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authorBjörn Gustavsson <[email protected]>2015-05-22 11:54:06 +0200
committerBjörn Gustavsson <[email protected]>2015-05-22 12:44:30 +0200
commit3d012b584a57e0ba8f76f00f475428a35e081885 (patch)
tree0495569eee343a4f0e6a30a7276918cfa9ae100d /lib/compiler/src
parentc758fa81e1c48c56ff20ef2a95e6424c1e69033a (diff)
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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.
Diffstat (limited to 'lib/compiler/src')
-rw-r--r--lib/compiler/src/sys_core_fold.erl25
1 files changed, 15 insertions, 10 deletions
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().