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-rw-r--r--lib/stdlib/src/erl_expand_records.erl132
1 files changed, 130 insertions, 2 deletions
diff --git a/lib/stdlib/src/erl_expand_records.erl b/lib/stdlib/src/erl_expand_records.erl
index a38b7639d8..18c467db81 100644
--- a/lib/stdlib/src/erl_expand_records.erl
+++ b/lib/stdlib/src/erl_expand_records.erl
@@ -95,8 +95,9 @@ forms([F | Fs0], St0) ->
forms([], St) -> {[],St}.
clauses([{clause,Line,H0,G0,B0} | Cs0], St0) ->
- {H,St1} = head(H0, St0),
- {G,St2} = guard(G0, St1),
+ {H1,St1} = head(H0, St0),
+ {G1,St2} = guard(G0, St1),
+ {H,G} = optimize_is_record(H1, G1),
{B,St3} = exprs(B0, St2),
{Cs,St4} = clauses(Cs0, St3),
{[{clause,Line,H,G,B} | Cs],St4};
@@ -800,5 +801,132 @@ imported(F, A, St) ->
error -> no
end.
+%%%
+%%% Replace is_record/3 in guards with matching if possible.
+%%%
+
+optimize_is_record(H0, G0) ->
+ case opt_rec_vars(G0) of
+ [] ->
+ {H0,G0};
+ Rs0 ->
+ {H,Rs} = opt_pattern_list(H0, Rs0),
+ G = opt_remove(G0, Rs),
+ {H,G}
+ end.
+
+
+%% opt_rec_vars(Guards) -> Vars.
+%% Search through the guard expression, looking for
+%% variables referenced in those is_record/3 calls that
+%% will fail the entire guard if they evaluate to 'false'
+%%
+%% In the following code
+%%
+%% f(X, Y, Z) when is_record(X, r1) andalso
+%% (is_record(Y, r2) orelse is_record(Z, r3))
+%%
+%% the entire guard will be false if the record test for
+%% X fails, and the clause can be rewritten to:
+%%
+%% f({r1,...}=X, Y, Z) when true andalso
+%% (is_record(Y, r2) or is_record(Z, r3))
+%%
+opt_rec_vars([G|Gs]) ->
+ Rs = opt_rec_vars_1(G, orddict:new()),
+ opt_rec_vars(Gs, Rs);
+opt_rec_vars([]) -> orddict:new().
+
+opt_rec_vars([G|Gs], Rs0) ->
+ Rs1 = opt_rec_vars_1(G, orddict:new()),
+ Rs = ordsets:intersection(Rs0, Rs1),
+ opt_rec_vars(Gs, Rs);
+opt_rec_vars([], Rs) -> Rs.
+
+opt_rec_vars_1([T|Ts], Rs0) ->
+ Rs = opt_rec_vars_2(T, Rs0),
+ opt_rec_vars_1(Ts, Rs);
+opt_rec_vars_1([], Rs) -> Rs.
+
+opt_rec_vars_2({op,_,'and',A1,A2}, Rs) ->
+ opt_rec_vars_1([A1,A2], Rs);
+opt_rec_vars_2({op,_,'andalso',A1,A2}, Rs) ->
+ opt_rec_vars_1([A1,A2], Rs);
+opt_rec_vars_2({op,_,'orelse',Arg,{atom,_,fail}}, Rs) ->
+ %% Since the second argument guarantees failure,
+ %% it is safe to inspect the first argument.
+ opt_rec_vars_2(Arg, Rs);
+opt_rec_vars_2({call,_,{remote,_,{atom,_,erlang},{atom,_,is_record}},
+ [{var,_,V},{atom,_,Tag},{integer,_,Sz}]}, Rs) ->
+ orddict:store(V, {Tag,Sz}, Rs);
+opt_rec_vars_2({call,_,{atom,_,is_record},
+ [{var,_,V},{atom,_,Tag},{integer,_,Sz}]}, Rs) ->
+ orddict:store(V, {Tag,Sz}, Rs);
+opt_rec_vars_2(_, Rs) -> Rs.
+
+opt_pattern_list(Ps, Rs) ->
+ opt_pattern_list(Ps, Rs, []).
+
+opt_pattern_list([P0|Ps], Rs0, Acc) ->
+ {P,Rs} = opt_pattern(P0, Rs0),
+ opt_pattern_list(Ps, Rs, [P|Acc]);
+opt_pattern_list([], Rs, Acc) ->
+ {reverse(Acc),Rs}.
+
+opt_pattern({var,_,V}=Var, Rs0) ->
+ case orddict:find(V, Rs0) of
+ {ok,{Tag,Sz}} ->
+ Rs = orddict:store(V, {remove,Tag,Sz}, Rs0),
+ {opt_var(Var, Tag, Sz),Rs};
+ _ ->
+ {Var,Rs0}
+ end;
+opt_pattern({cons,Line,H0,T0}, Rs0) ->
+ {H,Rs1} = opt_pattern(H0, Rs0),
+ {T,Rs} = opt_pattern(T0, Rs1),
+ {{cons,Line,H,T},Rs};
+opt_pattern({tuple,Line,Es0}, Rs0) ->
+ {Es,Rs} = opt_pattern_list(Es0, Rs0),
+ {{tuple,Line,Es},Rs};
+opt_pattern({match,Line,Pa0,Pb0}, Rs0) ->
+ {Pa,Rs1} = opt_pattern(Pa0, Rs0),
+ {Pb,Rs} = opt_pattern(Pb0, Rs1),
+ {{match,Line,Pa,Pb},Rs};
+opt_pattern(P, Rs) -> {P,Rs}.
+
+opt_var({var,Line,_}=Var, Tag, Sz) ->
+ Rp = record_pattern(2, -1, ignore, Sz, Line, [{atom,Line,Tag}]),
+ {match,Line,{tuple,Line,Rp},Var}.
+
+opt_remove(Gs, Rs) ->
+ [opt_remove_1(G, Rs) || G <- Gs].
+
+opt_remove_1(Ts, Rs) ->
+ [opt_remove_2(T, Rs) || T <- Ts].
+
+opt_remove_2({op,L,'and'=Op,A1,A2}, Rs) ->
+ {op,L,Op,opt_remove_2(A1, Rs),opt_remove_2(A2, Rs)};
+opt_remove_2({op,L,'andalso'=Op,A1,A2}, Rs) ->
+ {op,L,Op,opt_remove_2(A1, Rs),opt_remove_2(A2, Rs)};
+opt_remove_2({op,L,'orelse',A1,A2}, Rs) ->
+ {op,L,'orelse',opt_remove_2(A1, Rs),A2};
+opt_remove_2({call,Line,{remote,_,{atom,_,erlang},{atom,_,is_record}},
+ [{var,_,V},{atom,_,Tag},{integer,_,Sz}]}=A, Rs) ->
+ case orddict:find(V, Rs) of
+ {ok,{remove,Tag,Sz}} ->
+ {atom,Line,true};
+ _ ->
+ A
+ end;
+opt_remove_2({call,Line,{atom,_,is_record},
+ [{var,_,V},{atom,_,Tag},{integer,_,Sz}]}=A, Rs) ->
+ case orddict:find(V, Rs) of
+ {ok,{remove,Tag,Sz}} ->
+ {atom,Line,true};
+ _ ->
+ A
+ end;
+opt_remove_2(A, _) -> A.
+
neg_line(L) ->
erl_parse:set_line(L, fun(Line) -> -abs(Line) end).