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Diffstat (limited to 'lib/compiler/src/beam_ssa_recv.erl')
| -rw-r--r-- | lib/compiler/src/beam_ssa_recv.erl | 281 |
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. |