separate_compiler: always compile stub of methods to avoid unresolved symbols

[nit.git] / src / compiler / separate_compiler.nit

# This file is part of NIT ( http://www.nitlanguage.org ).
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

# Separate compilation of a Nit program
module separate_compiler

import abstract_compiler
import coloring
import rapid_type_analysis

# Add separate compiler specific options
redef class ToolContext
        # --separate
        var opt_separate = new OptionBool("Use separate compilation", "--separate")
        # --no-inline-intern
        var opt_no_inline_intern = new OptionBool("Do not inline call to intern methods", "--no-inline-intern")
        # --no-union-attribute
        var opt_no_union_attribute = new OptionBool("Put primitive attibutes in a box instead of an union", "--no-union-attribute")
        # --no-shortcut-equate
        var opt_no_shortcut_equate = new OptionBool("Always call == in a polymorphic way", "--no-shortcut-equal")
        # --no-tag-primitives
        var opt_no_tag_primitives = new OptionBool("Use only boxes for primitive types", "--no-tag-primitives")

        # --colors-are-symbols
        var opt_colors_are_symbols = new OptionBool("Store colors as symbols (link-boost)", "--colors-are-symbols")
        # --trampoline-call
        var opt_trampoline_call = new OptionBool("Use an indirection when calling", "--trampoline-call")
        # --guard-call
        var opt_guard_call = new OptionBool("Guard VFT calls with a direct call", "--guard-call")
        # --substitute-monomorph
        var opt_substitute_monomorph = new OptionBool("Replace monomorph trampoline with direct call (link-boost)", "--substitute-monomorph")
        # --link-boost
        var opt_link_boost = new OptionBool("Enable all link-boost optimizations", "--link-boost")

        # --inline-coloring-numbers
        var opt_inline_coloring_numbers = new OptionBool("Inline colors and ids (semi-global)", "--inline-coloring-numbers")
        # --inline-some-methods
        var opt_inline_some_methods = new OptionBool("Allow the separate compiler to inline some methods (semi-global)", "--inline-some-methods")
        # --direct-call-monomorph
        var opt_direct_call_monomorph = new OptionBool("Allow the separate compiler to direct call monomorph sites (semi-global)", "--direct-call-monomorph")
        # --direct-call-monomorph0
        var opt_direct_call_monomorph0 = new OptionBool("Allow the separate compiler to direct call monomorph sites (semi-global)", "--direct-call-monomorph0")
        # --skip-dead-methods
        var opt_skip_dead_methods = new OptionBool("Do not compile dead methods (semi-global)", "--skip-dead-methods")
        # --semi-global
        var opt_semi_global = new OptionBool("Enable all semi-global optimizations", "--semi-global")
        # --no-colo-dead-methods
        var opt_colo_dead_methods = new OptionBool("Force colorization of dead methods", "--colo-dead-methods")
        # --tables-metrics
        var opt_tables_metrics = new OptionBool("Enable static size measuring of tables used for vft, typing and resolution", "--tables-metrics")
        # --type-poset
        var opt_type_poset = new OptionBool("Build a poset of types to create more condensed tables.", "--type-poset")

        redef init
        do
                super
                self.option_context.add_option(self.opt_separate)
                self.option_context.add_option(self.opt_no_inline_intern)
                self.option_context.add_option(self.opt_no_union_attribute)
                self.option_context.add_option(self.opt_no_shortcut_equate)
                self.option_context.add_option(self.opt_no_tag_primitives)
                self.option_context.add_option(opt_colors_are_symbols, opt_trampoline_call, opt_guard_call, opt_direct_call_monomorph0, opt_substitute_monomorph, opt_link_boost)
                self.option_context.add_option(self.opt_inline_coloring_numbers, opt_inline_some_methods, opt_direct_call_monomorph, opt_skip_dead_methods, opt_semi_global)
                self.option_context.add_option(self.opt_colo_dead_methods)
                self.option_context.add_option(self.opt_tables_metrics)
                self.option_context.add_option(self.opt_type_poset)
        end

        redef fun process_options(args)
        do
                super

                var tc = self
                if tc.opt_semi_global.value then
                        tc.opt_inline_coloring_numbers.value = true
                        tc.opt_inline_some_methods.value = true
                        tc.opt_direct_call_monomorph.value = true
                        tc.opt_skip_dead_methods.value = true
                end
                if tc.opt_link_boost.value then
                        tc.opt_colors_are_symbols.value = true
                        tc.opt_substitute_monomorph.value = true
                end
                if tc.opt_substitute_monomorph.value then
                        tc.opt_trampoline_call.value = true
                end
        end

        var separate_compiler_phase = new SeparateCompilerPhase(self, null)
end

class SeparateCompilerPhase
        super Phase
        redef fun process_mainmodule(mainmodule, given_mmodules) do
                if not toolcontext.opt_separate.value then return

                var modelbuilder = toolcontext.modelbuilder
                var analysis = modelbuilder.do_rapid_type_analysis(mainmodule)
                modelbuilder.run_separate_compiler(mainmodule, analysis)
        end
end

redef class ModelBuilder
        fun run_separate_compiler(mainmodule: MModule, runtime_type_analysis: nullable RapidTypeAnalysis)
        do
                var time0 = get_time
                self.toolcontext.info("*** GENERATING C ***", 1)

                var compiler = new SeparateCompiler(mainmodule, self, runtime_type_analysis)
                compiler.do_compilation
                compiler.display_stats

                var time1 = get_time
                self.toolcontext.info("*** END GENERATING C: {time1-time0} ***", 2)
                write_and_make(compiler)
        end

        # Count number of invocations by VFT
        private var nb_invok_by_tables = 0
        # Count number of invocations by direct call
        private var nb_invok_by_direct = 0
        # Count number of invocations by inlining
        private var nb_invok_by_inline = 0
end

# Singleton that store the knowledge about the separate compilation process
class SeparateCompiler
        super AbstractCompiler

        redef type VISITOR: SeparateCompilerVisitor

        # The result of the RTA (used to know live types and methods)
        var runtime_type_analysis: nullable RapidTypeAnalysis

        private var undead_types: Set[MType] = new HashSet[MType]
        private var live_unresolved_types: Map[MClassDef, Set[MType]] = new HashMap[MClassDef, HashSet[MType]]

        private var type_ids: Map[MType, Int] is noinit
        private var type_colors: Map[MType, Int] is noinit
        private var opentype_colors: Map[MType, Int] is noinit

        init do
                var file = new_file("nit.common")
                self.header = new CodeWriter(file)
                self.compile_box_kinds
        end

        redef fun do_compilation
        do
                var compiler = self
                compiler.compile_header

                var c_name = mainmodule.c_name

                # compile class structures
                modelbuilder.toolcontext.info("Property coloring", 2)
                compiler.new_file("{c_name}.classes")
                compiler.do_property_coloring
                compiler.compile_class_infos
                for m in mainmodule.in_importation.greaters do
                        for mclass in m.intro_mclasses do
                                #if mclass.kind == abstract_kind or mclass.kind == interface_kind then continue
                                compiler.compile_class_to_c(mclass)
                        end
                end

                # The main function of the C
                compiler.new_file("{c_name}.main")
                compiler.compile_nitni_global_ref_functions
                compiler.compile_main_function
                compiler.compile_finalizer_function
                compiler.link_mmethods

                # compile methods
                for m in mainmodule.in_importation.greaters do
                        modelbuilder.toolcontext.info("Generate C for module {m.full_name}", 2)
                        compiler.new_file("{m.c_name}.sep")
                        compiler.compile_module_to_c(m)
                end

                # compile live & cast type structures
                modelbuilder.toolcontext.info("Type coloring", 2)
                compiler.new_file("{c_name}.types")
                compiler.compile_types
        end

        # Color and compile type structures and cast information
        fun compile_types
        do
                var compiler = self

                var mtypes = compiler.do_type_coloring
                for t in mtypes do
                        compiler.compile_type_to_c(t)
                end
                # compile remaining types structures (useless but needed for the symbol resolution at link-time)
                for t in compiler.undead_types do
                        if mtypes.has(t) then continue
                        compiler.compile_type_to_c(t)
                end

        end

        redef fun compile_header_structs do
                self.header.add_decl("typedef void(*nitmethod_t)(void); /* general C type representing a Nit method. */")
                self.compile_header_attribute_structs
                self.header.add_decl("struct class \{ int box_kind; nitmethod_t vft[]; \}; /* general C type representing a Nit class. */")

                # With resolution_table_table, all live type resolution are stored in a big table: resolution_table
                self.header.add_decl("struct type \{ int id; const char *name; int color; short int is_nullable; const struct types *resolution_table; int table_size; int type_table[]; \}; /* general C type representing a Nit type. */")
                self.header.add_decl("struct instance \{ const struct type *type; const struct class *class; nitattribute_t attrs[]; \}; /* general C type representing a Nit instance. */")
                self.header.add_decl("struct types \{ int dummy; const struct type *types[]; \}; /* a list types (used for vts, fts and unresolved lists). */")
                self.header.add_decl("typedef struct instance val; /* general C type representing a Nit instance. */")

                if not modelbuilder.toolcontext.opt_no_tag_primitives.value then
                        self.header.add_decl("extern const struct class *class_info[];")
                        self.header.add_decl("extern const struct type *type_info[];")
                end
        end

        fun compile_header_attribute_structs
        do
                if modelbuilder.toolcontext.opt_no_union_attribute.value then
                        self.header.add_decl("typedef void* nitattribute_t; /* general C type representing a Nit attribute. */")
                else
                        self.header.add_decl("typedef union \{")
                        self.header.add_decl("void* val;")
                        for c, v in self.box_kinds do
                                var t = c.mclass_type

                                # `Pointer` reuse the `val` field
                                if t.mclass.name == "Pointer" then continue

                                self.header.add_decl("{t.ctype_extern} {t.ctypename};")
                        end
                        self.header.add_decl("\} nitattribute_t; /* general C type representing a Nit attribute. */")
                end
        end

        fun compile_box_kinds
        do
                # Collect all bas box class
                # FIXME: this is not completely fine with a separate compilation scheme
                for classname in ["Int", "Bool", "Byte", "Char", "Float", "NativeString", "Pointer"] do
                        var classes = self.mainmodule.model.get_mclasses_by_name(classname)
                        if classes == null then continue
                        assert classes.length == 1 else print classes.join(", ")
                        self.box_kinds[classes.first] = self.box_kinds.length + 1
                end
        end

        var box_kinds = new HashMap[MClass, Int]

        fun box_kind_of(mclass: MClass): Int
        do
                #var pointer_type = self.mainmodule.pointer_type
                #if mclass.mclass_type.ctype == "val*" or mclass.mclass_type.is_subtype(self.mainmodule, mclass.mclass_type pointer_type) then
                if mclass.mclass_type.ctype_extern == "val*" then
                        return 0
                else if mclass.kind == extern_kind and mclass.name != "NativeString" then
                        return self.box_kinds[self.mainmodule.pointer_type.mclass]
                else
                        return self.box_kinds[mclass]
                end

        end

        fun compile_color_consts(colors: Map[Object, Int]) do
                var v = new_visitor
                for m, c in colors do
                        compile_color_const(v, m, c)
                end
        end

        fun compile_color_const(v: SeparateCompilerVisitor, m: Object, color: Int) do
                if color_consts_done.has(m) then return
                if m isa MEntity then
                        if modelbuilder.toolcontext.opt_inline_coloring_numbers.value then
                                self.provide_declaration(m.const_color, "#define {m.const_color} {color}")
                        else if not modelbuilder.toolcontext.opt_colors_are_symbols.value or not v.compiler.target_platform.supports_linker_script then
                                self.provide_declaration(m.const_color, "extern const int {m.const_color};")
                                v.add("const int {m.const_color} = {color};")
                        else
                                # The color 'C' is the ``address'' of a false static variable 'XC'
                                self.provide_declaration(m.const_color, "#define {m.const_color} ((long)&X{m.const_color})\nextern const void X{m.const_color};")
                                if color == -1 then color = 0 # Symbols cannot be negative, so just use 0 for dead things
                                # Teach the linker that the address of 'XC' is `color`.
                                linker_script.add("X{m.const_color} = {color};")
                        end
                else
                        abort
                end
                color_consts_done.add(m)
        end

        private var color_consts_done = new HashSet[Object]

        # The conflict graph of classes used for coloration
        var class_conflict_graph: POSetConflictGraph[MClass] is noinit

        # colorize classe properties
        fun do_property_coloring do

                var rta = runtime_type_analysis

                # Class graph
                var mclasses = mainmodule.flatten_mclass_hierarchy
                class_conflict_graph = mclasses.to_conflict_graph

                # Prepare to collect elements to color and build layout with
                var mmethods = new HashMap[MClass, Set[PropertyLayoutElement]]
                var mattributes = new HashMap[MClass, Set[MAttribute]]

                # The dead methods and super-call, still need to provide a dead color symbol
                var dead_methods = new Array[PropertyLayoutElement]

                for mclass in mclasses do
                        mmethods[mclass] = new HashSet[PropertyLayoutElement]
                        mattributes[mclass] = new HashSet[MAttribute]
                end

                # Pre-collect known live things
                if rta != null then
                        for m in rta.live_methods do
                                mmethods[m.intro_mclassdef.mclass].add m
                        end
                        for m in rta.live_super_sends do
                                var mclass = m.mclassdef.mclass
                                mmethods[mclass].add m
                        end
                end

                for m in mainmodule.in_importation.greaters do for cd in m.mclassdefs do
                        var mclass = cd.mclass
                        # Collect methods ad attributes
                        for p in cd.intro_mproperties do
                                if p isa MMethod then
                                        if rta == null then
                                                mmethods[mclass].add p
                                        else if not rta.live_methods.has(p) then
                                                dead_methods.add p
                                        end
                                else if p isa MAttribute then
                                        mattributes[mclass].add p
                                end
                        end

                        # Collect all super calls (dead or not)
                        for mpropdef in cd.mpropdefs do
                                if not mpropdef isa MMethodDef then continue
                                if mpropdef.has_supercall then
                                        if rta == null then
                                                mmethods[mclass].add mpropdef
                                        else if not rta.live_super_sends.has(mpropdef) then
                                                dead_methods.add mpropdef
                                        end
                                end
                        end
                end

                # methods coloration
                var meth_colorer = new POSetGroupColorer[MClass, PropertyLayoutElement](class_conflict_graph, mmethods)
                var method_colors = meth_colorer.colors
                compile_color_consts(method_colors)

                # give null color to dead methods and supercalls
                for mproperty in dead_methods do compile_color_const(new_visitor, mproperty, -1)

                # attribute coloration
                var attr_colorer = new POSetGroupColorer[MClass, MAttribute](class_conflict_graph, mattributes)
                var attr_colors = attr_colorer.colors#ize(poset, mattributes)
                compile_color_consts(attr_colors)

                # Build method and attribute tables
                method_tables = new HashMap[MClass, Array[nullable MPropDef]]
                attr_tables = new HashMap[MClass, Array[nullable MProperty]]
                for mclass in mclasses do
                        if not mclass.has_new_factory and (mclass.kind == abstract_kind or mclass.kind == interface_kind) then continue
                        if rta != null and not rta.live_classes.has(mclass) then continue

                        var mtype = mclass.intro.bound_mtype

                        # Resolve elements in the layout to get the final table
                        var meth_layout = meth_colorer.build_layout(mclass)
                        var meth_table = new Array[nullable MPropDef].with_capacity(meth_layout.length)
                        method_tables[mclass] = meth_table
                        for e in meth_layout do
                                if e == null then
                                        meth_table.add null
                                else if e isa MMethod then
                                        # Standard method call of `e`
                                        meth_table.add e.lookup_first_definition(mainmodule, mtype)
                                else if e isa MMethodDef then
                                        # Super-call in the methoddef `e`
                                        meth_table.add e.lookup_next_definition(mainmodule, mtype)
                                else
                                        abort
                                end
                        end

                        # Do not need to resolve attributes as only the position is used
                        attr_tables[mclass] = attr_colorer.build_layout(mclass)
                end


        end

        # colorize live types of the program
        private fun do_type_coloring: Collection[MType] do
                # Collect types to colorize
                var live_types = runtime_type_analysis.live_types
                var live_cast_types = runtime_type_analysis.live_cast_types

                var res = new HashSet[MType]
                res.add_all live_types
                res.add_all live_cast_types

                if modelbuilder.toolcontext.opt_type_poset.value then
                        # Compute colors with a type poset
                        var poset = poset_from_mtypes(live_types, live_cast_types)
                        var colorer = new POSetColorer[MType]
                        colorer.colorize(poset)
                        type_ids = colorer.ids
                        type_colors = colorer.colors
                        type_tables = build_type_tables(poset)
                else
                        # Compute colors using the class poset
                        # Faster to compute but the number of holes can degenerate
                        compute_type_test_layouts(live_types, live_cast_types)

                        type_ids = new HashMap[MType, Int]
                        for x in res do type_ids[x] = type_ids.length + 1
                end

                # VT and FT are stored with other unresolved types in the big resolution_tables
                self.compute_resolution_tables(live_types)

                return res
        end

        private fun poset_from_mtypes(mtypes, cast_types: Set[MType]): POSet[MType] do
                var poset = new POSet[MType]

                # Instead of doing the full matrix mtypes X cast_types,
                # a grouping is done by the base classes of the type so
                # that we compare only types whose base classes are in inheritance.

                var mtypes_by_class = new MultiHashMap[MClass, MType]
                for e in mtypes do
                        var c = e.undecorate.as(MClassType).mclass
                        mtypes_by_class[c].add(e)
                        poset.add_node(e)
                end

                var casttypes_by_class = new MultiHashMap[MClass, MType]
                for e in cast_types do
                        var c = e.undecorate.as(MClassType).mclass
                        casttypes_by_class[c].add(e)
                        poset.add_node(e)
                end

                for c1, ts1 in mtypes_by_class do
                        for c2 in c1.in_hierarchy(mainmodule).greaters do
                                var ts2 = casttypes_by_class[c2]
                                for e in ts1 do
                                        for o in ts2 do
                                                if e == o then continue
                                                if e.is_subtype(mainmodule, null, o) then
                                                        poset.add_edge(e, o)
                                                end
                                        end
                                end
                        end
                end
                return poset
        end

        # Build type tables
        fun build_type_tables(mtypes: POSet[MType]): Map[MType, Array[nullable MType]] do
                var tables = new HashMap[MType, Array[nullable MType]]
                for mtype in mtypes do
                        var table = new Array[nullable MType]
                        for sup in mtypes[mtype].greaters do
                                var color = type_colors[sup]
                                if table.length <= color then
                                        for i in [table.length .. color[ do
                                                table[i] = null
                                        end
                                end
                                table[color] = sup
                        end
                        tables[mtype] = table
                end
                return tables
        end


        private fun compute_type_test_layouts(mtypes: Set[MClassType], cast_types: Set[MType]) do
                # Group cast_type by their classes
                var bucklets = new HashMap[MClass, Set[MType]]
                for e in cast_types do
                        var c = e.undecorate.as(MClassType).mclass
                        if not bucklets.has_key(c) then
                                bucklets[c] = new HashSet[MType]
                        end
                        bucklets[c].add(e)
                end

                # Colorize cast_types from the class hierarchy
                var colorer = new POSetGroupColorer[MClass, MType](class_conflict_graph, bucklets)
                type_colors = colorer.colors

                var layouts = new HashMap[MClass, Array[nullable MType]]
                for c in runtime_type_analysis.live_classes do
                        layouts[c] = colorer.build_layout(c)
                end

                # Build the table for each live type
                for t in mtypes do
                        # A live type use the layout of its class
                        var c = t.mclass
                        var layout = layouts[c]
                        var table = new Array[nullable MType].with_capacity(layout.length)
                        type_tables[t] = table

                        # For each potential super-type in the layout
                        for sup in layout do
                                if sup == null then
                                        table.add null
                                else if t.is_subtype(mainmodule, null, sup) then
                                        table.add sup
                                else
                                        table.add null
                                end
                        end
                end
        end

        # resolution_tables is used to perform a type resolution at runtime in O(1)
        private fun compute_resolution_tables(mtypes: Set[MType]) do
                # During the visit of the body of classes, live_unresolved_types are collected
                # and associated to
                # Collect all live_unresolved_types (visited in the body of classes)

                # Determinate fo each livetype what are its possible requested anchored types
                var mtype2unresolved = new HashMap[MClass, Set[MType]]
                for mtype in self.runtime_type_analysis.live_types do
                        var mclass = mtype.mclass
                        var set = mtype2unresolved.get_or_null(mclass)
                        if set == null then
                                set = new HashSet[MType]
                                mtype2unresolved[mclass] = set
                        end
                        for cd in mtype.collect_mclassdefs(self.mainmodule) do
                                if self.live_unresolved_types.has_key(cd) then
                                        set.add_all(self.live_unresolved_types[cd])
                                end
                        end
                end

                # Compute the table layout with the prefered method
                var colorer = new BucketsColorer[MClass, MType]

                opentype_colors = colorer.colorize(mtype2unresolved)
                resolution_tables = self.build_resolution_tables(self.runtime_type_analysis.live_types, mtype2unresolved)

                # Compile a C constant for each collected unresolved type.
                # Either to a color, or to -1 if the unresolved type is dead (no live receiver can require it)
                var all_unresolved = new HashSet[MType]
                for t in self.live_unresolved_types.values do
                        all_unresolved.add_all(t)
                end
                var all_unresolved_types_colors = new HashMap[MType, Int]
                for t in all_unresolved do
                        if opentype_colors.has_key(t) then
                                all_unresolved_types_colors[t] = opentype_colors[t]
                        else
                                all_unresolved_types_colors[t] = -1
                        end
                end
                self.compile_color_consts(all_unresolved_types_colors)

                #print "tables"
                #for k, v in unresolved_types_tables.as(not null) do
                #       print "{k}: {v.join(", ")}"
                #end
                #print ""
        end

        fun build_resolution_tables(elements: Set[MClassType], map: Map[MClass, Set[MType]]): Map[MClassType, Array[nullable MType]] do
                var tables = new HashMap[MClassType, Array[nullable MType]]
                for mclasstype in elements do
                        var mtypes = map[mclasstype.mclass]
                        var table = new Array[nullable MType]
                        for mtype in mtypes do
                                var color = opentype_colors[mtype]
                                if table.length <= color then
                                        for i in [table.length .. color[ do
                                                table[i] = null
                                        end
                                end
                                table[color] = mtype
                        end
                        tables[mclasstype] = table
                end
                return tables
        end

        # Separately compile all the method definitions of the module
        fun compile_module_to_c(mmodule: MModule)
        do
                var old_module = self.mainmodule
                self.mainmodule = mmodule
                for cd in mmodule.mclassdefs do
                        for pd in cd.mpropdefs do
                                if not pd isa MMethodDef then continue
                                if pd.msignature == null then continue # Skip broken method
                                var rta = runtime_type_analysis
                                if modelbuilder.toolcontext.opt_skip_dead_methods.value and rta != null and not rta.live_methoddefs.has(pd) then continue
                                #print "compile {pd} @ {cd} @ {mmodule}"
                                var r = pd.separate_runtime_function
                                r.compile_to_c(self)
                                var r2 = pd.virtual_runtime_function
                                if r2 != r then r2.compile_to_c(self)

                                # Generate trampolines
                                if modelbuilder.toolcontext.opt_trampoline_call.value then
                                        r2.compile_trampolines(self)
                                end
                        end
                end
                self.mainmodule = old_module
        end

        # Process all introduced methods and compile some linking information (if needed)
        fun link_mmethods
        do
                if not modelbuilder.toolcontext.opt_substitute_monomorph.value and not modelbuilder.toolcontext.opt_guard_call.value then return

                for mmodule in mainmodule.in_importation.greaters do
                        for cd in mmodule.mclassdefs do
                                for m in cd.intro_mproperties do
                                        if not m isa MMethod then continue
                                        link_mmethod(m)
                                end
                        end
                end
        end

        # Compile some linking information (if needed)
        fun link_mmethod(m: MMethod)
        do
                var n2 = "CALL_" + m.const_color

                # Replace monomorphic call by a direct call to the virtual implementation
                var md = is_monomorphic(m)
                if md != null then
                        linker_script.add("{n2} = {md.virtual_runtime_function.c_name};")
                end

                # If opt_substitute_monomorph then a trampoline is used, else a weak symbol is used
                if modelbuilder.toolcontext.opt_guard_call.value then
                        var r = m.intro.virtual_runtime_function
                        provide_declaration(n2, "{r.c_ret} {n2}{r.c_sig} __attribute__((weak));")
                end
        end

        # The single mmethodef called in case of monomorphism.
        # Returns nul if dead or polymorphic.
        fun is_monomorphic(m: MMethod): nullable MMethodDef
        do
                var rta = runtime_type_analysis
                if rta == null then
                        # Without RTA, monomorphic means alone (uniq name)
                        if m.mpropdefs.length == 1 then
                                return m.mpropdefs.first
                        else
                                return null
                        end
                else
                        # With RTA, monomorphic means only live methoddef
                        var res: nullable MMethodDef = null
                        for md in m.mpropdefs do
                                if rta.live_methoddefs.has(md) then
                                        if res != null then return null
                                        res = md
                                end
                        end
                        return res
                end
        end

        # Globaly compile the type structure of a live type
        fun compile_type_to_c(mtype: MType)
        do
                assert not mtype.need_anchor
                var is_live = mtype isa MClassType and runtime_type_analysis.live_types.has(mtype)
                var is_cast_live = runtime_type_analysis.live_cast_types.has(mtype)
                var c_name = mtype.c_name
                var v = new SeparateCompilerVisitor(self)
                v.add_decl("/* runtime type {mtype} */")

                # extern const struct type_X
                self.provide_declaration("type_{c_name}", "extern const struct type type_{c_name};")

                # const struct type_X
                v.add_decl("const struct type type_{c_name} = \{")

                # type id (for cast target)
                if is_cast_live then
                        v.add_decl("{type_ids[mtype]},")
                else
                        v.add_decl("-1, /*CAST DEAD*/")
                end

                # type name
                v.add_decl("\"{mtype}\", /* class_name_string */")

                # type color (for cast target)
                if is_cast_live then
                        v.add_decl("{type_colors[mtype]},")
                else
                        v.add_decl("-1, /*CAST DEAD*/")
                end

                # is_nullable bit
                if mtype isa MNullableType then
                        v.add_decl("1,")
                else
                        v.add_decl("0,")
                end

                # resolution table (for receiver)
                if is_live then
                        var mclass_type = mtype.undecorate
                        assert mclass_type isa MClassType
                        if resolution_tables[mclass_type].is_empty then
                                v.add_decl("NULL, /*NO RESOLUTIONS*/")
                        else
                                compile_type_resolution_table(mtype)
                                v.require_declaration("resolution_table_{c_name}")
                                v.add_decl("&resolution_table_{c_name},")
                        end
                else
                        v.add_decl("NULL, /*DEAD*/")
                end

                # cast table (for receiver)
                if is_live then
                        v.add_decl("{self.type_tables[mtype].length},")
                        v.add_decl("\{")
                        for stype in self.type_tables[mtype] do
                                if stype == null then
                                        v.add_decl("-1, /* empty */")
                                else
                                        v.add_decl("{type_ids[stype]}, /* {stype} */")
                                end
                        end
                        v.add_decl("\},")
                else
                        # Use -1 to indicate dead type, the info is used by --hardening
                        v.add_decl("-1, \{\}, /*DEAD TYPE*/")
                end
                v.add_decl("\};")
        end

        fun compile_type_resolution_table(mtype: MType) do

                var mclass_type = mtype.undecorate.as(MClassType)

                # extern const struct resolution_table_X resolution_table_X
                self.provide_declaration("resolution_table_{mtype.c_name}", "extern const struct types resolution_table_{mtype.c_name};")

                # const struct fts_table_X fts_table_X
                var v = new_visitor
                v.add_decl("const struct types resolution_table_{mtype.c_name} = \{")
                v.add_decl("0, /* dummy */")
                v.add_decl("\{")
                for t in self.resolution_tables[mclass_type] do
                        if t == null then
                                v.add_decl("NULL, /* empty */")
                        else
                                # The table stores the result of the type resolution
                                # Therefore, for a receiver `mclass_type`, and a unresolved type `t`
                                # the value stored is tv.
                                var tv = t.resolve_for(mclass_type, mclass_type, self.mainmodule, true)
                                # FIXME: What typeids means here? How can a tv not be live?
                                if type_ids.has_key(tv) then
                                        v.require_declaration("type_{tv.c_name}")
                                        v.add_decl("&type_{tv.c_name}, /* {t}: {tv} */")
                                else
                                        v.add_decl("NULL, /* empty ({t}: {tv} not a live type) */")
                                end
                        end
                end
                v.add_decl("\}")
                v.add_decl("\};")
        end

        # Globally compile the table of the class mclass
        # In a link-time optimisation compiler, tables are globally computed
        # In a true separate compiler (a with dynamic loading) you cannot do this unfortnally
        fun compile_class_to_c(mclass: MClass)
        do
                var mtype = mclass.intro.bound_mtype
                var c_name = mclass.c_name

                var v = new_visitor

                var rta = runtime_type_analysis
                var is_dead = rta != null and not rta.live_classes.has(mclass)
                # While the class may be dead, some part of separately compiled code may use symbols associated to the class, so
                # in order to compile and link correctly the C code, these symbols should be declared and defined.
                var need_corpse = is_dead and mtype.is_c_primitive or mclass.kind == extern_kind or mclass.kind == enum_kind

                v.add_decl("/* runtime class {c_name}: {mclass.full_name} (dead={is_dead}; need_corpse={need_corpse})*/")

                # Build class vft
                if not is_dead or need_corpse then
                        self.provide_declaration("class_{c_name}", "extern const struct class class_{c_name};")
                        v.add_decl("const struct class class_{c_name} = \{")
                        v.add_decl("{self.box_kind_of(mclass)}, /* box_kind */")
                        v.add_decl("\{")
                        var vft = self.method_tables.get_or_null(mclass)
                        if vft != null then for i in [0 .. vft.length[ do
                                var mpropdef = vft[i]
                                if mpropdef == null then
                                        v.add_decl("NULL, /* empty */")
                                else
                                        assert mpropdef isa MMethodDef
                                        if rta != null and not rta.live_methoddefs.has(mpropdef) then
                                                v.add_decl("NULL, /* DEAD {mclass.intro_mmodule}:{mclass}:{mpropdef} */")
                                                continue
                                        end
                                        var rf = mpropdef.virtual_runtime_function
                                        v.require_declaration(rf.c_name)
                                        v.add_decl("(nitmethod_t){rf.c_name}, /* pointer to {mclass.intro_mmodule}:{mclass}:{mpropdef} */")
                                end
                        end
                        v.add_decl("\}")
                        v.add_decl("\};")
                end

                if mtype.is_c_primitive or mtype.mclass.name == "Pointer" then
                        # Is a primitive type or the Pointer class, not any other extern class

                        if mtype.is_tagged then return

                        #Build instance struct
                        self.header.add_decl("struct instance_{c_name} \{")
                        self.header.add_decl("const struct type *type;")
                        self.header.add_decl("const struct class *class;")
                        self.header.add_decl("{mtype.ctype_extern} value;")
                        self.header.add_decl("\};")

                        # Pointer is needed by extern types, live or not
                        if is_dead and mtype.mclass.name != "Pointer" then return

                        #Build BOX
                        self.provide_declaration("BOX_{c_name}", "val* BOX_{c_name}({mtype.ctype_extern});")
                        v.add_decl("/* allocate {mtype} */")
                        v.add_decl("val* BOX_{mtype.c_name}({mtype.ctype_extern} value) \{")
                        v.add("struct instance_{c_name}*res = nit_alloc(sizeof(struct instance_{c_name}));")
                        v.compiler.undead_types.add(mtype)
                        v.require_declaration("type_{c_name}")
                        v.add("res->type = &type_{c_name};")
                        v.require_declaration("class_{c_name}")
                        v.add("res->class = &class_{c_name};")
                        v.add("res->value = value;")
                        v.add("return (val*)res;")
                        v.add("\}")

                        # A Pointer class also need its constructor
                        if mtype.mclass.name != "Pointer" then return

                        v = new_visitor
                        self.provide_declaration("NEW_{c_name}", "{mtype.ctype} NEW_{c_name}(const struct type* type);")
                        v.add_decl("/* allocate {mtype} */")
                        v.add_decl("{mtype.ctype} NEW_{c_name}(const struct type* type) \{")
                        if is_dead then
                                v.add_abort("{mclass} is DEAD")
                        else
                                var res = v.new_named_var(mtype, "self")
                                res.is_exact = true
                                v.add("{res} = nit_alloc(sizeof(struct instance_{mtype.c_name}));")
                                v.add("{res}->type = type;")
                                hardening_live_type(v, "type")
                                v.require_declaration("class_{c_name}")
                                v.add("{res}->class = &class_{c_name};")
                                v.add("((struct instance_{mtype.c_name}*){res})->value = NULL;")
                                v.add("return {res};")
                        end
                        v.add("\}")
                        return
                else if mclass.name == "NativeArray" then
                        #Build instance struct
                        self.header.add_decl("struct instance_{c_name} \{")
                        self.header.add_decl("const struct type *type;")
                        self.header.add_decl("const struct class *class;")
                        # NativeArrays are just a instance header followed by a length and an array of values
                        self.header.add_decl("int length;")
                        self.header.add_decl("val* values[0];")
                        self.header.add_decl("\};")

                        #Build NEW
                        self.provide_declaration("NEW_{c_name}", "{mtype.ctype} NEW_{c_name}(int length, const struct type* type);")
                        v.add_decl("/* allocate {mtype} */")
                        v.add_decl("{mtype.ctype} NEW_{c_name}(int length, const struct type* type) \{")
                        var res = v.get_name("self")
                        v.add_decl("struct instance_{c_name} *{res};")
                        var mtype_elt = mtype.arguments.first
                        v.add("{res} = nit_alloc(sizeof(struct instance_{c_name}) + length*sizeof({mtype_elt.ctype}));")
                        v.add("{res}->type = type;")
                        hardening_live_type(v, "type")
                        v.require_declaration("class_{c_name}")
                        v.add("{res}->class = &class_{c_name};")
                        v.add("{res}->length = length;")
                        v.add("return (val*){res};")
                        v.add("\}")
                        return
                else if mtype.mclass.kind == extern_kind and mtype.mclass.name != "NativeString" then
                        # Is an extern class (other than Pointer and NativeString)
                        # Pointer is caught in a previous `if`, and NativeString is internal

                        var pointer_type = mainmodule.pointer_type

                        self.provide_declaration("NEW_{c_name}", "{mtype.ctype} NEW_{c_name}(const struct type* type);")
                        v.add_decl("/* allocate extern {mtype} */")
                        v.add_decl("{mtype.ctype} NEW_{c_name}(const struct type* type) \{")
                        if is_dead then
                                v.add_abort("{mclass} is DEAD")
                        else
                                var res = v.new_named_var(mtype, "self")
                                res.is_exact = true
                                v.add("{res} = nit_alloc(sizeof(struct instance_{pointer_type.c_name}));")
                                v.add("{res}->type = type;")
                                hardening_live_type(v, "type")
                                v.require_declaration("class_{c_name}")
                                v.add("{res}->class = &class_{c_name};")
                                v.add("((struct instance_{pointer_type.c_name}*){res})->value = NULL;")
                                v.add("return {res};")
                        end
                        v.add("\}")
                        return
                end

                #Build NEW
                self.provide_declaration("NEW_{c_name}", "{mtype.ctype} NEW_{c_name}(const struct type* type);")
                v.add_decl("/* allocate {mtype} */")
                v.add_decl("{mtype.ctype} NEW_{c_name}(const struct type* type) \{")
                if is_dead then
                        v.add_abort("{mclass} is DEAD")
                else
                        var res = v.new_named_var(mtype, "self")
                        res.is_exact = true
                        var attrs = self.attr_tables.get_or_null(mclass)
                        if attrs == null then
                                v.add("{res} = nit_alloc(sizeof(struct instance));")
                        else
                                v.add("{res} = nit_alloc(sizeof(struct instance) + {attrs.length}*sizeof(nitattribute_t));")
                        end
                        v.add("{res}->type = type;")
                        hardening_live_type(v, "type")
                        v.require_declaration("class_{c_name}")
                        v.add("{res}->class = &class_{c_name};")
                        if attrs != null then
                                self.generate_init_attr(v, res, mtype)
                                v.set_finalizer res
                        end
                        v.add("return {res};")
                end
                v.add("\}")
        end

        # Compile structures used to map tagged primitive values to their classes and types.
        # This method also determines which class will be tagged.
        fun compile_class_infos
        do
                if modelbuilder.toolcontext.opt_no_tag_primitives.value then return

                # Note: if you change the tagging scheme, do not forget to update
                # `autobox` and `extract_tag`
                var class_info = new Array[nullable MClass].filled_with(null, 4)
                for t in box_kinds.keys do
                        # Note: a same class can be associated to multiple slots if one want to
                        # use some Huffman coding.
                        if t.name == "Int" then
                                class_info[1] = t
                        else if t.name == "Char" then
                                class_info[2] = t
                        else if t.name == "Bool" then
                                class_info[3] = t
                        else
                                continue
                        end
                        t.mclass_type.is_tagged = true
                end

                # Compile the table for classes. The tag is used as an index
                var v = self.new_visitor
                v.add_decl "const struct class *class_info[4] = \{"
                for t in class_info do
                        if t == null then
                                v.add_decl("NULL,")
                        else
                                var s = "class_{t.c_name}"
                                v.require_declaration(s)
                                v.add_decl("&{s},")
                        end
                end
                v.add_decl("\};")

                # Compile the table for types. The tag is used as an index
                v.add_decl "const struct type *type_info[4] = \{"
                for t in class_info do
                        if t == null then
                                v.add_decl("NULL,")
                        else
                                var s = "type_{t.c_name}"
                                undead_types.add(t.mclass_type)
                                v.require_declaration(s)
                                v.add_decl("&{s},")
                        end
                end
                v.add_decl("\};")
        end

        # Add a dynamic test to ensure that the type referenced by `t` is a live type
        fun hardening_live_type(v: VISITOR, t: String)
        do
                if not v.compiler.modelbuilder.toolcontext.opt_hardening.value then return
                v.add("if({t} == NULL) \{")
                v.add_abort("type null")
                v.add("\}")
                v.add("if({t}->table_size < 0) \{")
                v.add("PRINT_ERROR(\"Insantiation of a dead type: %s\\n\", {t}->name);")
                v.add_abort("type dead")
                v.add("\}")
        end

        redef fun new_visitor do return new SeparateCompilerVisitor(self)

        # Stats

        private var type_tables: Map[MType, Array[nullable MType]] = new HashMap[MType, Array[nullable MType]]
        private var resolution_tables: Map[MClassType, Array[nullable MType]] = new HashMap[MClassType, Array[nullable MType]]
        protected var method_tables: Map[MClass, Array[nullable MPropDef]] = new HashMap[MClass, Array[nullable MPropDef]]
        protected var attr_tables: Map[MClass, Array[nullable MProperty]] = new HashMap[MClass, Array[nullable MProperty]]

        redef fun display_stats
        do
                super
                if self.modelbuilder.toolcontext.opt_tables_metrics.value then
                        display_sizes
                end
                if self.modelbuilder.toolcontext.opt_isset_checks_metrics.value then
                        display_isset_checks
                end
                var tc = self.modelbuilder.toolcontext
                tc.info("# implementation of method invocation",2)
                var nb_invok_total = modelbuilder.nb_invok_by_tables + modelbuilder.nb_invok_by_direct + modelbuilder.nb_invok_by_inline
                tc.info("total number of invocations: {nb_invok_total}",2)
                tc.info("invocations by VFT send:     {modelbuilder.nb_invok_by_tables} ({div(modelbuilder.nb_invok_by_tables,nb_invok_total)}%)",2)
                tc.info("invocations by direct call:  {modelbuilder.nb_invok_by_direct} ({div(modelbuilder.nb_invok_by_direct,nb_invok_total)}%)",2)
                tc.info("invocations by inlining:     {modelbuilder.nb_invok_by_inline} ({div(modelbuilder.nb_invok_by_inline,nb_invok_total)}%)",2)
        end

        fun display_sizes
        do
                print "# size of subtyping tables"
                print "\ttotal \tholes"
                var total = 0
                var holes = 0
                for t, table in type_tables do
                        total += table.length
                        for e in table do if e == null then holes += 1
                end
                print "\t{total}\t{holes}"

                print "# size of resolution tables"
                print "\ttotal \tholes"
                total = 0
                holes = 0
                for t, table in resolution_tables do
                        total += table.length
                        for e in table do if e == null then holes += 1
                end
                print "\t{total}\t{holes}"

                print "# size of methods tables"
                print "\ttotal \tholes"
                total = 0
                holes = 0
                for t, table in method_tables do
                        total += table.length
                        for e in table do if e == null then holes += 1
                end
                print "\t{total}\t{holes}"

                print "# size of attributes tables"
                print "\ttotal \tholes"
                total = 0
                holes = 0
                for t, table in attr_tables do
                        total += table.length
                        for e in table do if e == null then holes += 1
                end
                print "\t{total}\t{holes}"
        end

        protected var isset_checks_count = 0
        protected var attr_read_count = 0

        fun display_isset_checks do
                print "# total number of compiled attribute reads"
                print "\t{attr_read_count}"
                print "# total number of compiled isset-checks"
                print "\t{isset_checks_count}"
        end

        redef fun compile_nitni_structs
        do
                self.header.add_decl """
struct nitni_instance \{
        struct nitni_instance *next,
                *prev; /* adjacent global references in global list */
        int count; /* number of time this global reference has been marked */
        struct instance *value;
\};
"""
                super
        end

        redef fun finalize_ffi_for_module(mmodule)
        do
                var old_module = self.mainmodule
                self.mainmodule = mmodule
                super
                self.mainmodule = old_module
        end
end

# A visitor on the AST of property definition that generate the C code of a separate compilation process.
class SeparateCompilerVisitor
        super AbstractCompilerVisitor

        redef type COMPILER: SeparateCompiler

        redef fun adapt_signature(m, args)
        do
                var msignature = m.msignature.resolve_for(m.mclassdef.bound_mtype, m.mclassdef.bound_mtype, m.mclassdef.mmodule, true)
                var recv = args.first
                if recv.mtype.ctype != m.mclassdef.mclass.mclass_type.ctype then
                        args.first = self.autobox(args.first, m.mclassdef.mclass.mclass_type)
                end
                for i in [0..msignature.arity[ do
                        var t = msignature.mparameters[i].mtype
                        if i == msignature.vararg_rank then
                                t = args[i+1].mtype
                        end
                        args[i+1] = self.autobox(args[i+1], t)
                end
        end

        redef fun unbox_signature_extern(m, args)
        do
                var msignature = m.msignature.resolve_for(m.mclassdef.bound_mtype, m.mclassdef.bound_mtype, m.mclassdef.mmodule, true)
                if not m.mproperty.is_init and m.is_extern then
                        args.first = self.unbox_extern(args.first, m.mclassdef.mclass.mclass_type)
                end
                for i in [0..msignature.arity[ do
                        var t = msignature.mparameters[i].mtype
                        if i == msignature.vararg_rank then
                                t = args[i+1].mtype
                        end
                        if m.is_extern then args[i+1] = self.unbox_extern(args[i+1], t)
                end
        end

        redef fun autobox(value, mtype)
        do
                if value.mtype == mtype then
                        return value
                else if not value.mtype.is_c_primitive and not mtype.is_c_primitive then
                        return value
                else if not value.mtype.is_c_primitive then
                        if mtype.is_tagged then
                                if mtype.name == "Int" then
                                        return self.new_expr("(long)({value})>>2", mtype)
                                else if mtype.name == "Char" then
                                        return self.new_expr("(uint32_t)((long)({value})>>2)", mtype)
                                else if mtype.name == "Bool" then
                                        return self.new_expr("(short int)((long)({value})>>2)", mtype)
                                else
                                        abort
                                end
                        end
                        return self.new_expr("((struct instance_{mtype.c_name}*){value})->value; /* autounbox from {value.mtype} to {mtype} */", mtype)
                else if not mtype.is_c_primitive then
                        assert value.mtype == value.mcasttype
                        if value.mtype.is_tagged then
                                var res
                                if value.mtype.name == "Int" then
                                        res = self.new_expr("(val*)({value}<<2|1)", mtype)
                                else if value.mtype.name == "Char" then
                                        res = self.new_expr("(val*)((long)({value})<<2|2)", mtype)
                                else if value.mtype.name == "Bool" then
                                        res = self.new_expr("(val*)((long)({value})<<2|3)", mtype)
                                else
                                        abort
                                end
                                # Do not loose type info
                                res.mcasttype = value.mcasttype
                                return res
                        end
                        var valtype = value.mtype.as(MClassType)
                        if mtype isa MClassType and mtype.mclass.kind == extern_kind and mtype.mclass.name != "NativeString" then
                                valtype = compiler.mainmodule.pointer_type
                        end
                        var res = self.new_var(mtype)
                        # Do not loose type info
                        res.mcasttype = value.mcasttype
                        self.require_declaration("BOX_{valtype.c_name}")
                        self.add("{res} = BOX_{valtype.c_name}({value}); /* autobox from {value.mtype} to {mtype} */")
                        return res
                else if (value.mtype.ctype == "void*" and mtype.ctype == "void*") or
                        (value.mtype.ctype == "char*" and mtype.ctype == "void*") or
                        (value.mtype.ctype == "void*" and mtype.ctype == "char*") then
                        return value
                else
                        # Bad things will appen!
                        var res = self.new_var(mtype)
                        self.add("/* {res} left unintialized (cannot convert {value.mtype} to {mtype}) */")
                        self.add("PRINT_ERROR(\"Cast error: Cannot cast %s to %s.\\n\", \"{value.mtype}\", \"{mtype}\"); fatal_exit(1);")
                        return res
                end
        end

        redef fun unbox_extern(value, mtype)
        do
                if mtype isa MClassType and mtype.mclass.kind == extern_kind and
                   mtype.mclass.name != "NativeString" then
                        var pointer_type = compiler.mainmodule.pointer_type
                        var res = self.new_var_extern(mtype)
                        self.add "{res} = ((struct instance_{pointer_type.c_name}*){value})->value; /* unboxing {value.mtype} */"
                        return res
                else
                        return value
                end
        end

        redef fun box_extern(value, mtype)
        do
                if mtype isa MClassType and mtype.mclass.kind == extern_kind and
                   mtype.mclass.name != "NativeString" then
                        var valtype = compiler.mainmodule.pointer_type
                        var res = self.new_var(mtype)
                        compiler.undead_types.add(mtype)
                        self.require_declaration("BOX_{valtype.c_name}")
                        self.add("{res} = BOX_{valtype.c_name}({value}); /* boxing {value.mtype} */")
                        self.require_declaration("type_{mtype.c_name}")
                        self.add("{res}->type = &type_{mtype.c_name};")
                        self.require_declaration("class_{mtype.c_name}")
                        self.add("{res}->class = &class_{mtype.c_name};")
                        return res
                else
                        return value
                end
        end

        # Returns a C expression containing the tag of the value as a long.
        #
        # If the C expression is evaluated to 0, it means there is no tag.
        # Thus the expression can be used as a condition.
        fun extract_tag(value: RuntimeVariable): String
        do
                assert not value.mtype.is_c_primitive
                return "((long){value}&3)" # Get the two low bits
        end

        # Returns a C expression of the runtime class structure of the value.
        # The point of the method is to work also with primitive types.
        fun class_info(value: RuntimeVariable): String
        do
                if not value.mtype.is_c_primitive then
                        if can_be_primitive(value) and not compiler.modelbuilder.toolcontext.opt_no_tag_primitives.value then
                                var tag = extract_tag(value)
                                return "({tag}?class_info[{tag}]:{value}->class)"
                        end
                        return "{value}->class"
                else
                        compiler.undead_types.add(value.mtype)
                        self.require_declaration("class_{value.mtype.c_name}")
                        return "(&class_{value.mtype.c_name})"
                end
        end

        # Returns a C expression of the runtime type structure of the value.
        # The point of the method is to work also with primitive types.
        fun type_info(value: RuntimeVariable): String
        do
                if not value.mtype.is_c_primitive then
                        if can_be_primitive(value) and not compiler.modelbuilder.toolcontext.opt_no_tag_primitives.value then
                                var tag = extract_tag(value)
                                return "({tag}?type_info[{tag}]:{value}->type)"
                        end
                        return "{value}->type"
                else
                        compiler.undead_types.add(value.mtype)
                        self.require_declaration("type_{value.mtype.c_name}")
                        return "(&type_{value.mtype.c_name})"
                end
        end

        redef fun compile_callsite(callsite, args)
        do
                var rta = compiler.runtime_type_analysis
                # TODO: Inlining of new-style constructors with initializers
                if compiler.modelbuilder.toolcontext.opt_direct_call_monomorph.value and rta != null and callsite.mpropdef.initializers.is_empty then
                        var tgs = rta.live_targets(callsite)
                        if tgs.length == 1 then
                                return direct_call(tgs.first, args)
                        end
                end
                # Shortcut intern methods as they are not usually redefinable
                if callsite.mpropdef.is_intern and callsite.mproperty.name != "object_id" then
                        # `object_id` is the only redefined intern method, so it can not be directly called.
                        # TODO find a less ugly approach?
                        return direct_call(callsite.mpropdef, args)
                end
                return super
        end

        # Fully and directly call a mpropdef
        #
        # This method is used by `compile_callsite`
        private fun direct_call(mpropdef: MMethodDef, args: Array[RuntimeVariable]): nullable RuntimeVariable
        do
                var res0 = before_send(mpropdef.mproperty, args)
                var res = call(mpropdef, mpropdef.mclassdef.bound_mtype, args)
                if res0 != null then
                        assert res != null
                        self.assign(res0, res)
                        res = res0
                end
                add("\}") # close the before_send
                return res
        end
        redef fun send(mmethod, arguments)
        do
                if arguments.first.mcasttype.is_c_primitive then
                        # In order to shortcut the primitive, we need to find the most specific method
                        # Howverr, because of performance (no flattening), we always work on the realmainmodule
                        var m = self.compiler.mainmodule
                        self.compiler.mainmodule = self.compiler.realmainmodule
                        var res = self.monomorphic_send(mmethod, arguments.first.mcasttype, arguments)
                        self.compiler.mainmodule = m
                        return res
                end

                return table_send(mmethod, arguments, mmethod)
        end

        # Handle common special cases before doing the effective method invocation
        # This methods handle the `==` and `!=` methods and the case of the null receiver.
        # Note: a { is open in the generated C, that enclose and protect the effective method invocation.
        # Client must not forget to close the } after them.
        #
        # The value returned is the result of the common special cases.
        # If not null, client must compile it with the result of their own effective method invocation.
        #
        # If `before_send` can shortcut the whole message sending, a dummy `if(0){`
        # is generated to cancel the effective method invocation that will follow
        # TODO: find a better approach
        private fun before_send(mmethod: MMethod, arguments: Array[RuntimeVariable]): nullable RuntimeVariable
        do
                var res: nullable RuntimeVariable = null
                var recv = arguments.first
                var consider_null = not self.compiler.modelbuilder.toolcontext.opt_no_check_null.value or mmethod.name == "==" or mmethod.name == "!="
                var maybenull = (recv.mcasttype isa MNullableType or recv.mcasttype isa MNullType) and consider_null
                if maybenull then
                        self.add("if ({recv} == NULL) \{")
                        if mmethod.name == "==" or mmethod.name == "is_same_instance" then
                                res = self.new_var(bool_type)
                                var arg = arguments[1]
                                if arg.mcasttype isa MNullableType then
                                        self.add("{res} = ({arg} == NULL);")
                                else if arg.mcasttype isa MNullType then
                                        self.add("{res} = 1; /* is null */")
                                else
                                        self.add("{res} = 0; /* {arg.inspect} cannot be null */")
                                end
                        else if mmethod.name == "!=" then
                                res = self.new_var(bool_type)
                                var arg = arguments[1]
                                if arg.mcasttype isa MNullableType then
                                        self.add("{res} = ({arg} != NULL);")
                                else if arg.mcasttype isa MNullType then
                                        self.add("{res} = 0; /* is null */")
                                else
                                        self.add("{res} = 1; /* {arg.inspect} cannot be null */")
                                end
                        else
                                self.add_abort("Receiver is null")
                        end
                        self.add("\} else \{")
                else
                        self.add("\{")
                end
                if not self.compiler.modelbuilder.toolcontext.opt_no_shortcut_equate.value and (mmethod.name == "==" or mmethod.name == "!=" or mmethod.name == "is_same_instance") then
                        # Recv is not null, thus if arg is, it is easy to conclude (and respect the invariants)
                        var arg = arguments[1]
                        if arg.mcasttype isa MNullType then
                                if res == null then res = self.new_var(bool_type)
                                if mmethod.name == "!=" then
                                        self.add("{res} = 1; /* arg is null and recv is not */")
                                else # `==` and `is_same_instance`
                                        self.add("{res} = 0; /* arg is null but recv is not */")
                                end
                                self.add("\}") # closes the null case
                                self.add("if (0) \{") # what follow is useless, CC will drop it
                        end
                end
                return res
        end

        private fun table_send(mmethod: MMethod, arguments: Array[RuntimeVariable], mentity: MEntity): nullable RuntimeVariable
        do
                compiler.modelbuilder.nb_invok_by_tables += 1
                if compiler.modelbuilder.toolcontext.opt_invocation_metrics.value then add("count_invoke_by_tables++;")

                assert arguments.length == mmethod.intro.msignature.arity + 1 else debug("Invalid arity for {mmethod}. {arguments.length} arguments given.")

                var res0 = before_send(mmethod, arguments)

                var runtime_function = mmethod.intro.virtual_runtime_function
                var msignature = runtime_function.called_signature

                adapt_signature(mmethod.intro, arguments)

                var res: nullable RuntimeVariable
                var ret = msignature.return_mtype
                if ret == null then
                        res = null
                else
                        res = self.new_var(ret)
                end

                var ss = arguments.join(", ")

                var const_color = mentity.const_color
                var ress
                if res != null then
                        ress = "{res} = "
                else
                        ress = ""
                end
                if mentity isa MMethod and compiler.modelbuilder.toolcontext.opt_direct_call_monomorph0.value then
                        # opt_direct_call_monomorph0 is used to compare the efficiency of the alternative lookup implementation, ceteris paribus.
                        # The difference with the non-zero option is that the monomorphism is looked-at on the mmethod level and not at the callsite level.
                        # TODO: remove this mess and use per callsite service to detect monomorphism in a single place.
                        var md = compiler.is_monomorphic(mentity)
                        if md != null then
                                var callsym = md.virtual_runtime_function.c_name
                                self.require_declaration(callsym)
                                self.add "{ress}{callsym}({ss}); /* {mmethod} on {arguments.first.inspect}*/"
                        else
                                self.require_declaration(const_color)
                                self.add "{ress}(({runtime_function.c_funptrtype})({class_info(arguments.first)}->vft[{const_color}]))({ss}); /* {mmethod} on {arguments.first.inspect}*/"
                        end
                else if mentity isa MMethod and compiler.modelbuilder.toolcontext.opt_guard_call.value then
                        var callsym = "CALL_" + const_color
                        self.require_declaration(callsym)
                        self.add "if (!{callsym}) \{"
                        self.require_declaration(const_color)
                        self.add "{ress}(({runtime_function.c_funptrtype})({class_info(arguments.first)}->vft[{const_color}]))({ss}); /* {mmethod} on {arguments.first.inspect}*/"
                        self.add "\} else \{"
                        self.add "{ress}{callsym}({ss}); /* {mmethod} on {arguments.first.inspect}*/"
                        self.add "\}"
                else if mentity isa MMethod and compiler.modelbuilder.toolcontext.opt_trampoline_call.value then
                        var callsym = "CALL_" + const_color
                        self.require_declaration(callsym)
                        self.add "{ress}{callsym}({ss}); /* {mmethod} on {arguments.first.inspect}*/"
                else
                        self.require_declaration(const_color)
                        self.add "{ress}(({runtime_function.c_funptrtype})({class_info(arguments.first)}->vft[{const_color}]))({ss}); /* {mmethod} on {arguments.first.inspect}*/"
                end

                if res0 != null then
                        assert res != null
                        assign(res0,res)
                        res = res0
                end

                self.add("\}") # closes the null case

                return res
        end

        redef fun call(mmethoddef, recvtype, arguments)
        do
                assert arguments.length == mmethoddef.msignature.arity + 1 else debug("Invalid arity for {mmethoddef}. {arguments.length} arguments given.")

                var res: nullable RuntimeVariable
                var ret = mmethoddef.msignature.return_mtype
                if ret == null then
                        res = null
                else
                        ret = ret.resolve_for(mmethoddef.mclassdef.bound_mtype, mmethoddef.mclassdef.bound_mtype, mmethoddef.mclassdef.mmodule, true)
                        res = self.new_var(ret)
                end

                if (mmethoddef.is_intern and not compiler.modelbuilder.toolcontext.opt_no_inline_intern.value) or
                        (compiler.modelbuilder.toolcontext.opt_inline_some_methods.value and mmethoddef.can_inline(self)) then
                        compiler.modelbuilder.nb_invok_by_inline += 1
                        if compiler.modelbuilder.toolcontext.opt_invocation_metrics.value then add("count_invoke_by_inline++;")
                        var frame = new StaticFrame(self, mmethoddef, recvtype, arguments)
                        frame.returnlabel = self.get_name("RET_LABEL")
                        frame.returnvar = res
                        var old_frame = self.frame
                        self.frame = frame
                        self.add("\{ /* Inline {mmethoddef} ({arguments.join(",")}) on {arguments.first.inspect} */")
                        mmethoddef.compile_inside_to_c(self, arguments)
                        self.add("{frame.returnlabel.as(not null)}:(void)0;")
                        self.add("\}")
                        self.frame = old_frame
                        return res
                end
                compiler.modelbuilder.nb_invok_by_direct += 1
                if compiler.modelbuilder.toolcontext.opt_invocation_metrics.value then add("count_invoke_by_direct++;")

                # Autobox arguments
                self.adapt_signature(mmethoddef, arguments)

                self.require_declaration(mmethoddef.c_name)
                if res == null then
                        self.add("{mmethoddef.c_name}({arguments.join(", ")}); /* Direct call {mmethoddef} on {arguments.first.inspect}*/")
                        return null
                else
                        self.add("{res} = {mmethoddef.c_name}({arguments.join(", ")});")
                end

                return res
        end

        redef fun supercall(m: MMethodDef, recvtype: MClassType, arguments: Array[RuntimeVariable]): nullable RuntimeVariable
        do
                if arguments.first.mcasttype.is_c_primitive then
                        # In order to shortcut the primitive, we need to find the most specific method
                        # However, because of performance (no flattening), we always work on the realmainmodule
                        var main = self.compiler.mainmodule
                        self.compiler.mainmodule = self.compiler.realmainmodule
                        var res = self.monomorphic_super_send(m, recvtype, arguments)
                        self.compiler.mainmodule = main
                        return res
                end
                return table_send(m.mproperty, arguments, m)
        end

        redef fun vararg_instance(mpropdef, recv, varargs, elttype)
        do
                # A vararg must be stored into an new array
                # The trick is that the dymaic type of the array may depends on the receiver
                # of the method (ie recv) if the static type is unresolved
                # This is more complex than usual because the unresolved type must not be resolved
                # with the current receiver (ie self).
                # Therefore to isolate the resolution from self, a local StaticFrame is created.
                # One can see this implementation as an inlined method of the receiver whose only
                # job is to allocate the array
                var old_frame = self.frame
                var frame = new StaticFrame(self, mpropdef, mpropdef.mclassdef.bound_mtype, [recv])
                self.frame = frame
                #print "required Array[{elttype}] for recv {recv.inspect}. bound=Array[{self.resolve_for(elttype, recv)}]. selfvar={frame.arguments.first.inspect}"
                var res = self.array_instance(varargs, elttype)
                self.frame = old_frame
                return res
        end

        redef fun isset_attribute(a, recv)
        do
                self.check_recv_notnull(recv)
                var res = self.new_var(bool_type)

                # What is the declared type of the attribute?
                var mtype = a.intro.static_mtype.as(not null)
                var intromclassdef = a.intro.mclassdef
                mtype = mtype.resolve_for(intromclassdef.bound_mtype, intromclassdef.bound_mtype, intromclassdef.mmodule, true)

                if mtype isa MNullableType then
                        self.add("{res} = 1; /* easy isset: {a} on {recv.inspect} */")
                        return res
                end

                self.require_declaration(a.const_color)
                if self.compiler.modelbuilder.toolcontext.opt_no_union_attribute.value then
                        self.add("{res} = {recv}->attrs[{a.const_color}] != NULL; /* {a} on {recv.inspect}*/")
                else

                        if not mtype.is_c_primitive and not mtype.is_tagged then
                                self.add("{res} = {recv}->attrs[{a.const_color}].val != NULL; /* {a} on {recv.inspect} */")
                        else
                                self.add("{res} = 1; /* NOT YET IMPLEMENTED: isset of primitives: {a} on {recv.inspect} */")
                        end
                end
                return res
        end

        redef fun read_attribute(a, recv)
        do
                self.check_recv_notnull(recv)

                # What is the declared type of the attribute?
                var ret = a.intro.static_mtype.as(not null)
                var intromclassdef = a.intro.mclassdef
                ret = ret.resolve_for(intromclassdef.bound_mtype, intromclassdef.bound_mtype, intromclassdef.mmodule, true)

                if self.compiler.modelbuilder.toolcontext.opt_isset_checks_metrics.value then
                        self.compiler.attr_read_count += 1
                        self.add("count_attr_reads++;")
                end

                self.require_declaration(a.const_color)
                if self.compiler.modelbuilder.toolcontext.opt_no_union_attribute.value then
                        # Get the attribute or a box (ie. always a val*)
                        var cret = self.object_type.as_nullable
                        var res = self.new_var(cret)
                        res.mcasttype = ret

                        self.add("{res} = {recv}->attrs[{a.const_color}]; /* {a} on {recv.inspect} */")

                        # Check for Uninitialized attribute
                        if not ret isa MNullableType and not self.compiler.modelbuilder.toolcontext.opt_no_check_attr_isset.value then
                                self.add("if (unlikely({res} == NULL)) \{")
                                self.add_abort("Uninitialized attribute {a.name}")
                                self.add("\}")

                                if self.compiler.modelbuilder.toolcontext.opt_isset_checks_metrics.value then
                                        self.compiler.isset_checks_count += 1
                                        self.add("count_isset_checks++;")
                                end
                        end

                        # Return the attribute or its unboxed version
                        # Note: it is mandatory since we reuse the box on write, we do not whant that the box escapes
                        return self.autobox(res, ret)
                else
                        var res = self.new_var(ret)
                        self.add("{res} = {recv}->attrs[{a.const_color}].{ret.ctypename}; /* {a} on {recv.inspect} */")

                        # Check for Uninitialized attribute
                        if not ret.is_c_primitive and not ret isa MNullableType and not self.compiler.modelbuilder.toolcontext.opt_no_check_attr_isset.value then
                                self.add("if (unlikely({res} == NULL)) \{")
                                self.add_abort("Uninitialized attribute {a.name}")
                                self.add("\}")
                                if self.compiler.modelbuilder.toolcontext.opt_isset_checks_metrics.value then
                                        self.compiler.isset_checks_count += 1
                                        self.add("count_isset_checks++;")
                                end
                        end

                        return res
                end
        end

        redef fun write_attribute(a, recv, value)
        do
                self.check_recv_notnull(recv)

                # What is the declared type of the attribute?
                var mtype = a.intro.static_mtype.as(not null)
                var intromclassdef = a.intro.mclassdef
                mtype = mtype.resolve_for(intromclassdef.bound_mtype, intromclassdef.bound_mtype, intromclassdef.mmodule, true)

                # Adapt the value to the declared type
                value = self.autobox(value, mtype)

                self.require_declaration(a.const_color)
                if self.compiler.modelbuilder.toolcontext.opt_no_union_attribute.value then
                        var attr = "{recv}->attrs[{a.const_color}]"
                        if mtype.is_tagged then
                                # The attribute is not primitive, thus store it as tagged
                                var tv = autobox(value, compiler.mainmodule.object_type)
                                self.add("{attr} = {tv}; /* {a} on {recv.inspect} */")
                        else if mtype.is_c_primitive then
                                assert mtype isa MClassType
                                # The attribute is primitive, thus we store it in a box
                                # The trick is to create the box the first time then resuse the box
                                self.add("if ({attr} != NULL) \{")
                                self.add("((struct instance_{mtype.c_name}*){attr})->value = {value}; /* {a} on {recv.inspect} */")
                                self.add("\} else \{")
                                value = self.autobox(value, self.object_type.as_nullable)
                                self.add("{attr} = {value}; /* {a} on {recv.inspect} */")
                                self.add("\}")
                        else
                                # The attribute is not primitive, thus store it direclty
                                self.add("{attr} = {value}; /* {a} on {recv.inspect} */")
                        end
                else
                        self.add("{recv}->attrs[{a.const_color}].{mtype.ctypename} = {value}; /* {a} on {recv.inspect} */")
                end
        end

        # Check that mtype is a live open type
        fun hardening_live_open_type(mtype: MType)
        do
                if not compiler.modelbuilder.toolcontext.opt_hardening.value then return
                self.require_declaration(mtype.const_color)
                var col = mtype.const_color
                self.add("if({col} == -1) \{")
                self.add("PRINT_ERROR(\"Resolution of a dead open type: %s\\n\", \"{mtype.to_s.escape_to_c}\");")
                self.add_abort("open type dead")
                self.add("\}")
        end

        # Check that mtype it a pointer to a live cast type
        fun hardening_cast_type(t: String)
        do
                if not compiler.modelbuilder.toolcontext.opt_hardening.value then return
                add("if({t} == NULL) \{")
                add_abort("cast type null")
                add("\}")
                add("if({t}->id == -1 || {t}->color == -1) \{")
                add("PRINT_ERROR(\"Try to cast on a dead cast type: %s\\n\", {t}->name);")
                add_abort("cast type dead")
                add("\}")
        end

        redef fun init_instance(mtype)
        do
                self.require_declaration("NEW_{mtype.mclass.c_name}")
                var compiler = self.compiler
                if mtype isa MGenericType and mtype.need_anchor then
                        hardening_live_open_type(mtype)
                        link_unresolved_type(self.frame.mpropdef.mclassdef, mtype)
                        var recv = self.frame.arguments.first
                        var recv_type_info = self.type_info(recv)
                        self.require_declaration(mtype.const_color)
                        return self.new_expr("NEW_{mtype.mclass.c_name}({recv_type_info}->resolution_table->types[{mtype.const_color}])", mtype)
                end
                compiler.undead_types.add(mtype)
                self.require_declaration("type_{mtype.c_name}")
                return self.new_expr("NEW_{mtype.mclass.c_name}(&type_{mtype.c_name})", mtype)
        end

        redef fun type_test(value, mtype, tag)
        do
                self.add("/* {value.inspect} isa {mtype} */")
                var compiler = self.compiler

                var recv = self.frame.arguments.first
                var recv_type_info = self.type_info(recv)

                var res = self.new_var(bool_type)

                var cltype = self.get_name("cltype")
                self.add_decl("int {cltype};")
                var idtype = self.get_name("idtype")
                self.add_decl("int {idtype};")

                var maybe_null = self.maybe_null(value)
                var accept_null = "0"
                var ntype = mtype
                if ntype isa MNullableType then
                        ntype = ntype.mtype
                        accept_null = "1"
                end

                if value.mcasttype.is_subtype(self.frame.mpropdef.mclassdef.mmodule, self.frame.mpropdef.mclassdef.bound_mtype, mtype) then
                        self.add("{res} = 1; /* easy {value.inspect} isa {mtype}*/")
                        if compiler.modelbuilder.toolcontext.opt_typing_test_metrics.value then
                                self.compiler.count_type_test_skipped[tag] += 1
                                self.add("count_type_test_skipped_{tag}++;")
                        end
                        return res
                end

                if ntype.need_anchor then
                        var type_struct = self.get_name("type_struct")
                        self.add_decl("const struct type* {type_struct};")

                        # Either with resolution_table with a direct resolution
                        hardening_live_open_type(mtype)
                        link_unresolved_type(self.frame.mpropdef.mclassdef, mtype)
                        self.require_declaration(mtype.const_color)
                        self.add("{type_struct} = {recv_type_info}->resolution_table->types[{mtype.const_color}];")
                        if compiler.modelbuilder.toolcontext.opt_typing_test_metrics.value then
                                self.compiler.count_type_test_unresolved[tag] += 1
                                self.add("count_type_test_unresolved_{tag}++;")
                        end
                        hardening_cast_type(type_struct)
                        self.add("{cltype} = {type_struct}->color;")
                        self.add("{idtype} = {type_struct}->id;")
                        if maybe_null and accept_null == "0" then
                                var is_nullable = self.get_name("is_nullable")
                                self.add_decl("short int {is_nullable};")
                                self.add("{is_nullable} = {type_struct}->is_nullable;")
                                accept_null = is_nullable.to_s
                        end
                else if ntype isa MClassType then
                        compiler.undead_types.add(mtype)
                        self.require_declaration("type_{mtype.c_name}")
                        hardening_cast_type("(&type_{mtype.c_name})")
                        self.add("{cltype} = type_{mtype.c_name}.color;")
                        self.add("{idtype} = type_{mtype.c_name}.id;")
                        if compiler.modelbuilder.toolcontext.opt_typing_test_metrics.value then
                                self.compiler.count_type_test_resolved[tag] += 1
                                self.add("count_type_test_resolved_{tag}++;")
                        end
                else
                        self.add("PRINT_ERROR(\"NOT YET IMPLEMENTED: type_test(%s, {mtype}).\\n\", \"{value.inspect}\"); fatal_exit(1);")
                end

                # check color is in table
                if maybe_null then
                        self.add("if({value} == NULL) \{")
                        self.add("{res} = {accept_null};")
                        self.add("\} else \{")
                end
                var value_type_info = self.type_info(value)
                self.add("if({cltype} >= {value_type_info}->table_size) \{")
                self.add("{res} = 0;")
                self.add("\} else \{")
                self.add("{res} = {value_type_info}->type_table[{cltype}] == {idtype};")
                self.add("\}")
                if maybe_null then
                        self.add("\}")
                end

                return res
        end

        redef fun is_same_type_test(value1, value2)
        do
                var res = self.new_var(bool_type)
                # Swap values to be symetric
                if value2.mtype.is_c_primitive and not value1.mtype.is_c_primitive then
                        var tmp = value1
                        value1 = value2
                        value2 = tmp
                end
                if value1.mtype.is_c_primitive then
                        if value2.mtype == value1.mtype then
                                self.add("{res} = 1; /* is_same_type_test: compatible types {value1.mtype} vs. {value2.mtype} */")
                        else if value2.mtype.is_c_primitive then
                                self.add("{res} = 0; /* is_same_type_test: incompatible types {value1.mtype} vs. {value2.mtype}*/")
                        else
                                var mtype1 = value1.mtype.as(MClassType)
                                self.require_declaration("class_{mtype1.c_name}")
                                self.add("{res} = ({value2} != NULL) && ({value2}->class == &class_{mtype1.c_name}); /* is_same_type_test */")
                        end
                else
                        self.add("{res} = ({value1} == {value2}) || ({value1} != NULL && {value2} != NULL && {class_info(value1)} == {class_info(value2)}); /* is_same_type_test */")
                end
                return res
        end

        redef fun class_name_string(value)
        do
                var res = self.get_name("var_class_name")
                self.add_decl("const char* {res};")
                if not value.mtype.is_c_primitive then
                        self.add "{res} = {value} == NULL ? \"null\" : {type_info(value)}->name;"
                else if value.mtype isa MClassType and value.mtype.as(MClassType).mclass.kind == extern_kind and
                        value.mtype.as(MClassType).name != "NativeString" then
                        self.add "{res} = \"{value.mtype.as(MClassType).mclass}\";"
                else
                        self.require_declaration("type_{value.mtype.c_name}")
                        self.add "{res} = type_{value.mtype.c_name}.name;"
                end
                return res
        end

        redef fun equal_test(value1, value2)
        do
                var res = self.new_var(bool_type)
                if value2.mtype.is_c_primitive and not value1.mtype.is_c_primitive then
                        var tmp = value1
                        value1 = value2
                        value2 = tmp
                end
                if value1.mtype.is_c_primitive then
                        if value2.mtype == value1.mtype then
                                self.add("{res} = {value1} == {value2};")
                        else if value2.mtype.is_c_primitive then
                                self.add("{res} = 0; /* incompatible types {value1.mtype} vs. {value2.mtype}*/")
                        else if value1.mtype.is_tagged then
                                self.add("{res} = ({value2} != NULL) && ({self.autobox(value2, value1.mtype)} == {value1});")
                        else
                                var mtype1 = value1.mtype.as(MClassType)
                                self.require_declaration("class_{mtype1.c_name}")
                                self.add("{res} = ({value2} != NULL) && ({value2}->class == &class_{mtype1.c_name});")
                                self.add("if ({res}) \{")
                                self.add("{res} = ({self.autobox(value2, value1.mtype)} == {value1});")
                                self.add("\}")
                        end
                        return res
                end
                var maybe_null = true
                var test = new Array[String]
                var t1 = value1.mcasttype
                if t1 isa MNullableType then
                        test.add("{value1} != NULL")
                        t1 = t1.mtype
                else
                        maybe_null = false
                end
                var t2 = value2.mcasttype
                if t2 isa MNullableType then
                        test.add("{value2} != NULL")
                        t2 = t2.mtype
                else
                        maybe_null = false
                end

                var incompatible = false
                var primitive
                if t1.is_c_primitive then
                        primitive = t1
                        if t1 == t2 then
                                # No need to compare class
                        else if t2.is_c_primitive then
                                incompatible = true
                        else if can_be_primitive(value2) then
                                if t1.is_tagged then
                                        self.add("{res} = {value1} == {value2};")
                                        return res
                                end
                                if not compiler.modelbuilder.toolcontext.opt_no_tag_primitives.value then
                                        test.add("(!{extract_tag(value2)})")
                                end
                                test.add("{value1}->class == {value2}->class")
                        else
                                incompatible = true
                        end
                else if t2.is_c_primitive then
                        primitive = t2
                        if can_be_primitive(value1) then
                                if t2.is_tagged then
                                        self.add("{res} = {value1} == {value2};")
                                        return res
                                end
                                if not compiler.modelbuilder.toolcontext.opt_no_tag_primitives.value then
                                        test.add("(!{extract_tag(value1)})")
                                end
                                test.add("{value1}->class == {value2}->class")
                        else
                                incompatible = true
                        end
                else
                        primitive = null
                end

                if incompatible then
                        if maybe_null then
                                self.add("{res} = {value1} == {value2}; /* incompatible types {t1} vs. {t2}; but may be NULL*/")
                                return res
                        else
                                self.add("{res} = 0; /* incompatible types {t1} vs. {t2}; cannot be NULL */")
                                return res
                        end
                end
                if primitive != null then
                        if primitive.is_tagged then
                                self.add("{res} = {value1} == {value2};")
                                return res
                        end
                        test.add("((struct instance_{primitive.c_name}*){value1})->value == ((struct instance_{primitive.c_name}*){value2})->value")
                else if can_be_primitive(value1) and can_be_primitive(value2) then
                        if not compiler.modelbuilder.toolcontext.opt_no_tag_primitives.value then
                                test.add("(!{extract_tag(value1)}) && (!{extract_tag(value2)})")
                        end
                        test.add("{value1}->class == {value2}->class")
                        var s = new Array[String]
                        for t, v in self.compiler.box_kinds do
                                if t.mclass_type.is_tagged then continue
                                s.add "({value1}->class->box_kind == {v} && ((struct instance_{t.c_name}*){value1})->value == ((struct instance_{t.c_name}*){value2})->value)"
                        end
                        if s.is_empty then
                                self.add("{res} = {value1} == {value2};")
                                return res
                        end
                        test.add("({s.join(" || ")})")
                else
                        self.add("{res} = {value1} == {value2};")
                        return res
                end
                self.add("{res} = {value1} == {value2} || ({test.join(" && ")});")
                return res
        end

        fun can_be_primitive(value: RuntimeVariable): Bool
        do
                var t = value.mcasttype.undecorate
                if not t isa MClassType then return false
                var k = t.mclass.kind
                return k == interface_kind or t.is_c_primitive
        end

        fun maybe_null(value: RuntimeVariable): Bool
        do
                var t = value.mcasttype
                return t isa MNullableType or t isa MNullType
        end

        redef fun array_instance(array, elttype)
        do
                var nclass = mmodule.native_array_class
                var arrayclass = mmodule.array_class
                var arraytype = arrayclass.get_mtype([elttype])
                var res = self.init_instance(arraytype)
                self.add("\{ /* {res} = array_instance Array[{elttype}] */")
                var length = self.int_instance(array.length)
                var nat = native_array_instance(elttype, length)
                for i in [0..array.length[ do
                        var r = self.autobox(array[i], self.object_type)
                        self.add("((struct instance_{nclass.c_name}*){nat})->values[{i}] = (val*) {r};")
                end
                self.send(self.get_property("with_native", arrayclass.intro.bound_mtype), [res, nat, length])
                self.add("\}")
                return res
        end

        redef fun native_array_instance(elttype: MType, length: RuntimeVariable): RuntimeVariable
        do
                var mtype = mmodule.native_array_type(elttype)
                self.require_declaration("NEW_{mtype.mclass.c_name}")
                assert mtype isa MGenericType
                var compiler = self.compiler
                length = autobox(length, compiler.mainmodule.int_type)
                if mtype.need_anchor then
                        hardening_live_open_type(mtype)
                        link_unresolved_type(self.frame.mpropdef.mclassdef, mtype)
                        var recv = self.frame.arguments.first
                        var recv_type_info = self.type_info(recv)
                        self.require_declaration(mtype.const_color)
                        return self.new_expr("NEW_{mtype.mclass.c_name}({length}, {recv_type_info}->resolution_table->types[{mtype.const_color}])", mtype)
                end
                compiler.undead_types.add(mtype)
                self.require_declaration("type_{mtype.c_name}")
                return self.new_expr("NEW_{mtype.mclass.c_name}({length}, &type_{mtype.c_name})", mtype)
        end

        redef fun native_array_def(pname, ret_type, arguments)
        do
                var elttype = arguments.first.mtype
                var nclass = mmodule.native_array_class
                var recv = "((struct instance_{nclass.c_name}*){arguments[0]})->values"
                if pname == "[]" then
                        # Because the objects are boxed, return the box to avoid unnecessary (or broken) unboxing/reboxing
                        var res = self.new_expr("{recv}[{arguments[1]}]", compiler.mainmodule.object_type)
                        res.mcasttype = ret_type.as(not null)
                        self.ret(res)
                        return
                else if pname == "[]=" then
                        self.add("{recv}[{arguments[1]}]={arguments[2]};")
                        return
                else if pname == "length" then
                        self.ret(self.new_expr("((struct instance_{nclass.c_name}*){arguments[0]})->length", ret_type.as(not null)))
                        return
                else if pname == "copy_to" then
                        var recv1 = "((struct instance_{nclass.c_name}*){arguments[1]})->values"
                        self.add("memmove({recv1}, {recv}, {arguments[2]}*sizeof({elttype.ctype}));")
                        return
                end
        end

        redef fun native_array_get(nat, i)
        do
                var nclass = mmodule.native_array_class
                var recv = "((struct instance_{nclass.c_name}*){nat})->values"
                # Because the objects are boxed, return the box to avoid unnecessary (or broken) unboxing/reboxing
                var res = self.new_expr("{recv}[{i}]", compiler.mainmodule.object_type)
                return res
        end

        redef fun native_array_set(nat, i, val)
        do
                var nclass = mmodule.native_array_class
                var recv = "((struct instance_{nclass.c_name}*){nat})->values"
                self.add("{recv}[{i}]={val};")
        end

        fun link_unresolved_type(mclassdef: MClassDef, mtype: MType) do
                assert mtype.need_anchor
                var compiler = self.compiler
                if not compiler.live_unresolved_types.has_key(self.frame.mpropdef.mclassdef) then
                        compiler.live_unresolved_types[self.frame.mpropdef.mclassdef] = new HashSet[MType]
                end
                compiler.live_unresolved_types[self.frame.mpropdef.mclassdef].add(mtype)
        end
end

redef class MMethodDef
        # The C function associated to a mmethoddef
        fun separate_runtime_function: SeparateRuntimeFunction
        do
                var res = self.separate_runtime_function_cache
                if res == null then
                        var recv = mclassdef.bound_mtype
                        var msignature = msignature.resolve_for(recv, recv, mclassdef.mmodule, true)
                        res = new SeparateRuntimeFunction(self, recv, msignature, c_name)
                        self.separate_runtime_function_cache = res
                end
                return res
        end
        private var separate_runtime_function_cache: nullable SeparateRuntimeFunction

        # The C function associated to a mmethoddef, that can be stored into a VFT of a class
        # The first parameter (the reciever) is always typed by val* in order to accept an object value
        # The C-signature is always compatible with the intro
        fun virtual_runtime_function: SeparateRuntimeFunction
        do
                var res = self.virtual_runtime_function_cache
                if res == null then
                        # Because the function is virtual, the signature must match the one of the original class
                        var intromclassdef = mproperty.intro.mclassdef
                        var recv = intromclassdef.bound_mtype

                        res = separate_runtime_function
                        if res.called_recv == recv then
                                self.virtual_runtime_function_cache = res
                                return res
                        end

                        var msignature = mproperty.intro.msignature.resolve_for(recv, recv, intromclassdef.mmodule, true)

                        if recv.ctype == res.called_recv.ctype and msignature.c_equiv(res.called_signature) then
                                self.virtual_runtime_function_cache = res
                                return res
                        end

                        res = new SeparateRuntimeFunction(self, recv, msignature, "VIRTUAL_{c_name}")
                        self.virtual_runtime_function_cache = res
                        res.is_thunk = true
                end
                return res
        end
        private var virtual_runtime_function_cache: nullable SeparateRuntimeFunction
end

redef class MSignature
        # Does the C-version of `self` the same than the C-version of `other`?
        fun c_equiv(other: MSignature): Bool
        do
                if self == other then return true
                if arity != other.arity then return false
                for i in [0..arity[ do
                        if mparameters[i].mtype.ctype != other.mparameters[i].mtype.ctype then return false
                end
                if return_mtype != other.return_mtype then
                        if return_mtype == null or other.return_mtype == null then return false
                        if return_mtype.ctype != other.return_mtype.ctype then return false
                end
                return true
        end
end

# The C function associated to a methoddef separately compiled
class SeparateRuntimeFunction
        super AbstractRuntimeFunction

        # The call-side static receiver
        var called_recv: MType

        # The call-side static signature
        var called_signature: MSignature

        # The name on the compiled method
        redef var build_c_name: String

        # Statically call the original body instead
        var is_thunk = false

        redef fun to_s do return self.mmethoddef.to_s

        # The C return type (something or `void`)
        var c_ret: String is lazy do
                var ret = called_signature.return_mtype
                if ret != null then
                        return ret.ctype
                else
                        return "void"
                end
        end

        # The C signature (only the parmeter part)
        var c_sig: String is lazy do
                var sig = new FlatBuffer
                sig.append("({called_recv.ctype} self")
                for i in [0..called_signature.arity[ do
                        var mtype = called_signature.mparameters[i].mtype
                        if i == called_signature.vararg_rank then
                                mtype = mmethoddef.mclassdef.mmodule.array_type(mtype)
                        end
                        sig.append(", {mtype.ctype} p{i}")
                end
                sig.append(")")
                return sig.to_s
        end

        # The C type for the function pointer.
        var c_funptrtype: String is lazy do return "{c_ret}(*){c_sig}"

        redef fun compile_to_c(compiler)
        do
                var mmethoddef = self.mmethoddef

                var sig = "{c_ret} {c_name}{c_sig}"
                compiler.provide_declaration(self.c_name, "{sig};")

                var rta = compiler.as(SeparateCompiler).runtime_type_analysis

                var recv = self.mmethoddef.mclassdef.bound_mtype
                var v = compiler.new_visitor
                var selfvar = new RuntimeVariable("self", called_recv, recv)
                var arguments = new Array[RuntimeVariable]
                var frame = new StaticFrame(v, mmethoddef, recv, arguments)
                v.frame = frame

                var msignature = called_signature
                var ret = called_signature.return_mtype

                var comment = new FlatBuffer
                comment.append("({selfvar}: {selfvar.mtype}")
                arguments.add(selfvar)
                for i in [0..msignature.arity[ do
                        var mtype = msignature.mparameters[i].mtype
                        if i == msignature.vararg_rank then
                                mtype = v.mmodule.array_type(mtype)
                        end
                        comment.append(", {mtype}")
                        var argvar = new RuntimeVariable("p{i}", mtype, mtype)
                        arguments.add(argvar)
                end
                comment.append(")")
                if ret != null then
                        comment.append(": {ret}")
                end

                v.add_decl("/* method {self} for {comment} */")
                v.add_decl("{sig} \{")
                if ret != null then
                        frame.returnvar = v.new_var(ret)
                end
                frame.returnlabel = v.get_name("RET_LABEL")

                if is_thunk then
                        var subret = v.call(mmethoddef, recv, arguments)
                        if ret != null then
                                assert subret != null
                                v.assign(frame.returnvar.as(not null), subret)
                        end
                else if rta != null and not rta.live_mmodules.has(mmethoddef.mclassdef.mmodule) then
                        v.add_abort("FATAL: Dead method executed.")
                else
                        mmethoddef.compile_inside_to_c(v, arguments)
                end

                v.add("{frame.returnlabel.as(not null)}:;")
                if ret != null then
                        v.add("return {frame.returnvar.as(not null)};")
                end
                v.add("\}")
                compiler.names[self.c_name] = "{mmethoddef.full_name} ({mmethoddef.location.file.filename}:{mmethoddef.location.line_start})"
        end

        # Compile the trampolines used to implement late-binding.
        #
        # See `opt_trampoline_call`.
        fun compile_trampolines(compiler: SeparateCompiler)
        do
                var recv = self.mmethoddef.mclassdef.bound_mtype
                var selfvar = new RuntimeVariable("self", called_recv, recv)
                var ret = called_signature.return_mtype
                var arguments = ["self"]
                for i in [0..called_signature.arity[ do arguments.add "p{i}"

                if mmethoddef.is_intro and not recv.is_c_primitive then
                        var m = mmethoddef.mproperty
                        var n2 = "CALL_" + m.const_color
                        compiler.provide_declaration(n2, "{c_ret} {n2}{c_sig};")
                        var v2 = compiler.new_visitor
                        v2.add "{c_ret} {n2}{c_sig} \{"
                        v2.require_declaration(m.const_color)
                        var call = "(({c_funptrtype})({v2.class_info(selfvar)}->vft[{m.const_color}]))({arguments.join(", ")});"
                        if ret != null then
                                v2.add "return {call}"
                        else
                                v2.add call
                        end

                        v2.add "\}"

                end
                if mmethoddef.has_supercall and not recv.is_c_primitive then
                        var m = mmethoddef
                        var n2 = "CALL_" + m.const_color
                        compiler.provide_declaration(n2, "{c_ret} {n2}{c_sig};")
                        var v2 = compiler.new_visitor
                        v2.add "{c_ret} {n2}{c_sig} \{"
                        v2.require_declaration(m.const_color)
                        var call = "(({c_funptrtype})({v2.class_info(selfvar)}->vft[{m.const_color}]))({arguments.join(", ")});"
                        if ret != null then
                                v2.add "return {call}"
                        else
                                v2.add call
                        end

                        v2.add "\}"
                end
        end
end

redef class MType
        # Are values of `self` tagged?
        # If false, it means that the type is not primitive, or is boxed.
        var is_tagged = false
end

redef class MEntity
        var const_color: String is lazy do return "COLOR_{c_name}"
end

interface PropertyLayoutElement end

redef class MProperty
        super PropertyLayoutElement
end

redef class MPropDef
        super PropertyLayoutElement
end

redef class AMethPropdef
        # The semi-global compilation does not support inlining calls to extern news
        redef fun can_inline
        do
                var m = mpropdef
                if m != null and m.mproperty.is_init and m.is_extern then return false
                return super
        end
end

redef class AAttrPropdef
        redef fun init_expr(v, recv)
        do
                super
                if is_lazy and v.compiler.modelbuilder.toolcontext.opt_no_union_attribute.value then
                        var guard = self.mlazypropdef.mproperty
                        v.write_attribute(guard, recv, v.bool_instance(false))
                end
        end
end