2 files changed, 46 insertions, 27 deletions

diff --git a/erts/emulator/beam/beam_emu.c b/erts/emulator/beam/beam_emu.c
index ab5920a67e..aa61a2d7f9 100644
--- a/erts/emulator/beam/beam_emu.c
+++ b/erts/emulator/beam/beam_emu.c
@@ -3061,12 +3061,14 @@ erts_gc_update_map_exact(Process* p, Eterm* reg, Uint live, Uint n, Eterm* new_p
     Uint need;
     flatmap_t *old_mp, *mp;
     Eterm res;
+    Eterm* old_hp;
     Eterm* hp;
     Eterm* E;
     Eterm* old_keys;
     Eterm* old_vals;
     Eterm new_key;
     Eterm map;
+    int changed = 0;
 
     n /= 2;		/* Number of values to be updated */
     ASSERT(n > 0);
@@ -3133,6 +3135,7 @@ erts_gc_update_map_exact(Process* p, Eterm* reg, Uint live, Uint n, Eterm* new_p
      * Update map, keeping the old key tuple.
      */
 
+    old_hp = p->htop;
     hp = p->htop;
     E = p->stop;
 
@@ -3155,20 +3158,26 @@ erts_gc_update_map_exact(Process* p, Eterm* reg, Uint live, Uint n, Eterm* new_p
 	    /* Not same keys */
 	    *hp++ = *old_vals;
 	} else {
-	    GET_TERM(new_p[1], *hp);
-	    hp++;
-	    n--;
+            GET_TERM(new_p[1], *hp);
+            if(*hp != *old_vals) changed = 1;
+            hp++;
+            n--;
 	    if (n == 0) {
-		/*
-		 * All updates done. Copy remaining values
-		 * and return the result.
-		 */
-		for (i++, old_vals++; i < num_old; i++) {
-		    *hp++ = *old_vals++;
-		}
-		ASSERT(hp == p->htop + need);
-		p->htop = hp;
-		return res;
+                /*
+                * All updates done. Copy remaining values
+                * if any changed or return the original one.
+                */
+                if(changed) {
+		    for (i++, old_vals++; i < num_old; i++) {
+		        *hp++ = *old_vals++;
+		    }
+		    ASSERT(hp == p->htop + need);
+		    p->htop = hp;
+		    return res;
+                } else {
+                    p->htop = old_hp;
+                    return map;
+                }
 	    } else {
 		new_p += 2;
 		GET_TERM(*new_p, new_key);
diff --git a/erts/emulator/beam/erl_map.c b/erts/emulator/beam/erl_map.c
index 4a1fe4470e..3d6c9eb43f 100644
--- a/erts/emulator/beam/erl_map.c
+++ b/erts/emulator/beam/erl_map.c
@@ -1688,11 +1688,16 @@ int erts_maps_update(Process *p, Eterm key, Eterm value, Eterm map, Eterm *res)
 	return 0;
 
 found_key:
-	*hp++ = value;
-	vs++;
-	if (++i < n)
-	    sys_memcpy(hp, vs, (n - i)*sizeof(Eterm));
-	*res = make_flatmap(shp);
+        if(*vs == value) {
+            HRelease(p, shp + MAP_HEADER_FLATMAP_SZ + n, shp);
+            *res = map;
+        } else {
+	    *hp++ = value;
+	    vs++;
+	    if (++i < n)
+	       sys_memcpy(hp, vs, (n - i)*sizeof(Eterm));
+	    *res = make_flatmap(shp);
+        }
 	return 1;
     }
 
@@ -1748,9 +1753,7 @@ Eterm erts_maps_put(Process *p, Eterm key, Eterm value, Eterm map) {
 	if (is_immed(key)) {
 	    for( i = 0; i < n; i ++) {
 		if (ks[i] == key) {
-		    *hp++ = value;
-		    vs++;
-		    c = 1;
+                    goto found_key;
 		} else {
 		    *hp++ = *vs++;
 		}
@@ -1758,18 +1761,13 @@ Eterm erts_maps_put(Process *p, Eterm key, Eterm value, Eterm map) {
 	} else {
 	    for( i = 0; i < n; i ++) {
 		if (EQ(ks[i], key)) {
-		    *hp++ = value;
-		    vs++;
-		    c = 1;
+		    goto found_key;
 		} else {
 		    *hp++ = *vs++;
 		}
 	    }
 	}
 
-	if (c)
-	    return res;
-
 	/* the map will grow */
 
 	if (n >= MAP_SMALL_MAP_LIMIT) {
@@ -1824,6 +1822,18 @@ Eterm erts_maps_put(Process *p, Eterm key, Eterm value, Eterm map) {
 	 */
 	*shp = make_pos_bignum_header(0);
 	return res;
+
+found_key:
+        if(*vs == value) {
+            HRelease(p, shp + MAP_HEADER_FLATMAP_SZ + n, shp);
+            return map;
+        } else {
+            *hp++ = value;
+            vs++;
+            if (++i < n)
+               sys_memcpy(hp, vs, (n - i)*sizeof(Eterm));
+            return res;
+        }
     }
     ASSERT(is_hashmap(map));