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-rw-r--r--lib/compiler/src/beam_dead.erl49
1 files changed, 33 insertions, 16 deletions
diff --git a/lib/compiler/src/beam_dead.erl b/lib/compiler/src/beam_dead.erl
index da944f3ce6..dbbaae05eb 100644
--- a/lib/compiler/src/beam_dead.erl
+++ b/lib/compiler/src/beam_dead.erl
@@ -294,24 +294,25 @@ backward([{jump,{f,To}}=J|[{gc_bif,_,{f,To},_,_,_Dst}|Is]], D, Acc) ->
%% register is initialized, and it is therefore no need to test
%% for liveness of the destination register at label To.
backward([J|Is], D, Acc);
-backward([{test,bs_start_match2,F,Live,[R,_]=Args,Ctxt}|Is], D,
- [{test,bs_match_string,F,[Ctxt,Bs]},
- {test,bs_test_tail2,F,[Ctxt,0]}|Acc0]=Acc) ->
+backward([{test,bs_start_match2,F,Live,[Src,_]=Args,Ctxt}|Is], D, Acc0) ->
{f,To0} = F,
- case beam_utils:is_killed(Ctxt, Acc0, D) of
- true ->
- To = shortcut_bs_context_to_binary(To0, R, D),
- Eq = {test,is_eq_exact,{f,To},[R,{literal,Bs}]},
- backward(Is, D, [Eq|Acc0]);
- false ->
- To = shortcut_bs_start_match(To0, R, D),
- I = {test,bs_start_match2,{f,To},Live,Args,Ctxt},
- backward(Is, D, [I|Acc])
+ case test_bs_literal(F, Ctxt, D, Acc0) of
+ {none,Acc} ->
+ %% Ctxt killed immediately after bs_start_match2.
+ To = shortcut_bs_context_to_binary(To0, Src, D),
+ I = {test,is_bitstr,{f,To},[Src]},
+ backward(Is, D, [I|Acc]);
+ {Literal,Acc} ->
+ %% Ctxt killed after matching a literal.
+ To = shortcut_bs_context_to_binary(To0, Src, D),
+ Eq = {test,is_eq_exact,{f,To},[Src,{literal,Literal}]},
+ backward(Is, D, [Eq|Acc]);
+ not_killed ->
+ %% Ctxt not killed. Not much to do.
+ To = shortcut_bs_start_match(To0, Src, D),
+ I = {test,bs_start_match2,{f,To},Live,Args,Ctxt},
+ backward(Is, D, [I|Acc0])
end;
-backward([{test,bs_start_match2,{f,To0},Live,[Src|_]=Info,Dst}|Is], D, Acc) ->
- To = shortcut_bs_start_match(To0, Src, D),
- I = {test,bs_start_match2,{f,To},Live,Info,Dst},
- backward(Is, D, [I|Acc]);
backward([{test,Op,{f,To0},Ops0}|Is], D, Acc) ->
To1 = shortcut_bs_test(To0, Is, D),
To2 = shortcut_label(To1, D),
@@ -511,6 +512,22 @@ remove_from_list(Lit, [Val,{f,_}=Fail|T]) ->
[Val,Fail|remove_from_list(Lit, T)];
remove_from_list(_, []) -> [].
+
+test_bs_literal(F, Ctxt, D,
+ [{test,bs_match_string,F,[Ctxt,Bs]},
+ {test,bs_test_tail2,F,[Ctxt,0]}|Acc]) ->
+ test_bs_literal_1(Ctxt, Acc, D, Bs);
+test_bs_literal(F, Ctxt, D, [{test,bs_test_tail2,F,[Ctxt,0]}|Acc]) ->
+ test_bs_literal_1(Ctxt, Acc, D, <<>>);
+test_bs_literal(_, Ctxt, D, Acc) ->
+ test_bs_literal_1(Ctxt, Acc, D, none).
+
+test_bs_literal_1(Ctxt, Is, D, Literal) ->
+ case beam_utils:is_killed(Ctxt, Is, D) of
+ true -> {Literal,Is};
+ false -> not_killed
+ end.
+
%% shortcut_bs_test(TargetLabel, ReversedInstructions, D) -> TargetLabel'
%% Try to shortcut the failure label for bit syntax matching.