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+%%
+%% %CopyrightBegin%
+%%
+%% Copyright Ericsson AB 1999-2016. All Rights Reserved.
+%%
+%% 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.
+%%
+%% %CopyrightEnd%
+%%
+%% Purpose : Replace values by aliases from patterns optimisation for Core
+
+%% Replace expressions by aliases from patterns. For example:
+%%
+%% example({ok, Val}) ->
+%% {ok, Val}.
+%%
+%% will become:
+%%
+%% example({ok, Val} = Tuple) ->
+%% Tuple.
+%%
+%% Currently this pass aliases tuple and cons nodes made of literals,
+%% variables and other cons. The tuple/cons may appear anywhere in the
+%% pattern and it will be aliased if used later on.
+%%
+%% Notice a tuple/cons made only of literals is not aliased as it may
+%% be part of the literal pool.
+
+-module(sys_core_alias).
+
+-export([module/2]).
+
+-include("core_parse.hrl").
+
+-define(NOTSET, 0).
+
+-record(sub, {p=#{} :: #{term() => ?NOTSET | atom()}, %% Found pattern substitutions
+ v=cerl_sets:new() :: cerl_sets:set(cerl:var_name()), %% Variables used by patterns
+ t=undefined :: term()}). %% Temporary information from pre to post
+
+-type sub() :: #sub{}.
+
+-spec module(cerl:c_module(), [compile:option()]) ->
+ {'ok',cerl:c_module(),[]}.
+
+module(#c_module{defs=Ds0}=Mod, _Opts) ->
+ Ds1 = [def(D) || D <- Ds0],
+ {ok,Mod#c_module{defs=Ds1},[]}.
+
+def({#c_var{name={F,Arity}}=Name,B0}) ->
+ try
+ put(new_var_num, 0),
+ {B1,_} = cerl_trees:mapfold(fun pre/2, fun post/2, sub_new(undefined), B0),
+ erase(new_var_num),
+ {Name,B1}
+ catch
+ Class:Error:Stack ->
+ io:fwrite("Function: ~w/~w\n", [F,Arity]),
+ erlang:raise(Class, Error, Stack)
+ end.
+
+pre(#c_let{vars=Vars}=Node, Sub) ->
+ {Node,sub_fold(get_variables(Vars), Sub)};
+
+pre(#c_fun{vars=Vars}=Node, Sub) ->
+ {Node,sub_fold(get_variables(Vars), Sub)};
+
+pre(#c_clause{pats=Pats}=Node, Sub0) ->
+ VarNames = get_variables(Pats),
+ Sub1 = sub_fold(VarNames, Sub0),
+ Keys = get_pattern_keys(Pats),
+ Sub2 = sub_add_keys(Keys, Sub1),
+
+ #sub{v=SubNames,t=Temp} = Sub2,
+ Sub3 = Sub2#sub{v=merge_variables(VarNames, SubNames),
+ t={clause,Pats,Keys,SubNames,Temp}},
+
+ {Node#c_clause{pats=[]},Sub3};
+
+pre(Node, Sub0) ->
+ %% We cache only tuples and cons.
+ case cerl:is_data(Node) andalso not cerl:is_literal(Node) of
+ false ->
+ {Node,Sub0};
+ true ->
+ Kind = cerl:data_type(Node),
+ Es = cerl:data_es(Node),
+ case sub_cache_nodes(Kind, Es, Sub0) of
+ {Name,Sub1} ->
+ {cerl:ann_c_var(cerl:get_ann(Node), Name),Sub1};
+ error ->
+ {Node,Sub0}
+ end
+ end.
+
+post(#c_let{}=Node, Sub) ->
+ {Node,sub_unfold(Sub)};
+
+post(#c_fun{}=Node, Sub) ->
+ {Node,sub_unfold(Sub)};
+
+post(#c_clause{}=Node, #sub{t={clause,Pats0,Keys,V,T}}=Sub0) ->
+ {Sub1,PostKeys} = sub_take_keys(Keys, Sub0),
+ Pats1 = put_pattern_keys(Pats0, PostKeys),
+ Sub2 = sub_unfold(Sub1#sub{v=V,t=T}),
+ {Node#c_clause{pats=Pats1},Sub2};
+
+post(Node, Sub) ->
+ {Node,Sub}.
+
+%% sub_new/1
+%% sub_add_keys/2
+%% sub_take_keys/3
+%% sub_cache_nodes/3
+%%
+%% Manages the substitutions record.
+
+%% Builds a new sub.
+-spec sub_new(term()) -> sub().
+sub_new(Temp) ->
+ #sub{t=Temp}.
+
+%% Folds the sub into a new one if the variables in nodes are not disjoint
+sub_fold(VarNames, #sub{v=SubNames}=Sub) ->
+ case is_disjoint_variables(VarNames, SubNames) of
+ true -> Sub#sub{t={temp,Sub#sub.t}};
+ false -> sub_new({sub,Sub})
+ end.
+
+%% Unfolds the sub in case one was folded in the previous step
+sub_unfold(#sub{t={temp,Temp}}=Sub) ->
+ Sub#sub{t=Temp};
+sub_unfold(#sub{t={sub,Sub}}) ->
+ Sub.
+
+%% Adds the keys extracted from patterns to the state.
+-spec sub_add_keys([term()], sub()) -> sub().
+sub_add_keys(Keys, #sub{p=Pat0}=Sub) ->
+ Pat1 =
+ lists:foldl(fun(Key, Acc) ->
+ false = maps:is_key(Key, Acc), %Assertion.
+ maps:put(Key, ?NOTSET, Acc)
+ end, Pat0, Keys),
+ Sub#sub{p=Pat1}.
+
+%% Take the keys from the map taking into account the keys
+%% that have changed as those must become aliases in the pattern.
+-spec sub_take_keys([term()], sub()) -> {sub(), [{term(), atom()}]}.
+sub_take_keys(Keys, #sub{p=Pat0}=Sub) ->
+ {Pat1,Acc} = sub_take_keys(Keys, Pat0, []),
+ {Sub#sub{p=Pat1},Acc}.
+
+sub_take_keys([K|T], Sub0, Acc) ->
+ case maps:take(K, Sub0) of
+ {?NOTSET,Sub1} ->
+ sub_take_keys(T, Sub1, Acc);
+ {Name,Sub1} ->
+ sub_take_keys(T, Sub1, [{K,Name}|Acc])
+ end;
+sub_take_keys([], Sub, Acc) ->
+ {Sub,Acc}.
+
+%% Check if the node can be cached based on the state information.
+%% If it can be cached and it does not have an alias for it, we
+%% build one.
+-spec sub_cache_nodes(atom(), [cerl:cerl()], sub()) -> {atom(), sub()} | error.
+sub_cache_nodes(Kind, Nodes, #sub{p=Pat}=Sub) ->
+ case nodes_to_key(Kind, Nodes) of
+ {ok, Key} ->
+ case Pat of
+ #{Key := ?NOTSET} ->
+ new_var_name(Key, Sub);
+ #{Key := Name} ->
+ {Name,Sub};
+ #{} ->
+ error
+ end;
+ error ->
+ error
+ end.
+
+new_var_name(Key, #sub{p=Pat}=Sub) ->
+ Counter = get(new_var_num),
+ Name = list_to_atom("@r" ++ integer_to_list(Counter)),
+ put(new_var_num, Counter + 1),
+ {Name,Sub#sub{p=maps:put(Key, Name, Pat)}}.
+
+%% get_variables/1
+%% is_disjoint_variables/2
+%% merge_variables/2
+
+get_variables(NodesList) ->
+ cerl_sets:from_list([Var || Node <- NodesList, Var <- cerl_trees:variables(Node)]).
+
+is_disjoint_variables(Vars1, Vars2) ->
+ cerl_sets:is_disjoint(Vars1, Vars2).
+
+merge_variables(Vars1, Vars2) ->
+ cerl_sets:union(Vars1, Vars2).
+
+%% get_pattern_keys/2
+%% put_pattern_keys/2
+%%
+%% Gets keys from patterns or add them as aliases.
+
+get_pattern_keys(Patterns) ->
+ lists:foldl(fun get_pattern_keys/2, [], Patterns).
+
+get_pattern_keys(#c_tuple{es=Es}, Acc0) ->
+ Acc1 = accumulate_pattern_keys(tuple, Es, Acc0),
+ lists:foldl(fun get_pattern_keys/2, Acc1, Es);
+get_pattern_keys(#c_cons{hd=Hd,tl=Tl}, Acc0) ->
+ Acc1 = accumulate_pattern_keys(cons, [Hd, Tl], Acc0),
+ get_pattern_keys(Tl, get_pattern_keys(Hd, Acc1));
+get_pattern_keys(#c_alias{pat=Pat}, Acc0) ->
+ get_pattern_keys(Pat, Acc0);
+get_pattern_keys(#c_map{es=Es}, Acc0) ->
+ lists:foldl(fun get_pattern_keys/2, Acc0, Es);
+get_pattern_keys(#c_map_pair{val=Val}, Acc0) ->
+ get_pattern_keys(Val, Acc0);
+get_pattern_keys(_, Acc) ->
+ Acc.
+
+accumulate_pattern_keys(Kind, Nodes, Acc) ->
+ case nodes_to_key(Kind, Nodes) of
+ {ok,Key} -> [Key|Acc];
+ error -> Acc
+ end.
+
+put_pattern_keys(Patterns, []) ->
+ Patterns;
+put_pattern_keys(Patterns, Keys) ->
+ {NewPatterns,Map} =
+ lists:mapfoldl(fun alias_pattern_keys/2, maps:from_list(Keys), Patterns),
+ %% Check all aliases have been consumed from the map.
+ 0 = map_size(Map),
+ NewPatterns.
+
+alias_pattern_keys(#c_tuple{anno=Anno,es=Es0}=Node, Acc0) ->
+ {Es1,Acc1} = lists:mapfoldl(fun alias_pattern_keys/2, Acc0, Es0),
+ nodes_to_alias(tuple, Es0, Anno, Node#c_tuple{es=Es1}, Acc1);
+alias_pattern_keys(#c_cons{anno=Anno,hd=Hd0,tl=Tl0}=Node, Acc0) ->
+ {Hd1,Acc1} = alias_pattern_keys(Hd0, Acc0),
+ {Tl1,Acc2} = alias_pattern_keys(Tl0, Acc1),
+ nodes_to_alias(cons, [Hd0, Tl0], Anno, Node#c_cons{hd=Hd1,tl=Tl1}, Acc2);
+alias_pattern_keys(#c_alias{pat=Pat0}=Node, Acc0) ->
+ {Pat1,Acc1} = alias_pattern_keys(Pat0, Acc0),
+ {Node#c_alias{pat=Pat1}, Acc1};
+alias_pattern_keys(#c_map{es=Es0}=Node, Acc0) ->
+ {Es1,Acc1} = lists:mapfoldl(fun alias_pattern_keys/2, Acc0, Es0),
+ {Node#c_map{es=Es1}, Acc1};
+alias_pattern_keys(#c_map_pair{val=Val0}=Node, Acc0) ->
+ {Val1,Acc1} = alias_pattern_keys(Val0, Acc0),
+ {Node#c_map_pair{val=Val1}, Acc1};
+alias_pattern_keys(Pattern, Acc) ->
+ {Pattern,Acc}.
+
+%% Check if a node must become an alias because
+%% its pattern was used later on as an expression.
+nodes_to_alias(Kind, Inner, Anno, Node, Keys0) ->
+ case nodes_to_key(Kind, Inner) of
+ {ok,Key} ->
+ case maps:take(Key, Keys0) of
+ {Name,Keys1} ->
+ Var = cerl:ann_c_var(Anno, Name),
+ {cerl:ann_c_alias(Anno, Var, Node), Keys1};
+ error ->
+ {Node,Keys0}
+ end;
+ error ->
+ {Node,Keys0}
+ end.
+
+%% Builds the key used to check if a value can be
+%% replaced by an alias. It considers literals,
+%% aliases, variables, tuples and cons recursively.
+nodes_to_key(Kind, Nodes) ->
+ nodes_to_key(Nodes, [], Kind).
+
+nodes_to_key([#c_alias{var=Var}|T], Acc, Kind) ->
+ nodes_to_key([Var|T], Acc, Kind);
+nodes_to_key([#c_var{name=Name}|T], Acc, Kind) ->
+ nodes_to_key(T, [[var,Name]|Acc], Kind);
+nodes_to_key([Node|T], Acc0, Kind) ->
+ case cerl:is_data(Node) of
+ false ->
+ error;
+ true ->
+ case nodes_to_key(cerl:data_es(Node), [], cerl:data_type(Node)) of
+ {ok,Key} ->
+ nodes_to_key(T, [Key|Acc0], Kind);
+ error ->
+ error
+ end
+ end;
+nodes_to_key([], Acc, Kind) ->
+ {ok,[Kind|Acc]}.
generated by cgit v1.2.3 (git 2.25.1) at 2024-06-03 12:26:19 +0000