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Branches: main 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.
This directory holds the trace subsystem, i.e. the part of the Mercury debugger that is written in C code. Notes on interfacing with other subsystems ------------------------------------------ If tracing is enabled, the compiler includes calls to MR_trace() in the generated C code. The trace subsystem in this directory is therefore called directly from Mercury code, via MR_trace() in runtime/mercury_trace_base.c. One of the first things it does is to save the original values of the Mercury registers in a variable called `saved_regs'. The reason it needs to do this is that the code here may modify registers, e.g. by allocating memory using incr_hp or by calling Mercury code. Once the original values of the registers have been saved, the trace subsystem is free to modify the Mercury registers. So for all code in this directory, the usual convention is that the original values of the Mercury registers are in `saved_regs', while the current (scratch) values for the normal non-transient Mercury registers etc. are in their normal locations, not in the fake_reg copies, and the transient (register window) registers, if any, are in the fake_reg copies. Any code which uses macros such as incr_hp(), list_cons(), make_aligned_string(), etc. that modify the heap pointer must call restore_transient_regs() beforehand and must call save_transient_regs() afterwards. The simplest way to do this is to use the macro MR_TRACE_USE_HP() in trace/mercury_trace_util.h. The tracer may invoke Mercury code defined in the browser or library directories if that code is exported to C using `pragma export'. But any calls from functions here to code defined in Mercury and exported using `pragma export', i.e. functions starting with `ML_' prefixes, must be preceded by a call to save_registers() and followed by a call to restore_registers(). The simplest way to do this is to use the macro MR_TRACE_CALL_MERCURY() in trace/mercury_trace_util.h.