred code_info__variable_locations(map(var, set(rval)),
	code_info, code_info).
:- mode code_info__variable_locations(out, in, out) is det.

:- pred code_info__set_var_location(var, lval, code_info, code_info).
:- mode code_info__set_var_location(in, in, in, out) is det.

:- pred code_info__cache_expression(var, rval, code_info, code_info).
:- mode code_info__cache_expression(in, in, in, out) is det.

:- pred code_info__place_var(var, lval, code_tree, code_info, code_info).
:- mode code_info__place_var(in, in, out, in, out) is det.

:- pred code_info__produce_variable(var, code_tree, rval, code_info, code_info).
:- mode code_info__produce_variable(in, out, out, in, out) is det.

:- pred code_info__produce_variable_in_reg(var, code_tree, rval,
	code_info, code_info).
:- mode code_info__produce_variable_in_reg(in, out, out, in, out) is det.

:- pred code_info__produce_variable_in_reg_or_stack(var, code_tree, rval,
	code_info, code_info).
:- mode code_info__produce_variable_in_reg_or_stack(in, out, out, in, out)
	is det.

:- pred code_info__materialize_vars_in_rval(rval, rval, code_tree, code_info,
	code_info).
:- mode code_info__materialize_vars_in_rval(in, out, out, in, out) is det.

:- pred code_info__lock_reg(lval, code_info, code_info).
:- mode code_info__lock_reg(in, in, out) is det.

:- pred code_info__unlock_reg(lval, code_info, code_info).
:- mode code_info__unlock_reg(in, in, out) is det.

:- pred code_info__acquire_reg_for_var(var, lval, code_info, code_info).
:- mode code_info__acquire_reg_for_var(in, out, in, out) is det.

:- pred code_info__acquire_reg(reg_type, lval, code_info, code_info).
:- mode code_info__acquire_reg(in, out, in, out) is det.

:- pred code_info__release_reg(lval, code_info, code_info).
:- mode code_info__release_reg(in, in, out) is det.

:- pred code_info__clear_r1(code_tree, code_info, code_info).
:- mode code_info__clear_r1(out, in, out) is det.

:- pred code_info__generate_branch_end(code_model, store_map, code_tree,
	code_info, code_info).
:- mode code_info__generate_branch_end(in, in, out, in, out) is det.

	% code_info__remake_with_store_map throws away the exprn_info data
	% structure, forgetting the current locations of all variables,
	% and rebuilds it from scratch based on the given store map.
	% The new exprn_info will know about only the variables present
	% in the store map, and will believe they are where the store map
	% says they are.

:- pred code_info__remake_with_store_map(store_map, code_info, code_info).
:- mode code_info__remake_with_store_map(in, in, out) is det.

:- type call_direction ---> caller ; callee.

	% Generate code to either setup the input arguments for a call
	% (i.e. in the caller), or to setup the output arguments in the
	% predicate epilog (i.e. in the callee).

:- pred code_info__setup_call(assoc_list(var, arg_info),
	call_direction, code_tree, code_info, code_info).
:- mode code_info__setup_call(in, in, out, in, out) is det.

:- pred code_info__clear_all_registers(code_info, code_info).
:- mode code_info__clear_all_registers(in, out) is det.

:- pred code_info__save_variable_on_stack(var, code_tree,
	code_info, code_info).
:- mode code_info__save_variable_on_stack(in, out, in, out) is det.

:- pred code_info__save_variables_on_stack(list(var), code_tree,
	code_info, code_info).
:- mode code_info__save_variables_on_stack(in, out, in, out) is det.

:- pred code_info__max_reg_in_use(int, code_info, code_info).
:- mode code_info__max_reg_in_use(out, in, out) is det.

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

:- implementation.

:- pred code_info__place_vars(assoc_list(var, set(rval)), code_tree,
	code_info, code_info).
:- mode code_info__place_vars(in, out, in, out) is det.

code_info__variable_locations(Locations) -->
	code_info__get_exprn_info(Exprn),
	{ code_exprn__get_varlocs(Exprn, Locations) }.

code_info__set_var_location(Var, Lval) -->
	code_info__get_exprn_info(Exprn0),
	{ code_exprn__set_var_location(Var, Lval, Exprn0, Exprn) },
	code_info__set_exprn_info(Exprn).

code_info__cache_expression(Var, Rval) -->
	code_info__get_exprn_info(Exprn0),
	{ code_exprn__cache_exprn(Var, Rval, Exprn0, Exprn) },
	code_info__set_exprn_info(Exprn).

code_info__place_var(Var, Lval, Code) -->
	code_info__get_exprn_info(Exprn0),
	{ code_exprn__place_var(Var, Lval, Code, Exprn0, Exprn) },
	code_info__set_exprn_info(Exprn).

code_info__place_vars([], empty) --> [].
code_info__place_vars([V - Rs | RestList], Code) -->
	(
		{ set__to_sorted_list(Rs, RList) },
		{ code_info__lval_in_rval_list(L, RList) }
	->
		code_info__place_var(V, L, ThisCode)
	;
		{ ThisCode = empty }
	),
	code_info__place_vars(RestList, RestCode),
	{ Code = tree(ThisCode, RestCode) }.

:- pred code_info__lval_in_rval_list(lval, list(rval)).
:- mode code_info__lval_in_rval_list(out, in) is semidet.

code_info__lval_in_rval_list(Lval, [Rval | Rvals]) :-
	( Rval = lval(Lval0) ->
		Lval = Lval0
	;
		code_info__lval_in_rval_list(Lval, Rvals)
	).

code_info__produce_variable(Var, Code, Rval) -->
	code_info__get_exprn_info(Exprn0),
	{ code_exprn__produce_var(Var, Rval, Code, Exprn0, Exprn) },
	code_info__set_exprn_info(Exprn).

code_info__produce_variable_in_reg(Var, Code, Rval) -->
	code_info__get_exprn_info(Exprn0),
	{ code_exprn__produce_var_in_reg(Var, Rval, Code, Exprn0, Exprn) },
	code_info__set_exprn_info(Exprn).

code_info__produce_variable_in_reg_or_stack(Var, Code, Rval) -->
	code_info__get_exprn_info(Exprn0),
	{ code_exprn__produce_var_in_reg_or_stack(Var, Rval, Code,
		Exprn0, Exprn) },
	code_info__set_exprn_info(Exprn).

code_info__materialize_vars_in_rval(Rval0, Rval, Code) -->
	code_info__get_exprn_info(Exprn0),
	{ code_exprn__materialize_vars_in_rval(Rval0, Rval, Code,
		Exprn0, Exprn) },
	code_info__set_exprn_info(Exprn).

code_info__lock_reg(Reg) -->
	code_info__get_exprn_info(Exprn0),
	{ code_exprn__lock_reg(Reg, Exprn0, Exprn) },
	code_info__set_exprn_info(Exprn).

code_info__unlock_reg(Reg) -->
	code_info__get_exprn_info(Exprn0),
	{ code_exprn__unlock_reg(Reg, Exprn0, Exprn) },
	code_info__set_exprn_info(Exprn).

code_info__acquire_reg_for_var(Var, Lval) -->
	code_info__get_exprn_info(Exprn0),
	code_info__get_follow_vars(Follow),
	(
		{ map__search(Follow, Var, PrefLval) },
		{ PrefLval = reg(PrefRegType, PrefRegNum) }
	->
		{ code_exprn__acquire_reg_prefer_given(PrefRegType, PrefRegNum,
			Lval, Exprn0, Exprn) }
	;
		{ code_exprn__acquire_reg(r, Lval, Exprn0, Exprn) }
	),
	code_info__set_exprn_info(Exprn).

code_info__acquire_reg(Type, Lval) -->
	code_info__get_exprn_info(Exprn0),
	{ code_exprn__acquire_reg(Type, Lval, Exprn0, Exprn) },
	code_info__set_exprn_info(Exprn).

code_info__release_reg(Lval) -->
	code_info__get_exprn_info(Exprn0),
	{ code_exprn__release_reg(Lval, Exprn0, Exprn) },
	code_info__set_exprn_info(Exprn).

code_info__clear_r1(Code) -->
	code_info__get_exprn_info(Exprn0),
	{ code_exprn__clear_r1(Code, Exprn0, Exprn) },
	code_info__set_exprn_info(Exprn).

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

code_info__generate_branch_end(CodeModel, StoreMap, Code) -->
	code_info__get_exprn_info(Exprn0),
	{ map__to_assoc_list(StoreMap, VarLocs) },
	{ code_exprn__place_vars(VarLocs, PlaceCode, Exprn0, Exprn) },
	code_info__set_exprn_info(Exprn),
	( { CodeModel = model_non } ->
		code_info__unset_failure_cont(FlushCode),
		{ Code = tree(PlaceCode, FlushCode) }
	;
		{ Code = PlaceCode }
	).

code_info__remake_with_store_map(StoreMap) -->
	{ map__to_assoc_list(StoreMap, VarLvals) },
	{ code_info__fixup_lvallist(VarLvals, VarRvals) },
	code_info__get_exprn_info(Exprn0),
	{ code_exprn__reinit_state(VarRvals, Exprn0, Exprn) },
	code_info__set_exprn_info(Exprn).

:- pred code_info__fixup_lvallist(assoc_list(var, lval), assoc_list(var, rval)).
:- mode code_info__fixup_lvallist(in, out) is det.

code_info__fixup_lvallist([], []).
code_info__fixup_lvallist([V - L | Ls], [V - lval(L) | Rs]) :-
	code_info__fixup_lvallist(Ls, Rs).

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

code_info__setup_call([], _Direction, empty) --> [].
code_info__setup_call([V - arg_info(Loc, Mode) | Rest], Direction, Code) -->
	(
		{
			Mode = top_in,
			Direction = caller
		;
			Mode = top_out,
			Direction = callee
		}
	->
		{ code_util__arg_loc_to_register(Loc, Reg) },
		code_info__get_exprn_info(Exprn0),
		{ code_exprn__place_var(V, Reg, Code0, Exprn0, Exprn1) },
			% We need to test that either the variable
			% is live OR it occurs in the remaining arguments
			% because of a bug in polymorphism.m which
			% causes some compiler generated code to violate
			% superhomogeneous form
		(
			code_info__variable_is_forward_live(V)
		->
			{ IsLive = yes }
		;
			{ IsLive = no }
		),
		{
			list__member(Vtmp - _, Rest),
			V = Vtmp
		->
			Occurs = yes
		;
			Occurs = no
		},
		(
				% We can't simply use a disj here
				% because of bugs in modes/det_analysis
			{ bool__or(Occurs, IsLive, yes) }
		->
			{ code_exprn__lock_reg(Reg, Exprn1, Exprn2) },
			code_info__set_exprn_info(Exprn2),
			code_info__setup_call(Rest, Direction, Code1),
			code_info__get_exprn_info(Exprn3),
			{ code_exprn__unlock_reg(Reg, Exprn3, Exprn) },
			code_info__set_exprn_info(Exprn),
			{ Code = tree(Code0, Code1) }
		;
			{ code_exprn__lock_reg(Reg, Exprn1, Exprn2) },
			code_info__set_exprn_info(Exprn2),
			{ set__singleton_set(Vset, V) },
			code_info__make_vars_forward_dead(Vset),
			code_info__setup_call(Rest, Direction, Code1),
			code_info__get_exprn_info(Exprn4),
			{ code_exprn__unlock_reg(Reg, Exprn4, Exprn) },
			code_info__set_exprn_info(Exprn),
			{ Code = tree(Code0, Code1) }
		)
	;
		code_info__setup_call(Rest, Direction, Code)
	).

	% XXX We could use the sanity checking mechanism...
code_info__clear_all_registers -->
	code_info__get_exprn_info(Exprn0),
	{ code_exprn__clobber_regs([], Exprn0, Exprn) },
	code_info__set_exprn_info(Exprn).

code_info__save_variable_on_stack(Var, Code) -->
	code_info__get_variable_slot(Var, Slot),
	code_info__get_exprn_info(Exprn0),
	{ code_exprn__place_var(Var, Slot, Code, Exprn0, Exprn) },
	code_info__set_exprn_info(Exprn).

code_info__save_variables_on_stack([], empty) --> [].
code_info__save_variables_on_stack([Var | Vars], Code) -->
	code_info__save_variable_on_stack(Var, FirstCode),
	code_info__save_variables_on_stack(Vars, RestCode),
	{ Code = tree(FirstCode, RestCode) }.

code_info__max_reg_in_use(Max) -->
	code_info__get_exprn_info(Exprn),
	{ code_exprn__max_reg_in_use(Exprn, Max) }.

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

	% Submodule for dealing with information for garbage collection
	% and value numbering.

:- interface.

:- pred code_info__generate_stack_livevals(set(var), set(lval),
	code_info, code_info).
:- mode code_info__generate_stack_livevals(in, out, in, out) is det.

:- pred code_info__generate_stack_livelvals(set(var), instmap, 
	list(liveinfo), code_info, code_info).
:- mode code_info__generate_stack_livelvals(in, in, out, in, out) is det.

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

:- implementation.

code_info__generate_stack_livevals(Args, LiveVals) -->
	code_info__get_known_variables(LiveVars),
	{ set__list_to_set(LiveVars, Vars0) },
	{ set__difference(Vars0, Args, Vars) },
	{ set__to_sorted_list(Vars, VarList) },
	{ set__init(LiveVals0) },
	code_info__generate_var_livevals(VarList, LiveVals0, LiveVals1),
	code_info__get_temps_in_use(TempsSet),
	{ map__to_assoc_list(TempsSet, Temps) },
	{ code_info__generate_temp_livevals(Temps, LiveVals1, LiveVals2) },
	code_info__get_commit_triple_count(Triples),
	{ code_info__generate_commit_livevals(Triples, LiveVals2, LiveVals) }.

:- pred code_info__generate_var_livevals(list(var), set(lval), set(lval),
	code_info, code_info).
:- mode code_info__generate_var_livevals(in, in, out, in, out) is det.

code_info__generate_var_livevals([], Vals, Vals) --> [].
code_info__generate_var_livevals([V | Vs], Vals0, Vals) -->
	code_info__get_variable_slot(V, Slot),
	{ set__insert(Vals0, Slot, Vals1) },
	code_info__generate_var_livevals(Vs, Vals1, Vals).

:- pred code_info__generate_temp_livevals(assoc_list(lval, slot_contents),
	set(lval), set(lval)).
:- mode code_info__generate_temp_livevals(in, in, out) is det.

code_info__generate_temp_livevals([], Vals, Vals).
code_info__generate_temp_livevals([Slot - _ | Slots], Vals0, Vals) :-
	set__insert(Vals0, Slot, Vals1),
	code_info__generate_temp_livevals(Slots, Vals1, Vals).

:- pred code_info__generate_commit_livevals(int, set(lval), set(lval)).
:- mode code_info__generate_commit_livevals(in, in, out) is det.

code_info__generate_commit_livevals(Triples0, Vals0, Vals) :-
	( Triples0 = 0 ->
		Vals = Vals0
	;
		CurfrSlot is (Triples0 - 1) * 3 + 1,
		MaxfrSlot is (Triples0 - 1) * 3 + 2,
		RedoipSlot is (Triples0 - 1) * 3 + 3,
		CurfrVar = stackvar(CurfrSlot),
		MaxfrVar = stackvar(MaxfrSlot),
		RedoipVar = stackvar(RedoipSlot),
		set__insert(Vals0, CurfrVar, Vals1),
		set__insert(Vals1, MaxfrVar, Vals2),
		set__insert(Vals2, RedoipVar, Vals3),
		Triples1 is Triples0 - 1,
		code_info__generate_commit_livevals(Triples1, Vals3, Vals)
	).

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

code_info__generate_stack_livelvals(Args, AfterCallInstMap, LiveVals) -->
	code_info__get_known_variables(LiveVars),
	{ set__list_to_set(LiveVars, Vars0) },
	{ set__difference(Vars0, Args, Vars) },
	{ set__to_sorted_list(Vars, VarList) },
	{ set__init(LiveVals0) },
	code_info__generate_var_livelvals(VarList, LiveVals0, LiveVals1),
	{ set__to_sorted_list(LiveVals1, LiveVals2) },
	code_info__get_globals(Globals),
	{ globals__get_gc_method(Globals, GC_Method) },
	code_info__livevals_to_livelvals(LiveVals2, GC_Method, 
		AfterCallInstMap, LiveVals3),
	code_info__get_temps_in_use(TempsSet),
	{ map__to_assoc_list(TempsSet, Temps) },
	{ code_info__generate_temp_livelvals(Temps, LiveVals3, LiveVals4) },
	code_info__get_commit_triple_count(Triples),
	{ code_info__generate_commit_livelvals(Triples, LiveVals4, LiveVals) }.

:- pred code_info__generate_var_livelvals(list(var),
	set(pair(lval, var)), set(pair(lval, var)), code_info, code_info).
:- mode code_info__generate_var_livelvals(in, in, out, in, out) is det.

code_info__generate_var_livelvals([], Vals, Vals) --> [].
code_info__generate_var_livelvals([V | Vs], Vals0, Vals) -->
	code_info__get_variable_slot(V, Slot),
	{ set__insert(Vals0, Slot - V, Vals1) },
	code_info__generate_var_livelvals(Vs, Vals1, Vals).

:- pred code_info__generate_temp_livelvals(assoc_list(lval, slot_contents),
	list(liveinfo), list(liveinfo)).
:- mode code_info__generate_temp_livelvals(in, in, out) is det.

code_info__generate_temp_livelvals([], LiveInfo, LiveInfo).
code_info__generate_temp_livelvals([Slot - StoredLval | Slots], LiveInfo0, 
		[live_lvalue(Slot, LiveValueType, "", []) | LiveInfo1]) :-
	code_info__get_live_value_type(StoredLval, LiveValueType),
	code_info__generate_temp_livelvals(Slots, LiveInfo0, LiveInfo1).

:- pred code_info__generate_commit_livelvals(int,
	list(liveinfo), list(liveinfo)).
:- mode code_info__generate_commit_livelvals(in, in, out) is det.

code_info__generate_commit_livelvals(Triples0, LiveInfo0, LiveInfo) :-
	( Triples0 = 0 ->
		LiveInfo = LiveInfo0
	;
		Triples1 is Triples0 - 1,
		code_info__generate_commit_livelvals(Triples1,
			LiveInfo0, LiveInfo1),
		CurfrSlot is (Triples0 - 1) * 3 + 1,
		MaxfrSlot is (Triples0 - 1) * 3 + 2,
		RedoipSlot is (Triples0 - 1) * 3 + 3,
		CurfrVar = stackvar(CurfrSlot),
		MaxfrVar = stackvar(MaxfrSlot),
		RedoipVar = stackvar(RedoipSlot),
		code_info__get_live_value_type(lval(curfr), CurfrValueType),
		code_info__get_live_value_type(lval(maxfr), MaxfrValueType),
		code_info__get_live_value_type(lval(redoip(lval(maxfr))),
			RedoipValueType),
		LiveInfo2 = [live_lvalue(CurfrVar, CurfrValueType, "", []) | 
				LiveInfo1],
		LiveInfo3 = [live_lvalue(MaxfrVar, MaxfrValueType, "", []) |
				LiveInfo2],
		LiveInfo  = [live_lvalue(RedoipVar, RedoipValueType, "", []) |
				LiveInfo3]
	).

:- pred code_info__livevals_to_livelvals(assoc_list(lval, var), gc_method,
	instmap, list(liveinfo), code_info, code_info).
:- mode code_info__livevals_to_livelvals(in, in, in, out, in, out) is det.

code_info__livevals_to_livelvals([], _GC_Method, _, []) --> [].
code_info__livevals_to_livelvals([Lval - Var | Ls], GC_Method, AfterCallInstMap,
		[LiveLval | Lives]) -->
	code_info__get_varset(VarSet),
	{ varset__lookup_name(VarSet, Var, Name) },
	(
		{ GC_Method = accurate }
	->
		{ instmap__lookup_var(AfterCallInstMap, Var, Inst) },

		code_info__variable_type(Var, Type),
		{ type_util__vars(Type, TypeVars) },
		code_info__find_type_infos(TypeVars, TypeParams),
		{ LiveLval = live_lvalue(Lval, var(Type, Inst), Name,
			TypeParams) }
	;
		{ LiveLval = live_lvalue(Lval, unwanted, Name, []) }
	),
	code_info__livevals_to_livelvals(Ls, GC_Method, AfterCallInstMap, 
		Lives).

:- pred code_info__get_live_value_type(slot_contents, live_value_type).
:- mode code_info__get_live_value_type(in, out) is det.

code_info__get_live_value_type(lval(succip), succip).
code_info__get_live_value_type(lval(hp), hp).
code_info__get_live_value_type(lval(maxfr), maxfr).
code_info__get_live_value_type(lval(curfr), curfr).
code_info__get_live_value_type(lval(succfr(_)), unwanted).
code_info__get_live_value_type(lval(prevfr(_)), unwanted).
code_info__get_live_value_type(lval(redoip(_)), unwanted).
code_info__get_live_value_type(lval(succip(_)), unwanted).
code_info__get_live_value_type(lval(sp), unwanted).
code_info__get_live_value_type(lval(lvar(_)), unwanted).
code_info__get_live_value_type(lval(field(_, _, _)), unwanted).
code_info__get_live_value_type(lval(temp(_, _)), unwanted).
code_info__get_live_value_type(lval(reg(_, _)), unwanted).
code_info__get_live_value_type(lval(stackvar(_)), unwanted).
code_info__get_live_value_type(lval(framevar(_)), unwanted).
code_info__get_live_value_type(lval(mem_ref(_)), unwanted).		% XXX
code_info__get_live_value_type(ticket, unwanted). % XXX we may need to
					% modify this, if the GC is going
					% to garbage-collect the trail.
code_info__get_live_value_type(ticket_counter, unwanted).
code_info__get_live_value_type(trace_data, unwanted).

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

	% Submodule for managing stack slots.

	% The det stack frame is organized as follows.
	%
	%		... unused ...
	%	sp --->	<first unused slot>
	%		<space for local var 1>
	%		... local vars ...
	%		<space for local var n>
	%		<space for temporary reg save 1>
	%		... temporary reg saves ...
	%		<space for temporary reg save n>
	%		<space for succip>
	%
	% The stack pointer points to the first free location at the
	% top of the stack.
	%
	% `code_info__num_stackslots' counts the number of slots reserved
	% for saving local variables. XXX
	%
	% `code_info__max_push_count' counts the number of slots reserved
	% for saving and restoring registers (hp, redoip, etc.)
	%
	% `code_info__succip_used' determines whether we need a slot to
	% hold the succip.
	%
	% The variable part of the nondet stack is organized in the same way
	% as the det stack (but the nondet stack also contains several other
	% fixed fields.)

:- interface.

	% Returns the total stackslot count, but not including space for
	% succip.
:- pred code_info__get_total_stackslot_count(int, code_info, code_info).
:- mode code_info__get_total_stackslot_count(out, in, out) is det.

:- pred code_info__get_trace_slot(lval, code_info, code_info).
:- mode code_info__get_trace_slot(out, in, out) is det.

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

:- implementation.

:- pred code_info__acquire_temp_slot(slot_contents, lval,
	code_info, code_info).
:- mode code_info__acquire_temp_slot(in, out, in, out) is det.

:- pred code_info__release_temp_slot(lval, code_info, code_info).
:- mode code_info__release_temp_slot(in, in, out) is det.

:- pred code_info__get_variable_slot(var, lval, code_info, code_info).
:- mode code_info__get_variable_slot(in, out, in, out) is det.

:- pred code_info__max_var_slot(stack_slots, int).
:- mode code_info__max_var_slot(in, out) is det.

:- pred code_info__stack_variable(int, lval, code_info, code_info).
:- mode code_info__stack_variable(in, out, in, out) is det.

code_info__get_trace_slot(StackVar) -->
	code_info__acquire_temp_slot(trace_data, StackVar).

code_info__acquire_temp_slot(Item, StackVar) -->
	code_info__get_avail_temp_slots(AvailSlots0),
	( { set__remove_least(AvailSlots0, StackVarPrime, AvailSlots) } ->
		{ StackVar = StackVarPrime },
		code_info__set_avail_temp_slots(AvailSlots)
	;
		code_info__get_var_slot_count(VarSlots),
		code_info__get_max_temp_slot_count(TempSlots0),
		{ TempSlots is TempSlots0 + 1 },
		{ Slot is VarSlots + TempSlots },
		code_info__stack_variable(Slot, StackVar),
		code_info__set_max_temp_slot_count(TempSlots)
	),
	code_info__get_temps_in_use(TempsInUse0),
	{ map__det_insert(TempsInUse0, StackVar, Item, TempsInUse) },
	code_info__set_temps_in_use(TempsInUse).

code_info__release_temp_slot(StackVar) -->
	code_info__get_avail_temp_slots(AvailSlots0),
	{ set__insert(AvailSlots0, StackVar, AvailSlots) },
	code_info__set_avail_temp_slots(AvailSlots),
	code_info__get_temps_in_use(TempsInUse0),
	{ map__delete(TempsInUse0, StackVar, TempsInUse) },
	code_info__set_temps_in_use(TempsInUse).

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

code_info__get_variable_slot(Var, Slot) -->
	code_info__get_stack_slots(StackSlots),
	( { map__search(StackSlots, Var, SlotPrime) } ->
		{ Slot = SlotPrime }
	;
		code_info__variable_to_string(Var, Name),
		{ term__var_to_int(Var, Num) },
		{ string__int_to_string(Num, NumStr) },
		{ string__append_list([
			"code_info__get_variable_slot: variable `",
			Name, "' (", NumStr, ") not found"], Str) },
		{ error(Str) }
	).

code_info__max_var_slot(StackSlots, SlotCount) :-
	map__values(StackSlots, StackSlotList),
	code_info__max_var_slot_2(StackSlotList, 0, SlotCount).

:- pred code_info__max_var_slot_2(list(lval), int, int).
:- mode code_info__max_var_slot_2(in, in, out) is det.

code_info__max_var_slot_2([], Max, Max).
code_info__max_var_slot_2([L | Ls], Max0, Max) :-
	( L = stackvar(N) ->
		int__max(N, Max0, Max1)
	; L = framevar(N) ->
		int__max(N, Max0, Max1)
	;
		Max1 = Max0
	),
	code_info__max_var_slot_2(Ls, Max1, Max).

code_info__get_total_stackslot_count(NumSlots) -->
	code_info__get_var_slot_count(SlotsForVars),
	code_info__get_max_temp_slot_count(SlotsForTemps),
	{ NumSlots is SlotsForVars + SlotsForTemps }.

code_info__stack_variable(Num, Lval) -->
	code_info__get_proc_model(CodeModel),
	( { CodeModel = model_non } ->
		{ Num1 is Num - 1 },		% framevars start at zero
		{ Lval = framevar(Num1) }
	;
		{ Lval = stackvar(Num) }	% stackvars start at one
	).

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