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authorBjörn Gustavsson <[email protected]>2015-02-06 13:22:20 +0100
committerBjörn Gustavsson <[email protected]>2015-03-09 10:10:27 +0100
commit9e15be5f241730b127d89dca01c6ad5f1e7508d7 (patch)
treefd02b9b724b079e6d8a3817a959f7292ac478eeb
parente2ced63dfaf14f38d2a334d51b3ca45030d55e0c (diff)
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v3_core: Teach pat_alias/2 to eliminate duplicated variables
Duplicated variables as aliases in patterns, such as: f({_,_}=Dup=Dup) -> ... will work, but produce sub-optimal code similar to: f({_,_}=Dup=NewVar) when Dup =:= NewVar -> ... with one extra guard test for each duplicated variable. Rewrite pat_alias/2 to eliminate all duplicated variables. While we are at it, also simplify handling of tuples, conses, and literals by using the data functions in the cerl module.
-rw-r--r--lib/compiler/src/v3_core.erl87
-rw-r--r--lib/compiler/test/match_SUITE.erl13
2 files changed, 60 insertions, 40 deletions
diff --git a/lib/compiler/src/v3_core.erl b/lib/compiler/src/v3_core.erl
index 3c19a209c0..c954d21e59 100644
--- a/lib/compiler/src/v3_core.erl
+++ b/lib/compiler/src/v3_core.erl
@@ -78,7 +78,7 @@
splitwith/2,keyfind/3,sort/1,foreach/2,droplast/1,last/1]).
-import(ordsets, [add_element/2,del_element/2,is_element/2,
union/1,union/2,intersection/2,subtract/2]).
--import(cerl, [ann_c_cons/3,ann_c_cons_skel/3,ann_c_tuple/2,c_tuple/1,
+-import(cerl, [ann_c_cons/3,ann_c_tuple/2,c_tuple/1,
ann_c_map/3]).
-include("core_parse.hrl").
@@ -1660,48 +1660,55 @@ pat_segment({bin_element,_,Val,Size,[Type,{unit,Unit}|Flags]}, St) ->
%% pat_alias(CorePat, CorePat) -> AliasPat.
%% Normalise aliases. Trap bad aliases by throwing 'nomatch'.
-pat_alias(#c_var{name=V1}, P2) -> #c_alias{var=#c_var{name=V1},pat=P2};
-pat_alias(P1, #c_var{name=V2}) -> #c_alias{var=#c_var{name=V2},pat=P1};
-
-%% alias cons
-pat_alias(#c_cons{}=Cons, #c_literal{anno=A,val=[H|T]}=S) ->
- pat_alias(Cons, ann_c_cons_skel(A, #c_literal{anno=A,val=H},
- S#c_literal{val=T}));
-pat_alias(#c_literal{anno=A,val=[H|T]}=S, #c_cons{}=Cons) ->
- pat_alias(ann_c_cons_skel(A, #c_literal{anno=A,val=H},
- S#c_literal{val=T}), Cons);
-pat_alias(#c_cons{anno=Anno,hd=H1,tl=T1}, #c_cons{hd=H2,tl=T2}) ->
- ann_c_cons(Anno, pat_alias(H1, H2), pat_alias(T1, T2));
-
-%% alias tuples
-pat_alias(#c_tuple{anno=Anno,es=Es1}, #c_literal{val=T}) when is_tuple(T) ->
- Es2 = [#c_literal{val=E} || E <- tuple_to_list(T)],
- ann_c_tuple(Anno, pat_alias_list(Es1, Es2));
-pat_alias(#c_literal{anno=Anno,val=T}, #c_tuple{es=Es2}) when is_tuple(T) ->
- Es1 = [#c_literal{val=E} || E <- tuple_to_list(T)],
- ann_c_tuple(Anno, pat_alias_list(Es1, Es2));
-pat_alias(#c_tuple{anno=Anno,es=Es1}, #c_tuple{es=Es2}) ->
- ann_c_tuple(Anno, pat_alias_list(Es1, Es2));
-
-%% alias maps
-%% There are no literals in maps patterns (patterns are always abstract)
-pat_alias(#c_map{es=Es1}=M,#c_map{es=Es2}) ->
- M#c_map{es=pat_alias_map_pairs(Es1++Es2)};
-
-pat_alias(#c_alias{var=V1,pat=P1},
- #c_alias{var=V2,pat=P2}) ->
- if V1 =:= V2 -> #c_alias{var=V1,pat=pat_alias(P1, P2)};
- true -> #c_alias{var=V1,pat=#c_alias{var=V2,pat=pat_alias(P1, P2)}}
+pat_alias(#c_var{name=V1}=P, #c_var{name=V1}) -> P;
+pat_alias(#c_var{name=V1}=Var,
+ #c_alias{var=#c_var{name=V2},pat=Pat}=Alias) ->
+ if
+ V1 =:= V2 ->
+ Alias;
+ true ->
+ Alias#c_alias{pat=pat_alias(Var, Pat)}
+ end;
+pat_alias(#c_var{}=P1, P2) -> #c_alias{var=P1,pat=P2};
+
+pat_alias(#c_alias{var=#c_var{name=V1}}=Alias, #c_var{name=V1}) ->
+ Alias;
+pat_alias(#c_alias{var=#c_var{name=V1}=Var1,pat=P1},
+ #c_alias{var=#c_var{name=V2}=Var2,pat=P2}) ->
+ Pat = pat_alias(P1, P2),
+ if
+ V1 =:= V2 ->
+ #c_alias{var=Var1,pat=Pat};
+ true ->
+ pat_alias(Var1, pat_alias(Var2, Pat))
end;
-pat_alias(#c_alias{var=V1,pat=P1}, P2) ->
- #c_alias{var=V1,pat=pat_alias(P1, P2)};
-pat_alias(P1, #c_alias{var=V2,pat=P2}) ->
- #c_alias{var=V2,pat=pat_alias(P1, P2)};
+pat_alias(#c_alias{var=#c_var{}=Var,pat=P1}, P2) ->
+ #c_alias{var=Var,pat=pat_alias(P1, P2)};
+
+pat_alias(#c_map{es=Es1}=M, #c_map{es=Es2}) ->
+ M#c_map{es=pat_alias_map_pairs(Es1 ++ Es2)};
+
+pat_alias(P1, #c_var{}=Var) ->
+ #c_alias{var=Var,pat=P1};
+pat_alias(P1, #c_alias{pat=P2}=Alias) ->
+ Alias#c_alias{pat=pat_alias(P1, P2)};
+
pat_alias(P1, P2) ->
- case {set_anno(P1, []),set_anno(P2, [])} of
- {P,P} -> P;
+ %% Aliases between binaries are not allowed, so the only
+ %% legal patterns that remain are data patterns.
+ case cerl:is_data(P1) andalso cerl:is_data(P2) of
+ false -> throw(nomatch);
+ true -> ok
+ end,
+ Type = cerl:data_type(P1),
+ case cerl:data_type(P2) of
+ Type -> ok;
_ -> throw(nomatch)
- end.
+ end,
+ Es1 = cerl:data_es(P1),
+ Es2 = cerl:data_es(P2),
+ Es = pat_alias_list(Es1, Es2),
+ cerl:make_data(Type, Es).
%% pat_alias_list([A1], [A2]) -> [A].
diff --git a/lib/compiler/test/match_SUITE.erl b/lib/compiler/test/match_SUITE.erl
index 7522ee985f..9aec0b3d4e 100644
--- a/lib/compiler/test/match_SUITE.erl
+++ b/lib/compiler/test/match_SUITE.erl
@@ -141,6 +141,13 @@ aliases(Config) when is_list(Config) ->
?line {a,b} = list_alias2([a,b]),
?line {a,b} = list_alias3([a,b]),
+ %% Non-matching aliases.
+ none = mixed_aliases(<<42>>),
+ none = mixed_aliases([b]),
+ none = mixed_aliases([d]),
+ none = mixed_aliases({a,42}),
+ none = mixed_aliases(42),
+
ok.
str_alias(V) ->
@@ -244,6 +251,12 @@ list_alias2([X,Y]=[a,b]) ->
list_alias3([X,b]=[a,Y]) ->
{X,Y}.
+mixed_aliases(<<X:8>> = x) -> {a,X};
+mixed_aliases([b] = <<X:8>>) -> {b,X};
+mixed_aliases(<<X:8>> = {a,X}) -> {c,X};
+mixed_aliases([X] = <<X:8>>) -> {d,X};
+mixed_aliases(_) -> none.
+
%% OTP-7018.
match_in_call(Config) when is_list(Config) ->