From 80f9c7d0650330d53a3c457d85916447abe17194 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Tue, 10 Nov 2015 15:25:29 +0100
Subject: sys_core_dsetel: Use a map instead of a dict

For large modules, a map is significantly faster than a dict.
---
 lib/compiler/src/sys_core_dsetel.erl | 36 ++++++++++++++++++++----------------
 1 file changed, 20 insertions(+), 16 deletions(-)

(limited to 'lib/compiler/src/sys_core_dsetel.erl')

diff --git a/lib/compiler/src/sys_core_dsetel.erl b/lib/compiler/src/sys_core_dsetel.erl
index ac32db10fe..c6cfdbae7e 100644
--- a/lib/compiler/src/sys_core_dsetel.erl
+++ b/lib/compiler/src/sys_core_dsetel.erl
@@ -72,7 +72,7 @@ module(M0, _Options) ->
     {ok,M}.
 
 visit_module(#c_module{defs=Ds0}=R) ->
-    Env = dict:new(),
+    Env = #{},
     Ds = visit_module_1(Ds0, Env, []),
     R#c_module{defs=Ds}.
 
@@ -95,9 +95,11 @@ visit(Env, #c_var{name={_,_}}=R) ->
     {R, Env};
 visit(Env0, #c_var{name=X}=R) ->
     %% There should not be any free variables. If there are,
-    %% the next line will cause an exception.
-    {ok, N} = dict:find(X, Env0),
-    {R, dict:store(X, N+1, Env0)};
+    %% the case will fail with an exception.
+    case Env0 of
+	#{X:=N} ->
+	    {R, Env0#{X:=N+1}}
+    end;
 visit(Env, #c_literal{}=R) ->
     {R, Env};
 visit(Env0, #c_tuple{es=Es0}=R) ->
@@ -203,7 +205,7 @@ bind_vars(Vs, Env) ->
     bind_vars(Vs, Env, []).
 
 bind_vars([#c_var{name=X}|Vs], Env0, Xs)->
-    bind_vars(Vs, dict:store(X, 0, Env0), [X|Xs]);
+    bind_vars(Vs, Env0#{X=>0}, [X|Xs]);
 bind_vars([], Env,Xs) ->
     {Xs, Env}.
 
@@ -217,7 +219,7 @@ visit_pats([], Env, Vs) ->
     {Vs, Env}.
 
 visit_pat(Env0, #c_var{name=V}, Vs) ->
-    {[V|Vs], dict:store(V, 0, Env0)};
+    {[V|Vs], Env0#{V=>0}};
 visit_pat(Env0, #c_tuple{es=Es}, Vs) ->
     visit_pats(Es, Env0, Vs);
 visit_pat(Env0, #c_map{es=Es}, Vs) ->
@@ -235,23 +237,25 @@ visit_pat(Env0, #c_bitstr{val=Val,size=Sz}, Vs0) ->
 	case Sz of
 	    #c_var{name=V} ->
 		%% We don't tolerate free variables.
-		{ok, N} = dict:find(V, Env0),
-		{Vs0, dict:store(V, N+1, Env0)};
+		case Env0 of
+		    #{V:=N} ->
+			{Vs0, Env0#{V:=N+1}}
+		end;
 	    _ ->
 		visit_pat(Env0, Sz, Vs0)
 	end,
     visit_pat(Env1, Val, Vs1);
 visit_pat(Env0, #c_alias{pat=P,var=#c_var{name=V}}, Vs) ->
-    visit_pat(dict:store(V, 0, Env0), P, [V|Vs]);
+    visit_pat(Env0#{V=>0}, P, [V|Vs]);
 visit_pat(Env, #c_literal{}, Vs) ->
     {Vs, Env}.
 
 restore_vars([V|Vs], Env0, Env1) ->
-    case dict:find(V, Env0) of
-	{ok, N} ->
-	    restore_vars(Vs, Env0, dict:store(V, N, Env1));
-	error ->
-	    restore_vars(Vs, Env0, dict:erase(V, Env1))
+    case Env0 of
+	#{V:=N} ->
+	    restore_vars(Vs, Env0, Env1#{V=>N});
+	_ ->
+	    restore_vars(Vs, Env0, maps:remove(V, Env1))
     end;
 restore_vars([], _, Env1) ->
     Env1.
@@ -349,8 +353,8 @@ is_safe(#c_literal{}) -> true;
 is_safe(_) -> false.
 
 is_single_use(V, Env) ->
-    case dict:find(V, Env) of
-	{ok, 1} ->
+    case Env of
+	#{V:=1} ->
 	    true;
 	_ ->
 	    false
-- 
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