From 1858cb81391d2bce29b4b7620574ca60128cebf7 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= Date: Fri, 12 Mar 2010 09:12:05 +0100 Subject: erl_expand_records: Replace is_record() with matching The compiler currently generates better code for: f(#r1{}) -> r1; f(#r2{}) -> r2; f(#r3{}) -> r3. than for: g(X) when is_record(X, r1) -> r1; g(X) when is_record(X, r2) -> r2; g(X) when is_record(X, r3) -> r3. The compiler generates good code for pattern matching (as in f/1), but in g/1 there are no patterns to match, and the clause to be executed must be chosen by evaluating the guards sequentially until one succeeds. Make the compiler generate better code by replacing calls to is_record() with matching in the function head (basically, g/1 will automatically be rewritten to do pattern matching as in f/1). Note that this rewrite will also benefit code such as: h(X) when X#r1.a =:= 1 -> ok. because it would have been rewritten to: h(X) when (is_record(X, r1, 3) orelse fail) and (element(2, X) =:= 1) -> ok. which in turn will be rewritten to: h({r1,_,_}=X) when (true orelse fail) and (element(2, X) =:= 1) -> ok. (That will be further simplified in later compiler passes.) --- lib/stdlib/src/erl_expand_records.erl | 132 +++++++++++++++++++++++++++++++++- 1 file changed, 130 insertions(+), 2 deletions(-) (limited to 'lib/stdlib') 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). -- cgit v1.2.3 From 7ac0808979534a94617c3391503c961d1ef72755 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= Date: Fri, 12 Mar 2010 09:39:23 +0100 Subject: Evaluate element/2 at compile-time using type information The erl_expand_records compiler pass translates the following code: h(X) when X#r1.a =:= 1 -> ok. to (essentially): h({r1,V1,V2}=X) when element(2, X) =:= 1 -> ok. Since the guard can only be executed when the pattern matching has succeeded, we know that the second element in the tuple X must have been bound to V2. Thus we can eliminate the call to element/2 like this: h({r1,V1,V2}=X) when V1 =:= 1 -> ok. --- lib/stdlib/test/qlc_SUITE.erl | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'lib/stdlib') diff --git a/lib/stdlib/test/qlc_SUITE.erl b/lib/stdlib/test/qlc_SUITE.erl index aa12ed57da..e21de8770a 100644 --- a/lib/stdlib/test/qlc_SUITE.erl +++ b/lib/stdlib/test/qlc_SUITE.erl @@ -3184,7 +3184,9 @@ lookup2(Config) when is_list(Config) -> [] = qlc:e(Q), false = lookup_keys(Q) end, [{1,b},{2,3}])">>, - {warnings,[{{3,48},qlc,nomatch_filter}]}}, + {warnings,[{2,sys_core_fold,nomatch_guard}, + {3,qlc,nomatch_filter}, + {3,sys_core_fold,{eval_failure,badarg}}]}}, <<"etsc(fun(E) -> Q = qlc:q([X || {X} <- ets:table(E), element(1,{X}) =:= 1]), -- cgit v1.2.3