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authorBjörn Gustavsson <[email protected]>2016-08-01 17:06:40 +0200
committerBjörn Gustavsson <[email protected]>2016-08-05 10:58:12 +0200
commit921cf991e09698d63d0f4f9a20bf2cfc23b2e896 (patch)
tree7513a85a22254cedc97bf95d4fdb64a61166cf53 /lib/compiler/test
parent6dcf9c56c648bb6fa2f0e27bdf6429eab23fdd8c (diff)
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beam_block: Fix potentially unsafe optimization in move_allocates/1
beam_block has an optimization that only is safe when it is applied immediately after code generation. That is pointed out in a comment: NOTE: Moving allocation instructions is only safe because it is done immediately after code generation so that we KNOW that if {x,X} is initialized, all x registers with lower numbers are also initialized. That assumption may not be true after other optimizations, such as the beam_utils:live_opt/1 optimization. The new beam_reorder pass added in OTP 19 runs before beam_block. Therefore, the optimization is potentially unsafe. The optimization is also unsafe if compilation is started from assembly code in a .S file. Rewrite the optimization to make it safe. See the newly added comment for details. ERL-202
Diffstat (limited to 'lib/compiler/test')
-rw-r--r--lib/compiler/test/beam_block_SUITE.erl27
1 files changed, 25 insertions, 2 deletions
diff --git a/lib/compiler/test/beam_block_SUITE.erl b/lib/compiler/test/beam_block_SUITE.erl
index 4bcb252833..9fcb6e497d 100644
--- a/lib/compiler/test/beam_block_SUITE.erl
+++ b/lib/compiler/test/beam_block_SUITE.erl
@@ -21,7 +21,8 @@
-export([all/0,suite/0,groups/0,init_per_suite/1,end_per_suite/1,
init_per_group/2,end_per_group/2,
- get_map_elements/1,otp_7345/1,move_opt_across_gc_bif/1]).
+ get_map_elements/1,otp_7345/1,move_opt_across_gc_bif/1,
+ erl_202/1]).
%% The only test for the following functions is that
%% the code compiles and is accepted by beam_validator.
@@ -37,7 +38,8 @@ groups() ->
[{p,[parallel],
[get_map_elements,
otp_7345,
- move_opt_across_gc_bif
+ move_opt_across_gc_bif,
+ erl_202
]}].
init_per_suite(Config) ->
@@ -135,6 +137,27 @@ positive(speaking) ->
paris([], P) -> P + 1.
+
+%% See https://bugs.erlang.org/browse/ERL-202.
+%% Test that move_allocates/1 in beam_block doesn't move allocate
+%% when it would not be safe.
+
+-record(erl_202_r1, {y}).
+-record(erl_202_r2, {x}).
+
+erl_202(_Config) ->
+ Ref = make_ref(),
+ Ref = erl_202({{1,2},Ref}, 42),
+
+ {Ref} = erl_202({7,8}, #erl_202_r1{y=#erl_202_r2{x=Ref}}),
+
+ ok.
+
+erl_202({{_, _},X}, _) ->
+ X;
+erl_202({_, _}, #erl_202_r1{y=R2}) ->
+ {R2#erl_202_r2.x}.
+
%%%
%%% The only test of the following code is that it compiles.
%%%