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-rw-r--r--lib/compiler/src/sys_core_fold.erl88
-rw-r--r--lib/compiler/test/warnings_SUITE.erl26
2 files changed, 93 insertions, 21 deletions
diff --git a/lib/compiler/src/sys_core_fold.erl b/lib/compiler/src/sys_core_fold.erl
index ea1959d0f8..f0f58c767d 100644
--- a/lib/compiler/src/sys_core_fold.erl
+++ b/lib/compiler/src/sys_core_fold.erl
@@ -2036,7 +2036,7 @@ 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, [#c_literal{val=true}], Sub0);
+ true -> update_types(V, [bool], Sub0);
false -> Sub0
end,
is_bool_expr(B, Sub);
@@ -2272,36 +2272,29 @@ opt_simple_let(#c_let{arg=Arg0}=Let, Ctxt, Sub0) ->
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 = case {Vs,Args} of
- {[V],[A]} ->
- case is_bool_expr(A, Sub0) of
- true ->
- update_types(V, [#c_literal{val=true}], Sub1);
- false ->
- Sub1
- end;
- {_,_} -> Sub1
- end,
+ BodySub = update_let_types(Vs, Args, Sub1),
B = body(B0, Ctxt, BodySub),
Arg = core_lib:make_values(Args),
- opt_simple_let_2(Let, Vs, Arg, B, Ctxt, Sub1).
+ opt_simple_let_2(Let, Vs, Arg, B, B0, Ctxt, Sub1).
-opt_simple_let_2(Let0, Vs0, Arg0, Body, Ctxt, Sub) ->
+opt_simple_let_2(Let0, Vs0, Arg0, Body, PrevBody, Ctxt, Sub) ->
case {Vs0,Arg0,Body} of
- {[#c_var{name=N1}],Arg,#c_var{name=N2}} ->
+ {[#c_var{name=N1}],Arg1,#c_var{name=N2}} ->
case N1 =:= N2 of
true ->
%% let <Var> = Arg in <Var> ==> Arg
- Arg;
+ Arg1;
false ->
%% let <Var> = Arg in <OtherVar> ==> seq Arg OtherVar
+ Arg = maybe_suppress_warnings(Arg1, Vs0, PrevBody, Ctxt),
expr(#c_seq{arg=Arg,body=Body}, Ctxt,
sub_new_preserve_types(Sub))
end;
{[],#c_values{es=[]},_} ->
%% No variables left.
Body;
- {_,Arg,#c_literal{}} ->
+ {Vs,Arg1,#c_literal{}} ->
+ Arg = maybe_suppress_warnings(Arg1, Vs, PrevBody, Ctxt),
E = case Ctxt of
effect ->
%% Throw away the literal body.
@@ -2313,22 +2306,50 @@ opt_simple_let_2(Let0, Vs0, Arg0, Body, Ctxt, Sub) ->
#c_seq{arg=Arg,body=Body}
end,
expr(E, Ctxt, sub_new_preserve_types(Sub));
- {Vs,Arg,Body} ->
+ {Vs,Arg1,Body} ->
%% If none of the variables are used in the body, we can
%% rewrite the let to a sequence:
%% let <Var> = Arg in BodyWithoutVar ==>
%% seq Arg BodyWithoutVar
case is_any_var_used(Vs, Body) of
false ->
+ Arg = maybe_suppress_warnings(Arg1, Vs, PrevBody, Ctxt),
expr(#c_seq{arg=Arg,body=Body}, Ctxt,
sub_new_preserve_types(Sub));
true ->
- Let1 = Let0#c_let{vars=Vs,arg=Arg,body=Body},
+ Let1 = Let0#c_let{vars=Vs,arg=Arg1,body=Body},
Let2 = opt_case_in_let(Let1, Sub),
opt_case_in_let_arg(Let2, Ctxt, Sub)
end
end.
+%% maybe_suppress_warnings(Arg, [#c_var{}], PreviousBody, Context) -> 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, _, _, effect) ->
+ %% Don't suppress any warnings in effect context.
+ Arg;
+maybe_suppress_warnings(Arg, Vs, PrevBody, value) ->
+ case suppress_warning(Arg) of
+ true ->
+ Arg; %Already suppressed.
+ false ->
+ case is_any_var_used(Vs, PrevBody) of
+ true ->
+ cerl:set_ann(Arg, [compiler_generated]);
+ false ->
+ Arg
+ end
+ end.
+
move_case_into_arg(#c_case{arg=#c_let{vars=OuterVars0,arg=OuterArg,
body=InnerArg0}=Outer,
clauses=InnerClauses}=Inner, Sub) ->
@@ -2504,8 +2525,37 @@ is_tuple_type(Var, Sub) ->
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(Expr, Sub) ->
+ case is_bool_expr(Expr, Sub) of
+ false -> Expr;
+ true -> bool
+ end.
+
%% update_types(Expr, Pattern, Sub) -> Sub'
%% Update the type database.
+
+-spec update_types(cerl:cerl(), [type_info()], sub()) -> sub().
+
update_types(Expr, Pat, #sub{t=Tdb0}=Sub) ->
Tdb = update_types_1(Expr, Pat, Tdb0),
Sub#sub{t=Tdb}.
@@ -2525,6 +2575,8 @@ update_types_2(V, [#c_tuple{}=P], Types) ->
orddict:store(V, P, Types);
update_types_2(V, [#c_literal{val=Bool}], Types) when is_boolean(Bool) ->
orddict:store(V, bool, Types);
+update_types_2(V, [Type], Types) when is_atom(Type) ->
+ orddict:store(V, Type, Types);
update_types_2(_, _, Types) -> Types.
%% kill_types(V, Tdb) -> Tdb'
diff --git a/lib/compiler/test/warnings_SUITE.erl b/lib/compiler/test/warnings_SUITE.erl
index dcd3910926..d0b7c71be8 100644
--- a/lib/compiler/test/warnings_SUITE.erl
+++ b/lib/compiler/test/warnings_SUITE.erl
@@ -39,7 +39,7 @@
guard/1,bad_arith/1,bool_cases/1,bad_apply/1,
files/1,effect/1,bin_opt_info/1,bin_construction/1,
comprehensions/1,maps/1,redundant_boolean_clauses/1,
- latin1_fallback/1,underscore/1]).
+ latin1_fallback/1,underscore/1,no_warnings/1]).
% Default timetrap timeout (set in init_per_testcase).
-define(default_timeout, ?t:minutes(2)).
@@ -65,7 +65,7 @@ groups() ->
bad_arith,bool_cases,bad_apply,files,effect,
bin_opt_info,bin_construction,comprehensions,maps,
redundant_boolean_clauses,latin1_fallback,
- underscore]}].
+ underscore,no_warnings]}].
init_per_suite(Config) ->
Config.
@@ -281,7 +281,6 @@ bad_arith(Config) when is_list(Config) ->
{3,sys_core_fold,{eval_failure,badarith}},
{9,sys_core_fold,nomatch_guard},
{9,sys_core_fold,{eval_failure,badarith}},
- {9,sys_core_fold,{no_effect,{erlang,is_integer,1}}},
{10,sys_core_fold,nomatch_guard},
{10,sys_core_fold,{eval_failure,badarith}},
{15,sys_core_fold,{eval_failure,badarith}}
@@ -719,6 +718,27 @@ underscore(Config) when is_list(Config) ->
ok.
+no_warnings(Config) when is_list(Config) ->
+ Ts = [{no_warnings,
+ <<"-record(r, {s=ordsets:new(),a,b}).
+
+ a() ->
+ R = #r{}, %No warning expected.
+ {R#r.a,R#r.b}.
+
+ b(X) ->
+ T = true,
+ Var = [X], %No warning expected.
+ case T of
+ false -> Var;
+ true -> []
+ end.
+ ">>,
+ [],
+ []}],
+ run(Config, Ts),
+ ok.
+
%%%
%%% End of test cases.
%%%
generated by cgit v1.2.3 (git 2.25.1) at 2024-12-25 11:57:30 +0000