Pack consecutive enumeration arguments in discriminated union types into a

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Pack consecutive enumeration arguments in discriminated union types into a
single word to reduce cell sizes.  Argument packing is only enabled on C
back-ends with low-level data, and reordering arguments to improve
opportunities for packing is not yet attempted.  The RTTI implementations for
other back-ends will need to be updated, but that is best left until after any
argument reordering change.

Modules which import abstract enumeration types are notified so by writing
declarations of the form:

	:- type foo where type_is_abstract_enum(NumBits).

into the interface file for the module which defines the type.


compiler/prog_data.m:
	Add an `arg_width' argument to constructor arguments.

	Replace `is_solver_type' by `abstract_type_details', with an extra
	option for abstract exported enumeration types.

compiler/handle_options.m:
compiler/options.m:
	Add an internal option `--allow-argument-packing'.

compiler/make_hlds_passes.m:
	Determine whether and how to pack enumeration arguments, updating the
	`arg_width' fields of constructor arguments before constructors are
	added to the HLDS.

compiler/mercury_to_mercury.m:
compiler/modules.m:
	Write `where type_is_abstract_enum(NumBits)' to interface files
	for abstract exported enumeration types.

compiler/prog_io_type_defn.m:
	Parse `where type_is_abstract_enum(NumBits)' attributes on type
	definitions.

compiler/arg_pack.m:
compiler/backend_libs.m:
	Add a new module.  This mainly contains a predicate which packs rvals
	according to arg_widths, which is used by both LLDS and MLDS back-ends.

compiler/ml_unify_gen.m:
compiler/unify_gen.m:
	Take argument packing into account when generating code for
	constructions and deconstructions.  Only a relatively small part of the
	compiler actually needs to understand argument packing.  The rest works
	at the HLDS level with constructor arguments and variables, or at the
	LLDS and MLDS levels with structure fields.

compiler/code_info.m:
compiler/var_locn.m:
	Add assign_field_lval_expr_to_var and
	var_locn_assign_field_lval_expr_to_var.

	Allow more kinds of rvals in assign_cell_arg.  I do not know why it was
	previously restricted, except that the other kinds of rvals were not
	encountered as cell arguments before.

compiler/mlds.m:
	We can now rely on the compiler to pack arguments in the
	mlds_decl_flags type instead of doing it manually.  A slight downside
	is that though the type is packed down to a single word cell, it will
	still incur a memory allocation per cell.  However, I did not notice
	any difference in compiler speed.

compiler/rtti.m:
compiler/rtti_out.m:
	Add and output a new field for MR_DuFunctorDesc instances, which, if
	any arguments are packed, points to an array of MR_DuArgLocn.  Each
	array element describes the offset in the cell at which the argument's
	value is held, and which bits of the word it occupies.  In the more
	common case where no arguments are packed, the new field is simply
	null.

compiler/rtti_to_mlds.m:
	Generate the new field to MR_DuFunctorDesc.

compiler/structure_reuse.direct.choose_reuse.m:
	For now, prevent structure reuse reusing a dead cell which has a
	different constructor to the new cell.  The code to determine whether a
	dead cell will hold the arguments of a new cell with a different
	constructor will need to be updated to account for argument packing.

compiler/type_ctor_info.m:
	Bump RTTI version number.

	Conform to changes.

compiler/add_type.m:
compiler/check_typeclass.m:
compiler/equiv_type.m:
compiler/equiv_type_hlds.m:
compiler/erl_rtti.m:
compiler/hlds_data.m:
compiler/hlds_out_module.m:
compiler/intermod.m:
compiler/make_tags.m:
compiler/mlds_to_gcc.m:
compiler/opt_debug.m:
compiler/prog_type.m:
compiler/recompilation.check.m:
compiler/recompilation.version.m:
compiler/special_pred.m:
compiler/type_constraints.m:
compiler/type_util.m:
compiler/unify_proc.m:
compiler/xml_documentation.m:
	Conform to changes.

	Reduce code duplication in classify_type_defn.

compiler/hlds_goal.m:
	Clarify a comment.

library/construct.m:
	Make `construct' pack arguments when necessary.

	Remove an old RTTI version number check as recommended in
	mercury_grade.h.

library/store.m:
	Deal with packed arguments in this module.

runtime/mercury_grade.h:
	Bump binary compatibility version number.

runtime/mercury_type_info.c:
runtime/mercury_type_info.h:
	Bump RTTI version number.

	Add MR_DuArgLocn structure definition.

	Add a macro to unpack an argument as described by MR_DuArgLocn.

	Add a function to determine a cell's size, since the number of
	arguments is no longer correct.

runtime/mercury_deconstruct.c:
runtime/mercury_deconstruct.h:
runtime/mercury_deconstruct_macros.h:
runtime/mercury_ml_arg_body.h:
runtime/mercury_ml_expand_body.h:
	Deal with packed arguments when deconstructing.

	Remove an old RTTI version number check as recommended in
	mercury_grade.h.

runtime/mercury_deep_copy_body.h:
	Deal with packed arguments when copying.

runtime/mercury_table_type_body.h:
	Deal with packed arguments in tabling.

runtime/mercury_dotnet.cs.in:
	Add DuArgLocn field to DuFunctorDesc. Argument packing is not enabled
	for the C# back-end yet so this is unused.

trace/mercury_trace_vars.c:
	Deal with packed arguments in MR_select_specified_subterm,
	use for the `hold' command.

java/runtime/DuArgLocn.java:
java/runtime/DuFunctorDesc.java:
	Add DuArgLocn field to DuFunctorDesc. Argument packing is not enabled
	for the Java back-end yet so this is unused.

extras/trailed_update/tr_store.m:
	Deal with packed arguments in this module (untested).

extras/trailed_update/samples/interpreter.m:
extras/trailed_update/tr_array.m:
	Conform to argument reordering in the array, map and other modules in
	previous changes.

tests/hard_coded/Mercury.options:
tests/hard_coded/Mmakefile:
tests/hard_coded/lco_pack_args.exp:
tests/hard_coded/lco_pack_args.m:
tests/hard_coded/pack_args.exp:
tests/hard_coded/pack_args.m:
tests/hard_coded/pack_args_copy.exp:
tests/hard_coded/pack_args_copy.m:
tests/hard_coded/pack_args_intermod1.exp:
tests/hard_coded/pack_args_intermod1.m:
tests/hard_coded/pack_args_intermod2.m:
tests/hard_coded/pack_args_reuse.exp:
tests/hard_coded/pack_args_reuse.m:
tests/hard_coded/store_ref.exp:
tests/hard_coded/store_ref.m:
tests/invalid/Mmakefile:
tests/invalid/where_abstract_enum.err_exp:
tests/invalid/where_abstract_enum.m:
tests/tabling/Mmakefile:
tests/tabling/pack_args_memo.exp:
tests/tabling/pack_args_memo.m:
	Add new test cases.

tests/hard_coded/deconstruct_arg.exp:
tests/hard_coded/deconstruct_arg.exp2:
tests/hard_coded/deconstruct_arg.m:
	Add constructors with packed arguments to these cases.

tests/invalid/where_direct_arg.err_exp:
	Update expected output.

runtime/mercury_deconstruct.c

@@ -85,6 +85,7 @@ static  MR_ConstString  MR_expand_type_name(MR_TypeCtorInfo tci, MR_bool);
 MR_bool
 MR_arg(MR_TypeInfo type_info, MR_Word *term_ptr, int arg_index,
     MR_TypeInfo *arg_type_info_ptr, MR_Word **arg_ptr,
+    const MR_DuArgLocn **arg_locn_ptr,
     MR_noncanon_handling noncanon)
 {
     MR_Expand_Chosen_Arg_Only_Info  expand_info;
@@ -92,10 +93,11 @@ MR_arg(MR_TypeInfo type_info, MR_Word *term_ptr, int arg_index,
     MR_expand_chosen_arg_only(type_info, term_ptr, noncanon, arg_index,
             &expand_info);
 
-        /* Check range */
+    /* Check range. */
     if (expand_info.chosen_index_exists) {
         *arg_type_info_ptr = expand_info.chosen_type_info;
         *arg_ptr = expand_info.chosen_value_ptr;
+        *arg_locn_ptr = expand_info.chosen_arg_locn;
         return MR_TRUE;
     }
 
@@ -105,6 +107,7 @@ MR_arg(MR_TypeInfo type_info, MR_Word *term_ptr, int arg_index,
 MR_bool
 MR_named_arg(MR_TypeInfo type_info, MR_Word *term_ptr, MR_ConstString arg_name,
     MR_TypeInfo *arg_type_info_ptr, MR_Word **arg_ptr,
+    const MR_DuArgLocn **arg_locn_ptr,
     MR_noncanon_handling noncanon)
 {
     MR_Expand_Chosen_Arg_Only_Info  expand_info;
@@ -112,10 +115,11 @@ MR_named_arg(MR_TypeInfo type_info, MR_Word *term_ptr, MR_ConstString arg_name,
     MR_expand_named_arg_only(type_info, term_ptr, noncanon, arg_name,
             &expand_info);
 
-        /* Check range */
+    /* Check range. */
     if (expand_info.chosen_index_exists) {
         *arg_type_info_ptr = expand_info.chosen_type_info;
         *arg_ptr = expand_info.chosen_value_ptr;
+        *arg_locn_ptr = expand_info.chosen_arg_locn;
         return MR_TRUE;
     }