aboutsummaryrefslogtreecommitdiffstats
path: root/lib/compiler/src/beam_ssa_recv.erl
diff options
context:
space:
mode:
Diffstat (limited to 'lib/compiler/src/beam_ssa_recv.erl')
-rw-r--r--lib/compiler/src/beam_ssa_recv.erl281
1 files changed, 281 insertions, 0 deletions
diff --git a/lib/compiler/src/beam_ssa_recv.erl b/lib/compiler/src/beam_ssa_recv.erl
new file mode 100644
index 0000000000..82fe006487
--- /dev/null
+++ b/lib/compiler/src/beam_ssa_recv.erl
@@ -0,0 +1,281 @@
+%%
+%% %CopyrightBegin%
+%%
+%% Copyright Ericsson AB 2018. 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%
+%%
+
+-module(beam_ssa_recv).
+-export([module/2]).
+
+%%%
+%%% In code such as:
+%%%
+%%% Ref = make_ref(), %Or erlang:monitor(process, Pid)
+%%% .
+%%% .
+%%% .
+%%% receive
+%%% {Ref,Reply} -> Reply
+%%% end.
+%%%
+%%% we know that none of the messages that exist in the message queue
+%%% before the call to make_ref/0 can be matched out in the receive
+%%% statement. Therefore we can avoid going through the entire message
+%%% queue if we introduce two new instructions (here written as
+%%% BIFs in pseudo-Erlang):
+%%%
+%%% recv_mark(SomeUniqInteger),
+%%% Ref = make_ref(),
+%%% .
+%%% .
+%%% .
+%%% recv_set(SomeUniqInteger),
+%%% receive
+%%% {Ref,Reply} -> Reply
+%%% end.
+%%%
+%%% The recv_mark/1 instruction will save the current position and
+%%% SomeUniqInteger in the process context. The recv_set
+%%% instruction will verify that SomeUniqInteger is still stored
+%%% in the process context. If it is, it will set the current pointer
+%%% for the message queue (the next message to be read out) to the
+%%% position that was saved by recv_mark/1.
+%%%
+%%% The remove_message instruction must be modified to invalidate
+%%% the information stored by the previous recv_mark/1, in case there
+%%% is another receive executed between the calls to recv_mark/1 and
+%%% recv_set/1.
+%%%
+%%% We use a reference to a label (i.e. a position in the loaded code)
+%%% as the SomeUniqInteger.
+%%%
+
+-include("beam_ssa.hrl").
+-import(lists, [all/2,reverse/2]).
+
+-spec module(beam_ssa:b_module(), [compile:option()]) ->
+ {'ok',beam_ssa:b_module()}.
+
+module(#b_module{body=Fs0}=Module, _Opts) ->
+ Fs = [function(F) || F <- Fs0],
+ {ok,Module#b_module{body=Fs}}.
+
+%%%
+%%% Local functions.
+%%%
+
+function(#b_function{anno=Anno,bs=Blocks0}=F) ->
+ try
+ Blocks = opt(Blocks0),
+ F#b_function{bs=Blocks}
+ catch
+ Class:Error:Stack ->
+ #{func_info:={_,Name,Arity}} = Anno,
+ io:fwrite("Function: ~w/~w\n", [Name,Arity]),
+ erlang:raise(Class, Error, Stack)
+ end.
+
+opt(Blocks) ->
+ Linear = beam_ssa:linearize(Blocks),
+ opt(Linear, Blocks, []).
+
+opt([{L,#b_blk{is=[#b_set{op=peek_message}|_]}=Blk0}|Bs], Blocks0, Preds) ->
+ %% Search for a suitable reference creating call in one of the predecessor
+ %% blocks. Whether we find such a call or not, we always clear the
+ %% the list of predecessors to ensure that any nested receive can't
+ %% search above the current receive.
+ case recv_opt(Preds, L, Blocks0) of
+ {yes,Blocks1} ->
+ Blk = beam_ssa:add_anno(recv_set, L, Blk0),
+ Blocks = maps:put(L, Blk, Blocks1),
+ opt(Bs, Blocks, []);
+ no ->
+ opt(Bs, Blocks0, [])
+ end;
+opt([{L,_}|Bs], Blocks, Preds) ->
+ opt(Bs, Blocks, [L|Preds]);
+opt([], Blocks, _) -> Blocks.
+
+recv_opt([L|Ls], RecvLbl, Blocks) ->
+ #b_blk{is=Is0} = Blk0 = maps:get(L, Blocks),
+ case recv_opt_is(Is0, RecvLbl, Blocks, []) of
+ {yes,Is} ->
+ Blk = Blk0#b_blk{is=Is},
+ {yes,maps:put(L, Blk, Blocks)};
+ no ->
+ recv_opt(Ls, RecvLbl, Blocks)
+ end;
+recv_opt([], _, _Blocks) -> no.
+
+recv_opt_is([#b_set{op=call}=I0|Is], RecvLbl, Blocks0, Acc) ->
+ case makes_ref(I0, Blocks0) of
+ no ->
+ recv_opt_is(Is, RecvLbl, Blocks0, [I0|Acc]);
+ {yes,Ref} ->
+ case opt_ref_used(RecvLbl, Ref, Blocks0) of
+ false ->
+ recv_opt_is(Is, RecvLbl, Blocks0, [I0|Acc]);
+ true ->
+ I = beam_ssa:add_anno(recv_mark, RecvLbl, I0),
+ {yes,reverse(Acc, [I|Is])}
+ end
+ end;
+recv_opt_is([I|Is], RecvLbl, Blocks, Acc) ->
+ recv_opt_is(Is, RecvLbl, Blocks, [I|Acc]);
+recv_opt_is([], _, _, _) -> no.
+
+makes_ref(#b_set{dst=#b_var{name=Dst},args=[Func0|_]}, Blocks) ->
+ Func = case Func0 of
+ #b_remote{mod=#b_literal{val=erlang},
+ name=#b_literal{val=Name},arity=A0} ->
+ {Name,A0};
+ _ ->
+ none
+ end,
+ case Func of
+ {make_ref,0} ->
+ {yes,Dst};
+ {monitor,2} ->
+ {yes,Dst};
+ {spawn_monitor,A} when A =:= 1; A =:= 3 ->
+ ref_in_tuple(Dst, Blocks);
+ _ ->
+ no
+ end.
+
+ref_in_tuple(Tuple, Blocks) ->
+ F = fun(#b_set{op=get_tuple_element,dst=#b_var{name=Ref},
+ args=[#b_var{name=Tup},#b_literal{val=1}]}, no)
+ when Tup =:= Tuple -> {yes,Ref};
+ (_, A) -> A
+ end,
+ beam_ssa:fold_instrs_rpo(F, [0], no, Blocks).
+
+opt_ref_used(RecvLbl, Ref, Blocks) ->
+ Vs = #{{var,Ref}=>ref,ref=>Ref,ref_matched=>false},
+ case opt_ref_used_1(RecvLbl, Vs, Blocks) of
+ used -> true;
+ not_used -> false;
+ done -> false
+ end.
+
+opt_ref_used_1(L, Vs0, Blocks) ->
+ #b_blk{is=Is} = Blk = maps:get(L, Blocks),
+ case opt_ref_used_is(Is, Vs0) of
+ #{}=Vs ->
+ opt_ref_used_last(Blk, Vs, Blocks);
+ Result ->
+ Result
+ end.
+
+opt_ref_used_is([#b_set{op=peek_message,dst=#b_var{name=M}}|Is], Vs0) ->
+ Vs = Vs0#{{var,M}=>message},
+ opt_ref_used_is(Is, Vs);
+opt_ref_used_is([#b_set{op={bif,Bif},args=Args,dst=#b_var{name=B}}=I|Is],
+ Vs0) ->
+ S = case Bif of
+ '=:=' -> true;
+ '==' -> true;
+ _ -> none
+ end,
+ case S of
+ none ->
+ Vs = update_vars(I, Vs0),
+ opt_ref_used_is(Is, Vs);
+ Bool when is_boolean(Bool) ->
+ case is_ref_msg_comparison(Args, Vs0) of
+ true ->
+ Vs = Vs0#{B=>{is_ref,Bool}},
+ opt_ref_used_is(Is, Vs);
+ false ->
+ opt_ref_used_is(Is, Vs0)
+ end
+ end;
+opt_ref_used_is([#b_set{op=remove_message}|_], Vs) ->
+ case Vs of
+ #{ref_matched:=true} ->
+ used;
+ #{ref_matched:=false} ->
+ not_used
+ end;
+opt_ref_used_is([#b_set{op=recv_next}|_], _Vs) ->
+ done;
+opt_ref_used_is([#b_set{op=wait_timeout}|_], _Vs) ->
+ done;
+opt_ref_used_is([#b_set{op=wait}|_], _Vs) ->
+ done;
+opt_ref_used_is([#b_set{}=I|Is], Vs0) ->
+ Vs = update_vars(I, Vs0),
+ opt_ref_used_is(Is, Vs);
+opt_ref_used_is([], Vs) -> Vs.
+
+opt_ref_used_last(#b_blk{last=Last}=Blk, Vs, Blocks) ->
+ case Last of
+ #b_br{bool=#b_var{name=Bool},succ=Succ,fail=Fail} ->
+ case Vs of
+ #{Bool:={is_ref,Matched}} ->
+ ref_used_in([{Succ,Vs#{ref_matched:=Matched}},
+ {Fail,Vs#{ref_matched:=not Matched}}],
+ Blocks);
+ #{} ->
+ ref_used_in([{Succ,Vs},{Fail,Vs}], Blocks)
+ end;
+ _ ->
+ SuccVs = [{Succ,Vs} || Succ <- beam_ssa:successors(Blk)],
+ ref_used_in(SuccVs, Blocks)
+ end.
+
+ref_used_in([{L,Vs0}|Ls], Blocks) ->
+ case opt_ref_used_1(L, Vs0, Blocks) of
+ not_used ->
+ not_used;
+ used ->
+ case ref_used_in(Ls, Blocks) of
+ done -> used;
+ Result -> Result
+ end;
+ done -> ref_used_in(Ls, Blocks)
+ end;
+ref_used_in([], _) -> done.
+
+update_vars(#b_set{args=Args,dst=#b_var{name=B}}, Vs) ->
+ Vars = [V || #b_var{name=V} <- Args],
+ All = all(fun(V) ->
+ Var = {var,V},
+ case Vs of
+ #{Var:=message} -> true;
+ #{} -> false
+ end
+ end, Vars),
+ case All of
+ true -> Vs#{{var,B}=>message};
+ false -> Vs
+ end.
+
+%% is_ref_msg_comparison(Args, Variables) -> true|false.
+%% Return 'true' if Args denotes a comparison between the
+%% reference and message or part of the message.
+
+is_ref_msg_comparison([#b_var{name=A1},#b_var{name=A2}], Vs) ->
+ V1 = {var,A1},
+ V2 = {var,A2},
+ case Vs of
+ #{V1:=ref,V2:=message} -> true;
+ #{V1:=message,V2:=ref} -> true;
+ #{} -> false
+ end;
+is_ref_msg_comparison(_, _) -> false.