diff options
Diffstat (limited to 'lib/compiler/src/sys_core_fold.erl')
| -rw-r--r-- | lib/compiler/src/sys_core_fold.erl | 495 |
1 files changed, 364 insertions, 131 deletions
diff --git a/lib/compiler/src/sys_core_fold.erl b/lib/compiler/src/sys_core_fold.erl index d73060fb7e..1681d97efb 100644 --- a/lib/compiler/src/sys_core_fold.erl +++ b/lib/compiler/src/sys_core_fold.erl @@ -1,7 +1,7 @@ %% %% %CopyrightBegin% %% -%% Copyright Ericsson AB 1999-2017. All Rights Reserved. +%% Copyright Ericsson AB 1999-2018. All Rights Reserved. %% %% Licensed under the Apache License, Version 2.0 (the "License"); %% you may not use this file except in compliance with the License. @@ -108,25 +108,29 @@ module(#c_module{defs=Ds0}=Mod, Opts) -> put(no_inline_list_funcs, not member(inline_list_funcs, Opts)), - case get(new_var_num) of - undefined -> put(new_var_num, 0); - _ -> ok - end, init_warnings(), Ds1 = [function_1(D) || D <- Ds0], + erase(new_var_num), erase(no_inline_list_funcs), {ok,Mod#c_module{defs=Ds1},get_warnings()}. function_1({#c_var{name={F,Arity}}=Name,B0}) -> try + %% Find a suitable starting value for the variable + %% counter. Note that this pass assumes that new_var_name/1 + %% returns a variable name distinct from any variable used in + %% the entire body of the function. We use integers as + %% variable names to avoid filling up the atom table when + %% compiling huge functions. + Count = cerl_trees:next_free_variable_name(B0), + put(new_var_num, Count), B = find_fixpoint(fun(Core) -> %% This must be a fun! expr(Core, value, sub_new()) end, B0, 20), {Name,B} catch - Class:Error -> - Stack = erlang:get_stacktrace(), + Class:Error:Stack -> io:fwrite("Function: ~w/~w\n", [F,Arity]), erlang:raise(Class, Error, Stack) end. @@ -146,14 +150,9 @@ find_fixpoint(OptFun, Core0, Max) -> body(Body, Sub) -> body(Body, value, Sub). -body(#c_values{anno=A,es=Es0}, Ctxt, Sub) -> - Es1 = expr_list(Es0, Ctxt, Sub), - case Ctxt of - value -> - #c_values{anno=A,es=Es1}; - effect -> - make_effect_seq(Es1, Sub) - end; +body(#c_values{anno=A,es=Es0}, value, Sub) -> + Es1 = expr_list(Es0, value, Sub), + #c_values{anno=A,es=Es1}; body(E, Ctxt, Sub) -> ?ASSERT(verify_scope(E, Sub)), expr(E, Ctxt, Sub). @@ -208,6 +207,8 @@ opt_guard_try(#c_case{clauses=Cs}=Term) -> Term#c_case{clauses=opt_guard_try_list(Cs)}; opt_guard_try(#c_clause{body=B0}=Term) -> Term#c_clause{body=opt_guard_try(B0)}; +opt_guard_try(#c_let{vars=[],arg=#c_values{es=[]},body=B}) -> + B; opt_guard_try(#c_let{arg=Arg,body=B0}=Term) -> case opt_guard_try(B0) of #c_literal{}=B -> @@ -314,9 +315,15 @@ expr(#c_seq{arg=Arg0,body=B0}=Seq0, Ctxt, Sub) -> false -> %% Arg cannot be "values" here - only a single value %% make sense here. - case is_safe_simple(Arg, Sub) of - true -> B1; - false -> Seq0#c_seq{arg=Arg,body=B1} + case {Ctxt,is_safe_simple(Arg, Sub)} of + {effect,true} -> B1; + {effect,false} -> + case is_safe_simple(B1, Sub) of + true -> Arg; + false -> Seq0#c_seq{arg=Arg,body=B1} + end; + {value,true} -> B1; + {value,false} -> Seq0#c_seq{arg=Arg,body=B1} end end; expr(#c_let{}=Let0, Ctxt, Sub) -> @@ -338,7 +345,12 @@ expr(#c_letrec{body=#c_var{}}=Letrec, effect, _Sub) -> void(); expr(#c_letrec{defs=Fs0,body=B0}=Letrec, Ctxt, Sub) -> Fs1 = map(fun ({Name,Fb}) -> - {Name,expr(Fb, {letrec,Ctxt}, Sub)} + case Ctxt =:= effect andalso is_fun_effect_safe(Name, B0) of + true -> + {Name,expr(Fb, {letrec, effect}, Sub)}; + false -> + {Name,expr(Fb, {letrec, value}, Sub)} + end end, Fs0), B1 = body(B0, Ctxt, Sub), Letrec#c_letrec{defs=Fs1,body=B1}; @@ -380,10 +392,7 @@ expr(#c_case{}=Case0, Ctxt, Sub) -> Case = Case1#c_case{arg=Arg2,clauses=Cs2}, warn_no_clause_match(Case1, Case), Expr = eval_case(Case, Sub), - case move_case_into_arg(Case, Sub) of - impossible -> Expr; - Other -> Other - end; + move_case_into_arg(Expr, Sub); Other -> expr(Other, Ctxt, Sub) end; @@ -392,14 +401,15 @@ expr(#c_receive{clauses=Cs0,timeout=T0,action=A0}=Recv, Ctxt, Sub) -> T1 = expr(T0, value, Sub), A1 = body(A0, Ctxt, Sub), Recv#c_receive{clauses=Cs1,timeout=T1,action=A1}; -expr(#c_apply{anno=Anno,op=Op0,args=As0}=App, _, Sub) -> +expr(#c_apply{anno=Anno,op=Op0,args=As0}=Apply0, _, Sub) -> Op1 = expr(Op0, value, Sub), As1 = expr_list(As0, value, Sub), - case cerl:is_data(Op1) of + case cerl:is_data(Op1) andalso not is_literal_fun(Op1) of false -> - App#c_apply{op=Op1,args=As1}; + Apply = Apply0#c_apply{op=Op1,args=As1}, + fold_apply(Apply, Op1, As1); true -> - add_warning(App, invalid_call), + add_warning(Apply0, invalid_call), Err = #c_call{anno=Anno, module=#c_literal{val=erlang}, name=#c_literal{val=error}, @@ -415,9 +425,20 @@ expr(#c_call{module=M0,name=N0}=Call0, Ctxt, Sub) -> no -> call(Call, M1, N1, Sub); {yes,Seq} -> expr(Seq, Ctxt, Sub) end; +expr(#c_primop{name=#c_literal{val=build_stacktrace}}, effect, _Sub) -> + void(); expr(#c_primop{args=As0}=Prim, _, Sub) -> As1 = expr_list(As0, value, Sub), Prim#c_primop{args=As1}; +expr(#c_catch{anno=Anno,body=B}, effect, Sub) -> + %% When the return value of the 'catch' is ignored, we can replace it + %% with a try/catch to avoid building a stack trace when an exception + %% occurs. + Var = #c_var{name='catch_value'}, + Evs = [#c_var{name='Class'},#c_var{name='Reason'},#c_var{name='Stk'}], + Try = #c_try{anno=Anno,arg=B,vars=[Var],body=Var, + evars=Evs,handler=void()}, + expr(Try, effect, Sub); expr(#c_catch{body=B0}=Catch, _, Sub) -> %% We can remove catch if the value is simple B1 = body(B0, value, Sub), @@ -460,6 +481,86 @@ expr(#c_try{anno=A,arg=E0,vars=Vs0,body=B0,evars=Evs0,handler=H0}=Try, _, Sub0) Try#c_try{arg=E1,vars=Vs1,body=B1,evars=Evs1,handler=H1} end. + +%% If a fun or its application is used as an argument, then it's unsafe to +%% handle it in effect context as the side-effects may rely on its return +%% value. The following is a minimal example of where it can go wrong: +%% +%% do letrec 'f'/0 = fun () -> ... whatever ... +%% in call 'side':'effect'(apply 'f'/0()) +%% 'ok' +%% +%% This function returns 'true' if Body definitely does not rely on a +%% value produced by FVar, or 'false' if Body depends on or might depend on +%% a value produced by FVar. + +is_fun_effect_safe(#c_var{}=FVar, Body) -> + ifes_1(FVar, Body, true). + +ifes_1(FVar, #c_alias{pat=Pat}, _Safe) -> + ifes_1(FVar, Pat, false); +ifes_1(FVar, #c_apply{op=Op,args=Args}, Safe) -> + %% FVar(...) is safe as long its return value is ignored, but it's never + %% okay to pass FVar as an argument. + ifes_list(FVar, Args, false) andalso ifes_1(FVar, Op, Safe); +ifes_1(FVar, #c_binary{segments=Segments}, _Safe) -> + ifes_list(FVar, Segments, false); +ifes_1(FVar, #c_bitstr{val=Val,size=Size,unit=Unit}, _Safe) -> + ifes_list(FVar, [Val, Size, Unit], false); +ifes_1(FVar, #c_call{args=Args}, _Safe) -> + ifes_list(FVar, Args, false); +ifes_1(FVar, #c_case{arg=Arg,clauses=Clauses}, Safe) -> + ifes_1(FVar, Arg, false) andalso ifes_list(FVar, Clauses, Safe); +ifes_1(FVar, #c_catch{body=Body}, _Safe) -> + ifes_1(FVar, Body, false); +ifes_1(FVar, #c_clause{pats=Pats,guard=Guard,body=Body}, Safe) -> + ifes_list(FVar, Pats, false) andalso + ifes_1(FVar, Guard, false) andalso + ifes_1(FVar, Body, Safe); +ifes_1(FVar, #c_cons{hd=Hd,tl=Tl}, _Safe) -> + ifes_1(FVar, Hd, false) andalso ifes_1(FVar, Tl, false); +ifes_1(FVar, #c_fun{body=Body}, _Safe) -> + ifes_1(FVar, Body, false); +ifes_1(FVar, #c_let{arg=Arg,body=Body}, Safe) -> + ifes_1(FVar, Arg, false) andalso ifes_1(FVar, Body, Safe); +ifes_1(FVar, #c_letrec{defs=Defs,body=Body}, Safe) -> + Funs = [Fun || {_,Fun} <- Defs], + ifes_list(FVar, Funs, false) andalso ifes_1(FVar, Body, Safe); +ifes_1(_FVar, #c_literal{}, _Safe) -> + true; +ifes_1(FVar, #c_map{arg=Arg,es=Elements}, _Safe) -> + ifes_1(FVar, Arg, false) andalso ifes_list(FVar, Elements, false); +ifes_1(FVar, #c_map_pair{key=Key,val=Val}, _Safe) -> + ifes_1(FVar, Key, false) andalso ifes_1(FVar, Val, false); +ifes_1(FVar, #c_primop{args=Args}, _Safe) -> + ifes_list(FVar, Args, false); +ifes_1(FVar, #c_receive{timeout=Timeout,action=Action,clauses=Clauses}, Safe) -> + ifes_1(FVar, Timeout, false) andalso + ifes_1(FVar, Action, Safe) andalso + ifes_list(FVar, Clauses, Safe); +ifes_1(FVar, #c_seq{arg=Arg,body=Body}, Safe) -> + %% Arg of a #c_seq{} has no effect so it's okay to use FVar there even if + %% Safe=false. + ifes_1(FVar, Arg, true) andalso ifes_1(FVar, Body, Safe); +ifes_1(FVar, #c_try{arg=Arg,handler=Handler,body=Body}, Safe) -> + ifes_1(FVar, Arg, false) andalso + ifes_1(FVar, Handler, Safe) andalso + ifes_1(FVar, Body, Safe); +ifes_1(FVar, #c_tuple{es=Elements}, _Safe) -> + ifes_list(FVar, Elements, false); +ifes_1(FVar, #c_values{es=Elements}, _Safe) -> + ifes_list(FVar, Elements, false); +ifes_1(#c_var{name=Name}, #c_var{name=Name}, Safe) -> + %% It's safe to return FVar if it's unused. + Safe; +ifes_1(_FVar, #c_var{}, _Safe) -> + true. + +ifes_list(FVar, [E|Es], Safe) -> + ifes_1(FVar, E, Safe) andalso ifes_list(FVar, Es, Safe); +ifes_list(_FVar, [], _Safe) -> + true. + expr_list(Es, Ctxt, Sub) -> [expr(E, Ctxt, Sub) || E <- Es]. @@ -479,6 +580,9 @@ bitstr_list(Es, Sub) -> bitstr(#c_bitstr{val=Val,size=Size}=BinSeg, Sub) -> BinSeg#c_bitstr{val=expr(Val, Sub),size=expr(Size, value, Sub)}. +is_literal_fun(#c_literal{val=F}) -> is_function(F); +is_literal_fun(_) -> false. + %% is_safe_simple(Expr, Sub) -> true | false. %% A safe simple cannot fail with badarg and is safe to use %% in a guard. @@ -743,6 +847,25 @@ make_effect_seq([H|T], Sub) -> end; make_effect_seq([], _) -> void(). +%% fold_apply(Apply, LiteraFun, Args) -> Apply. +%% Replace an apply of a literal external fun with a call. + +fold_apply(Apply, #c_literal{val=Fun}, Args) when is_function(Fun) -> + {module,Mod} = erlang:fun_info(Fun, module), + {name,Name} = erlang:fun_info(Fun, name), + {arity,Arity} = erlang:fun_info(Fun, arity), + if + Arity =:= length(Args) -> + #c_call{anno=Apply#c_apply.anno, + module=#c_literal{val=Mod}, + name=#c_literal{val=Name}, + args=Args}; + true -> + Apply + end; +fold_apply(Apply, _, _) -> Apply. + + %% Handling remote calls. The module/name fields have been processed. call(#c_call{args=As}=Call, #c_literal{val=M}=M0, #c_literal{val=N}=N0, Sub) -> @@ -780,6 +903,8 @@ fold_call(Call, #c_literal{val=M}, #c_literal{val=F}, Args, Sub) -> fold_call_1(Call, M, F, Args, Sub); fold_call(Call, _M, _N, _Args, _Sub) -> Call. +fold_call_1(Call, erlang, apply, [Fun,Args], _) -> + simplify_fun_apply(Call, Fun, Args); fold_call_1(Call, erlang, apply, [Mod,Func,Args], _) -> simplify_apply(Call, Mod, Func, Args); fold_call_1(Call, Mod, Name, Args, Sub) -> @@ -1088,24 +1213,38 @@ eval_failure(Call, Reason) -> %% Simplify an apply/3 to a call if the number of arguments %% are known at compile time. -simplify_apply(Call, Mod, Func, Args) -> +simplify_apply(Call, Mod, Func, Args0) -> case is_atom_or_var(Mod) andalso is_atom_or_var(Func) of - true -> simplify_apply_1(Args, Call, Mod, Func, []); - false -> Call + true -> + case get_fixed_args(Args0, []) of + error -> + Call; + {ok,Args} -> + Call#c_call{module=Mod,name=Func,args=Args} + end; + false -> + Call end. - -simplify_apply_1(#c_literal{val=MoreArgs0}, Call, Mod, Func, Args) - when length(MoreArgs0) >= 0 -> - MoreArgs = [#c_literal{val=Arg} || Arg <- MoreArgs0], - Call#c_call{module=Mod,name=Func,args=reverse(Args, MoreArgs)}; -simplify_apply_1(#c_cons{hd=Arg,tl=T}, Call, Mod, Func, Args) -> - simplify_apply_1(T, Call, Mod, Func, [Arg|Args]); -simplify_apply_1(_, Call, _, _, _) -> Call. - is_atom_or_var(#c_literal{val=Atom}) when is_atom(Atom) -> true; is_atom_or_var(#c_var{}) -> true; is_atom_or_var(_) -> false. +simplify_fun_apply(#c_call{anno=Anno}=Call, Fun, Args0) -> + case get_fixed_args(Args0, []) of + error -> + Call; + {ok,Args} -> + #c_apply{anno=Anno,op=Fun,args=Args} + end. + +get_fixed_args(#c_literal{val=MoreArgs0}, Args) + when length(MoreArgs0) >= 0 -> + MoreArgs = [#c_literal{val=Arg} || Arg <- MoreArgs0], + {ok,reverse(Args, MoreArgs)}; +get_fixed_args(#c_cons{hd=Arg,tl=T}, Args) -> + get_fixed_args(T, [Arg|Args]); +get_fixed_args(_, _) -> error. + %% clause(Clause, Cepxr, Context, Sub) -> Clause. clause(#c_clause{pats=Ps0}=Cl, Cexpr, Ctxt, Sub0) -> @@ -1214,13 +1353,18 @@ let_subst_list([], [], _) -> {[],[],[]}. %%pattern(Pat, Sub) -> pattern(Pat, Sub, Sub). pattern(#c_var{}=Pat, Isub, Osub) -> - case sub_is_val(Pat, Isub) of + case sub_is_in_scope(Pat, Isub) of true -> + %% This variable either has a substitution or is used in + %% the variable list of an enclosing `let`. In either + %% case, it must be renamed to an unused name to avoid + %% name capture problems. V1 = make_var_name(), Pat1 = #c_var{name=V1}, {Pat1,sub_set_var(Pat, Pat1, sub_add_scope([V1], Osub))}; false -> - {Pat,sub_del_var(Pat, Osub)} + %% This variable has never been used. Add it to the scope. + {Pat,sub_add_scope([Pat#c_var.name], Osub)} end; pattern(#c_literal{}=Pat, _, Osub) -> {Pat,Osub}; pattern(#c_cons{anno=Anno,hd=H0,tl=T0}, Isub, Osub0) -> @@ -1399,8 +1543,8 @@ is_subst(_) -> false. %% sub_set_name(Name, Value, #sub{}) -> #sub{}. %% sub_del_var(Var, #sub{}) -> #sub{}. %% sub_subst_var(Var, Value, #sub{}) -> [{Name,Value}]. -%% sub_is_val(Var, #sub{}) -> boolean(). -%% sub_add_scope(#sub{}) -> #sub{} +%% sub_is_in_scope(Var, #sub{}) -> boolean(). +%% sub_add_scope([Var], #sub{}) -> #sub{} %% sub_subst_scope(#sub{}) -> #sub{} %% %% We use the variable name as key so as not have problems with @@ -1435,18 +1579,6 @@ sub_set_name(V, Val, #sub{v=S,s=Scope,t=Tdb0}=Sub) -> Tdb = copy_type(V, Val, Tdb1), Sub#sub{v=orddict:store(V, Val, S),s=cerl_sets:add_element(V, Scope),t=Tdb}. -sub_del_var(#c_var{name=V}, #sub{v=S,s=Scope,t=Tdb}=Sub) -> - %% Profiling shows that for programs with many record operations, - %% sub_del_var/2 is a bottleneck. Since the scope contains all - %% variables that are live, we know that V cannot be present in S - %% if it is not in the scope. - case cerl_sets:is_element(V, Scope) of - false -> - Sub#sub{s=cerl_sets:add_element(V, Scope)}; - true -> - Sub#sub{v=orddict:erase(V, S),t=kill_types(V, Tdb)} - end. - sub_subst_var(#c_var{name=V}, Val, #sub{v=S0}) -> %% Fold chained substitutions. [{V,Val}] ++ [ {K,Val} || {K,#c_var{name=V1}} <- S0, V1 =:= V]. @@ -1472,16 +1604,8 @@ sub_subst_scope_1([H|T], Key, Acc) -> sub_subst_scope_1(T, Key-1, [{Key,#c_var{name=H}}|Acc]); sub_subst_scope_1([], _, Acc) -> Acc. -sub_is_val(#c_var{name=V}, #sub{v=S,s=Scope}) -> - %% When the bottleneck in sub_del_var/2 was eliminated, this - %% became the new bottleneck. Since the scope contains all - %% live variables, a variable V can only be the target for - %% a substitution if it is in the scope. - cerl_sets:is_element(V, Scope) andalso v_is_value(V, S). - -v_is_value(Var, [{_,#c_var{name=Var}}|_]) -> true; -v_is_value(Var, [_|T]) -> v_is_value(Var, T); -v_is_value(_, []) -> false. +sub_is_in_scope(#c_var{name=V}, #sub{s=Scope}) -> + cerl_sets:is_element(V, Scope). %% warn_no_clause_match(CaseOrig, CaseOpt) -> ok %% Generate a warning if none of the user-specified clauses @@ -2146,7 +2270,7 @@ make_var(A) -> make_var_name() -> N = get(new_var_num), put(new_var_num, N+1), - list_to_atom("@f"++integer_to_list(N)). + N. letify(Bs, Body) -> Ann = cerl:get_ann(Body), @@ -2422,16 +2546,10 @@ move_let_into_expr(#c_let{vars=InnerVs0,body=InnerBody0}=Inner, Outer#c_let{vars=OuterVs,arg=Arg, body=Inner#c_let{vars=InnerVs,arg=OuterBody,body=InnerBody}}; move_let_into_expr(#c_let{vars=Lvs0,body=Lbody0}=Let, - #c_case{arg=Cexpr0,clauses=[Ca0,Cb0|Cs]}=Case, Sub0) -> - %% Test if there are no more clauses than Ca0 and Cb0, or if - %% Cb0 is guaranteed to match. - TwoClauses = Cs =:= [] orelse - case Cb0 of - #c_clause{pats=[#c_var{}],guard=#c_literal{val=true}} -> true; - _ -> false - end, - case {TwoClauses,is_failing_clause(Ca0),is_failing_clause(Cb0)} of - {true,false,true} -> + #c_case{arg=Cexpr0,clauses=[Ca0|Cs0]}=Case, Sub0) -> + case not is_failing_clause(Ca0) andalso + are_all_failing_clauses(Cs0) of + true -> %% let <Lvars> = case <Case-expr> of %% <Cpats> -> <Clause-body>; %% <OtherCpats> -> erlang:error(...) @@ -2467,8 +2585,8 @@ move_let_into_expr(#c_let{vars=Lvs0,body=Lbody0}=Let, body=Lbody}, Ca = Ca0#c_clause{pats=CaPats,guard=G,body=B}, - Cb = clause(Cb0, Cexpr, value, Sub0), - Case#c_case{arg=Cexpr,clauses=[Ca,Cb]} + Cs = [clause(C, Cexpr, value, Sub0) || C <- Cs0], + Case#c_case{arg=Cexpr,clauses=[Ca|Cs]} catch nomatch -> %% This is not a defeat. The code will eventually @@ -2476,7 +2594,7 @@ move_let_into_expr(#c_let{vars=Lvs0,body=Lbody0}=Let, %% optimizations done in this module. impossible end; - {_,_,_} -> impossible + false -> impossible end; move_let_into_expr(#c_let{vars=Lvs0,body=Lbody0}=Let, #c_seq{arg=Sarg0,body=Sbody0}=Seq, Sub0) -> @@ -2499,9 +2617,86 @@ move_let_into_expr(#c_let{vars=Lvs0,body=Lbody0}=Let, body=Lbody}}; move_let_into_expr(_Let, _Expr, _Sub) -> impossible. +are_all_failing_clauses(Cs) -> + all(fun is_failing_clause/1, Cs). + is_failing_clause(#c_clause{body=B}) -> will_fail(B). +%% opt_build_stacktrace(Let) -> Core. +%% If the stacktrace is *only* used in a call to erlang:raise/3, +%% there is no need to build a cooked stackframe using build_stacktrace/1. + +opt_build_stacktrace(#c_let{vars=[#c_var{name=Cooked}], + arg=#c_primop{name=#c_literal{val=build_stacktrace}, + args=[RawStk]}, + body=Body}=Let) -> + case Body of + #c_call{module=#c_literal{val=erlang}, + name=#c_literal{val=raise}, + args=[Class,Exp,#c_var{name=Cooked}]} -> + case core_lib:is_var_used(Cooked, #c_cons{hd=Class,tl=Exp}) of + true -> + %% Not safe. The stacktrace is used in the class or + %% reason. + Let; + false -> + %% The stacktrace is only used in the last + %% argument for erlang:raise/3. There is no need + %% to build the stacktrace. Replace the call to + %% erlang:raise/3 with the the raw_raise/3 + %% instruction, which will use a raw stacktrace. + #c_primop{name=#c_literal{val=raw_raise}, + args=[Class,Exp,RawStk]} + end; + #c_let{vars=[#c_var{name=V}],arg=Arg,body=B0} when V =/= Cooked -> + case core_lib:is_var_used(Cooked, Arg) of + false -> + %% The built stacktrace is not used in the argument, + %% so we can sink the building of the stacktrace into + %% the body of the let. + B = opt_build_stacktrace(Let#c_let{body=B0}), + Body#c_let{body=B}; + true -> + Let + end; + #c_seq{arg=Arg,body=B0} -> + case core_lib:is_var_used(Cooked, Arg) of + false -> + %% The built stacktrace is not used in the argument, + %% so we can sink the building of the stacktrace into + %% the body of the sequence. + B = opt_build_stacktrace(Let#c_let{body=B0}), + Body#c_seq{body=B}; + true -> + Let + end; + #c_case{arg=Arg,clauses=Cs0} -> + case core_lib:is_var_used(Cooked, Arg) orelse + is_used_in_any_guard(Cooked, Cs0) of + false -> + %% The built stacktrace is not used in the argument, + %% so we can sink the building of the stacktrace into + %% each arm of the case. + Cs = [begin + B = opt_build_stacktrace(Let#c_let{body=B0}), + C#c_clause{body=B} + end || #c_clause{body=B0}=C <- Cs0], + Body#c_case{clauses=Cs}; + true -> + Let + end; + _ -> + Let + end; +opt_build_stacktrace(Expr) -> + Expr. + +is_used_in_any_guard(V, Cs) -> + any(fun(#c_clause{guard=G}) -> + core_lib:is_var_used(V, G) + end, Cs). + %% opt_case_in_let(Let) -> Let' %% Try to avoid building tuples that are immediately matched. %% A common pattern is: @@ -2616,9 +2811,13 @@ delay_build_expr_1(#c_receive{clauses=Cs0, timeout=Timeout, action=A0}=Rec, TypeSig) -> Cs = delay_build_cs(Cs0, TypeSig), - A = case Timeout of - #c_literal{val=infinity} -> A0; - _ -> delay_build_expr(A0, TypeSig) + A = case {Timeout,A0} of + {#c_literal{val=infinity},#c_literal{}} -> + {_Type,Arity} = TypeSig, + Es = lists:duplicate(Arity, A0), + core_lib:make_values(Es); + _ -> + delay_build_expr(A0, TypeSig) end, Rec#c_receive{clauses=Cs,action=A}; delay_build_expr_1(#c_seq{body=B0}=Seq, TypeSig) -> @@ -2653,53 +2852,94 @@ opt_simple_let_1(#c_let{vars=Vs0,body=B0}=Let, Arg0, Ctxt, Sub0) -> %% Optimise let and add new substitutions. {Vs,Args,Sub1} = let_substs(Vs0, Arg0, Sub0), BodySub = update_let_types(Vs, Args, Sub1), + Sub = Sub1#sub{v=[],s=cerl_sets:new()}, B = body(B0, Ctxt, BodySub), Arg = core_lib:make_values(Args), - opt_simple_let_2(Let, Vs, Arg, B, B0, Ctxt, Sub1). + opt_simple_let_2(Let, Vs, Arg, B, B0, Sub). + -opt_simple_let_2(Let0, Vs0, Arg0, Body, PrevBody, Ctxt, Sub) -> +%% opt_simple_let_2(Let0, Vs0, Arg0, Body, PrevBody, Ctxt, Sub) -> Core. +%% Do final simplifications of the let. +%% +%% Note that the substitutions and scope in Sub have been cleared +%% and should not be used. + +opt_simple_let_2(Let0, Vs0, Arg0, Body, PrevBody, Sub) -> case {Vs0,Arg0,Body} of - {[#c_var{name=N1}],Arg1,#c_var{name=N2}} -> - case N1 =:= N2 of - true -> - %% let <Var> = Arg in <Var> ==> Arg - Arg1; - false -> - %% let <Var> = Arg in <OtherVar> ==> seq Arg OtherVar - Arg = maybe_suppress_warnings(Arg1, Vs0, PrevBody), - #c_seq{arg=Arg,body=Body} - end; + {[#c_var{name=V}],Arg1,#c_var{name=V}} -> + %% let <Var> = Arg in <Var> ==> Arg + Arg1; {[],#c_values{es=[]},_} -> %% No variables left. Body; - {Vs,Arg1,#c_literal{}} -> - Arg = maybe_suppress_warnings(Arg1, Vs, PrevBody), - case Ctxt of - effect -> - %% Throw away the literal body. - Arg; - value -> - %% Since the variable is not used in the body, we - %% can rewrite the let to a sequence. - %% let <Var> = Arg in Literal ==> seq Arg Literal - #c_seq{arg=Arg,body=Body} - end; - {Vs,Arg1,Body} -> - %% If none of the variables are used in the body, we can - %% rewrite the let to a sequence: - %% let <Var> = Arg in BodyWithoutVar ==> - %% seq Arg BodyWithoutVar - case is_any_var_used(Vs, Body) of - false -> - Arg = maybe_suppress_warnings(Arg1, Vs, PrevBody), - #c_seq{arg=Arg,body=Body}; - true -> - Let1 = Let0#c_let{vars=Vs,arg=Arg1,body=Body}, - opt_bool_case_in_let(Let1, Sub) + {[#c_var{name=V}=Var|Vars]=Vars0,Arg1,Body} -> + case core_lib:is_var_used(V, Body) of + false when Vars =:= [] -> + %% If the variable is not used in the body, we can + %% rewrite the let to a sequence: + %% let <Var> = Arg in BodyWithoutVar ==> + %% seq Arg BodyWithoutVar + Arg = maybe_suppress_warnings(Arg1, Var, PrevBody), + #c_seq{arg=Arg,body=Body}; + false -> + %% There are multiple values returned by the argument + %% and the first value is not used (this is a 'case' + %% with exported variables, but the return value is + %% ignored). We can remove the first variable and the + %% the first value returned from the 'let' argument. + Arg2 = remove_first_value(Arg1, Sub), + Let1 = Let0#c_let{vars=Vars,arg=Arg2,body=Body}, + post_opt_let(Let1, Sub); + true -> + Let1 = Let0#c_let{vars=Vars0,arg=Arg1,body=Body}, + post_opt_let(Let1, Sub) end end. -%% maybe_suppress_warnings(Arg, [#c_var{}], PreviousBody) -> Arg' +%% post_opt_let(Let, Sub) +%% Final optimizations of the let. +%% +%% Note that the substitutions and scope in Sub have been cleared +%% and should not be used. + +post_opt_let(Let0, Sub) -> + Let1 = opt_bool_case_in_let(Let0, Sub), + opt_build_stacktrace(Let1). + + +%% remove_first_value(Core0, Sub) -> Core. +%% Core0 is an expression that returns at least two values. +%% Remove the first value returned from Core0. + +remove_first_value(#c_values{es=[V|Vs]}, Sub) -> + Values = core_lib:make_values(Vs), + case is_safe_simple(V, Sub) of + false -> + #c_seq{arg=V,body=Values}; + true -> + Values + end; +remove_first_value(#c_case{clauses=Cs0}=Core, Sub) -> + Cs = remove_first_value_cs(Cs0, Sub), + Core#c_case{clauses=Cs}; +remove_first_value(#c_receive{clauses=Cs0,action=Act0}=Core, Sub) -> + Cs = remove_first_value_cs(Cs0, Sub), + Act = remove_first_value(Act0, Sub), + Core#c_receive{clauses=Cs,action=Act}; +remove_first_value(#c_let{body=B}=Core, Sub) -> + Core#c_let{body=remove_first_value(B, Sub)}; +remove_first_value(#c_seq{body=B}=Core, Sub) -> + Core#c_seq{body=remove_first_value(B, Sub)}; +remove_first_value(#c_primop{}=Core, _Sub) -> + Core; +remove_first_value(#c_call{}=Core, _Sub) -> + Core. + +remove_first_value_cs(Cs, Sub) -> + [C#c_clause{body=remove_first_value(B, Sub)} || + #c_clause{body=B}=C <- Cs]. + +%% maybe_suppress_warnings(Arg, #c_var{}, PreviousBody) -> Arg' %% Try to suppress false warnings when a variable is not used. %% For instance, we don't expect a warning for useless building in: %% @@ -2710,12 +2950,12 @@ opt_simple_let_2(Let0, Vs0, Arg0, Body, PrevBody, Ctxt, Sub) -> %% referenced in the original unoptimized code. If they were, we will %% consider the warning false and suppress it. -maybe_suppress_warnings(Arg, Vs, PrevBody) -> +maybe_suppress_warnings(Arg, #c_var{name=V}, PrevBody) -> case should_suppress_warning(Arg) of true -> Arg; %Already suppressed. false -> - case is_any_var_used(Vs, PrevBody) of + case core_lib:is_var_used(V, PrevBody) of true -> suppress_warning([Arg]); false -> @@ -2804,7 +3044,7 @@ move_case_into_arg(#c_case{arg=#c_case{arg=OuterArg, Outer#c_case{arg=OuterArg, clauses=[OuterCa,OuterCb]}; false -> - impossible + Inner0 end; move_case_into_arg(#c_case{arg=#c_seq{arg=OuterArg,body=InnerArg}=Outer, clauses=InnerClauses}=Inner, _Sub) -> @@ -2820,15 +3060,8 @@ move_case_into_arg(#c_case{arg=#c_seq{arg=OuterArg,body=InnerArg}=Outer, %% Outer#c_seq{arg=OuterArg, body=Inner#c_case{arg=InnerArg,clauses=InnerClauses}}; -move_case_into_arg(_, _) -> - impossible. - -is_any_var_used([#c_var{name=V}|Vs], Expr) -> - case core_lib:is_var_used(V, Expr) of - false -> is_any_var_used(Vs, Expr); - true -> true - end; -is_any_var_used([], _) -> false. +move_case_into_arg(Expr, _) -> + Expr. %%% %%% Retrieving information about types. |