Reduce the dependence of earlier parts of the compiler on the later ones.

Estimated hours taken: 4
Branches: main

Reduce the dependence of earlier parts of the compiler on the later ones.
Unnecessary import_module declarations in top level modules such as hlds.m
cause unnecessary recompilations when adding new types in later modules,
such as submodules of ll_backend.m. This change reduces the number of such
unnecessary imports.

There are no changes in algorithms, only functionality being moved around.

compiler/code_model.m:
	Change this module from being a submodule of backend_libs.m to being a
	submodule of hlds.m, since nothing in it is dependent on any backend.

compiler/arg_info.m:
compiler/code_util.m:
	Change arg_info.m from being a submodule of ll_backend.m to being a
	submodule of hlds.m, since most of it is applicable to all current
	and foreseeable backends. Move the one exported predicate that is
	ll_backend dependent, and its support predicates, to code_util.m.

compiler/backend_libs.m:
compiler/ll_backend.m:
compiler/hlds.m:
	Update include_module declarations in accordance with the above.

compiler/prog_data.m:
compiler/term_util.m:
	Instead of defining two separate types for holding argument size and
	termination information, one including HLDS-specific information (in
	term_util.m) and one not (in prog_data.m), use a polymorphic type
	defined in prog_data.m and two monomorphic instances.

compiler/termination.m:
compiler/mercury_to_mercury.m:
	Change the predicates for writing out argument size and termination
	information to handle the polymorphic type (we don't need special
	handling of the monomorphic versions), and move them from termination.m
	to mercury_to_mercury.m, since this allows us to avoid some
	undesirable dependencies.

compiler/base_typeclass_info.m:
compiler/hlds_code_util.m:
	Move the predicate make_instance_string from base_typeclass_info.m
	to hlds_code_util.m, again because it allows us to remove some
	undesirable dependencies.

compiler/top_level.m:
compiler/backend_libs.m:
compiler/check_hlds.m:
compiler/hlds.m:
compiler/ll_backend.m:
compiler/parse_tree.m:
compiler/transform_hlds.m:
	Delete some import_module declarations of other top level modules
	in these top level modules. Some imports were totally unnecessary.
	Some imports were useful in only a small minority of submodules;
	those submodules now import the necessary top level modules directly.

	Move remaining import_module declarations to the implementation section
	where this is feasible.

	Where we still need to import modules we ideally shouldn't, note why.

compiler/*.m:
	Update imports of code_util and arg_info.

	In some cases, import top level modules no longer imported by the
	parent module.

	In some cases, delete unnecessary imports.

compiler/add_heap_ops.m

@@ -1,5 +1,5 @@
 %-----------------------------------------------------------------------------%
-% Copyright (C) 2000-2003 The University of Melbourne.
+% Copyright (C) 2000-2004 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.
 %-----------------------------------------------------------------------------%
@@ -39,8 +39,8 @@
 
 :- implementation.
 
-:- import_module backend_libs__code_model.
 :- import_module check_hlds__type_util.
+:- import_module hlds__code_model.
 :- import_module hlds__goal_form.
 :- import_module hlds__goal_util.
 :- import_module hlds__hlds_data.