From c758fa81e1c48c56ff20ef2a95e6424c1e69033a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Tue, 12 May 2015 06:34:54 +0200
Subject: sys_core_fold: Eliminate warnings for unused terms
The optimization introduced in 0a0d39d351fc would cause spurious
warnings of the type: "a term is constructed, but never used".
To avoid the warning, we must mark not only tuples and lists as
compiler_generated, but also each element. We must also propagate
compiler_generated annotations in lets. For example, if we have:
let <X -| ['compiler_generated']> = 42 in X + 1
we must propagate the compiler_generated annotation to the literal
when do constant propagation:
42 -| ['compiler_generated'] + 1
---
lib/compiler/src/sys_core_fold.erl | 27 ++++++++++++++++++++-------
lib/compiler/test/warnings_SUITE.erl | 8 ++++++++
2 files changed, 28 insertions(+), 7 deletions(-)
(limited to 'lib')
diff --git a/lib/compiler/src/sys_core_fold.erl b/lib/compiler/src/sys_core_fold.erl
index 6f8279f65e..4068d60ec4 100644
--- a/lib/compiler/src/sys_core_fold.erl
+++ b/lib/compiler/src/sys_core_fold.erl
@@ -1130,11 +1130,23 @@ let_substs_1(Vs, #c_values{es=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], [A|As0], Sub) ->
+let_subst_list([V|Vs0], [A0|As0], Sub) ->
{Vs1,As1,Ss} = let_subst_list(Vs0, As0, Sub),
- case is_subst(A) of
- true -> {Vs1,As1,sub_subst_var(V, A, Sub) ++ Ss};
- false -> {[V|Vs1],[A|As1],Ss}
+ 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([], [], _) -> {[],[],[]}.
@@ -1899,8 +1911,8 @@ case_data_pat_alias(P, BindTo0, TypeSig, Bs0) ->
%% Here we will need to actually build the data and bind
%% it to the variable.
{Type,Arity} = TypeSig,
- Vars = make_vars([], Arity),
Ann = [compiler_generated],
+ Vars = make_vars(Ann, Arity),
Data = cerl:ann_make_data(Ann, Type, Vars),
Bs = [{BindTo0,P},{P,Data}|Bs0],
{Vars,Bs};
@@ -2392,8 +2404,9 @@ delay_build_1(Core0, TypeSig) ->
try delay_build_expr(Core0, TypeSig) of
Core ->
{Type,Arity} = TypeSig,
- Vars = make_vars([], Arity),
- Data = cerl:ann_make_data([compiler_generated], Type, Vars),
+ Ann = [compiler_generated],
+ Vars = make_vars(Ann, Arity),
+ Data = cerl:ann_make_data(Ann, Type, Vars),
{yes,Vars,Core,Data}
catch
throw:impossible ->
diff --git a/lib/compiler/test/warnings_SUITE.erl b/lib/compiler/test/warnings_SUITE.erl
index f6ba75577d..471ded219f 100644
--- a/lib/compiler/test/warnings_SUITE.erl
+++ b/lib/compiler/test/warnings_SUITE.erl
@@ -739,6 +739,14 @@ no_warnings(Config) when is_list(Config) ->
case R0 of
{r,V1,_V2,V3} -> {r,V1,\"def\",V3}
end.
+
+ d(In0, Bool) ->
+ {In1,Int} = case id(Bool) of
+ false -> {In0,0}
+ end,
+ [In1,Int].
+
+ id(I) -> I.
">>,
[],
[]}],
--
cgit v1.2.3
From 3d012b584a57e0ba8f76f00f475428a35e081885 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Fri, 22 May 2015 11:54:06 +0200
Subject: sys_core_fold: Eliminate warnings for unused terms in effect context
The optimization introduced in 0a0d39d351fc could cause spurious
warnings of the type: "a term is constructed, but never used".
That would happen for constructs in effect context.
To avoid those warnings, we will need to apply warning suppression
also in effect context.
---
lib/compiler/src/sys_core_fold.erl | 25 +++++++++++++++----------
lib/compiler/test/warnings_SUITE.erl | 16 +++++++++++++++-
2 files changed, 30 insertions(+), 11 deletions(-)
(limited to 'lib')
diff --git a/lib/compiler/src/sys_core_fold.erl b/lib/compiler/src/sys_core_fold.erl
index 4068d60ec4..37006cd8ce 100644
--- a/lib/compiler/src/sys_core_fold.erl
+++ b/lib/compiler/src/sys_core_fold.erl
@@ -2493,7 +2493,7 @@ opt_simple_let_2(Let0, Vs0, Arg0, Body, PrevBody, Ctxt, Sub) ->
Arg1;
false ->
%% let <Var> = Arg in <OtherVar> ==> seq Arg OtherVar
- Arg = maybe_suppress_warnings(Arg1, Vs0, PrevBody, Ctxt),
+ Arg = maybe_suppress_warnings(Arg1, Vs0, PrevBody),
expr(#c_seq{arg=Arg,body=Body}, Ctxt,
sub_new_preserve_types(Sub))
end;
@@ -2501,7 +2501,7 @@ opt_simple_let_2(Let0, Vs0, Arg0, Body, PrevBody, Ctxt, Sub) ->
%% No variables left.
Body;
{Vs,Arg1,#c_literal{}} ->
- Arg = maybe_suppress_warnings(Arg1, Vs, PrevBody, Ctxt),
+ Arg = maybe_suppress_warnings(Arg1, Vs, PrevBody),
E = case Ctxt of
effect ->
%% Throw away the literal body.
@@ -2520,7 +2520,7 @@ opt_simple_let_2(Let0, Vs0, Arg0, Body, PrevBody, Ctxt, Sub) ->
%% seq Arg BodyWithoutVar
case is_any_var_used(Vs, Body) of
false ->
- Arg = maybe_suppress_warnings(Arg1, Vs, PrevBody, Ctxt),
+ Arg = maybe_suppress_warnings(Arg1, Vs, PrevBody),
expr(#c_seq{arg=Arg,body=Body}, Ctxt,
sub_new_preserve_types(Sub));
true ->
@@ -2530,7 +2530,7 @@ opt_simple_let_2(Let0, Vs0, Arg0, Body, PrevBody, Ctxt, Sub) ->
end
end.
-%% maybe_suppress_warnings(Arg, [#c_var{}], PreviousBody, Context) -> Arg'
+%% 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:
%%
@@ -2541,10 +2541,7 @@ opt_simple_let_2(Let0, Vs0, Arg0, Body, PrevBody, Ctxt, Sub) ->
%% referenced in the original unoptimized code. If they were, we will
%% consider the warning false and suppress it.
-maybe_suppress_warnings(Arg, _, _, effect) ->
- %% Don't suppress any warnings in effect context.
- Arg;
-maybe_suppress_warnings(Arg, Vs, PrevBody, value) ->
+maybe_suppress_warnings(Arg, Vs, PrevBody) ->
case should_suppress_warning(Arg) of
true ->
Arg; %Already suppressed.
@@ -2568,8 +2565,16 @@ suppress_warning([H|T]) ->
true ->
suppress_warning(cerl:data_es(H) ++ T);
false ->
- Arg = cerl:set_ann(H, [compiler_generated]),
- cerl:c_seq(Arg, suppress_warning(T))
+ %% 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().
diff --git a/lib/compiler/test/warnings_SUITE.erl b/lib/compiler/test/warnings_SUITE.erl
index 471ded219f..ca6946e3cd 100644
--- a/lib/compiler/test/warnings_SUITE.erl
+++ b/lib/compiler/test/warnings_SUITE.erl
@@ -281,6 +281,7 @@ 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}}
@@ -369,7 +370,7 @@ files(Config) when is_list(Config) ->
%% Test warnings for term construction and BIF calls in effect context.
effect(Config) when is_list(Config) ->
- Ts = [{lc,
+ Ts = [{effect,
<<"
t(X) ->
case X of
@@ -475,6 +476,19 @@ effect(Config) when is_list(Config) ->
m9(Bs) ->
[{B,ok} = {B,foo:bar(B)} || B <- Bs],
ok.
+
+ m10(ConfigTableSize) ->
+ case ConfigTableSize of
+ apa ->
+ CurrentConfig = {id(camel_phase3),id(sms)},
+ case CurrentConfig of
+ {apa, bepa} -> ok;
+ _ -> ok
+ end
+ end,
+ ok.
+
+ id(I) -> I.
">>,
[],
{warnings,[{5,sys_core_fold,{no_effect,{erlang,is_integer,1}}},
--
cgit v1.2.3