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, 23 insertions, 19 deletions

diff --git a/erts/emulator/beam/erl_process.c b/erts/emulator/beam/erl_process.c
index f5b1308ca4..429bdd74fb 100644
--- a/erts/emulator/beam/erl_process.c
+++ b/erts/emulator/beam/erl_process.c
@@ -91,9 +91,9 @@ do {								\
 #define ERTS_EMPTY_RUNQ(RQ) \
   ((RQ)->len == 0 && (RQ)->misc.start == NULL)
 
-extern Eterm beam_apply[];
-extern Eterm beam_exit[];
-extern Eterm beam_continue_exit[];
+extern UWord beam_apply[];
+extern UWord beam_exit[];
+extern UWord beam_continue_exit[];
 
 static Sint p_last;
 static Sint p_next;
@@ -334,7 +334,7 @@ do {									\
 static void init_processes_bif(void);
 static void save_terminating_process(Process *p);
 static void exec_misc_ops(ErtsRunQueue *);
-static void print_function_from_pc(int to, void *to_arg, Eterm* x);
+static void print_function_from_pc(int to, void *to_arg, UWord* x);
 static int stack_element_dump(int to, void *to_arg, Process* p, Eterm* sp,
 			      int yreg);
 #ifdef ERTS_SMP
@@ -2078,9 +2078,9 @@ erts_init_scheduling(int mrq, int no_schedulers, int no_schedulers_online)
 
     erts_aligned_run_queues = erts_alloc(ERTS_ALC_T_RUNQS,
 					 (sizeof(ErtsAlignedRunQueue)*(n+1)));
-    if ((((Uint) erts_aligned_run_queues) & ERTS_CACHE_LINE_MASK) == 0)
+    if ((((UWord) erts_aligned_run_queues) & ERTS_CACHE_LINE_MASK) == 0)
 	erts_aligned_run_queues = ((ErtsAlignedRunQueue *)
-				   ((((Uint) erts_aligned_run_queues)
+				   ((((UWord) erts_aligned_run_queues)
 				     & ~ERTS_CACHE_LINE_MASK)
 				    + ERTS_CACHE_LINE_SIZE));
 
@@ -2175,9 +2175,9 @@ erts_init_scheduling(int mrq, int no_schedulers, int no_schedulers_online)
     erts_aligned_scheduler_data = erts_alloc(ERTS_ALC_T_SCHDLR_DATA,
 					     (sizeof(ErtsAlignedSchedulerData)
 					      *(n+1)));
-    if ((((Uint) erts_aligned_scheduler_data) & ERTS_CACHE_LINE_MASK) == 0)
+    if ((((UWord) erts_aligned_scheduler_data) & ERTS_CACHE_LINE_MASK) == 0)
 	erts_aligned_scheduler_data = ((ErtsAlignedSchedulerData *)
-				       ((((Uint) erts_aligned_scheduler_data)
+				       ((((UWord) erts_aligned_scheduler_data)
 					 & ~ERTS_CACHE_LINE_MASK)
 					+ ERTS_CACHE_LINE_SIZE));
     for (ix = 0; ix < n; ix++) {
@@ -2186,6 +2186,10 @@ erts_init_scheduling(int mrq, int no_schedulers, int no_schedulers_online)
 	erts_bits_init_state(&esdp->erl_bits_state);
 	esdp->match_pseudo_process = NULL;
 	esdp->free_process = NULL;
+#if HALFWORD_HEAP
+	/* Registers need to be heap allocated (correct memory range) for tracing to work */
+	esdp->save_reg = erts_alloc(ERTS_ALC_T_BEAM_REGISTER, ERTS_X_REGS_ALLOCATED * sizeof(Eterm));
+#endif
 #endif
 #if !HEAP_ON_C_STACK
 	esdp->num_tmp_heap_used = 0;
@@ -4484,7 +4488,7 @@ add_pend_suspend(Process *suspendee,
 					 sizeof(ErtsPendingSuspend));
     psp->next = NULL;
 #ifdef DEBUG
-#ifdef ARCH_64
+#if defined(ARCH_64) && !HALFWORD_HEAP
     psp->end = (ErtsPendingSuspend *) 0xdeaddeaddeaddead;
 #else
     psp->end = (ErtsPendingSuspend *) 0xdeaddead;
@@ -6765,8 +6769,8 @@ erl_create_process(Process* parent, /* Parent of process (default group leader).
 
     p->current = p->initial+INITIAL_MOD;
 
-    p->i = (Eterm *) beam_apply;
-    p->cp = (Eterm *) beam_apply+1;
+    p->i = (UWord *) beam_apply;
+    p->cp = (UWord *) beam_apply+1;
 
     p->arg_reg = p->def_arg_reg;
     p->max_arg_reg = sizeof(p->def_arg_reg)/sizeof(p->def_arg_reg[0]);
@@ -7351,7 +7355,7 @@ set_proc_exiting(Process *p, Eterm reason, ErlHeapFragment *bp)
     p->freason = EXTAG_EXIT;
     KILL_CATCHES(p);
     cancel_timer(p);
-    p->i = (Eterm *) beam_exit;
+    p->i = (UWord *) beam_exit;
 }
 
 
@@ -8279,7 +8283,7 @@ continue_exit_process(Process *p
 
     ASSERT(p->status == P_EXITING);
 
-    p->i = (Eterm *) beam_continue_exit;
+    p->i = (UWord *) beam_continue_exit;
 
     if (!(curr_locks & ERTS_PROC_LOCK_STATUS)) {
 	erts_smp_proc_lock(p, ERTS_PROC_LOCK_STATUS);
@@ -8299,7 +8303,7 @@ continue_exit_process(Process *p
 static void
 timeout_proc(Process* p)
 {
-    p->i = (Eterm *) p->def_arg_reg[0];
+    p->i = *((UWord **) (UWord) p->def_arg_reg);
     p->flags |= F_TIMO;
     p->flags &= ~F_INSLPQUEUE;
 
@@ -8398,9 +8402,9 @@ erts_program_counter_info(int to, void *to_arg, Process *p)
 }
 
 static void
-print_function_from_pc(int to, void *to_arg, Eterm* x)
+print_function_from_pc(int to, void *to_arg, UWord* x)
 {
-    Eterm* addr = find_function_from_pc(x);
+    UWord* addr = find_function_from_pc(x);
     if (addr == NULL) {
         if (x == beam_exit) {
             erts_print(to, to_arg, "<terminate process>");
@@ -8434,7 +8438,7 @@ stack_element_dump(int to, void *to_arg, Process* p, Eterm* sp, int yreg)
     }
 
     if (is_CP(x)) {
-        erts_print(to, to_arg, "Return addr %p (", (Eterm *) x);
+        erts_print(to, to_arg, "Return addr %p (", (Eterm *) EXPAND_POINTER(x));
         print_function_from_pc(to, to_arg, cp_val(x));
         erts_print(to, to_arg, ")\n");
         yreg = 0;
@@ -9263,8 +9267,8 @@ init_processes_bif(void)
     processes_trap_export.code[0] = am_erlang;
     processes_trap_export.code[1] = am_processes_trap;
     processes_trap_export.code[2] = 2;
-    processes_trap_export.code[3] = (Eterm) em_apply_bif;
-    processes_trap_export.code[4] = (Eterm) &processes_trap;
+    processes_trap_export.code[3] = (UWord) em_apply_bif;
+    processes_trap_export.code[4] = (UWord) &processes_trap;
 
 #if ERTS_PROCESSES_BIF_DEBUGLEVEL >= ERTS_PROCS_DBGLVL_CHK_TERM_PROC_LIST
     erts_get_emu_time(&debug_tv_start);