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beam_ssa_type: Fix bugs relating to subtraction in type inference #7489

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Sep 20, 2023
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beam_ssa_type: Fix bugs relating to subtraction in type inference #7489

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85 changes: 61 additions & 24 deletions lib/compiler/src/beam_ssa_type.erl
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Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,7 @@
%% it goes.
%%

-feature(maybe_expr, enable).
-module(beam_ssa_type).
-export([opt_start/2, opt_continue/4, opt_finish/3, opt_ranges/1]).

Expand Down Expand Up @@ -2497,17 +2498,27 @@ infer_types_br_1(V, Ts, Ds) ->
FailTs = subtract_types(NegTypes, Ts),
{SuccTs, FailTs};
InvOp ->
%% This is an relational operator.
%% This is a relational operator.
{bif,Op} = Op0,

%% Infer the types for both sides of operator succceding.
%% Infer the types for both sides of operator succeeding.
Types = concrete_types(Args, Ts),
TrueTypes0 = infer_relop(Op, Args, Types, Ds),
TrueTypes = meet_types(TrueTypes0, Ts),
{TruePos, TrueNeg} = infer_relop(Op, Args, Types, Ds),
TrueTypes = maybe
TrueTypes0 = #{} ?= meet_types(TruePos, Ts),
subtract_types(TrueNeg, TrueTypes0)
else
none -> none
end,

%% Infer the types for both sides of operator failing.
FalseTypes0 = infer_relop(InvOp, Args, Types, Ds),
FalseTypes = meet_types(FalseTypes0, Ts),
{FalsePos, FalseNeg} = infer_relop(InvOp, Args, Types, Ds),
FalseTypes = maybe
FalseTypes0 = #{} ?= meet_types(FalsePos, Ts),
subtract_types(FalseNeg, FalseTypes0)
else
none -> none
end,

{TrueTypes, FalseTypes}
end.
Expand All @@ -2524,12 +2535,12 @@ infer_relop('=:=', [LHS,RHS],
%% In order to avoid narrowing the types with regard to
%% appendable-status, deduce the types for the case when neither
%% LHS or RHS are appendable, then restore the appendable-status.
[{LHS,LType},{RHS,RType}|EqTypes] =
{[{LHS,LType},{RHS,RType} | EqTypes], []} =
infer_relop('=:=', [LHS,RHS],
[LType0#t_bitstring{appendable=false},
RType0#t_bitstring{appendable=false}], Ds),
[{LHS,LType#t_bitstring{appendable=LHSApp}},
{RHS,RType#t_bitstring{appendable=RHSApp}}|EqTypes];
{[{LHS,LType#t_bitstring{appendable=LHSApp}},
{RHS,RType#t_bitstring{appendable=RHSApp}} | EqTypes], []};
infer_relop('=:=', [LHS,RHS], [LType,RType], Ds) ->
EqTypes = infer_eq_type(map_get(LHS, Ds), RType),

Expand All @@ -2538,11 +2549,10 @@ infer_relop('=:=', [LHS,RHS], [LType,RType], Ds) ->
%% can be inferred that L1 is 'cons' (the meet of 'cons' and
%% 'list').
Type = beam_types:meet(LType, RType),
[{LHS,Type},{RHS,Type}] ++ EqTypes;
infer_relop(Op, Args, Types, _Ds) ->
infer_relop(Op, Args, Types).
{[{LHS,Type},{RHS,Type}] ++ EqTypes, []};
infer_relop('=/=', [LHS,RHS], [LType,RType], Ds) ->
NeTypes = infer_ne_type(map_get(LHS, Ds), RType),

infer_relop('=/=', [LHS,RHS], [LType,RType]) ->
%% We must be careful with types inferred from '=/='.
%%
%% For example, if we have L =/= [a], we must not subtract 'cons'
Expand All @@ -2554,9 +2564,12 @@ infer_relop('=/=', [LHS,RHS], [LType,RType]) ->
%% value and vice versa. We must not subtract the meet of the two
%% as it may be too specific. See beam_type_SUITE:type_subtraction/1
%% for details.
[{V,beam_types:subtract(ThisType, OtherType)} ||
{V, ThisType, OtherType} <- [{RHS, RType, LType}, {LHS, LType, RType}],
beam_types:is_singleton_type(OtherType)];
{[{V,beam_types:subtract(ThisType, OtherType)} ||
{V, ThisType, OtherType} <- [{RHS, RType, LType}, {LHS, LType, RType}],
beam_types:is_singleton_type(OtherType)], NeTypes};
infer_relop(Op, Args, Types, _Ds) ->
{infer_relop(Op, Args, Types), []}.

infer_relop(Op, [Arg1,Arg2], Types0) ->
case infer_relop(Op, Types0) of
any ->
Expand Down Expand Up @@ -2659,8 +2672,13 @@ infer_br_value(V, Bool, NewTs) ->
infer_types_switch(V, Lit, Ts0, IsTempVar, Ds) ->
Args = [V,Lit],
Types = concrete_types(Args, Ts0),
PosTypes = infer_relop('=:=', Args, Types, Ds),
Ts = meet_types(PosTypes, Ts0),
{PosTypes, NegTypes} = infer_relop('=:=', Args, Types, Ds),
Ts = maybe
Ts1 = #{} ?= meet_types(PosTypes, Ts0),
subtract_types(NegTypes, Ts1)
else
none -> none
end,
case IsTempVar of
true -> ts_remove_var(V, Ts);
false -> Ts
Expand Down Expand Up @@ -2744,15 +2762,15 @@ infer_type({bif,'and'}, [#b_var{}=LHS,#b_var{}=RHS], Ts, Ds) ->
%% rewrite this BIF to plain control flow.
%%
%% Note that we can't do anything for the 'false' case as either (or both)
%% of the arguments could be false.
%% of the arguments could be false, so we must ignore the negations.
#{ LHS := #b_set{op=LHSOp,args=LHSArgs},
RHS := #b_set{op=RHSOp,args=RHSArgs} } = Ds,

LHSTypes = infer_and_type(LHSOp, LHSArgs, Ts, Ds),
RHSTypes = infer_and_type(RHSOp, RHSArgs, Ts, Ds),
{LHSPos, _} = infer_and_type(LHSOp, LHSArgs, Ts, Ds),
{RHSPos, _} = infer_and_type(RHSOp, RHSArgs, Ts, Ds),

True = beam_types:make_atom(true),
{[{LHS, True}, {RHS, True}] ++ LHSTypes ++ RHSTypes, []};
{[{LHS, True}, {RHS, True}] ++ LHSPos ++ RHSPos, []};
infer_type(_Op, _Args, _Ts, _Ds) ->
{[], []}.

Expand Down Expand Up @@ -2801,11 +2819,30 @@ infer_eq_type(#b_set{op=get_tuple_element,
infer_eq_type(_, _) ->
[].

infer_ne_type(#b_set{op={bif,tuple_size},args=[#b_var{}=Tuple]},
#t_integer{elements={Size,Size}}) ->
[{Tuple,#t_tuple{exact=true,size=Size}}];
infer_ne_type(#b_set{op=get_tuple_element,
args=[#b_var{}=Tuple,#b_literal{val=N}]},
ElementType) ->
Index = N + 1,
case {beam_types:is_singleton_type(ElementType),
beam_types:set_tuple_element(Index, ElementType, #{})} of
{true, #{ Index := _ }=Es} ->
[{Tuple,#t_tuple{size=Index,elements=Es}}];
{_, #{}} ->
%% Subtraction is not safe: either we had a non-singleton element
%% type (see inference for `=/=`), or the element index was out of
%% range.
[]
end;
infer_ne_type(_, _) ->
[].

infer_and_type(Op, Args, Ts, Ds) ->
case inv_relop(Op) of
none ->
{LHSTypes0, _} = infer_type(Op, Args, Ts, Ds),
LHSTypes0;
infer_type(Op, Args, Ts, Ds);
_InvOp ->
{bif,RelOp} = Op,
infer_relop(RelOp, Args, concrete_types(Args, Ts), Ds)
Expand Down
43 changes: 43 additions & 0 deletions lib/compiler/test/beam_type_SUITE.erl
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Original file line number Diff line number Diff line change
Expand Up @@ -1047,8 +1047,16 @@ sto_1(step_4_3) -> {b, [sto_1(case_3_3)]}.
%% 3, so we must not subtract 2 on the failure path.
type_subtraction(Config) when is_list(Config) ->
true = type_subtraction_1(id(<<"A">>)),

ok = type_subtraction_2(id(true)),
<<"aaaa">> = type_subtraction_2(id(false)),
{'EXIT', _} = catch type_subtraction_3(id(false)),
ok = catch type_subtraction_4(id(ok)),
{'EXIT', _} = catch type_subtraction_4(id(false)),

ok.


type_subtraction_1(_x@1) ->
_a@1 = ts_12(_x@1),
_b@1 = ts_23(_x@1),
Expand All @@ -1073,6 +1081,41 @@ ts_23(_x@1) ->
2
end.

type_subtraction_2(X) ->
case ts_34(X) of
Tuple when element(1, Tuple) =:= ok ->
ok;
Tuple when element(1, Tuple) =:= error ->
element(2, Tuple)
end.

ts_34(X) ->
case X of
true -> {ok};
false -> {error, <<"aaaa">>}
end.

type_subtraction_3(_V0) when is_boolean(_V0), is_binary(_V0), _V0 andalso _V0 ->
ok.

type_subtraction_4(_V0) ->
try
_V0 = ok
catch
_ ->
<<
0
|| _V0 := _ <- ok,
(try ok of
_ when _V0, (_V0 andalso _V0) orelse trunc(ok) ->
ok
catch
_ ->
ok
end)
>>
end.

%% GH-4774: The validator didn't update container contents on type subtraction.
container_subtraction(Config) when is_list(Config) ->
A = id(baz),
Expand Down