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authorBjörn Gustavsson <[email protected]>2019-05-21 14:48:11 +0200
committerBjörn Gustavsson <[email protected]>2019-05-21 15:32:25 +0200
commit7173fb8984d1822cc9c081f094841fb755f800fc (patch)
tree7c4258089de470fff4ed035ee54d5d79676ed97c
parentd32991afaf3fc5f9f73e3e2448672bb9a1b80101 (diff)
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Eliminate compiler crash when compiling complex receive statements
Certain complex receive statements would result in an internal compiler failure. That would happen when the compiler would fail to find the common exit block following a receive. See the added test case for an example. https://bugs.erlang.org/browse/ERL-950
-rw-r--r--lib/compiler/src/beam_ssa_pre_codegen.erl11
-rw-r--r--lib/compiler/test/receive_SUITE.erl26
2 files changed, 31 insertions, 6 deletions
diff --git a/lib/compiler/src/beam_ssa_pre_codegen.erl b/lib/compiler/src/beam_ssa_pre_codegen.erl
index bf99e8fc26..9af72afca7 100644
--- a/lib/compiler/src/beam_ssa_pre_codegen.erl
+++ b/lib/compiler/src/beam_ssa_pre_codegen.erl
@@ -1415,12 +1415,15 @@ fix_receive([], _Defs, Blocks, Count) ->
find_loop_exit([L1,L2|_Ls], Blocks) ->
Path1 = beam_ssa:rpo([L1], Blocks),
Path2 = beam_ssa:rpo([L2], Blocks),
- find_loop_exit_1(reverse(Path1), reverse(Path2), none);
+ find_loop_exit_1(Path1, cerl_sets:from_list(Path2));
find_loop_exit(_, _) -> none.
-find_loop_exit_1([H|T1], [H|T2], _) ->
- find_loop_exit_1(T1, T2, H);
-find_loop_exit_1(_, _, Exit) -> Exit.
+find_loop_exit_1([H|T], OtherPath) ->
+ case cerl_sets:is_element(H, OtherPath) of
+ true -> H;
+ false -> find_loop_exit_1(T, OtherPath)
+ end;
+find_loop_exit_1([], _) -> none.
%% find_rm_blocks(StartLabel, Blocks) -> [Label].
%% Find all blocks that start with remove_message within the receive
diff --git a/lib/compiler/test/receive_SUITE.erl b/lib/compiler/test/receive_SUITE.erl
index 0038eb1a4b..752491f0f8 100644
--- a/lib/compiler/test/receive_SUITE.erl
+++ b/lib/compiler/test/receive_SUITE.erl
@@ -26,7 +26,7 @@
init_per_testcase/2,end_per_testcase/2,
export/1,recv/1,coverage/1,otp_7980/1,ref_opt/1,
wait/1,recv_in_try/1,double_recv/1,receive_var_zero/1,
- match_built_terms/1]).
+ match_built_terms/1,elusive_common_exit/1]).
-include_lib("common_test/include/ct.hrl").
@@ -47,7 +47,7 @@ groups() ->
[{p,test_lib:parallel(),
[recv,coverage,otp_7980,ref_opt,export,wait,
recv_in_try,double_recv,receive_var_zero,
- match_built_terms]}].
+ match_built_terms,elusive_common_exit]}].
init_per_suite(Config) ->
@@ -427,4 +427,26 @@ match_built_terms(Config) when is_list(Config) ->
?MATCH_BUILT_TERM(Ref, <<A, B>>),
?MATCH_BUILT_TERM(Ref, #{ 1 => A, 2 => B}).
+elusive_common_exit(_Config) ->
+ self() ! {1, a},
+ self() ! {2, b},
+ {[z], [{2,b},{1,a}]} = elusive_loop([x,y,z], 2, []),
+ ok.
+
+elusive_loop(List, 0, Results) ->
+ {List, Results};
+elusive_loop(List, ToReceive, Results) ->
+ {Result, RemList} =
+ receive
+ {_Pos, _R} = Res when List =/= [] ->
+ [_H|T] = List,
+ {Res, T};
+ {_Pos, _R} = Res when List =:= [] ->
+ {Res, []}
+ end,
+ %% beam_ssa_pre_codegen:fix_receives() would fail to find
+ %% the common exit block for this receive. That would mean
+ %% that it would not insert all necessary copy instructions.
+ elusive_loop(RemList, ToReceive-1, [Result | Results]).
+
id(I) -> I.