mercury/compiler/ml_code_gen.m

%-----------------------------------------------------------------------------%
% Copyright (C) 1999-2005 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: ml_code_gen.m
% Main author: fjh

% MLDS code generation -- convert from HLDS to MLDS.

% This module is an alternative to the original code generator.
% The original code generator compiles from HLDS to LLDS, generating
% very low-level code. This code generator instead compiles to MLDS,
% generating much higher-level code than the original code generator.

% One of the aims of the MLDS is to be able to generated human-readable
% code in languages like C or Java. This means that unlike the LLDS back-end,
% we do not want to rely on macros or conditional compilation. If the
% final code is going to depend on the setting of some compilation option,
% our philosophy is to reflect that change in the generated MLDS and C code
% where possible, rather than generating C code which calls macros that do
% different things in different grades. This is important both for
% readability of the generated code, and to make sure that we can easily
% adapt the MLDS code generator to target languages like Java that don't
% support macros or conditional compilation.

% A big challenge in generating MLDS code is handling nondeterminism.
% For nondeterministic procedures, we generate code using an explicit
% continuation passing style. Each nondeterministic procedures gets
% translated into a function which takes an extra parameter which is a
% function pointer that points to the success continuation. On success,
% the function calls its success continuation, and on failure it returns.

% To keep things easy, this pass generates code which may contain nested
% functions; if the target language doesn't support nested functions (or
% doesn't support them _efficiently_) then a later MLDS->MLDS simplification
% pass will convert it to a form that does not use nested functions.

% Note that when we take the address of a nested function, we only ever
% do two things with it: pass it as a continuation argument, or call it.
% The continuations are never returned and never stored inside heap objects
% or global variables. These conditions are sufficient to ensure that
% we never keep the address of a nested function after the containing
% functions has returned, so we won't get any dangling continuations.

%-----------------------------------------------------------------------------%
% CODE GENERATION SUMMARY
%-----------------------------------------------------------------------------%
%
% In each procedure, we declare a local variable `MR_bool succeeded'.
% This is used to hold the success status of semidet sub-goals.
% Note that the comments below show local declarations for the
% `succeeded' variable in all the places where they would be
% needed if we were generating them locally, but currently
% we actually just generate a single `succeeded' variable for
% each procedure.
%
% The calling convention for sub-goals is as follows.
%
%	model_det goal:
%		On success, fall through.
%		(May clobber `succeeded'.)
%	model_semi goal:
%		On success, set `succeeded' to MR_TRUE and fall through.
%		On failure, set `succeeded' to MR_FALSE and fall through.
%	multi/nondet goal:
%		On success, call the current success continuation.
%		On failure, fall through.
%		(May clobber `succeeded' in either case.)
%
% In comments, we use the following notation to distinguish between
% these three.
%
%	model_det goal:
%		<do Goal>
%			This means execute Goal (which must be model_det).
%	model_semi goal:
%		<succeeded = Goal>
%			This means execute Goal, and set `succeeded' to
%			MR_TRUE if the goal succeeds and MR_FALSE if it fails.
%	model_non goal:
%		<Goal && CONT()>
%			This means execute Goal, calling the success
%			continuation function CONT() if it succeeds,
%			and falling through if it fails.
%
% The notation
%
%	[situation]:
%		<[construct]>
%	===>
%		[code]
%
% means that in the situation described by [situation],
% for the the specified [construct] we will generate the specified [code].

% There is one other important thing which can be considered part of the
% calling convention for the code that we generate for each goal.
% If static ground term optimization is enabled, then for the terms
% marked as static by mark_static_terms.m, we will generate static consts.
% These static consts can refer to other static consts defined earlier.
% We need to be careful about the scopes of variables to ensure that
% for any term that mark_static_terms.m marks as static, the C constants
% representing the arguments of that term are in scope at the point
% where that term is constructed. Basically this means that
% all the static consts generated inside a goal must be hoist out to
% the top level scope for that goal, except for goal types where
% goal_expr_mark_static_terms (in mark_static_terms.m) returns the
% same static_info unchanged, i.e. branched goals and negations.
%
% Handling static constants also requires that the calls to ml_gen_goal
% for each subgoal must be done in the right order, so that the
% const_num_map in the ml_gen_info holds the right sequence numbers
% for the constants in scope.

%-----------------------------------------------------------------------------%
%
% Code for wrapping goals
%
%	If a model_foo goal occurs in a model_bar context, where foo != bar,
%	then we need to modify the code that we emit for the goal so that
%	it conforms to the calling convenion expected for model_bar.

%	det goal in semidet context:
%		<succeeded = Goal>
%	===>
%		<do Goal>
%		succeeded = MR_TRUE;

%	det goal in nondet context:
%		<Goal && SUCCEED()>
%	===>
%		<do Goal>
%		SUCCEED();

%	semi goal in nondet context:
%		<Goal && SUCCEED()>
%	===>
%		MR_bool succeeded;
%
%		<succeeded = Goal>
%		if (succeeded) SUCCEED();

%-----------------------------------------------------------------------------%
%
% Code for commits
%

% There's several different ways of handling commits:
%	- using catch/throw
%	- using setjmp/longjmp
%	- using GCC's __builtin_setjmp/__builtin_longjmp
%	- exiting nested functions via gotos to
%	  their containing functions
%
% The MLDS data structure abstracts away these differences
% using the `try_commit' and `do_commit' instructions.
% The comments below show the MLDS try_commit/do_commit version first,
% but for clarity I've also included sample code using each of the three
% different techniques. This shows how the MLDS->target back-end can map
% mlds__commit_type, do_commit and try_commit into target language
% constructs.
%
% Note that if we're using GCC's __builtin_longjmp(),
% then it is important that the call to __builtin_longjmp() be
% put in its own function, to ensure that it is not in the same
% function as the __builtin_setjmp().
% The code generation schema below does that automatically.
% We will need to be careful with MLDS optimizations to
% ensure that we preserve that invariant, though.
% (Alternatively, we could just call a function that
% calls __builtin_longjmp() rather than calling it directly.
% But that would be a little less efficient.)
%
% If those methods turn out to be too inefficient,
% another alternative would be to change the generated
% code so that after every function call, it would check a flag,
% and if that flag was set, it would return.
% Then MR_DO_COMMIT would just set the flag and return.
% The flag could be in a global (or thread-local) variable,
% or it could be an additional value returned from each function.

%	model_non in semi context: (using try_commit/do_commit)
%		<succeeded = Goal>
% 	===>
%		MR_COMMIT_TYPE ref;
%		void success() {
%			MR_DO_COMMIT(ref);
%		}
%		MR_TRY_COMMIT(ref, {
%			<Goal && success()>
%			succeeded = MR_FALSE;
%		}, {
%			succeeded = MR_TRUE;
%		})

%	model_non in semi context: (using catch/throw)
%		<succeeded = Goal>
% 	===>
%		void success() {
%			throw COMMIT();
%		}
%		try {
%			<Goal && success()>
%			succeeded = MR_FALSE;
%		} catch (COMMIT) {
%			succeeded = MR_TRUE;
%		}

%	The above is using C++ syntax. Here COMMIT is an exception type,
%	which can be defined trivially (e.g. "class COMMIT {};").
%	Note that when using catch/throw, we don't need the "ref" argument
%	at all; the target language's exception handling implementation
%	keeps track of all the information needed to unwind the stack.

%	model_non in semi context: (using setjmp/longjmp)
%		<succeeded = Goal>
% 	===>
%		jmp_buf ref;
%		void success() {
%			longjmp(ref, 1);
%		}
%		if (setjmp(ref)) {
%			succeeded = MR_TRUE;
%		} else {
%			<Goal && success()>
%			succeeded = MR_FALSE;
%		}

%	model_non in semi context: (using GNU C nested functions,
%				GNU C local labels, and exiting
%				the nested function by a goto
%				to a label in the containing function)
%		<succeeded = Goal>
% 	===>
%		__label__ commit;
%		void success() {
%			goto commit;
%		}
%		<Goal && success()>
%		succeeded = MR_FALSE;
%		goto commit_done;
%	commit:
%		succeeded = MR_TRUE;
%	commit_done:
%		;

%	model_non in det context: (using try_commit/do_commit)
%		<do Goal>
%	===>
%		MR_COMMIT_TYPE ref;
%		void success() {
%			MR_DO_COMMIT(ref);
%		}
%		MR_TRY_COMMIT(ref, {
%			<Goal && success()>
%		}, {})

%	model_non in det context (using GNU C nested functions,
%				GNU C local labels, and exiting
%				the nested function by a goto
%				to a label in the containing function)
%		<do Goal>
%	===>
%		__label__ done;
%		void success() {
%			goto done;
%		}
%		<Goal && success()>
%	done:	;

%	model_non in det context (using catch/throw):
%		<do Goal>
%	===>
%		void success() {
%			throw COMMIT();
%		}
%		try {
%			<Goal && success()>
%		} catch (COMMIT) {}

%	model_non in det context (using setjmp/longjmp):
%		<do Goal>
% 	===>
%		jmp_buf ref;
%		void success() {
%			longjmp(ref, 1);
%		}
%		if (setjmp(ref) == 0) {
%			<Goal && success()>
%		}

% Note that for all of these versions, we must hoist any static declarations
% generated for <Goal> out to the top level; this is needed so that such
% declarations remain in scope for any following goals.

%-----------------------------------------------------------------------------%
%
% Code for empty conjunctions (`true')
%

%	model_det goal:
%		<do true>
%	===>
%		/* fall through */

%	model_semi goal:
%		<succeeded = true>
%	===>
%		succceeded = MR_TRUE;

%	model_non goal
%		<true && CONT()>
%	===>
%		CONT();

%-----------------------------------------------------------------------------%
%
% Code for non-empty conjunctions
%

% We need to handle the case where the first goal cannot succeed
% specially:
%
%	at_most_zero Goal:
%		<Goal, Goals>
%	===>
%		<Goal>
%
% The remaining cases for conjunction all assume that the first
% goal's determinism is not `erroneous' or `failure'.

% If the first goal is model_det, it is straight-forward:
%
%	model_det Goal:
%		<Goal, Goals>
% 	===>
%		<do Goal>
%		<Goals>

% If the first goal is model_semidet, then there are two cases:
% if the conj as a whole is semidet, things are simple, and
% if the conj as a whole is model_non, then we do the same as
% for the semidet case, except that we also (ought to) declare
% a local `succeeded' variable.
%
%	model_semi Goal in model_semi conj:
%		<succeeded = (Goal, Goals)>
% 	===>
%		<succeeded = Goal>;
%		if (succeeded) {
%			<Goals>;
%		}
%
%	model_semi Goal in model_non conj:
%		<Goal && Goals>
% 	===>
%		MR_bool succeeded;
%
%		<succeeded = Goal>;
%		if (succeeded) {
%			<Goals>;
%		}
%
% The actual code generation scheme we use is slightly
% different to that: we hoist any declarations generated
% for <Goals> to the outer scope, rather than keeping
% them inside the `if', so that they remain in
% scope for any later goals which follow this.
% This is needed for declarations of static consts.

% For model_non goals, there are a couple of different
% ways that we could generate code, depending on whether
% we are aiming to maximize readability, or whether we
% prefer to generate code that may be more efficient
% but is a little less readable. The more readable method
% puts the generated goals in the same order that
% they occur in the source code:
%
%	model_non Goal (optimized for readability)
%		<Goal, Goals>
% 	===>
%		entry_func() {
%			<Goal && succ_func()>;
%		}
%		succ_func() {
%			<Goals && SUCCEED()>;
%		}
%
%		entry_func();
%
% The more efficient method generates the goals in
% reverse order, so it's less readable, but it has fewer
% function calls and can make it easier for the C compiler
% to inline things:
%
%	model_non Goal (optimized for efficiency):
%		<Goal, Goals>
% 	===>
%		succ_func() {
%			<Goals && SUCCEED()>;
%		}
%
%		<Goal && succ_func()>;
%
% The more efficient method is the one we actually use.
%
% Here's how those two methods look on longer
% conjunctions of nondet goals:
%
%	model_non goals (optimized for readability):
%		<Goal1, Goal2, Goal3, Goals>
% 	===>
%		label0_func() {
%			<Goal1 && label1_func()>;
%		}
%		label1_func() {
%			<Goal2 && label2_func()>;
%		}
%		label2_func() {
%			<Goal3 && label3_func()>;
%		}
%		label3_func() {
%			<Goals && SUCCEED()>;
%		}
%
%		label0_func();
%
%	model_non goals (optimized for efficiency):
%		<Goal1, Goal2, Goal3, Goals>
% 	===>
%		label1_func() {
%			label2_func() {
%				label3_func() {
%					<Goals && SUCCEED()>;
%				}
%				<Goal3 && label3_func()>;
%			}
%			<Goal2 && label2_func()>;
%		}
%		<Goal1 && label1_func()>;
%
% Note that it might actually make more sense to generate
% conjunctions of nondet goals like this:
%
%	model_non goals (optimized for efficiency, alternative version):
%		<Goal1, Goal2, Goal3, Goals>
% 	===>
%		label3_func() {
%			<Goals && SUCCEED()>;
%		}
%		label2_func() {
%			<Goal3 && label3_func()>;
%		}
%		label1_func() {
%			<Goal2 && label2_func()>;
%		}
%
%		<Goal1 && label1_func()>;
%
% This would avoid the undesirable deep nesting that we sometimes get
% with our current scheme. However, if we're eliminating nested
% functions, as is normally the case, then after the ml_elim_nested
% transformation all the functions and variables have been hoisted
% to the top level, so there is no difference between these two.
%
% As with semidet conjunctions, we hoist declarations
% out so that they remain in scope for any following goals.
% This is needed for declarations of static consts.
% However, we want to keep the declarations of non-static
% variables local, since accessing local variables is more
% efficient that accessing variables in the environment
% from a nested function. So we only hoist declarations
% of static constants.

%-----------------------------------------------------------------------------%
%
% Code for empty disjunctions (`fail')
%

%	model_semi goal:
%		<succeeded = fail>
%	===>
%		succeeded = MR_FALSE;

%	model_non goal:
%		<fail && CONT()>
%	===>
%		/* fall through */

%-----------------------------------------------------------------------------%
%
% Code for non-empty disjunctions
%

% model_det disj:

%	model_det Goal:
%		<do (Goal ; Goals)>
%	===>
%		<do Goal>
%		/* <Goals> will never be reached */

%	model_semi Goal:
%		<do (Goal ; Goals)>
%	===>
%		MR_bool succeeded;
%
%		<succeeded = Goal>;
%		if (!succeeded) {
%			<do Goals>;
%		}

% model_semi disj:

%	model_det Goal:
%		<succeeded = (Goal ; Goals)>
%	===>
%		MR_bool succeeded;
%
%		<do Goal>
%		succeeded = MR_TRUE
%		/* <Goals> will never be reached */

%	model_semi Goal:
%		<succeeded = (Goal ; Goals)>
%	===>
%		MR_bool succeeded;
%
%		<succeeded = Goal>;
%		if (!succeeded) {
%			<succeeded = Goals>;
%		}

% model_non disj:
%
%	model_det Goal:
%		<(Goal ; Goals) && SUCCEED()>
%	===>
%		<Goal>
%		SUCCEED();
%		<Goals && SUCCEED()>
%
%	model_semi Goal:
%		<(Goal ; Goals) && SUCCEED()>
%	===>
%		MR_bool succeeded;
%
%		<succeeded = Goal>
%		if (succeeded) SUCCEED();
%		<Goals && SUCCEED()>
%
%	model_non Goal:
%		<(Goal ; Goals) && SUCCEED()>
%	===>
%		<Goal && SUCCEED()>
%		<Goals && SUCCEED()>

%-----------------------------------------------------------------------------%
%
% Code for if-then-else
%

%	model_det Cond:
%		<(Cond -> Then ; Else)>
%	===>
%		<Cond>
%		<Then>

%	model_semi Cond:
%		<(Cond -> Then ; Else)>
%	===>
%		MR_bool succeeded;
%
%		<succeeded = Cond>
%		if (succeeded) {
%			<Then>
%		} else {
%			<Else>
%		}

%	/*
%	** XXX The following transformation does not do as good a job of GC
%	** as it could. Ideally we ought to ensure that stuff used only
%	** in the `Else' part will be reclaimed if a GC occurs during
%	** the `Then' part. But that is a bit tricky to achieve.
%	*/
%
%	model_non Cond:
%		<(Cond -> Then ; Else)>
%	===>
%		MR_bool cond_<N>;
%
%		void then_func() {
%			cond_<N> = MR_TRUE;
%			<Then>
%		}
%
%		cond_<N> = MR_FALSE;
%		<Cond && then_func()>
%		if (!cond_<N>) {
%			<Else>
%		}
%	except that we hoist any declarations generated
%	for <Cond> to the top of the scope, so that they
%	are in scope for the <Then> goal
%	(this is needed for declarations of static consts)

%-----------------------------------------------------------------------------%
%
% Code for negation
%

% model_det negation
%		<not(Goal)>
%	===>
%		MR_bool succeeded;
%		<succeeded = Goal>
%		/* now ignore the value of succeeded,
%		 which we know will be MR_FALSE */

% model_semi negation, model_det Goal:
%		<succeeded = not(Goal)>
%	===>
%		<do Goal>
%		succeeded = MR_FALSE;

% model_semi negation, model_semi Goal:
%		<succeeded = not(Goal)>
%	===>
%		<succeeded = Goal>
%		succeeded = !succeeded;

%-----------------------------------------------------------------------------%
%
% Code for deconstruction unifications
%

%	det (cannot_fail) deconstruction:
%		<succeeded = (X => f(A1, A2, ...))>
% 	===>
%		A1 = arg(X, f, 1);		% extract arguments
%		A2 = arg(X, f, 2);
%		...

%	semidet (can_fail) deconstruction:
%		<X => f(A1, A2, ...)>
% 	===>
%		<succeeded = (X => f(_, _, _, _))>	% tag test
%		if (succeeded) {
%			A1 = arg(X, f, 1);		% extract arguments
%			A2 = arg(X, f, 2);
%			...
%		}

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

% This back-end is still not yet 100% complete.
%
% Done:
%	- function prototypes
%	- code generation for det, semidet, and nondet predicates/functions:
%		- conjunctions
%		- disjunctions
%		- negation
%		- if-then-else
%		- predicate/function calls
%		- higher-order calls
%		- unifications
%			- assignment
%			- simple tests
%			- constructions
%			- deconstructions
%		- switches
%		- commits
%		- `pragma c_code'
%	- RTTI
%	- high level data representation
%	  (i.e. generate MLDS type declarations for user-defined types)
%	- support trailing
%
% BUGS:
%	- XXX parameter passing problem for abstract equivalence types
%	  that are defined as float (or anything which doesn't map to `Word')
%
% TODO:
%	- XXX define compare & unify preds for RTTI types
%	- XXX need to generate correct layout information for closures
%	  so that tests/hard_coded/copy_pred works.
%	- XXX fix ANSI/ISO C conformance of the generated code (i.e. port to lcc)
%
% UNIMPLEMENTED FEATURES:
%	- test --det-copy-out
%	- fix --gcc-nested-functions (need forward declarations for
%	  nested functions)
%	- support debugging (with mdb)
%	- support genuine parallel conjunction
%	- support fact tables
%	- support --split-c-files
%	- support accurate GC
%
% POTENTIAL EFFICIENCY IMPROVEMENTS:
%	- optimize unboxed float on DEC Alphas.
%	- generate better code for switches:
%		- optimize switches so that the recursive case comes first
%		  (see switch_gen.m).
%		- apply the reverse tag test optimization
%		  for types with two functors (see unify_gen.m)
%		- binary search switches
%		- lookup switches
%	- generate local declarations for the `succeeded' variable;
%	  this would help in nondet code, because it would avoid
%	  the need to access the outermost function's `succeeded'
%	  variable via the environment pointer
%	  (be careful about the interaction with setjmp(), though)

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

:- module ml_backend__ml_code_gen.

:- interface.

:- import_module hlds__code_model.
:- import_module hlds__hlds_goal.
:- import_module hlds__hlds_module.
:- import_module ml_backend__ml_code_util.
:- import_module ml_backend__mlds.
:- import_module parse_tree__prog_data.

:- import_module io, map.

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

	% Generate MLDS code for an entire module.
	%
:- pred ml_code_gen(module_info::in, mlds::out, io::di, io::uo) is det.

	% Generate MLDS code for the specified goal in the
	% specified code model. Return the result as a single statement
	% (which may be a block statement containing nested declarations).
	%
:- pred ml_gen_goal(code_model::in, hlds_goal::in, mlds__statement::out,
	ml_gen_info::in, ml_gen_info::out) is det.

	% Generate MLDS code for the specified goal in the
	% specified code model. Return the result as two lists,
	% one containing the necessary declarations and the other
	% containing the generated statements.
	%
:- pred ml_gen_goal(code_model::in, hlds_goal::in,
	mlds__defns::out, mlds__statements::out,
	ml_gen_info::in, ml_gen_info::out) is det.

	% ml_gen_wrap_goal(OuterCodeModel, InnerCodeModel, Context,
	%		Statements0, Statements):
	%
	%	OuterCodeModel is the code model expected by the
	%	context in which a goal is called. InnerCodeModel
	%	is the code model which the goal actually has.
	%	This predicate converts the code generated for
	%	the goal using InnerCodeModel into code that uses
	%	the calling convention appropriate for OuterCodeModel.
	%
:- pred ml_gen_wrap_goal(code_model::in, code_model::in, prog_context::in,
	mlds__statements::in, mlds__statements::out,
	ml_gen_info::in, ml_gen_info::out) is det.

	% Generate declarations for a list of local variables.
	%
:- pred ml_gen_local_var_decls(prog_varset::in, map(prog_var, prog_type)::in,
	prog_context::in, prog_vars::in, mlds__defns::out,
	ml_gen_info::in, ml_gen_info::out) is det.

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

:- implementation.

:- import_module backend_libs__builtin_ops.
:- import_module backend_libs__c_util.
:- import_module backend_libs__export.
:- import_module backend_libs__foreign. % XXX needed for pragma foreign code
:- import_module check_hlds__mode_util.
:- import_module check_hlds__type_util.
:- import_module hlds__goal_util.
:- import_module hlds__hlds_data.
:- import_module hlds__hlds_pred.
:- import_module hlds__passes_aux.
:- import_module libs__globals.
:- import_module libs__options.
:- import_module mdbcomp__prim_data.
:- import_module ml_backend__ml_call_gen.
:- import_module ml_backend__ml_code_util.
:- import_module ml_backend__ml_switch_gen.
:- import_module ml_backend__ml_type_gen.
:- import_module ml_backend__ml_unify_gen.
:- import_module parse_tree__error_util.
:- import_module parse_tree__modules.
:- import_module parse_tree__prog_util.
:- import_module parse_tree__prog_type.

:- import_module assoc_list, bool, string, list.
:- import_module int, set, term, require, std_util.

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

	% Generate MLDS code for an entire module.
	%
ml_code_gen(ModuleInfo, MLDS, !IO) :-
	module_info_name(ModuleInfo, ModuleName),
	ml_gen_foreign_code(ModuleInfo, ForeignCode, !IO),
	ml_gen_imports(ModuleInfo, Imports),
	ml_gen_defns(ModuleInfo, Defns, !IO),
	MLDS = mlds(ModuleName, ForeignCode, Imports, Defns).

:- pred ml_gen_foreign_code(module_info::in,
	map(foreign_language, mlds__foreign_code)::out,
	io::di, io::uo) is det.

ml_gen_foreign_code(ModuleInfo, AllForeignCode, !IO) :-
	module_info_get_foreign_decl(ModuleInfo, ForeignDecls),
	module_info_get_foreign_import_module(ModuleInfo, ForeignImports),
	module_info_get_foreign_body_code(ModuleInfo, ForeignBodys),
	globals__io_get_backend_foreign_languages(BackendForeignLanguages,
		!IO),

	WantedForeignImports = list__condense(
		list__map((func(L) = Imports :-
			foreign__filter_imports(L, ForeignImports, Imports, _)
		), BackendForeignLanguages)),

	list__foldl(ml_gen_foreign_code_lang(ModuleInfo, ForeignDecls,
		ForeignBodys, WantedForeignImports),
		BackendForeignLanguages, map__init, AllForeignCode).

:- pred ml_gen_foreign_code_lang(module_info::in, foreign_decl_info::in,
	foreign_body_info::in, foreign_import_module_info::in,
	foreign_language::in,
	map(foreign_language, mlds__foreign_code)::in,
	map(foreign_language, mlds__foreign_code)::out) is det.

ml_gen_foreign_code_lang(ModuleInfo, ForeignDecls, ForeignBodys,
		WantedForeignImports, Lang, Map0, Map) :-
	foreign__filter_decls(Lang, ForeignDecls, WantedForeignDecls,
		_OtherForeignDecls),
	foreign__filter_bodys(Lang, ForeignBodys, WantedForeignBodys,
		_OtherForeignBodys),
	ConvBody = (func(foreign_body_code(L, S, C)) =
		user_foreign_code(L, S, C)),
	MLDSWantedForeignBodys = list__map(ConvBody,
		WantedForeignBodys),
		% XXX exports are only implemented for
		% C and IL at the moment
	( ( Lang = c ; Lang = il ) ->
		ml_gen_pragma_export(ModuleInfo, MLDS_PragmaExports)
	;
		MLDS_PragmaExports = []
	),
	MLDS_ForeignCode = mlds__foreign_code(WantedForeignDecls,
		WantedForeignImports, MLDSWantedForeignBodys,
		MLDS_PragmaExports),
	map__det_insert(Map0, Lang, MLDS_ForeignCode, Map).

:- pred ml_gen_imports(module_info::in, mlds__imports::out) is det.

ml_gen_imports(ModuleInfo, MLDS_ImportList) :-
		% Determine all the mercury imports.
		% XXX This is overly conservative,
		% i.e. we import more than we really need.
	module_info_globals(ModuleInfo, Globals),
	globals__get_target(Globals, Target),
	module_info_get_all_deps(ModuleInfo, AllImports0),
		% No module needs to import itself.
	module_info_name(ModuleInfo, ThisModule),
	AllImports = set__delete(AllImports0, ThisModule),
	P = (func(Name) = mercury_import(compiler_visible_interface,
		mercury_module_name_to_mlds(Name))),

		% For every foreign type determine the import needed to
		% find the declaration for that type.
	module_info_types(ModuleInfo, Types),
	ForeignTypeImports = list__condense(
		list__map(foreign_type_required_imports(Target),
			map__values(Types))),

	MLDS_ImportList = ForeignTypeImports ++
		list__map(P, set__to_sorted_list(AllImports)).

:- func foreign_type_required_imports(compilation_target, hlds_type_defn)
	= list(mlds__import).

foreign_type_required_imports(c, _) = [].
foreign_type_required_imports(il, TypeDefn) = Imports :-
	hlds_data__get_type_defn_body(TypeDefn, Body),
	(
		Body = foreign_type(foreign_type_body(MaybeIL, _MaybeC,
				_MaybeJava))
	->
		(
			MaybeIL = yes(Data),
			Data = foreign_type_lang_data(il(_, Location, _), _, _)
		->
			Name = il_assembly_name(mercury_module_name_to_mlds(
				unqualified(Location))),
			Imports = [foreign_import(Name)]

		;
			unexpected(this_file, "no IL type")
		)
	;
		Imports = []
	).
foreign_type_required_imports(java, _) = [].
foreign_type_required_imports(asm, _) = [].

:- pred ml_gen_defns(module_info::in, mlds__defns::out, io::di, io::uo) is det.

ml_gen_defns(ModuleInfo, Defns, !IO) :-
	ml_gen_types(ModuleInfo, TypeDefns, !IO),
	ml_gen_preds(ModuleInfo, PredDefns, !IO),
	Defns = list__append(TypeDefns, PredDefns).

%-----------------------------------------------------------------------------%
%
% For each pragma export declaration we associate with it the
% information used to generate the function prototype for the MLDS
% entity.
%

:- pred ml_gen_pragma_export(module_info::in, list(mlds__pragma_export)::out)
	is det.

ml_gen_pragma_export(ModuleInfo, MLDS_PragmaExports) :-
	module_info_get_pragma_exported_procs(ModuleInfo, PragmaExports),
	list__map(ml_gen_pragma_export_proc(ModuleInfo),
		PragmaExports, MLDS_PragmaExports).

:- pred ml_gen_pragma_export_proc(module_info::in, pragma_exported_proc::in,
	mlds__pragma_export::out) is det.

ml_gen_pragma_export_proc(ModuleInfo,
		pragma_exported_proc(PredId, ProcId, C_Name, ProgContext),
		Defn) :-

	ml_gen_proc_label(ModuleInfo, PredId, ProcId, Name, ModuleName),
	FuncParams = ml_gen_proc_params(ModuleInfo, PredId, ProcId),
	MLDS_Context = mlds__make_context(ProgContext),
	Defn = ml_pragma_export(C_Name, qual(ModuleName, module_qual, Name),
		FuncParams, MLDS_Context).

%-----------------------------------------------------------------------------%
%
% Stuff to generate MLDS code for HLDS predicates & functions.
%

	% Generate MLDS definitions for all the non-imported
	% predicates (and functions) in the HLDS.
	%
:- pred ml_gen_preds(module_info::in, mlds__defns::out, io::di, io::uo) is det.

ml_gen_preds(ModuleInfo, PredDefns, !IO) :-
	module_info_preds(ModuleInfo, PredTable),
	map__keys(PredTable, PredIds),
	PredDefns0 = [],
	ml_gen_preds_2(ModuleInfo, PredIds, PredTable, PredDefns0, PredDefns,
		!IO).

:- pred ml_gen_preds_2(module_info::in, list(pred_id)::in, pred_table::in,
	mlds__defns::in, mlds__defns::out, io::di, io::uo) is det.

ml_gen_preds_2(ModuleInfo, PredIds0, PredTable, !Defns, !IO) :-
	(
		PredIds0 = [PredId | PredIds],
		map__lookup(PredTable, PredId, PredInfo),
		pred_info_import_status(PredInfo, ImportStatus),
		(
			( ImportStatus = imported(_)
			; pred_info_is_aditi_relation(PredInfo)

				% We generate incorrect and unnecessary
				% code for the external special preds
				% which are pseudo_imported, so just
				% ignore them.
			; is_unify_or_compare_pred(PredInfo),
				ImportStatus = external(pseudo_imported)
			)
		->
			true
		;
			ml_gen_pred(ModuleInfo, PredId, PredInfo, ImportStatus,
				!Defns, !IO)
		),
		ml_gen_preds_2(ModuleInfo, PredIds, PredTable, !Defns, !IO)
	;
		PredIds0 = []
	).

	% Generate MLDS definitions for all the non-imported
	% procedures of a given predicate (or function).
	%
:- pred ml_gen_pred(module_info::in, pred_id::in, pred_info::in,
	import_status::in, mlds__defns::in, mlds__defns::out,
	io::di, io::uo) is det.

ml_gen_pred(ModuleInfo, PredId, PredInfo, ImportStatus, !Defns, !IO) :-
	( ImportStatus = external(_) ->
		ProcIds = pred_info_procids(PredInfo)
	;
		ProcIds = pred_info_non_imported_procids(PredInfo)
	),
	( ProcIds = [] ->
		true
	;
		write_pred_progress_message("% Generating MLDS code for ",
			PredId, ModuleInfo, !IO),
		pred_info_procedures(PredInfo, ProcTable),
		ml_gen_procs(ProcIds, ModuleInfo, PredId, PredInfo,
			ProcTable, !Defns)
	).

:- pred ml_gen_procs(list(proc_id)::in, module_info::in, pred_id::in,
	pred_info::in, proc_table::in, mlds__defns::in, mlds__defns::out)
	is det.

ml_gen_procs([], _, _, _, _, !Defns).
ml_gen_procs([ProcId | ProcIds], ModuleInfo, PredId, PredInfo, ProcTable,
		!Defns) :-
	map__lookup(ProcTable, ProcId, ProcInfo),
	ml_gen_proc(ModuleInfo, PredId, ProcId, PredInfo, ProcInfo, !Defns),
	ml_gen_procs(ProcIds, ModuleInfo, PredId, PredInfo, ProcTable, !Defns).

%-----------------------------------------------------------------------------%
%
% Code for handling individual procedures
%

	% Generate MLDS code for the specified procedure.
	%
:- pred ml_gen_proc(module_info::in, pred_id::in, proc_id::in, pred_info::in,
	proc_info::in, mlds__defns::in, mlds__defns::out) is det.

ml_gen_proc(ModuleInfo, PredId, ProcId, _PredInfo, ProcInfo, !Defns) :-
	proc_info_context(ProcInfo, Context),

	ml_gen_proc_label(ModuleInfo, PredId, ProcId, Name, _ModuleName),
	MLDS_Context = mlds__make_context(Context),
	DeclFlags = ml_gen_proc_decl_flags(ModuleInfo, PredId, ProcId),
	ml_gen_proc_defn(ModuleInfo, PredId, ProcId, ProcDefnBody, ExtraDefns),
	ProcDefn = mlds__defn(Name, MLDS_Context, DeclFlags, ProcDefnBody),
	!:Defns = list__append(ExtraDefns, [ProcDefn | !.Defns]),
	ml_gen_maybe_add_table_var(ModuleInfo, PredId, ProcId, ProcInfo,
		!Defns).

:- pred ml_gen_maybe_add_table_var(module_info::in, pred_id::in, proc_id::in,
	proc_info::in, mlds__defns::in, mlds__defns::out) is det.

ml_gen_maybe_add_table_var(ModuleInfo, PredId, ProcId, ProcInfo,
		Defns0, Defns) :-
	proc_info_eval_method(ProcInfo, EvalMethod),
	(
		eval_method_has_per_proc_tabling_pointer(EvalMethod) = yes
	->
		ml_gen_pred_label(ModuleInfo, PredId, ProcId,
			PredLabel, _PredModule),
		Var = tabling_pointer(PredLabel - ProcId),
		Type = mlds__generic_type,
		Initializer = init_obj(const(null(Type))),
		proc_info_context(ProcInfo, Context),
		(
			module_info_globals(ModuleInfo, Globals),
			globals__get_gc_method(Globals, GC_Method),
			GC_Method = accurate
		->
			% XXX To handle this case properly, the GC would
			% need to trace through the global variable
			% that we generate for the table pointer.
			% Support for this is not yet implemented.
			% Also, we'd need to add GC support (stack
			% frame registration, and calls to MR_GC_check())
			% to MR_make_long_lived() and MR_deep_copy()
			% so that we do garbage collection of the
			% "global heap" which is used to store the tables.
			sorry(this_file, "tabling and `--gc accurate'")
		;
			GC_TraceCode = no
		),
		TablePointerVarDefn = ml_gen_mlds_var_decl(
			Var, Type, Initializer, GC_TraceCode,
			mlds__make_context(Context)),
		Defns = [TablePointerVarDefn | Defns0]
	;
		Defns = Defns0
	).

	% Return the declaration flags appropriate for a procedure definition.
	%
:- func ml_gen_proc_decl_flags(module_info, pred_id, proc_id)
	= mlds__decl_flags.

ml_gen_proc_decl_flags(ModuleInfo, PredId, ProcId) = DeclFlags :-
	module_info_pred_info(ModuleInfo, PredId, PredInfo),
	( procedure_is_exported(ModuleInfo, PredInfo, ProcId) ->
		Access = public
	;
		Access = private
	),
	PerInstance = one_copy,
	Virtuality = non_virtual,
	Finality = overridable,
	Constness = modifiable,
	Abstractness = concrete,
	DeclFlags = init_decl_flags(Access, PerInstance,
		Virtuality, Finality, Constness, Abstractness).

	% Generate an MLDS definition for the specified procedure.
	%
:- pred ml_gen_proc_defn(module_info::in, pred_id::in, proc_id::in,
	mlds__entity_defn::out, mlds__defns::out) is det.

ml_gen_proc_defn(ModuleInfo, PredId, ProcId, ProcDefnBody, ExtraDefns) :-
	module_info_pred_proc_info(ModuleInfo, PredId, ProcId,
		PredInfo, ProcInfo),
	pred_info_import_status(PredInfo, ImportStatus),
	pred_info_arg_types(PredInfo, ArgTypes),
	proc_info_interface_code_model(ProcInfo, CodeModel),
	proc_info_headvars(ProcInfo, HeadVars),
	proc_info_argmodes(ProcInfo, Modes),
	proc_info_goal(ProcInfo, Goal0),

	%
	% The HLDS front-end sometimes over-estimates
	% the set of non-locals. We need to restrict
	% the set of non-locals for the top-level goal
	% to just the headvars, because otherwise variables
	% which occur in the top-level non-locals but which
	% are not really non-local will not be declared.
	%
	Goal0 = GoalExpr - GoalInfo0,
	goal_info_get_code_gen_nonlocals(GoalInfo0, NonLocals0),
	set__list_to_set(HeadVars, HeadVarsSet),
	set__intersect(HeadVarsSet, NonLocals0, NonLocals),
	goal_info_set_code_gen_nonlocals(GoalInfo0, NonLocals, GoalInfo),
	Goal = GoalExpr - GoalInfo,

	goal_info_get_context(GoalInfo, Context),

	Info0 = ml_gen_info_init(ModuleInfo, PredId, ProcId),

	( ImportStatus = external(_) ->
		%
		% For Mercury procedures declared `:- external', we generate
		% an MLDS definition for them with no function body.
		% The MLDS -> target code pass can treat this accordingly,
		% e.g. for C it outputs a function declaration with no
		% corresponding definition, making sure that the function
		% is declared as `extern' rather than `static'.
		%
		FunctionBody = external,
		ExtraDefns = [],
		ml_gen_proc_params(PredId, ProcId, MLDS_Params, Info0, _Info)
	;
		% Set up the initial success continuation, if any.
		% Also figure out which output variables are returned by
		% value (rather than being passed by reference) and remove
		% them from the byref_output_vars field in the ml_gen_info.
		( CodeModel = model_non ->
 			ml_set_up_initial_succ_cont(ModuleInfo,
				CopiedOutputVars, Info0, Info1)
 		;
			ml_det_copy_out_vars(ModuleInfo,
			 	CopiedOutputVars, Info0, Info1)
		),

		% This would generate all the local variables at the top of
		% the function:
		%	ml_gen_all_local_var_decls(Goal,
		% 		VarSet, VarTypes, HeadVars, MLDS_LocalVars,
		%		Info1, Info2)
		% But instead we now generate them locally for each goal.
		% We just declare the `succeeded' var here, plus locals
		% for any output arguments that are returned by value
		% (e.g. if --nondet-copy-out is enabled, or for det function
		% return values).
		( CopiedOutputVars = [] ->
			% optimize common case
			OutputVarLocals = [],
			Info2 = Info1
		;
			proc_info_varset(ProcInfo, VarSet),
			proc_info_vartypes(ProcInfo, VarTypes),
			% note that for headvars we must use the types from
			% the procedure interface, not from the procedure body
			HeadVarTypes = map__from_corresponding_lists(HeadVars,
				ArgTypes),
			ml_gen_local_var_decls(VarSet,
				map__overlay(VarTypes, HeadVarTypes),
				Context, CopiedOutputVars, OutputVarLocals,
				Info1, Info2)
		),
		MLDS_Context = mlds__make_context(Context),
		MLDS_LocalVars = [ml_gen_succeeded_var_decl(MLDS_Context) |
			OutputVarLocals],
		modes_to_arg_modes(ModuleInfo, Modes, ArgTypes, ArgModes),
		ml_gen_proc_body(CodeModel, HeadVars, ArgTypes, ArgModes,
			CopiedOutputVars, Goal, Decls0, Statements,
			Info2, Info3),
		ml_gen_proc_params(PredId, ProcId, MLDS_Params, Info3, Info),
		ml_gen_info_get_extra_defns(Info, ExtraDefns),
		Decls = list__append(MLDS_LocalVars, Decls0),
		Statement = ml_gen_block(Decls, Statements, Context),
		FunctionBody = defined_here(Statement)
	),

	pred_info_get_attributes(PredInfo, Attributes),
	attributes_to_attribute_list(Attributes, AttributeList),

	MLDS_Attributes = attributes_to_mlds_attributes(ModuleInfo,
		AttributeList),

	ProcDefnBody = mlds__function(yes(proc(PredId, ProcId)),
		MLDS_Params, FunctionBody, MLDS_Attributes).

	% for model_det and model_semi procedures,
	% figure out which output variables are returned by
	% value (rather than being passed by reference) and remove
	% them from the byref_output_vars field in the ml_gen_info.
:- pred ml_det_copy_out_vars(module_info::in, list(prog_var)::out,
	ml_gen_info::in, ml_gen_info::out) is det.

ml_det_copy_out_vars(ModuleInfo, CopiedOutputVars, !Info) :-
	ml_gen_info_get_byref_output_vars(!.Info, OutputVars),
	module_info_globals(ModuleInfo, Globals),
	globals__lookup_bool_option(Globals, det_copy_out, DetCopyOut),
	(
		% if --det-copy-out is enabled, all output variables
		% are returned by value, rather than passing
		% them by reference.
		DetCopyOut = yes
	->
		ByRefOutputVars = [],
		CopiedOutputVars = OutputVars
	;
		% for det functions, the function result variable
		% is returned by value, and any remaining output
		% variables are passed by reference
		ml_gen_info_get_pred_id(!.Info, PredId),
		ml_gen_info_get_proc_id(!.Info, ProcId),
		ml_is_output_det_function(ModuleInfo, PredId, ProcId,
			ResultVar)
	->
		CopiedOutputVars = [ResultVar],
		list__delete_all(OutputVars, ResultVar, ByRefOutputVars)
	;
		% otherwise, all output vars are passed by reference
		CopiedOutputVars = [],
		ByRefOutputVars = OutputVars
	),
	ml_gen_info_set_byref_output_vars(ByRefOutputVars, !Info),
	ml_gen_info_set_value_output_vars(CopiedOutputVars, !Info).

	% for model_non procedures,
	% figure out which output variables are returned by
	% value (rather than being passed by reference) and remove
	% them from the byref_output_vars field in the ml_gen_info,
	% and construct the initial success continuation.
:- pred ml_set_up_initial_succ_cont(module_info::in, list(prog_var)::out,
	ml_gen_info::in, ml_gen_info::out) is det.

ml_set_up_initial_succ_cont(ModuleInfo, NondetCopiedOutputVars, !Info) :-
	module_info_globals(ModuleInfo, Globals),
	globals__lookup_bool_option(Globals, nondet_copy_out,
		NondetCopyOut),
	( NondetCopyOut = yes ->
		% for --nondet-copy-out, we generate local variables
		% for the output variables and then pass them to the
		% continuation, rather than passing them by reference.
		ml_gen_info_get_byref_output_vars(!.Info,
			NondetCopiedOutputVars),
		ml_gen_info_set_byref_output_vars([], !Info)
	;
		NondetCopiedOutputVars = []
	),
	ml_gen_info_set_value_output_vars(NondetCopiedOutputVars, !Info),
	ml_gen_var_list(!.Info, NondetCopiedOutputVars, OutputVarLvals),
	ml_variable_types(!.Info, NondetCopiedOutputVars, OutputVarTypes),
	ml_initial_cont(!.Info, OutputVarLvals, OutputVarTypes, InitialCont),
	ml_gen_info_push_success_cont(InitialCont, !Info).

	% Generate MLDS definitions for all the local variables in a function.
	%
	% Note that this function generates all the local variables at the
	% top of the function. It might be a better idea to instead
	% generate local declarations for all the variables used in
	% each sub-goal.
	%
:- pred ml_gen_all_local_var_decls(hlds_goal::in, prog_varset::in,
	map(prog_var, prog_type)::in, list(prog_var)::in, mlds__defns::out,
	ml_gen_info::in, ml_gen_info::out) is det.

ml_gen_all_local_var_decls(Goal, VarSet, VarTypes, HeadVars, MLDS_LocalVars,
		!Info) :-
	Goal = _ - GoalInfo,
	goal_info_get_context(GoalInfo, Context),
	goal_util__goal_vars(Goal, AllVarsSet),
	set__delete_list(AllVarsSet, HeadVars, LocalVarsSet),
	set__to_sorted_list(LocalVarsSet, LocalVars),
	ml_gen_local_var_decls(VarSet, VarTypes, Context, LocalVars,
		MLDS_LocalVars0, !Info),
	MLDS_Context = mlds__make_context(Context),
	MLDS_SucceededVar = ml_gen_succeeded_var_decl(MLDS_Context),
	MLDS_LocalVars = [MLDS_SucceededVar | MLDS_LocalVars0].

	% Generate declarations for a list of local variables.
	%
ml_gen_local_var_decls(_VarSet, _VarTypes, _Context, [], [], !Info).
ml_gen_local_var_decls(VarSet, VarTypes, Context, [Var | Vars], Defns,
		!Info) :-
	map__lookup(VarTypes, Var, Type),
	( type_util__is_dummy_argument_type(Type) ->
		% no declaration needed for this variable
		ml_gen_local_var_decls(VarSet, VarTypes, Context, Vars,
			Defns, !Info)
	;
		VarName = ml_gen_var_name(VarSet, Var),
		ml_gen_var_decl(VarName, Type, Context, Defn, !Info),
		ml_gen_local_var_decls(VarSet, VarTypes, Context, Vars,
			Defns0, !Info),
		Defns = [Defn | Defns0]
	).

	% Generate the code for a procedure body.
	%
:- pred ml_gen_proc_body(code_model::in, list(prog_var)::in,
	list(prog_type)::in, list(arg_mode)::in, list(prog_var)::in,
	hlds_goal::in, mlds__defns::out, mlds__statements::out,
	ml_gen_info::in, ml_gen_info::out) is det.

ml_gen_proc_body(CodeModel, HeadVars, ArgTypes, ArgModes, CopiedOutputVars,
		Goal, Decls, Statements, !Info) :-
	Goal = _ - GoalInfo,
	goal_info_get_context(GoalInfo, Context),

	%
	% First just generate the code for the procedure's goal.
	%
	DoGenGoal = ml_gen_goal(CodeModel, Goal),

	%
	% In certain cases -- for example existentially typed procedures,
	% or unification/compare procedures for equivalence types --
	% the parameters types may not match the types of the head variables.
	% In such cases, we need to box/unbox/cast them to the right type.
	% We also grab the original (uncast) lvals for the copied output
	% variables (if any) here, since for the return statement that
	% we append below, we want the original vars, not their cast versions.
	%
	ml_gen_var_list(!.Info, CopiedOutputVars,
		CopiedOutputVarOriginalLvals),
	ml_gen_convert_headvars(HeadVars, ArgTypes, ArgModes, CopiedOutputVars,
		Context, ConvDecls, ConvInputStatements, ConvOutputStatements,
		!Info),
	(
		ConvDecls = [],
		ConvInputStatements = [],
		ConvOutputStatements = []
	->
		% No boxing/unboxing/casting required.
		DoGenGoal(Decls, Statements1, !Info)
	;
		% Boxing/unboxing/casting required.
		% We need to convert the input arguments,
		% generate the goal, convert the output arguments,
		% and then succeeed.
		DoConvOutputs = (pred(NewDecls::out, NewStatements::out,
				Info0::in, Info::out) is det :-
			ml_gen_success(CodeModel, Context, SuccStatements,
				Info0, Info),
			NewDecls = [],
			NewStatements = list__append(ConvOutputStatements,
				SuccStatements)
		),
		ml_combine_conj(CodeModel, Context,
			DoGenGoal, DoConvOutputs,
			Decls0, Statements0, !Info),
		Statements1 = list__append(ConvInputStatements,
			Statements0),
		Decls = list__append(ConvDecls, Decls0)
	),

	%
	% Finally append an appropriate `return' statement, if needed.
	%
	ml_append_return_statement(!.Info, CodeModel,
		CopiedOutputVarOriginalLvals, Context,
		Statements1, Statements).

%
% In certain cases -- for example existentially typed procedures,
% or unification/compare procedures for equivalence types --
% the parameter types may not match the types of the head variables.
% In such cases, we need to box/unbox/cast them to the right type.
% This procedure handles that.
%
:- pred ml_gen_convert_headvars(list(prog_var)::in, list(prog_type)::in,
	list(arg_mode)::in, list(prog_var)::in, prog_context::in,
	mlds__defns::out, mlds__statements::out, mlds__statements::out,
	ml_gen_info::in, ml_gen_info::out) is det.

ml_gen_convert_headvars(Vars, HeadTypes, ArgModes, CopiedOutputVars, Context,
		Decls, InputStatements, OutputStatements, !Info) :-
	(
		% base case
		Vars = [],
		HeadTypes = [],
		ArgModes = []
	->
		Decls = [],
		InputStatements = [],
		OutputStatements = []
	;
		% recursive case
		Vars = [Var | Vars1],
		HeadTypes = [HeadType | HeadTypes1],
		ArgModes = [ArgMode | ArgModes1]
	->
		ml_variable_type(!.Info, Var, BodyType),
		(
			%
			% Arguments with mode `top_unused' do not need
			% to be converted
			%
			ArgMode = top_unused
		->
			% just recursively process the remaining arguments
			ml_gen_convert_headvars(Vars1, HeadTypes1, ArgModes1,
				CopiedOutputVars, Context, Decls,
				InputStatements, OutputStatements, !Info)
		;
			%
			% Check whether HeadType is the same as BodyType
			% (modulo the term__contexts).
			% If so, no conversion is needed.
			%
			map__init(Subst0),
			type_unify(HeadType, BodyType, [], Subst0, Subst),
			map__is_empty(Subst)
		->
			% just recursively process the remaining arguments
			ml_gen_convert_headvars(Vars1, HeadTypes1, ArgModes1,
				CopiedOutputVars, Context, Decls,
				InputStatements, OutputStatements, !Info)
		;
			%
			% generate the lval for the head variable
			%
			ml_gen_var_with_type(!.Info, Var, HeadType,
				HeadVarLval),

			%
			% generate code to box or unbox that head variable,
			% to convert its type from HeadType to BodyType
			%
			ml_gen_info_get_varset(!.Info, VarSet),
			VarName = ml_gen_var_name(VarSet, Var),
			ml_gen_box_or_unbox_lval(HeadType, BodyType,
				HeadVarLval, VarName, Context, no, 0, BodyLval,
				ConvDecls, ConvInputStatements,
				ConvOutputStatements, !Info),

			%
			% Ensure that for any uses of this variable in the
			% procedure body, we use the BodyLval (which has type
			% BodyType) rather than the HeadVarLval (which has
			% type HeadType).
			%
			ml_gen_info_set_var_lval(Var, BodyLval, !Info),

			%
			% Recursively process the remaining arguments
			%
			ml_gen_convert_headvars(Vars1, HeadTypes1, ArgModes1,
				CopiedOutputVars, Context, Decls1,
				InputStatements1, OutputStatements1, !Info),

			%
			% Add the code to convert this input or output.
			%
			ml_gen_info_get_byref_output_vars(!.Info,
				ByRefOutputVars),
			(
				( list__member(Var, ByRefOutputVars)
				; list__member(Var, CopiedOutputVars)
				)
			->
				InputStatements = InputStatements1,
				OutputStatements =
					list__append(OutputStatements1,
					ConvOutputStatements)
			;
				InputStatements =
					list__append(ConvInputStatements,
					InputStatements1),
				OutputStatements = OutputStatements1
			),
			list__append(ConvDecls, Decls1, Decls)
		)
	;
		% neither base case nor recursive case matched
		unexpected(this_file,
			"ml_gen_convert_headvars: length mismatch")
	).

%-----------------------------------------------------------------------------%
%
% Stuff to generate code for goals.
%

	% Generate MLDS code for the specified goal in the
	% specified code model. Return the result as a single statement
	% (which may be a block statement containing nested declarations).
	%
ml_gen_goal(CodeModel, Goal, Statement, !Info) :-
	ml_gen_goal(CodeModel, Goal, Decls, Statements, !Info),
	Goal = _ - GoalInfo,
	goal_info_get_context(GoalInfo, Context),
	Statement = ml_gen_block(Decls, Statements, Context).

	% Generate MLDS code for the specified goal in the
	% specified code model. Return the result as two lists,
	% one containing the necessary declarations and the other
	% containing the generated statements.
	%
ml_gen_goal(CodeModel, Goal, Decls, Statements, !Info) :-
	Goal = GoalExpr - GoalInfo,
	goal_info_get_context(GoalInfo, Context),
	%
	% Generate the local variables for this goal.
	% We need to declare any variables which
	% are local to this goal (including its subgoals),
	% but which are not local to a subgoal.
	% (If they're local to a subgoal, they'll be declared
	% when we generate code for that subgoal.)
	%
	% We need to make sure that we declare any type_info or
	% type_classinfo variables *before* any other variables,
	% since the GC tracing code for the other variables may
	% refer to the type_info variables, so they need to be in scope.

	Locals = goal_local_vars(Goal),
	SubGoalLocals = union_of_direct_subgoal_locals(Goal),
	set__difference(Locals, SubGoalLocals, VarsToDeclareHere),
	set__to_sorted_list(VarsToDeclareHere, VarsList0),
	ml_gen_info_get_varset(!.Info, VarSet),
	ml_gen_info_get_var_types(!.Info, VarTypes),
	VarsList = put_typeinfo_vars_first(VarsList0, VarTypes),
	ml_gen_local_var_decls(VarSet, VarTypes, Context, VarsList, VarDecls,
		!Info),

	%
	% Generate code for the goal in its own code model.
	%
	goal_info_get_code_model(GoalInfo, GoalCodeModel),
	ml_gen_goal_expr(GoalExpr, GoalCodeModel, Context,
		GoalDecls, GoalStatements0, !Info),

	%
	% Add whatever wrapper is needed to convert the goal's
	% code model to the desired code model.
	%
	ml_gen_wrap_goal(CodeModel, GoalCodeModel, Context,
		GoalStatements0, GoalStatements, !Info),

	ml_join_decls(VarDecls, [], GoalDecls, GoalStatements, Context,
		Decls, Statements).

	% Return the set of variables which occur in the specified goal
	% (including in its subgoals) and which are local to that goal.
:- func goal_local_vars(hlds_goal) = set(prog_var).

goal_local_vars(Goal) = LocalVars :-
	% find all the variables in the goal
	goal_util__goal_vars(Goal, GoalVars),
	% delete the non-locals
	Goal = _ - GoalInfo,
	goal_info_get_code_gen_nonlocals(GoalInfo, NonLocalVars),
	set__difference(GoalVars, NonLocalVars, LocalVars).

:- func union_of_direct_subgoal_locals(hlds_goal) = set(prog_var).

union_of_direct_subgoal_locals(Goal - _GoalInfo) =
	promise_only_solution((pred(UnionOfSubGoalLocals::out) is cc_multi :-
		set__init(EmptySet),
		unsorted_aggregate(direct_subgoal(Goal),
			union_subgoal_locals, EmptySet, UnionOfSubGoalLocals)
	)).

:- pred union_subgoal_locals(hlds_goal::in, set(prog_var)::in,
	set(prog_var)::out) is det.

union_subgoal_locals(SubGoal, UnionOfSubGoalLocals0, UnionOfSubGoalLocals) :-
	SubGoalLocals = goal_local_vars(SubGoal),
	set__union(UnionOfSubGoalLocals0, SubGoalLocals, UnionOfSubGoalLocals).

	% ml_gen_wrap_goal(OuterCodeModel, InnerCodeModel, Context,
	%		Statements0, Statements):
	%
	%	OuterCodeModel is the code model expected by the
	%	context in which a goal is called. InnerCodeModel
	%	is the code model which the goal actually has.
	%	This predicate converts the code generated for
	%	the goal using InnerCodeModel into code that uses
	%	the calling convention appropriate for OuterCodeModel.

	%
	% If the inner and outer code models are equal,
	% we don't need to do anything special.

ml_gen_wrap_goal(model_det, model_det, _, !Statements, !Info).
ml_gen_wrap_goal(model_semi, model_semi, _, !Statements, !Info).
ml_gen_wrap_goal(model_non, model_non, _, !Statements, !Info).

	% If the inner code model is more precise than the outer code
	% model, then we need to append some statements to convert
	% the calling convention for the inner code model to that of
	% the outer code model.

ml_gen_wrap_goal(model_semi, model_det, Context, !Statements, !Info) :-
	%
	% det goal in semidet context:
	%	<succeeded = Goal>
	% ===>
	%	<do Goal>
	%	succeeded = MR_TRUE
	%
	ml_gen_set_success(!.Info, const(true), Context, SetSuccessTrue),
	!:Statements = list__append(!.Statements, [SetSuccessTrue]).

ml_gen_wrap_goal(model_non, model_det, Context, !Statements, !Info) :-
	%
	% det goal in nondet context:
	%	<Goal && SUCCEED()>
	% ===>
	%	<do Goal>
	%	SUCCEED()
	%
	ml_gen_call_current_success_cont(Context, CallCont, !Info),
	!:Statements = list__append(!.Statements, [CallCont]).

ml_gen_wrap_goal(model_non, model_semi, Context, !Statements, !Info) :-
	%
	% semi goal in nondet context:
	%	<Goal && SUCCEED()>
	% ===>
	%	MR_bool succeeded;
	%
	%	<succeeded = Goal>
	%	if (succeeded) SUCCEED()
	%
	ml_gen_test_success(!.Info, Succeeded),
	ml_gen_call_current_success_cont(Context, CallCont, !Info),
	IfStmt = if_then_else(Succeeded, CallCont, no),
	IfStatement = mlds__statement(IfStmt, mlds__make_context(Context)),
	!:Statements = list__append(!.Statements, [IfStatement]).

	% If the inner code model is less precise than the outer code model,
	% then simplify.m is supposed to wrap the goal inside a `some'
	% to indicate that a commit is needed.

ml_gen_wrap_goal(model_det, model_semi, _, _, _, !Info) :-
	error("ml_gen_wrap_goal: code model mismatch -- semi in det").
ml_gen_wrap_goal(model_det, model_non, _, _, _, !Info) :-
	error("ml_gen_wrap_goal: code model mismatch -- nondet in det").
ml_gen_wrap_goal(model_semi, model_non, _, _, _, !Info) :-
	error("ml_gen_wrap_goal: code model mismatch -- nondet in semi").

	% Generate code for a commit.
	%
:- pred ml_gen_commit(hlds_goal::in, code_model::in, prog_context::in,
	mlds__defns::out, mlds__statements::out,
	ml_gen_info::in, ml_gen_info::out) is det.

ml_gen_commit(Goal, CodeModel, Context, Decls, Statements, !Info) :-
	Goal = _ - GoalInfo,
	goal_info_get_code_model(GoalInfo, GoalCodeModel),
	goal_info_get_context(GoalInfo, GoalContext),

	(
		GoalCodeModel = model_non,
		CodeModel = model_semi
	->

		%	model_non in semi context: (using try_commit/do_commit)
		%		<succeeded = Goal>
		% 	===>
		%		MR_bool succeeded;
		%	#ifdef NONDET_COPY_OUT
		%		<local var decls>
		%	#endif
		%	#ifdef PUT_COMMIT_IN_OWN_FUNC
		%	    /*
		%	    ** to avoid problems with setjmp() and non-volatile
		%	    ** local variables, we need to put the call to
		%	    ** setjmp() in its own nested function
		%	    */
		%	    void commit_func()
		%	    {
		%	#endif
		%		MR_COMMIT_TYPE ref;
		%
		%		void success() {
		%			MR_DO_COMMIT(ref);
		%		}
		%
		%		MR_TRY_COMMIT(ref, {
		%			<Goal && success()>
		%			succeeded = MR_FALSE;
		%		}, {
		%	#ifdef NONDET_COPY_OUT
		%			<copy local vars to output args>
		%	#endif
		%			succeeded = MR_TRUE;
		%		})
		%	#ifdef PUT_COMMIT_IN_OWN_FUNC
		%
		%	    commit_func();
		%	#endif

		ml_gen_maybe_make_locals_for_output_args(GoalInfo,
			LocalVarDecls, CopyLocalsToOutputArgs,
			OrigVarLvalMap, !Info),

		% generate the `success()' function
		ml_gen_new_func_label(no, SuccessFuncLabel,
			SuccessFuncLabelRval, !Info),
		/* push nesting level */
		MLDS_Context = mlds__make_context(Context),
		ml_gen_info_new_commit_label(CommitLabelNum, !Info),
		CommitRef = mlds__var_name(string__format("commit_%d",
			[i(CommitLabelNum)]), no),
		ml_gen_var_lval(!.Info, CommitRef, mlds__commit_type,
			CommitRefLval),
		CommitRefDecl = ml_gen_commit_var_decl(MLDS_Context,
			CommitRef),
		DoCommitStmt = do_commit(lval(CommitRefLval)),
		DoCommitStatement =
			mlds__statement(DoCommitStmt, MLDS_Context),
		/* pop nesting level */
		ml_gen_nondet_label_func(!.Info, SuccessFuncLabel, Context,
			DoCommitStatement, SuccessFunc),

		ml_get_env_ptr(!.Info, EnvPtrRval),
		SuccessCont = success_cont(SuccessFuncLabelRval,
			EnvPtrRval, [], []),
		ml_gen_info_push_success_cont(SuccessCont, !Info),
		ml_gen_goal(model_non, Goal, GoalDecls, GoalStatements, !Info),
		% hoist any static constant declarations for Goal
		% out to the top level
		list__filter(ml_decl_is_static_const, GoalDecls,
			GoalStaticDecls, GoalOtherDecls),
		GoalStatement = ml_gen_block(GoalOtherDecls,
			GoalStatements, GoalContext),
		ml_gen_info_pop_success_cont(!Info),
		ml_gen_set_success(!.Info, const(false), Context,
			SetSuccessFalse),
		ml_gen_set_success(!.Info, const(true), Context,
			SetSuccessTrue),
		TryCommitStmt = try_commit(CommitRefLval,
			ml_gen_block([], [GoalStatement, SetSuccessFalse],
				Context),
			ml_gen_block([], list__append(CopyLocalsToOutputArgs,
				[SetSuccessTrue]), Context)),
		TryCommitStatement = mlds__statement(TryCommitStmt,
			MLDS_Context),
		CommitFuncLocalDecls = [CommitRefDecl, SuccessFunc |
			GoalStaticDecls],
		maybe_put_commit_in_own_func(CommitFuncLocalDecls,
			[TryCommitStatement], Context,
			CommitFuncDecls, Statements, !Info),
		Decls = LocalVarDecls ++ CommitFuncDecls,

		ml_gen_info_set_var_lvals(OrigVarLvalMap, !Info)

	;
		GoalCodeModel = model_non,
		CodeModel = model_det
	->

		%	model_non in det context: (using try_commit/do_commit)
		%		<do Goal>
		%	===>
		%	#ifdef NONDET_COPY_OUT
		%		<local var decls>
		%	#endif
		%	#ifdef PUT_COMMIT_IN_NESTED_FUNC
		%	    /*
		%	    ** to avoid problems with setjmp() and non-volatile
		%	    ** local variables, we need to put the call to
		%	    ** setjmp() in its own nested functions
		%	    */
		%	    void commit_func()
		%	    {
		%       #endif
		%		MR_COMMIT_TYPE ref;
		%		void success() {
		%			MR_DO_COMMIT(ref);
		%		}
		%		MR_TRY_COMMIT(ref, {
		%			<Goal && success()>
		%		}, {
		%	#ifdef NONDET_COPY_OUT
		%			<copy local vars to output args>
		%	#endif
		%		})
		%	#ifdef PUT_COMMIT_IN_NESTED_FUNC
		%
		%	    commit_func();
		%       #endif

		ml_gen_maybe_make_locals_for_output_args(GoalInfo,
			LocalVarDecls, CopyLocalsToOutputArgs,
			OrigVarLvalMap, !Info),

		% generate the `success()' function
		ml_gen_new_func_label(no,
			SuccessFuncLabel, SuccessFuncLabelRval, !Info),
		/* push nesting level */
		MLDS_Context = mlds__make_context(Context),
		ml_gen_info_new_commit_label(CommitLabelNum, !Info),
		CommitRef = mlds__var_name(
			string__format("commit_%d", [i(CommitLabelNum)]),
			no),
		ml_gen_var_lval(!.Info, CommitRef, mlds__commit_type,
			CommitRefLval),
		CommitRefDecl = ml_gen_commit_var_decl(MLDS_Context,
			CommitRef),
		DoCommitStmt = do_commit(lval(CommitRefLval)),
		DoCommitStatement = mlds__statement(DoCommitStmt,
			MLDS_Context),
		/* pop nesting level */
		ml_gen_nondet_label_func(!.Info, SuccessFuncLabel, Context,
			DoCommitStatement, SuccessFunc),

		ml_get_env_ptr(!.Info, EnvPtrRval),
		SuccessCont = success_cont(SuccessFuncLabelRval,
			EnvPtrRval, [], []),
		ml_gen_info_push_success_cont(SuccessCont, !Info),
		ml_gen_goal(model_non, Goal, GoalDecls, GoalStatements, !Info),
		% hoist any static constant declarations for Goal
		% out to the top level
		list__filter(ml_decl_is_static_const, GoalDecls,
			GoalStaticDecls, GoalOtherDecls),
		GoalStatement = ml_gen_block(GoalOtherDecls,
			GoalStatements, GoalContext),
		ml_gen_info_pop_success_cont(!Info),

		TryCommitStmt = try_commit(CommitRefLval, GoalStatement,
			ml_gen_block([], CopyLocalsToOutputArgs, Context)),
		TryCommitStatement = mlds__statement(TryCommitStmt,
			MLDS_Context),
		CommitFuncLocalDecls = [CommitRefDecl, SuccessFunc |
			GoalStaticDecls],
		maybe_put_commit_in_own_func(CommitFuncLocalDecls,
			[TryCommitStatement], Context,
			CommitFuncDecls, Statements, !Info),
		Decls = LocalVarDecls ++ CommitFuncDecls,
		ml_gen_info_set_var_lvals(OrigVarLvalMap, !Info)
	;
		% no commit required
		ml_gen_goal(CodeModel, Goal, Decls, Statements, !Info)
	).

	% maybe_put_commit_in_own_func(Defns0, Stmts0, Defns, Stmts):
	% if the --put-commit-in-own-func option is set, put
	% the commit in its own function. This is needed for
	% the high-level C back-end, to handle problems with
	% setjmp()/longjmp() clobbering non-volatile local variables.
	%
	% Detailed explanation:
	%
	% For the high-level C back-end, we implement commits using
	% setjmp()/longjmp(). Unfortunately for us, ANSI/ISO C says
	% that longjmp() is allowed to clobber the values of any
	% non-volatile local variables in the function that called
	% setjmp() which have been modified between the setjmp()
	% and the longjmp().
	%
	% To avoid this, whenever we generate a commit, we put
	% it in its own nested function, with the local variables
	% (e.g. `succeeded', plus any outputs from the goal that
	% we're committing over) remaining in the containing function.
	% This ensures that none of the variables which get modified
	% between the setjmp() and the longjmp() and which get
	% referenced after the longjmp() are local variables in the
	% function containing the setjmp().
	%
	% [The obvious alternative of declaring the local variables in
	% the function containing setjmp() as `volatile' doesn't work,
	% since the assignments to those output variables may be deep
	% in some function called indirectly from the goal that we're
	% committing across, and assigning to a volatile-qualified
	% variable via a non-volatile pointer is undefined behaviour.
	% The only way to make it work would be to be to declare
	% *every* output argument that we pass by reference as
	% `volatile T *'. But that would impose distributed fat and
	% would make interoperability difficult.]
	%
:- pred maybe_put_commit_in_own_func(mlds__defns::in, mlds__statements::in,
	prog_context::in, mlds__defns::out, mlds__statements::out,
	ml_gen_info::in, ml_gen_info::out) is det.

maybe_put_commit_in_own_func(CommitFuncLocalDecls, TryCommitStatements,
		Context, Decls, Statements, !Info) :-
	ml_gen_info_put_commit_in_own_func(!.Info, PutCommitInOwnFunc),
	( PutCommitInOwnFunc = yes ->
		%
		% Generate the `void commit_func() { ... }' wrapper
		% around the main body that we generated above
		%
		ml_gen_new_func_label(no, CommitFuncLabel,
			CommitFuncLabelRval, !Info),
		/* push nesting level */
		CommitFuncBody = ml_gen_block(CommitFuncLocalDecls,
			TryCommitStatements, Context),
		/* pop nesting level */
		ml_gen_nondet_label_func(!.Info, CommitFuncLabel, Context,
			CommitFuncBody, CommitFunc),
		%
		% Generate the call to `commit_func();'
		%
		ml_gen_info_use_gcc_nested_functions(!.Info, UseNestedFuncs),
		( UseNestedFuncs = yes ->
			ArgRvals = [],
			ArgTypes = []
		;
			ml_get_env_ptr(!.Info, EnvPtrRval),
			ArgRvals = [EnvPtrRval],
			ArgTypes = [mlds__generic_env_ptr_type]
		),
		RetTypes = [],
		Signature = mlds__func_signature(ArgTypes, RetTypes),
		CallKind = ordinary_call,
		CallStmt = call(Signature, CommitFuncLabelRval, no,
			ArgRvals, [], CallKind),
		CallStatement = mlds__statement(CallStmt,
			mlds__make_context(Context)),
		% Package it all up
		Statements = [CallStatement],
		Decls = [CommitFunc]
	;
		Statements = TryCommitStatements,
		Decls = CommitFuncLocalDecls
	).

	%
	% In commits, you have model_non code called from a model_det or
	% model_semi context. With --nondet-copy-out, when generating code
	% for commits, if the context is a model_det or model_semi procedure
	% with output arguments passed by reference, then we need to introduce
	% local variables corresponding to those output arguments,
	% and at the end of the commit we'll copy the local variables into
	% the output arguments.
	%
:- pred ml_gen_maybe_make_locals_for_output_args(hlds_goal_info::in,
	mlds__defns::out, mlds__statements::out,
	map(prog_var, mlds__lval)::out,
	ml_gen_info::in, ml_gen_info::out) is det.

ml_gen_maybe_make_locals_for_output_args(GoalInfo, LocalVarDecls,
		CopyLocalsToOutputArgs, OrigVarLvalMap, !Info) :-
	ml_gen_info_get_var_lvals(!.Info, OrigVarLvalMap),
	ml_gen_info_get_globals(!.Info, Globals),
	globals__lookup_bool_option(Globals, nondet_copy_out,
		NondetCopyOut),
	( NondetCopyOut = yes ->
		goal_info_get_context(GoalInfo, Context),
		goal_info_get_nonlocals(GoalInfo, NonLocals),
		ml_gen_info_get_byref_output_vars(!.Info, ByRefOutputVars),
		VarsToCopy = set__intersect(set__list_to_set(ByRefOutputVars),
			NonLocals),
		ml_gen_make_locals_for_output_args(
			set__to_sorted_list(VarsToCopy), Context,
			LocalVarDecls, CopyLocalsToOutputArgs, !Info)
	;
		LocalVarDecls = [],
		CopyLocalsToOutputArgs = []
	).

:- pred ml_gen_make_locals_for_output_args(list(prog_var)::in, prog_context::in,
	mlds__defns::out, mlds__statements::out,
	ml_gen_info::in, ml_gen_info::out) is det.

ml_gen_make_locals_for_output_args([], _, [], [], !Info).
ml_gen_make_locals_for_output_args([Var | Vars], Context,
		LocalDefns, Assigns, !Info) :-
	ml_gen_make_locals_for_output_args(Vars, Context,
		LocalDefns0, Assigns0, !Info),
	ml_variable_type(!.Info, Var, Type),
	( type_util__is_dummy_argument_type(Type) ->
		LocalDefns = LocalDefns0,
		Assigns = Assigns0
	;
		ml_gen_make_local_for_output_arg(Var, Type, Context,
			LocalDefn, Assign, !Info),
		LocalDefns = [LocalDefn | LocalDefns0],
		Assigns = [Assign | Assigns0]
	).

:- pred ml_gen_make_local_for_output_arg(prog_var::in, prog_type::in,
	prog_context::in, mlds__defn::out, mlds__statement::out,
	ml_gen_info::in, ml_gen_info::out) is det.

ml_gen_make_local_for_output_arg(OutputVar, Type, Context,
		LocalVarDefn, Assign, !Info) :-
	%
	% Look up the name of the output variable
	%
	ml_gen_info_get_varset(!.Info, VarSet),
	OutputVarName = ml_gen_var_name(VarSet, OutputVar),

	%
	% Generate a declaration for a corresponding local variable.
	OutputVarName = mlds__var_name(OutputVarNameStr, MaybeNum),
	LocalVarName = mlds__var_name(
		string__append("local_", OutputVarNameStr), MaybeNum),
	ml_gen_type(!.Info, Type, MLDS_Type),
	ml_gen_maybe_gc_trace_code(LocalVarName, Type, Context, GC_TraceCode,
		!Info),
	LocalVarDefn = ml_gen_mlds_var_decl(var(LocalVarName), MLDS_Type,
		GC_TraceCode, mlds__make_context(Context)),

	%
	% Generate code to assign from the local var to the output var
	%
	ml_gen_var(!.Info, OutputVar, OutputVarLval),
	ml_gen_var_lval(!.Info, LocalVarName, MLDS_Type, LocalVarLval),
	Assign = ml_gen_assign(OutputVarLval, lval(LocalVarLval), Context),

	%
	% Update the lval for this variable so that any references to it
	% inside the commit refer to the local variable rather than
	% to the output argument.
	% (Note that we reset all the var lvals at the end of the commit.)
	%
	ml_gen_info_set_var_lval(OutputVar, LocalVarLval, !Info).

	% Generate the declaration for the `commit' variable.
	%
:- func ml_gen_commit_var_decl(mlds__context, mlds__var_name) = mlds__defn.

ml_gen_commit_var_decl(Context, VarName) =
	ml_gen_mlds_var_decl(var(VarName), mlds__commit_type, no, Context).

	% Generate MLDS code for the different kinds of HLDS goals.
	%
:- pred ml_gen_goal_expr(hlds_goal_expr::in, code_model::in, prog_context::in,
	mlds__defns::out, mlds__statements::out,
	ml_gen_info::in, ml_gen_info::out) is det.

ml_gen_goal_expr(switch(Var, CanFail, CasesList), CodeModel, Context,
		Decls, Statements, !Info) :-
	ml_gen_switch(Var, CanFail, CasesList, CodeModel, Context,
		Decls, Statements, !Info).

ml_gen_goal_expr(some(_Vars, _CanRemove, Goal), CodeModel, Context,
		Decls, Statements, !Info) :-
	ml_gen_commit(Goal, CodeModel, Context, Decls, Statements, !Info).

ml_gen_goal_expr(if_then_else(_Vars, Cond, Then, Else),
		CodeModel, Context, Decls, Statements, !Info) :-
	ml_gen_ite(CodeModel, Cond, Then, Else, Context,
		Decls, Statements, !Info).

ml_gen_goal_expr(not(Goal), CodeModel, Context,
		Decls, Statements, !Info) :-
	ml_gen_negation(Goal, CodeModel, Context, Decls, Statements, !Info).

ml_gen_goal_expr(conj(Goals), CodeModel, Context,
		Decls, Statements, !Info) :-
	ml_gen_conj(Goals, CodeModel, Context, Decls, Statements, !Info).

ml_gen_goal_expr(disj(Goals), CodeModel, Context,
		Decls, Statements, !Info) :-
	ml_gen_disj(Goals, CodeModel, Context, Decls, Statements, !Info).

ml_gen_goal_expr(par_conj(Goals), CodeModel, Context,
		Decls, Statements, !Info) :-
	%
	% XXX currently we treat parallel conjunction the same as
	% sequential conjunction -- parallelism is not yet implemented
	%
	ml_gen_conj(Goals, CodeModel, Context, Decls, Statements, !Info).

ml_gen_goal_expr(generic_call(GenericCall, Vars, Modes, Detism), CodeModel,
		Context, Decls, Statements, !Info) :-
	determinism_to_code_model(Detism, CallCodeModel),
	require(unify(CodeModel, CallCodeModel),
		"ml_gen_generic_call: code model mismatch"),
	ml_gen_generic_call(GenericCall, Vars, Modes, Detism, Context,
		Decls, Statements, !Info).

ml_gen_goal_expr(call(PredId, ProcId, ArgVars, BuiltinState, _, _),
		CodeModel, Context, Decls, Statements, !Info) :-
	( BuiltinState = not_builtin ->
		ml_gen_var_list(!.Info, ArgVars, ArgLvals),
		ml_gen_info_get_varset(!.Info, VarSet),
		ArgNames = ml_gen_var_names(VarSet, ArgVars),
		ml_variable_types(!.Info, ArgVars, ActualArgTypes),
		ml_gen_call(PredId, ProcId, ArgNames, ArgLvals, ActualArgTypes,
			CodeModel, Context, no, Decls, Statements, !Info)
	;
		ml_gen_builtin(PredId, ProcId, ArgVars, CodeModel, Context,
			Decls, Statements, !Info)
	).

ml_gen_goal_expr(unify(_LHS, _RHS, _Mode, Unification, _UnifyContext),
		CodeModel, Context, Decls, Statements, !Info) :-
	ml_gen_unification(Unification, CodeModel, Context,
		Decls, Statements, !Info).

ml_gen_goal_expr(foreign_proc(Attributes, PredId, ProcId, Args, ExtraArgs,
		PragmaImpl), CodeModel, OuterContext, Decls, Statements,
		!Info) :-
	(
		PragmaImpl = ordinary(ForeignCode, MaybeContext),
		(
			MaybeContext = yes(Context)
		;
			MaybeContext = no,
			Context = OuterContext
		),
		ml_gen_ordinary_pragma_foreign_proc(CodeModel, Attributes,
			PredId, ProcId, Args, ExtraArgs, ForeignCode,
			Context, Decls, Statements, !Info)
	;
		PragmaImpl = nondet(LocalVarsDecls, LocalVarsContext,
			FirstCode, FirstContext, LaterCode, LaterContext,
			_Treatment, SharedCode, SharedContext),
		require(unify(ExtraArgs, []),
			"ml_gen_goal_expr: extra args"),
		ml_gen_nondet_pragma_foreign_proc(CodeModel, Attributes,
			PredId, ProcId, Args, OuterContext,
			LocalVarsDecls, LocalVarsContext,
			FirstCode, FirstContext, LaterCode, LaterContext,
			SharedCode, SharedContext, Decls, Statements, !Info)
	;
		PragmaImpl = import(Name, HandleReturn, Vars, _Context),
		require(unify(ExtraArgs, []),
			"ml_gen_goal_expr: extra args"),
		ForeignCode = string__append_list([HandleReturn, " ",
			Name, "(", Vars, ");"]),
		ml_gen_ordinary_pragma_foreign_proc(CodeModel, Attributes,
			PredId, ProcId, Args, ExtraArgs, ForeignCode,
			OuterContext, Decls, Statements, !Info)
	).

ml_gen_goal_expr(shorthand(_), _, _, _, _, !Info) :-
	% these should have been expanded out by now
	error("ml_gen_goal_expr: unexpected shorthand").

% :- module ml_foreign.
%
% ml_foreign creates MLDS code to execute foreign language code.
%
%

:- pred ml_gen_nondet_pragma_foreign_proc(code_model::in,
	pragma_foreign_proc_attributes::in,
	pred_id::in, proc_id::in, list(foreign_arg)::in,
	prog_context::in, string::in, maybe(prog_context)::in, string::in,
	maybe(prog_context)::in, string::in, maybe(prog_context)::in,
	string::in, maybe(prog_context)::in,
	mlds__defns::out, mlds__statements::out,
	ml_gen_info::in, ml_gen_info::out) is det.

	% For model_non pragma c_code,
	% we generate code of the following form:
	%
	%	#define MR_PROC_LABEL <procedure name>
	% 	<declaration of locals needed for boxing/unboxing>
	%	{
	% 		<declaration of one local variable for each arg>
	%		struct {
	%			<user's local_vars decls>
	%		} MR_locals;
	%		MR_bool MR_done = MR_FALSE;
	%		MR_bool MR_succeeded = MR_FALSE;
	%
	%		#define FAIL		(MR_done = MR_TRUE)
	%		#define SUCCEED		(MR_succeeded = MR_TRUE)
	%		#define SUCCEED_LAST	(MR_succeeded = MR_TRUE, \
	%					 MR_done = MR_TRUE)
	%		#define LOCALS		(&MR_locals)
	%
	%		<assign input args>
	%		<obtain global lock>
	%		<user's first_code C code>
	%		while (true) {
	%			<user's shared_code C code>
	%			<release global lock>
	%			if (MR_succeeded) {
	%				<assign output args>
	% 				<boxing/unboxing of outputs>
	%				CONT();
	%			}
	%			if (MR_done) break;
	%			MR_succeeded = MR_FALSE;
	%			<obtain global lock>
	%			<user's later_code C code>
	%		}
	%
	%		#undef FAIL
	%		#undef SUCCEED
	%		#undef SUCCEED_LAST
	%		#undef LOCALS
	%	}
	%	#undef MR_PROC_LABEL
	%
	% We insert a #define for MR_PROC_LABEL, so that the C code in
	% the Mercury standard library that allocates memory manually
	% can use MR_PROC_LABEL as the procname argument to
	% incr_hp_msg(), for memory profiling. Hard-coding the procname
	% argument in the C code would be wrong, since it wouldn't
	% handle the case where the original pragma c_code procedure
	% gets inlined and optimized away. Of course we also need to
	% #undef it afterwards.
	%
ml_gen_nondet_pragma_foreign_proc(CodeModel, Attributes, PredId, _ProcId,
		Args, Context, LocalVarsDecls, LocalVarsContext,
		FirstCode, FirstContext, LaterCode, LaterContext,
		SharedCode, SharedContext, Decls, Statements, !Info) :-

	Lang = foreign_language(Attributes),
	( Lang = csharp ->
		sorry(this_file, "nondet pragma foreign_proc for C#")
	;
		true
	),
	%
	% Generate <declaration of one local variable for each arg>
	%
	ml_gen_pragma_c_decls(!.Info, Lang, Args, ArgDeclsList),

	%
	% Generate definitions of the FAIL, SUCCEED, SUCCEED_LAST,
	% and LOCALS macros
	%
	string__append_list([
"	#define FAIL		(MR_done = MR_TRUE)\n",
"	#define SUCCEED		(MR_succeeded = MR_TRUE)\n",
"	#define SUCCEED_LAST	(MR_succeeded = MR_TRUE, MR_done = MR_TRUE)\n",
"	#define LOCALS		(&MR_locals)\n"
		], HashDefines),
	string__append_list([
			"	#undef	FAIL\n",
			"	#undef	SUCCEED\n",
			"	#undef	SUCCEED_LAST\n",
			"	#undef	LOCALS\n"
		], HashUndefs),

	%
	% Generate code to set the values of the input variables.
	%
	ml_gen_pragma_c_input_arg_list(Lang, Args, AssignInputsList, !Info),

	%
	% Generate code to assign the values of the output variables.
	%
	ml_gen_pragma_c_output_arg_list(Lang, Args, Context,
		AssignOutputsList, ConvDecls, ConvStatements, !Info),

	%
	% Generate code fragments to obtain and release the global lock
	%
	ThreadSafe = thread_safe(Attributes),
	ml_gen_obtain_release_global_lock(!.Info, ThreadSafe, PredId,
		ObtainLock, ReleaseLock),

	%
	% Generate the MR_PROC_LABEL #define
	%
	ml_gen_hash_define_mr_proc_label(!.Info, HashDefine),

	%
	% Put it all together
	%
	Starting_C_Code = list__condense([
		[raw_target_code("{\n", [])],
		HashDefine,
		ArgDeclsList,
		[raw_target_code("\tstruct {\n", []),
		user_target_code(LocalVarsDecls, LocalVarsContext, []),
		raw_target_code("\n", []),
		raw_target_code("\t} MR_locals;\n", []),
		raw_target_code("\tMR_bool MR_succeeded = MR_FALSE;\n", []),
		raw_target_code("\tMR_bool MR_done = MR_FALSE;\n", []),
		raw_target_code("\n", []),
		raw_target_code(HashDefines, []),
		raw_target_code("\n", [])],
		AssignInputsList,
		[raw_target_code(ObtainLock, []),
		raw_target_code("\t{\n", []),
		user_target_code(FirstCode, FirstContext, []),
		raw_target_code("\n\t;}\n", []),
		raw_target_code("\twhile (1) {\n", []),
		raw_target_code("\t\t{\n", []),
		user_target_code(SharedCode, SharedContext, []),
		raw_target_code("\n\t\t;}\n", []),
		raw_target_code("#undef MR_PROC_LABEL\n", []),
		raw_target_code(ReleaseLock, []),
		raw_target_code("\t\tif (MR_succeeded) {\n", [])],
		AssignOutputsList
	]),
	ml_gen_info_get_module_info(!.Info, ModuleInfo),
	module_info_globals(ModuleInfo, Globals),
	globals__get_target(Globals, Target),
	( CodeModel = model_non ->

		% For IL code, we can't call continutations because there is
		% no syntax for calling managed function pointers in
		% managed C++. Instead we have to call back into IL and make
		% the continuation call in IL. This is called an "indirect"
		% success continuation call.

		( Target = il ->
			ml_gen_call_current_success_cont_indirectly(Context,
				CallCont, !Info)
		;
			ml_gen_call_current_success_cont(Context, CallCont,
				!Info)
		)
	;
		error("ml_gen_nondet_pragma_c_code: unexpected code model")
	),
	Ending_C_Code = [
		raw_target_code("\t\t}\n", []),
		raw_target_code("\t\tif (MR_done) break;\n", []),
		raw_target_code("\tMR_succeeded = MR_FALSE;\n", []),
		raw_target_code(ObtainLock, []),
		raw_target_code("\t\t{\n", []),
		user_target_code(LaterCode, LaterContext, []),
		raw_target_code("\n\t\t;}\n", []),
		raw_target_code("\t}\n", []),
		raw_target_code("\n", []),
		raw_target_code(HashUndefs, []),
		raw_target_code("}\n", [])
	],
	Starting_C_Code_Stmt = inline_target_code(lang_C, Starting_C_Code),
	Starting_C_Code_Statement = mlds__statement(
		atomic(Starting_C_Code_Stmt), mlds__make_context(Context)),
	Ending_C_Code_Stmt = inline_target_code(lang_C, Ending_C_Code),
	Ending_C_Code_Statement = mlds__statement(
		atomic(Ending_C_Code_Stmt), mlds__make_context(Context)),
	Statements = list__condense([
		[Starting_C_Code_Statement],
		ConvStatements,
		[CallCont,
		Ending_C_Code_Statement]
	]),
	Decls = ConvDecls.

:- pred ml_gen_ordinary_pragma_foreign_proc(code_model::in,
	pragma_foreign_proc_attributes::in, pred_id::in, proc_id::in,
	list(foreign_arg)::in, list(foreign_arg)::in, string::in,
	prog_context::in, mlds__defns::out, mlds__statements::out,
	ml_gen_info::in, ml_gen_info::out) is det.

ml_gen_ordinary_pragma_foreign_proc(CodeModel, Attributes, PredId, ProcId,
		Args, ExtraArgs, Foreign_Code, Context, Decls, Statements,
		!Info) :-
	Lang = foreign_language(Attributes),
	(
		CodeModel = model_det,
		OrdinaryKind = kind_det
	;
		CodeModel = model_semi,
		ml_gen_info_get_module_info(!.Info, ModuleInfo),
		module_info_pred_proc_info(ModuleInfo, PredId, ProcId,
			_PredInfo, ProcInfo),
		proc_info_interface_determinism(ProcInfo, Detism),
		determinism_components(Detism, _, MaxSoln),
		( MaxSoln = at_most_zero ->
			OrdinaryKind = kind_failure
		;
			OrdinaryKind = kind_semi
		)
	;
		CodeModel = model_non,
		OrdinaryDespiteDetism = ordinary_despite_detism(Attributes),
		(
			OrdinaryDespiteDetism = no,
			error("ml_gen_ordinary_pragma_foreign_proc: " ++
				"unexpected code model")
		;
			OrdinaryDespiteDetism = yes,
			OrdinaryKind = kind_semi
		)
	),
	(
		Lang = c,
		ml_gen_ordinary_pragma_c_proc(OrdinaryKind, Attributes,
			PredId, ProcId, Args, ExtraArgs,
			Foreign_Code, Context, Decls, Statements, !Info)
	;
		Lang = managed_cplusplus,
		ml_gen_ordinary_pragma_managed_proc(OrdinaryKind, Attributes,
			PredId, ProcId, Args, ExtraArgs,
			Foreign_Code, Context, Decls, Statements, !Info)
	;
		Lang = csharp,
		ml_gen_ordinary_pragma_managed_proc(OrdinaryKind, Attributes,
			PredId, ProcId, Args, ExtraArgs,
			Foreign_Code, Context, Decls, Statements, !Info)
	;
		Lang = il,
		% XXX should pass OrdinaryKind
		ml_gen_ordinary_pragma_il_proc(CodeModel, Attributes,
			PredId, ProcId, Args, ExtraArgs,
			Foreign_Code, Context, Decls, Statements, !Info)
	;
		Lang = java,
		% XXX should pass OrdinaryKind
		ml_gen_ordinary_pragma_java_proc(CodeModel, Attributes,
			PredId, ProcId, Args, ExtraArgs,
			Foreign_Code, Context, Decls, Statements, !Info)
	).

:- pred ml_gen_ordinary_pragma_java_proc(code_model::in,
	pragma_foreign_proc_attributes::in, pred_id::in, proc_id::in,
	list(foreign_arg)::in, list(foreign_arg)::in, string::in,
	prog_context::in, mlds__defns::out, mlds__statements::out,
	ml_gen_info::in, ml_gen_info::out) is det.

ml_gen_ordinary_pragma_java_proc(_CodeModel, Attributes, _PredId, _ProcId,
		Args, ExtraArgs, JavaCode, Context, Decls, Statements,
		!Info) :-

	Lang = foreign_language(Attributes),
	%
	% Generate <declaration of one local variable for each arg>
	%
	ml_gen_pragma_c_decls(!.Info, Lang, Args, ArgDeclsList),
	require(unify(ExtraArgs, []),
		"ml_gen_ordinary_pragma_java_proc: extra args"),
	%
	% Generate code to set the values of the input variables.
	%
	ml_gen_pragma_c_input_arg_list(Lang, Args, AssignInputsList, !Info),
	%
	% Generate MLDS statements to assign the values of the output
	% variables.
	%
	ml_gen_pragma_java_output_arg_list(Lang, Args, Context,
		AssignOutputsList, ConvDecls, ConvStatements, !Info),
	%
	% Put it all together
	% XXX FIXME need to handle model_semi code here,
	% i.e. provide some equivalent to SUCCESS_INDICATOR.
	%
	Java_Code = list__condense([
		ArgDeclsList,
		AssignInputsList,
		[user_target_code(JavaCode, yes(Context), [])]
	]),
	Java_Code_Stmt = inline_target_code(lang_java, Java_Code),
	Java_Code_Statement = mlds__statement(
		atomic(Java_Code_Stmt),
		mlds__make_context(Context)),
	Statements = list__condense([
		[Java_Code_Statement],
		AssignOutputsList,
		ConvStatements
		]),
	Decls = ConvDecls.

:- type ordinary_pragma_kind
	--->	kind_det
	;	kind_semi
	;	kind_failure.

	% For ordinary (not model_non) pragma foreign_code in C# or MC++,
	% we generate a call to an out-of-line procedure that contains
	% the user's code.

:- pred ml_gen_ordinary_pragma_managed_proc(ordinary_pragma_kind::in,
	pragma_foreign_proc_attributes::in, pred_id::in, proc_id::in,
	list(foreign_arg)::in, list(foreign_arg)::in, string::in,
	prog_context::in, mlds__defns::out, mlds__statements::out,
	ml_gen_info::in, ml_gen_info::out) is det.

ml_gen_ordinary_pragma_managed_proc(OrdinaryKind, Attributes, _PredId, _ProcId,
		Args, ExtraArgs, ForeignCode, Context, Decls, Statements,
		!Info) :-

	ml_gen_outline_args(Args, OutlineArgs, !Info),
	require(unify(ExtraArgs, []),
		"ml_gen_ordinary_pragma_managed_proc: extra args"),

	ForeignLang = foreign_language(Attributes),
	MLDSContext = mlds__make_context(Context),
	ml_gen_info_get_value_output_vars(!.Info, OutputVars),
	ml_gen_var_list(!.Info, OutputVars, OutputVarLvals),
	OutlineStmt = outline_foreign_proc(ForeignLang, OutlineArgs,
		OutputVarLvals, ForeignCode),

	ml_gen_info_get_module_info(!.Info, ModuleInfo),
	module_info_name(ModuleInfo, ModuleName),
	MLDSModuleName = mercury_module_name_to_mlds(ModuleName),

	ml_success_lval(!.Info, SucceededLval),
	(
		OrdinaryKind = kind_det,
		SuccessVarLocals = [],
		SuccessIndicatorStatements = []
	;
		OrdinaryKind = kind_semi,
		% If the code is semidet, we should copy SUCCESS_INDICATOR
		% out into "success".
		SuccessIndicatorVarName = var_name("SUCCESS_INDICATOR", no),
		SuccessIndicatorDecl = ml_gen_mlds_var_decl(
			var(SuccessIndicatorVarName),
			mlds__native_bool_type,
			no_initializer, no, MLDSContext),
		SuccessIndicatorLval = var(qual(MLDSModuleName, module_qual,
			SuccessIndicatorVarName), mlds__native_bool_type),
		SuccessIndicatorStatement = ml_gen_assign(SucceededLval,
			lval(SuccessIndicatorLval), Context),
		SuccessVarLocals = [SuccessIndicatorDecl],
		SuccessIndicatorStatements = [SuccessIndicatorStatement]
	;
		OrdinaryKind = kind_failure,
		error("ml_gen_ordinary_pragma_managed_proc: " ++
			"kind_failure not yet implemented")
	),

	Statements = [
		mlds__statement(atomic(OutlineStmt), MLDSContext) |
		SuccessIndicatorStatements
		],
	Decls = SuccessVarLocals.

:- pred ml_gen_outline_args(list(foreign_arg)::in, list(outline_arg)::out,
	ml_gen_info::in, ml_gen_info::out) is det.

ml_gen_outline_args([], [], !Info).
ml_gen_outline_args([foreign_arg(Var, MaybeVarMode, OrigType) | Args],
		[OutlineArg | OutlineArgs], !Info) :-
	ml_gen_outline_args(Args, OutlineArgs, !Info),
	ml_gen_info_get_module_info(!.Info, ModuleInfo),
	ml_gen_var(!.Info, Var, VarLval),
	ml_gen_type(!.Info, OrigType, MldsType),
	(
		MaybeVarMode = yes(ArgName - Mode),
		\+ type_util__is_dummy_argument_type(OrigType),
		\+ var_is_singleton(ArgName)
	->
		mode_to_arg_mode(ModuleInfo, Mode, OrigType, ArgMode),
		( ArgMode = top_in,
			OutlineArg = in(MldsType, ArgName, lval(VarLval))
		; ArgMode = top_out,
			OutlineArg = out(MldsType, ArgName, VarLval)
		; ArgMode = top_unused,
			OutlineArg = unused
		)
	;
		OutlineArg = unused
	).

:- pred ml_gen_ordinary_pragma_il_proc(code_model::in,
	pragma_foreign_proc_attributes::in, pred_id::in, proc_id::in,
	list(foreign_arg)::in, list(foreign_arg)::in, string::in,
	prog_context::in, mlds__defns::out, mlds__statements::out,
	ml_gen_info::in, ml_gen_info::out) is det.

ml_gen_ordinary_pragma_il_proc(_CodeModel, Attributes, PredId, ProcId,
		Args, ExtraArgs, ForeignCode, Context, Decls, Statements,
		!Info) :-

	require(unify(ExtraArgs, []),
		"ml_gen_ordinary_pragma_managed_proc: extra args"),

	% XXX FIXME need to handle model_semi code here,
	% i.e. provide some equivalent to SUCCESS_INDICATOR.

	% XXX FIXME do we handle top_unused mode correctly?

	MLDSContext = mlds__make_context(Context),

	ml_gen_info_get_module_info(!.Info, ModuleInfo),
	module_info_pred_proc_info(ModuleInfo, PredId, ProcId,
		_PredInfo, ProcInfo),
	proc_info_varset(ProcInfo, VarSet),
%	proc_info_vartypes(ProcInfo, VarTypes),
	% note that for headvars we must use the types from
	% the procedure interface, not from the procedure body
	ml_gen_info_get_byref_output_vars(!.Info, ByRefOutputVars),
	ml_gen_info_get_value_output_vars(!.Info, CopiedOutputVars),
	module_info_name(ModuleInfo, ModuleName),
	MLDSModuleName = mercury_module_name_to_mlds(ModuleName),

	% XXX in the code to marshall parameters, fjh says:
	% We need to handle the case where the types in the procedure interface
	% are polymorphic, but the types of the vars in the `foreign_proc' HLDS
	% goal are concrete instances of those types, which can happen when the
	% procedure is inlined or specialized. The assignment that you
	% generate here with ml_gen_assign won't be type-correct. In general
	% you may need to box/unbox the arguments.

	build_arg_map(Args, map__init, ArgMap),

		% Generate statements to assign by-ref output arguments
	list__filter_map(ml_gen_pragma_il_proc_assign_output(ModuleInfo,
			MLDSModuleName, ArgMap, VarSet, Context, yes),
		ByRefOutputVars, ByRefAssignStatements),

		% Generate statements to assign copied output arguments
	list__filter_map(ml_gen_pragma_il_proc_assign_output(ModuleInfo,
			MLDSModuleName, ArgMap, VarSet, Context, no),
		CopiedOutputVars, CopiedOutputStatements),

	ArgVars = list__map(foreign_arg_var, Args),
		% Generate declarations for all the variables, and
		% initializers for input variables.
	list__map(ml_gen_pragma_il_proc_var_decl_defn(ModuleInfo,
			MLDSModuleName, ArgMap, VarSet, MLDSContext,
			ByRefOutputVars, CopiedOutputVars),
		ArgVars, VarLocals),

	OutlineStmt = inline_target_code(lang_il, [
		user_target_code(ForeignCode, yes(Context),
			get_target_code_attributes(il,
				Attributes ^ extra_attributes))
		]),

	ILCodeFragment = mlds__statement(atomic(OutlineStmt), MLDSContext),
	Statements = [statement(block(VarLocals,
		[ILCodeFragment] ++ ByRefAssignStatements
			++ CopiedOutputStatements),
		mlds__make_context(Context))],
	Decls = [].

:- pred build_arg_map(list(foreign_arg)::in, map(prog_var, foreign_arg)::in,
	map(prog_var, foreign_arg)::out) is det.

build_arg_map([], !ArgMap).
build_arg_map([ForeignArg | ForeignArgs], !ArgMap) :-
	ForeignArg = foreign_arg(Var, _, _),
	map__det_insert(!.ArgMap, Var, ForeignArg, !:ArgMap),
	build_arg_map(ForeignArgs, !ArgMap).

:- pred ml_gen_pragma_il_proc_assign_output(module_info::in,
	mlds_module_name::in, map(prog_var, foreign_arg)::in, prog_varset::in,
	prog_context::in, bool::in, prog_var::in, mlds__statement::out)
	is semidet.

ml_gen_pragma_il_proc_assign_output(ModuleInfo, MLDSModuleName, ArgMap,
		VarSet, Context, IsByRef, Var, Statement) :-
	map__lookup(ArgMap, Var, ForeignArg),
	ForeignArg = foreign_arg(_, MaybeNameMode, Type),
	not type_util__is_dummy_argument_type(Type),
	MLDSType = mercury_type_to_mlds_type(ModuleInfo, Type),

	VarName = ml_gen_var_name(VarSet, Var),
	QualVarName = qual(MLDSModuleName, module_qual, VarName),
	(
		IsByRef = yes,
		OutputVarLval = mem_ref(lval(var(QualVarName, MLDSType)),
			MLDSType)
	;
		IsByRef = no,
		OutputVarLval = var(QualVarName, MLDSType)
	),

	MaybeNameMode = yes(UserVarNameString - _),
	NonMangledVarName = mlds__var_name(UserVarNameString, no),
	QualLocalVarName= qual(MLDSModuleName, module_qual, NonMangledVarName),
	LocalVarLval = var(QualLocalVarName, MLDSType),

	Statement = ml_gen_assign(OutputVarLval, lval(LocalVarLval), Context).

:- pred ml_gen_pragma_il_proc_var_decl_defn(module_info::in,
	mlds_module_name::in, map(prog_var, foreign_arg)::in, prog_varset::in,
	mlds__context::in, list(prog_var)::in, list(prog_var)::in,
	prog_var::in, mlds__defn::out) is det.

ml_gen_pragma_il_proc_var_decl_defn(ModuleInfo, MLDSModuleName, ArgMap, VarSet,
		MLDSContext, ByRefOutputVars, CopiedOutputVars, Var, Defn) :-
	map__lookup(ArgMap, Var, ForeignArg),
	ForeignArg = foreign_arg(_, MaybeNameMode, Type),
	VarName = ml_gen_var_name(VarSet, Var),
	( MaybeNameMode = yes(UserVarNameString - _) ->
		NonMangledVarName = mlds__var_name(UserVarNameString, no)
	;
		sorry(this_file, "no variable name for var")
	),

		% Dummy arguments are just mapped to integers,
		% since they shouldn't be used in any
		% way that requires them to have a real value.
	( type_util__is_dummy_argument_type(Type) ->
		Initializer = no_initializer,
		MLDSType = mlds__native_int_type
	; list__member(Var, ByRefOutputVars) ->
		Initializer = no_initializer,
		MLDSType = mercury_type_to_mlds_type(ModuleInfo, Type)
	; list__member(Var, CopiedOutputVars) ->
		Initializer = no_initializer,
		MLDSType = mercury_type_to_mlds_type(ModuleInfo, Type)
	;
		MLDSType = mercury_type_to_mlds_type(
			ModuleInfo, Type),
		QualVarName = qual(MLDSModuleName, module_qual, VarName),
		Initializer = init_obj(
			lval(var(QualVarName, MLDSType)))
	),
	% XXX Accurate GC is not supported for IL foreign code;
	% this would only be useful if interfacing to
	% IL when compiling to C, which is not yet supported.
	GC_TraceCode = no,
	Defn = ml_gen_mlds_var_decl(var(NonMangledVarName), MLDSType,
		Initializer, GC_TraceCode, MLDSContext).

	% For ordinary (not model_non) pragma c_proc,
	% we generate code of the following form:
	%
	% model_det pragma_c_proc:
	%
	%	#define MR_PROC_LABEL <procedure name>
	% 	<declaration of locals needed for boxing/unboxing>
	%	{
	% 		<declaration of one local variable for each arg>
	%
	%		<assign input args>
	%		<obtain global lock>
	%		<c code>
	% 		<boxing/unboxing of outputs>
	%		<release global lock>
	%		<assign output args>
	%	}
	%	#undef MR_PROC_LABEL
	%
	% model_semi pragma_c_proc:
	%
	%	#define MR_PROC_LABEL <procedure name>
	% 	<declaration of locals needed for boxing/unboxing>
	%	{
	% 		<declaration of one local variable for each arg>
	%		MR_bool SUCCESS_INDICATOR;
	%
	%		<assign input args>
	%		<obtain global lock>
	%		<c code>
	%		<release global lock>
	%		if (SUCCESS_INDICATOR) {
	%			<assign output args>
	% 			<boxing/unboxing of outputs>
	%		}
	%
	%		<succeeded> = SUCCESS_INDICATOR;
	%	}
	%	#undef MR_PROC_LABEL
	%
	% We insert a #define for MR_PROC_LABEL, so that the C code in
	% the Mercury standard library that allocates memory manually
	% can use MR_PROC_LABEL as the procname argument to
	% incr_hp_msg(), for memory profiling. Hard-coding the procname
	% argument in the C code would be wrong, since it wouldn't
	% handle the case where the original pragma c_code procedure
	% gets inlined and optimized away. Of course we also need to
	% #undef it afterwards.
	%
	% Note that we generate this code directly as
	% `target_code(lang_C, <string>)' instructions in the MLDS.
	% It would probably be nicer to encode more of the structure
	% in the MLDS, so that (a) we could do better MLDS optimization
	% and (b) so that the generation of C code strings could be
	% isolated in mlds_to_c.m. Also we will need to do something
	% different for targets other than C, e.g. when compiling to
	% Java.
	%
:- pred ml_gen_ordinary_pragma_c_proc(ordinary_pragma_kind::in,
	pragma_foreign_proc_attributes::in, pred_id::in, proc_id::in,
	list(foreign_arg)::in, list(foreign_arg)::in, string::in,
	prog_context::in, mlds__defns::out, mlds__statements::out,
	ml_gen_info::in, ml_gen_info::out) is det.

ml_gen_ordinary_pragma_c_proc(OrdinaryKind, Attributes, PredId, _ProcId,
		OrigArgs, ExtraArgs, C_Code, Context, Decls, Statements,
		!Info) :-

	Lang = foreign_language(Attributes),

	%
	% Generate <declaration of one local variable for each arg>
	%
	list__append(OrigArgs, ExtraArgs, Args),
	ml_gen_pragma_c_decls(!.Info, Lang, Args, ArgDeclsList),

	%
	% Generate code to set the values of the input variables.
	%
	ml_gen_pragma_c_input_arg_list(Lang, Args, AssignInputsList, !Info),

	%
	% Generate code to assign the values of the output variables.
	%
	ml_gen_pragma_c_output_arg_list(Lang, Args, Context,
		AssignOutputsList, ConvDecls, ConvStatements, !Info),

	%
	% Generate code fragments to obtain and release the global lock
	%
	ThreadSafe = thread_safe(Attributes),
	ml_gen_obtain_release_global_lock(!.Info, ThreadSafe, PredId,
		ObtainLock, ReleaseLock),

	%
	% Generate the MR_PROC_LABEL #define
	%
	ml_gen_hash_define_mr_proc_label(!.Info, HashDefine),

	%
	% Put it all together
	%
	(
		OrdinaryKind = kind_det,
		Starting_C_Code = list__condense([
			[raw_target_code("{\n", [])],
			HashDefine,
			ArgDeclsList,
			[raw_target_code("\n", [])],
			AssignInputsList,
			[raw_target_code(ObtainLock, []),
			raw_target_code("\t\t{\n", []),
			user_target_code(C_Code, yes(Context), []),
			raw_target_code("\n\t\t;}\n", []),
			raw_target_code("#undef MR_PROC_LABEL\n", []),
			raw_target_code(ReleaseLock, [])],
			AssignOutputsList
		]),
		Ending_C_Code = [raw_target_code("}\n", [])]
	;
		OrdinaryKind = kind_failure,
		% We need to treat this case separately, because for these
		% foreign_procs the C code fragment won't assign anything
		% SUCCESS_INDICATOR; the code we generate for CanSucceed = yes
		% would test an undefined value.
		ml_success_lval(!.Info, SucceededLval),
		Starting_C_Code = list__condense([
			[raw_target_code("{\n", [])],
			HashDefine,
			ArgDeclsList,
			[raw_target_code("\n", [])],
			AssignInputsList,
			[raw_target_code(ObtainLock, []),
			raw_target_code("\t\t{\n", []),
			user_target_code(C_Code, yes(Context), []),
			raw_target_code("\n\t\t;}\n", []),
			raw_target_code("#undef MR_PROC_LABEL\n", []),
			raw_target_code(ReleaseLock, [])]
		]),
		Ending_C_Code = [
			target_code_output(SucceededLval),
			raw_target_code(" = MR_FALSE;\n", []),
			raw_target_code("}\n", [])
		]
	;
		OrdinaryKind = kind_semi,
		ml_success_lval(!.Info, SucceededLval),
		Starting_C_Code = list__condense([
			[raw_target_code("{\n", [])],
			HashDefine,
			ArgDeclsList,
			[raw_target_code("\tMR_bool SUCCESS_INDICATOR;\n", []),
			raw_target_code("\n", [])],
			AssignInputsList,
			[raw_target_code(ObtainLock, []),
			raw_target_code("\t\t{\n", []),
			user_target_code(C_Code, yes(Context), []),
			raw_target_code("\n\t\t;}\n", []),
			raw_target_code("#undef MR_PROC_LABEL\n", []),
			raw_target_code(ReleaseLock, []),
			raw_target_code("\tif (SUCCESS_INDICATOR) {\n", [])],
			AssignOutputsList
		]),
		Ending_C_Code = [
			raw_target_code("\t}\n", []),
			target_code_output(SucceededLval),
			raw_target_code(" = SUCCESS_INDICATOR;\n", []),
			raw_target_code("}\n", [])
		]
	),
	Starting_C_Code_Stmt = inline_target_code(lang_C, Starting_C_Code),
	Ending_C_Code_Stmt = inline_target_code(lang_C, Ending_C_Code),
	Starting_C_Code_Statement = mlds__statement(
		atomic(Starting_C_Code_Stmt), mlds__make_context(Context)),
	Ending_C_Code_Statement = mlds__statement(atomic(Ending_C_Code_Stmt),
		mlds__make_context(Context)),
	Statements = list__condense([
		[Starting_C_Code_Statement],
		ConvStatements,
		[Ending_C_Code_Statement]
	]),
	Decls = ConvDecls.

	% Generate code fragments to obtain and release the global lock
	% (this is used for ensuring thread safety in a concurrent
	% implementation)
	%
:- pred ml_gen_obtain_release_global_lock(ml_gen_info::in, thread_safe::in,
	pred_id::in, string::out, string::out) is det.

ml_gen_obtain_release_global_lock(Info, ThreadSafe, PredId,
		ObtainLock, ReleaseLock) :-
	ml_gen_info_get_module_info(Info, ModuleInfo),
	module_info_globals(ModuleInfo, Globals),
	globals__lookup_bool_option(Globals, parallel, Parallel),
	(
		Parallel = yes,
		ThreadSafe = not_thread_safe
	->
		module_info_pred_info(ModuleInfo, PredId, PredInfo),
		Name = pred_info_name(PredInfo),
		c_util__quote_string(Name, MangledName),
		string__append_list(["\tMR_OBTAIN_GLOBAL_LOCK(""",
			MangledName, """);\n"], ObtainLock),
		string__append_list(["\tMR_RELEASE_GLOBAL_LOCK(""",
			MangledName, """);\n"], ReleaseLock)
	;
		ObtainLock = "",
		ReleaseLock = ""
	).

:- pred ml_gen_hash_define_mr_proc_label(ml_gen_info::in,
	list(target_code_component)::out) is det.

ml_gen_hash_define_mr_proc_label(Info, HashDefine) :-
	ml_gen_info_get_module_info(Info, ModuleInfo),
	% Note that we use the pred_id and proc_id of the current procedure,
	% not the one that the pragma foreign_code originally came from.
	% There may not be any function address for the latter, e.g. if it
	% has been inlined and the original definition optimized away.
	ml_gen_info_get_pred_id(Info, PredId),
	ml_gen_info_get_proc_id(Info, ProcId),
	ml_gen_proc_label(ModuleInfo, PredId, ProcId, Name, Module),
	HashDefine = [raw_target_code("#define MR_PROC_LABEL ", []),
		name(qual(Module, module_qual, Name)),
		raw_target_code("\n", [])].

:- func get_target_code_attributes(foreign_language,
	pragma_foreign_proc_extra_attributes) = target_code_attributes.

get_target_code_attributes(_, []) = [].
get_target_code_attributes(Lang, [max_stack_size(N) | Xs]) =
	( Lang = il ->
		[max_stack_size(N) | get_target_code_attributes(Lang, Xs)]
	;
		[]
	).

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

% ml_gen_pragma_c_decls generates C code to declare the arguments
% for a `pragma foreign_proc' declaration.
%
:- pred ml_gen_pragma_c_decls(ml_gen_info::in, foreign_language::in,
	list(foreign_arg)::in, list(target_code_component)::out) is det.

	% XXX Maybe this ought to be renamed as it works for, and
	% is used by the Java back-end as well.
	%
ml_gen_pragma_c_decls(_, _, [], []).
ml_gen_pragma_c_decls(Info, Lang, [Arg | Args], [Decl | Decls]) :-
	ml_gen_pragma_c_decl(Info, Lang, Arg, Decl),
	ml_gen_pragma_c_decls(Info, Lang, Args, Decls).

% ml_gen_pragma_c_decl generates C code to declare an argument
% of a `pragma foreign_proc' declaration.
%
:- pred ml_gen_pragma_c_decl(ml_gen_info::in, foreign_language::in,
	foreign_arg::in, target_code_component::out) is det.

ml_gen_pragma_c_decl(Info, Lang, foreign_arg(_Var, MaybeNameAndMode, Type),
		Decl) :-
	ml_gen_info_get_module_info(Info, ModuleInfo),
	(
		MaybeNameAndMode = yes(ArgName - _Mode),
		\+ var_is_singleton(ArgName)
	->
		TypeString = foreign__to_type_string(Lang, ModuleInfo, Type),
		string__format("\t%s %s;\n", [s(TypeString), s(ArgName)],
			DeclString)
	;
		% if the variable doesn't occur in the ArgNames list,
		% it can't be used, so we just ignore it
		DeclString = ""
	),
	Decl = raw_target_code(DeclString, []).

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

% var_is_singleton determines whether or not a given pragma_c variable
% is singleton (i.e. starts with an underscore)
%
% Singleton vars should be ignored when generating the declarations for
% pragma_c arguments because:
%
%	- they should not appear in the C code
% 	- they could clash with the system name space
%
:- pred var_is_singleton(string::in) is semidet.

var_is_singleton(Name) :-
	string__first_char(Name, '_', _).

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

	% XXX Maybe this ought to be renamed as it works for, and
	% is used by the Java back-end as well.
	%
:- pred ml_gen_pragma_c_input_arg_list(foreign_language::in,
	list(foreign_arg)::in, list(target_code_component)::out,
	ml_gen_info::in, ml_gen_info::out) is det.

ml_gen_pragma_c_input_arg_list(Lang, ArgList, AssignInputs, !Info) :-
	list__map_foldl(ml_gen_pragma_c_input_arg(Lang), ArgList,
		AssignInputsList, !Info),
	list__condense(AssignInputsList, AssignInputs).

	% ml_gen_pragma_c_input_arg generates C code to assign the value of an
	% input arg for a `pragma foreign_proc' declaration.
	%
:- pred ml_gen_pragma_c_input_arg(foreign_language::in, foreign_arg::in,
	list(target_code_component)::out,
	ml_gen_info::in, ml_gen_info::out) is det.

ml_gen_pragma_c_input_arg(Lang, ForeignArg, AssignInput, !Info) :-
	ml_gen_info_get_module_info(!.Info, ModuleInfo),
	(
		ForeignArg = foreign_arg(Var, MaybeNameAndMode, OrigType),
		MaybeNameAndMode = yes(ArgName - Mode),
		\+ var_is_singleton(ArgName),
		mode_to_arg_mode(ModuleInfo, Mode, OrigType, top_in)
	->
		ml_gen_pragma_c_gen_input_arg(Lang, Var, ArgName, OrigType,
			AssignInput, !Info)
	;
		% If the variable doesn't occur in the ArgNames list,
		% it can't be used, so we just ignore it.
		AssignInput = []
	).

:- pred ml_gen_pragma_c_gen_input_arg(foreign_language::in, prog_var::in,
	string::in, prog_type::in, list(target_code_component)::out,
	ml_gen_info::in, ml_gen_info::out) is det.

ml_gen_pragma_c_gen_input_arg(Lang, Var, ArgName, OrigType, AssignInput,
		!Info) :-
	ml_variable_type(!.Info, Var, VarType),
	ml_gen_var(!.Info, Var, VarLval),
	( type_util__is_dummy_argument_type(VarType) ->
		% The variable may not have been declared, so we need
		% to generate a dummy value for it. Using `0' here
		% is more efficient than using private_builtin__dummy_var,
		% which is what ml_gen_var will have generated for this
		% variable.
		ArgRval = const(int_const(0))
	;
		ml_gen_box_or_unbox_rval(VarType, OrigType, lval(VarLval),
			ArgRval, !Info)
	),
	% At this point we have an rval with the right type for
	% *internal* use in the code generated by the Mercury
	% compiler's MLDS back-end. We need to convert this to
	% the appropriate type to use for the C interface.
	ml_gen_info_get_module_info(!.Info, ModuleInfo),
	ExportedType = foreign__to_exported_type(ModuleInfo, OrigType),
	TypeString = foreign__to_type_string(Lang, ExportedType),
	IsForeign = foreign__is_foreign_type(ExportedType),
	(
		(
			Lang = java,
			MaybeCast = no
		;
			Lang = c,
			IsForeign = no,
			MaybeCast = no
		;
			Lang = c,
			IsForeign = yes(Assertions),
			list__member(can_pass_as_mercury_type, Assertions),
			MaybeCast = yes("(" ++ TypeString ++ ") ")
		)
	->
		% In the usual case, we can just use an assignment
		% and perhaps a cast.
		module_info_globals(ModuleInfo, Globals),
		globals__lookup_bool_option(Globals, highlevel_data,
			HighLevelData),
		(
			HighLevelData = yes,
			% In general, the types used for the C
			% interface are not the same as the types
			% used by --high-level-data, so we always
			% use a cast here.
			% (Strictly speaking the cast is not needed for
			% a few cases like `int', but it doesn't do
			% any harm.)
			string__format("(%s)", [s(TypeString)], Cast)
		;
			HighLevelData = no,
			% For --no-high-level-data, we only need to use
			% a cast is for polymorphic types, which are
			% `Word' in the C interface but `MR_Box' in the
			% MLDS back-end.
			% Except for MC++, where polymorphic types
			% are MR_Box.
			(
				prog_type__var(OrigType, _),
				Lang \= managed_cplusplus
			->
				Cast = "(MR_Word) "
			;
				MaybeCast = yes(CastPrime)
			->
				Cast = CastPrime
			;
				Cast = ""
			)
		),
		string__format("\t%s = %s\n", [s(ArgName), s(Cast)],
			AssignToArgName),
		AssignInput = [
			raw_target_code(AssignToArgName, []),
			target_code_input(ArgRval),
			raw_target_code(";\n", [])
		]
	;
		% For foreign types,
		% we need to call MR_MAYBE_UNBOX_FOREIGN_TYPE
		% XXX not if can_pass_as_mercury_type is set
		AssignInput = [
			raw_target_code("\tMR_MAYBE_UNBOX_FOREIGN_TYPE("
				++ TypeString ++ ", ", []),
			target_code_input(ArgRval),
			raw_target_code(", " ++ ArgName ++ ");\n", [])
		]
	).

:- pred ml_gen_pragma_java_output_arg_list(foreign_language::in,
	list(foreign_arg)::in, prog_context::in, mlds__statements::out,
	mlds__defns::out, mlds__statements::out,
	ml_gen_info::in, ml_gen_info::out) is det.

ml_gen_pragma_java_output_arg_list(_, [], _, [], [], [], !Info).
ml_gen_pragma_java_output_arg_list(Lang, [Java_Arg | Java_Args], Context,
		Statements, ConvDecls, ConvStatements, !Info) :-
	ml_gen_pragma_java_output_arg(Lang, Java_Arg, Context, Statements1,
		ConvDecls1, ConvStatements1, !Info),
	ml_gen_pragma_java_output_arg_list(Lang, Java_Args, Context,
		Statements2, ConvDecls2, ConvStatements2, !Info),
	Statements = Statements1 ++ Statements2,
	ConvDecls = ConvDecls1 ++ ConvDecls2,
	ConvStatements = ConvStatements1 ++ ConvStatements2.

% ml_gen_pragma_java_output_arg generates MLDS statements to
% assign the value of an output arg for a `pragma foreign_proc'
% declaration.
%
:- pred ml_gen_pragma_java_output_arg(foreign_language::in,
	foreign_arg::in, prog_context::in, mlds__statements::out,
	mlds__defns::out, mlds__statements::out,
	ml_gen_info::in, ml_gen_info::out) is det.

ml_gen_pragma_java_output_arg(_Lang, ForeignArg, Context, AssignOutput,
		ConvDecls, ConvOutputStatements, !Info) :-
	ForeignArg = foreign_arg(Var, MaybeNameAndMode, OrigType),
	ml_gen_info_get_module_info(!.Info, ModuleInfo),
	(
		MaybeNameAndMode = yes(ArgName - Mode),
		not var_is_singleton(ArgName),
		not type_util__is_dummy_argument_type(OrigType),
		mode_to_arg_mode(ModuleInfo, Mode, OrigType, top_out)
	->
		% Create a target lval with the right type for *internal*
		% use in the code generated by the Mercury compiler's
		% MLDS back-end.
		ml_variable_type(!.Info, Var, VarType),
		ml_gen_var(!.Info, Var, VarLval),
		ml_gen_box_or_unbox_lval(VarType, OrigType, VarLval,
			mlds__var_name(ArgName, no), Context, no, 0,
			ArgLval, ConvDecls, _ConvInputStatements,
			ConvOutputStatements, !Info),
		% This is the MLDS type of the original argument, which
		% we need to cast the local (Java) representation of
		% the argument back to.
		MLDSType = mercury_type_to_mlds_type(ModuleInfo, OrigType),
		% Construct an MLDS lval for the local Java representation
		% of the argument.
		module_info_name(ModuleInfo, ModuleName),
		MLDSModuleName = mercury_module_name_to_mlds(ModuleName),
		NonMangledVarName = mlds__var_name(ArgName, no),
		QualLocalVarName = qual(MLDSModuleName, module_qual,
			NonMangledVarName),
		% XXX MLDSType is the incorrect type for this variable.
		% It should have the Java foreign language representation
		% of that type. Unfortunately this is not easily expressed
		% as an mlds__type.
		LocalVarLval = var(QualLocalVarName, MLDSType),
		% We cast this variable back to the corresponding
		% MLDS type before assigning it to the lval
		Rval = unop(cast(MLDSType), lval(LocalVarLval)),
		AssignOutput = [ml_gen_assign(ArgLval, Rval, Context)]
	;
		% if the variable doesn't occur in the ArgNames list,
		% it can't be used, so we just ignore it
		AssignOutput = [],
		ConvDecls = [],
		ConvOutputStatements = []
	).

:- pred ml_gen_pragma_c_output_arg_list(foreign_language::in,
	list(foreign_arg)::in, prog_context::in,
	list(target_code_component)::out, mlds__defns::out,
	mlds__statements::out, ml_gen_info::in, ml_gen_info::out) is det.

ml_gen_pragma_c_output_arg_list(_, [], _, [], [], [], !Info).
ml_gen_pragma_c_output_arg_list(Lang, [ForeignArg | ForeignArgs], Context,
		Components, ConvDecls, ConvStatements, !Info) :-
	ml_gen_pragma_c_output_arg(Lang, ForeignArg, Context, Components1,
		ConvDecls1, ConvStatements1, !Info),
	ml_gen_pragma_c_output_arg_list(Lang, ForeignArgs, Context,
		Components2, ConvDecls2, ConvStatements2, !Info),
	Components = list__append(Components1, Components2),
	ConvDecls = list__append(ConvDecls1, ConvDecls2),
	ConvStatements = list__append(ConvStatements1, ConvStatements2).

% ml_gen_pragma_c_output_arg generates C code to assign the value of an output
% arg for a `pragma foreign_proc' declaration.
%
:- pred ml_gen_pragma_c_output_arg(foreign_language::in, foreign_arg::in,
	prog_context::in, list(target_code_component)::out,
	mlds__defns::out, mlds__statements::out,
	ml_gen_info::in, ml_gen_info::out) is det.

ml_gen_pragma_c_output_arg(Lang, foreign_arg(Var, MaybeNameAndMode, OrigType),
		Context, AssignOutput, ConvDecls, ConvOutputStatements,
		!Info) :-
	ml_gen_info_get_module_info(!.Info, ModuleInfo),
	(
		MaybeNameAndMode = yes(ArgName - Mode),
		\+ var_is_singleton(ArgName),
		\+ type_util__is_dummy_argument_type(OrigType),
		mode_to_arg_mode(ModuleInfo, Mode, OrigType, top_out)
	->
		ml_gen_pragma_c_gen_output_arg(Lang, Var, ArgName, OrigType,
			Context, AssignOutput, ConvDecls, ConvOutputStatements,
			!Info)
	;
		% if the variable doesn't occur in the ArgNames list,
		% it can't be used, so we just ignore it
		AssignOutput = [],
		ConvDecls = [],
		ConvOutputStatements = []
	).

:- pred ml_gen_pragma_c_gen_output_arg(foreign_language::in, prog_var::in,
	string::in, prog_type::in, prog_context::in,
	list(target_code_component)::out, mlds__defns::out,
	mlds__statements::out, ml_gen_info::in, ml_gen_info::out) is det.

ml_gen_pragma_c_gen_output_arg(Lang, Var, ArgName, OrigType, Context,
		AssignOutput, ConvDecls, ConvOutputStatements, !Info) :-
	ml_variable_type(!.Info, Var, VarType),
	ml_gen_var(!.Info, Var, VarLval),
	ml_gen_box_or_unbox_lval(VarType, OrigType, VarLval,
		mlds__var_name(ArgName, no), Context, no, 0,
		ArgLval, ConvDecls, _ConvInputStatements,
		ConvOutputStatements, !Info),
	% At this point we have an lval with the right type for
	% *internal* use in the code generated by the Mercury
	% compiler's MLDS back-end. We need to convert this to
	% the appropriate type to use for the C interface.
	ml_gen_info_get_module_info(!.Info, ModuleInfo),
	ExportedType = foreign__to_exported_type(ModuleInfo, OrigType),
	TypeString = foreign__to_type_string(Lang, ExportedType),
	IsForeign = foreign__is_foreign_type(ExportedType),
	(
		(
			Lang = java,
			IsForeign = no,
			Cast = no
		;
			Lang = c,
			IsForeign = no,
			Cast = no
		;
			Lang = c,
			IsForeign = yes(Assertions),
			list__member(can_pass_as_mercury_type, Assertions),
			Cast = yes
		)
	->
		% In the usual case, we can just use an assignment,
		% perhaps with a cast.
		module_info_globals(ModuleInfo, Globals),
		globals__lookup_bool_option(Globals, highlevel_data,
			HighLevelData),
		(
			HighLevelData = yes,
			% In general, the types used for the C interface
			% are not the same as the types used by
			% --high-level-data, so we always use a cast here.
			% (Strictly speaking the cast is not needed for
			% a few cases like `int', but it doesn't do any harm.)
			% Note that we can't easily obtain the type string
			% for the RHS of the assignment, so instead we cast
			% the LHS.
			string__format("*(%s *)&", [s(TypeString)], LHS_Cast),
			RHS_Cast = ""
		;
			HighLevelData = no,
			% For --no-high-level-data, we only need to use
			% a cast is for polymorphic types, which are
			% `Word' in the C interface but `MR_Box' in the
			% MLDS back-end.
			(
				( prog_type__var(OrigType, _)
				; Cast = yes
				)
			->
				RHS_Cast = "(MR_Box) "
			;
				RHS_Cast = ""
			),
			LHS_Cast = ""
		),
		string__format(" = %s%s;\n", [s(RHS_Cast),
			s(ArgName)], AssignFromArgName),
		string__format("\t%s\n", [s(LHS_Cast)], AssignTo),
		AssignOutput = [
			raw_target_code(AssignTo, []),
			target_code_output(ArgLval),
			raw_target_code(AssignFromArgName, [])
		]
	;
		% For foreign types, we need to call MR_MAYBE_BOX_FOREIGN_TYPE.
		AssignOutput = [
			raw_target_code("\tMR_MAYBE_BOX_FOREIGN_TYPE("
				++ TypeString ++ ", " ++ ArgName ++
				", ", []),
			target_code_output(ArgLval),
			raw_target_code(");\n", [])
		]
	).

% :- end_module ml_foreign.

%-----------------------------------------------------------------------------%
%
% Code for if-then-else
%

:- pred ml_gen_ite(code_model::in, hlds_goal::in, hlds_goal::in, hlds_goal::in,
	prog_context::in, mlds__defns::out, mlds__statements::out,
	ml_gen_info::in, ml_gen_info::out) is det.

ml_gen_ite(CodeModel, Cond, Then, Else, Context, Decls, Statements, !Info) :-
	Cond = _ - CondGoalInfo,
	goal_info_get_code_model(CondGoalInfo, CondCodeModel),
	(
		%	model_det Cond:
		%		<(Cond -> Then ; Else)>
		%	===>
		%		<Cond>
		%		<Then>
		CondCodeModel = model_det,
		ml_gen_goal(model_det, Cond, CondStatement, !Info),
		ml_gen_goal(CodeModel, Then, ThenStatement, !Info),
		Decls = [],
		Statements = [CondStatement, ThenStatement]
	;
		%	model_semi cond:
		%		<(Cond -> Then ; Else)>
		%	===>
		%		MR_bool succeeded;
		%
		%		<succeeded = Cond>
		%		if (succeeded) {
		%			<Then>
		%		} else {
		%			<Else>
		%		}
		CondCodeModel = model_semi,
		ml_gen_goal(model_semi, Cond, CondDecls, CondStatements, !Info),
		ml_gen_test_success(!.Info, Succeeded),
		ml_gen_goal(CodeModel, Then, ThenStatement, !Info),
		ml_gen_goal(CodeModel, Else, ElseStatement, !Info),
		IfStmt = if_then_else(Succeeded, ThenStatement,
			yes(ElseStatement)),
		IfStatement = mlds__statement(IfStmt,
			mlds__make_context(Context)),
		Decls = CondDecls,
		Statements = list__append(CondStatements,
			[IfStatement])
	;
		%	/*
		%	** XXX The following transformation does not do as
		%	** good a job of GC as it could. Ideally we ought
		%	** to ensure that stuff used only in the `Else' part
		%	** will be reclaimed if a GC occurs during the `Then'
		%	** part. But that is a bit tricky to achieve.
		%	*/
		%
		%	model_non cond:
		%		<(Cond -> Then ; Else)>
		%	===>
		%		MR_bool cond_<N>;
		%
		%		void then_func() {
		%			cond_<N> = MR_TRUE;
		%			<Then>
		%		}
		%
		%		cond_<N> = MR_FALSE;
		%		<Cond && then_func()>
		%		if (!cond_<N>) {
		%			<Else>
		%		}
		%	except that we hoist any declarations generated
		%	for <Cond> to the top of the scope, so that they
		%	are in scope for the <Then> goal
		%	(this is needed for declarations of static consts)

		CondCodeModel = model_non,

		% generate the `cond_<N>' var and the code to initialize it to false
		ml_gen_info_new_cond_var(CondVar, !Info),
		MLDS_Context = mlds__make_context(Context),
		CondVarDecl = ml_gen_cond_var_decl(CondVar, MLDS_Context),
		ml_gen_set_cond_var(!.Info, CondVar, const(false), Context,
			SetCondFalse),

		% allocate a name for the `then_func'
		ml_gen_new_func_label(no, ThenFuncLabel, ThenFuncLabelRval,
			!Info),

		% generate <Cond && then_func()>
		ml_get_env_ptr(!.Info, EnvPtrRval),
		SuccessCont = success_cont(ThenFuncLabelRval, EnvPtrRval,
			[], []),
		ml_gen_info_push_success_cont(SuccessCont, !Info),
		ml_gen_goal(model_non, Cond, CondDecls, CondStatements, !Info),
		ml_gen_info_pop_success_cont(!Info),

		% generate the `then_func'
		/* push nesting level */
		Then = _ - ThenGoalInfo,
		goal_info_get_context(ThenGoalInfo, ThenContext),
		ml_gen_set_cond_var(!.Info, CondVar, const(true), ThenContext,
			SetCondTrue),
		ml_gen_goal(CodeModel, Then, ThenStatement, !Info),
		ThenFuncBody = ml_gen_block([],
			[SetCondTrue, ThenStatement], ThenContext),
		/* pop nesting level */
		ml_gen_nondet_label_func(!.Info, ThenFuncLabel, ThenContext,
			ThenFuncBody, ThenFunc),

		% generate `if (!cond_<N>) { <Else> }'
		ml_gen_test_cond_var(!.Info, CondVar, CondSucceeded),
		ml_gen_goal(CodeModel, Else, ElseStatement, !Info),
		IfStmt = if_then_else(unop(std_unop(not), CondSucceeded),
			ElseStatement, no),
		IfStatement = mlds__statement(IfStmt, MLDS_Context),

		% package it all up in the right order
		Decls = list__append([CondVarDecl | CondDecls], [ThenFunc]),
		Statements = list__append(
			[SetCondFalse | CondStatements], [IfStatement])
	).

%-----------------------------------------------------------------------------%
%
% Code for negation
%

:- pred ml_gen_negation(hlds_goal::in, code_model::in, prog_context::in,
	mlds__defns::out, mlds__statements::out,
	ml_gen_info::in, ml_gen_info::out) is det.

ml_gen_negation(Cond, CodeModel, Context, Decls, Statements, !Info) :-
	Cond = _ - CondGoalInfo,
	goal_info_get_code_model(CondGoalInfo, CondCodeModel),
	(
		% model_det negation:
		%		<not(Goal)>
		%	===>
		%	{
		%		MR_bool succeeded;
		%		<succeeded = Goal>
		%		/* now ignore the value of succeeded,
		%		 which we know will be MR_FALSE */
		%	}
		CodeModel = model_det,
		ml_gen_goal(model_semi, Cond, Decls, Statements, !Info)
	;
		% model_semi negation, model_det goal:
		%		<succeeded = not(Goal)>
		%	===>
		%		<do Goal>
		%		succeeded = MR_FALSE;
		CodeModel = model_semi, CondCodeModel = model_det,
		ml_gen_goal(model_det, Cond, CondDecls, CondStatements, !Info),
		ml_gen_set_success(!.Info, const(false), Context,
			SetSuccessFalse),
		Decls = CondDecls,
		Statements = list__append(CondStatements, [SetSuccessFalse])
	;
		% model_semi negation, model_semi goal:
		%		<succeeded = not(Goal)>
		%	===>
		%		<succeeded = Goal>
		%		succeeded = !succeeded;
		CodeModel = model_semi, CondCodeModel = model_semi,
		ml_gen_goal(model_semi, Cond, CondDecls, CondStatements,
			!Info),
		ml_gen_test_success(!.Info, Succeeded),
		ml_gen_set_success(!.Info, unop(std_unop(not), Succeeded),
			Context, InvertSuccess),
		Decls = CondDecls,
		Statements = list__append(CondStatements, [InvertSuccess])
	;
		CodeModel = model_semi, CondCodeModel = model_non,
		error("ml_gen_negation: nondet cond")
	;
		CodeModel = model_non,
		error("ml_gen_negation: nondet negation")
	).

%-----------------------------------------------------------------------------%
%
% Code for conjunctions
%

:- pred ml_gen_conj(hlds_goals::in, code_model::in, prog_context::in,
	mlds__defns::out, mlds__statements::out,
	ml_gen_info::in, ml_gen_info::out) is det.

ml_gen_conj([], CodeModel, Context, [], Statements, !Info) :-
	ml_gen_success(CodeModel, Context, Statements, !Info).
ml_gen_conj([SingleGoal], CodeModel, _Context, Decls, Statements, !Info) :-
	ml_gen_goal(CodeModel, SingleGoal, Decls, Statements, !Info).
ml_gen_conj([First | Rest], CodeModel, Context, Decls, Statements, !Info) :-
	Rest = [_ | _],
	First = _ - FirstGoalInfo,
	goal_info_get_determinism(FirstGoalInfo, FirstDeterminism),
	( determinism_components(FirstDeterminism, _, at_most_zero) ->
		% the `Rest' code is unreachable
		ml_gen_goal(CodeModel, First, Decls, Statements, !Info)
	;
		determinism_to_code_model(FirstDeterminism, FirstCodeModel),
		DoGenFirst = ml_gen_goal(FirstCodeModel, First),
		DoGenRest = ml_gen_conj(Rest, CodeModel, Context),
		ml_combine_conj(FirstCodeModel, Context, DoGenFirst, DoGenRest,
			Decls, Statements, !Info)
	).

%-----------------------------------------------------------------------------%
%
% Code for disjunctions
%

:- pred ml_gen_disj(hlds_goals::in, code_model::in, prog_context::in,
	mlds__defns::out, mlds__statements::out,
	ml_gen_info::in, ml_gen_info::out) is det.

	%
	% handle empty disjunctions (a.ka. `fail')
	%
ml_gen_disj([], CodeModel, Context, [], Statements, !Info) :-
	ml_gen_failure(CodeModel, Context, Statements, !Info).

	%
	% handle singleton disjunctions
	% (the HLDS should not contain singleton disjunctions,
	% but this code is needed to handle recursive calls to ml_gen_disj)
	% Note that each arm of the model_non disjunction is placed into
	% a block. This avoids a problem where ml_join_decls can create
	% block nesting proportional to the size of the disjunction.
	% The nesting can hit fixed limit problems in some C compilers.
	%
ml_gen_disj([SingleGoal], CodeModel, Context, [], [Statement], !Info) :-
	ml_gen_goal(CodeModel, SingleGoal, Goal_Decls, Goal_Statements, !Info),
	Statement = ml_gen_block(Goal_Decls, Goal_Statements, Context).

ml_gen_disj([First | Rest], CodeModel, Context, Decls, Statements, !Info) :-
	Rest = [_ | _],
	( CodeModel = model_non ->
		%
		% model_non disj:
		%
		%		<(Goal ; Goals) && SUCCEED()>
		%	===>
		%		<Goal && SUCCEED()>
		%		<Goals && SUCCEED()>
		%
		ml_gen_goal(model_non, First, FirstDecls, FirstStatements,
			!Info),
		ml_gen_disj(Rest, model_non, Context,
			RestDecls, RestStatements, !Info),

		(
			RestDecls = []
		->
			FirstBlock = ml_gen_block(FirstDecls,
					FirstStatements, Context),
			Decls = [],
			Statements = [FirstBlock | RestStatements]
		;
			error("ml_gen_disj: RestDecls not empty.")
		)

	; /* CodeModel is model_det or model_semi */
		%
		% model_det/model_semi disj:
		%
		%	model_det goal:
		%		<Goal ; Goals>
		%	===>
		%		<Goal>
		%		/* <Goals> will never be reached */
		%
		%	model_semi goal:
		%		<Goal ; Goals>
		%	===>
		%	{
		%		MR_bool succeeded;
		%
		%		<succeeded = Goal>;
		%		if (!succeeded) {
		%			<Goals>;
		%		}
		%	}
		%
		First = _ - FirstGoalInfo,
		goal_info_get_code_model(FirstGoalInfo, FirstCodeModel),
		(
			FirstCodeModel = model_det,
			ml_gen_goal(model_det, First, Decls, Statements, !Info)
		;
			FirstCodeModel = model_semi,
			ml_gen_goal(model_semi, First,
				FirstDecls, FirstStatements, !Info),
			ml_gen_test_success(!.Info, Succeeded),
			ml_gen_disj(Rest, CodeModel, Context,
				RestDecls, RestStatements, !Info),
			RestStatement = ml_gen_block(RestDecls,
				RestStatements, Context),
			IfStmt = if_then_else(unop(std_unop(not), Succeeded),
						RestStatement, no),
			IfStatement = mlds__statement(IfStmt,
				mlds__make_context(Context)),
			Decls = FirstDecls,
			Statements = list__append(FirstStatements,
				[IfStatement])
		;
			FirstCodeModel = model_non,
			% simplify.m should get wrap commits around these
			error("model_non disj in model_det disjunction")
		)
	).

%-----------------------------------------------------------------------------%
%
% Code for handling attributes
%

:- func attributes_to_mlds_attributes(module_info, list(hlds_pred__attribute))
	= list(mlds__attribute).

attributes_to_mlds_attributes(ModuleInfo, Attrs) =
	list__map(attribute_to_mlds_attribute(ModuleInfo), Attrs).

:- func attribute_to_mlds_attribute(module_info, hlds_pred__attribute)
	= mlds__attribute.

attribute_to_mlds_attribute(ModuleInfo, custom(Type)) =
	custom(mercury_type_to_mlds_type(ModuleInfo, Type)).

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

:- func this_file = string.

this_file = "ml_code_gen.m".

:- end_module ml_code_gen.

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