v3_core: Add is_map tests before map instructions

If we have a sequence of put_map_* instructions operating on the
same map, it will be more efficient if we can have one is_map/2
instruction before put_map_* instructions, so that each put_map_*
does not need to test whether the argument is a map.

4 files changed, 39 insertions, 49 deletions

diff --git a/lib/compiler/src/sys_core_fold.erl b/lib/compiler/src/sys_core_fold.erl
index 2618f7adba..ea1959d0f8 100644
--- a/lib/compiler/src/sys_core_fold.erl
+++ b/lib/compiler/src/sys_core_fold.erl
@@ -1603,6 +1603,7 @@ eval_case(#c_case{arg=E,clauses=[#c_clause{pats=Ps0,
 	    %% is correct, the clause will always match at run-time.
 	    Case;
 	{true,Bs} ->
+	    eval_case_warn(B),
 	    {Ps,As} = unzip(Bs),
 	    InnerLet = cerl:c_let(Ps, core_lib:make_values(As), B),
 	    Let = cerl:c_let(Vs, E, InnerLet),
@@ -1610,6 +1611,19 @@ eval_case(#c_case{arg=E,clauses=[#c_clause{pats=Ps0,
     end;
 eval_case(Case, _) -> Case.
 
+eval_case_warn(#c_primop{anno=Anno,
+			 name=#c_literal{val=match_fail},
+			 args=[#c_literal{val=Reason}]}=Core)
+  when is_atom(Reason) ->
+    case member(eval_failure, Anno) of
+	false ->
+	    ok;
+	true ->
+	    %% Example: M = not_map, M#{k:=v}
+	    add_warning(Core, {eval_failure,Reason})
+    end;
+eval_case_warn(_) -> ok.
+
 %% case_opt(CaseArg, [Clause]) -> {CaseArg,[Clause]}.
 %%  Try and optimise a case by avoid building tuples or lists
 %%  in the case expression. Instead combine the variable parts
diff --git a/lib/compiler/src/v3_core.erl b/lib/compiler/src/v3_core.erl
index 9478dc9579..cd44fb459b 100644
--- a/lib/compiler/src/v3_core.erl
+++ b/lib/compiler/src/v3_core.erl
@@ -758,30 +758,28 @@ make_bool_switch_guard(L, E, V, T, F) ->
       {clause,NegL,[V],[],[V]}
      ]}.
 
-expr_map(M0,Es0,A,St0) ->
-    {M1,Mps,St1} = safe(M0, St0),
+expr_map(M0, Es0, A, St0) ->
+    {M1,Eps0,St1} = safe(M0, St0),
     case is_valid_map_src(M1) of
 	true ->
-	    case {M1,Es0} of
-		{#c_var{}, []} ->
-		    %% transform M#{} to is_map(M)
-		    {Vpat,St2} = new_var(St1),
-		    {Fpat,St3} = new_var(St2),
-		    Cs = [#iclause{
-			   anno=A,
-			   pats=[Vpat],
-			   guard=[#icall{anno=#a{anno=A},
+	    {M2,Eps1,St2} = map_build_pairs(M1, Es0, A, St1),
+	    M3 = case Es0 of
+		     [] -> M1;
+		     [_|_] -> M2
+		 end,
+	    Cs = [#iclause{
+		     anno=#a{anno=[compiler_generated|A]},
+		     pats=[],
+		     guard=[#icall{anno=#a{anno=A},
 				   module=#c_literal{anno=A,val=erlang},
 			           name=#c_literal{anno=A,val=is_map},
-				   args=[Vpat]}],
-			   body=[Vpat]}],
-		    Fc = fail_clause([Fpat], A, #c_literal{val=badarg}),
-		    {#icase{anno=#a{anno=A},args=[M1],clauses=Cs,fc=Fc},Mps,St3};
-		{_,_} ->
-		    {M2,Eps,St2} = map_build_pairs(M1, Es0, A, St1),
-		    {M2,Mps++Eps,St2}
-	    end;
-	false -> throw({bad_map,bad_map})
+				   args=[M1]}],
+		     body=[M3]}],
+	    Fc = fail_clause([], [eval_failure|A], #c_literal{val=badarg}),
+	    Eps = Eps0 ++ Eps1,
+	    {#icase{anno=#a{anno=A},args=[],clauses=Cs,fc=Fc},Eps,St2};
+	false ->
+	    throw({bad_map,bad_map})
     end.
 
 map_build_pairs(Map, Es0, Ann, St0) ->
diff --git a/lib/compiler/src/v3_kernel.erl b/lib/compiler/src/v3_kernel.erl
index 08e84efc1b..0ac1aaf158 100644
--- a/lib/compiler/src/v3_kernel.erl
+++ b/lib/compiler/src/v3_kernel.erl
@@ -273,17 +273,7 @@ expr(#c_tuple{anno=A,es=Ces}, Sub, St0) ->
     {Kes,Ep,St1} = atomic_list(Ces, Sub, St0),
     {#k_tuple{anno=A,es=Kes},Ep,St1};
 expr(#c_map{anno=A,arg=Var,es=Ces}, Sub, St0) ->
-    try expr_map(A,Var,Ces,Sub,St0) of
-	{_,_,_}=Res -> Res
-    catch
-	throw:bad_map ->
-	    St1 = add_warning(get_line(A), bad_map, A, St0),
-	    Erl = #c_literal{val=erlang},
-	    Name = #c_literal{val=error},
-	    Args = [#c_literal{val=badarg}],
-	    Error = #c_call{anno=A,module=Erl,name=Name,args=Args},
-	    expr(Error, Sub, St1)
-    end;
+    expr_map(A, Var, Ces, Sub, St0);
 expr(#c_binary{anno=A,segments=Cv}, Sub, St0) ->
     try atomic_bin(Cv, Sub, St0) of
 	{Kv,Ep,St1} ->
@@ -506,19 +496,9 @@ translate_fc(Args) ->
     [#c_literal{val=function_clause},make_list(Args)].
 
 expr_map(A,Var0,Ces,Sub,St0) ->
-    %% An extra pass of validation of Map src because of inlining
     {Var,Mps,St1} = expr(Var0, Sub, St0),
-    case is_valid_map_src(Var) of
-	true ->
-	    {Km,Eps,St2} = map_split_pairs(A, Var, Ces, Sub, St1),
-	    {Km,Eps++Mps,St2};
-	false -> throw(bad_map)
-    end.
-
-is_valid_map_src(#k_map{}) -> true;
-is_valid_map_src(#k_literal{val=M}) when is_map(M) -> true;
-is_valid_map_src(#k_var{}) -> true;
-is_valid_map_src(_) -> false.
+    {Km,Eps,St2} = map_split_pairs(A, Var, Ces, Sub, St1),
+    {Km,Eps++Mps,St2}.
 
 map_split_pairs(A, Var, Ces, Sub, St0) ->
     %% 1. Force variables.
@@ -2024,9 +2004,7 @@ format_error(nomatch_shadow) ->
 format_error(bad_call) ->
     "invalid module and/or function name; this call will always fail";
 format_error(bad_segment_size) ->
-    "binary construction will fail because of a type mismatch";
-format_error(bad_map) ->
-    "map construction will fail because of a type mismatch".
+    "binary construction will fail because of a type mismatch".
 
 add_warning(none, Term, Anno, #kern{ws=Ws}=St) ->
     File = get_file(Anno),
diff --git a/lib/compiler/test/warnings_SUITE.erl b/lib/compiler/test/warnings_SUITE.erl
index 6663985ad7..dcd3910926 100644
--- a/lib/compiler/test/warnings_SUITE.erl
+++ b/lib/compiler/test/warnings_SUITE.erl
@@ -580,11 +580,11 @@ maps(Config) when is_list(Config) ->
            <<"
              t() ->
 		 M = {a,[]},
-		 {'EXIT',{badarg,_}} = (catch(M#{ a => 1})),
+		 {'EXIT',{badarg,_}} = (catch(M#{ a => 1 })),
 		 ok.
            ">>,
            [],
-	   {warnings,[{4,v3_kernel,bad_map}]}},
+	   {warnings,[{4,sys_core_fold,{eval_failure,badarg}}]}},
 	   {bad_map_src2,
            <<"
              t() ->
@@ -594,7 +594,7 @@ maps(Config) when is_list(Config) ->
 	     id(I) -> I.
            ">>,
 	   [inline],
-	   {warnings,[{4,v3_kernel,bad_map}]}},
+	    []},
 	   {bad_map_src3,
            <<"
              t() ->