Merge branch 'master' into sverk/master/halt-INT_MIN

1 files changed, 1304 insertions, 95 deletions

diff --git a/erts/emulator/beam/copy.c b/erts/emulator/beam/copy.c
index 64be43edb4..b38ebe066b 100644
--- a/erts/emulator/beam/copy.c
+++ b/erts/emulator/beam/copy.c
@@ -35,56 +35,59 @@
 #include "erl_bits.h"
 #include "dtrace-wrapper.h"
 
-static void move_one_frag(Eterm** hpp, ErlHeapFragment*, ErlOffHeap*);
+static void move_one_frag(Eterm** hpp, ErlHeapFragment*, ErlOffHeap*, int);
 
 /*
  *  Copy object "obj" to process p.
  */
-Eterm
-copy_object(Eterm obj, Process* to)
-{
-    Uint size = size_object(obj);
-    Eterm* hp = HAlloc(to, size);
-    Eterm res;
+Eterm copy_object_x(Eterm obj, Process* to, Uint extra) {
+    if (!is_immed(obj)) {
+        Uint size = size_object(obj);
+        Eterm* hp = HAllocX(to, size, extra);
+        Eterm res;
 
 #ifdef USE_VM_PROBES
-    if (DTRACE_ENABLED(copy_object)) {
-        DTRACE_CHARBUF(proc_name, 64);
+        if (DTRACE_ENABLED(copy_object)) {
+            DTRACE_CHARBUF(proc_name, 64);
 
-        erts_snprintf(proc_name, sizeof(DTRACE_CHARBUF_NAME(proc_name)),
-                      "%T", to->common.id);
-        DTRACE2(copy_object, proc_name, size);
-    }
+            erts_snprintf(proc_name, sizeof(DTRACE_CHARBUF_NAME(proc_name)),
+                    "%T", to->common.id);
+            DTRACE2(copy_object, proc_name, size);
+        }
 #endif
-    res = copy_struct(obj, size, &hp, &to->off_heap);
+        res = copy_struct(obj, size, &hp, &to->off_heap);
 #ifdef DEBUG
-    if (eq(obj, res) == 0) {
-	erts_exit(ERTS_ABORT_EXIT, "copy not equal to source\n");
-    }
+        if (eq(obj, res) == 0) {
+            erts_exit(ERTS_ABORT_EXIT, "copy not equal to source\n");
+        }
 #endif
-    return res;
+        return res;
+    }
+    return obj;
 }
 
 /*
  * Return the "flat" size of the object.
  */
 
-#if HALFWORD_HEAP
-Uint size_object_rel(Eterm obj, Eterm* base)
-#else
 Uint size_object(Eterm obj)
-#endif
 {
     Uint sum = 0;
     Eterm* ptr;
     int arity;
+#ifdef DEBUG
+    Eterm mypid = erts_get_current_pid();
+#endif
 
     DECLARE_ESTACK(s);
+
+    VERBOSE(DEBUG_SHCOPY, ("[pid=%T] size_object %p\n", mypid, obj));
+
     for (;;) {
 	switch (primary_tag(obj)) {
 	case TAG_PRIMARY_LIST:
 	    sum += 2;
-	    ptr = list_val_rel(obj,base);
+	    ptr = list_val(obj);
 	    obj = *ptr++;
 	    if (!IS_CONST(obj)) {
 		ESTACK_PUSH(s, obj);
@@ -93,11 +96,11 @@ Uint size_object(Eterm obj)
 	    break;
 	case TAG_PRIMARY_BOXED:
 	    {
-		Eterm hdr = *boxed_val_rel(obj,base);
+		Eterm hdr = *boxed_val(obj);
 		ASSERT(is_header(hdr));
 		switch (hdr & _TAG_HEADER_MASK) {
 		case ARITYVAL_SUBTAG:
-		    ptr = tuple_val_rel(obj,base);
+		    ptr = tuple_val(obj);
 		    arity = header_arity(hdr);
 		    sum += arity + 1;
 		    if (arity == 0) { /* Empty tuple -- unusual. */
@@ -113,7 +116,7 @@ Uint size_object(Eterm obj)
 		    break;
 		case FUN_SUBTAG:
 		    {
-			Eterm* bptr = fun_val_rel(obj,base);
+			Eterm* bptr = fun_val(obj);
 			ErlFunThing* funp = (ErlFunThing *) bptr;
 			unsigned eterms = 1 /* creator */ + funp->num_free;
 			unsigned sz = thing_arityval(hdr);
@@ -134,7 +137,7 @@ Uint size_object(Eterm obj)
                             {
                                 Uint n;
                                 flatmap_t *mp;
-                                mp  = (flatmap_t*)flatmap_val_rel(obj,base);
+                                mp  = (flatmap_t*)flatmap_val(obj);
                                 ptr = (Eterm *)mp;
                                 n   = flatmap_get_size(mp) + 1;
                                 sum += n + 2;
@@ -153,7 +156,7 @@ Uint size_object(Eterm obj)
 			    {
 				Eterm *head;
 				Uint sz;
-				head  = hashmap_val_rel(obj, base);
+				head  = hashmap_val(obj);
 				sz    = hashmap_bitcount(MAP_HEADER_VAL(hdr));
 				sum  += 1 + sz + header_arity(hdr);
 				head += 1 + header_arity(hdr);
@@ -182,7 +185,7 @@ Uint size_object(Eterm obj)
 			Uint bitoffs;
 			Uint extra_bytes;
 			Eterm hdr;
-			ERTS_GET_REAL_BIN_REL(obj, real_bin, offset, bitoffs, bitsize, base);
+			ERTS_GET_REAL_BIN(obj, real_bin, offset, bitoffs, bitsize);
 			if ((bitsize + bitoffs) > 8) {
 			    sum += ERL_SUB_BIN_SIZE;
 			    extra_bytes = 2;
@@ -192,11 +195,11 @@ Uint size_object(Eterm obj)
 			} else {
 			    extra_bytes = 0;
 			}
-			hdr = *binary_val_rel(real_bin,base);
+			hdr = *binary_val(real_bin);
 			if (thing_subtag(hdr) == REFC_BINARY_SUBTAG) {
 			    sum += PROC_BIN_SIZE;
 			} else {
-			    sum += heap_bin_size(binary_size_rel(obj,base)+extra_bytes);
+			    sum += heap_bin_size(binary_size(obj)+extra_bytes);
 			}
 			goto pop_next;
 		    }
@@ -214,6 +217,7 @@ Uint size_object(Eterm obj)
 	pop_next:
 	    if (ESTACK_ISEMPTY(s)) {
 		DESTROY_ESTACK(s);
+		VERBOSE(DEBUG_SHCOPY, ("[pid=%T] size was: %u\n", mypid, sum));
 		return sum;
 	    }
 	    obj = ESTACK_POP(s);
@@ -225,14 +229,377 @@ Uint size_object(Eterm obj)
 }
 
 /*
+ *  Machinery for sharing preserving information
+ *  Using a WSTACK but not very transparently; consider refactoring
+ */
+
+#define DECLARE_BITSTORE(s)						\
+    DECLARE_WSTACK(s);							\
+    int WSTK_CONCAT(s,_bitoffs) = 0;					\
+    int WSTK_CONCAT(s,_offset) = 0;					\
+    UWord WSTK_CONCAT(s,_buffer) = 0
+
+#define DESTROY_BITSTORE(s) DESTROY_WSTACK(s)
+#define BITSTORE_PUT(s,i)						\
+do {									\
+    WSTK_CONCAT(s,_buffer) |= i << WSTK_CONCAT(s,_bitoffs);		\
+    WSTK_CONCAT(s,_bitoffs) += 2;					\
+    if (WSTK_CONCAT(s,_bitoffs) >= 8*sizeof(UWord)) {			\
+	WSTACK_PUSH(s, WSTK_CONCAT(s,_buffer));				\
+	WSTK_CONCAT(s,_bitoffs) = 0;					\
+	WSTK_CONCAT(s,_buffer) = 0;					\
+    }									\
+} while(0)
+#define BITSTORE_CLOSE(s)						\
+do {									\
+    if (WSTK_CONCAT(s,_bitoffs) > 0) {					\
+	WSTACK_PUSH(s, WSTK_CONCAT(s,_buffer));				\
+	WSTK_CONCAT(s,_bitoffs) = 0;					\
+    }									\
+} while(0)
+
+#define BITSTORE_FETCH(s,dst)                                           \
+do {                                                                    \
+    UWord result;                                                       \
+    if (WSTK_CONCAT(s,_bitoffs) <= 0) {                                 \
+        WSTK_CONCAT(s,_buffer) = s.wstart[WSTK_CONCAT(s,_offset)];      \
+        WSTK_CONCAT(s,_offset)++;                                       \
+        WSTK_CONCAT(s,_bitoffs) = 8*sizeof(UWord);                      \
+    }                                                                   \
+    WSTK_CONCAT(s,_bitoffs) -= 2;                                       \
+    result = WSTK_CONCAT(s,_buffer) & 3;                                \
+    WSTK_CONCAT(s,_buffer) >>= 2;                                       \
+    (dst) = result;                                                     \
+} while(0)
+
+#define BOXED_VISITED_MASK	 ((Eterm) 3)
+#define BOXED_VISITED		 ((Eterm) 1)
+#define BOXED_SHARED_UNPROCESSED ((Eterm) 2)
+#define BOXED_SHARED_PROCESSED	 ((Eterm) 3)
+
+#define COUNT_OFF_HEAP (0)
+
+#define IN_LITERAL_PURGE_AREA(info, ptr)                 \
+    ((info)->range_ptr && (                              \
+        (info)->range_ptr <= (ptr) &&                    \
+        (ptr) < ((info)->range_ptr + (info)->range_sz)))
+/*
+ *  Return the real size of an object and find sharing information
+ *  This currently returns the same as erts_debug:size/1.
+ *  It is argued whether the size of subterms in constant pools
+ *  should be counted or not.
+ */
+
+Uint size_shared(Eterm obj)
+{
+    Eterm saved_obj = obj;
+    Uint sum = 0;
+    Eterm* ptr;
+
+    DECLARE_EQUEUE(s);
+    DECLARE_BITSTORE(b);
+
+    for (;;) {
+	switch (primary_tag(obj)) {
+	case TAG_PRIMARY_LIST: {
+	    Eterm head, tail;
+	    ptr = list_val(obj);
+	    /* we're not counting anything that's outside our heap */
+	    if (!COUNT_OFF_HEAP && erts_is_literal(obj,ptr)) {
+		goto pop_next;
+	    }
+	    head = CAR(ptr);
+	    tail = CDR(ptr);
+	    /* if it's visited, don't count it */
+	    if (primary_tag(tail) == TAG_PRIMARY_HEADER ||
+		primary_tag(head) == TAG_PRIMARY_HEADER) {
+		goto pop_next;
+	    }
+	    /* else make it visited now */
+	    switch (primary_tag(tail)) {
+	    case TAG_PRIMARY_LIST:
+		ptr[1] = (tail - TAG_PRIMARY_LIST) | TAG_PRIMARY_HEADER;
+		break;
+	    case TAG_PRIMARY_IMMED1:
+		CAR(ptr) = (head - primary_tag(head)) | TAG_PRIMARY_HEADER;
+		CDR(ptr) = (tail - TAG_PRIMARY_IMMED1) | primary_tag(head);
+		break;
+	    case TAG_PRIMARY_BOXED:
+		BITSTORE_PUT(b, primary_tag(head));
+		CAR(ptr) = (head - primary_tag(head)) | TAG_PRIMARY_HEADER;
+		CDR(ptr) = (tail - TAG_PRIMARY_BOXED) | TAG_PRIMARY_HEADER;
+		break;
+	    }
+	    /* and count it */
+	    sum += 2;
+	    if (!IS_CONST(head)) {
+		EQUEUE_PUT(s, head);
+	    }
+	    obj = tail;
+	    break;
+	}
+	case TAG_PRIMARY_BOXED: {
+	    Eterm hdr;
+	    ptr = boxed_val(obj);
+	    /* we're not counting anything that's outside our heap */
+	    if (!COUNT_OFF_HEAP && erts_is_literal(obj,ptr)) {
+		goto pop_next;
+	    }
+	    hdr = *ptr;
+	    /* if it's visited, don't count it */
+	    if (primary_tag(hdr) != TAG_PRIMARY_HEADER) {
+		goto pop_next;
+	    }
+	    /* else make it visited now */
+	    *ptr = (hdr - primary_tag(hdr)) + BOXED_VISITED;
+	    /* and count it */
+	    ASSERT(is_header(hdr));
+	    switch (hdr & _TAG_HEADER_MASK) {
+	    case ARITYVAL_SUBTAG: {
+		int arity = header_arity(hdr);
+		sum += arity + 1;
+		if (arity == 0) { /* Empty tuple -- unusual. */
+		    goto pop_next;
+		}
+		while (arity-- > 0) {
+		    obj = *++ptr;
+		    if (!IS_CONST(obj)) {
+			EQUEUE_PUT(s, obj);
+		    }
+		}
+		goto pop_next;
+	    }
+	    case FUN_SUBTAG: {
+		ErlFunThing* funp = (ErlFunThing *) ptr;
+		unsigned eterms = 1 /* creator */ + funp->num_free;
+		unsigned sz = thing_arityval(hdr);
+		sum += 1 /* header */ + sz + eterms;
+		ptr += 1 /* header */ + sz;
+		while (eterms-- > 0) {
+		    obj = *ptr++;
+		    if (!IS_CONST(obj)) {
+			EQUEUE_PUT(s, obj);
+		    }
+		}
+		goto pop_next;
+	    }
+	    case SUB_BINARY_SUBTAG: {
+		ErlSubBin* sb = (ErlSubBin *) ptr;
+		Uint extra_bytes;
+		Eterm hdr;
+		ASSERT((sb->thing_word & ~BOXED_VISITED_MASK) == HEADER_SUB_BIN);
+		if (sb->bitsize + sb->bitoffs > 8) {
+		    sum += ERL_SUB_BIN_SIZE;
+		    extra_bytes = 2;
+		} else if (sb->bitsize + sb->bitoffs > 0) {
+		    sum += ERL_SUB_BIN_SIZE;
+		    extra_bytes = 1;
+		} else {
+		    extra_bytes = 0;
+		}
+		ptr = binary_val(sb->orig);
+		hdr = (*ptr) & ~BOXED_VISITED_MASK;
+		if (thing_subtag(hdr) == REFC_BINARY_SUBTAG) {
+		    sum += PROC_BIN_SIZE;
+		} else {
+		    ASSERT(thing_subtag(hdr) == HEAP_BINARY_SUBTAG);
+		    sum += heap_bin_size(binary_size(obj) + extra_bytes);
+		}
+		goto pop_next;
+	    }
+            case MAP_SUBTAG:
+                switch (MAP_HEADER_TYPE(hdr)) {
+                    case MAP_HEADER_TAG_FLATMAP_HEAD : {
+                        flatmap_t *mp  = (flatmap_t*)flatmap_val(obj);
+                        Uint n = flatmap_get_size(mp) + 1;
+                        ptr  = (Eterm *)mp;
+                        sum += n + 2;
+                        ptr += 2; /* hdr + size words */
+                        while (n--) {
+                            obj = *ptr++;
+                            if (!IS_CONST(obj)) {
+                                EQUEUE_PUT(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 : {
+                        Uint n = hashmap_bitcount(MAP_HEADER_VAL(hdr));
+                        sum += 1 + n + header_arity(hdr);
+                        ptr += 1 + header_arity(hdr);
+                        while (n--) {
+                            obj = *ptr++;
+                            if (!IS_CONST(obj)) {
+                                EQUEUE_PUT(s, obj);
+                            }
+                        }
+                        goto pop_next;
+                    }
+                    default:
+                        erts_exit(ERTS_ABORT_EXIT, "size_shared: bad hashmap type %d\n", MAP_HEADER_TYPE(hdr));
+                }
+	    case BIN_MATCHSTATE_SUBTAG:
+		erts_exit(ERTS_ABORT_EXIT,
+			 "size_shared: matchstate term not allowed");
+	    default:
+		sum += thing_arityval(hdr) + 1;
+		goto pop_next;
+	    }
+	    break;
+	}
+	case TAG_PRIMARY_IMMED1:
+	pop_next:
+	    if (EQUEUE_ISEMPTY(s)) {
+		goto cleanup;
+	    }
+	    obj = EQUEUE_GET(s);
+	    break;
+	default:
+	    erts_exit(ERTS_ABORT_EXIT, "size_shared: bad tag for %#x\n", obj);
+	}
+    }
+
+cleanup:
+    obj = saved_obj;
+    BITSTORE_CLOSE(b);
+    for (;;) {
+	switch (primary_tag(obj)) {
+	case TAG_PRIMARY_LIST: {
+	    Eterm head, tail;
+	    ptr = list_val(obj);
+	    if (!COUNT_OFF_HEAP && erts_is_literal(obj,ptr)) {
+		goto cleanup_next;
+	    }
+	    head = CAR(ptr);
+	    tail = CDR(ptr);
+	    /* if not already clean, clean it up */
+	    if (primary_tag(tail) == TAG_PRIMARY_HEADER) {
+		if (primary_tag(head) == TAG_PRIMARY_HEADER) {
+		    Eterm saved;
+                    BITSTORE_FETCH(b, saved);
+		    CAR(ptr) = head = (head - TAG_PRIMARY_HEADER) | saved;
+		    CDR(ptr) = tail = (tail - TAG_PRIMARY_HEADER) | TAG_PRIMARY_BOXED;
+		} else {
+		    CDR(ptr) = tail = (tail - TAG_PRIMARY_HEADER) | TAG_PRIMARY_LIST;
+		}
+	    } else if (primary_tag(head) == TAG_PRIMARY_HEADER) {
+		CAR(ptr) = head = (head - TAG_PRIMARY_HEADER) | primary_tag(tail);
+		CDR(ptr) = tail = (tail - primary_tag(tail)) | TAG_PRIMARY_IMMED1;
+	    } else {
+		goto cleanup_next;
+	    }
+	    /* and its children too */
+	    if (!IS_CONST(head)) {
+		EQUEUE_PUT_UNCHECKED(s, head);
+	    }
+	    obj = tail;
+	    break;
+	}
+	case TAG_PRIMARY_BOXED: {
+	    Eterm hdr;
+	    ptr = boxed_val(obj);
+	    if (!COUNT_OFF_HEAP && erts_is_literal(obj,ptr)) {
+		goto cleanup_next;
+	    }
+	    hdr = *ptr;
+	    /* if not already clean, clean it up */
+	    if (primary_tag(hdr) == TAG_PRIMARY_HEADER) {
+		goto cleanup_next;
+	    }
+	    else {
+		ASSERT(primary_tag(hdr) == BOXED_VISITED);
+		*ptr = hdr = (hdr - BOXED_VISITED) + TAG_PRIMARY_HEADER;
+	    }
+	    /* and its children too */
+	    switch (hdr & _TAG_HEADER_MASK) {
+	    case ARITYVAL_SUBTAG: {
+		int arity = header_arity(hdr);
+		if (arity == 0) { /* Empty tuple -- unusual. */
+		    goto cleanup_next;
+		}
+		while (arity-- > 0) {
+		    obj = *++ptr;
+		    if (!IS_CONST(obj)) {
+			EQUEUE_PUT_UNCHECKED(s, obj);
+		    }
+		}
+		goto cleanup_next;
+	    }
+	    case FUN_SUBTAG: {
+		ErlFunThing* funp = (ErlFunThing *) ptr;
+		unsigned eterms = 1 /* creator */ + funp->num_free;
+		unsigned sz = thing_arityval(hdr);
+		ptr += 1 /* header */ + sz;
+		while (eterms-- > 0) {
+		    obj = *ptr++;
+		    if (!IS_CONST(obj)) {
+			EQUEUE_PUT_UNCHECKED(s, obj);
+		    }
+		}
+		goto cleanup_next;
+	    }
+            case MAP_SUBTAG:
+                switch (MAP_HEADER_TYPE(hdr)) {
+                    case MAP_HEADER_TAG_FLATMAP_HEAD : {
+                        flatmap_t *mp = (flatmap_t *) ptr;
+                        Uint n = flatmap_get_size(mp) + 1;
+                        ptr += 2; /* hdr + size words */
+                        while (n--) {
+                            obj = *ptr++;
+                            if (!IS_CONST(obj)) {
+                                EQUEUE_PUT_UNCHECKED(s, obj);
+                            }
+                        }
+                        goto cleanup_next;
+                    }
+                    case MAP_HEADER_TAG_HAMT_HEAD_BITMAP :
+                    case MAP_HEADER_TAG_HAMT_HEAD_ARRAY :
+                    case MAP_HEADER_TAG_HAMT_NODE_BITMAP : {
+                        Uint n = hashmap_bitcount(MAP_HEADER_VAL(hdr));
+                        sum += 1 + n + header_arity(hdr);
+                        ptr += 1 + header_arity(hdr);
+                        while (n--) {
+                            obj = *ptr++;
+                            if (!IS_CONST(obj)) {
+                                EQUEUE_PUT_UNCHECKED(s, obj);
+                            }
+                        }
+                        goto cleanup_next;
+                    }
+                    default:
+                        erts_exit(ERTS_ABORT_EXIT, "size_shared: bad hashmap type %d\n", MAP_HEADER_TYPE(hdr));
+                }
+	    default:
+		goto cleanup_next;
+	    }
+	    break;
+	}
+	case TAG_PRIMARY_IMMED1:
+	cleanup_next:
+	    if (EQUEUE_ISEMPTY(s)) {
+		goto all_clean;
+	    }
+	    obj = EQUEUE_GET(s);
+	    break;
+	default:
+	    erts_exit(ERTS_ABORT_EXIT, "size_shared: bad tag for %#x\n", obj);
+	}
+    }
+
+ all_clean:
+    /* Return the result */
+    DESTROY_EQUEUE(s);
+    DESTROY_BITSTORE(b);
+    return sum;
+}
+
+
+/*
  *  Copy a structure to a heap.
  */
-#if HALFWORD_HEAP
-Eterm copy_struct_rel(Eterm obj, Uint sz, Eterm** hpp, ErlOffHeap* off_heap,
-                      Eterm* src_base, Eterm* dst_base)
-#else
-Eterm copy_struct(Eterm obj, Uint sz, Eterm** hpp, ErlOffHeap* off_heap)
-#endif
+Eterm copy_struct_x(Eterm obj, Uint sz, Eterm** hpp, ErlOffHeap* off_heap, Uint *bsz)
 {
     char* hstart;
     Uint hsize;
@@ -247,19 +614,23 @@ Eterm copy_struct(Eterm obj, Uint sz, Eterm** hpp, ErlOffHeap* off_heap)
     Eterm* argp;
     Eterm* const_tuple;
     Eterm hdr;
+    Eterm *hend;
     int i;
 #ifdef DEBUG
     Eterm org_obj = obj;
     Uint org_sz = sz;
+    Eterm mypid = erts_get_current_pid();
 #endif
 
     if (IS_CONST(obj))
 	return obj;
 
+    VERBOSE(DEBUG_SHCOPY, ("[pid=%T] copy_struct %p\n", mypid, obj));
+
     DTRACE1(copy_struct, (int32_t)sz);
 
     hp = htop = *hpp;
-    hbot   = htop + sz;
+    hbot = hend = htop + sz;
     hstart = (char *)htop;
     hsize = (char*) hbot - hstart;
     const_tuple = 0;
@@ -268,7 +639,7 @@ Eterm copy_struct(Eterm obj, Uint sz, Eterm** hpp, ErlOffHeap* off_heap)
     switch (primary_tag(obj)) {
     case TAG_PRIMARY_LIST:
 	argp = &res;
-	objp = list_val_rel(obj,src_base);
+	objp = list_val(obj);
 	goto L_copy_list;
     case TAG_PRIMARY_BOXED: argp = &res; goto L_copy_boxed;
     default:
@@ -286,14 +657,11 @@ Eterm copy_struct(Eterm obj, Uint sz, Eterm** hpp, ErlOffHeap* off_heap)
 	    hp++;
 	    break;
 	case TAG_PRIMARY_LIST:
-	    objp = list_val_rel(obj,src_base);
-	#if !HALFWORD_HEAP || defined(DEBUG)
-	    if (in_area(objp,hstart,hsize)) {
-		ASSERT(!HALFWORD_HEAP);
+	    objp = list_val(obj);
+	    if (ErtsInArea(objp,hstart,hsize)) {
 		hp++;
 		break;
 	    }
-	#endif
 	    argp = hp++;
 	    /* Fall through */
 
@@ -309,23 +677,15 @@ Eterm copy_struct(Eterm obj, Uint sz, Eterm** hpp, ErlOffHeap* off_heap)
 		}
 		else {
 		    CAR(htop) = elem;
-		#if HALFWORD_HEAP
-		    CDR(htop) = CDR(objp);
-		    *tailp = make_list_rel(htop,dst_base);
-		    htop += 2;
-		    goto L_copy;
-		#else
 		    tailp = &CDR(htop);
 		    htop += 2;
-		#endif
 		}
-		ASSERT(!HALFWORD_HEAP || tp < hp || tp >= hbot);
-		*tp = make_list_rel(tailp - 1, dst_base);
+		*tp = make_list(tailp - 1);
 		obj = CDR(objp);
 		if (!is_list(obj)) {
 		    break;
 		}
-		objp = list_val_rel(obj,src_base);
+		objp = list_val(obj);
 	    }
 	    switch (primary_tag(obj)) {
 	    case TAG_PRIMARY_IMMED1: *tailp = obj; goto L_copy;
@@ -337,24 +697,21 @@ Eterm copy_struct(Eterm obj, Uint sz, Eterm** hpp, ErlOffHeap* off_heap)
 	    }
 	    
 	case TAG_PRIMARY_BOXED:
-	#if !HALFWORD_HEAP || defined(DEBUG)
-	    if (in_area(boxed_val_rel(obj,src_base),hstart,hsize)) {
-		ASSERT(!HALFWORD_HEAP);
+	    if (ErtsInArea(boxed_val(obj),hstart,hsize)) {
 		hp++;
 		break;
 	    }
-	#endif
 	    argp = hp++;
 
 	L_copy_boxed:
-	    objp = boxed_val_rel(obj, src_base);
+	    objp = boxed_val(obj);
 	    hdr = *objp;
 	    switch (hdr & _TAG_HEADER_MASK) {
 	    case ARITYVAL_SUBTAG:
 		{
 		    int const_flag = 1; /* assume constant tuple */
 		    i = arityval(hdr);
-		    *argp = make_tuple_rel(htop, dst_base);
+		    *argp = make_tuple(htop);
 		    tp = htop;	/* tp is pointer to new arity value */
 		    *htop++ = *objp++; /* copy arity value */
 		    while (i--) {
@@ -383,7 +740,7 @@ Eterm copy_struct(Eterm obj, Uint sz, Eterm** hpp, ErlOffHeap* off_heap)
 		    while (i--)  {
 			*tp++ = *objp++;
 		    }
-		    *argp = make_binary_rel(hbot, dst_base);
+		    *argp = make_binary(hbot);
 		    pb = (ProcBin*) hbot;
 		    erts_refc_inc(&pb->val->refc, 2);
 		    pb->next = off_heap->first;
@@ -410,7 +767,7 @@ Eterm copy_struct(Eterm obj, Uint sz, Eterm** hpp, ErlOffHeap* off_heap)
 			extra_bytes = 0;
 		    } 
 		    real_size = size+extra_bytes;
-		    objp = binary_val_rel(real_bin,src_base);
+		    objp = binary_val(real_bin);
 		    if (thing_subtag(*objp) == HEAP_BINARY_SUBTAG) {
 			ErlHeapBin* from = (ErlHeapBin *) objp;
 			ErlHeapBin* to;
@@ -440,7 +797,7 @@ Eterm copy_struct(Eterm obj, Uint sz, Eterm** hpp, ErlOffHeap* off_heap)
 			off_heap->first = (struct erl_off_heap_header*) to;
 			OH_OVERHEAD(off_heap, to->size / sizeof(Eterm));
 		    }
-		    *argp = make_binary_rel(hbot, dst_base);
+		    *argp = make_binary(hbot);
 		    if (extra_bytes != 0) {
 			ErlSubBin* res;
 			hbot -= ERL_SUB_BIN_SIZE;
@@ -452,7 +809,7 @@ Eterm copy_struct(Eterm obj, Uint sz, Eterm** hpp, ErlOffHeap* off_heap)
 			res->offs = 0;
 			res->is_writable = 0;
 			res->orig = *argp;
-			*argp = make_binary_rel(hbot, dst_base);
+			*argp = make_binary(hbot);
 		    }
 		    break;
 		}
@@ -470,7 +827,7 @@ Eterm copy_struct(Eterm obj, Uint sz, Eterm** hpp, ErlOffHeap* off_heap)
 		    funp->next = off_heap->first;
 		    off_heap->first = (struct erl_off_heap_header*) funp;
 		    erts_refc_inc(&funp->fe->refc, 2);
-		    *argp = make_fun_rel(tp, dst_base);
+		    *argp = make_fun(tp);
 		}
 		break;
 	    case EXTERNAL_PID_SUBTAG:
@@ -490,7 +847,7 @@ Eterm copy_struct(Eterm obj, Uint sz, Eterm** hpp, ErlOffHeap* off_heap)
 		  off_heap->first = (struct erl_off_heap_header*)etp;
 		  erts_refc_inc(&etp->node->refc, 2);
 
-		  *argp = make_external_rel(tp, dst_base);
+		  *argp = make_external(tp);
 		}
 		break;
 	    case MAP_SUBTAG:
@@ -498,7 +855,7 @@ Eterm copy_struct(Eterm obj, Uint sz, Eterm** hpp, ErlOffHeap* off_heap)
 		switch (MAP_HEADER_TYPE(hdr)) {
 		    case MAP_HEADER_TAG_FLATMAP_HEAD :
                         i = flatmap_get_size(objp) + 3;
-                        *argp = make_flatmap_rel(htop, dst_base);
+                        *argp = make_flatmap(htop);
                         while (i--) {
                             *htop++ = *objp++;
                         }
@@ -509,7 +866,7 @@ Eterm copy_struct(Eterm obj, Uint sz, Eterm** hpp, ErlOffHeap* off_heap)
 		    case MAP_HEADER_TAG_HAMT_NODE_BITMAP :
 			i = 1 + hashmap_bitcount(MAP_HEADER_VAL(hdr));
 			while (i--)  { *htop++ = *objp++; }
-			*argp = make_hashmap_rel(tp, dst_base);
+			*argp = make_hashmap(tp);
 			break;
 		    default:
 			erts_exit(ERTS_ABORT_EXIT, "copy_struct: bad hashmap type %d\n", MAP_HEADER_TYPE(hdr));
@@ -522,7 +879,7 @@ Eterm copy_struct(Eterm obj, Uint sz, Eterm** hpp, ErlOffHeap* off_heap)
 		i = thing_arityval(hdr)+1;
 		hbot -= i;
 		tp = hbot;
-		*argp = make_boxed_rel(hbot, dst_base);
+		*argp = make_boxed(hbot);
 		while (i--) {
 		    *tp++ = *objp++;
 		}
@@ -538,22 +895,870 @@ Eterm copy_struct(Eterm obj, Uint sz, Eterm** hpp, ErlOffHeap* off_heap)
 	}
     }
 
+    if (bsz) {
+        *hpp = htop;
+        *bsz = hend - hbot;
+    } else {
 #ifdef DEBUG
-    if (htop != hbot)
-	erts_exit(ERTS_ABORT_EXIT,
-		 "Internal error in copy_struct() when copying %T:"
-		 " htop=%p != hbot=%p (sz=%beu)\n",
-		 org_obj, htop, hbot, org_sz); 
+        if (htop != hbot)
+            erts_exit(ERTS_ABORT_EXIT,
+                    "Internal error in copy_struct() when copying %T:"
+                    " htop=%p != hbot=%p (sz=%beu)\n",
+                    org_obj, htop, hbot, org_sz);
 #else
-    if (htop > hbot) {
-	erts_exit(ERTS_ABORT_EXIT,
-		 "Internal error in copy_struct(): htop, hbot overrun\n");
-    }
+        if (htop > hbot) {
+            erts_exit(ERTS_ABORT_EXIT,
+                    "Internal error in copy_struct(): htop, hbot overrun\n");
+        }
 #endif
-    *hpp = (Eterm *) (hstart+hsize);
+        *hpp = (Eterm *) (hstart+hsize);
+    }
+    VERBOSE(DEBUG_SHCOPY, ("[pid=%T] result is at %p\n", mypid, res));
     return res;
 }
 
+
+/*
+ *  Machinery for the table used by the sharing preserving copier
+ *  Using an ESTACK but not very transparently; consider refactoring
+ */
+
+#define DECLARE_SHTABLE(s)					\
+    DECLARE_ESTACK(s);						\
+    Uint ESTK_CONCAT(s,_offset) = 0
+#define DESTROY_SHTABLE(s) DESTROY_ESTACK(s)
+#define SHTABLE_INCR 4
+#define SHTABLE_NEXT(s)	ESTK_CONCAT(s,_offset)
+#define SHTABLE_PUSH(s,x,y,b)					\
+do {								\
+    if (s.sp > s.end - SHTABLE_INCR) {				\
+        erl_grow_estack(&(s), SHTABLE_INCR);	       		\
+    }								\
+    *s.sp++ = (x);						\
+    *s.sp++ = (y);						\
+    *s.sp++ = (Eterm) NULL;					\
+    *s.sp++ = (Eterm) (b);		                	\
+    ESTK_CONCAT(s,_offset) += SHTABLE_INCR;			\
+} while(0)
+#define SHTABLE_X(s,e) (s.start[e])
+#define SHTABLE_Y(s,e) (s.start[(e)+1])
+#define SHTABLE_FWD(s,e) ((Eterm *) (s.start[(e)+2]))
+#define SHTABLE_FWD_UPD(s,e,p) (s.start[(e)+2] = (Eterm) (p))
+#define SHTABLE_REV(s,e) ((Eterm *) (s.start[(e)+3]))
+
+#define LIST_SHARED_UNPROCESSED ((Eterm) 0)
+#define LIST_SHARED_PROCESSED	((Eterm) 1)
+
+#define HEAP_ELEM_TO_BE_FILLED	_unchecked_make_list(NULL)
+
+
+/*
+ *  Specialized macros for using/reusing the persistent state
+ */
+
+#define DECLARE_EQUEUE_INIT_INFO(q, info)		\
+    UWord* EQUE_DEF_QUEUE(q) = info->queue_default;	\
+    ErtsEQueue q = {					\
+        EQUE_DEF_QUEUE(q), /* start */			\
+        EQUE_DEF_QUEUE(q), /* front */			\
+        EQUE_DEF_QUEUE(q), /* back */			\
+        1,                 /* possibly_empty */		\
+        EQUE_DEF_QUEUE(q) + DEF_EQUEUE_SIZE, /* end */	\
+        ERTS_ALC_T_ESTACK  /* alloc_type */		\
+    }
+
+#define DECLARE_EQUEUE_FROM_INFO(q, info)		\
+    /* no EQUE_DEF_QUEUE(q), read-only */		\
+    ErtsEQueue q = {					\
+        info->queue_start,      /* start */		\
+        info->queue_start,      /* front */		\
+        info->queue_start,      /* back */		\
+        1,                      /* possibly_empty */	\
+        info->queue_end,        /* end */		\
+        info->queue_alloc_type  /* alloc_type */	\
+    }
+
+#define DECLARE_BITSTORE_INIT_INFO(s, info)		\
+    UWord* WSTK_DEF_STACK(s) = info->bitstore_default;	\
+    ErtsWStack s = {					\
+        WSTK_DEF_STACK(s),  /* wstart */		\
+        WSTK_DEF_STACK(s),  /* wsp */			\
+        WSTK_DEF_STACK(s) + DEF_WSTACK_SIZE, /* wend */	\
+        WSTK_DEF_STACK(s),  /* wdflt */ 		\
+        ERTS_ALC_T_ESTACK /* alloc_type */		\
+    };							\
+    int WSTK_CONCAT(s,_bitoffs) = 0;			\
+    /* no WSTK_CONCAT(s,_offset), write-only */		\
+    UWord WSTK_CONCAT(s,_buffer) = 0
+
+#define DECLARE_BITSTORE_FROM_INFO(s, info)		\
+    /* no WSTK_DEF_STACK(s), read-only */		\
+    ErtsWStack s = {					\
+        info->bitstore_start,  /* wstart */		\
+        NULL,                  /* wsp,  read-only */	\
+        NULL,                  /* wend, read-only */	\
+        NULL,                  /* wdef, read-only */	\
+        info->bitstore_alloc_type /* alloc_type */	\
+    };							\
+    int WSTK_CONCAT(s,_bitoffs) = 0;			\
+    int WSTK_CONCAT(s,_offset) = 0;			\
+    UWord WSTK_CONCAT(s,_buffer) = 0
+
+#define DECLARE_SHTABLE_INIT_INFO(s, info)		\
+    Eterm* ESTK_DEF_STACK(s) = info->shtable_default;	\
+    ErtsEStack s = {					\
+        ESTK_DEF_STACK(s),  /* start */			\
+        ESTK_DEF_STACK(s),  /* sp */			\
+        ESTK_DEF_STACK(s) + DEF_ESTACK_SIZE, /* end */	\
+        ESTK_DEF_STACK(s),  /* default */		\
+        ERTS_ALC_T_ESTACK /* alloc_type */		\
+    };							\
+    Uint ESTK_CONCAT(s,_offset) = 0
+
+#define DECLARE_SHTABLE_FROM_INFO(s, info)		\
+    /* no ESTK_DEF_STACK(s), read-only */		\
+    ErtsEStack s = {					\
+        info->shtable_start,     /* start */		\
+        NULL,                    /* sp,  read-only */	\
+        NULL,                    /* end, read-only */	\
+        NULL,                    /* def, read-only */	\
+        info->shtable_alloc_type /* alloc_type */	\
+    };							\
+    /* no ESTK_CONCAT(s,_offset), read-only */
+
+/*
+ *  Copy object "obj" preserving sharing.
+ *  First half: count size and calculate sharing.
+ */
+Uint copy_shared_calculate(Eterm obj, erts_shcopy_t *info)
+{
+    Uint sum;
+    Uint e;
+    unsigned sz;
+    Eterm* ptr;
+#ifdef DEBUG
+    Eterm mypid = erts_get_current_pid();
+#endif
+
+    DECLARE_EQUEUE_INIT_INFO(s, info);
+    DECLARE_BITSTORE_INIT_INFO(b, info);
+    DECLARE_SHTABLE_INIT_INFO(t, info);
+
+    /* step #0:
+       -------------------------------------------------------
+       get rid of the easy cases first:
+       - copying constants
+       - if not a proper process, do flat copy
+    */
+
+    if (IS_CONST(obj))
+	return 0;
+
+    VERBOSE(DEBUG_SHCOPY, ("[pid=%T] copy_shared_calculate %p\n", mypid, obj));
+    VERBOSE(DEBUG_SHCOPY, ("[pid=%T] message is %T\n", mypid, obj));
+
+    /* step #1:
+       -------------------------------------------------------
+       traverse the term and calculate the size;
+       when traversing, transform as you do in size_shared
+       but when you find shared objects:
+
+       a. add entry in the table, indexed by i
+       b. mark them:
+	  b1. boxed terms, set header to (i | 11)
+	      store (old header, NONV, NULL, backptr) in the entry
+	  b2. cons cells, set CDR to NONV, set CAR to i
+	      store (old CAR, old CDR, NULL, backptr) in the entry
+    */
+
+    sum = 0;
+
+    for (;;) {
+	switch (primary_tag(obj)) {
+	case TAG_PRIMARY_LIST: {
+	    Eterm head, tail;
+	    ptr = list_val(obj);
+	    /* off heap list pointers are copied verbatim */
+	    if (erts_is_literal(obj,ptr)) {
+		VERBOSE(DEBUG_SHCOPY, ("[pid=%T] bypassed copying %p is %T\n", mypid, ptr, obj));
+                if (IN_LITERAL_PURGE_AREA(info,ptr))
+                    info->literal_size += size_object(obj);
+		goto pop_next;
+	    }
+	    head = CAR(ptr);
+	    tail = CDR(ptr);
+	    /* if it's visited, don't count it;
+	       if not already shared, make it shared and store it in the table */
+	    if (primary_tag(tail) == TAG_PRIMARY_HEADER ||
+		primary_tag(head) == TAG_PRIMARY_HEADER) {
+		if (tail != THE_NON_VALUE) {
+		    e = SHTABLE_NEXT(t);
+		    VERBOSE(DEBUG_SHCOPY, ("[pid=%T] tabling L %p\n", mypid, ptr));
+		    SHTABLE_PUSH(t, head, tail, ptr);
+		    CAR(ptr) = (e << _TAG_PRIMARY_SIZE) | LIST_SHARED_UNPROCESSED;
+		    CDR(ptr) = THE_NON_VALUE;
+		}
+		goto pop_next;
+	    }
+	    /* else make it visited now */
+	    switch (primary_tag(tail)) {
+	    case TAG_PRIMARY_LIST:
+		VERBOSE(DEBUG_SHCOPY, ("[pid=%T] mangling L/L %p\n", mypid, ptr));
+		CDR(ptr) = (tail - TAG_PRIMARY_LIST) | TAG_PRIMARY_HEADER;
+		break;
+	    case TAG_PRIMARY_IMMED1:
+		VERBOSE(DEBUG_SHCOPY, ("[pid=%T] mangling L/I %p\n", mypid, ptr));
+		CAR(ptr) = (head - primary_tag(head)) | TAG_PRIMARY_HEADER;
+		CDR(ptr) = (tail - TAG_PRIMARY_IMMED1) | primary_tag(head);
+		break;
+	    case TAG_PRIMARY_BOXED:
+		BITSTORE_PUT(b, primary_tag(head));
+		VERBOSE(DEBUG_SHCOPY, ("[pid=%T] mangling L/B %p\n", mypid, ptr));
+		CAR(ptr) = (head - primary_tag(head)) | TAG_PRIMARY_HEADER;
+		CDR(ptr) = (tail - TAG_PRIMARY_BOXED) | TAG_PRIMARY_HEADER;
+		break;
+	    }
+	    /* and count it */
+	    sum += 2;
+	    if (!IS_CONST(head)) {
+		EQUEUE_PUT(s, head);
+	    }
+	    obj = tail;
+	    break;
+	}
+	case TAG_PRIMARY_BOXED: {
+	    Eterm hdr;
+	    ptr = boxed_val(obj);
+	    /* off heap pointers to boxes are copied verbatim */
+	    if (erts_is_literal(obj,ptr)) {
+		VERBOSE(DEBUG_SHCOPY, ("[pid=%T] bypassed copying %p is %T\n", mypid, ptr, obj));
+                if (IN_LITERAL_PURGE_AREA(info,ptr))
+                    info->literal_size += size_object(obj);
+		goto pop_next;
+	    }
+	    hdr = *ptr;
+	    /* if it's visited, don't count it;
+	       if not already shared, make it shared and store it in the table */
+	    if (primary_tag(hdr) != TAG_PRIMARY_HEADER) {
+		if (primary_tag(hdr) == BOXED_VISITED) {
+		    e = SHTABLE_NEXT(t);
+		    VERBOSE(DEBUG_SHCOPY, ("[pid=%T] tabling B %p\n", mypid, ptr));
+		    SHTABLE_PUSH(t, hdr, THE_NON_VALUE, ptr);
+		    *ptr = (e << _TAG_PRIMARY_SIZE) | BOXED_SHARED_UNPROCESSED;
+		}
+		goto pop_next;
+	    }
+	    /* else make it visited now */
+	    VERBOSE(DEBUG_SHCOPY, ("[pid=%T] mangling B %p\n", mypid, ptr));
+	    *ptr = (hdr - primary_tag(hdr)) + BOXED_VISITED;
+	    /* and count it */
+	    ASSERT(is_header(hdr));
+	    switch (hdr & _TAG_HEADER_MASK) {
+	    case ARITYVAL_SUBTAG: {
+		int arity = header_arity(hdr);
+		sum += arity + 1;
+		if (arity == 0) { /* Empty tuple -- unusual. */
+		    goto pop_next;
+		}
+		while (arity-- > 0) {
+		    obj = *++ptr;
+		    if (!IS_CONST(obj)) {
+			EQUEUE_PUT(s, obj);
+		    }
+		}
+		goto pop_next;
+	    }
+	    case FUN_SUBTAG: {
+		ErlFunThing* funp = (ErlFunThing *) ptr;
+		unsigned eterms = 1 /* creator */ + funp->num_free;
+		sz = thing_arityval(hdr);
+		sum += 1 /* header */ + sz + eterms;
+		ptr += 1 /* header */ + sz;
+		while (eterms-- > 0) {
+		    obj = *ptr++;
+		    if (!IS_CONST(obj)) {
+			EQUEUE_PUT(s, obj);
+		    }
+		}
+		goto pop_next;
+	    }
+	    case SUB_BINARY_SUBTAG: {
+		ErlSubBin* sb = (ErlSubBin *) ptr;
+		Eterm real_bin = sb->orig;
+		Uint bit_offset = sb->bitoffs;
+		Uint bit_size = sb->bitsize;
+		size_t size = sb->size;
+		Uint extra_bytes;
+		Eterm hdr;
+		if (bit_size + bit_offset > 8) {
+		    sum += ERL_SUB_BIN_SIZE;
+		    extra_bytes = 2;
+		} else if (bit_size + bit_offset > 0) {
+		    sum += ERL_SUB_BIN_SIZE;
+		    extra_bytes = 1;
+		} else {
+		    extra_bytes = 0;
+		}
+		ASSERT(is_boxed(real_bin) &&
+		       (((*boxed_val(real_bin)) &
+			 (_TAG_HEADER_MASK - _BINARY_XXX_MASK - BOXED_VISITED_MASK))
+			== _TAG_HEADER_REFC_BIN));
+		hdr = *_unchecked_binary_val(real_bin) & ~BOXED_VISITED_MASK;
+		if (thing_subtag(hdr) == HEAP_BINARY_SUBTAG) {
+		    sum += heap_bin_size(size+extra_bytes);
+		} else {
+		    ASSERT(thing_subtag(hdr) == REFC_BINARY_SUBTAG);
+		    sum += PROC_BIN_SIZE;
+		}
+		goto pop_next;
+	    }
+            case MAP_SUBTAG:
+                switch (MAP_HEADER_TYPE(hdr)) {
+                    case MAP_HEADER_TAG_FLATMAP_HEAD : {
+                        flatmap_t *mp = (flatmap_t *) ptr;
+                        Uint n = flatmap_get_size(mp) + 1;
+                        sum += n + 2;
+                        ptr += 2; /* hdr + size words */
+                        while (n--) {
+                            obj = *ptr++;
+                            if (!IS_CONST(obj)) {
+                                EQUEUE_PUT(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 : {
+                        Uint n = hashmap_bitcount(MAP_HEADER_VAL(hdr));
+                        sum += 1 + n + header_arity(hdr);
+                        ptr += 1 + header_arity(hdr);
+
+                        if (n == 0) {
+                            goto pop_next;
+                        }
+                        while(n--) {
+                            obj = *ptr++;
+                            if (!IS_CONST(obj)) {
+                                EQUEUE_PUT(s, obj);
+                            }
+                        }
+                        goto pop_next;
+                    }
+                    default:
+                        erts_exit(ERTS_ABORT_EXIT, "copy_shared_calculate: bad hashmap type %d\n", MAP_HEADER_TYPE(hdr));
+                }
+            case BIN_MATCHSTATE_SUBTAG:
+		erts_exit(ERTS_ABORT_EXIT,
+			 "size_shared: matchstate term not allowed");
+	    default:
+		sum += thing_arityval(hdr) + 1;
+		goto pop_next;
+	    }
+	    break;
+	}
+	case TAG_PRIMARY_IMMED1:
+	pop_next:
+	    if (EQUEUE_ISEMPTY(s)) {
+                /* add sentinel to the table */
+                SHTABLE_PUSH(t, THE_NON_VALUE, THE_NON_VALUE, NULL);
+                /* store persistent info */
+                BITSTORE_CLOSE(b);
+                info->queue_start = s.start;
+                info->queue_end = s.end;
+                info->queue_alloc_type = s.alloc_type;
+                info->bitstore_start = b.wstart;
+                info->bitstore_alloc_type = b.alloc_type;
+                info->shtable_start = t.start;
+                info->shtable_alloc_type = t.alloc_type;
+                /* single point of return: the size of the object */
+                VERBOSE(DEBUG_SHCOPY, ("[pid=%T] size was: %u\n", mypid, sum));
+                return sum + info->literal_size;
+	    }
+	    obj = EQUEUE_GET(s);
+	    break;
+	default:
+	    erts_exit(ERTS_ABORT_EXIT, "[pid=%T] size_shared: bad tag for %#x\n", obj);
+	}
+    }
+}
+
+/*
+ *  Copy object "obj" preserving sharing.
+ *  Second half: copy and restore the object.
+ */
+Uint copy_shared_perform(Eterm obj, Uint size, erts_shcopy_t *info,
+                         Eterm** hpp, ErlOffHeap* off_heap) {
+    Uint e;
+    unsigned sz;
+    Eterm* ptr;
+    Eterm* hp;
+    Eterm* hscan;
+    Eterm result;
+    Eterm* resp;
+    Eterm *hbot, *hend;
+    unsigned remaining;
+#ifdef DEBUG
+    Eterm mypid = erts_get_current_pid();
+    Eterm saved_obj = obj;
+#endif
+
+    DECLARE_EQUEUE_FROM_INFO(s, info);
+    DECLARE_BITSTORE_FROM_INFO(b, info);
+    DECLARE_SHTABLE_FROM_INFO(t, info);
+
+    /* step #0:
+       -------------------------------------------------------
+       get rid of the easy cases first:
+       - copying constants
+       - if not a proper process, do flat copy
+    */
+
+    if (IS_CONST(obj))
+	return obj;
+
+    VERBOSE(DEBUG_SHCOPY, ("[pid=%T] copy_shared_perform %p\n", mypid, obj));
+
+    /* step #2: was performed before this function was called
+       -------------------------------------------------------
+       allocate new space
+    */
+
+    hscan = hp = *hpp;
+    hbot  = hend = hp + size;
+
+    /* step #3:
+       -------------------------------------------------------
+       traverse the term a second time and when traversing:
+       a. if the object is marked as shared
+	  a1. if the entry contains a forwarding ptr, use that
+	  a2. otherwise, copy it to the new space and store the
+	      forwarding ptr to the entry
+      b. otherwise, reverse-transform as you do in size_shared
+	 and copy to the new space
+    */
+
+    resp = &result;
+    remaining = 0;
+    for (;;) {
+	switch (primary_tag(obj)) {
+	case TAG_PRIMARY_LIST: {
+	    Eterm head, tail;
+	    ptr = list_val(obj);
+	    /* off heap list pointers are copied verbatim */
+	    if (erts_is_literal(obj,ptr)) {
+                if (!IN_LITERAL_PURGE_AREA(info,ptr)) {
+                    *resp = obj;
+                } else {
+                    Uint bsz = 0;
+                    *resp = copy_struct_x(obj, hbot - hp, &hp, off_heap, &bsz);
+                    hbot -= bsz;
+                }
+		goto cleanup_next;
+	    }
+	    head = CAR(ptr);
+	    tail = CDR(ptr);
+	    /* if it is shared */
+	    if (tail == THE_NON_VALUE) {
+		e = head >> _TAG_PRIMARY_SIZE;
+		/* if it has been processed, just use the forwarding pointer */
+		if (primary_tag(head) == LIST_SHARED_PROCESSED) {
+		    *resp = make_list(SHTABLE_FWD(t, e));
+		    goto cleanup_next;
+		}
+		/* else, let's process it now,
+		   copy it and keep the forwarding pointer */
+		else {
+		    CAR(ptr) = (head - primary_tag(head)) + LIST_SHARED_PROCESSED;
+		    head = SHTABLE_X(t, e);
+		    tail = SHTABLE_Y(t, e);
+		    ptr = &(SHTABLE_X(t, e));
+		    VERBOSE(DEBUG_SHCOPY, ("[pid=%T] tabled L %p is %p\n", mypid, ptr, SHTABLE_REV(t, e)));
+		    SHTABLE_FWD_UPD(t, e, hp);
+		}
+	    }
+	    /* if not already clean, clean it up and copy it */
+	    if (primary_tag(tail) == TAG_PRIMARY_HEADER) {
+		if (primary_tag(head) == TAG_PRIMARY_HEADER) {
+		    Eterm saved;
+                    BITSTORE_FETCH(b, saved);
+		    VERBOSE(DEBUG_SHCOPY, ("[pid=%T] unmangling L/B %p\n", mypid, ptr));
+		    CAR(ptr) = head = (head - TAG_PRIMARY_HEADER) + saved;
+		    CDR(ptr) = tail = (tail - TAG_PRIMARY_HEADER) + TAG_PRIMARY_BOXED;
+		} else {
+		    VERBOSE(DEBUG_SHCOPY, ("[pid=%T] unmangling L/L %p\n", mypid, ptr));
+		    CDR(ptr) = tail = (tail - TAG_PRIMARY_HEADER) + TAG_PRIMARY_LIST;
+		}
+	    } else if (primary_tag(head) == TAG_PRIMARY_HEADER) {
+		VERBOSE(DEBUG_SHCOPY, ("[pid=%T] unmangling L/I %p\n", mypid, ptr));
+		CAR(ptr) = head = (head - TAG_PRIMARY_HEADER) | primary_tag(tail);
+		CDR(ptr) = tail = (tail - primary_tag(tail)) | TAG_PRIMARY_IMMED1;
+	    } else {
+		ASSERT(0 && "cannot come here");
+		goto cleanup_next;
+	    }
+	    /* and its children too */
+	    if (IS_CONST(head)) {
+		CAR(hp) = head;
+	    } else {
+		EQUEUE_PUT_UNCHECKED(s, head);
+		CAR(hp) = HEAP_ELEM_TO_BE_FILLED;
+	    }
+	    *resp = make_list(hp);
+	    resp = &(CDR(hp));
+	    hp += 2;
+	    obj = tail;
+	    break;
+	}
+	case TAG_PRIMARY_BOXED: {
+	    Eterm hdr;
+	    ptr = boxed_val(obj);
+	    /* off heap pointers to boxes are copied verbatim */
+	    if (erts_is_literal(obj,ptr)) {
+                if (!IN_LITERAL_PURGE_AREA(info,ptr)) {
+                    *resp = obj;
+                } else {
+                    Uint bsz = 0;
+                    *resp = copy_struct_x(obj, hbot - hp, &hp, off_heap, &bsz);
+                    hbot -= bsz;
+                }
+		goto cleanup_next;
+	    }
+	    hdr = *ptr;
+	    /* clean it up, unless it's already clean or shared and processed */
+	    switch (primary_tag(hdr)) {
+	    case TAG_PRIMARY_HEADER:
+		ASSERT(0 && "cannot come here");
+	    /* if it is shared and has been processed,
+	       just use the forwarding pointer */
+	    case BOXED_SHARED_PROCESSED:
+		e = hdr >> _TAG_PRIMARY_SIZE;
+		*resp = make_boxed(SHTABLE_FWD(t, e));
+		goto cleanup_next;
+	    /* if it is shared but has not been processed yet, let's process
+	       it now: copy it and keep the forwarding pointer */
+	    case BOXED_SHARED_UNPROCESSED:
+		e = hdr >> _TAG_PRIMARY_SIZE;
+		*ptr = (hdr - primary_tag(hdr)) + BOXED_SHARED_PROCESSED;
+		hdr = SHTABLE_X(t, e);
+		ASSERT(primary_tag(hdr) == BOXED_VISITED);
+		VERBOSE(DEBUG_SHCOPY, ("[pid=%T] tabled B %p is %p\n", mypid, ptr, SHTABLE_REV(t, e)));
+		VERBOSE(DEBUG_SHCOPY, ("[pid=%T] unmangling B %p\n", mypid, ptr));
+		SHTABLE_X(t, e) = hdr = (hdr - BOXED_VISITED) + TAG_PRIMARY_HEADER;
+		SHTABLE_FWD_UPD(t, e, hp);
+		break;
+	    case BOXED_VISITED:
+		VERBOSE(DEBUG_SHCOPY, ("[pid=%T] unmangling B %p\n", mypid, ptr));
+		*ptr = hdr = (hdr - BOXED_VISITED) + TAG_PRIMARY_HEADER;
+		break;
+	    }
+	    /* and its children too */
+	    switch (hdr & _TAG_HEADER_MASK) {
+	    case ARITYVAL_SUBTAG: {
+		int arity = header_arity(hdr);
+		*resp = make_boxed(hp);
+		*hp++ = hdr;
+		while (arity-- > 0) {
+		    obj = *++ptr;
+		    if (IS_CONST(obj)) {
+			*hp++ = obj;
+		    } else {
+			EQUEUE_PUT_UNCHECKED(s, obj);
+			*hp++ = HEAP_ELEM_TO_BE_FILLED;
+		    }
+		}
+		goto cleanup_next;
+	    }
+	    case FUN_SUBTAG: {
+		ErlFunThing* funp = (ErlFunThing *) ptr;
+		unsigned eterms = 1 /* creator */ + funp->num_free;
+		sz = thing_arityval(hdr);
+		funp = (ErlFunThing *) hp;
+		*resp = make_fun(hp);
+		*hp++ = hdr;
+		ptr++;
+		while (sz-- > 0) {
+		    *hp++ = *ptr++;
+		}
+		while (eterms-- > 0) {
+		    obj = *ptr++;
+		    if (IS_CONST(obj)) {
+			*hp++ = obj;
+		    } else {
+			EQUEUE_PUT_UNCHECKED(s, obj);
+			*hp++ = HEAP_ELEM_TO_BE_FILLED;
+		    }
+		}
+		funp->next = off_heap->first;
+		off_heap->first = (struct erl_off_heap_header*) funp;
+		erts_refc_inc(&funp->fe->refc, 2);
+		goto cleanup_next;
+	    }
+	    case MAP_SUBTAG:
+                *resp  = make_flatmap(hp);
+                *hp++  = hdr;
+                switch (MAP_HEADER_TYPE(hdr)) {
+                    case MAP_HEADER_TAG_FLATMAP_HEAD : {
+                        flatmap_t *mp = (flatmap_t *) ptr;
+                        Uint n = flatmap_get_size(mp) + 1;
+                        *hp++  = *++ptr; /* keys */
+                        while (n--) {
+                            obj = *++ptr;
+                            if (IS_CONST(obj)) {
+                                *hp++ = obj;
+                            } else {
+                                EQUEUE_PUT_UNCHECKED(s, obj);
+                                *hp++ = HEAP_ELEM_TO_BE_FILLED;
+                            }
+                        }
+                        goto cleanup_next;
+                    }
+                    case MAP_HEADER_TAG_HAMT_HEAD_BITMAP :
+                    case MAP_HEADER_TAG_HAMT_HEAD_ARRAY :
+			*hp++ = *++ptr; /* total map size */
+                    case MAP_HEADER_TAG_HAMT_NODE_BITMAP : {
+                         Uint n = hashmap_bitcount(MAP_HEADER_VAL(hdr));
+                         while (n--)  {
+                             obj = *++ptr;
+                             if (IS_CONST(obj)) {
+                                 *hp++ = obj;
+                             } else {
+                                 EQUEUE_PUT_UNCHECKED(s, obj);
+                                 *hp++ = HEAP_ELEM_TO_BE_FILLED;
+                             }
+                         }
+                        goto cleanup_next;
+                    }
+                    default:
+                        erts_exit(ERTS_ABORT_EXIT, "copy_shared_perform: bad hashmap type %d\n", MAP_HEADER_TYPE(hdr));
+                }
+	    case REFC_BINARY_SUBTAG: {
+		ProcBin* pb = (ProcBin *) ptr;
+		sz = thing_arityval(hdr);
+		if (pb->flags) {
+		    erts_emasculate_writable_binary(pb);
+		}
+		pb = (ProcBin *) hp;
+		*resp = make_binary(hp);
+		*hp++ = hdr;
+		ptr++;
+		while (sz-- > 0) {
+		    *hp++ = *ptr++;
+		}
+		erts_refc_inc(&pb->val->refc, 2);
+		pb->next = off_heap->first;
+		pb->flags = 0;
+		off_heap->first = (struct erl_off_heap_header*) pb;
+		OH_OVERHEAD(off_heap, pb->size / sizeof(Eterm));
+		goto cleanup_next;
+	    }
+	    case SUB_BINARY_SUBTAG: {
+		ErlSubBin* sb = (ErlSubBin *) ptr;
+		Eterm real_bin = sb->orig;
+		Uint bit_offset = sb->bitoffs;
+		Uint bit_size = sb->bitsize;
+		Uint offset = sb->offs;
+		size_t size = sb->size;
+		Uint extra_bytes;
+		Uint real_size;
+		if ((bit_size + bit_offset) > 8) {
+		    extra_bytes = 2;
+		} else if ((bit_size + bit_offset) > 0) {
+		    extra_bytes = 1;
+		} else {
+		    extra_bytes = 0;
+		}
+		real_size = size+extra_bytes;
+		ASSERT(is_boxed(real_bin) &&
+		       (((*boxed_val(real_bin)) &
+			 (_TAG_HEADER_MASK - _BINARY_XXX_MASK - BOXED_VISITED_MASK))
+			== _TAG_HEADER_REFC_BIN));
+		ptr = _unchecked_binary_val(real_bin);
+		*resp = make_binary(hp);
+		if (extra_bytes != 0) {
+		    ErlSubBin* res = (ErlSubBin *) hp;
+		    hp += ERL_SUB_BIN_SIZE;
+		    res->thing_word = HEADER_SUB_BIN;
+		    res->size = size;
+		    res->bitsize = bit_size;
+		    res->bitoffs = bit_offset;
+		    res->offs = 0;
+		    res->is_writable = 0;
+		    res->orig = make_binary(hp);
+		}
+		if (thing_subtag(*ptr & ~BOXED_VISITED_MASK) == HEAP_BINARY_SUBTAG) {
+		    ErlHeapBin* from = (ErlHeapBin *) ptr;
+		    ErlHeapBin* to = (ErlHeapBin *) hp;
+		    hp += heap_bin_size(real_size);
+		    to->thing_word = header_heap_bin(real_size);
+		    to->size = real_size;
+		    sys_memcpy(to->data, ((byte *)from->data)+offset, real_size);
+		} else {
+		    ProcBin* from = (ProcBin *) ptr;
+		    ProcBin* to = (ProcBin *) hp;
+		    ASSERT(thing_subtag(*ptr & ~BOXED_VISITED_MASK) == REFC_BINARY_SUBTAG);
+		    if (from->flags) {
+			erts_emasculate_writable_binary(from);
+		    }
+		    hp += PROC_BIN_SIZE;
+		    to->thing_word = HEADER_PROC_BIN;
+		    to->size = real_size;
+		    to->val = from->val;
+		    erts_refc_inc(&to->val->refc, 2);
+		    to->bytes = from->bytes + offset;
+		    to->next = off_heap->first;
+		    to->flags = 0;
+		    off_heap->first = (struct erl_off_heap_header*) to;
+		    OH_OVERHEAD(off_heap, to->size / sizeof(Eterm));
+		}
+		goto cleanup_next;
+	    }
+	    case EXTERNAL_PID_SUBTAG:
+	    case EXTERNAL_PORT_SUBTAG:
+	    case EXTERNAL_REF_SUBTAG: {
+		ExternalThing *etp = (ExternalThing *) hp;
+		sz = thing_arityval(hdr);
+		*resp = make_external(hp);
+		*hp++ = hdr;
+		ptr++;
+		while (sz-- > 0) {
+		    *hp++ = *ptr++;
+		}
+		etp->next = off_heap->first;
+		off_heap->first = (struct erl_off_heap_header*) etp;
+		erts_refc_inc(&etp->node->refc, 2);
+		goto cleanup_next;
+	    }
+	    default:
+		sz = thing_arityval(hdr);
+		*resp = make_boxed(hp);
+		*hp++ = hdr;
+		ptr++;
+		while (sz-- > 0) {
+		    *hp++ = *ptr++;
+		}
+		goto cleanup_next;
+	    }
+	    break;
+	}
+	case TAG_PRIMARY_IMMED1:
+	    *resp = obj;
+	cleanup_next:
+	    if (EQUEUE_ISEMPTY(s)) {
+		goto all_clean;
+	    }
+	    obj = EQUEUE_GET(s);
+	    for (;;) {
+		ASSERT(hscan < hp);
+		if (remaining == 0) {
+		    if (*hscan == HEAP_ELEM_TO_BE_FILLED) {
+			resp = hscan;
+			hscan += 2;
+			break; /* scanning loop */
+		    } else if (primary_tag(*hscan) == TAG_PRIMARY_HEADER) {
+			switch (*hscan & _TAG_HEADER_MASK) {
+			case ARITYVAL_SUBTAG:
+			    remaining = header_arity(*hscan);
+			    hscan++;
+			    break;
+			case FUN_SUBTAG: {
+			    ErlFunThing* funp = (ErlFunThing *) hscan;
+			    hscan += 1 + thing_arityval(*hscan);
+			    remaining = 1 + funp->num_free;
+			    break;
+			}
+			case MAP_SUBTAG:
+                            switch (MAP_HEADER_TYPE(*hscan)) {
+                                case MAP_HEADER_TAG_FLATMAP_HEAD : {
+                                    flatmap_t *mp = (flatmap_t *) hscan;
+                                    remaining = flatmap_get_size(mp) + 1;
+                                    hscan += 2;
+                                    break;
+                                }
+                                case MAP_HEADER_TAG_HAMT_HEAD_BITMAP :
+                                case MAP_HEADER_TAG_HAMT_HEAD_ARRAY :
+                                case MAP_HEADER_TAG_HAMT_NODE_BITMAP :
+                                    remaining = hashmap_bitcount(MAP_HEADER_VAL(*hscan));
+                                    hscan += MAP_HEADER_ARITY(*hscan) + 1;
+                                    break;
+                                default:
+                                    erts_exit(ERTS_ABORT_EXIT,
+                                            "copy_shared_perform: bad hashmap type %d\n",
+                                            MAP_HEADER_TYPE(*hscan));
+                            }
+                            break;
+			case SUB_BINARY_SUBTAG:
+			    ASSERT(((ErlSubBin *) hscan)->bitoffs +
+				   ((ErlSubBin *) hscan)->bitsize > 0);
+			    hscan += ERL_SUB_BIN_SIZE;
+			    break;
+			default:
+			    hscan += 1 + thing_arityval(*hscan);
+			    break;
+			}
+		    } else {
+			hscan++;
+		    }
+		} else if (*hscan == HEAP_ELEM_TO_BE_FILLED) {
+		    resp = hscan++;
+		    remaining--;
+		    break; /* scanning loop */
+		} else {
+		    hscan++;
+		    remaining--;
+		}
+	    }
+	    ASSERT(resp < hp);
+	    break;
+	default:
+	    erts_exit(ERTS_ABORT_EXIT, "size_shared: bad tag for %#x\n", obj);
+	}
+    }
+
+    /* step #4:
+       -------------------------------------------------------
+       traverse the table and reverse-transform all stored entries
+    */
+
+all_clean:
+    for (e = 0; ; e += SHTABLE_INCR) {
+	ptr = SHTABLE_REV(t, e);
+	if (ptr == NULL)
+	    break;
+	VERBOSE(DEBUG_SHCOPY, ("[copy] restoring shared: %x\n", ptr));
+	/* entry was a list */
+	if (SHTABLE_Y(t, e) != THE_NON_VALUE) {
+	    VERBOSE(DEBUG_SHCOPY, ("[pid=%T] untabling L %p\n", mypid, ptr));
+	    CAR(ptr) = SHTABLE_X(t, e);
+	    CDR(ptr) = SHTABLE_Y(t, e);
+	}
+	/* entry was boxed */
+	else {
+	    VERBOSE(DEBUG_SHCOPY, ("[pid=%T] untabling B %p\n", mypid, ptr));
+	    *ptr = SHTABLE_X(t, e);
+	    ASSERT(primary_tag(*ptr) == TAG_PRIMARY_HEADER);
+	}
+    }
+
+#ifdef DEBUG
+    if (eq(saved_obj, result) == 0) {
+	erts_fprintf(stderr, "original = %T\n", saved_obj);
+	erts_fprintf(stderr, "copy = %T\n", result);
+	erts_exit(ERTS_ABORT_EXIT, "copy (shared) not equal to source\n");
+    }
+#endif
+
+    VERBOSE(DEBUG_SHCOPY, ("[pid=%T] original was %T\n", mypid, saved_obj));
+    VERBOSE(DEBUG_SHCOPY, ("[pid=%T] copy is %T\n", mypid, result));
+    VERBOSE(DEBUG_SHCOPY, ("[pid=%T] result is at %p\n", mypid, result));
+
+    ASSERT(hbot == hp);
+    ASSERT(size == ((hp - *hpp) + (hend - hbot)));
+    *hpp = hend;
+    return result;
+}
+
+
 /*
  * Copy a term that is guaranteed to be contained in a single
  * heap block. The heap block is copied word by word, and any
@@ -563,21 +1768,12 @@ Eterm copy_struct(Eterm obj, Uint sz, Eterm** hpp, ErlOffHeap* off_heap)
  *
  * NOTE: Assumes that term is a tuple (ptr is an untagged tuple ptr).
  */
-#if HALFWORD_HEAP
-Eterm copy_shallow_rel(Eterm* ptr, Uint sz, Eterm** hpp, ErlOffHeap* off_heap,
-		       Eterm* src_base)
-#else
 Eterm copy_shallow(Eterm* ptr, Uint sz, Eterm** hpp, ErlOffHeap* off_heap)
-#endif
 {
     Eterm* tp = ptr;
     Eterm* hp = *hpp;
     const Eterm res = make_tuple(hp);
-#if HALFWORD_HEAP
-    const Sint offs = COMPRESS_POINTER(hp - (tp - src_base));
-#else
     const Sint offs = (hp - tp) * sizeof(Eterm);
-#endif
 
     while (sz--) {
 	Eterm val = *tp++;
@@ -652,17 +1848,24 @@ Eterm copy_shallow(Eterm* ptr, Uint sz, Eterm** hpp, ErlOffHeap* off_heap)
  * move markers.
  * Typically used to copy a multi-fragmented message (from NIF).
  */
-void move_multi_frags(Eterm** hpp, ErlOffHeap* off_heap, ErlHeapFragment* first,
-		      Eterm* refs, unsigned nrefs)
+void erts_move_multi_frags(Eterm** hpp, ErlOffHeap* off_heap, ErlHeapFragment* first,
+			   Eterm* refs, unsigned nrefs, int literals)
 {
     ErlHeapFragment* bp;
     Eterm* hp_start = *hpp;
     Eterm* hp_end;
     Eterm* hp;
     unsigned i;
+    Eterm literal_tag;
+
+#ifdef TAG_LITERAL_PTR
+    literal_tag = (Eterm) literals ? TAG_LITERAL_PTR : 0;
+#else
+    literal_tag = (Eterm) 0;
+#endif
 
     for (bp=first; bp!=NULL; bp=bp->next) {
-	move_one_frag(hpp, bp, off_heap);
+	move_one_frag(hpp, bp, off_heap, literals);
     }
     hp_end = *hpp;
     for (hp=hp_start; hp<hp_end; ++hp) {
@@ -675,6 +1878,9 @@ void move_multi_frags(Eterm** hpp, ErlOffHeap* off_heap, ErlHeapFragment* first,
 	    val = *ptr;
 	    if (IS_MOVED_BOXED(val)) {
 		ASSERT(is_boxed(val));
+#ifdef TAG_LITERAL_PTR
+		val |= literal_tag;
+#endif
 		*hp = val;
 	    }
 	    break;
@@ -682,7 +1888,11 @@ void move_multi_frags(Eterm** hpp, ErlOffHeap* off_heap, ErlHeapFragment* first,
 	    ptr = list_val(gval);
 	    val = *ptr;
 	    if (IS_MOVED_CONS(val)) {
-		*hp = ptr[1];
+		val = ptr[1];
+#ifdef TAG_LITERAL_PTR
+		val |= literal_tag;
+#endif
+		*hp = val;
 	    }
 	    break;
 	case TAG_PRIMARY_HEADER:
@@ -693,12 +1903,12 @@ void move_multi_frags(Eterm** hpp, ErlOffHeap* off_heap, ErlHeapFragment* first,
 	}
     }
     for (i=0; i<nrefs; ++i) {
-	refs[i] = follow_moved(refs[i]);
+	refs[i] = follow_moved(refs[i], literal_tag);
     }
 }
 
 static void
-move_one_frag(Eterm** hpp, ErlHeapFragment* frag, ErlOffHeap* off_heap)
+move_one_frag(Eterm** hpp, ErlHeapFragment* frag, ErlOffHeap* off_heap, int literals)
 {
     Eterm* ptr = frag->mem;
     Eterm* end = ptr + frag->used_size;
@@ -735,4 +1945,3 @@ move_one_frag(Eterm** hpp, ErlHeapFragment* frag, ErlOffHeap* off_heap)
     OH_OVERHEAD(off_heap, frag->off_heap.overhead);
     frag->off_heap.first = NULL;
 }
-