Evaluate is_record/3 at compile-time using type information

1 files changed, 16 insertions, 0 deletions

diff --git a/lib/compiler/src/sys_core_fold.erl b/lib/compiler/src/sys_core_fold.erl
index 3e572d4b27..96015fbe58 100644
--- a/lib/compiler/src/sys_core_fold.erl
+++ b/lib/compiler/src/sys_core_fold.erl
@@ -1038,6 +1038,8 @@ fold_non_lit_args(Call, lists, append, [Arg1,Arg2], _) ->
     eval_append(Call, Arg1, Arg2);
 fold_non_lit_args(Call, erlang, setelement, [Arg1,Arg2,Arg3], _) ->
     eval_setelement(Call, Arg1, Arg2, Arg3);
+fold_non_lit_args(Call, erlang, is_record, [Arg1,Arg2,Arg3], Sub) ->
+    eval_is_record(Call, Arg1, Arg2, Arg3, Sub);
 fold_non_lit_args(Call, erlang, N, Args, Sub) ->
     NumArgs = length(Args),
     case erl_internal:comp_op(N, NumArgs) of
@@ -1218,6 +1220,20 @@ eval_element(Call, Pos, Tuple, _Types) ->
 	    Call
     end.
 
+%% eval_is_record(Call, Var, Tag, Size, Types) -> Val.
+%%  Evaluates is_record/3 using type information.
+%%
+eval_is_record(Call, #c_var{name=V}, #c_literal{val=NeededTag}=Lit,
+	       #c_literal{val=Size}, Types) ->
+    case orddict:find(V, Types#sub.t) of
+	{ok,#c_tuple{es=[#c_literal{val=Tag}|_]=Es}} ->
+	    Lit#c_literal{val=Tag =:= NeededTag andalso
+			  length(Es) =:= Size};
+	_ ->
+	    Call
+    end;
+eval_is_record(Call, _, _, _, _) -> Call.
+
 %% is_not_integer(Core) -> true | false.
 %%  Returns true if Core is definitely not an integer.