Merge branch 'egil/maps/refactor-tagscheme/OTP-12585'

* egil/maps/refactor-tagscheme/OTP-12585:
  erts: Refactor Map - use multiple values ESTACK_PUSHN
  erts: GC needs the size even if the frag is not referenced
  Revert "hipe: Handle separate hashmap tag correctly"
  erts: Combine flat and hash maps under one unifying tag

13 files changed, 359 insertions, 382 deletions

diff --git a/erts/emulator/beam/beam_emu.c b/erts/emulator/beam/beam_emu.c
index 6526e87e4c..8fcdc72895 100644
--- a/erts/emulator/beam/beam_emu.c
+++ b/erts/emulator/beam/beam_emu.c
@@ -6602,8 +6602,8 @@ new_map(Process* p, Eterm* reg, BeamInstr* I)
     keys   = make_tuple(thp);
     *thp++ = make_arityval(n/2);
 
-    mp = (flatmap_t *)mhp; mhp += MAP_HEADER_SIZE;
-    mp->thing_word = MAP_HEADER;
+    mp = (flatmap_t *)mhp; mhp += MAP_HEADER_FLATMAP_SZ;
+    mp->thing_word = MAP_HEADER_FLATMAP;
     mp->size = n/2;
     mp->keys = keys;
 
@@ -6684,7 +6684,7 @@ update_map_assoc(Process* p, Eterm* reg, Eterm map, BeamInstr* I)
      * update list are new).
      */
 
-    need = 2*(num_old+num_updates) + 1 + MAP_HEADER_SIZE;
+    need = 2*(num_old+num_updates) + 1 + MAP_HEADER_FLATMAP_SZ;
     if (HeapWordsLeft(p) < need) {
 	Uint live = Arg(3);
 	reg[live] = map;
@@ -6723,8 +6723,8 @@ update_map_assoc(Process* p, Eterm* reg, Eterm map, BeamInstr* I)
 
     res = make_flatmap(hp);
     mp = (flatmap_t *)hp;
-    hp += MAP_HEADER_SIZE;
-    mp->thing_word = MAP_HEADER;
+    hp += MAP_HEADER_FLATMAP_SZ;
+    mp->thing_word = MAP_HEADER_FLATMAP;
     mp->keys = make_tuple(kp-1);
 
     old_vals = flatmap_get_values(old_mp);
@@ -6906,7 +6906,7 @@ update_map_exact(Process* p, Eterm* reg, Eterm map, BeamInstr* I)
      * Allocate the exact heap space needed.
      */
 
-    need = num_old + MAP_HEADER_SIZE;
+    need = num_old + MAP_HEADER_FLATMAP_SZ;
     if (HeapWordsLeft(p) < need) {
 	Uint live = Arg(3);
 	reg[live] = map;
@@ -6927,8 +6927,8 @@ update_map_exact(Process* p, Eterm* reg, Eterm map, BeamInstr* I)
 
     res = make_flatmap(hp);
     mp = (flatmap_t *)hp;
-    hp += MAP_HEADER_SIZE;
-    mp->thing_word = MAP_HEADER;
+    hp += MAP_HEADER_FLATMAP_SZ;
+    mp->thing_word = MAP_HEADER_FLATMAP;
     mp->size = num_old;
     mp->keys = old_mp->keys;
 
diff --git a/erts/emulator/beam/copy.c b/erts/emulator/beam/copy.c
index 027b85b079..4d12dae787 100644
--- a/erts/emulator/beam/copy.c
+++ b/erts/emulator/beam/copy.c
@@ -127,8 +127,25 @@ Uint size_object(Eterm obj)
 			obj = *bptr;
 			break;
 		    }
-		case HASHMAP_SUBTAG:
+		case MAP_SUBTAG:
 		    switch (MAP_HEADER_TYPE(hdr)) {
+			case MAP_HEADER_TAG_FLATMAP_HEAD :
+                            {
+                                Uint n;
+                                flatmap_t *mp;
+                                mp  = (flatmap_t*)flatmap_val_rel(obj,base);
+                                ptr = (Eterm *)mp;
+                                n   = flatmap_get_size(mp) + 1;
+                                sum += n + 2;
+                                ptr += 2; /* hdr + size words */
+                                while (n--) {
+                                    obj = *ptr++;
+                                    if (!IS_CONST(obj)) {
+                                        ESTACK_PUSH(s, obj);
+                                    }
+                                }
+                                goto pop_next;
+                            }
 			case MAP_HEADER_TAG_HAMT_HEAD_BITMAP :
 			case MAP_HEADER_TAG_HAMT_HEAD_ARRAY :
 			case MAP_HEADER_TAG_HAMT_NODE_BITMAP :
@@ -183,25 +200,7 @@ Uint size_object(Eterm obj)
 			goto pop_next;
 		    }
 		    break;
-		case MAP_SUBTAG:
-		    {
-			Uint n;
-			flatmap_t *mp;
-			mp  = (flatmap_t*)flatmap_val_rel(obj,base);
-			ptr = (Eterm *)mp;
-			n   = flatmap_get_size(mp) + 1;
-			sum += n + 2;
-			ptr += 2; /* hdr + size words */
-			while (n--) {
-			    obj = *ptr++;
-			    if (!IS_CONST(obj)) {
-				ESTACK_PUSH(s, obj);
-			    }
-			}
-			goto pop_next;
-		    }
-		    break;
-		case BIN_MATCHSTATE_SUBTAG:
+                case BIN_MATCHSTATE_SUBTAG:
 		    erl_exit(ERTS_ABORT_EXIT,
 			     "size_object: matchstate term not allowed");
 		default:
@@ -369,15 +368,6 @@ Eterm copy_struct(Eterm obj, Uint sz, Eterm** hpp, ErlOffHeap* off_heap)
 		    }
 		}
 		break;
-	    case MAP_SUBTAG:
-		{
-		    i = flatmap_get_size(objp) + 3;
-		    *argp = make_flatmap_rel(htop, dst_base);
-		    while (i--) {
-			*htop++ = *objp++;
-		    }
-		}
-		break;
 	    case REFC_BINARY_SUBTAG:
 		{
 		    ProcBin* pb;
@@ -502,9 +492,16 @@ Eterm copy_struct(Eterm obj, Uint sz, Eterm** hpp, ErlOffHeap* off_heap)
 		  *argp = make_external_rel(tp, dst_base);
 		}
 		break;
-	    case HASHMAP_SUBTAG:
+	    case MAP_SUBTAG:
 		tp = htop;
 		switch (MAP_HEADER_TYPE(hdr)) {
+		    case MAP_HEADER_TAG_FLATMAP_HEAD :
+                        i = flatmap_get_size(objp) + 3;
+                        *argp = make_flatmap_rel(htop, dst_base);
+                        while (i--) {
+                            *htop++ = *objp++;
+                        }
+			break;
 		    case MAP_HEADER_TAG_HAMT_HEAD_BITMAP :
 		    case MAP_HEADER_TAG_HAMT_HEAD_ARRAY :
 			*htop++ = *objp++;
diff --git a/erts/emulator/beam/erl_db_util.c b/erts/emulator/beam/erl_db_util.c
index 9d699d4b22..0bf562d937 100644
--- a/erts/emulator/beam/erl_db_util.c
+++ b/erts/emulator/beam/erl_db_util.c
@@ -2153,16 +2153,16 @@ restart:
 	    break;
         case matchMkFlatMap:
             n = *pc++;
-            ehp = HAllocX(build_proc, 1 + MAP_HEADER_SIZE + n, HEAP_XTRA);
+            ehp = HAllocX(build_proc, 1 + MAP_HEADER_FLATMAP_SZ + n, HEAP_XTRA);
             t = *ehp++ = *--esp;
             {
                 flatmap_t *m = (flatmap_t *)ehp;
-                m->thing_word = MAP_HEADER;
+                m->thing_word = MAP_HEADER_FLATMAP;
                 m->size = n;
                 m->keys = t;
             }
             t = make_flatmap(ehp);
-            ehp += MAP_HEADER_SIZE;
+            ehp += MAP_HEADER_FLATMAP_SZ;
             while (n--) {
                 *ehp++ = *--esp;
             }
@@ -3540,14 +3540,10 @@ static DMCRet dmc_one_term(DMCContext *context,
 	    DMC_PUSH(*stack, c);
 	    break;
         case (_TAG_HEADER_MAP >> _TAG_PRIMARY_SIZE):
-            n = flatmap_get_size(flatmap_val(c));
-            DMC_PUSH(*text, matchPushM);
-            ++(context->stack_used);
-            DMC_PUSH(*text, n);
-            DMC_PUSH(*stack, c);
-            break;
-        case (_TAG_HEADER_HASHMAP >> _TAG_PRIMARY_SIZE):
-            n = hashmap_size(c);
+            if (is_flatmap(c))
+                n = flatmap_get_size(flatmap_val(c));
+            else
+                n = hashmap_size(c);
             DMC_PUSH(*text, matchPushM);
             ++(context->stack_used);
             DMC_PUSH(*text, n);
diff --git a/erts/emulator/beam/erl_gc.h b/erts/emulator/beam/erl_gc.h
index 8afcb060a1..bd6dcc9078 100644
--- a/erts/emulator/beam/erl_gc.h
+++ b/erts/emulator/beam/erl_gc.h
@@ -55,9 +55,10 @@ do {                                                                    \
     nelts = header_arity(HDR);                                          \
     switch ((HDR) & _HEADER_SUBTAG_MASK) {                              \
     case SUB_BINARY_SUBTAG: nelts++; break;                             \
-    case MAP_SUBTAG: nelts+=flatmap_get_size(PTR) + 1; break;               \
-    case HASHMAP_SUBTAG: nelts=hashmap_bitcount(MAP_HEADER_VAL(HDR));   \
-	 nelts += is_hashmap_header_head(HDR) ? 1 : 0; break;           \
+    case MAP_SUBTAG:                                                    \
+        if (is_flatmap_header(HDR)) nelts+=flatmap_get_size(PTR) + 1;   \
+        else nelts += hashmap_bitcount(MAP_HEADER_VAL(HDR));            \
+    break;                                                              \
     case FUN_SUBTAG: nelts+=((ErlFunThing*)(PTR))->num_free+1; break;   \
     }                                                                   \
     gval    = make_boxed(HTOP);                                         \
diff --git a/erts/emulator/beam/erl_map.c b/erts/emulator/beam/erl_map.c
index 35446501d4..ab40f47919 100644
--- a/erts/emulator/beam/erl_map.c
+++ b/erts/emulator/beam/erl_map.c
@@ -303,10 +303,10 @@ static Eterm flatmap_from_validated_list(Process *p, Eterm list, Uint size) {
     hp   += size;
     mp    = (flatmap_t*)hp;
     res   = make_flatmap(mp);
-    hp   += MAP_HEADER_SIZE;
+    hp   += MAP_HEADER_FLATMAP_SZ;
     vs    = hp;
 
-    mp->thing_word = MAP_HEADER;
+    mp->thing_word = MAP_HEADER_FLATMAP;
     mp->size = size; /* set later, might shrink*/
     mp->keys = keys;
 
@@ -438,10 +438,10 @@ static Eterm hashmap_from_validated_list(Process *p, Eterm list, Uint size) {
 	ks    = hp;
 	hp   += n;
 	mp    = (flatmap_t*)hp;
-	hp   += MAP_HEADER_SIZE;
+	hp   += MAP_HEADER_FLATMAP_SZ;
 	vs    = hp;
 
-	mp->thing_word = MAP_HEADER;
+	mp->thing_word = MAP_HEADER_FLATMAP;
 	mp->size = n;
 	mp->keys = keys;
 
@@ -710,8 +710,7 @@ static Eterm hashmap_from_chunked_array(ErtsHeapFactory *factory,
 	}
     }
 
-    ESTACK_PUSH(stack, res);
-    ESTACK_PUSH(stack, 1 << slot);
+    ESTACK_PUSH2(stack,res,1 << slot);
 
     /* all of the other nodes .. */
     elems = n - 2; /* remove first and last elements */
@@ -755,14 +754,12 @@ static Eterm hashmap_from_chunked_array(ErtsHeapFactory *factory,
 	    slot = maskval(v, d);
 	    bp   = 1 << slot;
 	    /* no more collisions */
-	    ESTACK_PUSH(stack,res);
-	    ESTACK_PUSH(stack,bp);
+            ESTACK_PUSH2(stack,res,bp);
 	} else if (d == dn) {
 	    /* no collisions at all */
 	    slot = maskval(v, d);
 	    bp   = 1 << slot;
-	    ESTACK_PUSH(stack,res);
-	    ESTACK_PUSH(stack,hdr | bp);
+            ESTACK_PUSH2(stack,res,hdr | bp);
 	} else {
 	    /* dn < n, we have a drop and we are done
 	     * build nodes and subtree */
@@ -786,8 +783,7 @@ static Eterm hashmap_from_chunked_array(ErtsHeapFactory *factory,
 		hdr = ESTACK_POP(stack);
 		d--;
 	    }
-	    ESTACK_PUSH(stack, res);
-	    ESTACK_PUSH(stack, hdr);
+            ESTACK_PUSH2(stack,res,hdr);
 	}
 
 	vp = v;
@@ -944,16 +940,16 @@ static Eterm flatmap_merge(Process *p, Eterm nodeA, Eterm nodeB) {
     n1   = flatmap_get_size(mp1);
     n2   = flatmap_get_size(mp2);
 
-    need = MAP_HEADER_SIZE + 1 + 2*(n1 + n2);
+    need = MAP_HEADER_FLATMAP_SZ + 1 + 2 * (n1 + n2);
 
     hp     = HAlloc(p, need);
     thp    = hp;
     tup    = make_tuple(thp);
     ks     = hp + 1; hp += 1 + n1 + n2;
-    mp_new = (flatmap_t*)hp; hp += MAP_HEADER_SIZE;
+    mp_new = (flatmap_t*)hp; hp += MAP_HEADER_FLATMAP_SZ;
     vs     = hp; hp += n1 + n2;
 
-    mp_new->thing_word = MAP_HEADER;
+    mp_new->thing_word = MAP_HEADER_FLATMAP;
     mp_new->size = 0;
     mp_new->keys = tup;
 
@@ -1008,6 +1004,7 @@ static Eterm flatmap_merge(Process *p, Eterm nodeA, Eterm nodeB) {
 
     n = n1 + n2 - unused_size;
     *thp = make_arityval(n);
+    mp_new->size = n;
 
     /* Reshape map to a hashmap if the map exceeds the limit */
 
@@ -1043,8 +1040,6 @@ static Eterm flatmap_merge(Process *p, Eterm nodeA, Eterm nodeB) {
 	return res;
     }
 
-    mp_new->size = n;
-
     return make_flatmap(mp_new);
 }
 
@@ -1344,12 +1339,12 @@ BIF_RETTYPE maps_new_0(BIF_ALIST_0) {
     Eterm tup;
     flatmap_t *mp;
 
-    hp    = HAlloc(BIF_P, (MAP_HEADER_SIZE + 1));
+    hp    = HAlloc(BIF_P, (MAP_HEADER_FLATMAP_SZ + 1));
     tup   = make_tuple(hp);
     *hp++ = make_arityval(0);
 
     mp    = (flatmap_t*)hp;
-    mp->thing_word = MAP_HEADER;
+    mp->thing_word = MAP_HEADER_FLATMAP;
     mp->size = 0;
     mp->keys = tup;
 
@@ -1401,7 +1396,7 @@ int erts_maps_remove(Process *p, Eterm key, Eterm map, Eterm *res) {
 	*thp++ = make_arityval(n - 1);
 
 	*res   = make_flatmap(mhp);
-	*mhp++ = MAP_HEADER;
+	*mhp++ = MAP_HEADER_FLATMAP;
 	*mhp++ = n - 1;
 	*mhp++ = tup;
 
@@ -1478,9 +1473,9 @@ int erts_maps_update(Process *p, Eterm key, Eterm value, Eterm map, Eterm *res)
 	 * assume key-tuple will be intact
 	 */
 
-	hp  = HAlloc(p, MAP_HEADER_SIZE + n);
+	hp  = HAlloc(p, MAP_HEADER_FLATMAP_SZ + n);
 	shp = hp;
-	*hp++ = MAP_HEADER;
+	*hp++ = MAP_HEADER_FLATMAP;
 	*hp++ = n;
 	*hp++ = mp->keys;
 
@@ -1502,7 +1497,7 @@ int erts_maps_update(Process *p, Eterm key, Eterm value, Eterm map, Eterm *res)
 	    }
 	}
 
-	HRelease(p, shp + MAP_HEADER_SIZE + n, shp);
+	HRelease(p, shp + MAP_HEADER_FLATMAP_SZ + n, shp);
 	return 0;
 
 found_key:
@@ -1536,12 +1531,12 @@ Eterm erts_maps_put(Process *p, Eterm key, Eterm value, Eterm map) {
 	n = flatmap_get_size(mp);
 
 	if (n == 0) {
-	    hp    = HAlloc(p, MAP_HEADER_SIZE + 1 + 2);
+	    hp    = HAlloc(p, MAP_HEADER_FLATMAP_SZ + 1 + 2);
 	    tup   = make_tuple(hp);
 	    *hp++ = make_arityval(1);
 	    *hp++ = key;
 	    res   = make_flatmap(hp);
-	    *hp++ = MAP_HEADER;
+	    *hp++ = MAP_HEADER_FLATMAP;
 	    *hp++ = 1;
 	    *hp++ = tup;
 	    *hp++ = value;
@@ -1556,10 +1551,10 @@ Eterm erts_maps_put(Process *p, Eterm key, Eterm value, Eterm map) {
 	 * assume key-tuple will be intact
 	 */
 
-	hp  = HAlloc(p, MAP_HEADER_SIZE + n);
+	hp  = HAlloc(p, MAP_HEADER_FLATMAP_SZ + n);
 	shp = hp; /* save hp, used if optimistic update fails */
 	res = make_flatmap(hp);
-	*hp++ = MAP_HEADER;
+	*hp++ = MAP_HEADER_FLATMAP;
 	*hp++ = n;
 	*hp++ = mp->keys;
 
@@ -1591,7 +1586,7 @@ Eterm erts_maps_put(Process *p, Eterm key, Eterm value, Eterm map) {
 	/* the map will grow */
 
 	if (n >= MAP_SMALL_MAP_LIMIT) {
-	    HRelease(p, shp + MAP_HEADER_SIZE + n, shp);
+	    HRelease(p, shp + MAP_HEADER_FLATMAP_SZ + n, shp);
 	    ks = flatmap_get_keys(mp);
 	    vs = flatmap_get_values(mp);
 
@@ -1608,7 +1603,7 @@ Eterm erts_maps_put(Process *p, Eterm key, Eterm value, Eterm map) {
 
 	hp    = HAlloc(p, 3 + n + 1);
 	res   = make_flatmap(hp);
-	*hp++ = MAP_HEADER;
+	*hp++ = MAP_HEADER_FLATMAP;
 	*hp++ = n + 1;
 	*hp++ = tup;
 
@@ -1946,8 +1941,7 @@ int erts_hashmap_insert_down(Uint32 hx, Eterm key, Eterm node, Uint *sz,
 			slot = hashmap_bitcount(hval & (bp - 1));
 			n    = hashmap_bitcount(hval);
 
-			ESTACK_PUSH(*sp, n);
-			ESTACK_PUSH3(*sp, bp, slot, node);
+			ESTACK_PUSH4(*sp, n, bp, slot, node);
 
 			/* occupied */
 			if (bp & hval) {
@@ -1970,8 +1964,7 @@ int erts_hashmap_insert_down(Uint32 hx, Eterm key, Eterm node, Uint *sz,
 			slot = hashmap_bitcount(hval & (bp - 1));
 			n    = hashmap_bitcount(hval);
 
-			ESTACK_PUSH(*sp, n);
-			ESTACK_PUSH3(*sp, bp, slot, node);
+			ESTACK_PUSH4(*sp, n, bp, slot, node);
 
 			/* occupied */
 			if (bp & hval) {
@@ -2005,8 +1998,7 @@ insert_subnodes:
     cix   = hashmap_index(chx);
 
     while (cix == ix) {
-	ESTACK_PUSH(*sp, 0);
-	ESTACK_PUSH3(*sp, 1 << ix, 0, MAP_HEADER_HAMT_NODE_BITMAP(0));
+	ESTACK_PUSH4(*sp, 0, 1 << ix, 0, MAP_HEADER_HAMT_NODE_BITMAP(0));
 	size += HAMT_NODE_BITMAP_SZ(1);
 	hx    = hashmap_shift_hash(th,hx,lvl,key);
 	chx   = hashmap_shift_hash(th,chx,clvl,ckey);
@@ -2194,8 +2186,7 @@ static Eterm hashmap_delete(Process *p, Uint32 hx, Eterm key, Eterm map) {
 			slot = hashmap_bitcount(hval & (bp - 1));
 			n    = hashmap_bitcount(hval);
 
-			ESTACK_PUSH(stack, n);
-			ESTACK_PUSH3(stack, bp, slot, node);
+			ESTACK_PUSH4(stack, n, bp, slot, node);
 
 			/* occupied */
 			if (bp & hval) {
@@ -2214,8 +2205,7 @@ static Eterm hashmap_delete(Process *p, Uint32 hx, Eterm key, Eterm map) {
 			slot = hashmap_bitcount(hval & (bp - 1));
 			n    = hashmap_bitcount(hval);
 
-			ESTACK_PUSH(stack, n);
-			ESTACK_PUSH3(stack, bp, slot, node);
+			ESTACK_PUSH4(stack, n, bp, slot, node);
 
 			/* occupied */
 			if (bp & hval) {
@@ -2258,10 +2248,10 @@ unroll:
 	ks    = hp;
 	hp   += n;
 	mp    = (flatmap_t*)hp;
-	hp   += MAP_HEADER_SIZE;
+	hp   += MAP_HEADER_FLATMAP_SZ;
 	vs    = hp;
 
-	mp->thing_word = MAP_HEADER;
+	mp->thing_word = MAP_HEADER_FLATMAP;
 	mp->size = n;
 	mp->keys = keys;
 
diff --git a/erts/emulator/beam/erl_map.h b/erts/emulator/beam/erl_map.h
index 9fc1a72b68..2cc6768bfc 100644
--- a/erts/emulator/beam/erl_map.h
+++ b/erts/emulator/beam/erl_map.h
@@ -55,9 +55,9 @@ typedef struct flatmap_s {
 /* the head-node is a bitmap or array with an untagged size */
 
 
-#define hashmap_size(x) (((hashmap_head_t*) hashmap_val(x))->size)
+#define hashmap_size(x)               (((hashmap_head_t*) hashmap_val(x))->size)
 #define hashmap_size_rel(RTERM, BASE) hashmap_size(rterm2wterm(RTERM, BASE))
-#define hashmap_make_hash(Key) make_internal_hash(Key)
+#define hashmap_make_hash(Key)        make_internal_hash(Key)
 
 #define hashmap_restore_hash(Heap,Lvl,Key) \
     (((Lvl) < 8) ? hashmap_make_hash(Key) >> (4*(Lvl)) : hashmap_make_hash(CONS(Heap, make_small((Lvl)>>3), (Key))) >> (4*((Lvl) & 7)))
@@ -66,27 +66,15 @@ typedef struct flatmap_s {
 
 
 /* erl_term.h stuff */
-#define make_flatmap(x)		make_boxed((Eterm*)(x))
-#define make_flatmap_rel(x, BASE)   make_boxed_rel((Eterm*)(x),(BASE))
-#define is_flatmap(x)		(is_boxed((x)) && is_flatmap_header(*boxed_val((x))))
-#define is_flatmap_rel(RTERM,BASE)  is_flatmap(rterm2wterm(RTERM,BASE))
-#define is_not_flatmap(x)           (!is_flatmap((x)))
-#define is_flatmap_header(x)	(((x) & (_TAG_HEADER_MASK)) == _TAG_HEADER_MAP)
-#define header_is_flatmap(x)        ((((x) & (_HEADER_SUBTAG_MASK)) == MAP_SUBTAG))
-#define flatmap_val(x)		(_unchecked_boxed_val((x)))
-#define flatmap_val_rel(RTERM, BASE) flatmap_val(rterm2wterm(RTERM, BASE))
-
-#define flatmap_get_values(x)      (((Eterm *)(x)) + 3)
-#define flatmap_get_keys(x)        (((Eterm *)tuple_val(((flatmap_t *)(x))->keys)) + 1)
-#define flatmap_get_size(x)        (((flatmap_t*)(x))->size)
+#define flatmap_get_values(x)        (((Eterm *)(x)) + 3)
+#define flatmap_get_keys(x)          (((Eterm *)tuple_val(((flatmap_t *)(x))->keys)) + 1)
+#define flatmap_get_size(x)          (((flatmap_t*)(x))->size)
 
 #ifdef DEBUG
 #define MAP_SMALL_MAP_LIMIT    (3)
 #else
 #define MAP_SMALL_MAP_LIMIT    (32)
 #endif
-#define MAP_HEADER             _make_header(1,_TAG_HEADER_MAP)
-#define MAP_HEADER_SIZE        (sizeof(flatmap_t) / sizeof(Eterm))
 
 struct ErtsWStack_;
 struct ErtsEStack_;
@@ -170,7 +158,10 @@ typedef struct hashmap_head_s {
 #define is_hashmap_header_head(x) ((MAP_HEADER_TYPE(x) & (0x2)))
 
 #define MAKE_MAP_HEADER(Type,Arity,Val) \
-    (_make_header(((((Uint16)(Val)) << MAP_HEADER_ARITY_SZ) | (Arity)) << MAP_HEADER_TAG_SZ | (Type) , _TAG_HEADER_HASHMAP))
+    (_make_header(((((Uint16)(Val)) << MAP_HEADER_ARITY_SZ) | (Arity)) << MAP_HEADER_TAG_SZ | (Type) , _TAG_HEADER_MAP))
+
+#define MAP_HEADER_FLATMAP \
+    MAKE_MAP_HEADER(MAP_HEADER_TAG_FLATMAP_HEAD,0x1,0x0)
 
 #define MAP_HEADER_HAMT_HEAD_ARRAY \
     MAKE_MAP_HEADER(MAP_HEADER_TAG_HAMT_HEAD_ARRAY,0x1,0xffff)
@@ -181,15 +172,22 @@ typedef struct hashmap_head_s {
 #define MAP_HEADER_HAMT_NODE_BITMAP(Bmp) \
     MAKE_MAP_HEADER(MAP_HEADER_TAG_HAMT_NODE_BITMAP,0x0,Bmp)
 
-#define HAMT_HEAD_EMPTY_SZ     (2)
-#define HAMT_HEAD_ARRAY_SZ     (18)
-#define HAMT_NODE_BITMAP_SZ(n) (1 + n)
-#define HAMT_HEAD_BITMAP_SZ(n) (2 + n)
+#define MAP_HEADER_FLATMAP_SZ  (sizeof(flatmap_t) / sizeof(Eterm))
+
+#define HAMT_NODE_ARRAY_SZ      (17)
+#define HAMT_HEAD_ARRAY_SZ      (18)
+#define HAMT_NODE_BITMAP_SZ(n)  (1 + n)
+#define HAMT_HEAD_BITMAP_SZ(n)  (2 + n)
+
+/* 2 bits maps tag + 4 bits subtag + 2 ignore bits */
+#define _HEADER_MAP_SUBTAG_MASK       (0xfc)
+/* 1 bit map tag + 1 ignore bit + 4 bits subtag + 2 ignore bits */
+#define _HEADER_MAP_HASHMAP_HEAD_MASK (0xbc)
 
-#define _HEADER_MAP_SUBTAG_MASK    (0xfc) /* 2 bits maps tag + 4 bits subtag + 2 ignore bits */
-#define HAMT_SUBTAG_NODE_BITMAP  ((MAP_HEADER_TAG_HAMT_NODE_BITMAP << _HEADER_ARITY_OFFS) | HASHMAP_SUBTAG)
-#define HAMT_SUBTAG_HEAD_ARRAY   ((MAP_HEADER_TAG_HAMT_HEAD_ARRAY << _HEADER_ARITY_OFFS) | HASHMAP_SUBTAG)
-#define HAMT_SUBTAG_HEAD_BITMAP  ((MAP_HEADER_TAG_HAMT_HEAD_BITMAP << _HEADER_ARITY_OFFS) | HASHMAP_SUBTAG)
+#define HAMT_SUBTAG_NODE_BITMAP  ((MAP_HEADER_TAG_HAMT_NODE_BITMAP << _HEADER_ARITY_OFFS) | MAP_SUBTAG)
+#define HAMT_SUBTAG_HEAD_ARRAY   ((MAP_HEADER_TAG_HAMT_HEAD_ARRAY  << _HEADER_ARITY_OFFS) | MAP_SUBTAG)
+#define HAMT_SUBTAG_HEAD_BITMAP  ((MAP_HEADER_TAG_HAMT_HEAD_BITMAP << _HEADER_ARITY_OFFS) | MAP_SUBTAG)
+#define HAMT_SUBTAG_HEAD_FLATMAP ((MAP_HEADER_TAG_FLATMAP_HEAD << _HEADER_ARITY_OFFS) | MAP_SUBTAG)
 
 #define hashmap_index(hash)      (((Uint32)hash) & 0xf)
 
diff --git a/erts/emulator/beam/erl_nif.c b/erts/emulator/beam/erl_nif.c
index c7c8b3fee3..660f446a52 100644
--- a/erts/emulator/beam/erl_nif.c
+++ b/erts/emulator/beam/erl_nif.c
@@ -1926,14 +1926,14 @@ int enif_get_map_size(ErlNifEnv* env, ERL_NIF_TERM term, size_t *size)
 
 ERL_NIF_TERM enif_make_new_map(ErlNifEnv* env)
 {
-    Eterm* hp = alloc_heap(env,MAP_HEADER_SIZE+1);
+    Eterm* hp = alloc_heap(env,MAP_HEADER_FLATMAP_SZ+1);
     Eterm tup;
     flatmap_t *mp;
 
     tup   = make_tuple(hp);
     *hp++ = make_arityval(0);
     mp    = (flatmap_t*)hp;
-    mp->thing_word = MAP_HEADER;
+    mp->thing_word = MAP_HEADER_FLATMAP;
     mp->size = 0;
     mp->keys = tup;
 
diff --git a/erts/emulator/beam/erl_printf_term.c b/erts/emulator/beam/erl_printf_term.c
index ac5b139f8d..e0dfbd31b8 100644
--- a/erts/emulator/beam/erl_printf_term.c
+++ b/erts/emulator/beam/erl_printf_term.c
@@ -565,77 +565,74 @@ print_term(fmtfn_t fn, void* arg, Eterm obj, long *dcount,
 	    }
 	    break;
 	case MAP_DEF:
-	    {
-		Uint n;
-		Eterm *ks, *vs;
-		flatmap_t *mp = (flatmap_t *)flatmap_val(wobj);
-		n  = flatmap_get_size(mp);
-		ks = flatmap_get_keys(mp);
-		vs = flatmap_get_values(mp);
-
-		PRINT_CHAR(res, fn, arg, '#');
-		PRINT_CHAR(res, fn, arg, '{');
-		WSTACK_PUSH(s, PRT_CLOSE_TUPLE);
-		if (n > 0) {
-		    n--;
-		    WSTACK_PUSH5(s, vs[n], PRT_TERM, PRT_ASSOC, ks[n], PRT_TERM);
-		    while (n--) {
-			WSTACK_PUSH6(s, PRT_COMMA, vs[n], PRT_TERM, PRT_ASSOC,
-				     ks[n], PRT_TERM);
-		    }
-		}
-	    }
-	    break;
-	case HASHMAP_DEF:
-	    {
-		Uint n,mapval;
-		Eterm *head;
-		head = hashmap_val(wobj);
-		mapval = MAP_HEADER_VAL(*head);
-		switch (MAP_HEADER_TYPE(*head)) {
-		    case MAP_HEADER_TAG_HAMT_HEAD_ARRAY:
-		    case MAP_HEADER_TAG_HAMT_HEAD_BITMAP:
-			PRINT_STRING(res, fn, arg, "#<");
-			PRINT_UWORD(res, fn, arg, 'x', 0, 1, mapval);
-			PRINT_STRING(res, fn, arg, ">{");
-			WSTACK_PUSH(s,PRT_CLOSE_TUPLE);
-			n = hashmap_bitcount(mapval);
-			ASSERT(n < 17);
-			head += 2;
-			if (n > 0) {
-			    n--;
-			    WSTACK_PUSH(s, head[n]);
-			    WSTACK_PUSH(s, PRT_TERM);
-			    while (n--) {
-				WSTACK_PUSH(s, PRT_COMMA);
-				WSTACK_PUSH(s, head[n]);
-				WSTACK_PUSH(s, PRT_TERM);
-			    }
-			}
-			break;
-		    case MAP_HEADER_TAG_HAMT_NODE_BITMAP:
-			n = hashmap_bitcount(mapval);
-			head++;
-			PRINT_CHAR(res, fn, arg, '<');
-			PRINT_UWORD(res, fn, arg, 'x', 0, 1, mapval);
-			PRINT_STRING(res, fn, arg, ">{");
-			WSTACK_PUSH(s,PRT_CLOSE_TUPLE);
-			ASSERT(n < 17);
-			if (n > 0) {
-			    n--;
-			    WSTACK_PUSH(s, head[n]);
-			    WSTACK_PUSH(s, PRT_TERM);
-			    while (n--) {
-				WSTACK_PUSH(s, PRT_COMMA);
-				WSTACK_PUSH(s, head[n]);
-				WSTACK_PUSH(s, PRT_TERM);
-			    }
-			}
-			break;
-		}
-	    }
-	    break;
-	default:
+            if (is_flatmap(wobj)) {
+                Uint n;
+                Eterm *ks, *vs;
+                flatmap_t *mp = (flatmap_t *)flatmap_val(wobj);
+                n  = flatmap_get_size(mp);
+                ks = flatmap_get_keys(mp);
+                vs = flatmap_get_values(mp);
+
+                PRINT_CHAR(res, fn, arg, '#');
+                PRINT_CHAR(res, fn, arg, '{');
+                WSTACK_PUSH(s, PRT_CLOSE_TUPLE);
+                if (n > 0) {
+                    n--;
+                    WSTACK_PUSH5(s, vs[n], PRT_TERM, PRT_ASSOC, ks[n], PRT_TERM);
+                    while (n--) {
+                        WSTACK_PUSH6(s, PRT_COMMA, vs[n], PRT_TERM, PRT_ASSOC,
+                                ks[n], PRT_TERM);
+                    }
+                }
+            } else {
+                Uint n, mapval;
+                Eterm *head;
+                head = hashmap_val(wobj);
+                mapval = MAP_HEADER_VAL(*head);
+                switch (MAP_HEADER_TYPE(*head)) {
+                case MAP_HEADER_TAG_HAMT_HEAD_ARRAY:
+                case MAP_HEADER_TAG_HAMT_HEAD_BITMAP:
+                    PRINT_STRING(res, fn, arg, "#<");
+                    PRINT_UWORD(res, fn, arg, 'x', 0, 1, mapval);
+                    PRINT_STRING(res, fn, arg, ">{");
+                    WSTACK_PUSH(s,PRT_CLOSE_TUPLE);
+                    n = hashmap_bitcount(mapval);
+                    ASSERT(n < 17);
+                    head += 2;
+                    if (n > 0) {
+                        n--;
+                        WSTACK_PUSH(s, head[n]);
+                        WSTACK_PUSH(s, PRT_TERM);
+                        while (n--) {
+                            WSTACK_PUSH(s, PRT_COMMA);
+                            WSTACK_PUSH(s, head[n]);
+                            WSTACK_PUSH(s, PRT_TERM);
+                        }
+                    }
+                    break;
+                case MAP_HEADER_TAG_HAMT_NODE_BITMAP:
+                    n = hashmap_bitcount(mapval);
+                    head++;
+                    PRINT_CHAR(res, fn, arg, '<');
+                    PRINT_UWORD(res, fn, arg, 'x', 0, 1, mapval);
+                    PRINT_STRING(res, fn, arg, ">{");
+                    WSTACK_PUSH(s,PRT_CLOSE_TUPLE);
+                    ASSERT(n < 17);
+                    if (n > 0) {
+                        n--;
+                        WSTACK_PUSH(s, head[n]);
+                        WSTACK_PUSH(s, PRT_TERM);
+                        while (n--) {
+                            WSTACK_PUSH(s, PRT_COMMA);
+                            WSTACK_PUSH(s, head[n]);
+                            WSTACK_PUSH(s, PRT_TERM);
+                        }
+                    }
+                    break;
+                }
+            }
+            break;
+        default:
 	    PRINT_STRING(res, fn, arg, "<unknown:");
 	    PRINT_POINTER(res, fn, arg, wobj);
 	    PRINT_CHAR(res, fn, arg, '>');
diff --git a/erts/emulator/beam/erl_term.c b/erts/emulator/beam/erl_term.c
index d6fb88ea61..bc04d7b78e 100644
--- a/erts/emulator/beam/erl_term.c
+++ b/erts/emulator/beam/erl_term.c
@@ -90,7 +90,6 @@ unsigned tag_val_def(Wterm x)
 	    case (_TAG_HEADER_REFC_BIN >> _TAG_PRIMARY_SIZE):	return BINARY_DEF;
 	    case (_TAG_HEADER_HEAP_BIN >> _TAG_PRIMARY_SIZE):	return BINARY_DEF;
 	    case (_TAG_HEADER_SUB_BIN >> _TAG_PRIMARY_SIZE):	return BINARY_DEF;
-	    case (_TAG_HEADER_HASHMAP >> _TAG_PRIMARY_SIZE):	return HASHMAP_DEF;
 	  }
  
 	  break;
diff --git a/erts/emulator/beam/erl_term.h b/erts/emulator/beam/erl_term.h
index 1625a4ec15..095aa54ddd 100644
--- a/erts/emulator/beam/erl_term.h
+++ b/erts/emulator/beam/erl_term.h
@@ -141,29 +141,27 @@ struct erl_node_; /* Declared in erl_node_tables.h */
 #define HEAP_BINARY_SUBTAG	(0x9 << _TAG_PRIMARY_SIZE) /* BINARY */
 #define SUB_BINARY_SUBTAG	(0xA << _TAG_PRIMARY_SIZE) /* BINARY */
 /*   _BINARY_XXX_MASK depends on 0xB being unused */
-#define HASHMAP_SUBTAG		(0xB << _TAG_PRIMARY_SIZE) /* HASHMAP */
 #define EXTERNAL_PID_SUBTAG	(0xC << _TAG_PRIMARY_SIZE) /* EXTERNAL_PID */
 #define EXTERNAL_PORT_SUBTAG	(0xD << _TAG_PRIMARY_SIZE) /* EXTERNAL_PORT */
 #define EXTERNAL_REF_SUBTAG	(0xE << _TAG_PRIMARY_SIZE) /* EXTERNAL_REF */
 #define MAP_SUBTAG		(0xF << _TAG_PRIMARY_SIZE) /* MAP */
 
 
-#define _TAG_HEADER_ARITYVAL	(TAG_PRIMARY_HEADER|ARITYVAL_SUBTAG)
-#define _TAG_HEADER_FUN		(TAG_PRIMARY_HEADER|FUN_SUBTAG)
-#define _TAG_HEADER_POS_BIG	(TAG_PRIMARY_HEADER|POS_BIG_SUBTAG)
-#define _TAG_HEADER_NEG_BIG	(TAG_PRIMARY_HEADER|NEG_BIG_SUBTAG)
-#define _TAG_HEADER_FLOAT	(TAG_PRIMARY_HEADER|FLOAT_SUBTAG)
-#define _TAG_HEADER_EXPORT	(TAG_PRIMARY_HEADER|EXPORT_SUBTAG)
-#define _TAG_HEADER_REF		(TAG_PRIMARY_HEADER|REF_SUBTAG)
-#define _TAG_HEADER_REFC_BIN	(TAG_PRIMARY_HEADER|REFC_BINARY_SUBTAG)
-#define _TAG_HEADER_HEAP_BIN	(TAG_PRIMARY_HEADER|HEAP_BINARY_SUBTAG)
-#define _TAG_HEADER_SUB_BIN	(TAG_PRIMARY_HEADER|SUB_BINARY_SUBTAG)
-#define _TAG_HEADER_EXTERNAL_PID  (TAG_PRIMARY_HEADER|EXTERNAL_PID_SUBTAG)
-#define _TAG_HEADER_EXTERNAL_PORT (TAG_PRIMARY_HEADER|EXTERNAL_PORT_SUBTAG)
-#define _TAG_HEADER_EXTERNAL_REF  (TAG_PRIMARY_HEADER|EXTERNAL_REF_SUBTAG)
+#define _TAG_HEADER_ARITYVAL       (TAG_PRIMARY_HEADER|ARITYVAL_SUBTAG)
+#define _TAG_HEADER_FUN	           (TAG_PRIMARY_HEADER|FUN_SUBTAG)
+#define _TAG_HEADER_POS_BIG        (TAG_PRIMARY_HEADER|POS_BIG_SUBTAG)
+#define _TAG_HEADER_NEG_BIG        (TAG_PRIMARY_HEADER|NEG_BIG_SUBTAG)
+#define _TAG_HEADER_FLOAT          (TAG_PRIMARY_HEADER|FLOAT_SUBTAG)
+#define _TAG_HEADER_EXPORT         (TAG_PRIMARY_HEADER|EXPORT_SUBTAG)
+#define _TAG_HEADER_REF            (TAG_PRIMARY_HEADER|REF_SUBTAG)
+#define _TAG_HEADER_REFC_BIN       (TAG_PRIMARY_HEADER|REFC_BINARY_SUBTAG)
+#define _TAG_HEADER_HEAP_BIN       (TAG_PRIMARY_HEADER|HEAP_BINARY_SUBTAG)
+#define _TAG_HEADER_SUB_BIN        (TAG_PRIMARY_HEADER|SUB_BINARY_SUBTAG)
+#define _TAG_HEADER_EXTERNAL_PID   (TAG_PRIMARY_HEADER|EXTERNAL_PID_SUBTAG)
+#define _TAG_HEADER_EXTERNAL_PORT  (TAG_PRIMARY_HEADER|EXTERNAL_PORT_SUBTAG)
+#define _TAG_HEADER_EXTERNAL_REF   (TAG_PRIMARY_HEADER|EXTERNAL_REF_SUBTAG)
 #define _TAG_HEADER_BIN_MATCHSTATE (TAG_PRIMARY_HEADER|BIN_MATCHSTATE_SUBTAG)
-#define _TAG_HEADER_MAP	 	(TAG_PRIMARY_HEADER|MAP_SUBTAG)
-#define _TAG_HEADER_HASHMAP	(TAG_PRIMARY_HEADER|HASHMAP_SUBTAG)
+#define _TAG_HEADER_MAP	           (TAG_PRIMARY_HEADER|MAP_SUBTAG)
 
 
 #define _TAG_HEADER_MASK	0x3F
@@ -302,7 +300,7 @@ _ET_DECLARE_CHECKED(Uint,atom_val,Eterm)
 #define is_header(x)	(((x) & _TAG_PRIMARY_MASK) == TAG_PRIMARY_HEADER)
 //#define _unchecked_header_arity(x)	((x) >> _HEADER_ARITY_OFFS)
 #define _unchecked_header_arity(x) \
-    (is_hashmap_header(x) ? MAP_HEADER_ARITY(x) : ((x) >> _HEADER_ARITY_OFFS))
+    (is_map_header(x) ? MAP_HEADER_ARITY(x) : ((x) >> _HEADER_ARITY_OFFS))
 _ET_DECLARE_CHECKED(Uint,header_arity,Eterm)
 #define header_arity(x)	_ET_APPLY(header_arity,(x))
 
@@ -1001,7 +999,7 @@ _ET_DECLARE_CHECKED(struct erl_node_*,external_ref_node,Eterm)
 #define MAP_HEADER_ARITY_SZ               (8)
 #define MAP_HEADER_VAL_SZ                 (16)
 
-#define MAP_HEADER_TAG_FLAT               (0x0)
+#define MAP_HEADER_TAG_FLATMAP_HEAD       (0x0)
 #define MAP_HEADER_TAG_HAMT_NODE_BITMAP   (0x1)
 #define MAP_HEADER_TAG_HAMT_HEAD_ARRAY    (0x2)
 #define MAP_HEADER_TAG_HAMT_HEAD_BITMAP   (0x3)
@@ -1010,17 +1008,27 @@ _ET_DECLARE_CHECKED(struct erl_node_*,external_ref_node,Eterm)
 #define MAP_HEADER_ARITY(Hdr) (((Hdr) >> (_HEADER_ARITY_OFFS + MAP_HEADER_TAG_SZ)) & (0xff))
 #define MAP_HEADER_VAL(Hdr)   (((Hdr) >> (_HEADER_ARITY_OFFS + MAP_HEADER_TAG_SZ + MAP_HEADER_ARITY_SZ)) & (0xffff))
 
-#define make_hashmap(x)		make_boxed((Eterm*)(x))
-#define make_hashmap_rel 	make_boxed_rel
-#define is_hashmap(x)		(is_boxed((x)) && is_hashmap_header(*boxed_val((x))))
-#define is_not_hashmap(x)       (!is_hashmap(x))
-#define is_hashmap_rel(RTERM,BASE)  is_hashmap(rterm2wterm(RTERM,BASE))
-#define is_hashmap_header(x)	(((x) & (_TAG_HEADER_MASK)) == _TAG_HEADER_HASHMAP)
-#define hashmap_val(x)		_unchecked_boxed_val((x))
-#define hashmap_val_rel(RTERM, BASE) hashmap_val(rterm2wterm(RTERM, BASE))
-
-#define is_map(x)            (is_flatmap(x) || is_hashmap(x))
-#define is_map_rel(x,BASE)   (is_flatmap_rel(x,BASE) || is_hashmap_rel(x,BASE))
+#define make_hashmap(x)		      make_boxed((Eterm*)(x))
+#define make_hashmap_rel 	      make_boxed_rel
+#define is_hashmap(x)		      (is_boxed((x)) && is_hashmap_header(*boxed_val((x))))
+#define is_not_hashmap(x)             (!is_hashmap(x))
+#define is_hashmap_rel(RTERM,BASE)    is_hashmap(rterm2wterm(RTERM,BASE))
+#define is_hashmap_header(x)	      (((x) & (_HEADER_MAP_HASHMAP_HEAD_MASK)) == HAMT_SUBTAG_HEAD_ARRAY)
+#define hashmap_val(x)		      _unchecked_boxed_val((x))
+#define hashmap_val_rel(RTERM, BASE)  hashmap_val(rterm2wterm(RTERM, BASE))
+
+#define make_flatmap(x)               make_boxed((Eterm*)(x))
+#define make_flatmap_rel(x, BASE)     make_boxed_rel((Eterm*)(x),(BASE))
+#define is_flatmap(x)                 (is_boxed((x)) && is_flatmap_header(*boxed_val((x))))
+#define is_flatmap_rel(RTERM,BASE)    is_flatmap(rterm2wterm(RTERM,BASE))
+#define is_not_flatmap(x)             (!is_flatmap((x)))
+#define is_flatmap_header(x)          (((x) & (_HEADER_MAP_SUBTAG_MASK)) == HAMT_SUBTAG_HEAD_FLATMAP)
+#define flatmap_val(x)                (_unchecked_boxed_val((x)))
+#define flatmap_val_rel(RTERM, BASE)  flatmap_val(rterm2wterm(RTERM, BASE))
+
+#define is_map_header(x)       (((x) & (_TAG_HEADER_MASK)) == _TAG_HEADER_MAP)
+#define is_map(x)              (is_boxed((x)) && is_map_header(*boxed_val(x)))
+#define is_map_rel(RTERM,BASE) is_map(rterm2wterm(RTERM,BASE))
 
 /* number tests */
 
@@ -1113,23 +1121,22 @@ _ET_DECLARE_CHECKED(Uint,y_reg_index,Uint)
 #define BINARY_DEF		0x0
 #define LIST_DEF		0x1
 #define NIL_DEF			0x2
-#define HASHMAP_DEF		0x3
-#define MAP_DEF			0x4
-#define TUPLE_DEF		0x5
-#define PID_DEF			0x6
-#define EXTERNAL_PID_DEF	0x7
-#define PORT_DEF		0x8
-#define EXTERNAL_PORT_DEF	0x9
-#define EXPORT_DEF		0xa
-#define FUN_DEF			0xb
-#define REF_DEF			0xc
-#define EXTERNAL_REF_DEF	0xd
-#define ATOM_DEF		0xe
-#define FLOAT_DEF		0xf
-#define BIG_DEF			0x10
-#define SMALL_DEF		0x11
-
-#define FIRST_VACANT_TAG_DEF    0x12
+#define MAP_DEF			0x3
+#define TUPLE_DEF		0x4
+#define PID_DEF			0x5
+#define EXTERNAL_PID_DEF	0x6
+#define PORT_DEF		0x7
+#define EXTERNAL_PORT_DEF	0x8
+#define EXPORT_DEF		0x9
+#define FUN_DEF			0xa
+#define REF_DEF			0xb
+#define EXTERNAL_REF_DEF	0xc
+#define ATOM_DEF		0xd
+#define FLOAT_DEF		0xe
+#define BIG_DEF			0xf
+#define SMALL_DEF		0x10
+
+#define FIRST_VACANT_TAG_DEF    0x11
 
 #if ET_DEBUG
 extern unsigned tag_val_def_debug(Wterm, const char*, unsigned);
diff --git a/erts/emulator/beam/external.c b/erts/emulator/beam/external.c
index b0b232f185..2a9189b51e 100644
--- a/erts/emulator/beam/external.c
+++ b/erts/emulator/beam/external.c
@@ -2604,7 +2604,7 @@ enc_term_int(TTBEncodeContext* ctx, ErtsAtomCacheMap *acmp, Eterm obj, byte* ep,
 	    break;
 
 	case MAP_DEF:
-	    {
+	    if (is_flatmap(obj)) {
 		flatmap_t *mp = (flatmap_t*)flatmap_val(obj);
 		Uint size = flatmap_get_size(mp);
 
@@ -2618,11 +2618,7 @@ enc_term_int(TTBEncodeContext* ctx, ErtsAtomCacheMap *acmp, Eterm obj, byte* ep,
 		    WSTACK_PUSH4(s, (UWord)kptr, (UWord)vptr,
 				 ENC_MAP_PAIR, size);
 		}
-	    }
-	    break;
-
-	case HASHMAP_DEF:
-	    {
+	    } else {
 		Eterm hdr;
 		Uint node_sz;
 		ptr = boxed_val(obj);
@@ -2656,7 +2652,6 @@ enc_term_int(TTBEncodeContext* ctx, ErtsAtomCacheMap *acmp, Eterm obj, byte* ep,
 		}
 	    }
 	    break;
-
 	case FLOAT_DEF:
 	    GET_DOUBLE(obj, f);
 	    if (dflags & DFLAG_NEW_FLOATS) {
@@ -3607,7 +3602,7 @@ dec_term_atom_common:
                     kptr = hp - 1;
 
                     mp    = (flatmap_t*)hp;
-                    hp   += MAP_HEADER_SIZE;
+                    hp   += MAP_HEADER_FLATMAP_SZ;
                     hp   += size;
                     vptr = hp - 1;
 
@@ -3893,7 +3888,7 @@ dec_term_atom_common:
 
     while (maps_list) {
 	next  = (Eterm *)(EXPAND_POINTER(*maps_list));
-	*maps_list = MAP_HEADER;
+	*maps_list = MAP_HEADER_FLATMAP;
 	if (!erts_validate_and_sort_flatmap((flatmap_t*)maps_list))
 	    goto error;
 	maps_list  = next;
@@ -4121,7 +4116,7 @@ encode_size_struct_int(TTBSizeContext* ctx, ErtsAtomCacheMap *acmp, Eterm obj,
 	    }
 	    break;
 	case MAP_DEF:
-	    {
+	    if (is_flatmap(obj)) {
 		flatmap_t *mp = (flatmap_t*)flatmap_val(obj);
 		Uint size = flatmap_get_size(mp);
 		Uint i;
@@ -4158,11 +4153,7 @@ encode_size_struct_int(TTBSizeContext* ctx, ErtsAtomCacheMap *acmp, Eterm obj,
 		    ++ptr;
 		}
 		goto outer_loop;
-	    }
-	    break;
-
-	case HASHMAP_DEF:
-	    {
+	    } else {
 		Eterm *ptr;
 		Eterm hdr;
 		Uint node_sz;
@@ -4190,7 +4181,6 @@ encode_size_struct_int(TTBSizeContext* ctx, ErtsAtomCacheMap *acmp, Eterm obj,
 		}
 		result += 1 + 4; /* tag + 4 bytes size */
 	    }
-
 	    break;
 	case FLOAT_DEF:
 	    if (dflags & DFLAG_NEW_FLOATS) {
diff --git a/erts/emulator/beam/io.c b/erts/emulator/beam/io.c
index 46f0eba5e0..1db3a9fba7 100644
--- a/erts/emulator/beam/io.c
+++ b/erts/emulator/beam/io.c
@@ -5354,7 +5354,7 @@ driver_deliver_term(Eterm to, ErlDrvTermData* data, int len)
             if (ptr[0] > MAP_SMALL_MAP_LIMIT) {
                 need += hashmap_over_estimated_heap_size(ptr[0]);
             } else {
-                need += MAP_HEADER_SIZE + 1 + 2*ptr[0];
+                need += MAP_HEADER_FLATMAP_SZ + 1 + 2*ptr[0];
             }
 	    depth -= 2*ptr[0];
 	    if (depth < 0) ERTS_DDT_FAIL;
@@ -5627,12 +5627,12 @@ driver_deliver_term(Eterm to, ErlDrvTermData* data, int len)
 
                 hp += 1 + size;
                 mp = (flatmap_t*)hp;
-                mp->thing_word = MAP_HEADER;
+                mp->thing_word = MAP_HEADER_FLATMAP;
                 mp->size = size;
                 mp->keys = make_tuple(tp);
                 mess = make_flatmap(mp);
 
-                hp += MAP_HEADER_SIZE + size;   /* advance "heap" pointer */
+                hp += MAP_HEADER_FLATMAP_SZ + size;
 
                 tp += size;    /* point at last key */
                 vp = hp - 1;   /* point at last value */
diff --git a/erts/emulator/beam/utils.c b/erts/emulator/beam/utils.c
index 6edb466a36..cb4ef2b376 100644
--- a/erts/emulator/beam/utils.c
+++ b/erts/emulator/beam/utils.c
@@ -1025,11 +1025,8 @@ tail_recur:
 	    break;
 	}	
     case MAP_DEF:
-    case HASHMAP_DEF:
-	{
-	    hash = hash*FUNNY_NUMBER13 + FUNNY_NUMBER14 + make_hash2(term);
-	    break;
-	}
+        hash = hash*FUNNY_NUMBER13 + FUNNY_NUMBER14 + make_hash2(term);
+        break;
     case TUPLE_DEF: 
 	{
 	    Eterm* ptr = tuple_val(term);
@@ -1273,41 +1270,40 @@ make_hash2(Eterm term)
 		}
 	    }
 	    break;
-	    case MAP_SUBTAG:
-	    {
-		flatmap_t *mp = (flatmap_t *)flatmap_val(term);
-		int i;
-		int size  = flatmap_get_size(mp);
-		Eterm *ks = flatmap_get_keys(mp);
-		Eterm *vs = flatmap_get_values(mp);
-		UINT32_HASH(size, HCONST_16);
-		if (size == 0) {
-		    goto hash2_common;
-		}
-		/* We want a portable hash function that is *independent* of
-		 * the order in which keys and values are encountered.
-		 * We therefore calculate context independent hashes for all    				      .
-		 * key-value pairs and then xor them together.
-		 */
-		ESTACK_PUSH(s, hash_xor_pairs);
-		ESTACK_PUSH(s, hash);
-		ESTACK_PUSH(s, HASH_MAP_TAIL);
-		hash = 0;
-		hash_xor_pairs = 0;
-		for (i = size - 1; i >= 0; i--) {
-		    ESTACK_PUSH(s, HASH_MAP_PAIR);
-		    ESTACK_PUSH(s, vs[i]);
-                    ESTACK_PUSH(s, ks[i]);
-		}
-		goto hash2_common;
-	    }
-	    break;
-            case HASHMAP_SUBTAG:
+            case MAP_SUBTAG:
             {
                 Eterm* ptr = boxed_val(term) + 1;
                 Uint size;
                 int i;
                 switch (hdr & _HEADER_MAP_SUBTAG_MASK) {
+                case HAMT_SUBTAG_HEAD_FLATMAP:
+                {
+                    flatmap_t *mp = (flatmap_t *)flatmap_val(term);
+                    Eterm *ks = flatmap_get_keys(mp);
+                    Eterm *vs = flatmap_get_values(mp);
+                    size      = flatmap_get_size(mp);
+                    UINT32_HASH(size, HCONST_16);
+                    if (size == 0)
+                        goto hash2_common;
+
+                    /* We want a portable hash function that is *independent* of
+                     * the order in which keys and values are encountered.
+                     * We therefore calculate context independent hashes for all    				      .
+                     * key-value pairs and then xor them together.
+                     */
+                    ESTACK_PUSH(s, hash_xor_pairs);
+                    ESTACK_PUSH(s, hash);
+                    ESTACK_PUSH(s, HASH_MAP_TAIL);
+                    hash = 0;
+                    hash_xor_pairs = 0;
+                    for (i = size - 1; i >= 0; i--) {
+                        ESTACK_PUSH(s, HASH_MAP_PAIR);
+                        ESTACK_PUSH(s, vs[i]);
+                        ESTACK_PUSH(s, ks[i]);
+                    }
+                    goto hash2_common;
+                }
+
                 case HAMT_SUBTAG_HEAD_ARRAY:
                 case HAMT_SUBTAG_HEAD_BITMAP:
                     size = *ptr++;
@@ -1675,42 +1671,40 @@ make_internal_hash(Eterm term)
 		}
 	    }
 	    break;
-	    case MAP_SUBTAG:
-	    {
-		flatmap_t *mp = (flatmap_t *)flatmap_val(term);
-		int i;
-		int size  = flatmap_get_size(mp);
-		Eterm *ks = flatmap_get_keys(mp);
-		Eterm *vs = flatmap_get_values(mp);
-		UINT32_HASH(size, HCONST_16);
-		if (size == 0) {
-		    goto pop_next;
-		}
-		/* We want a hash function that is *independent* of
-		 * the order in which keys and values are encountered.
-		 * We therefore calculate context independent hashes for all    				      .
-		 * key-value pairs and then xor them together.
-		 */
-		ESTACK_PUSH(s, hash_xor_pairs);
-		ESTACK_PUSH(s, hash);
-		ESTACK_PUSH(s, HASH_MAP_TAIL);
-		hash = 0;
-		hash_xor_pairs = 0;
-		for (i = size - 1; i >= 0; i--) {
-		    ESTACK_PUSH(s, HASH_MAP_PAIR);
-		    ESTACK_PUSH(s, vs[i]);
-                    ESTACK_PUSH(s, ks[i]);
-		}
-		goto pop_next;
-	    }
-	    break;
-            case HASHMAP_SUBTAG:
+
+            case MAP_SUBTAG:
             {
                 Eterm* ptr = boxed_val(term) + 1;
                 Uint size;
                 int i;
                 switch (hdr & _HEADER_MAP_SUBTAG_MASK) {
-                case HAMT_SUBTAG_HEAD_ARRAY:
+                case HAMT_SUBTAG_HEAD_FLATMAP:
+                {
+                    flatmap_t *mp = (flatmap_t *)flatmap_val(term);
+                    Eterm *ks = flatmap_get_keys(mp);
+                    Eterm *vs = flatmap_get_values(mp);
+                    size      = flatmap_get_size(mp);
+                    UINT32_HASH(size, HCONST_16);
+                    if (size == 0)
+                        goto pop_next;
+
+                    /* We want a hash function that is *independent* of
+                     * the order in which keys and values are encountered.
+                     * We therefore calculate context independent hashes for all    				      .
+                     * key-value pairs and then xor them together.
+                     */
+                    ESTACK_PUSH(s, hash_xor_pairs);
+                    ESTACK_PUSH(s, hash);
+                    ESTACK_PUSH(s, HASH_MAP_TAIL);
+                    hash = 0;
+                    hash_xor_pairs = 0;
+                    for (i = size - 1; i >= 0; i--) {
+                        ESTACK_PUSH(s, HASH_MAP_PAIR);
+                        ESTACK_PUSH(s, vs[i]);
+                        ESTACK_PUSH(s, ks[i]);
+                    }
+                    goto pop_next;
+                }
                 case HAMT_SUBTAG_HEAD_BITMAP:
                     size = *ptr++;
                     UINT32_HASH(size, HCONST_16);
@@ -2170,11 +2164,8 @@ tail_recur:
 	break;
 
     case MAP_DEF:
-    case HASHMAP_DEF:
-	{
-	    hash = hash*FUNNY_NUMBER13 + FUNNY_NUMBER14 + make_hash2(term);
-	    break;
-	}
+        hash = hash*FUNNY_NUMBER13 + FUNNY_NUMBER14 + make_hash2(term);
+        break;
     case TUPLE_DEF: 
 	{
 	    Eterm* ptr = tuple_val(term);
@@ -2579,22 +2570,6 @@ tailrecur_ne:
 		    ++bb;
 		    goto term_array;
 		}
-	    case MAP_SUBTAG:
-		{
-		    aa = flatmap_val_rel(a, a_base);
-		    if (!is_boxed(b) || *boxed_val_rel(b,b_base) != *aa)
-			goto not_equal;
-		    bb = flatmap_val_rel(b,b_base);
-		    sz = flatmap_get_size((flatmap_t*)aa);
-
-		    if (sz != flatmap_get_size((flatmap_t*)bb)) goto not_equal;
-		    if (sz == 0) goto pop_next;
-
-		    aa += 2;
-		    bb += 2;
-		    sz += 1; /* increment for tuple-keys */
-		    goto term_array;
-		}
 	    case REFC_BINARY_SUBTAG:
 	    case HEAP_BINARY_SUBTAG:
 	    case SUB_BINARY_SUBTAG:
@@ -2786,8 +2761,23 @@ tailrecur_ne:
 		    }
 		    break; /* not equal */
 		}
-	    case HASHMAP_SUBTAG:
-		{
+	    case MAP_SUBTAG:
+                if (is_flatmap_rel(a, a_base)) {
+		    aa = flatmap_val_rel(a, a_base);
+		    if (!is_boxed(b) || *boxed_val_rel(b,b_base) != *aa)
+			goto not_equal;
+		    bb = flatmap_val_rel(b,b_base);
+		    sz = flatmap_get_size((flatmap_t*)aa);
+
+		    if (sz != flatmap_get_size((flatmap_t*)bb)) goto not_equal;
+		    if (sz == 0) goto pop_next;
+
+		    aa += 2;
+		    bb += 2;
+		    sz += 1; /* increment for tuple-keys */
+		    goto term_array;
+
+                } else {
 		    if (!is_boxed(b) || *boxed_val_rel(b,b_base) != hdr)
 			goto not_equal;
 
@@ -3124,44 +3114,56 @@ tailrecur_ne:
 		++aa;
 		++bb;
 		goto term_array;
-	    case (_TAG_HEADER_MAP >> _TAG_PRIMARY_SIZE) :
-		if (!is_flatmap_rel(b,b_base)) {
-		    a_tag = MAP_DEF;
-		    goto mixed_types;
-		}
-		aa = (Eterm *)flatmap_val_rel(a,a_base);
-		bb = (Eterm *)flatmap_val_rel(b,b_base);
-
-		i = flatmap_get_size((flatmap_t*)aa);
-		if (i != flatmap_get_size((flatmap_t*)bb)) {
-		    RETURN_NEQ((int)(i - flatmap_get_size((flatmap_t*)bb)));
-		}
-		if (i == 0) {
-		    goto pop_next;
-		}
-		aa += 2;
-		bb += 2;
-		if (exact) {
-		    i  += 1; /* increment for tuple-keys */
-		    goto term_array;
-		}
-		else {
-		    /* Value array */
-		    WSTACK_PUSH3(stack, (UWord)(bb+1), (UWord)(aa+1), TERM_ARRAY_OP_WORD(i));
-		    /* Switch back from 'exact' key compare */
-		    WSTACK_PUSH(stack, OP_WORD(SWITCH_EXACT_OFF_OP));
-		    /* Now do 'exact' compare of key tuples */
-		    a = *aa;
-		    b = *bb;
-		    exact = 1;
-		    goto bodyrecur;
-		}
-
-	    case (_TAG_HEADER_HASHMAP >> _TAG_PRIMARY_SIZE) :
+            case (_TAG_HEADER_MAP >> _TAG_PRIMARY_SIZE) :
 		{
                     struct erts_cmp_hashmap_state* sp;
+                    if (is_flatmap_header(ahdr)) {
+                        if (!is_flatmap_rel(b,b_base)) {
+                            if (is_hashmap_rel(b,b_base)) {
+                                aa = (Eterm *)flatmap_val_rel(a,a_base);
+                                i = flatmap_get_size((flatmap_t*)aa) - hashmap_size_rel(b,b_base);
+                                ASSERT(i != 0);
+                                RETURN_NEQ(i);
+                            }
+                            a_tag = MAP_DEF;
+                            goto mixed_types;
+                        }
+                        aa = (Eterm *)flatmap_val_rel(a,a_base);
+                        bb = (Eterm *)flatmap_val_rel(b,b_base);
+
+                        i = flatmap_get_size((flatmap_t*)aa);
+                        if (i != flatmap_get_size((flatmap_t*)bb)) {
+                            RETURN_NEQ((int)(i - flatmap_get_size((flatmap_t*)bb)));
+                        }
+                        if (i == 0) {
+                            goto pop_next;
+                        }
+                        aa += 2;
+                        bb += 2;
+                        if (exact) {
+                            i  += 1; /* increment for tuple-keys */
+                            goto term_array;
+                        }
+                        else {
+                            /* Value array */
+                            WSTACK_PUSH3(stack,(UWord)(bb+1),(UWord)(aa+1),TERM_ARRAY_OP_WORD(i));
+                            /* Switch back from 'exact' key compare */
+                            WSTACK_PUSH(stack,OP_WORD(SWITCH_EXACT_OFF_OP));
+                            /* Now do 'exact' compare of key tuples */
+                            a = *aa;
+                            b = *bb;
+                            exact = 1;
+                            goto bodyrecur;
+                        }
+                    }
 		    if (!is_hashmap_rel(b,b_base)) {
-			a_tag = HASHMAP_DEF;
+                        if (is_flatmap_rel(b,b_base)) {
+                            bb = (Eterm *)flatmap_val_rel(b,b_base);
+                            i = hashmap_size_rel(a,a_base) - flatmap_get_size((flatmap_t*)bb);
+                            ASSERT(i != 0);
+                            RETURN_NEQ(i);
+                        }
+			a_tag = MAP_DEF;
 			goto mixed_types;
 		    }
 		    i = hashmap_size_rel(a,a_base) - hashmap_size_rel(b,b_base);