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-rw-r--r--lib/compiler/src/beam_except.erl32
-rw-r--r--lib/compiler/src/beam_ssa_pre_codegen.erl62
-rw-r--r--lib/compiler/test/beam_except_SUITE.erl14
-rw-r--r--lib/compiler/test/receive_SUITE.erl35
4 files changed, 113 insertions, 30 deletions
diff --git a/lib/compiler/src/beam_except.erl b/lib/compiler/src/beam_except.erl
index 2305502800..2b9c1b0cf5 100644
--- a/lib/compiler/src/beam_except.erl
+++ b/lib/compiler/src/beam_except.erl
@@ -152,7 +152,7 @@ dig_out_fc(Arity, Is0) ->
({test,_,_,_}) -> false;
(_) -> true
end, Is0),
- {Regs,Acc} = dig_out_fc_1(reverse(Is), Regs0, Acc0),
+ {Regs,Acc} = dig_out_fc_1(reverse(Is), Arity, Regs0, Acc0),
case Regs of
#{{x,0}:={atom,function_clause},{x,1}:=Args} ->
case moves_from_stack(Args, 0, []) of
@@ -165,19 +165,27 @@ dig_out_fc(Arity, Is0) ->
no
end.
-dig_out_fc_1([{block,Bl}|Is], Regs0, Acc) ->
+dig_out_fc_1([{block,Bl}|Is], Arity, Regs0, Acc) ->
Regs = dig_out_fc_block(Bl, Regs0),
- dig_out_fc_1(Is, Regs, Acc);
-dig_out_fc_1([{bs_set_position,_,_}=I|Is], Regs, Acc) ->
- dig_out_fc_1(Is, Regs, [I|Acc]);
-dig_out_fc_1([{bs_get_tail,Src,Dst,Live0}|Is], Regs0, Acc) ->
- Regs = prune_xregs(Live0, Regs0),
- Live = dig_out_stack_live(Regs, Live0),
- I = {bs_get_tail,Src,Dst,Live},
- dig_out_fc_1(Is, Regs, [I|Acc]);
-dig_out_fc_1([_|_], _Regs, _Acc) ->
+ dig_out_fc_1(Is, Arity, Regs, Acc);
+dig_out_fc_1([{bs_set_position,_,_}=I|Is], Arity, Regs, Acc) ->
+ dig_out_fc_1(Is, Arity, Regs, [I|Acc]);
+dig_out_fc_1([{bs_get_tail,Src,Dst,Live0}|Is], Arity, Regs0, Acc) ->
+ case Src of
+ {x,X} when X < Arity ->
+ %% The heuristic for determining the number of live
+ %% registers is likely to give an incorrect result.
+ %% Give up.
+ {#{},[]};
+ _ ->
+ Regs = prune_xregs(Live0, Regs0),
+ Live = dig_out_stack_live(Regs, Live0),
+ I = {bs_get_tail,Src,Dst,Live},
+ dig_out_fc_1(Is, Arity, Regs, [I|Acc])
+ end;
+dig_out_fc_1([_|_], _Arity, _Regs, _Acc) ->
{#{},[]};
-dig_out_fc_1([], Regs, Acc) ->
+dig_out_fc_1([], _Arity, Regs, Acc) ->
{Regs,Acc}.
dig_out_fc_block([{set,[],[],{alloc,Live,_}}|Is], Regs0) ->
diff --git a/lib/compiler/src/beam_ssa_pre_codegen.erl b/lib/compiler/src/beam_ssa_pre_codegen.erl
index 7ef604d444..7f816b9802 100644
--- a/lib/compiler/src/beam_ssa_pre_codegen.erl
+++ b/lib/compiler/src/beam_ssa_pre_codegen.erl
@@ -1463,25 +1463,51 @@ fix_receive([], _Defs, Blocks, Count) ->
{Blocks,Count}.
%% find_loop_exit([Label], Blocks) -> Label | none.
-%% Find the block to which control is transferred when the
-%% the receive loop is exited.
-
-find_loop_exit([L1,L2|_Ls], Blocks) ->
- Path1 = beam_ssa:rpo([L1], Blocks),
- Path2 = beam_ssa:rpo([L2], Blocks),
- find_loop_exit_1(Path1, cerl_sets:from_list(Path2));
-find_loop_exit(_, _) -> none.
-
-find_loop_exit_1([?BADARG_BLOCK | T], OtherPath) ->
- %% ?BADARG_BLOCK is a marker and not an actual block, so we can't consider
- %% it to be a common block even if both paths cross it.
- find_loop_exit_1(T, OtherPath);
-find_loop_exit_1([H|T], OtherPath) ->
- case cerl_sets:is_element(H, OtherPath) of
- true -> H;
- false -> find_loop_exit_1(T, OtherPath)
+%% Given the list of all blocks with the remove_message instructions
+%% for this receive, find the block to which control is transferred
+%% when the receive loop is exited (if any).
+
+find_loop_exit([_,_|_]=RmBlocks, Blocks) ->
+ %% We used to only analyze the path from two of the remove_message
+ %% blocks. That would fail to find a common block if one or both
+ %% of the blocks happened to raise an exception. To be sure that
+ %% we always find a common block if there is one (shared by at
+ %% least two clauses), we must analyze the path from all
+ %% remove_message blocks.
+ {Dominators,_} = beam_ssa:dominators(Blocks),
+ RmSet = cerl_sets:from_list(RmBlocks),
+ Rpo = beam_ssa:rpo(RmBlocks, Blocks),
+ find_loop_exit_1(Rpo, RmSet, Dominators);
+find_loop_exit(_, _) ->
+ %% There is (at most) a single clause. There is no common
+ %% loop exit block.
+ none.
+
+find_loop_exit_1([?BADARG_BLOCK|Ls], RmSet, Dominators) ->
+ %% ?BADARG_BLOCK is a marker and not an actual block, so it is not
+ %% the block we are looking for.
+ find_loop_exit_1(Ls, RmSet, Dominators);
+find_loop_exit_1([L|Ls], RmSet, Dominators) ->
+ DomBy = map_get(L, Dominators),
+ case any(fun(E) -> cerl_sets:is_element(E, RmSet) end, DomBy) of
+ true ->
+ %% This block is dominated by one of the remove_message blocks,
+ %% which means that the block is part of only one clause.
+ %% It is not the block we are looking for.
+ find_loop_exit_1(Ls, RmSet, Dominators);
+ false ->
+ %% This block is the first block that is not dominated by
+ %% any of the blocks with remove_message instructions,
+ %% which means that at least two of the receive clauses
+ %% will ultimately transfer control to it. It is the block
+ %% we are looking for.
+ L
end;
-find_loop_exit_1([], _) -> none.
+find_loop_exit_1([], _, _) ->
+ %% None of clauses transfers control to a common block after the receive
+ %% statement. That means that the receive statement is a the end of a
+ %% function (or that all clauses raise exceptions).
+ none.
%% find_rm_blocks(StartLabel, Blocks) -> [Label].
%% Find all blocks that start with remove_message within the receive
diff --git a/lib/compiler/test/beam_except_SUITE.erl b/lib/compiler/test/beam_except_SUITE.erl
index 67947dc292..f52239f2a8 100644
--- a/lib/compiler/test/beam_except_SUITE.erl
+++ b/lib/compiler/test/beam_except_SUITE.erl
@@ -72,11 +72,25 @@ bs_get_tail(Config) ->
{function_clause,
[{?MODULE,bs_get_tail_1,[<<>>,0,0,Config],_}|_]}} =
(catch bs_get_tail_1(id(<<>>), 0, 0, Config)),
+
+ ok = bs_get_tail_2(<<"W">>, <<"X">>, <<"Z">>),
+ ok = bs_get_tail_2(<<"M">>, <<"X">>, <<"Z">>),
+ {'EXIT',
+ {function_clause,
+ [{?MODULE,do_get_bs_tail_2,[<<"A">>,<<"B">>,[],<<"C">>],_}|_]}} =
+ (catch bs_get_tail_2(<<"A">>, <<"B">>, <<"C">>)),
+
ok.
bs_get_tail_1(<<_:32, Rest/binary>>, Z1, Z2, F1) ->
{Rest,Z1,Z2,F1}.
+bs_get_tail_2(A, B, C) ->
+ do_get_bs_tail_2(A, B, [], C).
+
+do_get_bs_tail_2(<<"W">>, <<"X">>, _, <<"Z">>) -> ok;
+do_get_bs_tail_2(<<"M">>, <<"X">>, _, <<"Z">>) -> ok.
+
coverage(_) ->
File = {file,"fake.erl"},
ok = fc(a),
diff --git a/lib/compiler/test/receive_SUITE.erl b/lib/compiler/test/receive_SUITE.erl
index 752491f0f8..8cd864c59e 100644
--- a/lib/compiler/test/receive_SUITE.erl
+++ b/lib/compiler/test/receive_SUITE.erl
@@ -431,6 +431,20 @@ elusive_common_exit(_Config) ->
self() ! {1, a},
self() ! {2, b},
{[z], [{2,b},{1,a}]} = elusive_loop([x,y,z], 2, []),
+
+ CodeServer = whereis(code_server),
+ Self = self(),
+ Self ! {Self, abc},
+ Self ! {CodeServer, []},
+ Self ! {Self, other},
+ try elusive2([]) of
+ Unexpected ->
+ ct:fail("Expected an exception; got ~p\n", [Unexpected])
+ catch
+ throw:[other, CodeServer, Self] ->
+ ok
+ end,
+
ok.
elusive_loop(List, 0, Results) ->
@@ -449,4 +463,25 @@ elusive_loop(List, ToReceive, Results) ->
%% that it would not insert all necessary copy instructions.
elusive_loop(RemList, ToReceive-1, [Result | Results]).
+
+elusive2(Acc) ->
+ receive
+ {Pid, abc} ->
+ ok;
+ {Pid, []} ->
+ ok;
+ {Pid, Res} ->
+ %% beam_ssa_pre_codegen:find_loop_exit/2 attempts to find
+ %% the first block of the common code after the receive
+ %% statement. It used to only look at the two last clauses
+ %% of the receive. In this function, the last two clauses
+ %% don't have any common block, so it would be assumed
+ %% that there was no common block for any of the
+ %% clauses. That would mean that copy instructions would
+ %% not be inserted as needed.
+ throw([Res | Acc])
+ end,
+ %% Common code.
+ elusive2([Pid | Acc]).
+
id(I) -> I.
generated by cgit v1.2.3 (git 2.25.1) at 2024-08-09 01:12:48 +0000