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beam_validator: Infer the types of copies in a smarter way 
Smarter code generation means that beam_validator must
be smarter too. In the following example, beam_validator
must be able to infer that y0 refers to a map:

    move x0 y0
    test is_map L1 x0
    %% Here the type for y0 must be 'map'.
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@bjorng
bjorng committed Aug 17, 2018
1 parent 684d07d commit 1f221b2
Showing 1 changed file with 87 additions and 27 deletions.
114 changes: 87 additions & 27 deletions lib/compiler/src/beam_validator.erl
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Expand Up @@ -146,7 +146,8 @@ validate_0(Module, [{function,Name,Ar,Entry,Code}|Fs], Ft) ->
ct=[], %List of hot catch/try labels
setelem=false, %Previous instruction was setelement/3.
puts_left=none, %put/1 instructions left.
defs=#{} %Defining expression for each register.
defs=#{}, %Defining expression for each register.
aliases=#{}
}).

-type label() :: integer().
Expand Down Expand Up @@ -311,9 +312,10 @@ valfun_1({move,{y,_}=Src,{y,_}=Dst}, Vst) ->
{trytag,_} -> error({trytag,Src});
Type -> set_type_reg(Type, Dst, Vst)
end;
valfun_1({move,Src,Dst}, Vst) ->
Type = get_move_term_type(Src, Vst),
set_type_reg(Type, Dst, Vst);
valfun_1({move,Src,Dst}, Vst0) ->
Type = get_move_term_type(Src, Vst0),
Vst = set_type_reg(Type, Dst, Vst0),
set_alias(Src, Dst, Vst);
valfun_1({fmove,Src,{fr,_}=Dst}, Vst) ->
assert_type(float, Src, Vst),
set_freg(Dst, Vst);
Expand Down Expand Up @@ -415,7 +417,7 @@ valfun_1({trim,N,Remaining}, #vst{current=#st{y=Yregs0,numy=NumY}=St}=Vst) ->
N =< NumY, N+Remaining =:= NumY ->
Yregs1 = [{Y-N,Type} || {Y,Type} <- gb_trees:to_list(Yregs0), Y >= N],
Yregs = gb_trees_from_list(Yregs1),
Vst#vst{current=St#st{y=Yregs,numy=NumY-N}};
Vst#vst{current=St#st{y=Yregs,numy=NumY-N,aliases=#{}}};
true ->
error({trim,N,Remaining,allocated,NumY})
end;
Expand All @@ -429,7 +431,7 @@ valfun_1({catch_end,Reg}, #vst{current=#st{ct=[Fail|Fails]}}=Vst0) ->
{catchtag,Fail} ->
Vst = #vst{current=St} = set_catch_end(Reg, Vst0),
Xregs = gb_trees:enter(0, term, St#st.x),
Vst#vst{current=St#st{x=Xregs,ct=Fails,fls=undefined}};
Vst#vst{current=St#st{x=Xregs,ct=Fails,fls=undefined,aliases=#{}}};
Type ->
error({bad_type,Type})
end;
Expand All @@ -446,7 +448,7 @@ valfun_1({try_case,Reg}, #vst{current=#st{ct=[Fail|Fails]}}=Vst0) ->
{trytag,Fail} ->
Vst = #vst{current=St} = set_catch_end(Reg, Vst0),
Xs = gb_trees_from_list([{0,{atom,[]}},{1,term},{2,term}]),
Vst#vst{current=St#st{x=Xs,ct=Fails,fls=undefined}};
Vst#vst{current=St#st{x=Xs,ct=Fails,fls=undefined,aliases=#{}}};
Type ->
error({bad_type,Type})
end;
Expand Down Expand Up @@ -571,7 +573,7 @@ valfun_4({bif,element,{f,Fail},[Pos,Tuple],Dst}, Vst0) ->
PosType = get_term_type(Pos, Vst0),
Vst1 = branch_state(Fail, Vst0),
TupleType = upgrade_tuple_type({tuple,[get_tuple_size(PosType)]}, TupleType0),
Vst = set_type(TupleType, Tuple, Vst1),
Vst = set_aliased_type(TupleType, Tuple, Vst1),
set_type_reg(term, Tuple, Dst, Vst);
valfun_4({bif,raise,{f,0},Src,_Dst}, Vst) ->
validate_src(Src, Vst),
Expand Down Expand Up @@ -716,16 +718,19 @@ valfun_4({test,is_float,{f,Lbl},[Float]}, Vst) ->
valfun_4({test,is_tuple,{f,Lbl},[Tuple]}, Vst) ->
Type0 = get_term_type(Tuple, Vst),
Type = upgrade_tuple_type({tuple,[0]}, Type0),
set_type(Type, Tuple, branch_state(Lbl, Vst));
set_aliased_type(Type, Tuple, branch_state(Lbl, Vst));
valfun_4({test,is_nonempty_list,{f,Lbl},[Cons]}, Vst) ->
assert_term(Cons, Vst),
set_type(cons, Cons, branch_state(Lbl, Vst));
Type = cons,
set_aliased_type(Type, Cons, branch_state(Lbl, Vst));
valfun_4({test,test_arity,{f,Lbl},[Tuple,Sz]}, Vst) when is_integer(Sz) ->
assert_type(tuple, Tuple, Vst),
set_type_reg({tuple,Sz}, Tuple, branch_state(Lbl, Vst));
Type = {tuple,Sz},
set_aliased_type(Type, Tuple, branch_state(Lbl, Vst));
valfun_4({test,is_tagged_tuple,{f,Lbl},[Src,Sz,_Atom]}, Vst) ->
validate_src([Src], Vst),
set_type_reg({tuple, Sz}, Src, branch_state(Lbl, Vst));
Type = {tuple,Sz},
set_aliased_type(Type, Src, branch_state(Lbl, Vst));
valfun_4({test,has_map_fields,{f,Lbl},Src,{list,List}}, Vst) ->
assert_type(map, Src, Vst),
assert_unique_map_keys(List),
Expand All @@ -734,11 +739,12 @@ valfun_4({test,is_map,{f,Lbl},[Src]}, Vst0) ->
Vst = branch_state(Lbl, Vst0),
case Src of
{Tag,_} when Tag =:= x; Tag =:= y ->
set_type_reg(map, Src, Vst);
Type = map,
set_aliased_type(Type, Src, Vst);
{literal,Map} when is_map(Map) ->
Vst;
Vst0;
_ ->
kill_state(Vst)
kill_state(Vst0)
end;
valfun_4({test,is_eq_exact,{f,Lbl},[Src,Val]=Ss}, Vst0) ->
validate_src(Ss, Vst0),
Expand All @@ -750,7 +756,7 @@ valfun_4({test,is_eq_exact,{f,Lbl},[Src,Val]=Ss}, Vst0) ->
Type0 = get_term_type(Val, Vst),
Type = upgrade_tuple_type({tuple,tuple_size(Tuple)},
Type0),
set_type(Type, Src, Vst);
set_aliased_type(Type, Src, Vst);
_ ->
Vst
end;
Expand Down Expand Up @@ -936,7 +942,7 @@ call(Name, Live, #vst{current=St}=Vst) ->
Type when Type =/= exception ->
%% Type is never 'exception' because it has been handled earlier.
Xs = gb_trees_from_list([{0,Type}]),
Vst#vst{current=St#st{x=Xs,f=init_fregs()}}
Vst#vst{current=St#st{x=Xs,f=init_fregs(),aliases=#{}}}
end.

%% Tail call.
Expand Down Expand Up @@ -1049,15 +1055,25 @@ heap_alloc_2([{floats,Floats}|T], St0) ->
St = St0#st{hf=Floats},
heap_alloc_2(T, St);
heap_alloc_2([], St) -> St.
prune_x_regs(Live, #vst{current=#st{x=Xs0,defs=Defs0}=St0}=Vst)

prune_x_regs(Live, #vst{current=St0}=Vst)
when is_integer(Live) ->
#st{x=Xs0,defs=Defs0,aliases=Aliases0} = St0,
Xs1 = gb_trees:to_list(Xs0),
Xs = [P || {R,_}=P <- Xs1, R < Live],
Defs = maps:filter(fun({x,X}, _) -> X < Live;
({y,_}, _) -> true
end, Defs0),
St = St0#st{x=gb_trees:from_orddict(Xs),defs=Defs},
Aliases = maps:filter(fun({x,X1}, {x,X2}) ->
X1 < Live andalso X2 < Live;
({x,X}, _) ->
X < Live;
(_, {x,X}) ->
X < Live;
(_, _) ->
true
end, Aliases0),
St = St0#st{x=gb_trees:from_orddict(Xs),defs=Defs,aliases=Aliases},
Vst#vst{current=St}.

%%%
Expand Down Expand Up @@ -1224,6 +1240,37 @@ infer_types(Src, Vst) ->
%%% Keeping track of types.
%%%

set_alias(Reg1, Reg2, #vst{current=St0}=Vst) ->
case Reg1 of
{Kind,_} when Kind =:= x; Kind =:= y ->
#st{aliases=Aliases0} = St0,
Aliases = Aliases0#{Reg1=>Reg2,Reg2=>Reg1},
St = St0#st{aliases=Aliases},
Vst#vst{current=St};
_ ->
Vst
end.

set_aliased_type(Type, Reg, #vst{current=#st{aliases=Aliases}}=Vst0) ->
Vst1 = set_type(Type, Reg, Vst0),
case Aliases of
#{Reg:=OtherReg} ->
Vst = set_type_reg(Type, OtherReg, Vst1),
#vst{current=St} = Vst,
Vst#vst{current=St#st{aliases=Aliases}};
#{} ->
Vst1
end.

kill_aliases(Reg, #st{aliases=Aliases0}=St) ->
case Aliases0 of
#{Reg:=OtherReg} ->
Aliases = maps:without([Reg,OtherReg], Aliases0),
St#st{aliases=Aliases};
#{} ->
St
end.

set_type(Type, {x,_}=Reg, Vst) -> set_type_reg(Type, Reg, Vst);
set_type(Type, {y,_}=Reg, Vst) -> set_type_y(Type, Reg, Vst);
set_type(_, _, #vst{}=Vst) -> Vst.
Expand All @@ -1247,7 +1294,7 @@ set_type_reg_expr(Type, Expr, Reg, Vst) ->
set_type_y(Type, Reg, Vst) ->
set_type_y(Type, none, Reg, Vst).

set_type_x(Type, Expr, {x,X}=Reg, #vst{current=#st{x=Xs0,defs=Defs0}=St}=Vst)
set_type_x(Type, Expr, {x,X}=Reg, #vst{current=#st{x=Xs0,defs=Defs0}=St0}=Vst)
when is_integer(X), 0 =< X ->
check_limit(Reg),
Xs = case gb_trees:lookup(X, Xs0) of
Expand All @@ -1259,11 +1306,12 @@ set_type_x(Type, Expr, {x,X}=Reg, #vst{current=#st{x=Xs0,defs=Defs0}=St}=Vst)
gb_trees:update(X, Type, Xs0)
end,
Defs = Defs0#{Reg=>Expr},
St = kill_aliases(Reg, St0),
Vst#vst{current=St#st{x=Xs,defs=Defs}};
set_type_x(Type, _Expr, Reg, #vst{}) ->
error({invalid_store,Reg,Type}).

set_type_y(Type, Expr, {y,Y}=Reg, #vst{current=#st{y=Ys0,defs=Defs0}=St}=Vst)
set_type_y(Type, Expr, {y,Y}=Reg, #vst{current=#st{y=Ys0,defs=Defs0}=St0}=Vst)
when is_integer(Y), 0 =< Y ->
check_limit(Reg),
Ys = case gb_trees:lookup(Y, Ys0) of
Expand All @@ -1278,6 +1326,7 @@ set_type_y(Type, Expr, {y,Y}=Reg, #vst{current=#st{y=Ys0,defs=Defs0}=St}=Vst)
end,
check_try_catch_tags(Type, Y, Ys0),
Defs = Defs0#{Reg=>Expr},
St = kill_aliases(Reg, St0),
Vst#vst{current=St#st{y=Ys,defs=Defs}};
set_type_y(Type, _Expr, Reg, #vst{}) ->
error({invalid_store,Reg,Type}).
Expand Down Expand Up @@ -1523,7 +1572,7 @@ get_literal({literal,L}) -> L;
get_literal(T) -> error({not_literal,T}).

branch_arities([Sz,{f,L}|T], Tuple, {tuple,[_]}=Type0, Vst0) when is_integer(Sz) ->
Vst1 = set_type_reg({tuple,Sz}, Tuple, Vst0),
Vst1 = set_aliased_type({tuple,Sz}, Tuple, Vst0),
Vst = branch_state(L, Vst1),
branch_arities(T, Tuple, Type0, Vst);
branch_arities([Sz,{f,L}|T], Tuple, {tuple,Sz}=Type, Vst0) when is_integer(Sz) ->
Expand Down Expand Up @@ -1565,13 +1614,14 @@ merge_states(L, St, Branched) when L =/= 0 ->
{value,OtherSt} -> merge_states_1(St, OtherSt)
end.

merge_states_1(#st{x=Xs0,y=Ys0,numy=NumY0,h=H0,ct=Ct0},
#st{x=Xs1,y=Ys1,numy=NumY1,h=H1,ct=Ct1}) ->
merge_states_1(#st{x=Xs0,y=Ys0,numy=NumY0,h=H0,ct=Ct0,aliases=Aliases0},
#st{x=Xs1,y=Ys1,numy=NumY1,h=H1,ct=Ct1,aliases=Aliases1}) ->
NumY = merge_stk(NumY0, NumY1),
Xs = merge_regs(Xs0, Xs1),
Ys = merge_y_regs(Ys0, Ys1),
Ct = merge_ct(Ct0, Ct1),
#st{x=Xs,y=Ys,numy=NumY,h=min(H0, H1),ct=Ct}.
Aliases = merge_aliases(Aliases0, Aliases1),
#st{x=Xs,y=Ys,numy=NumY,h=min(H0, H1),ct=Ct,aliases=Aliases}.

merge_stk(S, S) -> S;
merge_stk(_, _) -> undecided.
Expand Down Expand Up @@ -1680,7 +1730,17 @@ merge_bool([]) -> {atom,[]};
merge_bool(true) -> bool;
merge_bool(false) -> bool;
merge_bool(_) -> {atom,[]}.


merge_aliases(Al0, Al1) when map_size(Al0) =< map_size(Al1) ->
maps:filter(fun(K, V) ->
case Al1 of
#{K:=V} -> true;
#{} -> false
end
end, Al0);
merge_aliases(Al0, Al1) ->
merge_aliases(Al1, Al0).

verify_y_init(#vst{current=#st{y=Ys}}) ->
verify_y_init_1(gb_trees:to_list(Ys)).

Expand Down

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