6 files changed, 39 insertions, 4 deletions
diff --git a/lib/compiler/src/beam_dead.erl b/lib/compiler/src/beam_dead.erl
index dbbaae05eb..762c7bdf9e 100644
--- a/lib/compiler/src/beam_dead.erl
+++ b/lib/compiler/src/beam_dead.erl
@@ -392,6 +392,26 @@ backward([{bif,'or',{f,To0},[Dst,{atom,false}],Dst}=I|Is], D,
 	_ ->
 	    backward(Is, D, [I|Acc])
     end;
+backward([{bif,map_get,{f,FF},[Key,Map],_}=I0,
+          {test,has_map_fields,{f,FT}=F,[Map|Keys0]}=I1|Is], D, Acc) when FF =/= 0 ->
+    case shortcut_label(FF, D) of
+        FT ->
+            case lists:delete(Key, Keys0) of
+                [] ->
+                    backward([I0|Is], D, Acc);
+                Keys ->
+                    Test = {test,has_map_fields,F,[Map|Keys]},
+                    backward([Test|Is], D, [I0|Acc])
+            end;
+        _ ->
+            backward([I1|Is], D, [I0|Acc])
+    end;
+backward([{bif,map_get,{f,FF},[_,Map],_}=I0,
+          {test,is_map,{f,FT},[Map]}=I1|Is], D, Acc) when FF =/= 0 ->
+    case shortcut_label(FF, D) of
+        FT -> backward([I0|Is], D, Acc);
+        _ -> backward([I1|Is], D, [I0|Acc])
+    end;
 backward([I|Is], D, Acc) ->
     backward(Is, D, [I|Acc]);
 backward([], _D, Acc) -> Acc.
diff --git a/lib/compiler/src/beam_peep.erl b/lib/compiler/src/beam_peep.erl
index eb3192fe8f..920fb00397 100644
--- a/lib/compiler/src/beam_peep.erl
+++ b/lib/compiler/src/beam_peep.erl
@@ -77,6 +77,12 @@ peep([{bif,tuple_size,_,[_]=Ops,Dst}=I|Is], SeenTests0, Acc) ->
     %% Kill all remembered tests that depend on the destination register.
     SeenTests = kill_seen(Dst, SeenTests1),
     peep(Is, SeenTests, [I|Acc]);
+peep([{bif,map_get,_,[Key,Map],Dst}=I|Is], SeenTests0, Acc) ->
+    %% Pretend that we have seen {test,has_map_fields,_,[Map,Key]}
+    SeenTests1 = gb_sets:add({has_map_fields,[Map,Key]}, SeenTests0),
+    %% Kill all remembered tests that depend on the destination register.
+    SeenTests = kill_seen(Dst, SeenTests1),
+    peep(Is, SeenTests, [I|Acc]);
 peep([{bif,_,_,_,Dst}=I|Is], SeenTests0, Acc) ->
     %% Kill all remembered tests that depend on the destination register.
     SeenTests = kill_seen(Dst, SeenTests0),
diff --git a/lib/compiler/src/beam_type.erl b/lib/compiler/src/beam_type.erl
index 28f36db399..12da8c9446 100644
--- a/lib/compiler/src/beam_type.erl
+++ b/lib/compiler/src/beam_type.erl
@@ -462,6 +462,9 @@ update({set,[D],[Index,Reg],{bif,element,_}}, Ts0) ->
               end,
     Ts = tdb_meet(Reg, {tuple,min_size,MinSize,[]}, Ts0),
     tdb_store(D, any, Ts);
+update({set,[D],[_Key,Map],{bif,map_get,_}}, Ts0) ->
+    Ts = tdb_meet(Map, map, Ts0),
+    tdb_store(D, any, Ts);
 update({set,[D],Args,{bif,N,_}}, Ts) ->
     Ar = length(Args),
     BoolOp = erl_internal:new_type_test(N, Ar) orelse
diff --git a/lib/compiler/src/cerl_trees.erl b/lib/compiler/src/cerl_trees.erl
index c7a129b42c..533c984221 100644
--- a/lib/compiler/src/cerl_trees.erl
+++ b/lib/compiler/src/cerl_trees.erl
@@ -351,10 +351,9 @@ mapfold(F, S0, T) ->
   mapfold(fun(T0, A) -> {T0, A} end, F, S0, T).
 
 
-%% @spec mapfold(Pre, Post, Initial::term(), Tree::cerl()) ->
-%%           {cerl(), term()}
-%%
-%%    Pre = Post = (cerl(), term()) -> {cerl(), term()}
+%% @spec mapfold(Pre, Post, Initial::term(), Tree::cerl()) -> {cerl(), term()}
+%%       Pre  = (cerl(), term()) -> {cerl(), term()}
+%%       Post = (cerl(), term()) -> {cerl(), term()}
 %%
 %% @doc Does a combined map/fold operation on the nodes of the
 %% tree. It begins by calling <code>Pre</code> on the tree, using the
diff --git a/lib/compiler/src/erl_bifs.erl b/lib/compiler/src/erl_bifs.erl
index 70b36f029e..a7452aebc8 100644
--- a/lib/compiler/src/erl_bifs.erl
+++ b/lib/compiler/src/erl_bifs.erl
@@ -94,6 +94,7 @@ is_pure(erlang, is_function, 1) -> true;
 is_pure(erlang, is_integer, 1) -> true;
 is_pure(erlang, is_list, 1) -> true;
 is_pure(erlang, is_map, 1) -> true;
+is_pure(erlang, is_map_key, 2) -> true;
 is_pure(erlang, is_number, 1) -> true;
 is_pure(erlang, is_pid, 1) -> true;
 is_pure(erlang, is_port, 1) -> true;
diff --git a/lib/compiler/src/v3_codegen.erl b/lib/compiler/src/v3_codegen.erl
index 8e73b613a0..9652a8476d 100644
--- a/lib/compiler/src/v3_codegen.erl
+++ b/lib/compiler/src/v3_codegen.erl
@@ -589,6 +589,7 @@ is_gc_bif(element, 2) -> false;
 is_gc_bif(get, 1) -> false;
 is_gc_bif(tuple_size, 1) -> false;
 is_gc_bif(map_get, 2) -> false;
+is_gc_bif(is_map_key, 2) -> false;
 is_gc_bif(Bif, Arity) ->
     not (erl_internal:bool_op(Bif, Arity) orelse
 	 erl_internal:new_type_test(Bif, Arity) orelse
@@ -1620,6 +1621,11 @@ test_cg(is_boolean, [#k_atom{val=Val}], Fail, I, Vdb, Bef, St) ->
 	     false -> [{jump,{f,Fail}}]
 	 end,
     {Is,Aft,St};
+test_cg(is_map_key, As, Fail, I, Vdb, Bef, St) ->
+    [Key,Map] = cg_reg_args(As, Bef),
+    Aft = clear_dead(Bef, I, Vdb),
+    F = {f,Fail},
+    {[{test,is_map,F,[Map]},{test,has_map_fields,F,Map,{list,[Key]}}],Aft,St};
 test_cg(Test, As, Fail, I, Vdb, Bef, St) ->
     Args = cg_reg_args(As, Bef),
     Aft = clear_dead(Bef, I, Vdb),