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authorBjörn Gustavsson <[email protected]>2016-09-13 08:43:44 +0200
committerBjörn Gustavsson <[email protected]>2016-09-26 16:20:40 +0200
commit7169258d1315b86622093e1f14faf2267c9c448e (patch)
treec9a4053abf8bd9c0d744c3229f95220ba83a3479
parentac3bbbe932f2e547d93ebdc7c3bf4c0e542f30bd (diff)
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sys_core_fold: Improve case optimization
The optimization that avoids building a tuple in a case expression would not work if any clause matched a tuple as in the following example: f(A, B) -> case {A,B} of {<<X>>,Y} -> {X,Y} end. The generated Core Erlang code would look like this (note the tuples in the case expression and the pattern): 'f'/2 = fun (_cor1,_cor0) -> case {_cor1,_cor0} of <{#{#<X>(8,1,'integer',['unsigned'|['big']])}#,Y}> when 'true' -> {X,Y} . . . end It is expected that the code should look like this (note that tuples have been replaced with "values"): 'f'/2 = fun (_cor1,_cor0) -> %% Line 5 case <_cor1,_cor0> of <#{#<X>(8,1,'integer',['unsigned'|['big']])}#,Y> -> {X,Y} . . . end While at it, also fix bugs in the handling of pattern with aliases. The bindings were produced in the wrong order (creating 'let's with referring to free variables), but in most cases the incorrect bindings were discarded later without causing any harm.
-rw-r--r--lib/compiler/src/sys_core_fold.erl61
1 files changed, 32 insertions, 29 deletions
diff --git a/lib/compiler/src/sys_core_fold.erl b/lib/compiler/src/sys_core_fold.erl
index 79a45b1c7c..b8df4e04f8 100644
--- a/lib/compiler/src/sys_core_fold.erl
+++ b/lib/compiler/src/sys_core_fold.erl
@@ -2018,10 +2018,10 @@ case_opt_lit_1(_, []) -> [].
%% the clauses where it is actually needed.
case_opt_data(E, Cs0) ->
- Es = cerl:data_es(E),
TypeSig = {cerl:data_type(E),cerl:data_arity(E)},
- try case_opt_data_1(Cs0, Es, TypeSig) of
+ try case_opt_data_1(Cs0, TypeSig) of
Cs ->
+ Es = cerl:data_es(E),
{ok,Es,Cs}
catch
throw:impossible ->
@@ -2029,44 +2029,47 @@ case_opt_data(E, Cs0) ->
{error,Cs0}
end.
-case_opt_data_1([{[P0|Ps0],C,PsAcc,Bs0}|Cs], Es, TypeSig) ->
+case_opt_data_1([{[P0|Ps0],C,PsAcc,Bs0}|Cs], TypeSig) ->
P = case_opt_compiler_generated(P0),
- BindTo = #c_var{name=dummy},
- {Ps1,[{BindTo,_}|Bs1]} = case_data_pat_alias(P, BindTo, TypeSig, []),
- [{Ps1++Ps0,C,PsAcc,Bs1++Bs0}|case_opt_data_1(Cs, Es, TypeSig)];
-case_opt_data_1([], _, _) -> [].
+ {Ps1,Bs} = case_opt_data_2(P, TypeSig, Bs0),
+ [{Ps1++Ps0,C,PsAcc,Bs}|case_opt_data_1(Cs, TypeSig)];
+case_opt_data_1([], _) -> [].
-case_data_pat_alias(P, BindTo0, TypeSig, Bs0) ->
- case cerl:type(P) of
- alias ->
- %% Recursively handle the pattern and bind to
- %% the alias variable.
- BindTo = cerl:alias_var(P),
- Apat0 = cerl:alias_pat(P),
- Ann = [compiler_generated],
- Apat = cerl:set_ann(Apat0, Ann),
- {Ps,Bs} = case_data_pat_alias(Apat, BindTo, TypeSig, Bs0),
- {Ps,[{BindTo0,BindTo}|Bs]};
- var ->
- %% Here we will need to actually build the data and bind
- %% it to the variable.
+case_opt_data_2(P, TypeSig, Bs0) ->
+ case case_analyze_pat(P) of
+ {[],Pat} when Pat =/= none ->
+ DataEs = cerl:data_es(P),
+ {DataEs,Bs0};
+ {[V|Vs],none} ->
{Type,Arity} = TypeSig,
Ann = [compiler_generated],
Vars = make_vars(Ann, Arity),
Data = cerl:ann_make_data(Ann, Type, Vars),
- Bs = [{BindTo0,P},{P,Data}|Bs0],
+ Bs = [{V,Data} | [{Var,V} || Var <- Vs] ++ Bs0],
{Vars,Bs};
- _ ->
- %% Since case_opt_nomatch/3 has removed all clauses that
- %% cannot match, we KNOW that this clause must match and
- %% that the pattern must be a data constructor.
- %% Here we must build the data and bind it to the variable.
+ {[V|Vs],Pat} when Pat =/= none ->
{Type,_} = TypeSig,
- DataEs = cerl:data_es(P),
+ DataEs = cerl:data_es(Pat),
Vars = pat_to_expr_list(DataEs),
Ann = [compiler_generated],
Data = cerl:ann_make_data(Ann, Type, Vars),
- {DataEs,[{BindTo0,Data}]}
+ Bs = [{V,Data} | [{Var,V} || Var <- Vs] ++ Bs0],
+ {DataEs,Bs}
+ end.
+
+case_analyze_pat(P) ->
+ case_analyze_pat_1(P, [], none).
+
+case_analyze_pat_1(P, Vs, Pat) ->
+ case cerl:type(P) of
+ alias ->
+ V = cerl:alias_var(P),
+ Apat = cerl:alias_pat(P),
+ case_analyze_pat_1(Apat, [V|Vs], Pat);
+ var ->
+ {[P|Vs],Pat};
+ _ ->
+ {Vs,P}
end.
%% pat_to_expr(Pattern) -> Expression.