[m-dev.] [reuse] diff: eager codegen structure reuse

[Peter Ross]

Hi,


===================================================================


Estimated hours taken: 8

First cut of structure reuse with the eager code generator.

code_info.m:
unify_gen.m:
    Pass down the how_to_construct type.
    
var_locn.m:
    Generate the code which does structure reuse.


Index: code_info.m
===================================================================
RCS file: /home/mercury1/repository/mercury/compiler/code_info.m,v
retrieving revision 1.252.2.2
diff -u -r1.252.2.2 code_info.m
--- code_info.m	2000/10/09 09:09:50	1.252.2.2
+++ code_info.m	2000/10/09 16:47:27
@@ -3036,7 +3036,8 @@
 	code_info::in, code_info::out) is det.
 
 :- pred code_info__assign_cell_to_var(prog_var::in, tag::in,
-	list(maybe(rval))::in, string::in, code_tree::out,
+	list(maybe(rval))::in, string::in,
+	how_to_construct::in, code_tree::out,
 	code_info::in, code_info::out) is det.
 
 :- pred code_info__place_var(prog_var::in, lval::in, code_tree::out,
@@ -3217,7 +3218,8 @@
 	},
 	code_info__set_var_locns_info(VarInfo).
 
-code_info__assign_cell_to_var(Var, Ptag, Vector, TypeMsg, Code) -->
+code_info__assign_cell_to_var(Var, Ptag, Vector, TypeMsg,
+		HowToConstruct, Code) -->
 	code_info__get_var_locns_info(VarInfo0),
 	code_info__get_next_cell_number(CellNum),
 	{
@@ -3233,7 +3235,7 @@
 	;
 		VarInfo0 = var_locn_info(VarLocInfo0),
 		var_locn__assign_cell_to_var(Var, Ptag, Vector, CellNum,
-			TypeMsg, Code, VarLocInfo0, VarLocInfo),
+			TypeMsg, HowToConstruct, Code, VarLocInfo0, VarLocInfo),
 		VarInfo = var_locn_info(VarLocInfo)
 	},
 	code_info__set_var_locns_info(VarInfo).
Index: unify_gen.m
===================================================================
RCS file: /home/mercury1/repository/mercury/compiler/unify_gen.m,v
retrieving revision 1.108.2.2
diff -u -r1.108.2.2 unify_gen.m
--- unify_gen.m	2000/09/27 15:00:48	1.108.2.2
+++ unify_gen.m	2000/10/09 16:47:59
@@ -62,10 +62,11 @@
 			{ Code = empty }
 		)
 	;
-		{ Uni = construct(Var, ConsId, Args, Modes, _, _, AditiInfo) },
+		{ Uni = construct(Var, ConsId, Args, Modes,
+				HowToConstruct, _, AditiInfo) },
 		( code_info__variable_is_forward_live(Var) ->
 			unify_gen__generate_construction(Var, ConsId,
-				Args, Modes, AditiInfo, Code)
+				Args, Modes, HowToConstruct, AditiInfo, Code)
 		;
 			{ Code = empty }
 		)
@@ -268,28 +269,32 @@
 	% instantiate the arguments of that term.
 
 :- pred unify_gen__generate_construction(prog_var::in, cons_id::in,
-	list(prog_var)::in, list(uni_mode)::in, maybe(rl_exprn_id)::in,
-	code_tree::out, code_info::in, code_info::out) is det.
+	list(prog_var)::in, list(uni_mode)::in, how_to_construct::in,
+	maybe(rl_exprn_id)::in, code_tree::out,
+	code_info::in, code_info::out) is det.
 
-unify_gen__generate_construction(Var, Cons, Args, Modes, AditiInfo, Code) -->
+unify_gen__generate_construction(Var, Cons, Args, Modes,
+		HowToConstruct, AditiInfo, Code) -->
 	code_info__cons_id_to_tag(Var, Cons, Tag),
 	unify_gen__generate_construction_2(Tag, Var, Args,
-		Modes, AditiInfo, Code).
+		Modes, HowToConstruct, AditiInfo, Code).
 
 :- pred unify_gen__generate_construction_2(cons_tag::in, prog_var::in, 
-	list(prog_var)::in, list(uni_mode)::in, maybe(rl_exprn_id)::in,
+	list(prog_var)::in, list(uni_mode)::in,
+	how_to_construct::in, maybe(rl_exprn_id)::in,
 	code_tree::out, code_info::in, code_info::out) is det.
 
 unify_gen__generate_construction_2(string_constant(String),
-		Var, _Args, _Modes, _, empty) -->
+		Var, _Args, _Modes, _HowToConstruct, _, empty) -->
 	code_info__assign_const_to_var(Var, const(string_const(String))).
 unify_gen__generate_construction_2(int_constant(Int),
-		Var, _Args, _Modes, _, empty) -->
+		Var, _Args, _Modes, _HowToConstruct, _, empty) -->
 	code_info__assign_const_to_var(Var, const(int_const(Int))).
 unify_gen__generate_construction_2(float_constant(Float),
-		Var, _Args, _Modes, _, empty) -->
+		Var, _Args, _Modes, _HowToConstruct, _, empty) -->
 	code_info__assign_const_to_var(Var, const(float_const(Float))).
-unify_gen__generate_construction_2(no_tag, Var, Args, Modes, _, Code) -->
+unify_gen__generate_construction_2(no_tag, Var, Args, Modes, _HowToConstruct,
+		_, Code) -->
 	( { Args = [Arg], Modes = [Mode] } ->
 		code_info__variable_type(Arg, Type),
 		unify_gen__generate_sub_unify(ref(Var), ref(Arg),
@@ -298,17 +303,22 @@
 		{ error(
 		"unify_gen__generate_construction_2: no_tag: arity != 1") }
 	).
+
+	% RRR need to modify this code!
 unify_gen__generate_construction_2(unshared_tag(Ptag),
-		Var, Args, Modes, _, Code) -->
+		Var, Args, Modes, HowToConstruct, _, Code) -->
 	code_info__get_module_info(ModuleInfo),
 	unify_gen__var_types(Args, ArgTypes),
 	{ unify_gen__generate_cons_args(Args, ArgTypes, Modes, ModuleInfo,
 		Rvals) },
 	code_info__variable_type(Var, VarType),
 	{ unify_gen__var_type_msg(VarType, VarTypeMsg) },
-	code_info__assign_cell_to_var(Var, Ptag, Rvals, VarTypeMsg, Code).
+	code_info__assign_cell_to_var(Var, Ptag, Rvals, VarTypeMsg,
+			HowToConstruct, Code).
+
+	% RRR need to modify this code!
 unify_gen__generate_construction_2(shared_remote_tag(Ptag, Sectag),
-		Var, Args, Modes, _, Code) -->
+		Var, Args, Modes, HowToConstruct, _, Code) -->
 	code_info__get_module_info(ModuleInfo),
 	unify_gen__var_types(Args, ArgTypes),
 	{ unify_gen__generate_cons_args(Args, ArgTypes, Modes, ModuleInfo,
@@ -317,13 +327,16 @@
 	{ Rvals = [yes(const(int_const(Sectag))) | Rvals0] },
 	code_info__variable_type(Var, VarType),
 	{ unify_gen__var_type_msg(VarType, VarTypeMsg) },
-	code_info__assign_cell_to_var(Var, Ptag, Rvals, VarTypeMsg, Code).
+	code_info__assign_cell_to_var(Var, Ptag, Rvals, VarTypeMsg,
+			HowToConstruct, Code).
+
 unify_gen__generate_construction_2(shared_local_tag(Bits1, Num1),
-		Var, _Args, _Modes, _, empty) -->
+		Var, _Args, _Modes, _HowToConstruct, _, empty) -->
 	code_info__assign_const_to_var(Var,
 		mkword(Bits1, unop(mkbody, const(int_const(Num1))))).
 unify_gen__generate_construction_2(type_ctor_info_constant(ModuleName,
-		TypeName, TypeArity), Var, Args, _Modes, _, empty) -->
+		TypeName, TypeArity), Var, Args, _Modes,
+		_HowToConstruct, _, empty) -->
 	( { Args = [] } ->
 		[]
 	;
@@ -333,7 +346,8 @@
 	{ DataAddr = rtti_addr(RttiTypeId, type_ctor_info) },
 	code_info__assign_const_to_var(Var, const(data_addr_const(DataAddr))).
 unify_gen__generate_construction_2(base_typeclass_info_constant(ModuleName,
-		ClassId, Instance), Var, Args, _Modes, _, empty) -->
+		ClassId, Instance), Var, Args, _HowToConstruct,
+		_Modes, _, empty) -->
 	( { Args = [] } ->
 		[]
 	;
@@ -342,7 +356,7 @@
 	code_info__assign_const_to_var(Var, const(data_addr_const(data_addr(
 		ModuleName, base_typeclass_info(ClassId, Instance))))).
 unify_gen__generate_construction_2(tabling_pointer_constant(PredId, ProcId),
-		Var, Args, _Modes, _, empty) -->
+		Var, Args, _Modes, _HowToConstruct, _, empty) -->
 	( { Args = [] } ->
 		[]
 	;
@@ -354,7 +368,7 @@
 	{ DataAddr = data_addr(ModuleName, tabling_pointer(ProcLabel)) },
 	code_info__assign_const_to_var(Var, const(data_addr_const(DataAddr))).
 unify_gen__generate_construction_2(code_addr_constant(PredId, ProcId),
-		Var, Args, _Modes, _, empty) -->
+		Var, Args, _Modes, _HowToConstruct, _, empty) -->
 	( { Args = [] } ->
 		[]
 	;
@@ -365,7 +379,7 @@
 	code_info__assign_const_to_var(Var, const(code_addr_const(CodeAddr))).
 unify_gen__generate_construction_2(
 		pred_closure_tag(PredId, ProcId, EvalMethod),
-		Var, Args, _Modes, _AditiInfo, Code) -->
+		Var, Args, _Modes, HowToConstruct, _AditiInfo, Code) -->
 	% This code constructs or extends a closure.
 	% The structure of closures is defined in runtime/mercury_ho_call.h.
 
@@ -551,7 +565,8 @@
 			yes(const(int_const(NumArgs)))
 			| PredArgs
 		] },
-		code_info__assign_cell_to_var(Var, 0, Vector, "closure", Code)
+		code_info__assign_cell_to_var(Var, 0, Vector, "closure",
+				HowToConstruct, Code)
 	).
 
 :- pred unify_gen__generate_extra_closure_args(list(prog_var)::in, lval::in,
Index: var_locn.m
===================================================================
RCS file: /home/mercury1/repository/mercury/compiler/var_locn.m,v
retrieving revision 1.1.2.1
diff -u -r1.1.2.1 var_locn.m
--- var_locn.m	2000/09/25 17:06:00	1.1.2.1
+++ var_locn.m	2000/10/09 16:48:01
@@ -149,7 +149,8 @@
 %		and updates the state of VarLocnInfo0 accordingly.
 
 :- pred var_locn__assign_cell_to_var(prog_var::in, tag::in,
-	list(maybe(rval))::in, int::in, string::in, code_tree::out,
+	list(maybe(rval))::in, int::in, string::in,
+	how_to_construct::in, code_tree::out,
 	var_locn_info::in, var_locn_info::out) is det.
 
 %	var_locn__place_var(Var, Lval, Code, VarLocnInfo0, VarLocnInfo)
@@ -773,7 +774,8 @@
 
 %----------------------------------------------------------------------------%
 
-var_locn__assign_cell_to_var(Var, Ptag, Vector, CellNum, TypeMsg, Code) -->
+var_locn__assign_cell_to_var(Var, Ptag, Vector, CellNum, TypeMsg,
+		HowToConstruct, Code) -->
 	{ Reuse = no },
 	{ CellRval0 = create(Ptag, Vector, uniform(no), can_be_either,
 		CellNum, TypeMsg, Reuse) },
@@ -786,8 +788,19 @@
 		var_locn__assign_const_to_var(Var, CellRval),
 		{ Code = empty }
 	;
-		var_locn__assign_dynamic_cell_to_var(Var, Ptag, Vector,
-			TypeMsg, Code)
+		(
+			{ HowToConstruct = construct_statically(_) },
+			{ error("var_locn__assign_cell_to_var") }
+		;
+			{ HowToConstruct = construct_dynamically },
+			var_locn__assign_dynamic_cell_to_var(Var, Ptag, Vector,
+					TypeMsg, Code)
+		;
+			{ HowToConstruct = reuse_cell(CellToReuse) },
+			{ CellToReuse = cell_to_reuse(ReuseVar,
+					_ReuseConsId, _) },
+			var_locn__reuse_cell(Var, ReuseVar, Ptag, Vector, Code)
+		)
 	).
 
 :- pred var_locn__assign_dynamic_cell_to_var(prog_var::in, tag::in,
@@ -807,6 +820,61 @@
 	var_locn__set_magic_var_location(Var, Lval),
 	var_locn__assign_cell_args(Vector, yes(Ptag), lval(Lval), 0, ArgsCode),
 	{ Code = tree(CellCode, ArgsCode) }.
+
+:- pred var_locn__reuse_cell(prog_var::in, prog_var::in, tag::in,
+	list(maybe(rval))::in, code_tree::out,
+	var_locn_info::in, var_locn_info::out) is det.
+
+var_locn__reuse_cell(Var, ReuseVar, Ptag, Vector, Code) -->
+	var_locn__check_var_is_unknown(Var),
+
+	var_locn__produce_var(ReuseVar, ReuseRval, ReuseCode),
+
+	{ require(tree__is_empty(ReuseCode),
+			"var_locn__reuse_cell: ReuseCode non-empty!") },
+
+	{ ReuseRval = lval(ReuseLval0) ->
+		_ReuseLval = ReuseLval0
+	;
+		error("var_locn__reuse_cell: not an lval")
+	},
+
+	var_locn__select_preferred_reg_or_stack(Var, Lval),
+	var_locn__get_var_name(Var, VarName),
+
+		% XXX we need to worry about the tag!
+		% XXX also look at assign_var_to_var
+	{ CellCode = node([
+		assign(Lval, ReuseRval)
+			- string__append("Reusing cell on heap for ", VarName)
+	]) },
+	var_locn__set_magic_var_location(Var, Lval),
+
+	var_locn__assign_cell_args(Vector, yes(Ptag), lval(Lval), 0, ArgsCode),
+	{ Code = tree(CellCode, ArgsCode) }.
+
+/*
+:- pred var_locn__reuse_cell(prog_var::in, tag::in,
+	list(maybe(rval))::in, string::in, code_tree::out,
+	var_locn_info::in, var_locn_info::out) is det.
+
+var_locn__reuse_cell(Var, Ptag, Vector, TypeMsg, Code) -->
+	var_locn__check_var_is_unknown(Var),
+
+		% XXX Here we want to look up the address of the reuse
+		% var.
+
+	var_locn__select_preferred_reg_or_stack(Var, Lval),
+	var_locn__get_var_name(Var, VarName),
+	{ list__length(Vector, Size) },
+	{ CellCode = node([
+		incr_hp(Lval, yes(Ptag), const(int_const(Size)), TypeMsg)
+			- string__append("Allocating heap for ", VarName)
+	]) },
+	var_locn__set_magic_var_location(Var, Lval),
+	var_locn__assign_cell_args(Vector, yes(Ptag), lval(Lval), 0, ArgsCode),
+	{ Code = tree(CellCode, ArgsCode) }.
+*/
 
 :- pred var_locn__assign_cell_args(list(maybe(rval))::in,
 	maybe(tag)::in, rval::in, int::in, code_tree::out,

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