%%
%% %CopyrightBegin%
%%
%% 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.
%% You may obtain a copy of the License at
%%
%% http://www.apache.org/licenses/LICENSE-2.0
%%
%% Unless required by applicable law or agreed to in writing, software
%% distributed under the License is distributed on an "AS IS" BASIS,
%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
%% See the License for the specific language governing permissions and
%% limitations under the License.
%%
%% %CopyrightEnd%
%%
%% Purpose : Constant folding optimisation for Core
%% Propagate atomic values and fold in values of safe calls to
%% constant arguments. Also detect and remove literals which are
%% ignored in a 'seq'. Could handle lets better by chasing down
%% complex 'arg' expressions and finding values.
%%
%% Try to optimise case expressions by removing unmatchable or
%% unreachable clauses. Also change explicit tuple arg into multiple
%% values and extend clause patterns. We must be careful here not to
%% generate cases which we know to be safe but later stages will not
%% recognise as such, e.g. the following is NOT acceptable:
%%
%% case 'b' of
%% <'b'> -> ...
%% end
%%
%% Variable folding is complicated by variable shadowing, for example
%% in:
%% 'foo'/1 =
%% fun (X) ->
%% let <A> = X
%% in let <X> = Y
%% in ... <use A>
%% If we were to simply substitute X for A then we would be using the
%% wrong X. Our solution is to rename variables that are the values
%% of substitutions. We could rename all shadowing variables but do
%% the minimum. We would then get:
%% 'foo'/1 =
%% fun (X) ->
%% let <A> = X
%% in let <X1> = Y
%% in ... <use A>
%% which is optimised to:
%% 'foo'/1 =
%% fun (X) ->
%% let <X1> = Y
%% in ... <use X>
%%
%% This is done by carefully shadowing variables and substituting
%% values. See details when defining functions.
%%
%% It would be possible to extend to replace repeated evaluation of
%% "simple" expressions by the value (variable) of the first call.
%% For example, after a "let Z = X+1" then X+1 would be replaced by Z
%% where X is valid. The Sub uses the full Core expression as key.
%% It would complicate handling of patterns as we would have to remove
%% all values where the key contains pattern variables.
-module(sys_core_fold).
-export([module/2,format_error/1]).
-import(lists, [map/2,foldl/3,foldr/3,mapfoldl/3,all/2,any/2,
reverse/1,reverse/2,member/2,flatten/1,
unzip/1,keyfind/3]).
-import(cerl, [ann_c_cons/3,ann_c_map/3,ann_c_tuple/2]).
-include("core_parse.hrl").
%%-define(DEBUG, 1).
-ifdef(DEBUG).
-define(ASSERT(E),
case E of
true ->
ok;
false ->
io:format("~p, line ~p: assertion failed\n", [?MODULE,?LINE]),
error(assertion_failed)
end).
-else.
-define(ASSERT(E), ignore).
-endif.
%% Variable value info.
-record(sub, {v=[], %Variable substitutions
s=cerl_sets:new() :: cerl_sets:set(), %Variables in scope
t=#{} :: map(), %Types
in_guard=false}). %In guard or not.
-type type_info() :: cerl:cerl() | 'bool' | 'integer' | {'fun', pos_integer()}.
-type yes_no_maybe() :: 'yes' | 'no' | 'maybe'.
-type sub() :: #sub{}.
-spec module(cerl:c_module(), [compile:option()]) ->
{'ok', cerl:c_module(), [_]}.
module(#c_module{defs=Ds0}=Mod, Opts) ->
put(no_inline_list_funcs, not member(inline_list_funcs, Opts)),
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 ->
io:fwrite("Function: ~w/~w\n", [F,Arity]),
erlang:raise(Class, Error, Stack)
end.
find_fixpoint(_OptFun, Core, 0) ->
Core;
find_fixpoint(OptFun, Core0, Max) ->
case OptFun(Core0) of
Core0 -> Core0;
Core -> find_fixpoint(OptFun, Core, Max-1)
end.
%% body(Expr, Sub) -> Expr.
%% body(Expr, Context, Sub) -> Expr.
%% No special handling of anything except values.
body(Body, Sub) ->
body(Body, value, Sub).
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).
%% guard(Expr, Sub) -> Expr.
%% Do guard expression. We optimize it in the same way as
%% expressions in function bodies.
guard(Expr, Sub) ->
?ASSERT(verify_scope(Expr, Sub)),
expr(Expr, value, Sub#sub{in_guard=true}).
%% opt_guard_try(Expr) -> Expr.
%%
opt_guard_try(#c_seq{arg=Arg,body=Body0}=Seq) ->
Body = opt_guard_try(Body0),
WillFail = case Body of
#c_call{module=#c_literal{val=erlang},
name=#c_literal{val=error},
args=[_]} ->
true;
#c_literal{val=false} ->
true;
_ ->
false
end,
case Arg of
#c_call{module=#c_literal{val=Mod},
name=#c_literal{val=Name},
args=Args} when WillFail ->
%% We have sequence consisting of a call (evaluated
%% for a possible exception and/or side effect only),
%% followed by 'false' or a call to error/1.
%% Since the sequence is inside a try block that will
%% default to 'false' if any exception occurs, not
%% evalutating the call will not change the behaviour
%% provided that the call has no side effects.
case erl_bifs:is_pure(Mod, Name, length(Args)) of
false ->
%% Not a pure BIF (meaning that this is not
%% a guard and that we must keep the call).
Seq#c_seq{body=Body};
true ->
%% The BIF has no side effects, so it can
%% be safely removed.
Body
end;
_ ->
Seq#c_seq{body=Body}
end;
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 ->
opt_guard_try(#c_seq{arg=Arg,body=B});
B ->
Term#c_let{body=B}
end;
opt_guard_try(Term) -> Term.
opt_guard_try_list([C|Cs]) ->
[opt_guard_try(C)|opt_guard_try_list(Cs)];
opt_guard_try_list([]) -> [].
%% expr(Expr, Sub) -> Expr.
%% expr(Expr, Context, Sub) -> Expr.
expr(Expr, Sub) ->
expr(Expr, value, Sub).
expr(#c_var{}=V, Ctxt, Sub) ->
%% Return void() in effect context to potentially shorten the life time
%% of the variable and potentially generate better code
%% (for instance, if the variable no longer needs to survive a function
%% call, there will be no need to save it in the stack frame).
case Ctxt of
effect -> void();
value -> sub_get_var(V, Sub)
end;
expr(#c_literal{val=Val}=L, Ctxt, _Sub) ->
case Ctxt of
effect ->
case Val of
[] ->
%% Keep as [] - might give slightly better code.
L;
_ when is_atom(Val) ->
%% For cleanliness replace with void().
void();
_ ->
%% Warn and replace with void().
add_warning(L, useless_building),
void()
end;
value -> L
end;
expr(#c_cons{anno=Anno,hd=H0,tl=T0}=Cons, Ctxt, Sub) ->
H1 = expr(H0, Ctxt, Sub),
T1 = expr(T0, Ctxt, Sub),
case Ctxt of
effect ->
add_warning(Cons, useless_building),
make_effect_seq([H1,T1], Sub);
value ->
ann_c_cons(Anno, H1, T1)
end;
expr(#c_tuple{anno=Anno,es=Es0}=Tuple, Ctxt, Sub) ->
Es = expr_list(Es0, Ctxt, Sub),
case Ctxt of
effect ->
add_warning(Tuple, useless_building),
make_effect_seq(Es, Sub);
value ->
ann_c_tuple(Anno, Es)
end;
expr(#c_map{anno=Anno,arg=V0,es=Es0}=Map, Ctxt, Sub) ->
Es = pair_list(Es0, Ctxt, Sub),
case Ctxt of
effect ->
add_warning(Map, useless_building),
make_effect_seq(Es, Sub);
value ->
V = expr(V0, Ctxt, Sub),
ann_c_map(Anno,V,Es)
end;
expr(#c_binary{segments=Ss}=Bin0, Ctxt, Sub) ->
%% Warn for useless building, but always build the binary
%% anyway to preserve a possible exception.
case Ctxt of
effect -> add_warning(Bin0, useless_building);
value -> ok
end,
Bin1 = Bin0#c_binary{segments=bitstr_list(Ss, Sub)},
Bin = bin_un_utf(Bin1),
eval_binary(Bin);
expr(#c_fun{}=Fun, effect, _) ->
%% A fun is created, but not used. Warn, and replace with the void value.
add_warning(Fun, useless_building),
void();
expr(#c_fun{vars=Vs0,body=B0}=Fun, Ctxt0, Sub0) ->
{Vs1,Sub1} = var_list(Vs0, Sub0),
Ctxt = case Ctxt0 of
{letrec,Ctxt1} -> Ctxt1;
value -> value
end,
B1 = body(B0, Ctxt, Sub1),
Fun#c_fun{vars=Vs1,body=B1};
expr(#c_seq{arg=Arg0,body=B0}=Seq0, Ctxt, Sub) ->
%% Optimise away pure literal arg as its value is ignored.
B1 = body(B0, Ctxt, Sub),
Arg = body(Arg0, effect, Sub),
case will_fail(Arg) of
true ->
Arg;
false ->
%% Arg cannot be "values" here - only a single value
%% make sense here.
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) ->
Let = opt_case_in_let(Let0),
case simplify_let(Let, Sub) of
impossible ->
%% 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);
Expr ->
%% The let body was successfully moved into the let argument.
%% Now recursively re-process the new expression.
Expr
end;
expr(#c_letrec{body=#c_var{}}=Letrec, effect, _Sub) ->
%% This is named fun in an 'effect' context. Warn and ignore.
add_warning(Letrec, useless_building),
void();
expr(#c_letrec{defs=Fs0,body=B0}=Letrec, Ctxt, Sub) ->
Fs1 = map(fun ({Name,Fb}) ->
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};
expr(#c_case{}=Case0, Ctxt, Sub) ->
%% Ideally, the compiler should only emit warnings when there is
%% a real mistake in the code being compiled. We use the follow
%% heuristics in an attempt to approach that ideal:
%%
%% * If the guard for a clause always fails, we will emit a
%% warning.
%%
%% * If a case expression is a literal, we will emit no warnings
%% for clauses that will not match or for clauses that are
%% shadowed after a clause that will always match. That means
%% that code such as:
%%
%% case ?DEBUG of
%% false -> ok;
%% true -> ...
%% end
%%
%% (where ?DEBUG expands to either 'true' or 'false') will not
%% produce any warnings.
%%
%% * If the case expression is not literal, warnings will be
%% emitted for every clause that don't match and for all
%% clauses following a clause that will always match.
%%
%% * If no clause will ever match, there will be a warning
%% (in addition to any warnings that may have been emitted
%% according to the rules above).
%%
case opt_bool_case(Case0, Sub) of
#c_case{arg=Arg0,clauses=Cs0}=Case1 ->
Arg1 = body(Arg0, value, Sub),
LitExpr = cerl:is_literal(Arg1),
{Arg2,Cs1} = case_opt(Arg1, Cs0, Sub),
Cs2 = clauses(Arg2, Cs1, Ctxt, Sub, LitExpr),
Case = Case1#c_case{arg=Arg2,clauses=Cs2},
warn_no_clause_match(Case1, Case),
Expr = eval_case(Case, Sub),
move_case_into_arg(Expr, Sub);
Other ->
expr(Other, Ctxt, Sub)
end;
expr(#c_receive{clauses=Cs0,timeout=T0,action=A0}=Recv, Ctxt, Sub) ->
Cs1 = clauses(#c_var{name='_'}, Cs0, Ctxt, Sub, false),
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}=Apply0, _, Sub) ->
Op1 = expr(Op0, value, Sub),
As1 = expr_list(As0, value, Sub),
case cerl:is_data(Op1) andalso not is_literal_fun(Op1) of
false ->
Apply = Apply0#c_apply{op=Op1,args=As1},
fold_apply(Apply, Op1, As1);
true ->
add_warning(Apply0, invalid_call),
Err = #c_call{anno=Anno,
module=#c_literal{val=erlang},
name=#c_literal{val=error},
args=[#c_tuple{es=[#c_literal{val='badfun'},
Op1]}]},
make_effect_seq(As1++[Err], Sub)
end;
expr(#c_call{module=M0,name=N0}=Call0, Ctxt, Sub) ->
M1 = expr(M0, value, Sub),
N1 = expr(N0, value, Sub),
Call = Call0#c_call{module=M1,name=N1},
case useless_call(Ctxt, Call) of
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),
case is_safe_simple(B1, Sub) of
true -> B1;
false -> Catch#c_catch{body=B1}
end;
expr(#c_try{arg=E0,vars=[#c_var{name=X}],body=#c_var{name=X},
handler=#c_literal{val=false}=False}=Try, _, Sub) ->
%% Since guard may call expr/2, we must do some optimization of
%% the kind of try's that occur in guards.
E1 = body(E0, value, Sub),
case will_fail(E1) of
false ->
%% Remove any calls that are evaluated for effect only.
E2 = opt_guard_try(E1),
%% We can remove try/catch if the expression is an
%% expression that cannot fail.
case is_safe_bool_expr(E2, Sub) orelse is_safe_simple(E2, Sub) of
true -> E2;
false -> Try#c_try{arg=E2}
end;
true ->
%% Expression will always fail.
False
end;
expr(#c_try{anno=A,arg=E0,vars=Vs0,body=B0,evars=Evs0,handler=H0}=Try, _, Sub0) ->
%% Here is the general try/catch construct outside of guards.
%% We can remove try if the value is simple and replace it with a let.
E1 = body(E0, value, Sub0),
{Vs1,Sub1} = var_list(Vs0, Sub0),
B1 = body(B0, value, Sub1),
case is_safe_simple(E1, Sub0) of
true ->
expr(#c_let{anno=A,vars=Vs1,arg=E1,body=B1}, value, Sub0);
false ->
{Evs1,Sub2} = var_list(Evs0, Sub0),
H1 = body(H0, value, Sub2),
H2 = opt_try_handler(H1, lists:last(Evs1)),
Try#c_try{arg=E1,vars=Vs1,body=B1,evars=Evs1,handler=H2}
end.
%% Attempts to convert old erlang:get_stacktrace/0 calls into the new
%% three-argument catch, with possibility of further optimisations.
opt_try_handler(#c_call{anno=A,module=#c_literal{val=erlang},name=#c_literal{val=get_stacktrace},args=[]}, Var) ->
#c_primop{anno=A,name=#c_literal{val=build_stacktrace},args=[Var]};
opt_try_handler(#c_case{clauses=Cs0} = Case, Var) ->
Cs = [C#c_clause{body=opt_try_handler(B, Var)} || #c_clause{body=B} = C <- Cs0],
Case#c_case{clauses=Cs};
opt_try_handler(#c_let{arg=Arg} = Let, Var) ->
Let#c_let{arg=opt_try_handler(Arg, Var)};
opt_try_handler(X, _) -> X.
%% 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].
pair_list(Es, Ctxt, Sub) ->
[pair(E, Ctxt, Sub) || E <- Es].
pair(#c_map_pair{key=K,val=V}, effect, Sub) ->
make_effect_seq([K,V], Sub);
pair(#c_map_pair{key=K0,val=V0}=Pair, value=Ctxt, Sub) ->
K = expr(K0, Ctxt, Sub),
V = expr(V0, Ctxt, Sub),
Pair#c_map_pair{key=K,val=V}.
bitstr_list(Es, Sub) ->
[bitstr(E, Sub) || E <- Es].
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.
%%
%% Currently, we don't attempt to check binaries because they
%% are difficult to check.
is_safe_simple(#c_var{}=Var, _) ->
not cerl:is_c_fname(Var);
is_safe_simple(#c_cons{hd=H,tl=T}, Sub) ->
is_safe_simple(H, Sub) andalso is_safe_simple(T, Sub);
is_safe_simple(#c_tuple{es=Es}, Sub) -> is_safe_simple_list(Es, Sub);
is_safe_simple(#c_literal{}, _) -> true;
is_safe_simple(#c_call{module=#c_literal{val=erlang},
name=#c_literal{val=Name},
args=Args}, Sub) when is_atom(Name) ->
NumArgs = length(Args),
case erl_internal:bool_op(Name, NumArgs) of
true ->
%% Boolean operators are safe if the arguments are boolean.
all(fun(C) -> is_boolean_type(C, Sub) =:= yes end, Args);
false ->
%% We need a rather complicated test to ensure that
%% we only allow safe calls that are allowed in a guard.
%% (Note that is_function/2 is a type test, but is not safe.)
erl_bifs:is_safe(erlang, Name, NumArgs) andalso
(erl_internal:comp_op(Name, NumArgs) orelse
erl_internal:new_type_test(Name, NumArgs))
end;
is_safe_simple(_, _) -> false.
is_safe_simple_list(Es, Sub) -> all(fun(E) -> is_safe_simple(E, Sub) end, Es).
%% will_fail(Expr) -> true|false.
%% Determine whether the expression will fail with an exception.
%% Return true if the expression always will fail with an exception,
%% i.e. never return normally.
will_fail(#c_let{arg=A,body=B}) ->
will_fail(A) orelse will_fail(B);
will_fail(#c_call{module=#c_literal{val=Mod},name=#c_literal{val=Name},args=Args}) ->
erl_bifs:is_exit_bif(Mod, Name, length(Args));
will_fail(#c_primop{name=#c_literal{val=match_fail},args=[_]}) -> true;
will_fail(_) -> false.
%% bin_un_utf(#c_binary{}) -> #c_binary{}
%% Convert any literal UTF-8/16/32 literals to byte-sized
%% integer fields.
bin_un_utf(#c_binary{anno=Anno,segments=Ss}=Bin) ->
Bin#c_binary{segments=bin_un_utf_1(Ss, Anno)}.
bin_un_utf_1([#c_bitstr{val=#c_literal{},type=#c_literal{val=utf8}}=H|T],
Anno) ->
bin_un_utf_eval(H, Anno) ++ bin_un_utf_1(T, Anno);
bin_un_utf_1([#c_bitstr{val=#c_literal{},type=#c_literal{val=utf16}}=H|T],
Anno) ->
bin_un_utf_eval(H, Anno) ++ bin_un_utf_1(T, Anno);
bin_un_utf_1([#c_bitstr{val=#c_literal{},type=#c_literal{val=utf32}}=H|T],
Anno) ->
bin_un_utf_eval(H, Anno) ++ bin_un_utf_1(T, Anno);
bin_un_utf_1([H|T], Anno) ->
[H|bin_un_utf_1(T, Anno)];
bin_un_utf_1([], _) -> [].
bin_un_utf_eval(Bitstr, Anno) ->
Segments = [Bitstr],
case eval_binary(#c_binary{anno=Anno,segments=Segments}) of
#c_literal{anno=Anno,val=Bytes} when is_binary(Bytes) ->
[#c_bitstr{anno=Anno,
val=#c_literal{anno=Anno,val=B},
size=#c_literal{anno=Anno,val=8},
unit=#c_literal{anno=Anno,val=1},
type=#c_literal{anno=Anno,val=integer},
flags=#c_literal{anno=Anno,val=[unsigned,big]}} ||
B <- binary_to_list(Bytes)];
_ ->
Segments
end.
%% eval_binary(#c_binary{}) -> #c_binary{} | #c_literal{}
%% Evaluate a binary at compile time if possible to create
%% a binary literal.
eval_binary(#c_binary{anno=Anno,segments=Ss}=Bin) ->
try
#c_literal{anno=Anno,val=eval_binary_1(Ss, <<>>)}
catch
throw:impossible ->
Bin;
throw:{badarg,Warning} ->
add_warning(Bin, Warning),
#c_call{anno=Anno,
module=#c_literal{val=erlang},
name=#c_literal{val=error},
args=[#c_literal{val=badarg}]}
end.
eval_binary_1([#c_bitstr{val=#c_literal{val=Val},size=#c_literal{val=Sz},
unit=#c_literal{val=Unit},type=#c_literal{val=Type},
flags=#c_literal{val=Flags}}|Ss], Acc0) ->
Endian = case member(big, Flags) of
true ->
big;
false ->
case member(little, Flags) of
true -> little;
false -> throw(impossible) %Native endian.
end
end,
%% Make sure that the size is reasonable.
case Type of
binary when is_bitstring(Val) ->
if
Sz =:= all ->
ok;
Sz*Unit =< bit_size(Val) ->
ok;
true ->
%% Field size is greater than the actual binary - will fail.
throw({badarg,embedded_binary_size})
end;
integer when is_integer(Val) ->
%% Estimate the number of bits needed to to hold the integer
%% literal. Check whether the field size is reasonable in
%% proportion to the number of bits needed.
if
Sz*Unit =< 256 ->
%% Don't be cheap - always accept fields up to this size.
ok;
true ->
case count_bits(Val) of
BitsNeeded when 2*BitsNeeded >= Sz*Unit ->
ok;
_ ->
%% More than about half of the field size will be
%% filled out with zeroes - not acceptable.
throw(impossible)
end
end;
float when is_float(Val) ->
%% Bad float size.
case Sz*Unit of
32 -> ok;
64 -> ok;
_ -> throw(impossible)
end;
utf8 -> ok;
utf16 -> ok;
utf32 -> ok;
_ ->
throw(impossible)
end,
%% Evaluate the field.
try eval_binary_2(Acc0, Val, Sz, Unit, Type, Endian) of
Acc -> eval_binary_1(Ss, Acc)
catch
error:_ ->
throw(impossible)
end;
eval_binary_1([], Acc) -> Acc;
eval_binary_1(_, _) -> throw(impossible).
eval_binary_2(Acc, Val, Size, Unit, integer, little) ->
<<Acc/bitstring,Val:(Size*Unit)/little>>;
eval_binary_2(Acc, Val, Size, Unit, integer, big) ->
<<Acc/bitstring,Val:(Size*Unit)/big>>;
eval_binary_2(Acc, Val, _Size, _Unit, utf8, _) ->
try
<<Acc/bitstring,Val/utf8>>
catch
error:_ ->
throw({badarg,bad_unicode})
end;
eval_binary_2(Acc, Val, _Size, _Unit, utf16, big) ->
try
<<Acc/bitstring,Val/big-utf16>>
catch
error:_ ->
throw({badarg,bad_unicode})
end;
eval_binary_2(Acc, Val, _Size, _Unit, utf16, little) ->
try
<<Acc/bitstring,Val/little-utf16>>
catch
error:_ ->
throw({badarg,bad_unicode})
end;
eval_binary_2(Acc, Val, _Size, _Unit, utf32, big) ->
try
<<Acc/bitstring,Val/big-utf32>>
catch
error:_ ->
throw({badarg,bad_unicode})
end;
eval_binary_2(Acc, Val, _Size, _Unit, utf32, little) ->
try
<<Acc/bitstring,Val/little-utf32>>
catch
error:_ ->
throw({badarg,bad_unicode})
end;
eval_binary_2(Acc, Val, Size, Unit, float, little) ->
<<Acc/bitstring,Val:(Size*Unit)/little-float>>;
eval_binary_2(Acc, Val, Size, Unit, float, big) ->
<<Acc/bitstring,Val:(Size*Unit)/big-float>>;
eval_binary_2(Acc, Val, all, Unit, binary, _) ->
case bit_size(Val) of
Size when Size rem Unit =:= 0 ->
<<Acc/bitstring,Val:Size/bitstring>>;
Size ->
throw({badarg,{embedded_unit,Unit,Size}})
end;
eval_binary_2(Acc, Val, Size, Unit, binary, _) ->
<<Acc/bitstring,Val:(Size*Unit)/bitstring>>.
%% Count the number of bits approximately needed to store Int.
%% (We don't need an exact result for this purpose.)
count_bits(Int) ->
count_bits_1(abs(Int), 64).
count_bits_1(0, Bits) -> Bits;
count_bits_1(Int, Bits) -> count_bits_1(Int bsr 64, Bits+64).
%% useless_call(Context, #c_call{}) -> no | {yes,Expr}
%% Check whether the function is called only for effect,
%% and if the function either has no effect whatsoever or
%% the only effect is an exception. Generate appropriate
%% warnings. If the call is "useless" (has no effect),
%% a rewritten expression consisting of a sequence of
%% the arguments only is returned.
useless_call(effect, #c_call{module=#c_literal{val=Mod},
name=#c_literal{val=Name},
args=Args}=Call) ->
A = length(Args),
case erl_bifs:is_safe(Mod, Name, A) of
false ->
case erl_bifs:is_pure(Mod, Name, A) of
true -> add_warning(Call, result_ignored);
false -> ok
end,
no;
true ->
add_warning(Call, {no_effect,{Mod,Name,A}}),
{yes,make_effect_seq(Args, sub_new())}
end;
useless_call(_, _) -> no.
%% make_effect_seq([Expr], Sub) -> #c_seq{}|void()
%% Convert a list of expressions evaluated in effect context to a chain of
%% #c_seq{}. The body in the innermost #c_seq{} will be void().
%% Anything that will not have any effect will be thrown away.
make_effect_seq([H|T], Sub) ->
case is_safe_simple(H, Sub) of
true -> make_effect_seq(T, Sub);
false -> #c_seq{arg=H,body=make_effect_seq(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) ->
case get(no_inline_list_funcs) of
true ->
call_1(Call, M0, N0, As, Sub);
false ->
case sys_core_fold_lists:call(Call, M, N, As) of
none ->
call_1(Call, M0, N0, As, Sub);
Core ->
expr(Core, Sub)
end
end;
call(#c_call{args=As}=Call, M, N, Sub) ->
call_1(Call, M, N, As, Sub).
call_1(Call, M, N, As0, Sub) ->
As1 = expr_list(As0, value, Sub),
fold_call(Call#c_call{args=As1}, M, N, As1, Sub).
%% fold_call(Call, Mod, Name, Args, Sub) -> Expr.
%% Try to safely evaluate the call. Just try to evaluate arguments,
%% do the call and convert return values to literals. If this
%% succeeds then use the new value, otherwise just fail and use
%% original call. Do this at every level.
%%
%% We attempt to evaluate calls to certain BIFs even if the
%% arguments are not literals. For instance, we evaluate length/1
%% if the shape of the list is known, and element/2 and setelement/3
%% if the position is constant and the shape of the tuple is known.
%%
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) ->
NumArgs = length(Args),
case erl_bifs:is_pure(Mod, Name, NumArgs) of
false -> Call; %Not pure - keep call.
true -> fold_call_2(Call, Mod, Name, Args, Sub)
end.
fold_call_2(Call, Module, Name, Args, Sub) ->
case all(fun cerl:is_literal/1, Args) of
true ->
%% All arguments are literals.
fold_lit_args(Call, Module, Name, Args);
false ->
%% At least one non-literal argument.
fold_non_lit_args(Call, Module, Name, Args, Sub)
end.
fold_lit_args(Call, Module, Name, Args0) ->
Args = [cerl:concrete(A) || A <- Args0],
try apply(Module, Name, Args) of
Val ->
case cerl:is_literal_term(Val) of
true ->
cerl:ann_abstract(cerl:get_ann(Call), Val);
false ->
%% Successful evaluation, but it was not possible
%% to express the computed value as a literal.
Call
end
catch
error:Reason ->
%% Evaluation of the function failed. Warn and replace
%% the call with a call to erlang:error/1.
eval_failure(Call, Reason)
end.
%% fold_non_lit_args(Call, Module, Name, Args, Sub) -> Expr.
%% Attempt to evaluate some pure BIF calls with one or more
%% non-literals arguments.
%%
fold_non_lit_args(Call, erlang, is_boolean, [Arg], Sub) ->
eval_is_boolean(Call, Arg, Sub);
fold_non_lit_args(Call, erlang, length, [Arg], _) ->
eval_length(Call, Arg);
fold_non_lit_args(Call, erlang, '++', [Arg1,Arg2], _) ->
eval_append(Call, Arg1, Arg2);
fold_non_lit_args(Call, lists, append, [Arg1,Arg2], _) ->
eval_append(Call, Arg1, Arg2);
fold_non_lit_args(Call, erlang, is_function, [Arg1], Sub) ->
eval_is_function_1(Call, Arg1, Sub);
fold_non_lit_args(Call, erlang, is_function, [Arg1,Arg2], Sub) ->
eval_is_function_2(Call, Arg1, Arg2, Sub);
fold_non_lit_args(Call, erlang, N, Args, Sub) ->
NumArgs = length(Args),
case erl_internal:comp_op(N, NumArgs) of
true ->
eval_rel_op(Call, N, Args, Sub);
false ->
case erl_internal:bool_op(N, NumArgs) of
true ->
eval_bool_op(Call, N, Args, Sub);
false ->
Call
end
end;
fold_non_lit_args(Call, _, _, _, _) -> Call.
eval_is_function_1(Call, Arg1, Sub) ->
case get_type(Arg1, Sub) of
none -> Call;
{'fun',_} -> #c_literal{anno=cerl:get_ann(Call),val=true};
_ -> #c_literal{anno=cerl:get_ann(Call),val=false}
end.
eval_is_function_2(Call, Arg1, #c_literal{val=Arity}, Sub)
when is_integer(Arity), Arity > 0 ->
case get_type(Arg1, Sub) of
none -> Call;
{'fun',Arity} -> #c_literal{anno=cerl:get_ann(Call),val=true};
_ -> #c_literal{anno=cerl:get_ann(Call),val=false}
end;
eval_is_function_2(Call, _Arg1, _Arg2, _Sub) -> Call.
%% Evaluate a relational operation using type information.
eval_rel_op(Call, Op, [#c_var{name=V},#c_var{name=V}], _) ->
Bool = erlang:Op(same, same),
#c_literal{anno=cerl:get_ann(Call),val=Bool};
eval_rel_op(Call, '=:=', [Term,#c_literal{val=true}], Sub) ->
%% BoolVar =:= true ==> BoolVar
case is_boolean_type(Term, Sub) of
yes -> Term;
maybe -> Call;
no -> #c_literal{val=false}
end;
eval_rel_op(Call, '==', Ops, Sub) ->
case is_exact_eq_ok(Ops, Sub) of
true ->
Name = #c_literal{anno=cerl:get_ann(Call),val='=:='},
Call#c_call{name=Name};
false ->
Call
end;
eval_rel_op(Call, '/=', Ops, Sub) ->
case is_exact_eq_ok(Ops, Sub) of
true ->
Name = #c_literal{anno=cerl:get_ann(Call),val='=/='},
Call#c_call{name=Name};
false ->
Call
end;
eval_rel_op(Call, _, _, _) -> Call.
is_exact_eq_ok([A,B]=L, Sub) ->
case is_int_type(A, Sub) =:= yes andalso is_int_type(B, Sub) =:= yes of
true -> true;
false -> is_exact_eq_ok_1(L)
end.
is_exact_eq_ok_1([#c_literal{val=Lit}|_]) ->
is_non_numeric(Lit);
is_exact_eq_ok_1([_|T]) ->
is_exact_eq_ok_1(T);
is_exact_eq_ok_1([]) -> false.
is_non_numeric([H|T]) ->
is_non_numeric(H) andalso is_non_numeric(T);
is_non_numeric(Tuple) when is_tuple(Tuple) ->
is_non_numeric_tuple(Tuple, tuple_size(Tuple));
is_non_numeric(Map) when is_map(Map) ->
%% Note that 17.x and 18.x compare keys in different ways.
%% Be very conservative -- require that both keys and values
%% are non-numeric.
is_non_numeric(maps:to_list(Map));
is_non_numeric(Num) when is_number(Num) ->
false;
is_non_numeric(_) -> true.
is_non_numeric_tuple(Tuple, El) when El >= 1 ->
is_non_numeric(element(El, Tuple)) andalso
is_non_numeric_tuple(Tuple, El-1);
is_non_numeric_tuple(_Tuple, 0) -> true.
%% Evaluate a bool op using type information. We KNOW that
%% there must be at least one non-literal argument (i.e.
%% there is no need to handle the case that all argments
%% are literal).
eval_bool_op(Call, 'and', [#c_literal{val=true},Term], Sub) ->
eval_bool_op_1(Call, Term, Term, Sub);
eval_bool_op(Call, 'and', [Term,#c_literal{val=true}], Sub) ->
eval_bool_op_1(Call, Term, Term, Sub);
eval_bool_op(Call, 'and', [#c_literal{val=false}=Res,Term], Sub) ->
eval_bool_op_1(Call, Res, Term, Sub);
eval_bool_op(Call, 'and', [Term,#c_literal{val=false}=Res], Sub) ->
eval_bool_op_1(Call, Res, Term, Sub);
eval_bool_op(Call, _, _, _) -> Call.
eval_bool_op_1(Call, Res, Term, Sub) ->
case is_boolean_type(Term, Sub) of
yes -> Res;
no -> eval_failure(Call, badarg);
maybe -> Call
end.
%% Evaluate is_boolean/1 using type information.
eval_is_boolean(Call, Term, Sub) ->
case is_boolean_type(Term, Sub) of
no -> #c_literal{val=false};
yes -> #c_literal{val=true};
maybe -> Call
end.
%% eval_length(Call, List) -> Val.
%% Evaluates the length for the prefix of List which has a known
%% shape.
%%
eval_length(Call, Core) -> eval_length(Call, Core, 0).
eval_length(Call, #c_literal{val=Val}, Len0) ->
try
Len = Len0 + length(Val),
#c_literal{anno=Call#c_call.anno,val=Len}
catch
_:_ ->
eval_failure(Call, badarg)
end;
eval_length(Call, #c_cons{tl=T}, Len) ->
eval_length(Call, T, Len+1);
eval_length(Call, _List, 0) ->
Call; %Could do nothing
eval_length(Call, List, Len) ->
A = Call#c_call.anno,
#c_call{anno=A,
module=#c_literal{anno=A,val=erlang},
name=#c_literal{anno=A,val='+'},
args=[#c_literal{anno=A,val=Len},Call#c_call{args=[List]}]}.
%% eval_append(Call, FirstList, SecondList) -> Val.
%% Evaluates the constant part of '++' expression.
%%
eval_append(Call, #c_literal{val=Cs1}=S1, #c_literal{val=Cs2}) ->
try
S1#c_literal{val=Cs1 ++ Cs2}
catch error:badarg ->
eval_failure(Call, badarg)
end;
eval_append(Call, #c_literal{val=Cs}, List) when length(Cs) =< 4 ->
Anno = Call#c_call.anno,
foldr(fun (C, L) ->
ann_c_cons(Anno, #c_literal{val=C}, L)
end, List, Cs);
eval_append(Call, #c_cons{anno=Anno,hd=H,tl=T}, List) ->
ann_c_cons(Anno, H, eval_append(Call, T, List));
eval_append(Call, X, Y) ->
Call#c_call{args=[X,Y]}. %Rebuild call arguments.
%% eval_failure(Call, Reason) -> Core.
%% Warn for a call that will fail and replace the call with
%% a call to erlang:error(Reason).
%%
eval_failure(Call, Reason) ->
add_warning(Call, {eval_failure,Reason}),
Call#c_call{module=#c_literal{val=erlang},
name=#c_literal{val=error},
args=[#c_literal{val=Reason}]}.
%% simplify_apply(Call0, Mod, Func, Args) -> Call
%% Simplify an apply/3 to a call if the number of arguments
%% are known at compile time.
simplify_apply(Call, Mod, Func, Args0) ->
case is_atom_or_var(Mod) andalso is_atom_or_var(Func) of
true ->
case get_fixed_args(Args0, []) of
error ->
Call;
{ok,Args} ->
Call#c_call{module=Mod,name=Func,args=Args}
end;
false ->
Call
end.
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) ->
try pattern_list(Ps0, Sub0) of
{Ps1,Sub1} ->
clause_1(Cl, Ps1, Cexpr, Ctxt, Sub1)
catch
nomatch ->
Cl#c_clause{anno=[compiler_generated],
guard=#c_literal{val=false}}
end.
clause_1(#c_clause{guard=G0,body=B0}=Cl, Ps1, Cexpr, Ctxt, Sub1) ->
GSub = case {Cexpr,Ps1,G0} of
{_,_,#c_literal{}} ->
%% No need for substitution tricks when the guard
%% does not contain any variables.
Sub1;
{#c_var{name='_'},_,_} ->
%% In a 'receive', Cexpr is the variable '_', which represents the
%% message being matched. We must NOT do any extra substiutions.
Sub1;
{#c_var{},[#c_var{}=Var],_} ->
%% The idea here is to optimize expressions such as
%%
%% case A of A -> ...
%%
%% to get rid of the extra guard test that the compiler
%% added when converting to the Core Erlang representation:
%%
%% case A of NewVar when A =:= NewVar -> ...
%%
%% By replacing NewVar with A everywhere in the guard
%% expression, we get
%%
%% case A of NewVar when A =:= A -> ...
%%
%% which by constant-expression evaluation is reduced to
%%
%% case A of NewVar when true -> ...
%%
case cerl:is_c_fname(Cexpr) of
false ->
sub_set_var(Var, Cexpr, Sub1);
true ->
%% We must not copy funs, and especially not into guards.
Sub1
end;
_ ->
Sub1
end,
G1 = guard(G0, GSub),
B1 = body(B0, Ctxt, Sub1),
Cl#c_clause{pats=Ps1,guard=G1,body=B1}.
%% let_substs(LetVars, LetArg, Sub) -> {[Var],[Val],Sub}.
%% Add suitable substitutions to Sub of variables in LetVars. First
%% remove variables in LetVars from Sub, then fix subs. N.B. must
%% work out new subs in parallel and then apply them to subs. Return
%% the unsubstituted variables and values.
let_substs(Vs0, As0, Sub0) ->
{Vs1,Sub1} = var_list(Vs0, Sub0),
{Vs2,As1,Ss} = let_substs_1(Vs1, As0, Sub1),
Sub2 = sub_add_scope([V || #c_var{name=V} <- Vs2], Sub1),
{Vs2,As1,
foldl(fun ({V,S}, Sub) -> sub_set_name(V, S, Sub) end, Sub2, Ss)}.
let_substs_1(Vs, #c_values{es=As}, Sub) ->
let_subst_list(Vs, As, Sub);
let_substs_1([V], A, Sub) -> let_subst_list([V], [A], Sub);
let_substs_1(Vs, A, _) -> {Vs,A,[]}.
let_subst_list([V|Vs0], [A0|As0], Sub) ->
{Vs1,As1,Ss} = let_subst_list(Vs0, As0, Sub),
case is_subst(A0) of
true ->
A = case is_compiler_generated(V) andalso
not is_compiler_generated(A0) of
true ->
%% Propagate the 'compiler_generated' annotation
%% along with the value.
Ann = [compiler_generated|cerl:get_ann(A0)],
cerl:set_ann(A0, Ann);
false ->
A0
end,
{Vs1,As1,sub_subst_var(V, A, Sub) ++ Ss};
false ->
{[V|Vs1],[A0|As1],Ss}
end;
let_subst_list([], [], _) -> {[],[],[]}.
%% pattern(Pattern, InSub) -> {Pattern,OutSub}.
%% pattern(Pattern, InSub, OutSub) -> {Pattern,OutSub}.
%% Variables occurring in Pattern will shadow so they must be removed
%% from Sub. If they occur as a value in Sub then we create a new
%% variable and then add a substitution for that.
%%
%% Patterns are complicated by sizes in binaries. These are pure
%% input variables which create no bindings. We, therefore, need to
%% carry around the original substitutions to get the correct
%% handling.
%%pattern(Pat, Sub) -> pattern(Pat, Sub, Sub).
pattern(#c_var{}=Pat, Isub, Osub) ->
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 ->
%% 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) ->
{H1,Osub1} = pattern(H0, Isub, Osub0),
{T1,Osub2} = pattern(T0, Isub, Osub1),
{ann_c_cons(Anno, H1, T1),Osub2};
pattern(#c_tuple{anno=Anno,es=Es0}, Isub, Osub0) ->
{Es1,Osub1} = pattern_list(Es0, Isub, Osub0),
{ann_c_tuple(Anno, Es1),Osub1};
pattern(#c_map{anno=Anno,es=Es0}=Map, Isub, Osub0) ->
{Es1,Osub1} = map_pair_pattern_list(Es0, Isub, Osub0),
{Map#c_map{anno=Anno,es=Es1},Osub1};
pattern(#c_binary{segments=V0}=Pat, Isub, Osub0) ->
{V1,Osub1} = bin_pattern_list(V0, Isub, Osub0),
{Pat#c_binary{segments=V1},Osub1};
pattern(#c_alias{var=V0,pat=P0}=Pat, Isub, Osub0) ->
{V1,Osub1} = pattern(V0, Isub, Osub0),
{P1,Osub} = pattern(P0, Isub, Osub1),
{Pat#c_alias{var=V1,pat=P1},Osub}.
map_pair_pattern_list(Ps0, Isub, Osub0) ->
{Ps,{_,Osub}} = mapfoldl(fun map_pair_pattern/2, {Isub,Osub0}, Ps0),
{Ps,Osub}.
map_pair_pattern(#c_map_pair{op=#c_literal{val=exact},key=K0,val=V0}=Pair,{Isub,Osub0}) ->
K = expr(K0, Isub),
{V,Osub} = pattern(V0,Isub,Osub0),
{Pair#c_map_pair{key=K,val=V},{Isub,Osub}}.
bin_pattern_list(Ps0, Isub, Osub0) ->
{Ps,{_,Osub}} = mapfoldl(fun bin_pattern/2, {Isub,Osub0}, Ps0),
{Ps,Osub}.
bin_pattern(#c_bitstr{val=E0,size=Size0}=Pat0, {Isub0,Osub0}) ->
Size1 = expr(Size0, Isub0),
{E1,Osub} = pattern(E0, Isub0, Osub0),
Isub = case E0 of
#c_var{} -> sub_set_var(E0, E1, Isub0);
_ -> Isub0
end,
Pat = Pat0#c_bitstr{val=E1,size=Size1},
bin_pat_warn(Pat),
{Pat,{Isub,Osub}}.
pattern_list(Ps, Sub) -> pattern_list(Ps, Sub, Sub).
pattern_list(Ps0, Isub, Osub0) ->
mapfoldl(fun (P, Osub) -> pattern(P, Isub, Osub) end, Osub0, Ps0).
%% var_list([Var], InSub) -> {Pattern,OutSub}.
%% Works like pattern_list/2 but only accept variables and is
%% guaranteed not to throw an exception.
var_list(Vs, Sub0) ->
mapfoldl(fun (#c_var{}=V, Sub) ->
pattern(V, Sub, Sub)
end, Sub0, Vs).
%%%
%%% Generate warnings for binary patterns that will not match.
%%%
bin_pat_warn(#c_bitstr{type=#c_literal{val=Type},
val=Val0,
size=#c_literal{val=Sz},
unit=#c_literal{val=Unit},
flags=Fl}=Pat) ->
case {Type,Sz} of
{_,_} when is_integer(Sz), Sz >= 0 -> ok;
{binary,all} -> ok;
{utf8,undefined} -> ok;
{utf16,undefined} -> ok;
{utf32,undefined} -> ok;
{_,_} ->
add_warning(Pat, {nomatch_bit_syntax_size,Sz}),
throw(nomatch)
end,
case {Type,Val0} of
{integer,#c_literal{val=Val}} when is_integer(Val) ->
Signedness = signedness(Fl),
TotalSz = Sz * Unit,
bit_pat_warn_int(Val, TotalSz, Signedness, Pat);
{float,#c_literal{val=Val}} when is_float(Val) ->
ok;
{utf8,#c_literal{val=Val}} when is_integer(Val) ->
bit_pat_warn_unicode(Val, Pat);
{utf16,#c_literal{val=Val}} when is_integer(Val) ->
bit_pat_warn_unicode(Val, Pat);
{utf32,#c_literal{val=Val}} when is_integer(Val) ->
bit_pat_warn_unicode(Val, Pat);
{_,#c_literal{val=Val}} ->
add_warning(Pat, {nomatch_bit_syntax_type,Val,Type}),
throw(nomatch);
{_,_} ->
ok
end;
bin_pat_warn(#c_bitstr{type=#c_literal{val=Type},val=Val0,flags=Fl}=Pat) ->
%% Size is variable. Not much that we can check.
case {Type,Val0} of
{integer,#c_literal{val=Val}} when is_integer(Val) ->
case signedness(Fl) of
unsigned when Val < 0 ->
add_warning(Pat, {nomatch_bit_syntax_unsigned,Val}),
throw(nomatch);
_ ->
ok
end;
{float,#c_literal{val=Val}} when is_float(Val) ->
ok;
{_,#c_literal{val=Val}} ->
add_warning(Pat, {nomatch_bit_syntax_type,Val,Type}),
throw(nomatch);
{_,_} ->
ok
end.
bit_pat_warn_int(Val, 0, signed, Pat) ->
if
Val =:= 0 ->
ok;
true ->
add_warning(Pat, {nomatch_bit_syntax_truncated,signed,Val,0}),
throw(nomatch)
end;
bit_pat_warn_int(Val, Sz, signed, Pat) ->
if
Val < 0, Val bsr (Sz - 1) =/= -1 ->
add_warning(Pat, {nomatch_bit_syntax_truncated,signed,Val,Sz}),
throw(nomatch);
Val > 0, Val bsr (Sz - 1) =/= 0 ->
add_warning(Pat, {nomatch_bit_syntax_truncated,signed,Val,Sz}),
throw(nomatch);
true ->
ok
end;
bit_pat_warn_int(Val, _Sz, unsigned, Pat) when Val < 0 ->
add_warning(Pat, {nomatch_bit_syntax_unsigned,Val}),
throw(nomatch);
bit_pat_warn_int(Val, Sz, unsigned, Pat) ->
if
Val bsr Sz =:= 0 ->
ok;
true ->
add_warning(Pat, {nomatch_bit_syntax_truncated,unsigned,Val,Sz}),
throw(nomatch)
end.
bit_pat_warn_unicode(U, _Pat) when 0 =< U, U =< 16#10FFFF ->
ok;
bit_pat_warn_unicode(U, Pat) ->
add_warning(Pat, {nomatch_bit_syntax_unicode,U}),
throw(nomatch).
signedness(#c_literal{val=Flags}) ->
[S] = [F || F <- Flags, F =:= signed orelse F =:= unsigned],
S.
%% is_subst(Expr) -> true | false.
%% Test whether an expression is a suitable substitution.
is_subst(#c_var{name={_,_}}) ->
%% Funs must not be duplicated (which will happen if the variable
%% is used more than once), because the funs will not be equal
%% (their "index" fields will be different).
false;
is_subst(#c_var{}) -> true;
is_subst(#c_literal{}) -> true;
is_subst(_) -> false.
%% sub_new() -> #sub{}.
%% sub_get_var(Var, #sub{}) -> Value.
%% sub_set_var(Var, Value, #sub{}) -> #sub{}.
%% sub_set_name(Name, Value, #sub{}) -> #sub{}.
%% sub_del_var(Var, #sub{}) -> #sub{}.
%% sub_subst_var(Var, Value, #sub{}) -> [{Name,Value}].
%% 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
%% annotations. When adding a new substitute we fold substitute
%% chains so we never have to search more than once. Use orddict so
%% we know the format.
%%
%% In addition to the list of substitutions, we also keep track of
%% all variable currently live (the scope).
%%
%% sub_add_scope/2 adds variables to the scope. sub_subst_scope/1
%% adds dummy substitutions for all variables in the scope in order
%% to force renaming if variables in the scope occurs as pattern
%% variables.
sub_new() -> #sub{v=orddict:new(),s=cerl_sets:new(),t=#{}}.
sub_new(#sub{}=Sub) ->
Sub#sub{v=orddict:new(),t=#{}}.
sub_get_var(#c_var{name=V}=Var, #sub{v=S}) ->
case orddict:find(V, S) of
{ok,Val} -> Val;
error -> Var
end.
sub_set_var(#c_var{name=V}, Val, Sub) ->
sub_set_name(V, Val, Sub).
sub_set_name(V, Val, #sub{v=S,s=Scope,t=Tdb0}=Sub) ->
Tdb1 = kill_types(V, Tdb0),
Tdb = copy_type(V, Val, Tdb1),
Sub#sub{v=orddict:store(V, Val, S),s=cerl_sets:add_element(V, Scope),t=Tdb}.
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].
sub_add_scope(Vs, #sub{s=Scope0}=Sub) ->
Scope = foldl(fun(V, S) when is_integer(V); is_atom(V) ->
cerl_sets:add_element(V, S)
end, Scope0, Vs),
Sub#sub{s=Scope}.
sub_subst_scope(#sub{v=S0,s=Scope}=Sub) ->
Initial = case S0 of
[{NegInt,_}|_] when is_integer(NegInt), NegInt < 0 ->
NegInt - 1;
_ ->
-1
end,
S = sub_subst_scope_1(cerl_sets:to_list(Scope), Initial, S0),
Sub#sub{v=orddict:from_list(S)}.
%% The keys in an orddict must be unique. Make them so!
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_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
%% will match.
warn_no_clause_match(CaseOrig, CaseOpt) ->
OrigCs = cerl:case_clauses(CaseOrig),
OptCs = cerl:case_clauses(CaseOpt),
case any(fun(C) -> not is_compiler_generated(C) end, OrigCs) andalso
all(fun is_compiler_generated/1, OptCs) of
true ->
%% The original list of clauses did contain at least one
%% user-specified clause, but none of them will match.
%% That is probably a mistake.
add_warning(CaseOrig, no_clause_match);
false ->
%% Either there were user-specified clauses left in
%% the transformed clauses, or else none of the original
%% clauses were user-specified to begin with (as in 'andalso').
ok
end.
%% clauses(E, [Clause], TopLevel, Context, Sub) -> [Clause].
%% Trim the clauses by removing all clauses AFTER the first one which
%% is guaranteed to match. Also remove all trivially false clauses.
clauses(E, [C0|Cs], Ctxt, Sub, LitExpr) ->
#c_clause{pats=Ps,guard=G} = C1 = clause(C0, E, Ctxt, Sub),
%%ok = io:fwrite("~w: ~p~n", [?LINE,{E,Ps}]),
case {will_match(E, Ps),will_succeed(G)} of
{yes,yes} ->
case LitExpr of
false ->
Line = get_line(cerl:get_ann(C1)),
shadow_warning(Cs, Line);
true ->
%% If the case expression is a literal,
%% it is probably OK that some clauses don't match.
%% It is a probably some sort of debug macro.
ok
end,
[C1]; %Skip the rest
{_Mat,no} -> %Guard fails.
add_warning(C1, nomatch_guard),
clauses(E, Cs, Ctxt, Sub, LitExpr); %Skip this clause
{_Mat,_Suc} ->
[C1|clauses(E, Cs, Ctxt, Sub, LitExpr)]
end;
clauses(_, [], _, _, _) -> [].
shadow_warning([C|Cs], none) ->
add_warning(C, nomatch_shadow),
shadow_warning(Cs, none);
shadow_warning([C|Cs], Line) ->
add_warning(C, {nomatch_shadow, Line}),
shadow_warning(Cs, Line);
shadow_warning([], _) -> ok.
%% will_succeed(Guard) -> yes | maybe | no.
%% Test if we know whether a guard will succeed/fail or just don't
%% know. Be VERY conservative!
will_succeed(#c_literal{val=true}) -> yes;
will_succeed(#c_literal{val=false}) -> no;
will_succeed(_Guard) -> maybe.
%% will_match(Expr, [Pattern]) -> yes | maybe.
%% We KNOW that this function is only used after optimizations
%% in case_opt/4. Therefore clauses that can definitely not match
%% have already been pruned.
will_match(#c_values{es=Es}, Ps) ->
will_match_1(cerl_clauses:match_list(Ps, Es));
will_match(E, [P]) ->
will_match_1(cerl_clauses:match(P, E)).
will_match_1({false,_}) -> maybe;
will_match_1({true,_}) -> yes.
%% opt_bool_case(CoreExpr, Sub) - CoreExpr'.
%%
%% In bodies, do various optimizations to case statements that have
%% boolean case expressions. We don't do the optimizations in guards,
%% because they would thwart the optimization in v3_kernel.
%%
%% We start with some simple optimizations and normalization
%% to facilitate later optimizations.
%%
%% If the case expression can only return a boolean
%% (or fail), we can remove any clause that cannot
%% possibly match 'true' or 'false'. Also, any clause
%% following both 'true' and 'false' clause can
%% be removed. If successful, we will end up like this:
%%
%% case BoolExpr of case BoolExpr of
%% true -> false ->
%% ...; ...;
%% false -> OR true ->
%% ... ...
%% end. end.
%%
%% We give up if there are clauses with guards, or if there
%% is a variable clause that matches anything.
opt_bool_case(#c_case{}=Case, #sub{in_guard=true}) ->
%% v3_kernel does a better job without "help".
Case;
opt_bool_case(#c_case{arg=Arg}=Case0, #sub{in_guard=false}) ->
case is_bool_expr(Arg) of
false ->
Case0;
true ->
try opt_bool_clauses(Case0) of
Case ->
opt_bool_not(Case)
catch
impossible ->
Case0
end
end.
opt_bool_clauses(#c_case{clauses=Cs}=Case) ->
Case#c_case{clauses=opt_bool_clauses(Cs, false, false)}.
opt_bool_clauses(Cs, true, true) ->
%% We have now seen clauses that match both true and false.
%% Any remaining clauses cannot possibly match.
case Cs of
[_|_] ->
shadow_warning(Cs, none),
[];
[] ->
[]
end;
opt_bool_clauses([#c_clause{pats=[#c_literal{val=Lit}],
guard=#c_literal{val=true}}=C|Cs], SeenT, SeenF) ->
case is_boolean(Lit) of
false ->
%% Not a boolean - this clause can't match.
add_warning(C, nomatch_clause_type),
opt_bool_clauses(Cs, SeenT, SeenF);
true ->
%% This clause will match.
case {Lit,SeenT,SeenF} of
{false,_,false} ->
[C|opt_bool_clauses(Cs, SeenT, true)];
{true,false,_} ->
[C|opt_bool_clauses(Cs, true, SeenF)];
_ ->
add_warning(C, nomatch_shadow),
opt_bool_clauses(Cs, SeenT, SeenF)
end
end;
opt_bool_clauses([#c_clause{pats=Ps,guard=#c_literal{val=true}}=C|Cs], SeenT, SeenF) ->
case Ps of
[#c_var{}] ->
%% Will match a boolean.
throw(impossible);
[#c_alias{}] ->
%% Might match a boolean.
throw(impossible);
_ ->
%% The clause cannot possible match a boolean.
%% We can remove it.
add_warning(C, nomatch_clause_type),
opt_bool_clauses(Cs, SeenT, SeenF)
end;
opt_bool_clauses([_|_], _, _) ->
%% A clause with a guard. Give up.
throw(impossible).
%% We intentionally do not have a clause that match an empty
%% list. An empty list would indicate that the clauses do not
%% match all possible values for the case expression, which
%% means that the Core Erlang program is illegal. We prefer to
%% crash on such illegal input, rather than producing code that will
%% fail mysteriously at run time.
%% opt_bool_not(Case) -> CoreExpr.
%% Try to eliminate one or more calls to 'not' at the top level
%% of the case expression.
%%
%% We KNOW that the case expression is guaranteed to return
%% a boolean and that there are exactly two clauses: one that
%% matches 'true' and one that matches 'false'.
%%
%% case not Expr of case Expr of
%% true -> false ->
%% ...; ...;
%% false -> ==> true ->
%% ... ...;
%% end. NewVar ->
%% erlang:error(badarg)
%% end.
opt_bool_not(#c_case{arg=Arg,clauses=Cs0}=Case0) ->
case Arg of
#c_call{anno=Anno,module=#c_literal{val=erlang},
name=#c_literal{val='not'},
args=[Expr]} ->
Cs = [opt_bool_not_invert(C) || C <- Cs0] ++
[#c_clause{anno=[compiler_generated],
pats=[#c_var{name=cor_variable}],
guard=#c_literal{val=true},
body=#c_call{anno=Anno,
module=#c_literal{val=erlang},
name=#c_literal{val=error},
args=[#c_literal{val=badarg}]}}],
Case = Case0#c_case{arg=Expr,clauses=Cs},
opt_bool_not(Case);
_ ->
opt_bool_case_redundant(Case0)
end.
opt_bool_not_invert(#c_clause{pats=[#c_literal{val=Bool}]}=C) ->
C#c_clause{pats=[#c_literal{val=not Bool}]}.
%% opt_bool_case_redundant(Core) -> Core'.
%% If the sole purpose of the case is to verify that the case
%% expression is indeed boolean, we do not need the case
%% (since we have already verified that the case expression is
%% boolean).
%%
%% case BoolExpr of
%% true -> true ==> BoolExpr
%% false -> false
%% end.
%%
opt_bool_case_redundant(#c_case{arg=Arg,clauses=Cs}=Case) ->
case all(fun opt_bool_case_redundant_1/1, Cs) of
true -> Arg;
false -> opt_bool_case_guard(Case)
end.
opt_bool_case_redundant_1(#c_clause{pats=[#c_literal{val=B}],
body=#c_literal{val=B}}) ->
true;
opt_bool_case_redundant_1(_) -> false.
%% opt_bool_case_guard(Case) -> Case'.
%% Move a boolean case expression into the guard if we are sure that
%% it cannot fail.
%%
%% case SafeBoolExpr of case <> of
%% true -> TrueClause; ==> <> when SafeBoolExpr -> TrueClause;
%% false -> FalseClause <> when true -> FalseClause
%% end. end.
%%
%% Generally, evaluting a boolean expression in a guard should
%% be faster than evaulating it in the body.
%%
opt_bool_case_guard(#c_case{arg=#c_literal{}}=Case) ->
%% It is not necessary to move a literal case expression into the
%% guard, because it will be handled quite well in other
%% optimizations, and moving the literal into the guard will
%% cause some extra warnings, for instance for this code
%%
%% case true of
%% true -> ...;
%% false -> ...
%% end.
%%
Case;
opt_bool_case_guard(#c_case{arg=Arg,clauses=Cs0}=Case) ->
case is_safe_bool_expr(Arg, sub_new()) of
false ->
Case;
true ->
Cs = opt_bool_case_guard(Arg, Cs0),
Case#c_case{arg=#c_values{anno=cerl:get_ann(Arg),es=[]},
clauses=Cs}
end.
opt_bool_case_guard(Arg, [#c_clause{pats=[#c_literal{val=true}]}=Tc,Fc]) ->
[Tc#c_clause{pats=[],guard=Arg},Fc#c_clause{pats=[]}];
opt_bool_case_guard(Arg, [#c_clause{pats=[#c_literal{val=false}]}=Fc,Tc]) ->
[Tc#c_clause{pats=[],guard=Arg},Fc#c_clause{pats=[]}].
%% eval_case(Case) -> #c_case{} | #c_let{}.
%% If possible, evaluate a case at compile time. We know that the
%% last clause is guaranteed to match so if there is only one clause
%% with a pattern containing only variables then rewrite to a let.
eval_case(#c_case{arg=E,clauses=[#c_clause{pats=Ps0,
guard=#c_literal{val=true},
body=B}]}=Case, Sub) ->
Es = case cerl:is_c_values(E) of
true -> cerl:values_es(E);
false -> [E]
end,
%% Consider:
%%
%% case SomeSideEffect() of
%% X=Y -> ...
%% end
%%
%% We must not rewrite it to:
%%
%% let <X,Y> = <SomeSideEffect(),SomeSideEffect()> in ...
%%
%% because SomeSideEffect() would be evaluated twice.
%%
%% Instead we must evaluate the case expression in an outer let
%% like this:
%%
%% let NewVar = SomeSideEffect() in
%% let <X,Y> = <NewVar,NewVar> in ...
%%
Vs = make_vars([], length(Es)),
case cerl_clauses:match_list(Ps0, Vs) of
{false,_} ->
%% This can only happen if the Core Erlang code is
%% handwritten or generated by another code generator
%% than v3_core. Assuming that the Core Erlang program
%% is correct, the clause will always match at run-time.
Case;
{true,Bs} ->
eval_case_warn(B),
{Ps,As} = unzip(Bs),
InnerLet = cerl:c_let(Ps, core_lib:make_values(As), B),
Let = cerl:c_let(Vs, E, InnerLet),
expr(Let, sub_new(Sub))
end;
eval_case(Case, _) -> Case.
eval_case_warn(#c_primop{anno=Anno,
name=#c_literal{val=match_fail},
args=[_]}=Core) ->
case keyfind(eval_failure, 1, Anno) of
false ->
ok;
{eval_failure,Reason} ->
%% Example: M = not_map, M#{k:=v}
add_warning(Core, {eval_failure,Reason})
end;
eval_case_warn(_) -> ok.
%% case_opt(CaseArg, [Clause]) -> {CaseArg,[Clause]}.
%% Try and optimise a case by avoid building tuples or lists
%% in the case expression. Instead combine the variable parts
%% of the case expression to multiple "values". If a clause
%% refers to the constructed term in the case expression (which
%% was not built), introduce a let into the guard and/or body to
%% build the term.
%%
%% case {ok,[Expr1,Expr2]} of case <Expr1,Expr2> of
%% {ok,[P1,P2]} -> ... <P1,P2> -> ...
%% . ==> .
%% . .
%% . .
%% Var -> <Var1,Var2> ->
%% ... Var ... let <Var> = {ok,[Var1,Var2]}
%% in ... Var ...
%% . .
%% . .
%% . .
%% end. end.
%%
case_opt(Arg, Cs0, Sub) ->
Cs1 = [{cerl:clause_pats(C),C,[],[]} || C <- Cs0],
Args0 = case cerl:is_c_values(Arg) of
false -> [Arg];
true -> cerl:values_es(Arg)
end,
LitExpr = cerl:is_literal(Arg),
{Args,Cs2} = case_opt_args(Args0, Cs1, Sub, LitExpr, []),
Cs = [cerl:update_c_clause(C,
reverse(Ps),
letify(Bs, cerl:clause_guard(C)),
letify(Bs, cerl:clause_body(C))) ||
{[],C,Ps,Bs} <- Cs2],
{core_lib:make_values(Args),Cs}.
case_opt_args([A0|As0], Cs0, Sub, LitExpr, Acc) ->
case case_opt_arg(A0, Sub, Cs0, LitExpr) of
{error,Cs1} ->
%% Nothing to be done. Move on to the next argument.
Cs = [{Ps,C,[P|PsAcc],Bs} || {[P|Ps],C,PsAcc,Bs} <- Cs1],
case_opt_args(As0, Cs, Sub, LitExpr, [A0|Acc]);
{ok,As1,Cs} ->
%% The argument was either expanded (from tuple/list) or
%% removed (literal).
case_opt_args(As1++As0, Cs, Sub, LitExpr, Acc)
end;
case_opt_args([], Cs, _Sub, _LitExpr, Acc) ->
{reverse(Acc),Cs}.
%% case_opt_arg(Expr, Sub, Clauses0, LitExpr) ->
%% {ok,Args,Clauses} | error
%% Try to expand one argument to several arguments (if tuple/list)
%% or to remove a literal argument.
%%
case_opt_arg(E0, Sub, Cs, LitExpr) ->
case cerl:is_c_var(E0) of
false ->
case_opt_arg_1(E0, Cs, LitExpr);
true ->
case case_will_var_match(Cs) of
true ->
%% All clauses will match a variable in the
%% current position. Don't expand this variable
%% (that can only make the code worse).
{error,Cs};
false ->
%% If possible, expand this variable to a previously
%% matched term.
E = case_expand_var(E0, Sub),
case_opt_arg_1(E, Cs, LitExpr)
end
end.
case_opt_arg_1(E0, Cs0, LitExpr) ->
case cerl:is_data(E0) of
false ->
{error,Cs0};
true ->
E = case_opt_compiler_generated(E0),
Cs = case_opt_nomatch(E, Cs0, LitExpr),
case cerl:is_literal(E) of
true ->
case_opt_lit(E, Cs);
false ->
case_opt_data(E, Cs)
end
end.
%% case_will_var_match([Clause]) -> true | false.
%% Return if all clauses will match a variable in the
%% current position.
%%
case_will_var_match(Cs) ->
all(fun({[P|_],_,_,_}) ->
case cerl_clauses:match(P, any) of
{true,_} -> true;
_ -> false
end
end, Cs).
%% case_opt_compiler_generated(Core) -> Core'
%% Mark Core expressions as compiler generated to ensure that
%% no warnings are generated if they turn out to be unused.
%% To pretty-printed Core Erlang easier to read, don't mark
%% constructs that can't cause warnings to be emitted.
%%
case_opt_compiler_generated(Core) ->
F = fun(C) ->
case cerl:type(C) of
alias -> C;
var -> C;
_ -> cerl:set_ann(C, [compiler_generated])
end
end,
cerl_trees:map(F, Core).
%% case_expand_var(Expr0, Sub) -> Expr
%% If Expr0 is a variable that is known to be bound to a
%% constructed tuple, return the tuple instead. Otherwise
%% return Expr0 unchanged.
case_expand_var(E, #sub{t=Tdb}) ->
Key = cerl:var_name(E),
case Tdb of
#{Key:=T} ->
case cerl:is_c_tuple(T) of
false -> E;
true -> T
end;
_ ->
E
end.
%% case_opt_nomatch(E, Clauses, LitExpr) -> Clauses'
%% Remove all clauses that cannot possibly match.
case_opt_nomatch(E, [{[P|_],C,_,_}=Current|Cs], LitExpr) ->
case cerl_clauses:match(P, E) of
none ->
%% The pattern will not match the case expression. Remove
%% the clause. Unless the entire case expression is a
%% literal, also emit a warning.
case LitExpr of
false -> add_warning(C, nomatch_clause_type);
true -> ok
end,
case_opt_nomatch(E, Cs, LitExpr);
_ ->
[Current|case_opt_nomatch(E, Cs, LitExpr)]
end;
case_opt_nomatch(_, [], _) -> [].
%% case_opt_lit(Literal, Clauses0) -> {ok,[],Clauses} | error
%% The current part of the case expression is a literal. That
%% means that we will know at compile-time whether a clause
%% will match, and we can remove the corresponding pattern from
%% each clause.
%%
%% The only complication is if the literal is a binary or map.
%% In general, it is difficult to know whether a binary or
%% map pattern will match, so we give up in that case.
case_opt_lit(Lit, Cs0) ->
try case_opt_lit_1(Lit, Cs0) of
Cs ->
{ok,[],Cs}
catch
throw:impossible ->
{error,Cs0}
end.
case_opt_lit_1(E, [{[P|Ps],C,PsAcc,Bs0}|Cs]) ->
%% Non-matching clauses have already been removed
%% in case_opt_nomatch/3.
case cerl_clauses:match(P, E) of
{true,Bs} ->
%% The pattern matches the literal. Remove the pattern
%% and update the bindings.
[{Ps,C,PsAcc,Bs++Bs0}|case_opt_lit_1(E, Cs)];
{false,_} ->
%% Binary literal and pattern. We are not sure whether
%% the pattern will match.
throw(impossible)
end;
case_opt_lit_1(_, []) -> [].
%% case_opt_data(Expr, Clauses0, LitExpr) -> {ok,Exprs,Clauses}
%% The case expression is a non-atomic data constructor (cons
%% or tuple). We can know at compile time whether each clause
%% will match, and we can delay the building of the data to
%% the clauses where it is actually needed.
case_opt_data(E, Cs0) ->
TypeSig = {cerl:data_type(E),cerl:data_arity(E)},
try case_opt_data_1(Cs0, TypeSig) of
Cs ->
Es = cerl:data_es(E),
{ok,Es,Cs}
catch
throw:impossible ->
%% The pattern contained a binary or map.
{error,Cs0}
end.
case_opt_data_1([{[P0|Ps0],C,PsAcc,Bs0}|Cs], TypeSig) ->
P = case_opt_compiler_generated(P0),
{Ps1,Bs} = case_opt_data_2(P, TypeSig, Bs0),
[{Ps1++Ps0,C,PsAcc,Bs}|case_opt_data_1(Cs, TypeSig)];
case_opt_data_1([], _) -> [].
case_opt_data_2(P, TypeSig, Bs0) ->
case case_analyze_pat(P) of
{[],Pat} when Pat =/= none ->
DataEs = cerl:data_es(P),
{DataEs,Bs0};
{[V|Vs],none} ->
{Type,Arity} = TypeSig,
Ann = [compiler_generated],
Vars = make_vars(Ann, Arity),
Data = cerl:ann_make_data(Ann, Type, Vars),
Bs = [{V,Data} | [{Var,V} || Var <- Vs] ++ Bs0],
{Vars,Bs};
{[V|Vs],Pat} when Pat =/= none ->
{Type,_} = TypeSig,
DataEs = cerl:data_es(Pat),
Vars = pat_to_expr_list(DataEs),
Ann = [compiler_generated],
Data = cerl:ann_make_data(Ann, Type, Vars),
Bs = [{V,Data} | [{Var,V} || Var <- Vs] ++ Bs0],
{DataEs,Bs}
end.
case_analyze_pat(P) ->
case_analyze_pat_1(P, [], none).
case_analyze_pat_1(P, Vs, Pat) ->
case cerl:type(P) of
alias ->
V = cerl:alias_var(P),
Apat = cerl:alias_pat(P),
case_analyze_pat_1(Apat, [V|Vs], Pat);
var ->
{[P|Vs],Pat};
_ ->
{Vs,P}
end.
%% pat_to_expr(Pattern) -> Expression.
%% Convert a pattern to an expression if possible. We KNOW that
%% all variables in the pattern will be bound.
%%
%% Throw an 'impossible' exception if a map or (non-literal)
%% binary is encountered. Trying to use a map pattern as an
%% expression is incorrect, while rebuilding a potentially
%% huge binary in an expression would be wasteful.
pat_to_expr(P) ->
case cerl:type(P) of
alias ->
cerl:alias_var(P);
var ->
P;
_ ->
case cerl:is_data(P) of
false ->
%% Map or binary.
throw(impossible);
true ->
Es = pat_to_expr_list(cerl:data_es(P)),
cerl:update_data(P, cerl:data_type(P), Es)
end
end.
pat_to_expr_list(Ps) -> [pat_to_expr(P) || P <- Ps].
make_vars(A, Max) ->
make_vars(A, 1, Max).
make_vars(A, I, Max) when I =< Max ->
[make_var(A)|make_vars(A, I+1, Max)];
make_vars(_, _, _) -> [].
make_var(A) ->
#c_var{anno=A,name=make_var_name()}.
make_var_name() ->
N = get(new_var_num),
put(new_var_num, N+1),
N.
letify(Bs, Body) ->
Ann = cerl:get_ann(Body),
foldr(fun({V,Val}, B) ->
cerl:ann_c_let(Ann, [V], Val, B)
end, Body, Bs).
%% opt_not_in_let(Let) -> Cerl
%% Try to optimize away a 'not' operator in a 'let'.
-spec opt_not_in_let(cerl:c_let()) -> cerl:cerl().
opt_not_in_let(#c_let{vars=[_]=Vs0,arg=Arg0,body=Body0}=Let) ->
case opt_not_in_let_0(Vs0, Arg0, Body0) of
{[],#c_values{es=[]},Body} ->
Body;
{Vs,Arg,Body} ->
Let#c_let{vars=Vs,arg=Arg,body=Body}
end;
opt_not_in_let(Let) -> Let.
opt_not_in_let_0([#c_var{name=V}]=Vs0, Arg0, Body0) ->
case cerl:type(Body0) of
call ->
%% let <V> = Expr in not V ==>
%% let <> = <> in notExpr
case opt_not_in_let_1(V, Body0, Arg0) of
no ->
{Vs0,Arg0,Body0};
{yes,Body} ->
{[],#c_values{es=[]},Body}
end;
'let' ->
%% let <V> = Expr in let <Var> = not V in Body ==>
%% let <Var> = notExpr in Body
%% V must not be used in Body.
LetArg = cerl:let_arg(Body0),
case opt_not_in_let_1(V, LetArg, Arg0) of
no ->
{Vs0,Arg0,Body0};
{yes,Arg} ->
LetBody = cerl:let_body(Body0),
case core_lib:is_var_used(V, LetBody) of
true ->
{Vs0,Arg0,Body0};
false ->
LetVars = cerl:let_vars(Body0),
{LetVars,Arg,LetBody}
end
end;
_ ->
{Vs0,Arg0,Body0}
end.
opt_not_in_let_1(V, Call, Body) ->
case Call of
#c_call{module=#c_literal{val=erlang},
name=#c_literal{val='not'},
args=[#c_var{name=V}]} ->
opt_not_in_let_2(Body, Call);
_ ->
no
end.
opt_not_in_let_2(#c_case{clauses=Cs0}=Case, NotCall) ->
Vars = make_vars([], 1),
Body = NotCall#c_call{args=Vars},
Cs = [begin
Let = #c_let{vars=Vars,arg=B,body=Body},
C#c_clause{body=opt_not_in_let(Let)}
end || #c_clause{body=B}=C <- Cs0],
{yes,Case#c_case{clauses=Cs}};
opt_not_in_let_2(#c_call{}=Call0, _NotCall) ->
invert_call(Call0);
opt_not_in_let_2(_, _) -> no.
invert_call(#c_call{module=#c_literal{val=erlang},
name=#c_literal{val=Name0},
args=[_,_]}=Call) ->
case inverse_rel_op(Name0) of
no -> no;
Name -> {yes,Call#c_call{name=#c_literal{val=Name}}}
end;
invert_call(#c_call{}) -> no.
%% inverse_rel_op(Op) -> no | RevOp
inverse_rel_op('=:=') -> '=/=';
inverse_rel_op('=/=') -> '=:=';
inverse_rel_op('==') -> '/=';
inverse_rel_op('/=') -> '==';
inverse_rel_op('>') -> '=<';
inverse_rel_op('<') -> '>=';
inverse_rel_op('>=') -> '<';
inverse_rel_op('=<') -> '>';
inverse_rel_op(_) -> no.
%% opt_bool_case_in_let(LetExpr) -> Core
opt_bool_case_in_let(#c_let{vars=Vs,arg=Arg,body=B}=Let, Sub) ->
opt_bool_case_in_let_1(Vs, Arg, B, Let, Sub).
opt_bool_case_in_let_1([#c_var{name=V}], Arg,
#c_case{arg=#c_var{name=V}}=Case0, Let, Sub) ->
case is_simple_case_arg(Arg) of
true ->
Case = opt_bool_case(Case0#c_case{arg=Arg}, Sub),
case core_lib:is_var_used(V, Case) of
false -> Case;
true -> Let
end;
false ->
Let
end;
opt_bool_case_in_let_1(_, _, _, Let, _) -> Let.
%% is_simple_case_arg(Expr) -> true|false
%% Determine whether the Expr is simple enough to be worth
%% substituting into a case argument. (Common substitutions
%% of variables and literals are assumed to have been already
%% handled by the caller.)
is_simple_case_arg(#c_cons{}) -> true;
is_simple_case_arg(#c_tuple{}) -> true;
is_simple_case_arg(#c_call{}) -> true;
is_simple_case_arg(#c_apply{}) -> true;
is_simple_case_arg(_) -> false.
%% is_bool_expr(Core) -> true|false
%% Check whether the Core expression is guaranteed to return
%% a boolean IF IT RETURNS AT ALL.
%%
is_bool_expr(Core) ->
is_bool_expr(Core, sub_new()).
%% is_bool_expr(Core, Sub) -> true|false
%% Check whether the Core expression is guaranteed to return
%% a boolean IF IT RETURNS AT ALL. Uses type information
%% to be able to identify more expressions as booleans.
%%
is_bool_expr(#c_call{module=#c_literal{val=erlang},
name=#c_literal{val=Name},args=Args}=Call, _) ->
NumArgs = length(Args),
erl_internal:comp_op(Name, NumArgs) orelse
erl_internal:new_type_test(Name, NumArgs) orelse
erl_internal:bool_op(Name, NumArgs) orelse
will_fail(Call);
is_bool_expr(#c_try{arg=E,vars=[#c_var{name=X}],body=#c_var{name=X},
handler=#c_literal{val=false}}, Sub) ->
is_bool_expr(E, Sub);
is_bool_expr(#c_case{clauses=Cs}, Sub) ->
is_bool_expr_list(Cs, Sub);
is_bool_expr(#c_clause{body=B}, Sub) ->
is_bool_expr(B, Sub);
is_bool_expr(#c_let{vars=[V],arg=Arg,body=B}, Sub0) ->
Sub = case is_bool_expr(Arg, Sub0) of
true -> update_types(V, [bool], Sub0);
false -> Sub0
end,
is_bool_expr(B, Sub);
is_bool_expr(#c_let{body=B}, Sub) ->
%% Binding of multiple variables.
is_bool_expr(B, Sub);
is_bool_expr(C, Sub) ->
is_boolean_type(C, Sub) =:= yes.
is_bool_expr_list([C|Cs], Sub) ->
is_bool_expr(C, Sub) andalso is_bool_expr_list(Cs, Sub);
is_bool_expr_list([], _) -> true.
%% is_safe_bool_expr(Core) -> true|false
%% Check whether the Core expression ALWAYS returns a boolean
%% (i.e. it cannot fail). Also make sure that the expression
%% is suitable for a guard (no calls to non-guard BIFs, local
%% functions, or is_record/2).
%%
is_safe_bool_expr(Core, Sub) ->
is_safe_bool_expr_1(Core, Sub, cerl_sets:new()).
is_safe_bool_expr_1(#c_call{module=#c_literal{val=erlang},
name=#c_literal{val=is_record},
args=[A,#c_literal{val=Tag},#c_literal{val=Size}]},
Sub, _BoolVars) when is_atom(Tag), is_integer(Size) ->
is_safe_simple(A, Sub);
is_safe_bool_expr_1(#c_call{module=#c_literal{val=erlang},
name=#c_literal{val=is_record}},
_Sub, _BoolVars) ->
%% The is_record/2 BIF is NOT allowed in guards.
%% The is_record/3 BIF where its second argument is not an atom or its third
%% is not an integer is NOT allowed in guards.
%%
%% NOTE: Calls like is_record(Expr, LiteralTag), where LiteralTag
%% is a literal atom referring to a defined record, have already
%% been rewritten to is_record(Expr, LiteralTag, TupleSize).
false;
is_safe_bool_expr_1(#c_call{module=#c_literal{val=erlang},
name=#c_literal{val=is_function},
args=[A,#c_literal{val=Arity}]},
Sub, _BoolVars) when is_integer(Arity), Arity >= 0 ->
is_safe_simple(A, Sub);
is_safe_bool_expr_1(#c_call{module=#c_literal{val=erlang},
name=#c_literal{val=is_function}},
_Sub, _BoolVars) ->
false;
is_safe_bool_expr_1(#c_call{module=#c_literal{val=erlang},
name=#c_literal{val=Name},args=Args},
Sub, BoolVars) ->
NumArgs = length(Args),
case (erl_internal:comp_op(Name, NumArgs) orelse
erl_internal:new_type_test(Name, NumArgs)) andalso
is_safe_simple_list(Args, Sub) of
true ->
true;
false ->
%% Boolean operators are safe if all arguments are boolean.
erl_internal:bool_op(Name, NumArgs) andalso
is_safe_bool_expr_list(Args, Sub, BoolVars)
end;
is_safe_bool_expr_1(#c_let{vars=Vars,arg=Arg,body=B}, Sub, BoolVars) ->
case is_safe_simple(Arg, Sub) of
true ->
case {is_safe_bool_expr_1(Arg, Sub, BoolVars),Vars} of
{true,[#c_var{name=V}]} ->
is_safe_bool_expr_1(B, Sub, cerl_sets:add_element(V, BoolVars));
{false,_} ->
is_safe_bool_expr_1(B, Sub, BoolVars)
end;
false -> false
end;
is_safe_bool_expr_1(#c_literal{val=Val}, _Sub, _) ->
is_boolean(Val);
is_safe_bool_expr_1(#c_var{name=V}, _Sub, BoolVars) ->
cerl_sets:is_element(V, BoolVars);
is_safe_bool_expr_1(_, _, _) -> false.
is_safe_bool_expr_list([C|Cs], Sub, BoolVars) ->
case is_safe_bool_expr_1(C, Sub, BoolVars) of
true -> is_safe_bool_expr_list(Cs, Sub, BoolVars);
false -> false
end;
is_safe_bool_expr_list([], _, _) -> true.
%% 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
%% expression.
simplify_let(#c_let{arg=Arg}=Let, Sub) ->
move_let_into_expr(Let, Arg, Sub).
move_let_into_expr(#c_let{vars=InnerVs0,body=InnerBody0}=Inner,
#c_let{vars=OuterVs0,arg=Arg0,body=OuterBody0}=Outer, Sub0) ->
%%
%% let <InnerVars> = let <OuterVars> = <Arg>
%% in <OuterBody>
%% in <InnerBody>
%%
%% ==>
%%
%% let <OuterVars> = <Arg>
%% in let <InnerVars> = <OuterBody>
%% in <InnerBody>
%%
Arg = body(Arg0, Sub0),
ScopeSub0 = sub_subst_scope(Sub0#sub{t=#{}}),
{OuterVs,ScopeSub} = var_list(OuterVs0, ScopeSub0),
OuterBody = body(OuterBody0, ScopeSub),
{InnerVs,Sub} = var_list(InnerVs0, Sub0),
InnerBody = body(InnerBody0, Sub),
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|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(...)
%% end
%% in <Let-body>
%%
%% ==>
%%
%% case <Case-expr> of
%% <Cpats> ->
%% let <Lvars> = <Clause-body>
%% in <Let-body>;
%% <OtherCpats> -> erlang:error(...)
%% end
Cexpr = body(Cexpr0, Sub0),
CaPats0 = Ca0#c_clause.pats,
G0 = Ca0#c_clause.guard,
B0 = Ca0#c_clause.body,
ScopeSub0 = sub_subst_scope(Sub0#sub{t=#{}}),
try pattern_list(CaPats0, ScopeSub0) of
{CaPats,ScopeSub} ->
G = guard(G0, ScopeSub),
B1 = body(B0, ScopeSub),
{Lvs,B2,Sub1} = let_substs(Lvs0, B1, Sub0),
Sub2 = Sub1#sub{s=cerl_sets:union(ScopeSub#sub.s,
Sub1#sub.s)},
Lbody = body(Lbody0, Sub2),
B = Let#c_let{vars=Lvs,
arg=core_lib:make_values(B2),
body=Lbody},
Ca = Ca0#c_clause{pats=CaPats,guard=G,body=B},
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
%% be optimized to erlang:error(...) by the other
%% optimizations done in this module.
impossible
end;
false -> impossible
end;
move_let_into_expr(#c_let{vars=Lvs0,body=Lbody0}=Let,
#c_seq{arg=Sarg0,body=Sbody0}=Seq, Sub0) ->
%%
%% let <Lvars> = do <Seq-arg>
%% <Seq-body>
%% in <Let-body>
%%
%% ==>
%%
%% do <Seq-arg>
%% let <Lvars> = <Seq-body>
%% in <Let-body>
%%
Sarg = body(Sarg0, Sub0),
Sbody1 = body(Sbody0, Sub0),
{Lvs,Sbody,Sub} = let_substs(Lvs0, Sbody1, Sub0),
Lbody = body(Lbody0, Sub),
Seq#c_seq{arg=Sarg,body=Let#c_let{vars=Lvs,arg=core_lib:make_values(Sbody),
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:
%%
%% {V1,V2,...} = case E of P -> ... {Val1,Val2,...}; ... end
%%
%% In Core Erlang the pattern would look like this:
%%
%% let <V> = case E of
%% ... -> ... {Val1,Val2}
%% ...
%% end,
%% in case V of
%% {A,B} -> ... <use A and B> ...
%% end
%%
%% Rewrite this to:
%%
%% let <V1,V2> = case E of
%% ... -> ... <Val1,Val2>
%% ...
%% end,
%% in
%% let <V> = {V1,V2}
%% in case V of
%% {A,B} -> ... <use A and B> ...
%% end
%%
%% Note that the second 'case' is unchanged. The other optimizations
%% in this module will eliminate the building of the tuple and
%% rewrite the second case to:
%%
%% case <V1,V2> of
%% <A,B> -> ... <use A and B> ...
%% end
%%
opt_case_in_let(#c_let{vars=Vs,arg=Arg0,body=B}=Let0) ->
case matches_data(Vs, B) of
{yes,TypeSig} ->
case delay_build(Arg0, TypeSig) of
no ->
Let0;
{yes,Vars,Arg,Data} ->
InnerLet = Let0#c_let{arg=Data},
Let0#c_let{vars=Vars,arg=Arg,body=InnerLet}
end;
no ->
Let0
end.
matches_data([#c_var{name=V}], #c_case{arg=#c_var{name=V},
clauses=[#c_clause{pats=[P]}|_]}) ->
case cerl:is_data(P) of
false ->
no;
true ->
case cerl:data_type(P) of
{atomic,_} ->
no;
Type ->
{yes,{Type,cerl:data_arity(P)}}
end
end;
matches_data(_, _) -> no.
delay_build(Core, TypeSig) ->
case cerl:is_data(Core) of
true -> no;
false -> delay_build_1(Core, TypeSig)
end.
delay_build_1(Core0, TypeSig) ->
try delay_build_expr(Core0, TypeSig) of
Core ->
{Type,Arity} = TypeSig,
Ann = [compiler_generated],
Vars = make_vars(Ann, Arity),
Data = cerl:ann_make_data(Ann, Type, Vars),
{yes,Vars,Core,Data}
catch
throw:impossible ->
no
end.
delay_build_cs([#c_clause{body=B0}=C0|Cs], TypeSig) ->
B = delay_build_expr(B0, TypeSig),
C = C0#c_clause{body=B},
[C|delay_build_cs(Cs, TypeSig)];
delay_build_cs([], _) -> [].
delay_build_expr(Core, {Type,Arity}=TypeSig) ->
case cerl:is_data(Core) of
false ->
delay_build_expr_1(Core, TypeSig);
true ->
case {cerl:data_type(Core),cerl:data_arity(Core)} of
{Type,Arity} ->
core_lib:make_values(cerl:data_es(Core));
{_,_} ->
throw(impossible)
end
end.
delay_build_expr_1(#c_case{clauses=Cs0}=Case, TypeSig) ->
Cs = delay_build_cs(Cs0, TypeSig),
Case#c_case{clauses=Cs};
delay_build_expr_1(#c_let{body=B0}=Let, TypeSig) ->
B = delay_build_expr(B0, TypeSig),
Let#c_let{body=B};
delay_build_expr_1(#c_receive{clauses=Cs0,
timeout=Timeout,
action=A0}=Rec, TypeSig) ->
Cs = delay_build_cs(Cs0, 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) ->
B = delay_build_expr(B0, TypeSig),
Seq#c_seq{body=B};
delay_build_expr_1(Core, _TypeSig) ->
case will_fail(Core) of
true -> Core;
false -> throw(impossible)
end.
%% opt_simple_let(#c_let{}, Context, Sub) -> CoreTerm
%% Optimize a let construct that does not contain any lets in
%% in its argument.
opt_simple_let(Let0, Ctxt, Sub) ->
case opt_not_in_let(Let0) of
#c_let{}=Let ->
opt_simple_let_0(Let, Ctxt, Sub);
Expr ->
expr(Expr, Ctxt, Sub)
end.
opt_simple_let_0(#c_let{arg=Arg0}=Let, Ctxt, Sub) ->
Arg = body(Arg0, value, Sub), %This is a body
case will_fail(Arg) of
true -> Arg;
false -> opt_simple_let_1(Let, Arg, Ctxt, Sub)
end.
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, 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=V}],Arg1,#c_var{name=V}} ->
%% let <Var> = Arg in <Var> ==> Arg
Arg1;
{[],#c_values{es=[]},_} ->
%% No variables left.
Body;
{[#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.
%% 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:
%%
%% R = #r{}, %No warning expected.
%% R#r.f %Optimization would remove the reference to R.
%%
%% To avoid false warnings, we will check whether the variables were
%% referenced in the original unoptimized code. If they were, we will
%% consider the warning false and suppress it.
maybe_suppress_warnings(Arg, #c_var{name=V}, PrevBody) ->
case should_suppress_warning(Arg) of
true ->
Arg; %Already suppressed.
false ->
case core_lib:is_var_used(V, PrevBody) of
true ->
suppress_warning([Arg]);
false ->
Arg
end
end.
%% Suppress warnings for a Core Erlang expression whose value will
%% be ignored.
suppress_warning([H|T]) ->
case cerl:is_literal(H) of
true ->
suppress_warning(T);
false ->
case cerl:is_data(H) of
true ->
suppress_warning(cerl:data_es(H) ++ T);
false ->
%% Some other thing, such as a function call.
%% This cannot be the compiler's fault, so the
%% warning should not be suppressed. We must
%% be careful not to destroy tail-recursion.
case T of
[] ->
H;
[_|_] ->
cerl:c_seq(H, suppress_warning(T))
end
end
end;
suppress_warning([]) -> void().
move_case_into_arg(#c_case{arg=#c_let{vars=OuterVars0,arg=OuterArg,
body=InnerArg0}=Outer,
clauses=InnerClauses}=Inner, Sub) ->
%%
%% case let <OuterVars> = <OuterArg> in <InnerArg> of
%% <InnerClauses>
%% end
%%
%% ==>
%%
%% let <OuterVars> = <OuterArg>
%% in case <InnerArg> of <InnerClauses> end
%%
ScopeSub0 = sub_subst_scope(Sub#sub{t=#{}}),
{OuterVars,ScopeSub} = var_list(OuterVars0, ScopeSub0),
InnerArg = body(InnerArg0, ScopeSub),
Outer#c_let{vars=OuterVars,arg=OuterArg,
body=Inner#c_case{arg=InnerArg,clauses=InnerClauses}};
move_case_into_arg(#c_case{arg=#c_case{arg=OuterArg,
clauses=[OuterCa0,OuterCb]}=Outer,
clauses=InnerClauses}=Inner0, Sub) ->
case is_failing_clause(OuterCb) of
true ->
#c_clause{pats=OuterPats0,guard=OuterGuard0,
body=InnerArg0} = OuterCa0,
%%
%% case case <OuterArg> of
%% <OuterPats> when <OuterGuard> -> <InnerArg>
%% <OuterCb>
%% ...
%% end of
%% <InnerClauses>
%% end
%%
%% ==>
%%
%% case <OuterArg> of
%% <OuterPats> when <OuterGuard> ->
%% case <InnerArg> of <InnerClauses> end
%% <OuterCb>
%% end
%%
ScopeSub0 = sub_subst_scope(Sub#sub{t=#{}}),
%% We KNOW that pattern_list/2 has already been called for OuterPats0;
%% therefore, it cannot throw an exception.
{OuterPats,ScopeSub} = pattern_list(OuterPats0, ScopeSub0),
OuterGuard = guard(OuterGuard0, ScopeSub),
InnerArg = body(InnerArg0, ScopeSub),
Inner = Inner0#c_case{arg=InnerArg,clauses=InnerClauses},
OuterCa = OuterCa0#c_clause{pats=OuterPats,
guard=OuterGuard,
body=Inner},
Outer#c_case{arg=OuterArg,
clauses=[OuterCa,OuterCb]};
false ->
Inner0
end;
move_case_into_arg(#c_case{arg=#c_seq{arg=OuterArg,body=InnerArg}=Outer,
clauses=InnerClauses}=Inner, _Sub) ->
%%
%% case do <OuterArg> <InnerArg> of
%% <InnerClauses>
%% end
%%
%% ==>
%%
%% do <OuterArg>
%% case <InnerArg> of <InerClauses> end
%%
Outer#c_seq{arg=OuterArg,
body=Inner#c_case{arg=InnerArg,clauses=InnerClauses}};
move_case_into_arg(Expr, _) ->
Expr.
%%%
%%% Retrieving information about types.
%%%
-spec get_type(cerl:cerl(), #sub{}) -> type_info() | 'none'.
get_type(#c_var{name=V}, #sub{t=Tdb}) ->
case Tdb of
#{V:=Type} -> Type;
_ -> none
end;
get_type(C, _) ->
case cerl:type(C) of
binary -> C;
map -> C;
_ ->
case cerl:is_data(C) of
true -> C;
false -> none
end
end.
-spec is_boolean_type(cerl:cerl(), sub()) -> yes_no_maybe().
is_boolean_type(Var, Sub) ->
case get_type(Var, Sub) of
none ->
maybe;
bool ->
yes;
C ->
B = cerl:is_c_atom(C) andalso
is_boolean(cerl:atom_val(C)),
yes_no(B)
end.
-spec is_int_type(cerl:cerl(), sub()) -> yes_no_maybe().
is_int_type(Var, Sub) ->
case get_type(Var, Sub) of
none -> maybe;
integer -> yes;
C -> yes_no(cerl:is_c_int(C))
end.
yes_no(true) -> yes;
yes_no(false) -> no.
%%%
%%% Update type information.
%%%
update_let_types(Vs, Args, Sub) when is_list(Args) ->
update_let_types_1(Vs, Args, Sub);
update_let_types(_Vs, _Arg, Sub) ->
%% The argument is a complex expression (such as a 'case')
%% that returns multiple values.
Sub.
update_let_types_1([#c_var{}=V|Vs], [A|As], Sub0) ->
Sub = update_types_from_expr(V, A, Sub0),
update_let_types_1(Vs, As, Sub);
update_let_types_1([], [], Sub) -> Sub.
update_types_from_expr(V, Expr, Sub) ->
Type = extract_type(Expr, Sub),
update_types(V, [Type], Sub).
extract_type(#c_call{module=#c_literal{val=erlang},
name=#c_literal{val=Name},
args=Args}=Call, Sub) ->
case returns_integer(Name, Args) of
true -> integer;
false -> extract_type_1(Call, Sub)
end;
extract_type(Expr, Sub) ->
extract_type_1(Expr, Sub).
extract_type_1(Expr, Sub) ->
case is_bool_expr(Expr, Sub) of
false -> Expr;
true -> bool
end.
returns_integer('band', [_,_]) -> true;
returns_integer('bnot', [_]) -> true;
returns_integer('bor', [_,_]) -> true;
returns_integer('bxor', [_,_]) -> true;
returns_integer(bit_size, [_]) -> true;
returns_integer('bsl', [_,_]) -> true;
returns_integer('bsr', [_,_]) -> true;
returns_integer(byte_size, [_]) -> true;
returns_integer(ceil, [_]) -> true;
returns_integer('div', [_,_]) -> true;
returns_integer(floor, [_]) -> true;
returns_integer(length, [_]) -> true;
returns_integer('rem', [_,_]) -> true;
returns_integer('round', [_]) -> true;
returns_integer(size, [_]) -> true;
returns_integer(tuple_size, [_]) -> true;
returns_integer(trunc, [_]) -> true;
returns_integer(_, _) -> false.
%% update_types(Expr, Pattern, Sub) -> Sub'
%% Update the type database.
-spec update_types(cerl:c_var(), [type_info()], sub()) -> sub().
update_types(#c_var{name=V}, Pat, #sub{t=Tdb0}=Sub) ->
Tdb = update_types_1(V, Pat, Tdb0),
Sub#sub{t=Tdb}.
update_types_1(V, [#c_tuple{}=P], Types) ->
Types#{V=>P};
update_types_1(V, [#c_literal{val=Bool}], Types) when is_boolean(Bool) ->
Types#{V=>bool};
update_types_1(V, [#c_fun{vars=Vars}], Types) ->
Types#{V=>{'fun',length(Vars)}};
update_types_1(V, [#c_var{name={_,Arity}}], Types) ->
Types#{V=>{'fun',Arity}};
update_types_1(V, [Type], Types) when is_atom(Type) ->
Types#{V=>Type};
update_types_1(_, _, Types) -> Types.
%% kill_types(V, Tdb) -> Tdb'
%% Kill any entries that references the variable,
%% either in the key or in the value.
kill_types(V, Tdb) ->
maps:from_list(kill_types2(V,maps:to_list(Tdb))).
kill_types2(V, [{V,_}|Tdb]) ->
kill_types2(V, Tdb);
kill_types2(V, [{_,#c_tuple{}=Tuple}=Entry|Tdb]) ->
case core_lib:is_var_used(V, Tuple) of
false -> [Entry|kill_types2(V, Tdb)];
true -> kill_types2(V, Tdb)
end;
kill_types2(V, [{_, {'fun',_}}=Entry|Tdb]) ->
[Entry|kill_types2(V, Tdb)];
kill_types2(V, [{_,Atom}=Entry|Tdb]) when is_atom(Atom) ->
[Entry|kill_types2(V, Tdb)];
kill_types2(_, []) -> [].
%% copy_type(DestVar, SrcVar, Tdb) -> Tdb'
%% If the SrcVar has a type, assign it to DestVar.
%%
copy_type(V, #c_var{name=Src}, Tdb) ->
case Tdb of
#{Src:=Type} -> Tdb#{V=>Type};
_ -> Tdb
end;
copy_type(_, _, Tdb) -> Tdb.
%% The atom `ok', is widely used in Erlang for "void" values.
void() -> #c_literal{val=ok}.
%%%
%%% Handling of warnings.
%%%
init_warnings() ->
put({?MODULE,warnings}, []).
add_warning(Core, Term) ->
case should_suppress_warning(Core) of
true ->
ok;
false ->
Anno = cerl:get_ann(Core),
Line = get_line(Anno),
File = get_file(Anno),
Key = {?MODULE,warnings},
case get(Key) of
[{File,[{Line,?MODULE,Term}]}|_] ->
ok; %We already have
%an identical warning.
Ws ->
put(Key, [{File,[{Line,?MODULE,Term}]}|Ws])
end
end.
get_line([Line|_]) when is_integer(Line) -> Line;
get_line([_|T]) -> get_line(T);
get_line([]) -> none.
get_file([{file,File}|_]) -> File;
get_file([_|T]) -> get_file(T);
get_file([]) -> "no_file". % should not happen
should_suppress_warning(Core) ->
is_compiler_generated(Core) orelse
is_result_unwanted(Core).
is_compiler_generated(Core) ->
Ann = cerl:get_ann(Core),
member(compiler_generated, Ann).
is_result_unwanted(Core) ->
Ann = cerl:get_ann(Core),
member(result_not_wanted, Ann).
get_warnings() ->
ordsets:from_list((erase({?MODULE,warnings}))).
-type error() :: 'bad_unicode' | 'bin_argument_order'
| 'bin_left_var_used_in_guard' | 'bin_opt_alias'
| 'bin_partition' | 'bin_var_used' | 'bin_var_used_in_guard'
| 'embedded_binary_size' | 'nomatch_clause_type'
| 'nomatch_guard' | 'nomatch_shadow' | 'no_clause_match'
| 'orig_bin_var_used_in_guard' | 'result_ignored'
| 'useless_building'
| {'eval_failure', term()}
| {'no_effect', {'erlang',atom(),arity()}}
| {'nomatch_shadow', integer()}
| {'embedded_unit', _, _}.
-spec format_error(error()) -> nonempty_string().
format_error({eval_failure,Reason}) ->
flatten(io_lib:format("this expression will fail with a '~p' exception", [Reason]));
format_error(embedded_binary_size) ->
"binary construction will fail with a 'badarg' exception "
"(field size for binary/bitstring greater than actual size)";
format_error({embedded_unit,Unit,Size}) ->
M = io_lib:format("binary construction will fail with a 'badarg' exception "
"(size ~p cannot be evenly divided by unit ~p)", [Size,Unit]),
flatten(M);
format_error(bad_unicode) ->
"binary construction will fail with a 'badarg' exception "
"(invalid Unicode code point in a utf8/utf16/utf32 segment)";
format_error({nomatch_shadow,Line}) ->
M = io_lib:format("this clause cannot match because a previous clause at line ~p "
"always matches", [Line]),
flatten(M);
format_error(nomatch_shadow) ->
"this clause cannot match because a previous clause always matches";
format_error(nomatch_guard) ->
"the guard for this clause evaluates to 'false'";
format_error({nomatch_bit_syntax_truncated,Signess,Val,Sz}) ->
S = case Signess of
signed -> "a 'signed'";
unsigned -> "an 'unsigned'"
end,
F = "this clause cannot match because the value ~P"
" will not fit in ~s binary segment of size ~p",
flatten(io_lib:format(F, [Val,10,S,Sz]));
format_error({nomatch_bit_syntax_unsigned,Val}) ->
F = "this clause cannot match because the negative value ~P"
" will never match the value of an 'unsigned' binary segment",
flatten(io_lib:format(F, [Val,10]));
format_error({nomatch_bit_syntax_size,Sz}) ->
F = "this clause cannot match because '~P' is not a valid size for a binary segment",
flatten(io_lib:format(F, [Sz,10]));
format_error({nomatch_bit_syntax_type,Val,Type}) ->
F = "this clause cannot match because '~P' is not of the"
" expected type '~p'",
flatten(io_lib:format(F, [Val,10,Type]));
format_error({nomatch_bit_syntax_unicode,Val}) ->
F = "this clause cannot match because the value ~p"
" is not a valid Unicode code point",
flatten(io_lib:format(F, [Val]));
format_error(no_clause_match) ->
"no clause will ever match";
format_error(nomatch_clause_type) ->
"this clause cannot match because of different types/sizes";
format_error({no_effect,{erlang,F,A}}) ->
{Fmt,Args} = case erl_internal:comp_op(F, A) of
true ->
{"use of operator ~p has no effect",[F]};
false ->
case erl_internal:bif(F, A) of
false ->
{"the call to erlang:~p/~p has no effect",[F,A]};
true ->
{"the call to ~p/~p has no effect",[F,A]}
end
end,
flatten(io_lib:format(Fmt, Args));
format_error(result_ignored) ->
"the result of the expression is ignored "
"(suppress the warning by assigning the expression to the _ variable)";
format_error(invalid_call) ->
"invalid function call";
format_error(useless_building) ->
"a term is constructed, but never used".
-ifdef(DEBUG).
%% In order for simplify_let/2 to work correctly, the list of
%% in-scope variables must always be a superset of the free variables
%% in the current expression (otherwise we might fail to rename a variable
%% when needed and get a name capture bug).
verify_scope(E, #sub{s=Scope}) ->
Free0 = cerl_trees:free_variables(E),
Free = [V || V <- Free0, not is_tuple(V)], %Ignore function names.
case is_subset_of_scope(Free, Scope) of
true ->
true;
false ->
io:format("~p\n", [E]),
io:format("~p\n", [Free]),
io:format("~p\n", [ordsets:from_list(cerl_sets:to_list(Scope))]),
false
end.
is_subset_of_scope([V|Vs], Scope) ->
cerl_sets:is_element(V, Scope) andalso is_subset_of_scope(Vs, Scope);
is_subset_of_scope([], _) -> true.
-endif.
