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3401-Inline-funs-that-are-immediately-used.patch
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File 3401-Inline-funs-that-are-immediately-used.patch of Package erlang
From 72675baaa9fd30e9823da20e07452acd91a6b196 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org> Date: Thu, 7 May 2020 14:48:18 +0200 Subject: [PATCH] Inline funs that are immediately used Funs can be used to hide local variables. Example: a() -> A = fun() -> A = 21, 2 * A end(), foo:bar(A). To avoid the slight runtime cost for such use of funs, teach the compiler to inline funs that are used only once immediately after creation. Resolves #4019. --- lib/compiler/src/sys_core_fold.erl | 39 ++++++++++++++++++- lib/compiler/test/fun_SUITE.erl | 7 +++- .../test/int_eval_SUITE_data/stacktrace.erl | 4 +- lib/stdlib/test/qlc_SUITE.erl | 11 ++++-- 4 files changed, 52 insertions(+), 9 deletions(-) diff --git a/lib/compiler/src/sys_core_fold.erl b/lib/compiler/src/sys_core_fold.erl index f5e26cdd08..49a3d57959 100644 --- a/lib/compiler/src/sys_core_fold.erl +++ b/lib/compiler/src/sys_core_fold.erl @@ -274,7 +274,7 @@ expr(#c_let{}=Let0, Ctxt, Sub) -> %% The argument for the let is "simple", i.e. has no %% complex structures such as let or seq that can be entered. ?ASSERT(verify_scope(Let, Sub)), - opt_simple_let(Let, Ctxt, Sub); + opt_fun_call(opt_simple_let(Let, Ctxt, Sub)); Expr -> %% The let body was successfully moved into the let argument. %% Now recursively re-process the new expression. @@ -2172,6 +2172,43 @@ is_safe_bool_expr_list([C|Cs], BoolVars) -> end; is_safe_bool_expr_list([], _, _) -> true. +opt_fun_call(#c_let{vars=[#c_var{name=V}],arg=#c_fun{}=FunDef,body=Body}=Let) -> + try do_opt_fun_call(V, FunDef, Body) of + impossible -> Let; + Expr -> Expr + catch + throw:impossible -> + Let + end; +opt_fun_call(Expr) -> Expr. + +do_opt_fun_call(V, FunDef, #c_apply{op=#c_var{name=V},args=CallArgs}) -> + Values = core_lib:make_values(CallArgs), + simplify_fun_call(V, Values, FunDef, CallArgs); +do_opt_fun_call(V, FunDef, #c_let{arg=#c_apply{op=#c_var{name=V},args=CallArgs}, + body=Rest}=Let) -> + Values = core_lib:make_values([Rest|CallArgs]), + Inlined = simplify_fun_call(V, Values, FunDef, CallArgs), + Let#c_let{arg=Inlined}; +do_opt_fun_call(V, FunDef, #c_seq{arg=#c_apply{op=#c_var{name=V},args=CallArgs}, + body=Rest}=Seq) -> + Values = core_lib:make_values([Rest|CallArgs]), + Inlined = simplify_fun_call(V, Values, FunDef, CallArgs), + Seq#c_seq{arg=Inlined}; +do_opt_fun_call(_, _, _) -> impossible. + +simplify_fun_call(V, Values, #c_fun{vars=Vars,body=FunBody}, CallArgs) -> + case not core_lib:is_var_used(V, Values) andalso length(Vars) =:= length(CallArgs) of + true -> + %% Safe to inline. + #c_let{vars=Vars, + arg=core_lib:make_values(CallArgs), + body=FunBody}; + false -> + %% The fun is used more than once or there is an arity mismatch. + throw(impossible) + end. + %% simplify_let(Let, Sub) -> Expr | impossible %% If the argument part of an let contains a complex expression, such %% as a let or a sequence, move the original let body into the complex diff --git a/lib/compiler/test/fun_SUITE.erl b/lib/compiler/test/fun_SUITE.erl index 2b8d60a885..387ed90ee6 100644 --- a/lib/compiler/test/fun_SUITE.erl +++ b/lib/compiler/test/fun_SUITE.erl @@ -56,12 +56,14 @@ end_per_group(_GroupName, Config) -> %%% The help functions below are copied from emulator:bs_construct_SUITE. --define(T(B, L), {B, ??B, L}). +-define(T(B, L), {fun() -> B end(), ??B, L}). l1() -> [ ?T((begin A = 3, F = fun(A) -> 1; (_) -> 2 end, F(2) end), 1), - ?T((begin G = fun(1=0) -> ok end, {'EXIT',_} = (catch G(2)), ok end), ok) + ?T((begin G = fun(1=0) -> ok end, {'EXIT',_} = (catch G(2)), ok end), ok), + ?T((begin F = fun(_, 1) -> 1; (F, N) -> N * F(F, N-1) end, F(F, 5) end), 120), + ?T((begin F = fun(_, 1) -> 1; (F, N) -> N * F(F, N-1) end, F(F, 1), ok end), ok) ]. test1(Config) when is_list(Config) -> @@ -241,6 +243,7 @@ dup2() -> badarity(Config) when is_list(Config) -> {'EXIT',{{badarity,{_,[]}},_}} = (catch (fun badarity/1)()), + {'EXIT',{{badarity,_},_}} = (catch fun() -> 42 end(0)), ok. badfun(_Config) -> diff --git a/lib/debugger/test/int_eval_SUITE_data/stacktrace.erl b/lib/debugger/test/int_eval_SUITE_data/stacktrace.erl index 591841ada3..61230eb598 100644 --- a/lib/debugger/test/int_eval_SUITE_data/stacktrace.erl +++ b/lib/debugger/test/int_eval_SUITE_data/stacktrace.erl @@ -106,10 +106,10 @@ do_fun(Bool) -> F(Bool). %Tail-recursive do_fun2(Bool) -> - F = fun(true) -> + F = fun(true, _) -> cons(Bool) %Tail-recursive end, - F(Bool), %Not tail-recursive + F(Bool, F), %Not tail-recursive. (The fun is not inlined) ?LINE. cons(Bool) -> diff --git a/lib/stdlib/test/qlc_SUITE.erl b/lib/stdlib/test/qlc_SUITE.erl index 8cb4067b1d..067e398840 100644 --- a/lib/stdlib/test/qlc_SUITE.erl +++ b/lib/stdlib/test/qlc_SUITE.erl @@ -2382,10 +2382,12 @@ filter(Config) when is_list(Config) -> false = lookup_keys(QH) end, [{1,1},{2,2},{3,3}])">>, - <<"fun(Z) -> + {cres, + <<"fun(Z) -> Q = qlc:q([X || Z < 2, X <- [1,2,3]]), [] = qlc:e(Q) - end(3)">>, + end(3)">>, [], {warnings,[{{2,31},sys_core_fold,no_clause_match}, + {{2,31},sys_core_fold,nomatch_guard}]}}, <<"H = qlc:q([{P1,A,P2,B,P3,C} || P1={A,_} <- [{1,a},{2,b}], @@ -3095,13 +3097,14 @@ lookup2(Config) when is_list(Config) -> %% {warnings,[{{4,35},qlc,nomatch_filter}]}}, []}, - <<"F = fun(U) -> + {cres, + <<"F = fun(U) -> Q = qlc:q([X || {X} <- [a,b,c], X =:= if U -> true; true -> false end]), [] = qlc:eval(Q), false = lookup_keys(Q) end, - F(apa)">>, + F(apa)">>, [], {warnings,[{{3,43},sys_core_fold,nomatch_guard}]}}, {cres, <<"etsc(fun(E) -> -- 2.26.2
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