From 7173fb8984d1822cc9c081f094841fb755f800fc Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= Date: Tue, 21 May 2019 14:48:11 +0200 Subject: 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 --- lib/compiler/src/beam_ssa_pre_codegen.erl | 11 +++++++---- lib/compiler/test/receive_SUITE.erl | 26 ++++++++++++++++++++++++-- 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, <>), ?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. -- cgit v1.2.3