diff options
| -rw-r--r-- | lib/compiler/src/beam_ssa_pre_codegen.erl | 62 | ||||
| -rw-r--r-- | lib/compiler/test/receive_SUITE.erl | 35 |
2 files changed, 79 insertions, 18 deletions
diff --git a/lib/compiler/src/beam_ssa_pre_codegen.erl b/lib/compiler/src/beam_ssa_pre_codegen.erl index 61b2155e39..61c42fdb6d 100644 --- a/lib/compiler/src/beam_ssa_pre_codegen.erl +++ b/lib/compiler/src/beam_ssa_pre_codegen.erl @@ -1544,25 +1544,51 @@ 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([?EXCEPTION_BLOCK | T], OtherPath) -> - %% ?EXCEPTION_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([?EXCEPTION_BLOCK|Ls], RmSet, Dominators) -> + %% ?EXCEPTION_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/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. |