From 541e87f3597523cb7d71f75fe0381fddb2af0ee0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Wed, 8 Apr 2015 07:14:17 +0200
Subject: debugger: Optimize evaluation of new map creation

Make sure that we recognize map literals at load time, as we
do for lists and tuples. Also use maps:from_list/1 to build
a new map instead of building it up from scratch inserting one
key/value pair at the time.
---
 lib/debugger/src/dbg_iload.erl | 26 +++++++++++++++++++++-----
 1 file changed, 21 insertions(+), 5 deletions(-)

(limited to 'lib/debugger/src/dbg_iload.erl')

diff --git a/lib/debugger/src/dbg_iload.erl b/lib/debugger/src/dbg_iload.erl
index d47d412893..379ffe8ce4 100644
--- a/lib/debugger/src/dbg_iload.erl
+++ b/lib/debugger/src/dbg_iload.erl
@@ -290,8 +290,7 @@ gexpr({tuple,Anno,Es0}) ->
     Es1 = gexpr_list(Es0),
     {tuple,ln(Anno),Es1};
 gexpr({map,Anno,Fs0}) ->
-    Fs1 = map_fields(Fs0, fun gexpr/1),
-    {map,ln(Anno),Fs1};
+    new_map(Fs0, Anno, fun gexpr/1);
 gexpr({map,Anno,E0,Fs0}) ->
     E1 = gexpr(E0),
     Fs1 = map_fields(Fs0, fun gexpr/1),
@@ -358,9 +357,8 @@ expr({cons,Anno,H0,T0}, _Lc) ->
 expr({tuple,Anno,Es0}, _Lc) ->
     Es1 = expr_list(Es0),
     {tuple,ln(Anno),Es1};
-expr({map,Anno,Fs0}, _Lc) ->
-    Fs1 = map_fields(Fs0),
-    {map,ln(Anno),Fs1};
+expr({map,Anno,Fs}, _Lc) ->
+    new_map(Fs, Anno, fun (E) -> expr(E, false) end);
 expr({map,Anno,E0,Fs0}, _Lc) ->
     E1 = expr(E0, false),
     Fs1 = map_fields(Fs0),
@@ -538,6 +536,24 @@ fun_clauses([{clause,A,H,G,B}|Cs]) ->
     [{clause,ln(A),head(H),guard(G),exprs(B, true)}|fun_clauses(Cs)];
 fun_clauses([]) -> [].
 
+
+new_map(Fs0, Anno, F) ->
+    Line = ln(Anno),
+    Fs1 = map_fields(Fs0, F),
+    Fs2 = [{ln(A),K,V} || {map_field_assoc,A,K,V} <- Fs1],
+    try
+	{value,Line,map_literal(Fs2, #{})}
+    catch
+	throw:not_literal ->
+	    {map,Line,Fs2}
+    end.
+
+map_literal([{_,{value,_,K},{value,_,V}}|T], M) ->
+    map_literal(T, maps:put(K, V, M));
+map_literal([_|_], _) ->
+    throw(not_literal);
+map_literal([], M) -> M.
+
 map_fields(Fs) ->
     map_fields(Fs, fun (E) -> expr(E, false) end).
 
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