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-rw-r--r--lib/compiler/test/beam_ssa_SUITE.erl60
1 files changed, 58 insertions, 2 deletions
diff --git a/lib/compiler/test/beam_ssa_SUITE.erl b/lib/compiler/test/beam_ssa_SUITE.erl
index 15cf9bcbf3..a741ebbdf9 100644
--- a/lib/compiler/test/beam_ssa_SUITE.erl
+++ b/lib/compiler/test/beam_ssa_SUITE.erl
@@ -22,7 +22,8 @@
-export([all/0,suite/0,groups/0,init_per_suite/1,end_per_suite/1,
init_per_group/2,end_per_group/2,
calls/1,tuple_matching/1,recv/1,maps/1,
- cover_ssa_dead/1,combine_sw/1,share_opt/1]).
+ cover_ssa_dead/1,combine_sw/1,share_opt/1,
+ beam_ssa_dead_crash/1]).
suite() -> [{ct_hooks,[ts_install_cth]}].
@@ -37,7 +38,8 @@ groups() ->
maps,
cover_ssa_dead,
combine_sw,
- share_opt
+ share_opt,
+ beam_ssa_dead_crash
]}].
init_per_suite(Config) ->
@@ -492,6 +494,60 @@ do_share_opt(A) ->
end,
receive after 1 -> ok end.
+beam_ssa_dead_crash(_Config) ->
+ not_A_B = do_beam_ssa_dead_crash(id(false), id(true)),
+ not_A_not_B = do_beam_ssa_dead_crash(false, false),
+ neither = do_beam_ssa_dead_crash(true, false),
+ neither = do_beam_ssa_dead_crash(true, true),
+ ok.
+
+do_beam_ssa_dead_crash(A, B) ->
+ %% beam_ssa_dead attempts to shortcut branches that branch other
+ %% branches. When a two-way branch is encountered, beam_ssa_dead
+ %% will simulate execution along both paths, in the hope that both
+ %% paths happens to end up in the same place.
+ %%
+ %% During the simulated execution of this function, the boolean
+ %% varible for a `br` instruction would be replaced with the
+ %% literal atom `nil`, which is not allowed, and would crash the
+ %% compiler. In practice, during the actual execution, control
+ %% would never be transferred to that `br` instruction when the
+ %% variable in question had the value `nil`.
+ %%
+ %% beam_ssa_dead has been updated to immediately abort the search
+ %% along the current path if there is an attempt to substitute a
+ %% non-boolean value into a `br` instruction.
+
+ case
+ case not A of
+ false ->
+ false;
+ true ->
+ B
+ end
+ of
+ V
+ when
+ V /= nil
+ andalso
+ V /= false ->
+ not_A_B;
+ _ ->
+ case
+ case not A of
+ false ->
+ false;
+ true ->
+ not B
+ end
+ of
+ true ->
+ not_A_not_B;
+ false ->
+ neither
+ end
+ end.
+
%% The identity function.
id(I) -> I.