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-rw-r--r--lib/compiler/src/beam_ssa_codegen.erl18
-rw-r--r--lib/compiler/src/beam_validator.erl20
-rw-r--r--lib/compiler/test/beam_ssa_SUITE.erl29
3 files changed, 56 insertions, 11 deletions
diff --git a/lib/compiler/src/beam_ssa_codegen.erl b/lib/compiler/src/beam_ssa_codegen.erl
index 07f4c8b461..08641e2abc 100644
--- a/lib/compiler/src/beam_ssa_codegen.erl
+++ b/lib/compiler/src/beam_ssa_codegen.erl
@@ -764,9 +764,8 @@ defined(Linear, #cg{regs=Regs}) ->
def([{L,#cg_blk{is=Is0,last=Last}=Blk0}|Bs], DefMap0, Regs) ->
Def0 = def_get(L, DefMap0),
- {Is,Def} = def_is(Is0, Regs, Def0, []),
- Successors = successors(Last),
- DefMap = def_successors(Successors, Def, DefMap0),
+ {Is,Def,MaybeDef} = def_is(Is0, Regs, Def0, []),
+ DefMap = def_successors(Last, Def, MaybeDef, DefMap0),
Blk = Blk0#cg_blk{is=Is},
[{L,Blk}|def(Bs, DefMap, Regs)];
def([], _, _) -> [].
@@ -780,6 +779,11 @@ def_get(L, DefMap) ->
def_is([#cg_alloc{anno=Anno0}=I0|Is], Regs, Def, Acc) ->
I = I0#cg_alloc{anno=Anno0#{def_yregs=>Def}},
def_is(Is, Regs, Def, [I|Acc]);
+def_is([#cg_set{op=succeeded,args=[Var]}=I], Regs, Def, Acc) ->
+ %% Var will only be defined on the success branch of the `br`
+ %% for this block.
+ MaybeDef = def_add_yreg(Var, [], Regs),
+ {reverse(Acc, [I]),Def,MaybeDef};
def_is([#cg_set{op=kill_try_tag,args=[#b_var{}=Tag]}=I|Is], Regs, Def0, Acc) ->
Def = ordsets:del_element(Tag, Def0),
def_is(Is, Regs, Def, [I|Acc]);
@@ -822,7 +826,7 @@ def_is([#cg_set{anno=Anno0,dst=Dst}=I0|Is], Regs, Def0, Acc) ->
Def = def_add_yreg(Dst, Def0, Regs),
def_is(Is, Regs, Def, [I|Acc]);
def_is([], _, Def, Acc) ->
- {reverse(Acc),Def}.
+ {reverse(Acc),Def,[]}.
def_add_yreg(Dst, Def, Regs) ->
case is_yreg(Dst, Regs) of
@@ -830,6 +834,12 @@ def_add_yreg(Dst, Def, Regs) ->
false -> Def
end.
+def_successors(#cg_br{bool=#b_var{},succ=Succ,fail=Fail}, Def, MaybeDef, DefMap0) ->
+ DefMap = def_successors([Fail], ordsets:subtract(Def, MaybeDef), DefMap0),
+ def_successors([Succ], Def, DefMap);
+def_successors(Last, Def, [], DefMap) ->
+ def_successors(successors(Last), Def, DefMap).
+
def_successors([S|Ss], Def0, DefMap) ->
case DefMap of
#{S:=Def1} ->
diff --git a/lib/compiler/src/beam_validator.erl b/lib/compiler/src/beam_validator.erl
index ebe9631e09..370481d08a 100644
--- a/lib/compiler/src/beam_validator.erl
+++ b/lib/compiler/src/beam_validator.erl
@@ -1068,8 +1068,11 @@ verify_get_map(Fail, Src, List, Vst0) ->
%% {get_map_elements,{f,7},{x,1},{list,[{atom,a},{x,1},{atom,b},{x,2}]}}.
%%
%% If 'a' exists but not 'b', {x,1} is overwritten when we jump to {f,7}.
+%%
+%% We must be careful to preserve the uninitialized status for Y registers
+%% that have been allocated but not yet defined.
clobber_map_vals([Key,Dst|T], Map, Vst0) ->
- case is_reg_defined(Dst, Vst0) of
+ case is_reg_initialized(Dst, Vst0) of
true ->
Vst = extract_term(term, {bif,map_get}, [Key, Map], Dst, Vst0),
clobber_map_vals(T, Map, Vst);
@@ -1079,6 +1082,17 @@ clobber_map_vals([Key,Dst|T], Map, Vst0) ->
clobber_map_vals([], _Map, Vst) ->
Vst.
+is_reg_initialized({x,_}=Reg, #vst{current=#st{xs=Xs}}) ->
+ is_map_key(Reg, Xs);
+is_reg_initialized({y,_}=Reg, #vst{current=#st{ys=Ys}}) ->
+ case Ys of
+ #{Reg:=Val} ->
+ Val =/= uninitialized;
+ #{} ->
+ false
+ end;
+is_reg_initialized(V, #vst{}) -> error({not_a_register, V}).
+
extract_map_keys([Key,_Val|T]) ->
[Key|extract_map_keys(T)];
extract_map_keys([]) -> [].
@@ -1885,10 +1899,6 @@ check_try_catch_tags(Type, {y,N}=Reg, Vst) ->
ok
end.
-is_reg_defined({x,_}=Reg, #vst{current=#st{xs=Xs}}) -> is_map_key(Reg, Xs);
-is_reg_defined({y,_}=Reg, #vst{current=#st{ys=Ys}}) -> is_map_key(Reg, Ys);
-is_reg_defined(V, #vst{}) -> error({not_a_register, V}).
-
assert_term(Src, Vst) ->
_ = get_term_type(Src, Vst),
ok.
diff --git a/lib/compiler/test/beam_ssa_SUITE.erl b/lib/compiler/test/beam_ssa_SUITE.erl
index dd1b7ddcd3..6f99b0e28e 100644
--- a/lib/compiler/test/beam_ssa_SUITE.erl
+++ b/lib/compiler/test/beam_ssa_SUITE.erl
@@ -23,7 +23,7 @@
init_per_group/2,end_per_group/2,
calls/1,tuple_matching/1,recv/1,maps/1,
cover_ssa_dead/1,combine_sw/1,share_opt/1,
- beam_ssa_dead_crash/1]).
+ beam_ssa_dead_crash/1,stack_init/1]).
suite() -> [{ct_hooks,[ts_install_cth]}].
@@ -39,7 +39,8 @@ groups() ->
cover_ssa_dead,
combine_sw,
share_opt,
- beam_ssa_dead_crash
+ beam_ssa_dead_crash,
+ stack_init
]}].
init_per_suite(Config) ->
@@ -589,6 +590,30 @@ do_beam_ssa_dead_crash(A, B) ->
end
end.
+stack_init(_Config) ->
+ 6 = stack_init(a, #{a => [1,2,3]}),
+ 0 = stack_init(missing, #{}),
+ ok.
+
+stack_init(Key, Map) ->
+ %% beam_ssa_codegen would wrongly assume that y(0) would always be
+ %% initialized by the `get_map_elements` instruction that follows, and
+ %% would set up the stack frame using an `allocate` instruction and
+ %% would not generate an `init` instruction to initialize y(0).
+ Res = case Map of
+ #{Key := Elements} ->
+ %% Elements will be assigned to y(0) if the key Key exists.
+ lists:foldl(fun(El, Acc) ->
+ Acc + El
+ end, 0, Elements);
+ #{} ->
+ %% y(0) will be left uninitialized when the key is not
+ %% present in the map.
+ 0
+ end,
+ %% y(0) would be uninitialized here if the key was not present in the map
+ %% (if the second clause was executed).
+ id(Res).
%% The identity function.
id(I) -> I.