aboutsummaryrefslogtreecommitdiffstats
path: root/lib/compiler/src
diff options
context:
space:
mode:
authorBjörn Gustavsson <[email protected]>2016-06-02 09:58:46 +0200
committerBjörn Gustavsson <[email protected]>2016-06-02 12:51:18 +0200
commit5facb518a9ee2d756564eccd92a2c11f334d6282 (patch)
tree459b4574356863255a4e27aa017c04796780fdd9 /lib/compiler/src
parentaab1db16d0a732823fa9e2964c6a52b109c61742 (diff)
downloadotp-5facb518a9ee2d756564eccd92a2c11f334d6282.tar.gz
otp-5facb518a9ee2d756564eccd92a2c11f334d6282.tar.bz2
otp-5facb518a9ee2d756564eccd92a2c11f334d6282.zip
Eliminate crash for map updates in guards
beam_validator would complain that x(1) is uninitialized in a test_heap instruction when attempting to compile the following code with sys_core_fold turned off: foo(M) when not (M#{true := 0}); [M] -> ok. Simplified, the generated BEAM assembly code looked like this: test is_map BadMap x(0) put_map_exact Fail x(0) => x(1) ... jump BooleanStuff BadMap: move ok => x(1) jump Fail BooleanStuff: ... move Boolean => x(2) jump Build Fail: move false => x(2) Build: test_heap 2 3 %% x(0), x(1), x(2) must be live. ... That is, if put_map_exact failed, control would transfer to the label Fail without initializing x(1). Fix that by making sure that x(1) is initilized even if put_map_exact fails: test is_map BadMap x(0) put_map_exact BadLbl x(0) => x(1) ... jump OkLbl BadLbl: move ok => x(1) jump Fail OkLbl: jump BooleanStuff BadMap: move ok => x(1) jump Fail BooleanStuff: ... move Boolean => x(2) jump Build Fail: move false => x(2) Build: test_heap 2 3 %% x(0), x(1), x(2) must be live. ... Note that this situation is rare, and that other optimization passes (beam_dead and beam_jump in particular) will clean up this mess.
Diffstat (limited to 'lib/compiler/src')
-rw-r--r--lib/compiler/src/beam_validator.erl4
-rw-r--r--lib/compiler/src/v3_codegen.erl60
2 files changed, 43 insertions, 21 deletions
diff --git a/lib/compiler/src/beam_validator.erl b/lib/compiler/src/beam_validator.erl
index 13aa31b7c9..4c0cb6780a 100644
--- a/lib/compiler/src/beam_validator.erl
+++ b/lib/compiler/src/beam_validator.erl
@@ -658,8 +658,10 @@ valfun_4({test,is_map,{f,Lbl},[Src]}, Vst0) ->
case Src of
{Tag,_} when Tag =:= x; Tag =:= y ->
set_type_reg(map, Src, Vst);
+ {literal,Map} when is_map(Map) ->
+ Vst;
_ ->
- Vst
+ kill_state(Vst)
end;
valfun_4({test,_Op,{f,Lbl},Src}, Vst) ->
validate_src(Src, Vst),
diff --git a/lib/compiler/src/v3_codegen.erl b/lib/compiler/src/v3_codegen.erl
index f5f3c73793..4df1aadd0a 100644
--- a/lib/compiler/src/v3_codegen.erl
+++ b/lib/compiler/src/v3_codegen.erl
@@ -1551,12 +1551,10 @@ set_cg([{var,R}], {binary,Segs}, Le, Vdb, Bef, #cg{bfail=Bfail}=St) ->
%% Now generate the complete code for constructing the binary.
Code = cg_binary(PutCode, Target, Temp, Fail, MaxRegs, Le#l.a),
{Sis++Code,Aft,St};
-% Map single variable key
-set_cg([{var,R}], {map,Op,Map,[{map_pair,{var,_}=K,V}]}, Le, Vdb, Bef,
- #cg{bfail=Bfail}=St) ->
- Fail = {f,Bfail},
- {Sis,Int0} = maybe_adjust_stack(Bef, Le#l.i, Le#l.i+1, Vdb, St),
+%% Map: single variable key.
+set_cg([{var,R}], {map,Op,Map,[{map_pair,{var,_}=K,V}]}, Le, Vdb, Bef, St0) ->
+ {Sis,Int0} = maybe_adjust_stack(Bef, Le#l.i, Le#l.i+1, Vdb, St0),
SrcReg = cg_reg_arg_prefer_y(Map, Int0),
Line = line(Le#l.a),
@@ -1570,21 +1568,16 @@ set_cg([{var,R}], {map,Op,Map,[{map_pair,{var,_}=K,V}]}, Le, Vdb, Bef,
Aft = Aft0#sr{reg=put_reg(R, Aft0#sr.reg)},
Target = fetch_reg(R, Aft#sr.reg),
- I = case Op of
- assoc -> put_map_assoc;
- exact -> put_map_exact
- end,
- {Sis++[Line]++[{I,Fail,SrcReg,Target,Live,{list,List}}],Aft,St};
+ {Is,St1} = set_cg_map(Line, Op, SrcReg, Target, Live, List, St0),
+ {Sis++Is,Aft,St1};
-% Map (possibly) multiple literal keys
-set_cg([{var,R}], {map,Op,Map,Es}, Le, Vdb, Bef,
- #cg{bfail=Bfail}=St) ->
+%% Map: (possibly) multiple literal keys.
+set_cg([{var,R}], {map,Op,Map,Es}, Le, Vdb, Bef, St0) ->
%% assert key literals
[] = [Var||{map_pair,{var,_}=Var,_} <- Es],
- Fail = {f,Bfail},
- {Sis,Int0} = maybe_adjust_stack(Bef, Le#l.i, Le#l.i+1, Vdb, St),
+ {Sis,Int0} = maybe_adjust_stack(Bef, Le#l.i, Le#l.i+1, Vdb, St0),
SrcReg = cg_reg_arg_prefer_y(Map, Int0),
Line = line(Le#l.a),
@@ -1599,11 +1592,10 @@ set_cg([{var,R}], {map,Op,Map,Es}, Le, Vdb, Bef,
Aft = Aft0#sr{reg=put_reg(R, Aft0#sr.reg)},
Target = fetch_reg(R, Aft#sr.reg),
- I = case Op of
- assoc -> put_map_assoc;
- exact -> put_map_exact
- end,
- {Sis++[Line]++[{I,Fail,SrcReg,Target,Live,{list,List}}],Aft,St};
+ {Is,St1} = set_cg_map(Line, Op, SrcReg, Target, Live, List, St0),
+ {Sis++Is,Aft,St1};
+
+%% Everything else.
set_cg([{var,R}], Con, Le, Vdb, Bef, St) ->
%% Find a place for the return register first.
Int = Bef#sr{reg=put_reg(R, Bef#sr.reg)},
@@ -1616,6 +1608,34 @@ set_cg([{var,R}], Con, Le, Vdb, Bef, St) ->
end,
{Ais,clear_dead(Int, Le#l.i, Vdb),St}.
+
+set_cg_map(Line, Op0, SrcReg, Target, Live, List, St0) ->
+ Bfail = St0#cg.bfail,
+ Fail = {f,St0#cg.bfail},
+ Op = case Op0 of
+ assoc -> put_map_assoc;
+ exact -> put_map_exact
+ end,
+ {OkLbl,St1} = new_label(St0),
+ {BadLbl,St2} = new_label(St1),
+ Is = if
+ Bfail =:= 0 orelse Op =:= put_map_assoc ->
+ [Line,{Op,{f,0},SrcReg,Target,Live,{list,List}}];
+ true ->
+ %% Ensure that Target is always set, even if
+ %% the map update operation fails. That is necessary
+ %% because Target may be included in a test_heap
+ %% instruction.
+ [Line,
+ {Op,{f,BadLbl},SrcReg,Target,Live,{list,List}},
+ {jump,{f,OkLbl}},
+ {label,BadLbl},
+ {move,{atom,ok},Target},
+ {jump,Fail},
+ {label,OkLbl}]
+ end,
+ {Is,St2}.
+
%%%
%%% Code generation for constructing binaries.
%%%