Merge branch 'bg/opt-receive' into dev

* bg/opt-receive:
  Test that gen_server:call/2,3 are fast even with a huge message queue
  erts: Add tests for the receive optimization
  Update primary bootstrap
  erts: Implement recv_mark/1 and recv_set/1 for real
  compiler tests: Cover the error handling code in beam_receive
  compiler test: Test optimization of receive statements
  Optimize selective receives in the presence of a large message queue
  Introduce the new recv_mark/1 and recv_mark/1 instructions
  Compile tests that communicate with R12 nodes with the r12 option
  Move p_run/2 to test_lib
  gen: Inline wait_resp_mon/2 to help the compiler optimize

OTP-8623 bg/opt-receive

reveive statements that can only read out a newly created reference are now
specially optimized so that it will execute in constant time regardless of
the number of messages in the receive queue for the process. That
optimization will benefit calls to gen_server:call(). (See gen:do_call/4
for an example of a receive statement that will be optimized.)

1 files changed, 388 insertions, 0 deletions

diff --git a/lib/compiler/src/beam_receive.erl b/lib/compiler/src/beam_receive.erl
new file mode 100644
index 0000000000..9ed44ad5d7
--- /dev/null
+++ b/lib/compiler/src/beam_receive.erl
@@ -0,0 +1,388 @@
+%%
+%% %CopyrightBegin%
+%%
+%% Copyright Ericsson AB 2010. All Rights Reserved.
+%%
+%% The contents of this file are subject to the Erlang Public License,
+%% Version 1.1, (the "License"); you may not use this file except in
+%% compliance with the License. You should have received a copy of the
+%% Erlang Public License along with this software. If not, it can be
+%% retrieved online at http://www.erlang.org/.
+%%
+%% Software distributed under the License is distributed on an "AS IS"
+%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+%% the License for the specific language governing rights and limitations
+%% under the License.
+%%
+%% %CopyrightEnd%
+%%
+
+-module(beam_receive).
+-export([module/2]).
+-import(lists, [foldl/3,reverse/1,reverse/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.
+%%%
+
+module({Mod,Exp,Attr,Fs0,Lc}, _Opts) ->
+    Fs = [function(F) || F <- Fs0],
+    Code = {Mod,Exp,Attr,Fs,Lc},
+    {ok,Code}.
+
+%%%
+%%% Local functions.
+%%%
+
+function({function,Name,Arity,Entry,Is}) ->
+    try
+	D = beam_utils:index_labels(Is),
+	{function,Name,Arity,Entry,opt(Is, D, [])}
+    catch
+	Class:Error ->
+	    Stack = erlang:get_stacktrace(),
+	    io:fwrite("Function: ~w/~w\n", [Name,Arity]),
+	    erlang:raise(Class, Error, Stack)
+    end.
+
+opt([{call_ext,Arity,{extfunc,erlang,Name,Arity}}=I|Is0], D, Acc) ->
+    case creates_new_ref(Name, Arity) of
+	true ->
+	    %% The call creates a brand new reference. Now
+	    %% search for a receive statement in the same
+	    %% function that will match against the reference.
+	    case opt_recv(Is0, D) of
+		no ->
+		    opt(Is0, D, [I|Acc]);
+		{yes,Is,Lbl} ->
+		    opt(Is, D, [I,{recv_mark,{f,Lbl}}|Acc])
+	    end;
+	false ->
+	    opt(Is0, D, [I|Acc])
+    end;
+opt([I|Is], D, Acc) ->
+    opt(Is, D, [I|Acc]);
+opt([], _, Acc) ->
+    reverse(Acc).
+
+%% creates_new_ref(Name, Arity) -> true|false.
+%%  Return 'true' if the BIF Name/Arity will create a new reference.
+creates_new_ref(monitor, 2) -> true;
+creates_new_ref(make_ref, 0) -> true;
+creates_new_ref(_, _) -> false.
+
+%% opt_recv([Instruction], LabelIndex) -> no|{yes,[Instruction]}
+%%  Search for a receive statement that will only retrieve messages
+%%  that contain the newly created reference (which is currently in {x,0}).
+opt_recv(Is, D) ->
+    R = regs_init_x0(),
+    L = gb_sets:empty(),
+    opt_recv(Is, D, R, L, []).
+
+opt_recv([{label,L}=Lbl,{loop_rec,{f,Fail},_}=Loop|Is], D, R0, _, Acc) ->
+    R = regs_kill_not_live(0, R0),
+    case regs_to_list(R) of
+	[{y,_}=RefReg] ->
+	    %% We now have the new reference in the Y register RefReg
+	    %% and the current instruction is the beginning of a
+	    %% receive statement. We must now verify that only messages
+	    %% that contain the reference will be matched.
+	    case opt_ref_used(Is, RefReg, Fail, D) of
+		false ->
+		    no;
+		true ->
+		    RecvSet = {recv_set,{f,L}},
+		    {yes,reverse(Acc, [RecvSet,Lbl,Loop|Is]),L}
+	    end;
+	[] ->
+	    no
+    end;
+opt_recv([I|Is], D, R0, L0, Acc) ->
+    {R,L} = opt_update_regs(I, R0, L0),
+    case regs_empty(R) of
+	true ->
+	    %% The reference is no longer alive. There is no
+	    %% point in continuing the search.
+	    no;
+	false ->
+	    opt_recv(Is, D, R, L, [I|Acc])
+    end.
+
+opt_update_regs({block,Bl}, R, L) ->
+    {opt_update_regs_bl(Bl, R),L};
+opt_update_regs({call,_,_}, R, L) ->
+    {regs_kill_not_live(0, R),L};
+opt_update_regs({call_ext,_,_}, R, L) ->
+    {regs_kill_not_live(0, R),L};
+opt_update_regs({call_fun,_}, R, L) ->
+    {regs_kill_not_live(0, R),L};
+opt_update_regs({kill,Y}, R, L) ->
+    {regs_kill([Y], R),L};
+opt_update_regs(send, R, L) ->
+    {regs_kill_not_live(0, R),L};
+opt_update_regs({'catch',_,{f,Lbl}}, R, L) ->
+    {R,gb_sets:add(Lbl, L)};
+opt_update_regs({catch_end,_}, R, L) ->
+    {R,L};
+opt_update_regs({label,Lbl}, R, L) ->
+    case gb_sets:is_member(Lbl, L) of
+	false ->
+	    %% We can't allow arbitrary labels (since the receive
+	    %% could be entered without first creating the reference).
+	    {regs_init(),L};
+	true ->
+	    %% A catch label for a previously seen catch instruction is OK.
+	    {R,L}
+    end;
+opt_update_regs({try_end,_}, R, L) ->
+    {R,L};
+opt_update_regs(_I, _R, L) ->
+    %% Unrecognized instruction. Abort the search.
+    {regs_init(),L}.
+
+opt_update_regs_bl([{set,Ds,_,{alloc,Live,_}}|Is], Regs0) ->
+    Regs1 = regs_kill_not_live(Live, Regs0),
+    Regs = regs_kill(Ds, Regs1),
+    opt_update_regs_bl(Is, Regs);
+opt_update_regs_bl([{set,[Dst]=Ds,[Src],move}|Is], Regs0) ->
+    Regs1 = regs_kill(Ds, Regs0),
+    Regs = case regs_is_member(Src, Regs1) of
+	       false -> Regs1;
+	       true -> regs_add(Dst, Regs1)
+	   end,
+    opt_update_regs_bl(Is, Regs);
+opt_update_regs_bl([{set,Ds,_,_}|Is], Regs0) ->
+    Regs = regs_kill(Ds, Regs0),
+    opt_update_regs_bl(Is, Regs);
+opt_update_regs_bl([], Regs) -> Regs.
+
+%% opt_ref_used([Instruction], RefRegister, FailLabel, LabelIndex) -> true|false
+%%  Return 'true' if it is certain that only messages that contain the same
+%%  reference as in RefRegister can be matched out. Otherwise return 'false'.
+%%
+%%  Basically, we follow all possible paths through the receive statement.
+%%  If all paths are safe, we return 'true'.
+%%
+%%  A branch to FailLabel is safe, because it exits the receive statement
+%%  and no further message may be matched out.
+%%
+%%  If a path hits an comparision between RefRegister and part of the message,
+%%  that path is safe (any messages that may be matched further down the
+%%  path is guaranteed to contain the reference).
+%%
+%%  Otherwise, if we hit a 'remove_message' instruction, we give up
+%%  and return 'false' (the optimization is definitely unsafe). If
+%%  we hit an unrecognized instruction, we also give up and return
+%%  'false' (the optimization may be unsafe).
+
+opt_ref_used(Is, RefReg, Fail, D) ->
+    Done = gb_sets:singleton(Fail),
+    Regs = regs_init_x0(),
+    try
+	opt_ref_used_1(Is, RefReg, D, Done, Regs),
+	true
+    catch
+	throw:not_used ->
+	    false
+    end.
+
+%% This functions only returns if all paths through the receive
+%% statement are safe, and throws an 'not_used' term otherwise.
+opt_ref_used_1([{block,Bl}|Is], RefReg, D, Done, Regs0) ->
+    Regs = opt_ref_used_bl(Bl, Regs0),
+    opt_ref_used_1(Is, RefReg, D, Done, Regs);
+opt_ref_used_1([{test,is_eq_exact,{f,Fail},Args}|Is], RefReg, D, Done0, Regs) ->
+    Done = opt_ref_used_at(Fail, RefReg, D, Done0, Regs),
+    case is_ref_msg_comparison(Args, RefReg, Regs) of
+	false ->
+	    opt_ref_used_1(Is, RefReg, D, Done, Regs);
+	true ->
+	    %% The instructions that follow (Is) can only be executed
+	    %% if the message contains the same reference as in RefReg.
+	    Done
+    end;
+opt_ref_used_1([{test,is_ne_exact,{f,Fail},Args}|Is], RefReg, D, Done0, Regs) ->
+    Done = opt_ref_used_1(Is, RefReg, D, Done0, Regs),
+    case is_ref_msg_comparison(Args, RefReg, Regs) of
+	false ->
+	    opt_ref_used_at(Fail, RefReg, D, Done, Regs);
+	true ->
+	    Done
+    end;
+opt_ref_used_1([{test,_,{f,Fail},_}|Is], RefReg, D, Done0, Regs) ->
+    Done = opt_ref_used_at(Fail, RefReg, D, Done0, Regs),
+    opt_ref_used_1(Is, RefReg, D, Done, Regs);
+opt_ref_used_1([{select_tuple_arity,_,{f,Fail},{list,List}}|_], RefReg, D, Done, Regs) ->
+    Lbls = [F || {f,F} <- List] ++ [Fail],
+    opt_ref_used_in_all(Lbls, RefReg, D, Done, Regs);
+opt_ref_used_1([{select_val,_,{f,Fail},{list,List}}|_], RefReg, D, Done, Regs) ->
+    Lbls = [F || {f,F} <- List] ++ [Fail],
+    opt_ref_used_in_all(Lbls, RefReg, D, Done, Regs);
+opt_ref_used_1([{label,Lbl}|Is], RefReg, D, Done, Regs) ->
+    case gb_sets:is_member(Lbl, Done) of
+	true -> Done;
+	false -> opt_ref_used_1(Is, RefReg, D, Done, Regs)
+    end;
+opt_ref_used_1([{loop_rec_end,_}|_], _, _, Done, _) ->
+    Done;
+opt_ref_used_1([_I|_], _RefReg, _D, _Done, _Regs) ->
+    %% The optimization may be unsafe.
+    throw(not_used).
+
+%% is_ref_msg_comparison(Args, RefReg, RegisterSet) -> true|false.
+%%  Return 'true' if Args denotes a comparison between the
+%%  reference and message or part of the message.
+is_ref_msg_comparison([R,RefReg], RefReg, Regs) ->
+    regs_is_member(R, Regs);
+is_ref_msg_comparison([RefReg,R], RefReg, Regs) ->
+    regs_is_member(R, Regs);
+is_ref_msg_comparison([_,_], _, _) -> false.
+
+opt_ref_used_in_all([L|Ls], RefReg, D, Done0, Regs) ->
+    Done = opt_ref_used_at(L, RefReg, D, Done0, Regs),
+    opt_ref_used_in_all(Ls, RefReg, D, Done, Regs);
+opt_ref_used_in_all([], _, _, Done, _) -> Done.
+
+opt_ref_used_at(Fail, RefReg, D, Done0, Regs) ->
+    case gb_sets:is_member(Fail, Done0) of
+	true ->
+	    Done0;
+	false ->
+	    Is = beam_utils:code_at(Fail, D),
+	    Done = opt_ref_used_1(Is, RefReg, D, Done0, Regs),
+	    gb_sets:add(Fail, Done)
+    end.
+
+opt_ref_used_bl([{set,[],[],remove_message}|_], _) ->
+    %% We have proved that a message that does not depend on the
+    %% reference can be matched out.
+    throw(not_used);
+opt_ref_used_bl([{set,Ds,Ss,_}|Is], Regs0) ->
+    case regs_all_members(Ss, Regs0) of
+	false ->
+	    %% The destination registers may be assigned values that
+	    %% are not dependent on the message being matched.
+	    Regs = regs_kill(Ds, Regs0),
+	    opt_ref_used_bl(Is, Regs);
+	true ->
+	    %% All the sources depend on the message directly or
+	    %% indirectly.
+	    Regs = regs_add_list(Ds, Regs0),
+	    opt_ref_used_bl(Is, Regs)
+    end;
+opt_ref_used_bl([], Regs) -> Regs.
+
+%%%
+%%% Functions for keeping track of a set of registers.
+%%%
+
+%% regs_init() -> RegisterSet
+%%  Return an empty set of registers.
+
+regs_init() ->
+    {0,0}.
+
+%% regs_init_x0() -> RegisterSet
+%%  Return a set that only contains the {x,0} register.
+
+regs_init_x0() ->
+    {1 bsl 0,0}.
+
+%% regs_empty(Register) -> true|false
+%%  Test whether the register set is empty.
+
+regs_empty(R) ->
+    R =:= {0,0}.
+
+%% regs_kill_not_live(Live, RegisterSet) -> RegisterSet'
+%%  Kill all registers indicated not live by Live.
+
+regs_kill_not_live(Live, {Xregs,Yregs}) ->
+    {Xregs band ((1 bsl Live)-1),Yregs}.
+
+%% regs_kill([Register], RegisterSet) -> RegisterSet'
+%%  Kill all registers mentioned in the list of registers.
+
+regs_kill([{x,N}|Rs], {Xregs,Yregs}) ->
+    regs_kill(Rs, {Xregs band (bnot (1 bsl N)),Yregs});
+regs_kill([{y,N}|Rs], {Xregs,Yregs}) ->
+    regs_kill(Rs, {Xregs,Yregs band (bnot (1 bsl N))});
+regs_kill([{fr,_}|Rs], Regs) ->
+    regs_kill(Rs, Regs);
+regs_kill([], Regs) -> Regs.
+
+regs_add_list(List, Regs) ->
+    foldl(fun(R, A) -> regs_add(R, A) end, Regs, List).
+
+%% regs_add(Register, RegisterSet) -> RegisterSet'
+%%  Add a new register to the set of registers.
+
+regs_add({x,N}, {Xregs,Yregs}) ->
+    {Xregs bor (1 bsl N),Yregs};
+regs_add({y,N}, {Xregs,Yregs}) ->
+    {Xregs,Yregs bor (1 bsl N)}.
+
+%% regs_all_members([Register], RegisterSet) -> true|false
+%%  Test whether all of the registers are part of the register set.
+
+regs_all_members([R|Rs], Regs) ->
+    regs_is_member(R, Regs) andalso regs_all_members(Rs, Regs);
+regs_all_members([], _) -> true.
+
+%% regs_is_member(Register, RegisterSet) -> true|false
+%%  Test whether Register is part of the register set.
+
+regs_is_member({x,N}, {Regs,_}) -> Regs band (1 bsl N) =/= 0;
+regs_is_member({y,N}, {_,Regs}) -> Regs band (1 bsl N) =/= 0;
+regs_is_member(_, _) -> false.
+
+%% regs_to_list(RegisterSet) -> [Register]
+%%  Convert the register set to an explicit list of registers.
+regs_to_list({Xregs,Yregs}) ->
+    regs_to_list_1(Xregs, 0, x, regs_to_list_1(Yregs, 0, y, [])).
+
+regs_to_list_1(0, _, _, Acc) ->
+    Acc;
+regs_to_list_1(Regs, N, Tag, Acc) when (Regs band 1) =:= 1 ->
+    regs_to_list_1(Regs bsr 1, N+1, Tag, [{Tag,N}|Acc]);
+regs_to_list_1(Regs, N, Tag, Acc) ->
+    regs_to_list_1(Regs bsr 1, N+1, Tag, Acc).