diff options
Diffstat (limited to 'lib/compiler/src/sys_core_fold.erl')
| -rw-r--r-- | lib/compiler/src/sys_core_fold.erl | 114 |
1 files changed, 100 insertions, 14 deletions
diff --git a/lib/compiler/src/sys_core_fold.erl b/lib/compiler/src/sys_core_fold.erl index ceb7d56221..1681d97efb 100644 --- a/lib/compiler/src/sys_core_fold.erl +++ b/lib/compiler/src/sys_core_fold.erl @@ -115,13 +115,6 @@ module(#c_module{defs=Ds0}=Mod, Opts) -> {ok,Mod#c_module{defs=Ds1},get_warnings()}. function_1({#c_var{name={F,Arity}}=Name,B0}) -> - %% 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), try %% Find a suitable starting value for the variable %% counter. Note that this pass assumes that new_var_name/1 @@ -352,7 +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}; @@ -483,6 +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]. @@ -2557,12 +2635,20 @@ opt_build_stacktrace(#c_let{vars=[#c_var{name=Cooked}], #c_call{module=#c_literal{val=erlang}, name=#c_literal{val=raise}, args=[Class,Exp,#c_var{name=Cooked}]} -> - %% The stacktrace is only used in a call to 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]}; + 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 -> |