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authorSverker Eriksson <[email protected]>2016-02-24 17:55:04 +0100
committerSverker Eriksson <[email protected]>2016-02-24 17:55:04 +0100
commit03743cd4193a2ca97f9b9a52a25e63f616e8fc07 (patch)
tree9c1f4094a2105ec4bf19dd0d16e76b598d0e608d /lib/compiler/src/beam_dead.erl
parent1b094d72ffc56069c72f17c7edd673dbbfe47e39 (diff)
parent35739bd06776f90526006486b3f4ab7e54f7f951 (diff)
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Merge branch 'master' into sverk/master/halt-INT_MIN
Diffstat (limited to 'lib/compiler/src/beam_dead.erl')
-rw-r--r--lib/compiler/src/beam_dead.erl57
1 files changed, 51 insertions, 6 deletions
diff --git a/lib/compiler/src/beam_dead.erl b/lib/compiler/src/beam_dead.erl
index ead88b57e9..11129c39bc 100644
--- a/lib/compiler/src/beam_dead.erl
+++ b/lib/compiler/src/beam_dead.erl
@@ -239,11 +239,26 @@ backward([{test,is_eq_exact,Fail,[Dst,{integer,Arity}]}=I|
backward([{label,Lbl}=L|Is], D, Acc) ->
backward(Is, beam_utils:index_label(Lbl, Acc, D), [L|Acc]);
backward([{select,select_val,Reg,{f,Fail0},List0}|Is], D, Acc) ->
- List = shortcut_select_list(List0, Reg, D, []),
+ List1 = shortcut_select_list(List0, Reg, D, []),
Fail1 = shortcut_label(Fail0, D),
Fail = shortcut_bs_test(Fail1, Is, D),
- Sel = {select,select_val,Reg,{f,Fail},List},
- backward(Is, D, [Sel|Acc]);
+ List = prune_redundant(List1, Fail),
+ case List of
+ [] ->
+ Jump = {jump,{f,Fail}},
+ backward([Jump|Is], D, Acc);
+ [V,F] ->
+ Test = {test,is_eq_exact,{f,Fail},[Reg,V]},
+ Jump = {jump,F},
+ backward([Jump,Test|Is], D, Acc);
+ [{atom,B1},F,{atom,B2},F] when B1 =:= not B2 ->
+ Test = {test,is_boolean,{f,Fail},[Reg]},
+ Jump = {jump,F},
+ backward([Jump,Test|Is], D, Acc);
+ [_|_] ->
+ Sel = {select,select_val,Reg,{f,Fail},List},
+ backward(Is, D, [Sel|Acc])
+ end;
backward([{jump,{f,To0}},{move,Src,Reg}=Move|Is], D, Acc) ->
To = shortcut_select_label(To0, Reg, Src, D),
Jump = {jump,{f,To}},
@@ -257,14 +272,17 @@ backward([{jump,{f,To}}=J|[{bif,Op,_,Ops,Reg}|Is]=Is0], D, Acc) ->
catch
throw:not_possible -> backward(Is0, D, [J|Acc])
end;
-backward([{test,bs_start_match2,F,_,[R,_],Ctxt}=I|Is], D,
+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) ->
+ {f,To0} = F,
+ To = shortcut_bs_start_match(To0, R, D),
case beam_utils:is_killed(Ctxt, Acc0, D) of
true ->
- Eq = {test,is_eq_exact,F,[R,{literal,Bs}]},
+ Eq = {test,is_eq_exact,{f,To},[R,{literal,Bs}]},
backward(Is, D, [Eq|Acc0]);
false ->
+ I = {test,bs_start_match2,{f,To},Live,Args,Ctxt},
backward(Is, D, [I|Acc])
end;
backward([{test,bs_start_match2,{f,To0},Live,[Src|_]=Info,Dst}|Is], D, Acc) ->
@@ -295,7 +313,28 @@ backward([{test,Op,{f,To0},Ops0}|Is], D, Acc) ->
is_eq_exact -> combine_eqs(To, Ops0, D, Acc);
_ -> {test,Op,{f,To},Ops0}
end,
- backward(Is, D, [I|Acc]);
+ case {I,Acc} of
+ {{test,is_atom,Fail,Ops0},[{test,is_boolean,Fail,Ops0}|_]} ->
+ %% An is_atom test before an is_boolean test (with the
+ %% same failure label) is redundant.
+ backward(Is, D, Acc);
+ {{test,is_atom,Fail,[R]},
+ [{test,is_eq_exact,Fail,[R,{atom,_}]}|_]} ->
+ %% An is_atom test before a comparison with an atom (with
+ %% the same failure label) is redundant.
+ backward(Is, D, Acc);
+ {{test,is_integer,Fail,[R]},
+ [{test,is_eq_exact,Fail,[R,{integer,_}]}|_]} ->
+ %% An is_integer test before a comparison with an integer
+ %% (with the same failure label) is redundant.
+ backward(Is, D, Acc);
+ {{test,_,_,_},_} ->
+ %% Still a test instruction. Done.
+ backward(Is, D, [I|Acc]);
+ {_,_} ->
+ %% Rewritten to a select_val. Rescan.
+ backward([I|Is], D, Acc)
+ end;
backward([{test,Op,{f,To0},Live,Ops0,Dst}|Is], D, Acc) ->
To1 = shortcut_bs_test(To0, Is, D),
To2 = shortcut_label(To1, D),
@@ -348,6 +387,12 @@ shortcut_label(To0, D) ->
shortcut_select_label(To, Reg, Lit, D) ->
shortcut_rel_op(To, is_ne_exact, [Reg,Lit], D).
+prune_redundant([_,{f,Fail}|T], Fail) ->
+ prune_redundant(T, Fail);
+prune_redundant([V,F|T], Fail) ->
+ [V,F|prune_redundant(T, Fail)];
+prune_redundant([], _) -> [].
+
%% Replace a comparison operator with a test instruction and a jump.
%% For example, if we have this code:
%%