Store pointers to heap data in 32-bit words

Store Erlang terms in 32-bit entities on the heap, expanding the
pointers to 64-bit when needed. This works because all terms are stored
on addresses in the 32-bit address range (the 32 most significant bits
of pointers to term data are always 0).

Introduce a new datatype called UWord (along with its companion SWord),
which is an integer having the exact same size as the machine word
(a void *), but might be larger than Eterm/Uint.

Store code as machine words, as the instructions are pointers to
executable code which might reside outside the 32-bit address range.

Continuation pointers are stored on the 32-bit stack and hence must
point to addresses in the low range, which means that loaded beam code
much be placed in the low 32-bit address range (but, as said earlier,
the instructions themselves are full words).

No Erlang term data can be stored on C stacks (enforced by an
earlier commit).

This version gives a prompt, but test cases still fail (and dump core).

The loader (and emulator loop) has instruction packing disabled.

The main issues has been in rewriting loader and actual virtual
machine. Subsystems (like distribution) does not work yet.

1 files changed, 24 insertions, 18 deletions

diff --git a/erts/emulator/beam/erl_db.c b/erts/emulator/beam/erl_db.c
index 08c448882f..959f7fa37c 100644
--- a/erts/emulator/beam/erl_db.c
+++ b/erts/emulator/beam/erl_db.c
@@ -87,7 +87,7 @@ static union {
 static struct {
     union {
 	DbTable *tb;     /* Only directly readable if slot is ALIVE */
-	Uint next_free;  /* (index<<2)|1 if slot is FREE */
+	UWord next_free;  /* (index<<2)|1 if slot is FREE */
     }u;
 } *meta_main_tab;
 
@@ -187,7 +187,7 @@ static Eterm ms_delete_all_buff[8]; /* To compare with for deletion
 
 static void fix_table_locked(Process* p, DbTable* tb);
 static void unfix_table_locked(Process* p,  DbTable* tb, db_lock_kind_t* kind);
-static void set_heir(Process* me, DbTable* tb, Eterm heir, Eterm heir_data);
+static void set_heir(Process* me, DbTable* tb, Eterm heir, UWord heir_data);
 static void free_heir_data(DbTable*);
 static void free_fixations_locked(DbTable *tb);
 
@@ -1186,7 +1186,7 @@ BIF_RETTYPE ets_new_2(BIF_ALIST_2)
     Eterm val;
     Eterm ret;
     Eterm heir;
-    Eterm heir_data;
+    UWord heir_data;
     Uint32 status;
     Sint keypos;
     int is_named, is_fine_locked;
@@ -1206,7 +1206,7 @@ BIF_RETTYPE ets_new_2(BIF_ALIST_2)
     is_named = 0;
     is_fine_locked = 0;
     heir = am_none;
-    heir_data = am_undefined;
+    heir_data = (UWord) am_undefined;
 
     list = BIF_ARG_2;
     while(is_list(list)) {
@@ -1566,9 +1566,15 @@ BIF_RETTYPE ets_delete_1(BIF_ALIST_1)
 	 * (it looks like an continuation pointer), but that is will crash the
 	 * emulator if this BIF is call traced.
 	 */
+#if HALFWORD_HEAP
+	Eterm *hp = HAlloc(BIF_P, 3);
+	hp[0] = make_pos_bignum_header(2);
+	*((UWord *) (UWord) (hp+1)) = (UWord) tb;
+#else
 	Eterm *hp = HAlloc(BIF_P, 2);
 	hp[0] = make_pos_bignum_header(1);
 	hp[1] = (Eterm) tb;
+#endif
 	BIF_TRAP1(&ets_delete_continue_exp, BIF_P, make_big(hp));
     }
     else {
@@ -1638,7 +1644,7 @@ BIF_RETTYPE ets_setopts_2(BIF_ALIST_2)
     Eterm* tp;
     Eterm opt;
     Eterm heir = THE_NON_VALUE;
-    Eterm heir_data = THE_NON_VALUE;
+    UWord heir_data = (UWord) THE_NON_VALUE;
     Uint32 protection = 0;
     DeclareTmpHeap(fakelist,2,BIF_P);
     Eterm tail;
@@ -2618,7 +2624,7 @@ void init_db(void)
 {
     DbTable init_tb;
     int i;
-    extern Eterm* em_apply_bif;
+    extern UWord* em_apply_bif;
     Eterm *hp;
     unsigned bits;
     size_t size;
@@ -2747,9 +2753,9 @@ void init_db(void)
     ets_select_delete_continue_exp.code[1] = am_atom_put("delete_trap",11);
     ets_select_delete_continue_exp.code[2] = 1;
     ets_select_delete_continue_exp.code[3] =
-	(Eterm) em_apply_bif;
+	(UWord) em_apply_bif;
     ets_select_delete_continue_exp.code[4] = 
-	(Eterm) &ets_select_delete_1;
+	(UWord) &ets_select_delete_1;
 
     /* Non visual BIF to trap to. */
     memset(&ets_select_count_continue_exp, 0, sizeof(Export));
@@ -2759,9 +2765,9 @@ void init_db(void)
     ets_select_count_continue_exp.code[1] = am_atom_put("count_trap",11);
     ets_select_count_continue_exp.code[2] = 1;
     ets_select_count_continue_exp.code[3] =
-	(Eterm) em_apply_bif;
+	(UWord) em_apply_bif;
     ets_select_count_continue_exp.code[4] = 
-	(Eterm) &ets_select_count_1;
+	(UWord) &ets_select_count_1;
 
     /* Non visual BIF to trap to. */
     memset(&ets_select_continue_exp, 0, sizeof(Export));
@@ -2771,9 +2777,9 @@ void init_db(void)
     ets_select_continue_exp.code[1] = am_atom_put("select_trap",11);
     ets_select_continue_exp.code[2] = 1;
     ets_select_continue_exp.code[3] =
-	(Eterm) em_apply_bif;
+	(UWord) em_apply_bif;
     ets_select_continue_exp.code[4] = 
-	(Eterm) &ets_select_trap_1;
+	(UWord) &ets_select_trap_1;
 
     /* Non visual BIF to trap to. */
     memset(&ets_delete_continue_exp, 0, sizeof(Export));
@@ -2781,8 +2787,8 @@ void init_db(void)
     ets_delete_continue_exp.code[0] = am_ets;
     ets_delete_continue_exp.code[1] = am_atom_put("delete_trap",11);
     ets_delete_continue_exp.code[2] = 1;
-    ets_delete_continue_exp.code[3] = (Eterm) em_apply_bif;
-    ets_delete_continue_exp.code[4] = (Eterm) &ets_delete_trap;
+    ets_delete_continue_exp.code[3] = (UWord) em_apply_bif;
+    ets_delete_continue_exp.code[4] = (UWord) &ets_delete_trap;
 
     hp = ms_delete_all_buff;
     ms_delete_all = CONS(hp, am_true, NIL);
@@ -2878,7 +2884,7 @@ static int give_away_to_heir(Process* p, DbTable* tb)
     ErtsProcLocks to_locks = ERTS_PROC_LOCK_MAIN;
     DeclareTmpHeap(buf,5,p);
     Eterm to_pid;
-    Eterm heir_data;
+    UWord heir_data;
 
     ASSERT(tb->common.owner == p->id);
     ASSERT(is_internal_pid(tb->common.heir));
@@ -3301,7 +3307,7 @@ static void free_fixations_locked(DbTable *tb)
     tb->common.fixations = NULL;
 }
 
-static void set_heir(Process* me, DbTable* tb, Eterm heir, Eterm heir_data)
+static void set_heir(Process* me, DbTable* tb, Eterm heir, UWord heir_data)
 {	
     tb->common.heir = heir;
     if (heir == am_none) {
@@ -3326,7 +3332,7 @@ static void set_heir(Process* me, DbTable* tb, Eterm heir, Eterm heir_data)
 
 	UseTmpHeap(2,me);
 	/* Make a dummy 1-tuple around data to use db_get_term() */
-	heir_data = (Eterm) db_get_term(&tb->common, NULL, 0,
+	heir_data = (UWord) db_get_term(&tb->common, NULL, 0,
 					TUPLE1(tmp,heir_data));
 	UnUseTmpHeap(2,me);
 	ASSERT(!is_immed(heir_data));
@@ -3351,7 +3357,7 @@ static BIF_RETTYPE ets_delete_trap(Process *p, Eterm cont)
 {
     int trap;
     Eterm* ptr = big_val(cont);
-    DbTable *tb = (DbTable *) ptr[1];
+    DbTable *tb = *((DbTable **) (UWord) (ptr + 1));
 
     ASSERT(*ptr == make_pos_bignum_header(1));