Merge branch 'egil/compiler/maps-fix-codegen'

* egil/compiler/maps-fix-codegen:
  compiler: Fix codegen multiple updates for Maps
  erts,compiler: Correct and amend tests for Maps

7 files changed, 156 insertions, 149 deletions

diff --git a/lib/compiler/src/v3_codegen.erl b/lib/compiler/src/v3_codegen.erl
index c8735a76e8..4d155c0fd0 100644
--- a/lib/compiler/src/v3_codegen.erl
+++ b/lib/compiler/src/v3_codegen.erl
@@ -459,7 +459,7 @@ basic_block([Le|Les], Acc) ->
 %% sets that may garbage collect are not allowed in basic blocks.
 	
 collect_block({set,_,{binary,_}})    -> no_block;
-collect_block({set,_,{map,_,_}})     -> no_block;
+collect_block({set,_,{map,_,_,_}})   -> no_block;
 collect_block({set,_,_})             -> include;
 collect_block({call,{var,_}=Var,As,_Rs}) -> {block_end,As++[Var]};
 collect_block({call,Func,As,_Rs})   -> {block_end,As++func_vars(Func)};
@@ -928,7 +928,7 @@ select_extract_tuple(Src, Vs, I, Vdb, Bef, St) ->
 select_map(Scs, V, Tf, Vf, Bef, St0) ->
     Reg = fetch_var(V, Bef),
     {Is,Aft,St1} =
-	match_fmf(fun(#l{ke={val_clause,{map,Es},B},i=I,vdb=Vdb}, Fail, St1) ->
+	match_fmf(fun(#l{ke={val_clause,{map,_,Es},B},i=I,vdb=Vdb}, Fail, St1) ->
 			  select_map_val(V, Es, B, Fail, I, Vdb, Bef, St1)
 		  end, Vf, St0, Scs),
     {[{test,is_map,{f,Tf},[Reg]}|Is],Aft,St1}.
@@ -1488,55 +1488,35 @@ set_cg([{var,R}], {binary,Segs}, Le, Vdb, Bef,
     %% Now generate the complete code for constructing the binary.
     Code = cg_binary(PutCode, Target, Temp, Fail, MaxRegs, Le#l.a),
     {Sis++Code,Aft,St};
-set_cg([{var,R}], {map,SrcMap,Es0}, Le, Vdb, Bef,
+set_cg([{var,R}], {map,Op,Map,Es}, Le, Vdb, Bef,
        #cg{in_catch=InCatch,bfail=Bfail}=St) ->
+
     Fail = {f,Bfail},
     {Sis,Int0} =
 	case InCatch of
 	    true -> adjust_stack(Bef, Le#l.i, Le#l.i+1, Vdb);
 	    false -> {[],Bef}
 	end,
+    SrcReg = cg_reg_arg(Map,Int0),
     Line = line(Le#l.a),
-    SrcReg = case SrcMap of
-		 {var,SrcVar} -> fetch_var(SrcVar, Int0);
-		 _ -> SrcMap
-	     end,
-    {Assoc,Exact} =
-	try
-	    cg_map_pairs(Es0)
-	catch
-	    throw:badarg ->
-		{[],[{{float,0.0},{atom,badarg}},
-		     {{integer,0},{atom,badarg}}]}
-	end,
-    F = fun ({K,{var,V}}) -> [K,fetch_var(V, Int0)];
-	    ({K,E}) -> [K,E]
-	end,
-    AssocList = flatmap(F, Assoc),
-    ExactList = flatmap(F, Exact),
-    Live0 = max_reg(Bef#sr.reg),
-    Int1 = clear_dead(Int0, Le#l.i, Vdb),
-    Aft = Bef#sr{reg=put_reg(R, Int1#sr.reg)},
-    Target = fetch_reg(R, Aft#sr.reg),
-    Code = [Line] ++
-	case {AssocList,ExactList} of
-	    {[_|_],[]} ->
-		[{put_map_assoc,Fail,SrcReg,Target,Live0,{list,AssocList}}];
-	    {[_|_],[_|_]} ->
-		Live = case Target of
-			   {x,TargetX} when TargetX =:= Live0 ->
-			       Live0 + 1;
-			   _ ->
-			       Live0
-		       end,
-		[{put_map_assoc,Fail,SrcReg,Target,Live0,{list,AssocList}},
-		 {put_map_exact,Fail,Target,Target,Live,{list,ExactList}}];
-	    {[],[_|_]} ->
-		[{put_map_exact,Fail,SrcReg,Target,Live0,{list,ExactList}}];
-	    {[],[]} ->
-		[{put_map_assoc,Fail,SrcReg,Target,Live0,{list,[]}}]
-	end,
-    {Sis++Code,Aft,St};
+
+    %% The instruction needs to store keys in term sorted order
+    %% All keys has to be unique here
+    Pairs = map_pair_strip_and_termsort(Es),
+
+    %% fetch registers for values to be put into the map
+    List = flatmap(fun({K,V}) -> [K,cg_reg_arg(V,Int0)] end, Pairs),
+
+    Live = max_reg(Bef#sr.reg),
+    Int1 = Int0#sr{reg=put_reg(R, Int0#sr.reg)},
+    Aft = clear_dead(Int1, Le#l.i, Vdb),
+    Target = fetch_reg(R, Int1#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};
 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)},
@@ -1549,70 +1529,12 @@ set_cg([{var,R}], Con, Le, Vdb, Bef, St) ->
 	  end,
     {Ais,clear_dead(Int, Le#l.i, Vdb),St}.
 
-%% cg_map_pairs(MapPairs) -> {Assoc,Exact}
-%%  Assoc = Exact = [{K,V}]
-%%
-%%  Remove multiple assignments to the same key, and return
-%%  one list key-value list with all keys that may or may not exist
-%%  (Assoc), and one with keys that must exist (Exact).
-%%
-
-cg_map_pairs(Es0) ->
-    Es = cg_map_pairs_1(Es0, 0),
-    R0 = sofs:relation(Es),
-    R1 = sofs:relation_to_family(R0),
-    R2 = sofs:to_external(R1),
-
-    %% R2 is now [{KeyValue,[{Order,Op,OriginalKey,Value}]}]
-    R3 = [begin
-	      %% The value for the last pair determines the value.
-	      {_,_,_,V} = lists:last(Vs),
-	      {Op,{_,SortOrder}=K} = map_pair_op_and_key(Vs),
-	      {Op,{SortOrder,K,V}}
-	  end || {_,Vs} <- R2],
-
-    %% R3 is now [{Op,{Key,Value}}]
-    R = termsort(R3),
-
-    %% R4 is now sorted with all alloc first in the list, followed by
-    %% all exact.
-    {Assoc,Exact} = lists:partition(fun({Op,_}) -> Op =:= assoc end, R),
-    {[{K,V} || {_,{_,K,V}} <- Assoc],
-     [{K,V} || {_,{_,K,V}} <- Exact]}.
-
-cg_map_pairs_1([{map_pair_assoc,{_,Kv}=K,V}|T], Order) ->
-    [{Kv,{Order,assoc,K,V}}|cg_map_pairs_1(T, Order+1)];
-cg_map_pairs_1([{map_pair_exact,{_,Kv}=K,V}|T], Order) ->
-    [{Kv,{Order,exact,K,V}}|cg_map_pairs_1(T, Order+1)];
-cg_map_pairs_1([], _) -> [].
-
-%% map_pair_op_and_key({_,Op,K,_}) -> {Operator,Key}
-%%  Determine the operator and key to use. Throw a 'badarg'
-%%  exception if there are contradictory exact updates.
-
-map_pair_op_and_key(L) ->
-    case [K || {_,exact,K,_} <- L] of
-	[K] ->
-	    %% There is a single ':=' operator. Use that key.
-	    {exact,K};
-	[K|T] ->
-	    %% There is more than one ':=' operator. All of them
-	    %% must have the same key.
-	    case lists:all(fun(E) -> E =:= K end, T) of
-		true ->
-		    {exact,K};
-		false ->
-		    %% Some keys are different, e.g. 1 and 1.0.
-		    throw(badarg)
-	    end;
-	[] ->
-	    %% Only '=>' operators. Use the first key in the list.
-	    [{_,assoc,K,_}|_] = L,
-	    {assoc,K}
-    end.
-
-termsort(Ls) ->
-    lists:sort(fun(A,B) -> erts_internal:cmp_term(A,B) < 0 end, Ls).
+map_pair_strip_and_termsort(Es) ->
+    %% format in
+    %%    [{map_pair,K,V}]
+    %% where K is for example {integer, 1} and we want to sort on 1.
+    Ls = [{K,V}||{_,K,V}<-Es],
+    lists:sort(fun({{_,A},_},{{_,B},_}) -> erts_internal:cmp_term(A,B) < 0 end, Ls).
 
 %%%
 %%% Code generation for constructing binaries.
@@ -2085,7 +2007,7 @@ load_vars(Vs, Regs) ->
     foldl(fun ({var,V}, Rs) -> put_reg(V, Rs) end, Regs, Vs).
 
 %% put_reg(Val, Regs) -> Regs.
-%% find_reg(Val, Regs) -> ok{r{R}} | error.
+%% find_reg(Val, Regs) -> {ok,r{R}} | error.
 %% fetch_reg(Val, Regs) -> r{R}.
 %%  Functions to interface the registers.
 
diff --git a/lib/compiler/src/v3_kernel.erl b/lib/compiler/src/v3_kernel.erl
index 6c8089e61d..bc5ca0314a 100644
--- a/lib/compiler/src/v3_kernel.erl
+++ b/lib/compiler/src/v3_kernel.erl
@@ -274,8 +274,7 @@ expr(#c_tuple{anno=A,es=Ces}, Sub, St0) ->
     {#k_tuple{anno=A,es=Kes},Ep,St1};
 expr(#c_map{anno=A,var=Var0,es=Ces}, Sub, St0) ->
     {Var,[],St1} = expr(Var0, Sub, St0),
-    {Kes,Ep,St2} = map_pairs(Ces, Sub, St1),
-    {#k_map{anno=A,var=Var,es=Kes},Ep,St2};
+    map_split_pairs(A, Var, Ces, Sub, St1);
 expr(#c_binary{anno=A,segments=Cv}, Sub, St0) ->
     try atomic_bin(Cv, Sub, St0) of
 	{Kv,Ep,St1} ->
@@ -497,15 +496,71 @@ translate_match_fail_1(Anno, As, Sub, #kern{ff=FF}) ->
 translate_fc(Args) ->
     [#c_literal{val=function_clause},make_list(Args)].
 
-%% FIXME: Not completed
-map_pairs(Es, Sub, St) ->
-    foldr(fun
-	    (#c_map_pair{op=#c_literal{val=Op},key=K0,val=V0}, {Kes,Esp,St0}) when
-                                           Op =:= assoc; Op =:= exact -> %% assert Op
-		{K,[],St1} = expr(K0, Sub, St0),
-		{V,Ep,St2} = atomic(V0, Sub, St1),
-		{[#k_map_pair{op=Op,key=K,val=V}|Kes],Ep ++ Esp,St2}
-	end, {[],[],St}, Es).
+    %{Kes,Ep,St2} = map_pairs(Ces, Sub, St1),
+map_split_pairs(A, Var, Ces, Sub, St0) ->
+    %% two steps
+    %% 1. force variables
+    %% 2. remove multiples
+    Pairs0 = [{Op,K,V} || #c_map_pair{op=#c_literal{val=Op},key=K,val=V} <- Ces],
+    {Pairs,Esp,St1} = foldr(fun
+	    ({Op,K0,V0}, {Ops,Espi,Sti0}) when Op =:= assoc; Op =:= exact ->
+		{K,[],Sti1} = expr(K0, Sub, Sti0),
+		{V,Ep,Sti2} = atomic(V0, Sub, Sti1),
+		{[{Op,K,V}|Ops],Ep ++ Espi,Sti2}
+	end, {[],[],St0}, Pairs0),
+
+    case map_group_pairs(Pairs) of
+	{Assoc,[]} ->
+	    Kes = [#k_map_pair{key=K,val=V}||{_,{assoc,K,V}} <- Assoc],
+	    {#k_map{anno=A,op=assoc,var=Var,es=Kes},Esp,St1};
+	{[],Exact} ->
+	    Kes = [#k_map_pair{key=K,val=V}||{_,{exact,K,V}} <- Exact],
+	    {#k_map{anno=A,op=exact,var=Var,es=Kes},Esp,St1};
+	{Assoc,Exact} ->
+	    Kes1 = [#k_map_pair{key=K,val=V}||{_,{assoc,K,V}} <- Assoc],
+	    {Mvar,Em,St2} = force_atomic(#k_map{anno=A,op=assoc,var=Var,es=Kes1},St1),
+	    Kes2 = [#k_map_pair{key=K,val=V}||{_,{exact,K,V}} <- Exact],
+	    {#k_map{anno=A,op=exact,var=Mvar,es=Kes2},Em ++ Esp,St2}
+
+    end.
+
+%% Group map by Assoc operations and Exact operations
+
+map_group_pairs(Es) ->
+    Groups = dict:to_list(map_group_pairs(Es,dict:new())),
+    partition(fun({_,{Op,_,_}}) -> Op =:= assoc end, Groups).
+
+map_group_pairs([{assoc,K,V}|Es0],Used0) ->
+    Used1 = case map_key_is_used(K,Used0) of
+	{ok, {assoc,_,_}} -> map_key_set_used(K,{assoc,K,V},Used0);
+	{ok, {exact,_,_}} -> map_key_set_used(K,{exact,K,V},Used0);
+	_                 -> map_key_set_used(K,{assoc,K,V},Used0)
+    end,
+    map_group_pairs(Es0,Used1);
+map_group_pairs([{exact,K,V}|Es0],Used0) ->
+    Used1 = case map_key_is_used(K,Used0) of
+	{ok, {assoc,_,_}} -> map_key_set_used(K,{assoc,K,V},Used0);
+	{ok, {exact,_,_}} -> map_key_set_used(K,{exact,K,V},Used0);
+	_                 -> map_key_set_used(K,{exact,K,V},Used0)
+    end,
+    map_group_pairs(Es0,Used1);
+map_group_pairs([],Used) ->
+    Used.
+
+map_key_set_used(K,How,Used) ->
+    dict:store(map_key_clean(K),How,Used).
+
+map_key_is_used(K,Used) ->
+    dict:find(map_key_clean(K),Used).
+
+%% Be explicit instead of using set_kanno(K,[])
+map_key_clean(#k_literal{val=V}) -> {k_literal,V};
+map_key_clean(#k_int{val=V})     -> {k_int,V};
+map_key_clean(#k_float{val=V})   -> {k_float,V};
+map_key_clean(#k_atom{val=V})    -> {k_atom,V};
+map_key_clean(#k_nil{})          -> k_nil;
+map_key_clean(#k_var{name=V})    -> {k_var,V}.
+
 
 %% call_type(Module, Function, Arity) -> call | bif | apply | error.
 %%  Classify the call.
@@ -664,11 +719,11 @@ pattern(#c_tuple{anno=A,es=Ces}, Isub, Osub0, St0) ->
     {#k_tuple{anno=A,es=Kes},Osub1,St1};
 pattern(#c_map{anno=A,es=Ces}, Isub, Osub0, St0) ->
     {Kes,Osub1,St1} = pattern_list(Ces, Isub, Osub0, St0),
-    {#k_map{anno=A,es=Kes},Osub1,St1};
+    {#k_map{anno=A,op=exact,es=Kes},Osub1,St1};
 pattern(#c_map_pair{op=#c_literal{val=exact},anno=A,key=Ck,val=Cv},Isub, Osub0, St0) ->
     {Kk,Osub1,St1} = pattern(Ck, Isub, Osub0, St0),
     {Kv,Osub2,St2} = pattern(Cv, Isub, Osub1, St1),
-    {#k_map_pair{anno=A,op=exact,key=Kk,val=Kv},Osub2,St2};
+    {#k_map_pair{anno=A,key=Kk,val=Kv},Osub2,St2};
 pattern(#c_binary{anno=A,segments=Cv}, Isub, Osub0, St0) ->
     {Kv,Osub1,St1} = pattern_bin(Cv, Isub, Osub0, St0),
     {#k_binary{anno=A,segs=Kv},Osub1,St1};
@@ -1356,9 +1411,8 @@ new_clauses(Cs0, U, St) ->
 				     [S,N|As];
 				 #k_bin_int{next=N} ->
 				     [N|As];
-				 #k_map{es=Es} ->
-				     Vals = [V ||
-						#k_map_pair{op=exact,val=V} <- Es],
+				 #k_map{op=exact,es=Es} ->
+				     Vals = [V || #k_map_pair{val=V} <- Es],
 				     Vals ++ As;
 				 _Other ->
 				     As
@@ -1458,9 +1512,9 @@ arg_val(Arg, C) ->
 		_ ->
 		    {set_kanno(S, []),U,T,Fs}
 	    end;
-	#k_map{es=Es} ->
+	#k_map{op=exact,es=Es} ->
 	    Keys = [begin
-			#k_map_pair{op=exact,key=#k_literal{val=Key}} = Pair,
+			#k_map_pair{key=#k_literal{val=Key}} = Pair,
 			Key
 		    end || Pair <- Es],
 	    %% multiple keys may have the same name
@@ -1876,7 +1930,7 @@ pat_vars(#k_tuple{es=Es}) ->
     pat_list_vars(Es);
 pat_vars(#k_map{es=Es}) ->
     pat_list_vars(Es);
-pat_vars(#k_map_pair{op=exact,val=V}) ->
+pat_vars(#k_map_pair{val=V}) ->
     pat_vars(V).
 
 pat_list_vars(Ps) ->
diff --git a/lib/compiler/src/v3_kernel.hrl b/lib/compiler/src/v3_kernel.hrl
index c7886a070d..ab66445f73 100644
--- a/lib/compiler/src/v3_kernel.hrl
+++ b/lib/compiler/src/v3_kernel.hrl
@@ -38,8 +38,8 @@
 -record(k_nil, {anno=[]}).
 
 -record(k_tuple, {anno=[],es}).
--record(k_map, {anno=[],var,es}).
--record(k_map_pair, {anno=[],op,key,val}).
+-record(k_map, {anno=[],var,op,es}).
+-record(k_map_pair, {anno=[],key,val}).
 -record(k_cons, {anno=[],hd,tl}).
 -record(k_binary, {anno=[],segs}).
 -record(k_bin_seg, {anno=[],size,unit,type,flags,seg,next}).
diff --git a/lib/compiler/src/v3_kernel_pp.erl b/lib/compiler/src/v3_kernel_pp.erl
index edbd3f74f8..639c6737e2 100644
--- a/lib/compiler/src/v3_kernel_pp.erl
+++ b/lib/compiler/src/v3_kernel_pp.erl
@@ -110,15 +110,18 @@ format_1(#k_map{var=#k_var{}=Var,es=Es}, Ctxt) ->
      " | ",format_1(Var, Ctxt),
      $},$~
     ];
-format_1(#k_map{es=Es}, Ctxt) ->
-    [$~,${,
+format_1(#k_map{op=assoc,es=Es}, Ctxt) ->
+    ["~{",
      format_hseq(Es, ",", ctxt_bump_indent(Ctxt, 1), fun format/2),
-     $},$~
+     "}~"
+    ];
+format_1(#k_map{op=exact,es=Es}, Ctxt) ->
+    ["::{",
+     format_hseq(Es, ",", ctxt_bump_indent(Ctxt, 1), fun format/2),
+     "}::"
     ];
-format_1(#k_map_pair{op=assoc,key=K,val=V}, Ctxt) ->
-    ["~<",format(K, Ctxt),",",format(V, Ctxt),">"];
-format_1(#k_map_pair{op=exact,key=K,val=V}, Ctxt) ->
-    ["::<",format(K, Ctxt),",",format(V, Ctxt),">"];
+format_1(#k_map_pair{key=K,val=V}, Ctxt) ->
+    ["<",format(K, Ctxt),",",format(V, Ctxt),">"];
 format_1(#k_binary{segs=S}, Ctxt) ->
     ["#<",format(S, ctxt_bump_indent(Ctxt, 2)),">#"];
 format_1(#k_bin_seg{next=Next}=S, Ctxt) ->
diff --git a/lib/compiler/src/v3_life.erl b/lib/compiler/src/v3_life.erl
index ae928e955c..c4f54a7970 100644
--- a/lib/compiler/src/v3_life.erl
+++ b/lib/compiler/src/v3_life.erl
@@ -367,12 +367,10 @@ literal(#k_bin_end{}, Ctxt) ->
     {bin_end,Ctxt};
 literal(#k_tuple{es=Es}, Ctxt) ->
     {tuple,literal_list(Es, Ctxt)};
-literal(#k_map{var=Var,es=Es}, Ctxt) ->
-    {map,literal(Var, Ctxt),literal_list(Es, Ctxt)};
-literal(#k_map_pair{op=assoc,key=K,val=V}, Ctxt) ->
-    {map_pair_assoc,literal(K, Ctxt),literal(V, Ctxt)};
-literal(#k_map_pair{op=exact,key=K,val=V}, Ctxt) ->
-    {map_pair_exact,literal(K, Ctxt),literal(V, Ctxt)};
+literal(#k_map{op=Op,var=Var,es=Es}, Ctxt) ->
+    {map,Op,literal(Var, Ctxt),literal_list(Es, Ctxt)};
+literal(#k_map_pair{key=K,val=V}, Ctxt) ->
+    {map_pair,literal(K, Ctxt),literal(V, Ctxt)};
 literal(#k_literal{val=V}, _Ctxt) ->
     {literal,V}.
 
@@ -402,8 +400,8 @@ literal2(#k_bin_end{}, Ctxt) ->
     {bin_end,Ctxt};
 literal2(#k_tuple{es=Es}, Ctxt) ->
     {tuple,literal_list2(Es, Ctxt)};
-literal2(#k_map{es=Es}, Ctxt) ->
-    {map,literal_list2(Es, Ctxt)};
+literal2(#k_map{op=Op,es=Es}, Ctxt) ->
+    {map,Op,literal_list2(Es, Ctxt)};
 literal2(#k_map_pair{key=K,val=V}, Ctxt) ->
     {map_pair,literal2(K, Ctxt),literal2(V, Ctxt)}.
 
diff --git a/lib/compiler/test/Makefile b/lib/compiler/test/Makefile
index 0a637a07cd..39c9fea5d9 100644
--- a/lib/compiler/test/Makefile
+++ b/lib/compiler/test/Makefile
@@ -48,6 +48,7 @@ NO_OPT= \
 	fun \
 	guard \
 	lc \
+	map \
 	match \
 	misc \
 	num_bif \
diff --git a/lib/compiler/test/map_SUITE.erl b/lib/compiler/test/map_SUITE.erl
index dc880a7a9d..bd514c60d0 100644
--- a/lib/compiler/test/map_SUITE.erl
+++ b/lib/compiler/test/map_SUITE.erl
@@ -38,10 +38,10 @@
 	%% not covered in 17.0-rc1
 	t_build_and_match_over_alloc/1,
 	t_build_and_match_empty_val/1,
-	t_build_and_match_val/1
+	t_build_and_match_val/1,
 
 	%% errors in 17.0-rc1
-
+	t_update_values/1
     ]).
 
 suite() -> [].
@@ -62,10 +62,10 @@ all() -> [
 	%% not covered in 17.0-rc1
 	t_build_and_match_over_alloc,
 	t_build_and_match_empty_val,
-	t_build_and_match_val
+	t_build_and_match_val,
 
 	%% errors in 17.0-rc1
-
+	t_update_values
     ].
 
 groups() -> [].
@@ -212,7 +212,14 @@ t_update_exact(Config) when is_list(Config) ->
     M2 = M0#{3.0:=new},
     #{1:=a,2:=b,3.0:=new,4:=d,5:=e} = M2,
     M2 = M0#{3.0=>wrong,3.0:=new},
-    M2 = M0#{3=>wrong,3.0:=new},
+    true = M2 =/= M0#{3=>right,3.0:=new},
+    #{ 3 := right, 3.0 := new } = M0#{3=>right,3.0:=new},
+
+    M3 = id(#{ 1 => val}),
+    #{1 := update2,1.0 := new_val4} = M3#{
+	1.0 => new_val1, 1 := update, 1=> update3,
+	1 := update2, 1.0 := new_val2, 1.0 => new_val3,
+	1.0 => new_val4 },
 
     %% Errors cases.
     {'EXIT',{badarg,_}} = (catch ((id(nil))#{ a := b })),
@@ -220,9 +227,31 @@ t_update_exact(Config) when is_list(Config) ->
     {'EXIT',{badarg,_}} = (catch M0#{1.0:=v,1.0=>v2}),
     {'EXIT',{badarg,_}} = (catch M0#{42.0:=v,42:=v2}),
     {'EXIT',{badarg,_}} = (catch M0#{42=>v1,42.0:=v2,42:=v3}),
+    ok.
 
+t_update_values(Config) when is_list(Config) ->
+    V0 = id(1337),
+    M0 = #{ a => 1, val => V0},
+    V1 = get_val(M0),
+    M1 = M0#{ val := [V0,V1], "wazzup" => 42 },
+    [1337, {some_val, 1337}] = get_val(M1),
+
+    N = 110,
+    List = [{[I,1,2,3,I],{1,2,3,"wat",I}}|| I <- lists:seq(1,N)],
+
+    {_,_,#{val2 := {1,2,3,"wat",N}, val1 := [N,1,2,3,N]}} = lists:foldl(fun
+	    ({V2,V3},{Old2,Old3,Mi}) ->
+		ok = check_val(Mi,Old2,Old3),
+		#{ val1 := Old2, val2 := Old3 } = Mi,
+		{V2,V3, Mi#{ val1 := id(V2), val2 := V1, val2 => id(V3)}}
+	end, {none, none, #{val1=>none,val2=>none}},List),
     ok.
 
+check_val(#{val1:=V1, val2:=V2},V1,V2) -> ok.
+
+get_val(#{ "wazzup" := _, val := V}) -> V;
+get_val(#{ val := V }) -> {some_val, V}.
+
 t_guard_bifs(Config) when is_list(Config) ->
     true   = map_guard_head(#{a=>1}),
     false  = map_guard_head([]),