Add the BeamInstr data type for loaded BEAM code

For cleanliness, use BeamInstr instead of the UWord
data type to any machine-sized words that are used
for BEAM instructions. Only use UWord for untyped
words in general.

34 files changed, 583 insertions, 577 deletions

diff --git a/erts/emulator/beam/beam_bif_load.c b/erts/emulator/beam/beam_bif_load.c
index db557c27a5..8462f1c7fd 100644
--- a/erts/emulator/beam/beam_bif_load.c
+++ b/erts/emulator/beam/beam_bif_load.c
@@ -39,10 +39,10 @@ static Eterm check_process_code(Process* rp, Module* modp);
 static void delete_code(Process *c_p, ErtsProcLocks c_p_locks, Module* modp);
 static void delete_export_references(Eterm module);
 static int purge_module(int module);
-static int is_native(UWord* code);
+static int is_native(BeamInstr* code);
 static int any_heap_ref_ptrs(Eterm* start, Eterm* end, char* mod_start, Uint mod_size);
 static int any_heap_refs(Eterm* start, Eterm* end, char* mod_start, Uint mod_size);
-static void remove_from_address_table(UWord* code);
+static void remove_from_address_table(BeamInstr* code);
 
 Eterm
 load_module_2(BIF_ALIST_2)
@@ -344,8 +344,8 @@ BIF_RETTYPE finish_after_on_load_2(BIF_ALIST_2)
 	modp->code[MI_ON_LOAD_FUNCTION_PTR] = 0;
 	set_default_trace_pattern(BIF_ARG_1);
     } else if (BIF_ARG_2 == am_false) {
-	UWord* code;
-	UWord* end;
+	BeamInstr* code;
+	BeamInstr* end;
 
 	/*
 	 * The on_load function failed. Remove the loaded code.
@@ -354,7 +354,7 @@ BIF_RETTYPE finish_after_on_load_2(BIF_ALIST_2)
 	 */
 	erts_total_code_size -= modp->code_length;
 	code = modp->code;
-	end = (UWord *)((char *)code + modp->code_length);
+	end = (BeamInstr *)((char *)code + modp->code_length);
 	erts_cleanup_funs_on_purge(code, end);
 	beam_catches_delmod(modp->catches, code, modp->code_length);
 	erts_free(ERTS_ALC_T_CODE, (void *) code);
@@ -397,10 +397,10 @@ set_default_trace_pattern(Eterm module)
 static Eterm
 check_process_code(Process* rp, Module* modp)
 {
-    UWord* start;
+    BeamInstr* start;
     char* mod_start;
     Uint mod_size;
-    UWord* end;
+    BeamInstr* end;
     Eterm* sp;
 #ifndef HYBRID /* FIND ME! */
     ErlFunThing* funp;
@@ -418,7 +418,7 @@ check_process_code(Process* rp, Module* modp)
      * Pick up limits for the module.
      */
     start = modp->old_code;
-    end = (UWord *)((char *)start + modp->old_code_length);
+    end = (BeamInstr *)((char *)start + modp->old_code_length);
     mod_start = (char *) start;
     mod_size = modp->old_code_length;
 
@@ -472,11 +472,11 @@ check_process_code(Process* rp, Module* modp)
 #ifndef HYBRID /* FIND ME! */
  rescan:
     for (funp = MSO(rp).funs; funp; funp = funp->next) {
-	UWord* fun_code;
+	BeamInstr* fun_code;
 
 	fun_code = funp->fe->address;
 
-	if (INSIDE((UWord *) funp->fe->address)) {
+	if (INSIDE((BeamInstr *) funp->fe->address)) {
 	    if (done_gc) {
 		return am_true;
 	    } else {
@@ -617,8 +617,8 @@ any_heap_refs(Eterm* start, Eterm* end, char* mod_start, Uint mod_size)
 static int
 purge_module(int module)
 {
-    UWord* code;
-    UWord* end;
+    BeamInstr* code;
+    BeamInstr* end;
     Module* modp;
 
     /*
@@ -653,7 +653,7 @@ purge_module(int module)
     ASSERT(erts_total_code_size >= modp->old_code_length);
     erts_total_code_size -= modp->old_code_length;
     code = modp->old_code;
-    end = (UWord *)((char *)code + modp->old_code_length);
+    end = (BeamInstr *)((char *)code + modp->old_code_length);
     erts_cleanup_funs_on_purge(code, end);
     beam_catches_delmod(modp->old_catches, code, modp->old_code_length);
     erts_free(ERTS_ALC_T_CODE, (void *) code);
@@ -665,7 +665,7 @@ purge_module(int module)
 }
 
 static void
-remove_from_address_table(UWord* code)
+remove_from_address_table(BeamInstr* code)
 {
     int i;
 
@@ -738,11 +738,11 @@ delete_export_references(Eterm module)
 	Export *ep = export_list(i);
         if (ep != NULL && (ep->code[0] == module)) {
 	    if (ep->address == ep->code+3 &&
-		(ep->code[3] == (UWord) em_apply_bif)) {
+		(ep->code[3] == (BeamInstr) em_apply_bif)) {
 		continue;
 	    }
 	    ep->address = ep->code+3;
-	    ep->code[3] = (UWord) em_call_error_handler;
+	    ep->code[3] = (BeamInstr) em_call_error_handler;
 	    ep->code[4] = 0;
 	    MatchSetUnref(ep->match_prog_set);
 	    ep->match_prog_set = NULL;
@@ -774,7 +774,7 @@ beam_make_current_old(Process *c_p, ErtsProcLocks c_p_locks, Eterm module)
 }
 
 static int
-is_native(UWord* code)
+is_native(BeamInstr* code)
 {
     return ((Eterm *)code[MI_FUNCTIONS])[1] != 0;
 }
diff --git a/erts/emulator/beam/beam_bp.c b/erts/emulator/beam/beam_bp.c
index 0cdc2116ba..b21e70258e 100644
--- a/erts/emulator/beam/beam_bp.c
+++ b/erts/emulator/beam/beam_bp.c
@@ -109,23 +109,23 @@ do {                               \
 */
 
 static int set_break(Eterm mfa[3], int specified,
-		     Binary *match_spec, Uint break_op, 
+		     Binary *match_spec, BeamInstr break_op,
 		     enum erts_break_op count_op, Eterm tracer_pid);
 static int set_module_break(Module *modp, Eterm mfa[3], int specified,
-			    Binary *match_spec, Uint break_op,
+			    Binary *match_spec, BeamInstr break_op,
 			    enum erts_break_op count_op, Eterm tracer_pid);
-static int set_function_break(Module *modp, Uint *pc,
-			      Binary *match_spec, Uint break_op,
+static int set_function_break(Module *modp, BeamInstr *pc,
+			      Binary *match_spec, BeamInstr break_op,
 			      enum erts_break_op count_op, Eterm tracer_pid); 
 
 static int clear_break(Eterm mfa[3], int specified, 
-		       Uint break_op);
+		       BeamInstr break_op);
 static int clear_module_break(Module *modp, Eterm mfa[3], int specified, 
-			      Uint break_op);
-static int clear_function_break(Module *modp, Uint *pc, 
-				Uint break_op);
+			      BeamInstr break_op);
+static int clear_function_break(Module *modp, BeamInstr *pc,
+				BeamInstr break_op);
 
-static BpData *is_break(Uint *pc, Uint break_op);
+static BpData *is_break(BeamInstr *pc, BeamInstr break_op);
 
 
 
@@ -145,7 +145,7 @@ erts_set_trace_break(Eterm mfa[3], int specified, Binary *match_spec,
 		     Eterm tracer_pid) {
     ERTS_SMP_LC_ASSERT(erts_smp_is_system_blocked(0));
     return set_break(mfa, specified, match_spec,
-		     (Uint) BeamOp(op_i_trace_breakpoint), 0, tracer_pid);
+		     (BeamInstr) BeamOp(op_i_trace_breakpoint), 0, tracer_pid);
 }
 
 int 
@@ -153,11 +153,11 @@ erts_set_mtrace_break(Eterm mfa[3], int specified, Binary *match_spec,
 		      Eterm tracer_pid) {
     ERTS_SMP_LC_ASSERT(erts_smp_is_system_blocked(0));
     return set_break(mfa, specified, match_spec,
-		     (Uint) BeamOp(op_i_mtrace_breakpoint), 0, tracer_pid);
+		     (BeamInstr) BeamOp(op_i_mtrace_breakpoint), 0, tracer_pid);
 }
 
 void
-erts_set_mtrace_bif(Uint *pc, Binary *match_spec, Eterm tracer_pid) {
+erts_set_mtrace_bif(BeamInstr *pc, Binary *match_spec, Eterm tracer_pid) {
     BpDataTrace *bdt;
     ERTS_SMP_LC_ASSERT(erts_smp_is_system_blocked(0));
 
@@ -173,7 +173,7 @@ erts_set_mtrace_bif(Uint *pc, Binary *match_spec, Eterm tracer_pid) {
 	MatchSetRef(match_spec);
 	bdt->match_spec = match_spec;
 	bdt->tracer_pid = tracer_pid;
-	pc[-4] = (Uint) bdt;
+	pc[-4] = (BeamInstr) bdt;
     }
 }
 
@@ -181,14 +181,14 @@ int
 erts_set_debug_break(Eterm mfa[3], int specified) {
     ERTS_SMP_LC_ASSERT(erts_smp_is_system_blocked(0));
     return set_break(mfa, specified, NULL, 
-		     (Uint) BeamOp(op_i_debug_breakpoint), 0, NIL);
+		     (BeamInstr) BeamOp(op_i_debug_breakpoint), 0, NIL);
 }
 
 int 
 erts_set_count_break(Eterm mfa[3], int specified, enum erts_break_op count_op) {
     ERTS_SMP_LC_ASSERT(erts_smp_is_system_blocked(0));
     return set_break(mfa, specified, NULL, 
-		     (Uint) BeamOp(op_i_count_breakpoint), count_op, NIL);
+		     (BeamInstr) BeamOp(op_i_count_breakpoint), count_op, NIL);
 }
 
 
@@ -197,18 +197,18 @@ int
 erts_clear_trace_break(Eterm mfa[3], int specified) {
     ERTS_SMP_LC_ASSERT(erts_smp_is_system_blocked(0));
     return clear_break(mfa, specified, 
-		       (Uint) BeamOp(op_i_trace_breakpoint));
+		       (BeamInstr) BeamOp(op_i_trace_breakpoint));
 }
 
 int
 erts_clear_mtrace_break(Eterm mfa[3], int specified) {
     ERTS_SMP_LC_ASSERT(erts_smp_is_system_blocked(0));
     return clear_break(mfa, specified, 
-		       (Uint) BeamOp(op_i_mtrace_breakpoint));
+		       (BeamInstr) BeamOp(op_i_mtrace_breakpoint));
 }
 
 void
-erts_clear_mtrace_bif(Uint *pc) {
+erts_clear_mtrace_bif(BeamInstr *pc) {
     BpDataTrace *bdt;
     ERTS_SMP_LC_ASSERT(erts_smp_is_system_blocked(0));
     
@@ -219,21 +219,21 @@ erts_clear_mtrace_bif(Uint *pc) {
 	}
 	Free(bdt);
     }
-    pc[-4] = (Uint) NULL;
+    pc[-4] = (BeamInstr) NULL;
 }
 
 int
 erts_clear_debug_break(Eterm mfa[3], int specified) {
     ERTS_SMP_LC_ASSERT(erts_smp_is_system_blocked(0));
     return clear_break(mfa, specified, 
-		       (Uint) BeamOp(op_i_debug_breakpoint));
+		       (BeamInstr) BeamOp(op_i_debug_breakpoint));
 }
 
 int
 erts_clear_count_break(Eterm mfa[3], int specified) {
     ERTS_SMP_LC_ASSERT(erts_smp_is_system_blocked(0));
     return clear_break(mfa, specified, 
-		       (Uint) BeamOp(op_i_count_breakpoint));
+		       (BeamInstr) BeamOp(op_i_count_breakpoint));
 }
 
 int
@@ -250,7 +250,7 @@ erts_clear_module_break(Module *modp) {
 }
 
 int
-erts_clear_function_break(Module *modp, Uint *pc) {
+erts_clear_function_break(Module *modp, BeamInstr *pc) {
     ERTS_SMP_LC_ASSERT(erts_smp_is_system_blocked(0));
     ASSERT(modp);
     return clear_function_break(modp, pc, 0);
@@ -261,13 +261,13 @@ erts_clear_function_break(Module *modp, Uint *pc) {
 /*
  * SMP NOTE: Process p may have become exiting on return!
  */
-Uint 
-erts_trace_break(Process *p, UWord *pc, Eterm *args,
+BeamInstr
+erts_trace_break(Process *p, BeamInstr *pc, Eterm *args,
 		 Uint32 *ret_flags, Eterm *tracer_pid) {
     Eterm tpid1, tpid2;
     BpDataTrace *bdt = (BpDataTrace *) pc[-4];
-    
-    ASSERT(pc[-5] == (Uint) BeamOp(op_i_func_info_IaaI));
+
+    ASSERT(pc[-5] == (BeamInstr) BeamOp(op_i_func_info_IaaI));
     ASSERT(bdt);
     bdt = (BpDataTrace *) bdt->next;
     ASSERT(bdt);
@@ -286,7 +286,7 @@ erts_trace_break(Process *p, UWord *pc, Eterm *args,
 	bdt->tracer_pid = tpid2;
 	ErtsSmpBPUnlock(bdt);
     }
-    pc[-4] = (Uint) bdt;
+    pc[-4] = (BeamInstr) bdt;
     return bdt->orig_instr;
 }
 
@@ -296,10 +296,10 @@ erts_trace_break(Process *p, UWord *pc, Eterm *args,
  * SMP NOTE: Process p may have become exiting on return!
  */
 Uint32
-erts_bif_mtrace(Process *p, UWord *pc, Eterm *args, int local,
+erts_bif_mtrace(Process *p, BeamInstr *pc, Eterm *args, int local,
 		Eterm *tracer_pid) {
     BpDataTrace *bdt = (BpDataTrace *) pc[-4];
-    
+
     ASSERT(tracer_pid);
     if (bdt) {
 	Eterm tpid1, tpid2;
@@ -326,9 +326,9 @@ erts_bif_mtrace(Process *p, UWord *pc, Eterm *args, int local,
 
 
 int 
-erts_is_trace_break(Uint *pc, Binary **match_spec_ret, Eterm *tracer_pid_ret) {
+erts_is_trace_break(BeamInstr *pc, Binary **match_spec_ret, Eterm *tracer_pid_ret) {
     BpDataTrace *bdt = 
-	(BpDataTrace *) is_break(pc, (Uint) BeamOp(op_i_trace_breakpoint));
+	(BpDataTrace *) is_break(pc, (BeamInstr) BeamOp(op_i_trace_breakpoint));
     
     if (bdt) {
 	if (match_spec_ret) {
@@ -345,9 +345,9 @@ erts_is_trace_break(Uint *pc, Binary **match_spec_ret, Eterm *tracer_pid_ret) {
 }
 
 int 
-erts_is_mtrace_break(Uint *pc, Binary **match_spec_ret, Eterm *tracer_pid_ret) {
+erts_is_mtrace_break(BeamInstr *pc, Binary **match_spec_ret, Eterm *tracer_pid_ret) {
     BpDataTrace *bdt = 
-	(BpDataTrace *) is_break(pc, (Uint) BeamOp(op_i_mtrace_breakpoint));
+	(BpDataTrace *) is_break(pc, (BeamInstr) BeamOp(op_i_mtrace_breakpoint));
     
     if (bdt) {
 	if (match_spec_ret) {
@@ -364,7 +364,7 @@ erts_is_mtrace_break(Uint *pc, Binary **match_spec_ret, Eterm *tracer_pid_ret) {
 }
 
 int
-erts_is_mtrace_bif(UWord *pc, Binary **match_spec_ret, Eterm *tracer_pid_ret) {
+erts_is_mtrace_bif(BeamInstr *pc, Binary **match_spec_ret, Eterm *tracer_pid_ret) {
     BpDataTrace *bdt = (BpDataTrace *) pc[-4];
     
     if (bdt) {
@@ -382,20 +382,20 @@ erts_is_mtrace_bif(UWord *pc, Binary **match_spec_ret, Eterm *tracer_pid_ret) {
 }
 
 int
-erts_is_native_break(Uint *pc) {
+erts_is_native_break(BeamInstr *pc) {
 #ifdef HIPE
-    ASSERT(pc[-5] == (Uint) BeamOp(op_i_func_info_IaaI));
-    return pc[0]  == (Uint) BeamOp(op_hipe_trap_call) 
-	|| pc[0]  == (Uint) BeamOp(op_hipe_trap_call_closure);
+    ASSERT(pc[-5] == (BeamInstr) BeamOp(op_i_func_info_IaaI));
+    return pc[0]  == (BeamInstr) BeamOp(op_hipe_trap_call)
+	|| pc[0]  == (BeamInstr) BeamOp(op_hipe_trap_call_closure);
 #else
     return 0;
 #endif
 }
 
 int 
-erts_is_count_break(Uint *pc, Sint *count_ret) {
+erts_is_count_break(BeamInstr *pc, Sint *count_ret) {
     BpDataCount *bdc = 
-	(BpDataCount *) is_break(pc, (Uint) BeamOp(op_i_count_breakpoint));
+	(BpDataCount *) is_break(pc, (BeamInstr) BeamOp(op_i_count_breakpoint));
     
     if (bdc) {
 	if (count_ret) {
@@ -408,24 +408,24 @@ erts_is_count_break(Uint *pc, Sint *count_ret) {
     return 0;
 }
 
-Uint *
+BeamInstr *
 erts_find_local_func(Eterm mfa[3]) {
     Module *modp;
-    Uint** code_base;
-    Uint* code_ptr;
+    BeamInstr** code_base;
+    BeamInstr* code_ptr;
     Uint i,n;
 
     if ((modp = erts_get_module(mfa[0])) == NULL)
 	return NULL;
-    if ((code_base = (Uint **) modp->code) == NULL)
+    if ((code_base = (BeamInstr **) modp->code) == NULL)
 	return NULL;
-    n = (Uint) code_base[MI_NUM_FUNCTIONS];
+    n = (BeamInstr) code_base[MI_NUM_FUNCTIONS];
     for (i = 0; i < n; ++i) {
 	code_ptr = code_base[MI_FUNCTIONS+i];
-	ASSERT(((Uint) BeamOp(op_i_func_info_IaaI)) == code_ptr[0]);
+	ASSERT(((BeamInstr) BeamOp(op_i_func_info_IaaI)) == code_ptr[0]);
 	ASSERT(mfa[0] == ((Eterm) code_ptr[2]));
 	if (mfa[1] == ((Eterm) code_ptr[3]) &&
-	    ((Uint) mfa[2]) == code_ptr[4]) {
+	    ((BeamInstr) mfa[2]) == code_ptr[4]) {
 	    return code_ptr + 5;
 	}
     }
@@ -440,7 +440,7 @@ erts_find_local_func(Eterm mfa[3]) {
 
 
 static int set_break(Eterm mfa[3], int specified, 
-		     Binary *match_spec, Eterm break_op, 
+		     Binary *match_spec, BeamInstr break_op,
 		     enum erts_break_op count_op, Eterm tracer_pid)
 {
     Module *modp;
@@ -470,26 +470,26 @@ static int set_break(Eterm mfa[3], int specified,
 }
 
 static int set_module_break(Module *modp, Eterm mfa[3], int specified,
-			    Binary *match_spec, Uint break_op, 
+			    Binary *match_spec, BeamInstr break_op,
 			    enum erts_break_op count_op, Eterm tracer_pid) {
-    Uint** code_base;
-    Uint* code_ptr;
+    BeamInstr** code_base;
+    BeamInstr* code_ptr;
     int num_processed = 0;
     Uint i,n;
 
     ASSERT(break_op);
     ASSERT(modp);
-    code_base = (Uint **) modp->code;
+    code_base = (BeamInstr **) modp->code;
     if (code_base == NULL) {
 	return 0;
     }
-    n = (Uint) code_base[MI_NUM_FUNCTIONS];
+    n = (BeamInstr) code_base[MI_NUM_FUNCTIONS];
     for (i = 0; i < n; ++i) {
 	code_ptr = code_base[MI_FUNCTIONS+i];
-	ASSERT(code_ptr[0] == (Uint) BeamOp(op_i_func_info_IaaI));
+	ASSERT(code_ptr[0] == (BeamInstr) BeamOp(op_i_func_info_IaaI));
 	if ((specified < 2 || mfa[1] == ((Eterm) code_ptr[3])) &&
 	    (specified < 3 || ((int) mfa[2]) == ((int) code_ptr[4]))) {
-	    Uint   *pc = code_ptr+5;
+	    BeamInstr   *pc = code_ptr+5;
 	    
 	    num_processed +=
 		set_function_break(modp, pc, match_spec, 
@@ -499,16 +499,16 @@ static int set_module_break(Module *modp, Eterm mfa[3], int specified,
     return num_processed;
 }
 
-static int set_function_break(Module *modp, Uint *pc, 
-			      Binary *match_spec, Uint break_op, 
+static int set_function_break(Module *modp, BeamInstr *pc,
+			      Binary *match_spec, BeamInstr break_op,
 			      enum erts_break_op count_op, Eterm tracer_pid) {
     BpData *bd, **r;
     size_t size;
-    Uint **code_base = (Uint **)modp->code;
+    BeamInstr **code_base = (BeamInstr **)modp->code;
     
     ASSERT(code_base);
-    ASSERT(code_base <= (Uint **)pc);
-    ASSERT((Uint **)pc < code_base + (modp->code_length/sizeof(Uint *)));
+    ASSERT(code_base <= (BeamInstr **)pc);
+    ASSERT((BeamInstr **)pc < code_base + (modp->code_length/sizeof(BeamInstr *)));
     /*
      * Currently no trace support for native code.
      */
@@ -517,8 +517,8 @@ static int set_function_break(Module *modp, Uint *pc,
     }
     /* Do not allow two breakpoints of the same kind */
     if ( (bd = is_break(pc, break_op))) {
-	if (break_op == (Uint) BeamOp(op_i_trace_breakpoint) 
-	    || break_op == (Uint) BeamOp(op_i_mtrace_breakpoint)) {
+	if (break_op == (BeamInstr) BeamOp(op_i_trace_breakpoint)
+	    || break_op == (BeamInstr) BeamOp(op_i_mtrace_breakpoint)) {
 	    BpDataTrace *bdt = (BpDataTrace *) bd;
 	    Binary *old_match_spec;
 	    
@@ -533,7 +533,7 @@ static int set_function_break(Module *modp, Uint *pc,
 	} else {
 	    ASSERT(! match_spec);
 	    ASSERT(is_nil(tracer_pid));
-	    if (break_op == (Uint) BeamOp(op_i_count_breakpoint)) {
+	    if (break_op == (BeamInstr) BeamOp(op_i_count_breakpoint)) {
 		BpDataCount *bdc = (BpDataCount *) bd;
 		
 		ErtsSmpBPLock(bdc);
@@ -551,13 +551,13 @@ static int set_function_break(Module *modp, Uint *pc,
 	}
 	return 1;
     }
-    if (break_op == (Uint) BeamOp(op_i_trace_breakpoint) ||
-	break_op == (Uint) BeamOp(op_i_mtrace_breakpoint)) {
+    if (break_op == (BeamInstr) BeamOp(op_i_trace_breakpoint) ||
+	break_op == (BeamInstr) BeamOp(op_i_mtrace_breakpoint)) {
 	size = sizeof(BpDataTrace);
     } else {
 	ASSERT(! match_spec);
 	ASSERT(is_nil(tracer_pid));
-	if (break_op == (Uint) BeamOp(op_i_count_breakpoint)) {
+	if (break_op == (BeamInstr) BeamOp(op_i_count_breakpoint)) {
 	    if (count_op == erts_break_reset
 		|| count_op == erts_break_stop) {
 		/* Do not insert a new breakpoint */
@@ -566,27 +566,27 @@ static int set_function_break(Module *modp, Uint *pc,
 	    size = sizeof(BpDataCount);
 	} else {
 	    ASSERT(! count_op);
-	    ASSERT(break_op == (Uint) BeamOp(op_i_debug_breakpoint));
+	    ASSERT(break_op == (BeamInstr) BeamOp(op_i_debug_breakpoint));
 	    size = sizeof(BpDataDebug);
 	}
     }
     r = (BpData **) (pc-4);
     if (! *r) {
-	ASSERT(*pc != (Uint) BeamOp(op_i_trace_breakpoint));
-	ASSERT(*pc != (Uint) BeamOp(op_i_mtrace_breakpoint));
-	ASSERT(*pc != (Uint) BeamOp(op_i_debug_breakpoint));
-	ASSERT(*pc != (Uint) BeamOp(op_i_count_breakpoint));
+	ASSERT(*pc != (BeamInstr) BeamOp(op_i_trace_breakpoint));
+	ASSERT(*pc != (BeamInstr) BeamOp(op_i_mtrace_breakpoint));
+	ASSERT(*pc != (BeamInstr) BeamOp(op_i_debug_breakpoint));
+	ASSERT(*pc != (BeamInstr) BeamOp(op_i_count_breakpoint));
 	/* First breakpoint; create singleton ring */
 	bd = Alloc(size);
 	BpInit(bd, *pc);
 	*pc = break_op;
 	*r = bd;
     } else {
-	ASSERT(*pc == (Uint) BeamOp(op_i_trace_breakpoint) ||
-	       *pc == (Uint) BeamOp(op_i_mtrace_breakpoint) ||
-	       *pc == (Uint) BeamOp(op_i_debug_breakpoint) ||
-	       *pc == (Uint) BeamOp(op_i_count_breakpoint));
-	if (*pc == (Uint) BeamOp(op_i_debug_breakpoint)) {
+	ASSERT(*pc == (BeamInstr) BeamOp(op_i_trace_breakpoint) ||
+	       *pc == (BeamInstr) BeamOp(op_i_mtrace_breakpoint) ||
+	       *pc == (BeamInstr) BeamOp(op_i_debug_breakpoint) ||
+	       *pc == (BeamInstr) BeamOp(op_i_count_breakpoint));
+	if (*pc == (BeamInstr) BeamOp(op_i_debug_breakpoint)) {
 	    /* Debug bp must be last, so if it is also first; 
 	     * it must be singleton. */
 	    ASSERT(BpSingleton(*r)); 
@@ -595,7 +595,7 @@ static int set_function_break(Module *modp, Uint *pc,
 	    BpInitAndSpliceNext(bd, *pc, *r);
 	    *pc = break_op;
 	} else if ((*r)->prev->orig_instr 
-		   == (Uint) BeamOp(op_i_debug_breakpoint)) {
+		   == (BeamInstr) BeamOp(op_i_debug_breakpoint)) {
 	    /* Debug bp last in the ring; insert new second to last. */
 	    bd = Alloc(size);
 	    BpInitAndSplicePrev(bd, (*r)->prev->orig_instr, *r);
@@ -609,24 +609,24 @@ static int set_function_break(Module *modp, Uint *pc,
 	}
     }
     /* Init the bp type specific data */
-    if (break_op == (Uint) BeamOp(op_i_trace_breakpoint) ||
-	break_op == (Uint) BeamOp(op_i_mtrace_breakpoint)) {
+    if (break_op == (BeamInstr) BeamOp(op_i_trace_breakpoint) ||
+	break_op == (BeamInstr) BeamOp(op_i_mtrace_breakpoint)) {
 		
 	BpDataTrace *bdt = (BpDataTrace *) bd;
 		
 	MatchSetRef(match_spec);
 	bdt->match_spec = match_spec;
 	bdt->tracer_pid = tracer_pid;
-    } else if (break_op == (Uint) BeamOp(op_i_count_breakpoint)) {
+    } else if (break_op == (BeamInstr) BeamOp(op_i_count_breakpoint)) {
 	BpDataCount *bdc = (BpDataCount *) bd;
 
 	bdc->count = 0;
     }
-    ++(*(Uint*)&code_base[MI_NUM_BREAKPOINTS]);
+    ++(*(BeamInstr*)&code_base[MI_NUM_BREAKPOINTS]);
     return 1;
 }
 
-static int clear_break(Eterm mfa[3], int specified, Uint break_op)
+static int clear_break(Eterm mfa[3], int specified, BeamInstr break_op)
 {
     int num_processed = 0;
     Module *modp;
@@ -652,23 +652,24 @@ static int clear_break(Eterm mfa[3], int specified, Uint break_op)
 }
 
 static int clear_module_break(Module *m, Eterm mfa[3], int specified, 
-			      Uint break_op) {
-    Uint** code_base;
-    Uint* code_ptr;
+			      BeamInstr break_op) {
+    BeamInstr** code_base;
+    BeamInstr* code_ptr;
     int num_processed = 0;
-    Uint i,n;
+    Uint i;
+    BeamInstr n;
     
     ASSERT(m);
-    code_base = (Uint **) m->code;
+    code_base = (BeamInstr **) m->code;
     if (code_base == NULL) {
 	return 0;
     }
-    n = (Uint) code_base[MI_NUM_FUNCTIONS];
+    n = (BeamInstr) code_base[MI_NUM_FUNCTIONS];
     for (i = 0; i < n; ++i) {
 	code_ptr = code_base[MI_FUNCTIONS+i];
 	if ((specified < 2 || mfa[1] == ((Eterm) code_ptr[3])) &&
 	    (specified < 3 || ((int) mfa[2]) == ((int) code_ptr[4]))) {
-	    Uint *pc = code_ptr + 5;
+	    BeamInstr *pc = code_ptr + 5;
 	    
 	    num_processed += 
 		clear_function_break(m, pc, break_op);
@@ -677,13 +678,13 @@ static int clear_module_break(Module *m, Eterm mfa[3], int specified,
     return num_processed;
 }
 
-static int clear_function_break(Module *m, Uint *pc, Uint break_op) {
+static int clear_function_break(Module *m, BeamInstr *pc, BeamInstr break_op) {
     BpData *bd;
-    Uint **code_base = (Uint **)m->code;
+    BeamInstr **code_base = (BeamInstr **)m->code;
     
     ASSERT(code_base);
-    ASSERT(code_base <= (Uint **)pc);
-    ASSERT((Uint **)pc < code_base + (m->code_length/sizeof(Uint *)));
+    ASSERT(code_base <= (BeamInstr **)pc);
+    ASSERT((BeamInstr **)pc < code_base + (m->code_length/sizeof(BeamInstr *)));
     /*
      * Currently no trace support for native code.
      */
@@ -695,7 +696,7 @@ static int clear_function_break(Module *m, Uint *pc, Uint break_op) {
 	 * There should be only one of each type, 
 	 * but break_op may be 0 which matches any type. 
 	 */
-	Uint op;
+	BeamInstr op;
 	BpData **r = (BpData **) (pc-4);
 	
 	ASSERT(*r);
@@ -731,16 +732,16 @@ static int clear_function_break(Module *m, Uint *pc, Uint break_op) {
 		bd_prev->orig_instr = bd->orig_instr;
 	    }
 	}
-	if (op == (Uint) BeamOp(op_i_trace_breakpoint) ||
-	    op == (Uint) BeamOp(op_i_mtrace_breakpoint)) {
+	if (op == (BeamInstr) BeamOp(op_i_trace_breakpoint) ||
+	    op == (BeamInstr) BeamOp(op_i_mtrace_breakpoint)) {
 	    
 	    BpDataTrace *bdt = (BpDataTrace *) bd;
-	    
+
 	    MatchSetUnref(bdt->match_spec);
 	}
 	Free(bd);
-	ASSERT(((Uint) code_base[MI_NUM_BREAKPOINTS]) > 0);
-	--(*(Uint*)&code_base[MI_NUM_BREAKPOINTS]);
+	ASSERT(((BeamInstr) code_base[MI_NUM_BREAKPOINTS]) > 0);
+	--(*(BeamInstr*)&code_base[MI_NUM_BREAKPOINTS]);
     }
     return 1;
 }
@@ -754,8 +755,8 @@ static int clear_function_break(Module *m, Uint *pc, Uint break_op) {
 ** returned. The program counter must point to the first executable
 ** (breakpoint) instruction of the function.
 */
-static BpData *is_break(Uint *pc, Uint break_op) {
-    ASSERT(pc[-5] == (Uint) BeamOp(op_i_func_info_IaaI));
+static BpData *is_break(BeamInstr *pc, BeamInstr break_op) {
+    ASSERT(pc[-5] == (BeamInstr) BeamOp(op_i_func_info_IaaI));
     if (! erts_is_native_break(pc)) {
 	BpData *bd = (BpData *) pc[-4];
 	
diff --git a/erts/emulator/beam/beam_bp.h b/erts/emulator/beam/beam_bp.h
index 44b463d39c..52a36db339 100644
--- a/erts/emulator/beam/beam_bp.h
+++ b/erts/emulator/beam/beam_bp.h
@@ -48,7 +48,7 @@
 typedef struct bp_data {
     struct bp_data *next; /* Doubly linked ring pointers */
     struct bp_data *prev; /* -"-                         */
-    Uint orig_instr;      /* The original instruction to execute */
+    BeamInstr orig_instr;      /* The original instruction to execute */
 } BpData;
 /*
 ** All the following bp_data_.. structs must begin the same way
@@ -57,21 +57,21 @@ typedef struct bp_data {
 typedef struct bp_data_trace {
     struct bp_data *next;
     struct bp_data *prev;
-    Uint            orig_instr;
+    BeamInstr      orig_instr;
     Binary         *match_spec;
-    Eterm           tracer_pid;
+    Eterm          tracer_pid;
 } BpDataTrace;
 
 typedef struct bp_data_debug {
     struct bp_data *next;
     struct bp_data *prev;
-    Uint            orig_instr;
+    BeamInstr      orig_instr;
 } BpDataDebug;
 
 typedef struct bp_data_count { /* Call count */
     struct bp_data *next;
     struct bp_data *prev;
-    Uint            orig_instr;
+    BeamInstr       orig_instr;
     Sint            count;
 } BpDataCount;
 
@@ -89,11 +89,11 @@ extern erts_smp_spinlock_t erts_bp_lock;
 do {                                                        \
     BpDataCount *bdc = (BpDataCount *) (pc)[-4];            \
                                                             \
-    ASSERT((pc)[-5] == (UWord) BeamOp(op_i_func_info_IaaI)); \
+    ASSERT((pc)[-5] == (BeamInstr) BeamOp(op_i_func_info_IaaI)); \
     ASSERT(bdc);                                            \
     bdc = (BpDataCount *) bdc->next;                        \
     ASSERT(bdc);                                            \
-    (pc)[-4] = (UWord) bdc;                                  \
+    (pc)[-4] = (BeamInstr) bdc;                                  \
     ErtsSmpBPLock(bdc);                                     \
     if (bdc->count >= 0) bdc->count++;                      \
     ErtsSmpBPUnlock(bdc);                                   \
@@ -104,11 +104,11 @@ do {                                                        \
 do {                                                        \
     BpData *bd = (BpData *) (pc)[-4];                       \
                                                             \
-    ASSERT((pc)[-5] == (UWord) BeamOp(op_i_func_info_IaaI)); \
+    ASSERT((pc)[-5] == (BeamInstr) BeamOp(op_i_func_info_IaaI)); \
     ASSERT(bd);                                             \
     bd = bd->next;                                          \
     ASSERT(bd);                                             \
-    (pc)[-4] = (UWord) bd;                                   \
+    (pc)[-4] = (BeamInstr) bd;                                   \
     *(instr_result) = bd->orig_instr;                       \
 } while (0)
 
@@ -133,9 +133,9 @@ int erts_clear_trace_break(Eterm mfa[3], int specified);
 int erts_set_mtrace_break(Eterm mfa[3], int specified, Binary *match_spec,
 			  Eterm tracer_pid);
 int erts_clear_mtrace_break(Eterm mfa[3], int specified);
-void erts_set_mtrace_bif(Uint *pc, Binary *match_spec, 
+void erts_set_mtrace_bif(BeamInstr *pc, Binary *match_spec,
 			 Eterm tracer_pid);
-void erts_clear_mtrace_bif(Uint *pc);
+void erts_clear_mtrace_bif(BeamInstr *pc);
 int erts_set_debug_break(Eterm mfa[3], int specified);
 int erts_clear_debug_break(Eterm mfa[3], int specified);
 int erts_set_count_break(Eterm mfa[3], int specified, enum erts_break_op);
@@ -144,22 +144,22 @@ int erts_clear_count_break(Eterm mfa[3], int specified);
 
 int erts_clear_break(Eterm mfa[3], int specified);
 int erts_clear_module_break(Module *modp);
-int erts_clear_function_break(Module *modp, Uint *pc);
+int erts_clear_function_break(Module *modp, BeamInstr *pc);
 
-Uint erts_trace_break(Process *p, UWord *pc, Eterm *args,
+BeamInstr erts_trace_break(Process *p, BeamInstr *pc, Eterm *args,
 		      Uint32 *ret_flags, Eterm *tracer_pid);
-Uint32 erts_bif_mtrace(Process *p, UWord *pc, Eterm *args,
+Uint32 erts_bif_mtrace(Process *p, BeamInstr *pc, Eterm *args,
 		       int local, Eterm *tracer_pid);
 
-int erts_is_trace_break(Uint *pc, Binary **match_spec_ret,
+int erts_is_trace_break(BeamInstr *pc, Binary **match_spec_ret,
 			Eterm *tracer_pid_ret);
-int erts_is_mtrace_break(Uint *pc, Binary **match_spec_ret, 
+int erts_is_mtrace_break(BeamInstr *pc, Binary **match_spec_ret,
 			 Eterm *tracer_pid_rte);
-int erts_is_mtrace_bif(UWord *pc, Binary **match_spec_ret,
+int erts_is_mtrace_bif(BeamInstr *pc, Binary **match_spec_ret,
 		       Eterm *tracer_pid_ret);
-int erts_is_native_break(Uint *pc);
-int erts_is_count_break(Uint *pc, Sint *count_ret);
+int erts_is_native_break(BeamInstr *pc);
+int erts_is_count_break(BeamInstr *pc, Sint *count_ret);
 
-Uint *erts_find_local_func(Eterm mfa[3]);
+BeamInstr *erts_find_local_func(Eterm mfa[3]);
 
 #endif /* _BEAM_BP_H */
diff --git a/erts/emulator/beam/beam_catches.c b/erts/emulator/beam/beam_catches.c
index af99b0499a..97258e179b 100644
--- a/erts/emulator/beam/beam_catches.c
+++ b/erts/emulator/beam/beam_catches.c
@@ -26,7 +26,7 @@
 /* XXX: should use dynamic reallocation */
 #define TABSIZ (16*1024)
 static struct {
-    UWord *cp;
+    BeamInstr *cp;
     unsigned cdr;
 } beam_catches[TABSIZ];
 
@@ -39,7 +39,7 @@ void beam_catches_init(void)
     high_mark = 0;
 }
 
-unsigned beam_catches_cons(UWord *cp, unsigned cdr)
+unsigned beam_catches_cons(BeamInstr *cp, unsigned cdr)
 {
     int i;
 
@@ -65,7 +65,7 @@ unsigned beam_catches_cons(UWord *cp, unsigned cdr)
     return i;
 }
 
-UWord *beam_catches_car(unsigned i)
+BeamInstr *beam_catches_car(unsigned i)
 {
     if( i >= TABSIZ ) {
 	fprintf(stderr,
@@ -75,7 +75,7 @@ UWord *beam_catches_car(unsigned i)
     return beam_catches[i].cp;
 }
 
-void beam_catches_delmod(unsigned head, UWord *code, unsigned code_bytes)
+void beam_catches_delmod(unsigned head, BeamInstr *code, unsigned code_bytes)
 {
     unsigned i, cdr;
 
diff --git a/erts/emulator/beam/beam_catches.h b/erts/emulator/beam/beam_catches.h
index 0769d47263..611207e968 100644
--- a/erts/emulator/beam/beam_catches.h
+++ b/erts/emulator/beam/beam_catches.h
@@ -23,9 +23,9 @@
 #define BEAM_CATCHES_NIL	(-1)
 
 void beam_catches_init(void);
-unsigned beam_catches_cons(UWord* cp, unsigned cdr);
-UWord *beam_catches_car(unsigned i);
-void beam_catches_delmod(unsigned head, UWord* code, unsigned code_bytes);
+unsigned beam_catches_cons(BeamInstr* cp, unsigned cdr);
+BeamInstr *beam_catches_car(unsigned i);
+void beam_catches_delmod(unsigned head, BeamInstr* code, unsigned code_bytes);
 
 #define catch_pc(x)	beam_catches_car(catch_val((x)))
 
diff --git a/erts/emulator/beam/beam_debug.c b/erts/emulator/beam/beam_debug.c
index 5680a93afd..43dcebd0fb 100644
--- a/erts/emulator/beam/beam_debug.c
+++ b/erts/emulator/beam/beam_debug.c
@@ -43,13 +43,13 @@
 #else
 # define HEXF "%08bpX"
 #endif
-#define TermWords(t) (((t) / (sizeof(UWord)/sizeof(Eterm))) + !!((t) % (sizeof(UWord)/sizeof(Eterm))))
+#define TermWords(t) (((t) / (sizeof(BeamInstr)/sizeof(Eterm))) + !!((t) % (sizeof(BeamInstr)/sizeof(Eterm))))
 
 void dbg_bt(Process* p, Eterm* sp);
-void dbg_where(UWord* addr, Eterm x0, Eterm* reg);
+void dbg_where(BeamInstr* addr, Eterm x0, Eterm* reg);
 
 static void print_big(int to, void *to_arg, Eterm* addr);
-static int print_op(int to, void *to_arg, int op, int size, UWord* addr);
+static int print_op(int to, void *to_arg, int op, int size, BeamInstr* addr);
 Eterm
 erts_debug_same_2(Process* p, Eterm term1, Eterm term2)
 {
@@ -133,16 +133,16 @@ erts_debug_disassemble_1(Process* p, Eterm addr)
     Eterm* tp;
     Eterm bin;
     Eterm mfa;
-    UWord* funcinfo = NULL;	/* Initialized to eliminate warning. */
-    UWord* code_base;
-    UWord* code_ptr = NULL;	/* Initialized to eliminate warning. */
-    UWord instr;
-    UWord uaddr;
+    BeamInstr* funcinfo = NULL;	/* Initialized to eliminate warning. */
+    BeamInstr* code_base;
+    BeamInstr* code_ptr = NULL;	/* Initialized to eliminate warning. */
+    BeamInstr instr;
+    BeamInstr uaddr;
     Uint hsz;
     int i;
 
     if (term_to_UWord(addr, &uaddr)) {
-	code_ptr = (UWord *) uaddr;
+	code_ptr = (BeamInstr *) uaddr;
 	if ((funcinfo = find_function_from_pc(code_ptr)) == NULL) {
 	    BIF_RET(am_false);
 	}
@@ -181,14 +181,14 @@ erts_debug_disassemble_1(Process* p, Eterm addr)
 	     * But this code_ptr will point to the start of the Export,
 	     * not the function's func_info instruction. BOOM !?
 	     */
-	    code_ptr = ((UWord *) ep->address) - 5;
+	    code_ptr = ((BeamInstr *) ep->address) - 5;
 	    funcinfo = code_ptr+2;
 	} else if (modp == NULL || (code_base = modp->code) == NULL) {
 	    BIF_RET(am_undef);
 	} else {
 	    n = code_base[MI_NUM_FUNCTIONS];
 	    for (i = 0; i < n; i++) {
-		code_ptr = (UWord *) code_base[MI_FUNCTIONS+i];
+		code_ptr = (BeamInstr *) code_base[MI_FUNCTIONS+i];
 		if (code_ptr[3] == name && code_ptr[4] == arity) {
 		    funcinfo = code_ptr+2;
 		    break;
@@ -204,9 +204,9 @@ erts_debug_disassemble_1(Process* p, Eterm addr)
 
     dsbufp = erts_create_tmp_dsbuf(0);
     erts_print(ERTS_PRINT_DSBUF, (void *) dsbufp, HEXF ": ", code_ptr);
-    instr = (UWord) code_ptr[0];
+    instr = (BeamInstr) code_ptr[0];
     for (i = 0; i < NUM_SPECIFIC_OPS; i++) {
-	if (instr == (UWord) BeamOp(i) && opc[i].name[0] != '\0') {
+	if (instr == (BeamInstr) BeamOp(i) && opc[i].name[0] != '\0') {
 	    code_ptr += print_op(ERTS_PRINT_DSBUF, (void *) dsbufp,
 				 i, opc[i].sz-1, code_ptr+1) + 1;
 	    break;
@@ -220,9 +220,9 @@ erts_debug_disassemble_1(Process* p, Eterm addr)
     bin = new_binary(p, (byte *) dsbufp->str, (int) dsbufp->str_len);
     erts_destroy_tmp_dsbuf(dsbufp);
     hsz = 4+4;
-    (void) erts_bld_uword(NULL, &hsz, (UWord) code_ptr);
+    (void) erts_bld_uword(NULL, &hsz, (BeamInstr) code_ptr);
     hp = HAlloc(p, hsz);
-    addr = erts_bld_uword(&hp, NULL, (UWord) code_ptr);
+    addr = erts_bld_uword(&hp, NULL, (BeamInstr) code_ptr);
     ASSERT(is_atom(funcinfo[0]));
     ASSERT(is_atom(funcinfo[1]));
     mfa = TUPLE3(hp, (Eterm) funcinfo[0], (Eterm) funcinfo[1], make_small((Eterm) funcinfo[2]));
@@ -237,7 +237,7 @@ dbg_bt(Process* p, Eterm* sp)
 
     while (sp < stack) {
 	if (is_CP(*sp)) {
-	    UWord* addr = find_function_from_pc(cp_val(*sp));
+	    BeamInstr* addr = find_function_from_pc(cp_val(*sp));
 	    if (addr)
 		erts_fprintf(stderr,
 			     HEXF ": %T:%T/%bpu\n",
@@ -248,9 +248,9 @@ dbg_bt(Process* p, Eterm* sp)
 }
 
 void
-dbg_where(UWord* addr, Eterm x0, Eterm* reg)
+dbg_where(BeamInstr* addr, Eterm x0, Eterm* reg)
 {
-    UWord* f = find_function_from_pc(addr);
+    BeamInstr* f = find_function_from_pc(addr);
 
     if (f == NULL) {
 	erts_fprintf(stderr, "???\n");
@@ -268,18 +268,18 @@ dbg_where(UWord* addr, Eterm x0, Eterm* reg)
 }
 
 static int
-print_op(int to, void *to_arg, int op, int size, UWord* addr)
+print_op(int to, void *to_arg, int op, int size, BeamInstr* addr)
 {
     int i;
-    UWord tag;
+    BeamInstr tag;
     char* sign;
     char* start_prog;		/* Start of program for packer. */
     char* prog;			/* Current position in packer program. */
-    UWord stack[8];		/* Stack for packer. */
-    UWord* sp = stack;		/* Points to next free position. */
-    UWord packed = 0;		/* Accumulator for packed operations. */
-    UWord args[8];		/* Arguments for this instruction. */
-    UWord* ap;			/* Pointer to arguments. */
+    BeamInstr stack[8];		/* Stack for packer. */
+    BeamInstr* sp = stack;		/* Points to next free position. */
+    BeamInstr packed = 0;		/* Accumulator for packed operations. */
+    BeamInstr args[8];		/* Arguments for this instruction. */
+    BeamInstr* ap;			/* Pointer to arguments. */
 
     start_prog = opc[op].pack;
 
@@ -289,7 +289,7 @@ print_op(int to, void *to_arg, int op, int size, UWord* addr)
 	 * Avoid copying because instructions containing bignum operands
 	 * are bigger than actually declared.
 	 */
-	ap = (UWord *) addr;
+	ap = (BeamInstr *) addr;
     } else {
 	/*
 	 * Copy all arguments to a local buffer for the unpacking.
@@ -423,8 +423,8 @@ print_op(int to, void *to_arg, int op, int size, UWord* addr)
 	    break;
 	case 'f':		/* Destination label */
 	    {
-		UWord* f = find_function_from_pc((UWord *)*ap);
-		if (f+3 != (UWord *) *ap) {
+		BeamInstr* f = find_function_from_pc((BeamInstr *)*ap);
+		if (f+3 != (BeamInstr *) *ap) {
 		    erts_print(to, to_arg, "f(" HEXF ")", *ap);
 		} else {
 		    erts_print(to, to_arg, "%T:%T/%bpu", (Eterm) f[0], (Eterm) f[1], (Eterm) f[2]);
@@ -434,8 +434,8 @@ print_op(int to, void *to_arg, int op, int size, UWord* addr)
 	    break;
 	case 'p':		/* Pointer (to label) */
 	    {
-		UWord* f = find_function_from_pc((UWord *)*ap);
-		if (f+3 != (UWord *) *ap) {
+		BeamInstr* f = find_function_from_pc((BeamInstr *)*ap);
+		if (f+3 != (BeamInstr *) *ap) {
 		    erts_print(to, to_arg, "p(" HEXF ")", *ap);
 		} else {
 		    erts_print(to, to_arg, "%T:%T/%bpu", (Eterm) f[0], (Eterm) f[1], (Eterm) f[2]);
@@ -474,7 +474,7 @@ print_op(int to, void *to_arg, int op, int size, UWord* addr)
 	    ap++;
 	    break;
 	case 'P':	/* Byte offset into tuple (see beam_load.c) */
-	    erts_print(to, to_arg, "%d", (*ap / sizeof(UWord)) - 1);
+	    erts_print(to, to_arg, "%d", (*ap / sizeof(BeamInstr)) - 1);
 	    ap++;
 	    break;
 	case 'l':		/* fr(N) */
diff --git a/erts/emulator/beam/beam_emu.c b/erts/emulator/beam/beam_emu.c
index d542c56e28..8113e78583 100644
--- a/erts/emulator/beam/beam_emu.c
+++ b/erts/emulator/beam/beam_emu.c
@@ -117,7 +117,7 @@ do {                                     \
 #endif
 
 #define GET_BIF_ADDRESS(p) ((BifFunction) (((Export *) p)->code[4]))
-#define TermWords(t) (((t) / (sizeof(UWord)/sizeof(Eterm))) + !!((t) % (sizeof(UWord)/sizeof(Eterm))))
+#define TermWords(t) (((t) / (sizeof(BeamInstr)/sizeof(Eterm))) + !!((t) % (sizeof(BeamInstr)/sizeof(Eterm))))
 
 
 /*
@@ -182,11 +182,11 @@ do {                                     \
  
 #define StoreBifResult(Dst, Result)                          \
   do {                                                       \
-    UWord* stb_next;                                         \
+    BeamInstr* stb_next;                                         \
     Eterm stb_reg;                                           \
     stb_reg = Arg(Dst);                                      \
     I += (Dst) + 2;                                          \
-    stb_next = (UWord *) *I;                                 \
+    stb_next = (BeamInstr *) *I;                                 \
     CHECK_TERM(Result);                                      \
     switch (beam_reg_tag(stb_reg)) {                         \
     case R_REG_DEF:                                          \
@@ -206,7 +206,7 @@ do {                                     \
       c_p->cp = 0;				\
    } while(0)
 
-#define RESTORE_CP(X)		SET_CP(c_p, (UWord *) cp_val(*(X)))
+#define RESTORE_CP(X)		SET_CP(c_p, (BeamInstr *) cp_val(*(X)))
 
 #define ISCATCHEND(instr) ((Eterm *) *(instr) == OpCode(catch_end_y))
 
@@ -214,13 +214,13 @@ do {                                     \
  * Special Beam instructions.
  */
 
-UWord beam_apply[2];
-UWord beam_exit[1];
-UWord beam_continue_exit[1];
+BeamInstr beam_apply[2];
+BeamInstr beam_exit[1];
+BeamInstr beam_continue_exit[1];
 
-UWord* em_call_error_handler;
-UWord* em_apply_bif;
-UWord* em_call_traced_function;
+BeamInstr* em_call_error_handler;
+BeamInstr* em_apply_bif;
+BeamInstr* em_call_traced_function;
 
 
 /* NOTE These should be the only variables containing trace instructions.
@@ -228,9 +228,9 @@ UWord* em_call_traced_function;
 **      for the refering variable (one of these), and rouge references
 **      will most likely cause chaos.
 */
-UWord beam_return_to_trace[1]; /* OpCode(i_return_to_trace) */
-UWord beam_return_trace[1];    /* OpCode(i_return_trace) */
-UWord beam_exception_trace[1]; /* UGLY also OpCode(i_return_trace) */
+BeamInstr beam_return_to_trace[1]; /* OpCode(i_return_to_trace) */
+BeamInstr beam_return_trace[1];    /* OpCode(i_return_trace) */
+BeamInstr beam_exception_trace[1]; /* UGLY also OpCode(i_return_trace) */
 
 /*
  * All Beam instructions in numerical order.
@@ -523,8 +523,8 @@ extern int count_instructions;
 
 #define DispatchMacro()				\
   do {						\
-     UWord* dis_next;				\
-     dis_next = (UWord *) *I;			\
+     BeamInstr* dis_next;				\
+     dis_next = (BeamInstr *) *I;			\
      CHECK_ARGS(I);				\
      if (FCALLS > 0 || FCALLS > neg_o_reds) {	\
         FCALLS--;				\
@@ -536,8 +536,8 @@ extern int count_instructions;
 
 #define DispatchMacroFun()			\
   do {						\
-     UWord* dis_next;				\
-     dis_next = (UWord *) *I;			\
+     BeamInstr* dis_next;				\
+     dis_next = (BeamInstr *) *I;			\
      CHECK_ARGS(I);				\
      if (FCALLS > 0 || FCALLS > neg_o_reds) {	\
         FCALLS--;				\
@@ -591,7 +591,7 @@ extern int count_instructions;
     ASSERT(VALID_INSTR(*I));   \
     Goto(*I)
 
-#define PreFetch(N, Dst) do { Dst = (UWord *) *(I + N + 1); } while (0)
+#define PreFetch(N, Dst) do { Dst = (BeamInstr *) *(I + N + 1); } while (0)
 #define NextPF(N, Dst)         \
     I += N + 1;                \
     ASSERT(VALID_INSTR(Dst));  \
@@ -645,7 +645,7 @@ extern int count_instructions;
 #define DeallocateReturn(Deallocate)       \
   do {                                     \
     int words_to_pop = (Deallocate);       \
-    SET_I((UWord *) cp_val(*E));                     \
+    SET_I((BeamInstr *) cp_val(*E));                     \
     E = ADD_BYTE_OFFSET(E, words_to_pop);  \
     CHECK_TERM(r(0));                      \
     Goto(*I);                              \
@@ -658,19 +658,19 @@ extern int count_instructions;
 #define MoveCall(Src, Dest, CallDest, Size)	\
     (Dest) = (Src);				\
     SET_CP(c_p, I+Size+1);			\
-    SET_I((UWord *) CallDest);			\
+    SET_I((BeamInstr *) CallDest);			\
     Dispatch();
 
 #define MoveCallLast(Src, Dest, CallDest, Deallocate)	\
     (Dest) = (Src);					\
     RESTORE_CP(E);					\
     E = ADD_BYTE_OFFSET(E, (Deallocate));		\
-    SET_I((UWord *) CallDest);				\
+    SET_I((BeamInstr *) CallDest);				\
     Dispatch();
 
 #define MoveCallOnly(Src, Dest, CallDest)	\
     (Dest) = (Src);				\
-    SET_I((UWord *) CallDest);			\
+    SET_I((BeamInstr *) CallDest);			\
     Dispatch();
 
 #define GetList(Src, H, T) do {			\
@@ -984,23 +984,23 @@ extern int count_instructions;
 #define IsRef(Src, Fail) if (is_not_ref(Src)) { Fail; }
 
 static BifFunction translate_gc_bif(void* gcf);
-static UWord* handle_error(Process* c_p, UWord* pc, Eterm* reg, BifFunction bf);
-static UWord* next_catch(Process* c_p, Eterm *reg);
+static BeamInstr* handle_error(Process* c_p, BeamInstr* pc, Eterm* reg, BifFunction bf);
+static BeamInstr* next_catch(Process* c_p, Eterm *reg);
 static void terminate_proc(Process* c_p, Eterm Value);
 static Eterm add_stacktrace(Process* c_p, Eterm Value, Eterm exc);
-static void save_stacktrace(Process* c_p, UWord* pc, Eterm* reg,
+static void save_stacktrace(Process* c_p, BeamInstr* pc, Eterm* reg,
 			     BifFunction bf, Eterm args);
 static struct StackTrace * get_trace_from_exc(Eterm exc);
 static Eterm make_arglist(Process* c_p, Eterm* reg, int a);
-static Eterm call_error_handler(Process* p, UWord* ip, Eterm* reg);
-static Eterm call_breakpoint_handler(Process* p, UWord* fi, Eterm* reg);
-static UWord* fixed_apply(Process* p, Eterm* reg, Uint arity);
-static UWord* apply(Process* p, Eterm module, Eterm function,
+static Eterm call_error_handler(Process* p, BeamInstr* ip, Eterm* reg);
+static Eterm call_breakpoint_handler(Process* p, BeamInstr* fi, Eterm* reg);
+static BeamInstr* fixed_apply(Process* p, Eterm* reg, Uint arity);
+static BeamInstr* apply(Process* p, Eterm module, Eterm function,
 		     Eterm args, Eterm* reg);
 static int hibernate(Process* c_p, Eterm module, Eterm function,
 		     Eterm args, Eterm* reg);
-static UWord* call_fun(Process* p, int arity, Eterm* reg, Eterm args);
-static UWord* apply_fun(Process* p, Eterm fun, Eterm args, Eterm* reg);
+static BeamInstr* call_fun(Process* p, int arity, Eterm* reg, Eterm args);
+static BeamInstr* apply_fun(Process* p, Eterm fun, Eterm args, Eterm* reg);
 static Eterm new_fun(Process* p, Eterm* reg, ErlFunEntry* fe, int num_free);
 
 #if defined(_OSE_) || defined(VXWORKS)
@@ -1088,7 +1088,7 @@ void process_main(void)
     /*
      * Pointer to next threaded instruction.
      */
-    register UWord *I REG_I = NULL;
+    register BeamInstr *I REG_I = NULL;
 
     /* Number of reductions left.  This function
      * returns to the scheduler when FCALLS reaches zero.
@@ -1194,7 +1194,7 @@ void process_main(void)
     {
 	int reds;
 	Eterm* argp;
-	UWord *next;
+	BeamInstr *next;
 	int i;
 
 	argp = c_p->arg_reg;
@@ -1221,7 +1221,7 @@ void process_main(void)
 	    FCALLS = REDS_IN(c_p) = reds;
 	}
 
-	next = (UWord *) *I;
+	next = (BeamInstr *) *I;
 	r(0) = c_p->arg_reg[0];
 #ifdef HARDDEBUG
 	if (c_p->arity > 0) {
@@ -1313,7 +1313,7 @@ void process_main(void)
  }
  /* FALL THROUGH */
  OpCase(i_call_only_f): {
-     SET_I((UWord *) Arg(0));
+     SET_I((BeamInstr *) Arg(0));
      Dispatch();
  }
 
@@ -1324,7 +1324,7 @@ void process_main(void)
  OpCase(i_call_last_fP): {
      RESTORE_CP(E);
      E = ADD_BYTE_OFFSET(E, Arg(1));
-     SET_I((UWord *) Arg(0));
+     SET_I((BeamInstr *) Arg(0));
      Dispatch();
  }
 
@@ -1335,7 +1335,7 @@ void process_main(void)
  /* FALL THROUGH */
  OpCase(i_call_f): {
      SET_CP(c_p, I+2);
-     SET_I((UWord *) Arg(0));
+     SET_I((BeamInstr *) Arg(0));
      Dispatch();
  }
 
@@ -1371,7 +1371,7 @@ void process_main(void)
     Dispatchx();
 
  OpCase(init_y): {
-     UWord *next;
+     BeamInstr *next;
 
      PreFetch(1, next);
      make_blank(yb(Arg(0)));
@@ -1379,7 +1379,7 @@ void process_main(void)
  }
 
  OpCase(i_trim_I): {
-     UWord *next;
+     BeamInstr *next;
      Uint words;
      Uint cp;
 
@@ -1405,7 +1405,7 @@ void process_main(void)
  }
 
  OpCase(test_heap_1_put_list_Iy): {
-     UWord *next;
+     BeamInstr *next;
 
      PreFetch(2, next);
      TestHeap(Arg(0), 1);
@@ -1436,7 +1436,7 @@ void process_main(void)
      */
 
  OpCase(send): {
-     UWord *next;
+     BeamInstr *next;
      Eterm result;
 
      PRE_BIF_SWAPOUT(c_p);
@@ -1451,7 +1451,7 @@ void process_main(void)
 	 NextPF(0, next);
      } else if (c_p->freason == TRAP) {
 	 SET_CP(c_p, I+1);
-	 SET_I(*((UWord **) (UWord) ((c_p)->def_arg_reg + 3)));
+	 SET_I(*((BeamInstr **) (BeamInstr) ((c_p)->def_arg_reg + 3)));
 	 SWAPIN;
 	 r(0) = c_p->def_arg_reg[0];
 	 x(1) = c_p->def_arg_reg[1];
@@ -1577,7 +1577,7 @@ void process_main(void)
      */
  OpCase(i_loop_rec_fr):
  {
-     UWord *next;
+     BeamInstr *next;
      ErlMessage* msgp;
 
  loop_rec__:
@@ -1601,7 +1601,7 @@ void process_main(void)
 	     erts_smp_proc_unlock(c_p, ERTS_PROC_LOCKS_MSG_RECEIVE);
 	 else {
 #endif
-	     SET_I((UWord *) Arg(0));
+	     SET_I((BeamInstr *) Arg(0));
 	     Goto(*I);		/* Jump to a wait or wait_timeout instruction */
 #ifdef ERTS_SMP
 	 }
@@ -1637,7 +1637,7 @@ void process_main(void)
   * Remove a (matched) message from the message queue.
   */
  OpCase(remove_message): {
-     UWord *next;
+     BeamInstr *next;
      ErlMessage* msgp;
 
      PROCESS_MAIN_CHK_LOCKS(c_p);
@@ -1682,7 +1682,7 @@ void process_main(void)
      * message didn't match), then jump to the loop_rec instruction.
      */
  OpCase(loop_rec_end_f): {
-     SET_I((UWord *) Arg(0));
+     SET_I((BeamInstr *) Arg(0));
      SAVE_MESSAGE(c_p);
      goto loop_rec__;
  }
@@ -1731,13 +1731,13 @@ void process_main(void)
 	      * Note that for the halfword emulator, the two first elements
 	      * of the array are used.
 	      */
-	     *((UWord **) (UWord) c_p->def_arg_reg) = I+3;
+	     *((BeamInstr **) (UWord) c_p->def_arg_reg) = I+3;
 	     set_timer(c_p, unsigned_val(timeout_value));
 	 } else if (timeout_value == am_infinity) {
 	     c_p->flags |= F_TIMO;
 #if !defined(ARCH_64) || HALFWORD_HEAP
 	 } else if (term_to_Uint(timeout_value, &time_val)) {
-	     *((UWord **) (UWord) c_p->def_arg_reg) = I+3;
+	     *((BeamInstr **) (UWord) c_p->def_arg_reg) = I+3;
 	     set_timer(c_p, time_val);
 #endif
 	 } else {		/* Wrong time */
@@ -1766,7 +1766,7 @@ void process_main(void)
 
 	 wait2: {
 	     ASSERT(!ERTS_PROC_IS_EXITING(c_p));
-	     c_p->i = (UWord *) Arg(0); /* L1 */
+	     c_p->i = (BeamInstr *) Arg(0); /* L1 */
 	     SWAPOUT;
 	     c_p->arity = 0;
 	     c_p->status = P_WAITING;
@@ -1794,7 +1794,7 @@ void process_main(void)
       * we must test the F_INSLPQUEUE flag as well as the F_TIMO flag.
       */
      if ((c_p->flags & (F_INSLPQUEUE | F_TIMO)) == 0) {
-	 *((UWord **) (UWord) c_p->def_arg_reg) = I+3;
+	 *((BeamInstr **) (UWord) c_p->def_arg_reg) = I+3;
 	 set_timer(c_p, Arg(1));
      }
      goto wait2;
@@ -1809,7 +1809,7 @@ void process_main(void)
  }
 
  OpCase(timeout): {
-     UWord *next;
+     BeamInstr *next;
 
      PreFetch(0, next);
      if (IS_TRACED_FL(c_p, F_TRACE_RECEIVE)) {
@@ -1829,8 +1829,8 @@ void process_main(void)
  do_binary_search:
  {
      struct Pairs {
-	 UWord val;
-	 UWord* addr;
+	 BeamInstr val;
+	 BeamInstr* addr;
      };
      struct Pairs* low;
      struct Pairs* high;
@@ -1870,7 +1870,7 @@ void process_main(void)
 	     Goto(*I);
 	 }
      }
-     SET_I((UWord *) Arg(1));
+     SET_I((BeamInstr *) Arg(1));
      Goto(*I);
  }
 
@@ -1882,11 +1882,11 @@ void process_main(void)
      if (is_small(index)) {
 	 index = signed_val(index);
 	 if (index < Arg(2)) {
-	     SET_I((UWord *) (&Arg(3))[index]);
+	     SET_I((BeamInstr *) (&Arg(3))[index]);
 	     Goto(*I);
 	 }
      }
-     SET_I((UWord *) Arg(1));
+     SET_I((BeamInstr *) Arg(1));
      Goto(*I);
  }
 
@@ -1898,11 +1898,11 @@ void process_main(void)
      if (is_small(index)) {
 	 index = (Uint) (signed_val(index) - Arg(3));
 	 if (index < Arg(2)) {
-	     SET_I((UWord *) (&Arg(4))[index]);
+	     SET_I((BeamInstr *) (&Arg(4))[index]);
 	     Goto(*I);
 	 }
      }
-     SET_I((UWord *) Arg(1));
+     SET_I((BeamInstr *) Arg(1));
      Goto(*I);
  }
 
@@ -1939,7 +1939,7 @@ void process_main(void)
 	if (is_value(result)) {
 	    StoreBifResult(3, result);
 	}
-	SET_I((UWord *) Arg(0));
+	SET_I((BeamInstr *) Arg(0));
 	Goto(*I);
     }
 
@@ -1979,7 +1979,7 @@ void process_main(void)
 	GcBifFunction bf;
 	Eterm arg;
 	Eterm result;
-	Uint live = Arg(3);
+	Uint live = (Uint) Arg(3);
 
 	GetArg1(2, arg);
 	reg[0] = r(0);
@@ -2000,7 +2000,7 @@ void process_main(void)
 	    StoreBifResult(4, result);
 	}
 	if (Arg(0) != 0) {
-	    SET_I((UWord *) Arg(0));
+	    SET_I((BeamInstr *) Arg(0));
 	    Goto(*I);
 	}
 	reg[0] = arg;
@@ -2028,7 +2028,7 @@ void process_main(void)
 	if (is_value(result)) {
 	    StoreBifResult(2, result);
 	}
-	SET_I((UWord *) Arg(0));
+	SET_I((BeamInstr *) Arg(0));
 	Goto(*I);
     }
 
@@ -2064,7 +2064,7 @@ void process_main(void)
      */
  OpCase(call_bif0_e):
     {
-	Eterm (*bf)(Process*, UWord*) = GET_BIF_ADDRESS(Arg(0));
+	Eterm (*bf)(Process*, BeamInstr*) = GET_BIF_ADDRESS(Arg(0));
 
 	PRE_BIF_SWAPOUT(c_p);
 	c_p->fcalls = FCALLS - 1;
@@ -2097,9 +2097,9 @@ void process_main(void)
 
  OpCase(call_bif1_e):
     {
-	Eterm (*bf)(Process*, Eterm, UWord*) = GET_BIF_ADDRESS(Arg(0));
+	Eterm (*bf)(Process*, Eterm, BeamInstr*) = GET_BIF_ADDRESS(Arg(0));
 	Eterm result;
-	UWord *next;
+	BeamInstr *next;
 
 	c_p->fcalls = FCALLS - 1;
 	if (FCALLS <= 0) {
@@ -2132,9 +2132,9 @@ void process_main(void)
 
  OpCase(call_bif2_e):
     {
-	Eterm (*bf)(Process*, Eterm, Eterm, UWord*) = GET_BIF_ADDRESS(Arg(0));
+	Eterm (*bf)(Process*, Eterm, Eterm, BeamInstr*) = GET_BIF_ADDRESS(Arg(0));
 	Eterm result;
-	UWord *next;
+	BeamInstr *next;
 
 	PRE_BIF_SWAPOUT(c_p);
 	c_p->fcalls = FCALLS - 1;
@@ -2169,9 +2169,9 @@ void process_main(void)
 
  OpCase(call_bif3_e):
     {
-	Eterm (*bf)(Process*, Eterm, Eterm, Eterm, UWord*) = GET_BIF_ADDRESS(Arg(0));
+	Eterm (*bf)(Process*, Eterm, Eterm, Eterm, BeamInstr*) = GET_BIF_ADDRESS(Arg(0));
 	Eterm result;
-	UWord *next;
+	BeamInstr *next;
 
 	PRE_BIF_SWAPOUT(c_p);
 	c_p->fcalls = FCALLS - 1;
@@ -2192,7 +2192,7 @@ void process_main(void)
 	} else if (c_p->freason == TRAP) {
 	call_bif_trap3:
 	    SET_CP(c_p, I+2);
-	    SET_I(*((UWord **) (UWord) ((c_p)->def_arg_reg + 3)));
+	    SET_I(*((BeamInstr **) (UWord) ((c_p)->def_arg_reg + 3)));
 	    SWAPIN;
 	    r(0) = c_p->def_arg_reg[0];
 	    x(1) = c_p->def_arg_reg[1];
@@ -2300,7 +2300,7 @@ void process_main(void)
  lb_Cl_error: {
      if (Arg(0) != 0) {
 	 OpCase(jump_f): {
-	     SET_I((UWord *) Arg(0));
+	     SET_I((BeamInstr *) Arg(0));
 	     Goto(*I);
 	 }
      }
@@ -2492,7 +2492,7 @@ void process_main(void)
     goto lb_Cl_error;
 
  OpCase(i_apply): {
-     UWord *next;
+     BeamInstr *next;
      SWAPOUT;
      next = apply(c_p, r(0), x(1), x(2), reg);
      SWAPIN;
@@ -2507,13 +2507,13 @@ void process_main(void)
  }
 
  OpCase(i_apply_last_P): {
-     UWord *next;
+     BeamInstr *next;
      SWAPOUT;
      next = apply(c_p, r(0), x(1), x(2), reg);
      SWAPIN;
      if (next != NULL) {
 	 r(0) = reg[0];
-	 SET_CP(c_p, (UWord *) EXPAND_POINTER(E[0]));
+	 SET_CP(c_p, (BeamInstr *) EXPAND_POINTER(E[0]));
 	 E = ADD_BYTE_OFFSET(E, Arg(0));
 	 SET_I(next);
 	 Dispatch();
@@ -2523,7 +2523,7 @@ void process_main(void)
  }
 
  OpCase(i_apply_only): {
-     UWord *next;
+     BeamInstr *next;
      SWAPOUT;
      next = apply(c_p, r(0), x(1), x(2), reg);
      SWAPIN;
@@ -2537,7 +2537,7 @@ void process_main(void)
  }
 
  OpCase(apply_I): {
-     UWord *next;
+     BeamInstr *next;
 
      reg[0] = r(0);
      SWAPOUT;
@@ -2554,7 +2554,7 @@ void process_main(void)
  }
 
  OpCase(apply_last_IP): {
-     UWord *next;
+     BeamInstr *next;
 
      reg[0] = r(0);
      SWAPOUT;
@@ -2562,7 +2562,7 @@ void process_main(void)
      SWAPIN;
      if (next != NULL) {
 	 r(0) = reg[0];
-	 SET_CP(c_p, (UWord *) EXPAND_POINTER(E[0]));
+	 SET_CP(c_p, (BeamInstr *) EXPAND_POINTER(E[0]));
 	 E = ADD_BYTE_OFFSET(E, Arg(1));
 	 SET_I(next);
 	 Dispatch();
@@ -2572,7 +2572,7 @@ void process_main(void)
  }
 
  OpCase(i_apply_fun): {
-     UWord *next;
+     BeamInstr *next;
 
      SWAPOUT;
      next = apply_fun(c_p, r(0), x(1), reg);
@@ -2587,14 +2587,14 @@ void process_main(void)
  }
 
  OpCase(i_apply_fun_last_P): {
-     UWord *next;
+     BeamInstr *next;
 
      SWAPOUT;
      next = apply_fun(c_p, r(0), x(1), reg);
      SWAPIN;
      if (next != NULL) {
 	 r(0) = reg[0];
-	 SET_CP(c_p, (UWord *) EXPAND_POINTER(E[0]));
+	 SET_CP(c_p, (BeamInstr *) EXPAND_POINTER(E[0]));
 	 E = ADD_BYTE_OFFSET(E, Arg(0));
 	 SET_I(next);
 	 Dispatchfun();
@@ -2603,7 +2603,7 @@ void process_main(void)
  }
 
  OpCase(i_apply_fun_only): {
-     UWord *next;
+     BeamInstr *next;
 
      SWAPOUT;
      next = apply_fun(c_p, r(0), x(1), reg);
@@ -2617,7 +2617,7 @@ void process_main(void)
  }
 
  OpCase(i_call_fun_I): {
-     UWord *next;
+     BeamInstr *next;
 
      SWAPOUT;
      reg[0] = r(0);
@@ -2633,7 +2633,7 @@ void process_main(void)
  }
 
  OpCase(i_call_fun_last_IP): {
-     UWord *next;
+     BeamInstr *next;
 
      SWAPOUT;
      reg[0] = r(0);
@@ -2641,7 +2641,7 @@ void process_main(void)
      SWAPIN;
      if (next != NULL) {
 	r(0) = reg[0];
-	SET_CP(c_p, (UWord *) EXPAND_POINTER(E[0]));
+	SET_CP(c_p, (BeamInstr *) EXPAND_POINTER(E[0]));
 	E = ADD_BYTE_OFFSET(E, Arg(1));
 	SET_I(next);
 	Dispatchfun();
@@ -2746,7 +2746,7 @@ void process_main(void)
 	 tmp_arg1 = *tuple_val(tmp_arg1);
 	 goto do_binary_search;
      }
-     SET_I((UWord *) Arg(1));
+     SET_I((BeamInstr *) Arg(1));
      Goto(*I);
  }     
 
@@ -2778,9 +2778,9 @@ void process_main(void)
 	    }
 	    while (bigp[0] == given_arity) {
 		if (memcmp(bigp+1, given+1, sizeof(Eterm)*given_size) == 0) {
-		    UWord *tmp =
-			((UWord *) (UWord) bigp) + TermWords(given_size + 1);
-		    SET_I((UWord *) *tmp);
+		    BeamInstr *tmp =
+			((BeamInstr *) (UWord) bigp) + TermWords(given_size + 1);
+		    SET_I((BeamInstr *) *tmp);
 		    Goto(*I);
 		}
 		bigp += thing_arityval(arity) + 2;
@@ -2791,7 +2791,7 @@ void process_main(void)
 	 * Failed.
 	 */
 
-	SET_I((UWord *) Arg(1));
+	SET_I((BeamInstr *) Arg(1));
 	Goto(*I);
     }
 
@@ -2802,7 +2802,7 @@ void process_main(void)
      int n;
      struct ValLabel {
 	 Uint f;
-	 UWord* addr;
+	 BeamInstr* addr;
      };
      struct ValLabel* ptr;
 
@@ -2830,7 +2830,7 @@ void process_main(void)
      struct ValLabel {
 	 Uint fpart1;
 	 Uint fpart2;
-	 UWord* addr;
+	 BeamInstr* addr;
      };
      struct ValLabel* ptr;
 
@@ -2848,7 +2848,7 @@ void process_main(void)
 	 }
 	 ptr++;
      }
-     SET_I((UWord *) Arg(1));
+     SET_I((BeamInstr *) Arg(1));
      Goto(*I);
  }
 #endif
@@ -2856,7 +2856,7 @@ void process_main(void)
  OpCase(set_tuple_element_sdP): {
      Eterm element;
      Eterm tuple;
-     UWord *next;
+     BeamInstr *next;
      Eterm* p;
      
      PreFetch(3, next);
@@ -3051,7 +3051,7 @@ void process_main(void)
 	switch (tmp_arg2) {
 	case 3:
 	    {
-		Eterm (*bf)(Process*, Eterm, Eterm, Eterm, UWord*) = vbf;
+		Eterm (*bf)(Process*, Eterm, Eterm, Eterm, BeamInstr*) = vbf;
 		ASSERT(!ERTS_PROC_IS_EXITING(c_p));
 		tmp_arg1 = (*bf)(c_p, r(0), x(1), x(2), I);
 		ASSERT(!ERTS_PROC_IS_EXITING(c_p) || is_non_value(tmp_arg1));
@@ -3060,7 +3060,7 @@ void process_main(void)
 	    break;
 	case 2:
 	    {
-		Eterm (*bf)(Process*, Eterm, Eterm, UWord*) = vbf;
+		Eterm (*bf)(Process*, Eterm, Eterm, BeamInstr*) = vbf;
 		ASSERT(!ERTS_PROC_IS_EXITING(c_p));
 		tmp_arg1 = (*bf)(c_p, r(0), x(1), I);
 		ASSERT(!ERTS_PROC_IS_EXITING(c_p) || is_non_value(tmp_arg1));
@@ -3069,7 +3069,7 @@ void process_main(void)
 	    break;
 	case 1:
 	    {
-		Eterm (*bf)(Process*, Eterm, UWord*) = vbf;
+		Eterm (*bf)(Process*, Eterm, BeamInstr*) = vbf;
 		ASSERT(!ERTS_PROC_IS_EXITING(c_p));
 		tmp_arg1 = (*bf)(c_p, r(0), I);
 		ASSERT(!ERTS_PROC_IS_EXITING(c_p) || is_non_value(tmp_arg1));
@@ -3078,7 +3078,7 @@ void process_main(void)
 	    break;
 	case 0:
 	    {
-		Eterm (*bf)(Process*, UWord*) = vbf;
+		Eterm (*bf)(Process*, BeamInstr*) = vbf;
 		ASSERT(!ERTS_PROC_IS_EXITING(c_p));
 		tmp_arg1 = (*bf)(c_p, I);
 		ASSERT(!ERTS_PROC_IS_EXITING(c_p) || is_non_value(tmp_arg1));
@@ -3102,7 +3102,7 @@ apply_bif_or_nif_epilogue:
 	    SET_I(c_p->cp);
 	    Goto(*I);
 	} else if (c_p->freason == TRAP) {
-	    SET_I(*((UWord **) (UWord) ((c_p)->def_arg_reg + 3)));
+	    SET_I(*((BeamInstr **) (UWord) ((c_p)->def_arg_reg + 3)));
 	    r(0) = c_p->def_arg_reg[0];
 	    x(1) = c_p->def_arg_reg[1];
 	    x(2) = c_p->def_arg_reg[2];
@@ -3560,7 +3560,7 @@ apply_bif_or_nif_epilogue:
 
  OpCase(bs_put_string_II):
     {
-	UWord *next;
+	BeamInstr *next;
 	PreFetch(2, next);
 	erts_new_bs_put_string(ERL_BITS_ARGS_2((byte *) Arg(1), Arg(0)));
 	NextPF(2, next);
@@ -3731,7 +3731,7 @@ apply_bif_or_nif_epilogue:
 
  {
      Eterm header;
-     UWord *next;
+     BeamInstr *next;
      Uint slots;
 
      OpCase(i_bs_start_match2_rfIId): {
@@ -3797,7 +3797,7 @@ apply_bif_or_nif_epilogue:
  }
 
  OpCase(bs_test_zero_tail2_fr): {
-     UWord *next;
+     BeamInstr *next;
      ErlBinMatchBuffer *_mb;
      
      PreFetch(1, next);
@@ -3809,7 +3809,7 @@ apply_bif_or_nif_epilogue:
  }
 
  OpCase(bs_test_zero_tail2_fx): {
-     UWord *next;
+     BeamInstr *next;
      ErlBinMatchBuffer *_mb;
      
      PreFetch(2, next);
@@ -3821,7 +3821,7 @@ apply_bif_or_nif_epilogue:
  }
 
  OpCase(bs_test_tail_imm2_frI): {
-     UWord *next;
+     BeamInstr *next;
      ErlBinMatchBuffer *_mb;
      PreFetch(2, next);
      _mb = ms_matchbuffer(r(0));
@@ -3831,7 +3831,7 @@ apply_bif_or_nif_epilogue:
      NextPF(2, next);
  }
  OpCase(bs_test_tail_imm2_fxI): {
-     UWord *next;
+     BeamInstr *next;
      ErlBinMatchBuffer *_mb;
      PreFetch(3, next);
      _mb = ms_matchbuffer(xb(Arg(1)));
@@ -3842,7 +3842,7 @@ apply_bif_or_nif_epilogue:
  }
 
  OpCase(bs_test_unit_frI): {
-     UWord *next;
+     BeamInstr *next;
      ErlBinMatchBuffer *_mb;
      PreFetch(2, next);
      _mb = ms_matchbuffer(r(0));
@@ -3852,7 +3852,7 @@ apply_bif_or_nif_epilogue:
      NextPF(2, next);
  }
  OpCase(bs_test_unit_fxI): {
-     UWord *next;
+     BeamInstr *next;
      ErlBinMatchBuffer *_mb;
      PreFetch(3, next);
      _mb = ms_matchbuffer(xb(Arg(1)));
@@ -3863,7 +3863,7 @@ apply_bif_or_nif_epilogue:
  }
 
  OpCase(bs_test_unit8_fr): {
-     UWord *next;
+     BeamInstr *next;
      ErlBinMatchBuffer *_mb;
      PreFetch(1, next);
      _mb = ms_matchbuffer(r(0));
@@ -3873,7 +3873,7 @@ apply_bif_or_nif_epilogue:
      NextPF(1, next);
  }
  OpCase(bs_test_unit8_fx): {
-     UWord *next;
+     BeamInstr *next;
      ErlBinMatchBuffer *_mb;
      PreFetch(2, next);
      _mb = ms_matchbuffer(xb(Arg(1)));
@@ -4198,7 +4198,7 @@ apply_bif_or_nif_epilogue:
 
  do_bs_match_string:
      {
-	 UWord *next;
+	 BeamInstr *next;
 	 byte* bytes;
 	 Uint bits;
 	 ErlBinMatchBuffer* mb;
@@ -4225,7 +4225,7 @@ apply_bif_or_nif_epilogue:
  }
 
  OpCase(i_bs_save2_rI): {
-     UWord *next;
+     BeamInstr *next;
      ErlBinMatchState *_ms;
      PreFetch(1, next);
      _ms = (ErlBinMatchState*) boxed_val((Eterm) r(0));
@@ -4233,7 +4233,7 @@ apply_bif_or_nif_epilogue:
      NextPF(1, next);
  }
  OpCase(i_bs_save2_xI): {
-     UWord *next;
+     BeamInstr *next;
      ErlBinMatchState *_ms;
      PreFetch(2, next);
      _ms = (ErlBinMatchState*) boxed_val((Eterm) xb(Arg(0)));
@@ -4242,7 +4242,7 @@ apply_bif_or_nif_epilogue:
  }
 
  OpCase(i_bs_restore2_rI): {
-     UWord *next;
+     BeamInstr *next;
      ErlBinMatchState *_ms;
      PreFetch(1, next);
      _ms = (ErlBinMatchState*) boxed_val((Eterm) r(0));
@@ -4250,7 +4250,7 @@ apply_bif_or_nif_epilogue:
      NextPF(1, next);
  }
  OpCase(i_bs_restore2_xI): {
-     UWord *next;
+     BeamInstr *next;
      ErlBinMatchState *_ms;
      PreFetch(2, next);
      _ms = (ErlBinMatchState*) boxed_val((Eterm) xb(Arg(0)));
@@ -4267,7 +4267,7 @@ apply_bif_or_nif_epilogue:
   * deallocate not followed by a return, and that should work.
   */
  OpCase(deallocate_I): {
-     UWord *next;
+     BeamInstr *next;
 
      PreFetch(1, next);
      D(Arg(0));
@@ -4317,7 +4317,7 @@ apply_bif_or_nif_epilogue:
 	     }
 	     E -= 3;
 	     ASSERT(c_p->htop <= E && E <= c_p->hend);
-	     ASSERT(is_CP((UWord)(ep->code)));
+	     ASSERT(is_CP((BeamInstr)(ep->code)));
 	     ASSERT(is_internal_pid(c_p->tracer_proc) || 
 		    is_internal_port(c_p->tracer_proc));
 	     E[2] = make_cp(c_p->cp); /* XXX:PaN - code in lower range on halfword */
@@ -4330,12 +4330,12 @@ apply_bif_or_nif_epilogue:
 	     erts_smp_proc_unlock(c_p, ERTS_PROC_LOCKS_ALL_MINOR);
 	 }
      }
-     SET_I((UWord *)Arg(0));
+     SET_I((BeamInstr *)Arg(0));
      Dispatch();
  }
 
  OpCase(return_trace): {
-     UWord* code = (UWord *) (UWord) E[0];
+     BeamInstr* code = (BeamInstr *) (UWord) E[0];
      
      SWAPOUT;		/* Needed for shared heap */
      ERTS_SMP_UNREQ_PROC_MAIN_LOCK(c_p);
@@ -4343,24 +4343,24 @@ apply_bif_or_nif_epilogue:
      ERTS_SMP_REQ_PROC_MAIN_LOCK(c_p);
      SWAPIN;
      c_p->cp = NULL;
-     SET_I((UWord *) cp_val(E[2]));
+     SET_I((BeamInstr *) cp_val(E[2]));
      E += 3;
      Goto(*I);
  }
 
  OpCase(i_count_breakpoint): {
-     UWord real_I;
+     BeamInstr real_I;
      
-     ErtsCountBreak((UWord *) I, &real_I);
+     ErtsCountBreak((BeamInstr *) I, &real_I);
      ASSERT(VALID_INSTR(real_I));
      Goto(real_I);
  }
 
  OpCase(i_trace_breakpoint):
      if (! IS_TRACED_FL(c_p, F_TRACE_CALLS)) {
-	 UWord real_I;
+	 BeamInstr real_I;
 	 
-	 ErtsBreakSkip((UWord *) I, &real_I);
+	 ErtsBreakSkip((BeamInstr *) I, &real_I);
 	 Goto(real_I);
      }
  /* Fall through to next case */
@@ -4374,10 +4374,10 @@ apply_bif_or_nif_epilogue:
      SWAPOUT;
      reg[0] = r(0);
 
-     if (*(c_p->cp) == (UWord) OpCode(return_trace)) {
+     if (*(c_p->cp) == (BeamInstr) OpCode(return_trace)) {
 	 cpp = (Uint*)&E[2];
      } else if (*(c_p->cp)
-		== (UWord) OpCode(i_return_to_trace)) {
+		== (BeamInstr) OpCode(i_return_to_trace)) {
 	 return_to_trace = !0;
 	 cpp = (Uint*)&E[0];
      } else {
@@ -4388,18 +4388,18 @@ apply_bif_or_nif_epilogue:
 	  * return_trace and/or i_return_to_trace stackframes
 	  * on the stack, they are not intermixed with y registers
 	  */
-	 UWord *cp_save = c_p->cp;
+	 BeamInstr *cp_save = c_p->cp;
 	 for (;;) {
 	     ASSERT(is_CP(*cpp));
-	     if (*cp_val(*cpp) == (UWord) OpCode(return_trace)) {
+	     if (*cp_val(*cpp) == (BeamInstr) OpCode(return_trace)) {
 		 cpp += 3;
-	     } else if (*cp_val(*cpp) == (UWord) OpCode(i_return_to_trace)) {
+	     } else if (*cp_val(*cpp) == (BeamInstr) OpCode(i_return_to_trace)) {
 		 return_to_trace = !0;
 		 cpp += 1;
 	     } else
 		 break;
 	 }
-	 c_p->cp = (UWord *) cp_val(*cpp);
+	 c_p->cp = (BeamInstr *) cp_val(*cpp);
 	 ASSERT(is_CP(*cpp));
 	 ERTS_SMP_UNREQ_PROC_MAIN_LOCK(c_p);
 	 real_I = erts_trace_break(c_p, I, reg, &flags, &tracer_pid);
@@ -4436,7 +4436,7 @@ apply_bif_or_nif_epilogue:
 	 E -= 1;
 	 ASSERT(c_p->htop <= E && E <= c_p->hend);
 	 E[0] = make_cp(c_p->cp);
-	 c_p->cp = (UWord *) beam_return_to_trace;
+	 c_p->cp = (BeamInstr *) beam_return_to_trace;
      }
      if (flags & MATCH_SET_RX_TRACE) {
 	 E -= 3;
@@ -4464,10 +4464,10 @@ apply_bif_or_nif_epilogue:
 	 Uint *cpp = (Uint*) E;
 	 for(;;) {
 	     ASSERT(is_CP(*cpp));
-	     if (*cp_val(*cpp) == (UWord) OpCode(return_trace)) {
+	     if (*cp_val(*cpp) == (BeamInstr) OpCode(return_trace)) {
 		 do ++cpp; while(is_not_CP(*cpp));
 		 cpp += 2;
-	     } else if (*cp_val(*cpp) == (UWord) OpCode(i_return_to_trace)) {
+	     } else if (*cp_val(*cpp) == (BeamInstr) OpCode(i_return_to_trace)) {
 		 do ++cpp; while(is_not_CP(*cpp));
 	     } else break;
 	 }
@@ -4478,7 +4478,7 @@ apply_bif_or_nif_epilogue:
 	 SWAPIN;
      }
      c_p->cp = NULL;
-     SET_I((UWord *) cp_val(E[0]));
+     SET_I((BeamInstr *) cp_val(E[0]));
      E += 1;
      Goto(*I);
  }
@@ -4489,7 +4489,7 @@ apply_bif_or_nif_epilogue:
 
  OpCase(i_global_cons):
  {
-     UWord *next;
+     BeamInstr *next;
 #ifdef HYBRID
      Eterm *hp;
 
@@ -4511,7 +4511,7 @@ apply_bif_or_nif_epilogue:
 
  OpCase(i_global_tuple):
  {
-     UWord *next;
+     BeamInstr *next;
      int len;
 #ifdef HYBRID
      Eterm list;
@@ -4546,7 +4546,7 @@ apply_bif_or_nif_epilogue:
 
  OpCase(i_global_copy):
  {
-     UWord *next;
+     BeamInstr *next;
      PreFetch(0,next);
 #ifdef HYBRID
      if (!IS_CONST(r(0)))
@@ -4575,7 +4575,7 @@ apply_bif_or_nif_epilogue:
 
  OpCase(fmove_ql): {
      Eterm fr = Arg(1);
-     UWord *next;
+     BeamInstr *next;
 
      PreFetch(2, next);
      GET_DOUBLE(Arg(0), *(FloatDef*)ADD_BYTE_OFFSET(freg, fr));
@@ -4585,7 +4585,7 @@ apply_bif_or_nif_epilogue:
  OpCase(fmove_dl): {
      Eterm targ1;
      Eterm fr = Arg(1);
-     UWord *next;
+     BeamInstr *next;
 
      PreFetch(2, next);
      GetR(0, targ1);
@@ -4606,7 +4606,7 @@ apply_bif_or_nif_epilogue:
  OpCase(fconv_dl): {
      Eterm targ1;
      Eterm fr = Arg(1);
-     UWord *next;
+     BeamInstr *next;
 
      GetR(0, targ1);
      PreFetch(2, next);
@@ -4635,7 +4635,7 @@ apply_bif_or_nif_epilogue:
 	 erl_exit(1, "fclearerror/i_fcheckerror without fpe signals (beam_emu)");
 #else
      OpCase(fclearerror): {
-	 UWord *next;
+	 BeamInstr *next;
 
 	 PreFetch(0, next);
 	 ERTS_FP_CHECK_INIT(c_p);
@@ -4643,7 +4643,7 @@ apply_bif_or_nif_epilogue:
      }
 
      OpCase(i_fcheckerror): {
-	 UWord *next;
+	 BeamInstr *next;
 
 	 PreFetch(0, next);
 	 ERTS_FP_ERROR(c_p, freg[0].fd, goto fbadarith);
@@ -4657,7 +4657,7 @@ apply_bif_or_nif_epilogue:
 
 
  OpCase(i_fadd_lll): {
-     UWord *next;
+     BeamInstr *next;
 
      PreFetch(3, next);
      ERTS_FP_CHECK_INIT(c_p);
@@ -4666,7 +4666,7 @@ apply_bif_or_nif_epilogue:
      NextPF(3, next);
  }
  OpCase(i_fsub_lll): {
-     UWord *next;
+     BeamInstr *next;
 
      PreFetch(3, next);
      ERTS_FP_CHECK_INIT(c_p);
@@ -4675,7 +4675,7 @@ apply_bif_or_nif_epilogue:
      NextPF(3, next);
  }
  OpCase(i_fmul_lll): {
-     UWord *next;
+     BeamInstr *next;
 
      PreFetch(3, next);
      ERTS_FP_CHECK_INIT(c_p);
@@ -4684,7 +4684,7 @@ apply_bif_or_nif_epilogue:
      NextPF(3, next);
  }
  OpCase(i_fdiv_lll): {
-     UWord *next;
+     BeamInstr *next;
 
      PreFetch(3, next);
      ERTS_FP_CHECK_INIT(c_p);
@@ -4693,7 +4693,7 @@ apply_bif_or_nif_epilogue:
      NextPF(3, next);
  }
  OpCase(i_fnegate_ll): {
-     UWord *next;
+     BeamInstr *next;
 
      PreFetch(2, next);
      ERTS_FP_CHECK_INIT(c_p);
@@ -4772,7 +4772,7 @@ apply_bif_or_nif_epilogue:
 	 /* This can be used to call any function value, but currently it's
 	    only used to call closures referring to unloaded modules. */
 	 {
-	     UWord *next;
+	     BeamInstr *next;
 
 	     next = call_fun(c_p, c_p->arity - 1, reg, THE_NON_VALUE);
 	     SWAPIN;
@@ -4921,8 +4921,8 @@ apply_bif_or_nif_epilogue:
 			      bif_table[i].name,
 			      bif_table[i].arity);
 	 bif_export[i] = ep;
-	 ep->code[3] = (UWord) OpCode(apply_bif);
-	 ep->code[4] = (UWord) bif_table[i].f;
+	 ep->code[3] = (BeamInstr) OpCode(apply_bif);
+	 ep->code[4] = (BeamInstr) bif_table[i].f;
      }
 
      return;
@@ -5025,8 +5025,8 @@ Eterm error_atom[NUMBER_EXIT_CODES] = {
  * at the point of the original exception.
  */
 
-static UWord*
-handle_error(Process* c_p, UWord* pc, Eterm* reg, BifFunction bf)
+static BeamInstr*
+handle_error(Process* c_p, BeamInstr* pc, Eterm* reg, BifFunction bf)
 {
     Eterm* hp;
     Eterm Value = c_p->fvalue;
@@ -5080,7 +5080,7 @@ handle_error(Process* c_p, UWord* pc, Eterm* reg, BifFunction bf)
     /* Find a handler or die */
     if ((c_p->catches > 0 || IS_TRACED_FL(c_p, F_EXCEPTION_TRACE))
 	&& !(c_p->freason & EXF_PANIC)) {
-	UWord *new_pc;
+	BeamInstr *new_pc;
         /* The Beam handler code (catch_end or try_end) checks reg[0]
 	   for THE_NON_VALUE to see if the previous code finished
 	   abnormally. If so, reg[1], reg[2] and reg[3] should hold the
@@ -5106,13 +5106,13 @@ handle_error(Process* c_p, UWord* pc, Eterm* reg, BifFunction bf)
 /*
  * Find the nearest catch handler
  */
-static UWord*
+static BeamInstr*
 next_catch(Process* c_p, Eterm *reg) {
     int active_catches = c_p->catches > 0;
     int have_return_to_trace = 0;
     Eterm *ptr, *prev, *return_to_trace_ptr = NULL;
-    UWord i_return_trace = beam_return_trace[0];
-    UWord i_return_to_trace = beam_return_to_trace[0];
+    BeamInstr i_return_trace = beam_return_trace[0];
+    BeamInstr i_return_to_trace = beam_return_to_trace[0];
     ptr = prev = c_p->stop;
     ASSERT(is_CP(*ptr));
     ASSERT(ptr <= STACK_START(c_p));
@@ -5121,7 +5121,7 @@ next_catch(Process* c_p, Eterm *reg) {
 			     *cp_val(*ptr) != i_return_to_trace))
 	&& c_p->cp) {
 	/* Can not follow cp here - code may be unloaded */
-	UWord *cpp = c_p->cp;
+	BeamInstr *cpp = c_p->cp;
 	if (cpp == beam_exception_trace) {
 	    erts_trace_exception(c_p, cp_val(ptr[0]),
 				 reg[1], reg[2], ptr+1);
@@ -5276,7 +5276,7 @@ expand_error_value(Process* c_p, Uint freason, Eterm Value) {
  */
 
 static void
-save_stacktrace(Process* c_p, UWord* pc, Eterm* reg, BifFunction bf,
+save_stacktrace(Process* c_p, BeamInstr* pc, Eterm* reg, BifFunction bf,
 		Eterm args) {
     struct StackTrace* s;
     int sz;
@@ -5287,7 +5287,7 @@ save_stacktrace(Process* c_p, UWord* pc, Eterm* reg, BifFunction bf,
     }
 
     /* Create a container for the exception data */
-    sz = (offsetof(struct StackTrace, trace) + sizeof(UWord *)*depth
+    sz = (offsetof(struct StackTrace, trace) + sizeof(BeamInstr *)*depth
           + sizeof(Eterm) - 1) / sizeof(Eterm);
     s = (struct StackTrace *) HAlloc(c_p, 1 + sz);
     /* The following fields are inside the bignum */
@@ -5375,9 +5375,9 @@ save_stacktrace(Process* c_p, UWord* pc, Eterm* reg, BifFunction bf,
     /* Save the actual stack trace */
     if (depth > 0) {
 	Eterm *ptr;
-	UWord *prev = s->depth ? s->trace[s->depth-1] : NULL;
-	UWord i_return_trace = beam_return_trace[0];
-	UWord i_return_to_trace = beam_return_to_trace[0];
+	BeamInstr *prev = s->depth ? s->trace[s->depth-1] : NULL;
+	BeamInstr i_return_trace = beam_return_trace[0];
+	BeamInstr i_return_to_trace = beam_return_to_trace[0];
 	/*
 	 * Traverse the stack backwards and add all unique continuation
 	 * pointers to the buffer, up to the maximum stack trace size.
@@ -5390,7 +5390,7 @@ save_stacktrace(Process* c_p, UWord* pc, Eterm* reg, BifFunction bf,
 				   *cp_val(*ptr) != i_return_to_trace))
 	    && c_p->cp) {
 	    /* Can not follow cp here - code may be unloaded */
-	    UWord *cpp = c_p->cp;
+	    BeamInstr *cpp = c_p->cp;
 	    if (cpp == beam_exception_trace || cpp == beam_return_trace) {
 		/* Skip return_trace parameters */
 		ptr += 2;
@@ -5410,7 +5410,7 @@ save_stacktrace(Process* c_p, UWord* pc, Eterm* reg, BifFunction bf,
 		    /* Skip stack frame variables */
 		    do ++ptr; while (is_not_CP(*ptr));
 		} else {
-		    UWord *cp = cp_val(*ptr);
+		    BeamInstr *cp = cp_val(*ptr);
 		    if (cp != prev) {
 			/* Record non-duplicates only */
 			prev = cp;
@@ -5482,9 +5482,9 @@ build_stacktrace(Process* c_p, Eterm exc) {
     struct StackTrace* s;
     Eterm  args;
     int    depth;
-    UWord* current;
+    BeamInstr* current;
 #if HALFWORD_HEAP
-    UWord current_buff[3];
+    BeamInstr current_buff[3];
 #endif
     Eterm  Where = NIL;
     Eterm *next_p = &Where;
@@ -5517,9 +5517,9 @@ build_stacktrace(Process* c_p, Eterm exc) {
     if (current == NULL) {
 #if HALFWORD_HEAP
 	current = current_buff;
-	current[0] = (UWord) c_p->initial[0];
-	current[1] = (UWord) c_p->initial[1];
-	current[2] = (UWord) c_p->initial[2];
+	current[0] = (BeamInstr) c_p->initial[0];
+	current[1] = (BeamInstr) c_p->initial[1];
+	current[2] = (BeamInstr) c_p->initial[2];
 #else
 	current = c_p->initial;
 #endif
@@ -5558,7 +5558,7 @@ build_stacktrace(Process* c_p, Eterm exc) {
 	 * Finally, we go through the saved continuation pointers.
 	 */
 	for (i = 0; i < depth; i++) {
-	    UWord *fi = find_function_from_pc((UWord *) s->trace[i]);
+	    BeamInstr *fi = find_function_from_pc((BeamInstr *) s->trace[i]);
 	    if (fi == NULL) continue;
 	    mfa = TUPLE3(hp, fi[0], fi[1], make_small(fi[2]));
 	    hp += 4;
@@ -5575,7 +5575,7 @@ build_stacktrace(Process* c_p, Eterm exc) {
 
 
 static Eterm
-call_error_handler(Process* p, UWord* fi, Eterm* reg)
+call_error_handler(Process* p, BeamInstr* fi, Eterm* reg)
 {
     Eterm* hp;
     Export* ep;
@@ -5623,7 +5623,7 @@ call_error_handler(Process* p, UWord* fi, Eterm* reg)
 }
 
 static Eterm
-call_breakpoint_handler(Process* p, UWord* fi, Eterm* reg)
+call_breakpoint_handler(Process* p, BeamInstr* fi, Eterm* reg)
 {
     Eterm* hp;
     Export* ep;
@@ -5716,7 +5716,7 @@ apply_setup_error_handler(Process* p, Eterm module, Eterm function, Uint arity,
     return ep;
 }
 
-static UWord*
+static BeamInstr*
 apply(Process* p, Eterm module, Eterm function, Eterm args, Eterm* reg)
 {
     int arity;
@@ -5798,7 +5798,7 @@ apply(Process* p, Eterm module, Eterm function, Eterm args, Eterm* reg)
     return ep->address;
 }
 
-static UWord*
+static BeamInstr*
 fixed_apply(Process* p, Eterm* reg, Uint arity)
 {
     Export* ep;
@@ -5904,7 +5904,7 @@ hibernate(Process* c_p, Eterm module, Eterm function, Eterm args, Eterm* reg)
     c_p->stop = STACK_START(c_p);
     c_p->catches = 0;
     c_p->i = beam_apply;
-    c_p->cp = (UWord *) beam_apply+1;
+    c_p->cp = (BeamInstr *) beam_apply+1;
 
     /*
      * If there are no waiting messages, garbage collect and
@@ -5934,7 +5934,7 @@ hibernate(Process* c_p, Eterm module, Eterm function, Eterm args, Eterm* reg)
     return 1;
 }
 
-static UWord*
+static BeamInstr*
 call_fun(Process* p,		/* Current process. */
 	 int arity,		/* Number of arguments for Fun. */
 	 Eterm* reg,		/* Contents of registers. */
@@ -5954,7 +5954,7 @@ call_fun(Process* p,		/* Current process. */
     if (is_fun_header(hdr)) {
 	ErlFunThing* funp = (ErlFunThing *) fun_val(fun);
 	ErlFunEntry* fe;
-	UWord* code_ptr;
+	BeamInstr* code_ptr;
 	Eterm* var_ptr;
 	int actual_arity;
 	unsigned num_free;
@@ -6117,7 +6117,7 @@ call_fun(Process* p,		/* Current process. */
     }
 }
 
-static UWord*
+static BeamInstr*
 apply_fun(Process* p, Eterm fun, Eterm args, Eterm* reg)
 {
     int arity;
@@ -6211,7 +6211,7 @@ erts_is_builtin(Eterm Mod, Eterm Name, int arity)
     if ((ep = export_get(&e)) == NULL) {
 	return 0;
     }
-    return ep->address == ep->code+3 && (ep->code[3] == (UWord) em_apply_bif);
+    return ep->address == ep->code+3 && (ep->code[3] == (BeamInstr) em_apply_bif);
 }
 
 
diff --git a/erts/emulator/beam/beam_load.c b/erts/emulator/beam/beam_load.c
index b928b04210..5b56002d3b 100644
--- a/erts/emulator/beam/beam_load.c
+++ b/erts/emulator/beam/beam_load.c
@@ -51,9 +51,9 @@ ErlDrvBinary* erts_gzinflate_buffer(char*, int);
 #define EXPORTED  2
 
 #ifdef NO_JUMP_TABLE
-#  define BeamOpCode(Op) ((UWord)(Op))
+#  define BeamOpCode(Op) ((BeamInstr)(Op))
 #else
-#  define BeamOpCode(Op) ((UWord)beam_ops[Op])
+#  define BeamOpCode(Op) ((BeamInstr)beam_ops[Op])
 #endif
 
 #if defined(WORDS_BIGENDIAN)
@@ -94,7 +94,7 @@ typedef struct {
 
 typedef struct {
     unsigned type;		/* Type of operand. */
-    UWord val;			/* Value of operand. */
+    BeamInstr val;			/* Value of operand. */
     Uint bigarity;		/* Arity for bignumbers (only). */
 } GenOpArg;
 
@@ -142,7 +142,7 @@ typedef struct {
 typedef struct {
     Eterm function;		/* Tagged atom for function. */
     int arity;			/* Arity. */
-    UWord* address;		/* Address to function in code. */
+    BeamInstr* address;		/* Address to function in code. */
 } ExportEntry;
 
 #define MakeIffId(a, b, c, d) \
@@ -274,13 +274,13 @@ typedef struct {
     int num_functions;		/* Number of functions in module. */
     int num_labels;		/* Number of labels. */
     int code_buffer_size;	/* Size of code buffer in words.  */
-    UWord* code;		/* Loaded code. */
+    BeamInstr* code;		/* Loaded code. */
     int ci;			/* Current index into loaded code. */
     Label* labels;
-    UWord put_strings;		/* Linked list of put_string instructions. */
-    UWord new_bs_put_strings;	/* Linked list of i_new_bs_put_string instructions. */
+    BeamInstr put_strings;		/* Linked list of put_string instructions. */
+    BeamInstr new_bs_put_strings;	/* Linked list of i_new_bs_put_string instructions. */
     StringPatch* string_patches; /* Linked list of position into string table to patch. */
-    UWord catches;		/* Linked list of catch_yf instructions. */
+    BeamInstr catches;		/* Linked list of catch_yf instructions. */
     unsigned loaded_size;	/* Final size of code when loaded. */
     byte mod_md5[16];		/* MD5 for module code. */
     int may_load_nif;           /* true if NIFs may later be loaded for this module */  
@@ -341,7 +341,7 @@ typedef struct {
 
 #define GetTagAndValue(Stp, Tag, Val) \
    do { \
-      UWord __w; \
+      BeamInstr __w; \
       GetByte(Stp, __w); \
       Tag = __w & 0x07; \
       if ((__w & 0x08) == 0) { \
@@ -388,7 +388,7 @@ typedef struct {
        goto load_error; \
     } else { \
        int __n = (N); \
-       UWord __result = 0; \
+       BeamInstr __result = 0; \
        Stp->file_left -= (unsigned) __n; \
        while (__n-- > 0) { \
           __result = __result << 8 | *Stp->file_p++; \
@@ -465,7 +465,7 @@ static int bin_load(Process *c_p, ErtsProcLocks c_p_locks,
 static void init_state(LoaderState* stp);
 static int insert_new_code(Process *c_p, ErtsProcLocks c_p_locks,
 			   Eterm group_leader, Eterm module,
-			   UWord* code, Uint size, UWord catches);
+			   BeamInstr* code, Uint size, BeamInstr catches);
 static int scan_iff_file(LoaderState* stp, Uint* chunk_types,
 			 Uint num_types, Uint num_mandatory);
 static int load_atom_table(LoaderState* stp);
@@ -499,8 +499,8 @@ static void load_printf(int line, LoaderState* context, char *fmt, ...);
 static int transform_engine(LoaderState* st);
 static void id_to_string(Uint id, char* s);
 static void new_genop(LoaderState* stp);
-static int get_int_val(LoaderState* stp, Uint len_code, UWord* result);
-static int get_erlang_integer(LoaderState* stp, Uint len_code, UWord* result);
+static int get_int_val(LoaderState* stp, Uint len_code, BeamInstr* result);
+static int get_erlang_integer(LoaderState* stp, Uint len_code, BeamInstr* result);
 static int new_label(LoaderState* stp);
 static void new_literal_patch(LoaderState* stp, int pos);
 static void new_string_patch(LoaderState* stp, int pos);
@@ -592,7 +592,8 @@ erts_load_module(Process *c_p,
     return result;
 }
 
-#ifdef DEBUG
+#if defined(LOAD_MEMORY_HARD_DEBUG) && defined(DEBUG)
+/* Requires allocators ERTS_ALLOC_UTIL_HARD_DEBUG also set in erl_alloc_util.h */
 extern void check_allocators(void);
 extern void check_allocated_block(Uint type, void *blk);
 #define CHKALLOC() check_allocators()
@@ -617,8 +618,8 @@ bin_load(Process *c_p, ErtsProcLocks c_p_locks,
      * Scan the IFF file.
      */
 
-#ifdef DEBUG
-    fprintf(stderr,"Loading a module\r\n");
+#if defined(LOAD_MEMORY_HARD_DEBUG) && defined(DEBUG)
+    erts_fprintf(stderr,"Loading a module\n");
 #endif
 
     CHKALLOC();
@@ -785,8 +786,8 @@ bin_load(Process *c_p, ErtsProcLocks c_p_locks,
 	erts_free(ERTS_ALC_T_LOADER_TMP, (void *) state.genop_blocks);
 	state.genop_blocks = next;
     }
-#ifdef DEBUG
-    erts_fprintf(stderr,"Loaded %T\r\n",*modp);
+#if defined(LOAD_MEMORY_HARD_DEBUG) && defined(DEBUG)
+    erts_fprintf(stderr,"Loaded %T\n",*modp);
 #endif
 
     return rval;
@@ -824,7 +825,7 @@ init_state(LoaderState* stp)
 
 static int
 insert_new_code(Process *c_p, ErtsProcLocks c_p_locks,
-		Eterm group_leader, Eterm module, UWord* code, Uint size, UWord catches)
+		Eterm group_leader, Eterm module, BeamInstr* code, Uint size, BeamInstr catches)
 {
     Module* modp;
     int rval;
@@ -866,7 +867,7 @@ insert_new_code(Process *c_p, ErtsProcLocks c_p_locks,
 	modules[i] = modules[i-1];
     }
     modules[i].start = code;
-    modules[i].end = (UWord *) (((byte *)code) + size);
+    modules[i].end = (BeamInstr *) (((byte *)code) + size);
     num_loaded_modules++;
     mid_module = &modules[num_loaded_modules/2];
     return 0;
@@ -1116,7 +1117,7 @@ load_import_table(LoaderState* stp)
 	 * the BIF function.
 	 */
 	if ((e = erts_find_export_entry(mod, func, arity)) != NULL) {
-	    if (e->code[3] == (UWord) em_apply_bif) {
+	    if (e->code[3] == (BeamInstr) em_apply_bif) {
 		stp->import[i].bf = (BifFunction) e->code[4];
 		if (func == am_load_nif && mod == am_erlang && arity == 2) {
 		    stp->may_load_nif = 1;
@@ -1184,7 +1185,7 @@ read_export_table(LoaderState* stp)
 	 * redefine).
 	 */
 	if ((e = erts_find_export_entry(stp->module, func, arity)) != NULL) {
-	    if (e->code[3] == (UWord) em_apply_bif) {
+	    if (e->code[3] == (BeamInstr) em_apply_bif) {
 		int j;
 
 		for (j = 0; j < sizeof(allow_redef)/sizeof(allow_redef[0]); j++) {
@@ -1253,7 +1254,7 @@ static int
 read_literal_table(LoaderState* stp)
 {
     int i;
-    UWord uncompressed_sz;
+    BeamInstr uncompressed_sz;
     byte* uncompressed = 0;
 
     GetInt(stp, 4, uncompressed_sz);
@@ -1371,8 +1372,8 @@ read_code_header(LoaderState* stp)
      * Initialize code area.
      */
     stp->code_buffer_size = erts_next_heap_size(2048 + stp->num_functions, 0);
-    stp->code = (UWord *) erts_alloc(ERTS_ALC_T_CODE,
-				    sizeof(UWord) * stp->code_buffer_size);
+    stp->code = (BeamInstr *) erts_alloc(ERTS_ALC_T_CODE,
+				    sizeof(BeamInstr) * stp->code_buffer_size);
 
     stp->code[MI_NUM_FUNCTIONS] = stp->num_functions;
     stp->ci = MI_FUNCTIONS + stp->num_functions + 1;
@@ -1403,13 +1404,13 @@ read_code_header(LoaderState* stp)
     if (code_buffer_size < ci+(w)) {					\
         code_buffer_size = erts_next_heap_size(ci+(w), 0);		\
 	stp->code = code						\
-	    = (UWord *) erts_realloc(ERTS_ALC_T_CODE,			\
+	    = (BeamInstr *) erts_realloc(ERTS_ALC_T_CODE,			\
 				     (void *) code,			\
-				     code_buffer_size * sizeof(UWord));	\
+				     code_buffer_size * sizeof(BeamInstr));	\
     } 									\
 } while (0)
     
-#define TermWords(t) (((t) / (sizeof(UWord)/sizeof(Eterm))) + !!((t) % (sizeof(UWord)/sizeof(Eterm))))
+#define TermWords(t) (((t) / (sizeof(BeamInstr)/sizeof(Eterm))) + !!((t) % (sizeof(BeamInstr)/sizeof(Eterm))))
 
 
 static int
@@ -1422,7 +1423,7 @@ load_code(LoaderState* stp)
     char* sign;
     int arg;			/* Number of current argument. */
     int num_specific;		/* Number of specific ops for current. */
-    UWord* code;
+    BeamInstr* code;
     int code_buffer_size;
     int specific;
     Uint last_label = 0;	/* Number of last label. */
@@ -1481,7 +1482,7 @@ load_code(LoaderState* stp)
       if (((First) & 0x08) == 0) { \
 	 Val = (First) >> 4; \
       } else if (((First) & 0x10) == 0) { \
-         UWord __w; \
+         BeamInstr __w; \
 	 GetByte(Stp, __w); \
 	 Val = (((First) >> 5) << 8) | __w; \
       } else { \
@@ -1490,7 +1491,7 @@ load_code(LoaderState* stp)
    } while (0)
 
 	for (arg = 0; arg < arity; arg++) {
-	    UWord first;
+	    BeamInstr first;
 
 	    GetByte(stp, first);
 	    last_op->a[arg].type = first & 0x07;
@@ -1499,7 +1500,7 @@ load_code(LoaderState* stp)
 		if ((first & 0x08) == 0) {
 		    last_op->a[arg].val = first >> 4;
 		} else if ((first & 0x10) == 0) {
-		    UWord w;
+		    BeamInstr w;
 		    GetByte(stp, w);
 		    ASSERT(first < 0x800);
 		    last_op->a[arg].val = ((first >> 5) << 8) | w;
@@ -1558,7 +1559,7 @@ load_code(LoaderState* stp)
 		break;
 	    case TAG_z:
 		{
-		    UWord ext_tag;
+		    BeamInstr ext_tag;
 		    unsigned tag;
 
 		    GetValue(stp, first, ext_tag);
@@ -1610,10 +1611,10 @@ load_code(LoaderState* stp)
 			break;
 		    case 3: 	/* Allocation list. */
 			{
-			    UWord n;
-			    UWord type;
-			    UWord val;
-			    UWord words = 0;
+			    BeamInstr n;
+			    BeamInstr type;
+			    BeamInstr val;
+			    BeamInstr words = 0;
 			    
 			    stp->new_float_instructions = 1;
 			    GetTagAndValue(stp, tag, n);
@@ -1642,7 +1643,7 @@ load_code(LoaderState* stp)
 			}
 		    case 4:	/* Literal. */
 			{
-			    UWord val;
+			    BeamInstr val;
 
 			    GetTagAndValue(stp, tag, val);
 			    VerifyTag(stp, tag, TAG_u);
@@ -1807,7 +1808,7 @@ load_code(LoaderState* stp)
 	    case 'c':		/* Tagged constant */
 		switch (tag) {
 		case TAG_i:
-		    code[ci++] = (UWord) make_small((Uint) tmp_op->a[arg].val);
+		    code[ci++] = (BeamInstr) make_small((Uint) tmp_op->a[arg].val);
 		    break;
 		case TAG_a:
 		    code[ci++] = tmp_op->a[arg].val;
@@ -1837,7 +1838,7 @@ load_code(LoaderState* stp)
 		    code[ci++] = make_yreg(tmp_op->a[arg].val);
 		    break;
 		case TAG_i:
-		    code[ci++] = (UWord) make_small((Uint)tmp_op->a[arg].val);
+		    code[ci++] = (BeamInstr) make_small((Uint)tmp_op->a[arg].val);
 		    break;
 		case TAG_a:
 		    code[ci++] = tmp_op->a[arg].val;
@@ -1931,12 +1932,12 @@ load_code(LoaderState* stp)
 		if (stp->import[i].bf == NULL) {
 		    LoadError1(stp, "not a BIF: import table index %d", i);
 		}
-		code[ci++] = (UWord) stp->import[i].bf;
+		code[ci++] = (BeamInstr) stp->import[i].bf;
 		break;
 	    case 'P':		/* Byte offset into tuple */ /* XXX:PaN - * sizeof(Eterm or Eterm *) ? */
 		VerifyTag(stp, tag, TAG_u);
 		tmp = tmp_op->a[arg].val;
-		code[ci++] = (UWord) ((tmp_op->a[arg].val+1) * sizeof(Eterm));
+		code[ci++] = (BeamInstr) ((tmp_op->a[arg].val+1) * sizeof(Eterm));
 		break;
 	    case 'l':		/* Floating point register. */
 		VerifyTag(stp, tag_to_letter[tag], *sign);
@@ -2090,8 +2091,8 @@ load_code(LoaderState* stp)
 			int pad = MIN_FUNC_SZ - (finfo_ix - last_func_start);
 			ASSERT(pad > 0 && pad < MIN_FUNC_SZ);
 			CodeNeed(pad);
-			sys_memmove(&code[finfo_ix+pad], &code[finfo_ix], FINFO_SZ*sizeof(UWord));
-			sys_memset(&code[finfo_ix], 0, pad*sizeof(UWord));
+			sys_memmove(&code[finfo_ix+pad], &code[finfo_ix], FINFO_SZ*sizeof(BeamInstr));
+			sys_memset(&code[finfo_ix], 0, pad*sizeof(BeamInstr));
 			ci += pad;
 			stp->labels[last_label].value += pad;
 		    }
@@ -2910,7 +2911,7 @@ gen_literal_timeout(LoaderState* stp, GenOpArg Fail, GenOpArg Time)
 	} else {
 	    Uint u;
 	    (void) term_to_Uint(big, &u);
-	    op->a[1].val = (UWord) u;
+	    op->a[1].val = (BeamInstr) u;
 	}
 #endif
     } else {
@@ -2957,7 +2958,7 @@ gen_literal_timeout_locked(LoaderState* stp, GenOpArg Fail, GenOpArg Time)
 	} else {
 	    Uint u;
 	    (void) term_to_Uint(big, &u);
-	    op->a[1].val = (UWord) u;
+	    op->a[1].val = (BeamInstr) u;
 	}
 #endif
     } else {
@@ -3377,7 +3378,7 @@ gen_make_fun2(LoaderState* stp, GenOpArg idx)
     op->op = genop_i_make_fun_2;
     op->arity = 2;
     op->a[0].type = TAG_u;
-    op->a[0].val = (UWord) fe;
+    op->a[0].val = (BeamInstr) fe;
     op->a[1].type = TAG_u;
     op->a[1].val = stp->lambdas[idx.val].num_free;
     op->next = NULL;
@@ -3432,7 +3433,7 @@ gen_guard_bif(LoaderState* stp, GenOpArg Fail, GenOpArg Live, GenOpArg Bif,
 static int
 freeze_code(LoaderState* stp)
 {
-    UWord* code = stp->code;
+    BeamInstr* code = stp->code;
     Uint *literal_end = NULL;
     Uint index;
     int i;
@@ -3458,21 +3459,21 @@ freeze_code(LoaderState* stp)
      * Calculate the final size of the code.
      */
 
-    size = (stp->ci * sizeof(UWord)) + (stp->total_literal_size * sizeof(Eterm)) +
+    size = (stp->ci * sizeof(BeamInstr)) + (stp->total_literal_size * sizeof(Eterm)) +
 	strtab_size + attr_size + compile_size;
 
     /*
      * Move the code to its final location.
      */
 
-    code = (UWord *) erts_realloc(ERTS_ALC_T_CODE, (void *) code, size);
+    code = (BeamInstr *) erts_realloc(ERTS_ALC_T_CODE, (void *) code, size);
     CHKBLK(ERTS_ALC_T_CODE,code);
     /*
      * Place a pointer to the op_int_code_end instruction in the
      * function table in the beginning of the file.
      */
 
-    code[MI_FUNCTIONS+stp->num_functions] = (UWord) (code + stp->ci - 1);
+    code[MI_FUNCTIONS+stp->num_functions] = (BeamInstr) (code + stp->ci - 1);
     CHKBLK(ERTS_ALC_T_CODE,code);
 
     /*
@@ -3480,7 +3481,7 @@ freeze_code(LoaderState* stp)
      */
 
     if (stp->on_load) {
-	code[MI_ON_LOAD_FUNCTION_PTR] = (UWord) (code + stp->on_load);
+	code[MI_ON_LOAD_FUNCTION_PTR] = (BeamInstr) (code + stp->on_load);
     } else {
 	code[MI_ON_LOAD_FUNCTION_PTR] = 0;
     }
@@ -3499,8 +3500,8 @@ freeze_code(LoaderState* stp)
 
 	low = (Uint *) (code+stp->ci);
 	high = low + stp->total_literal_size;
-	code[MI_LITERALS_START] = (UWord) low;
-	code[MI_LITERALS_END] = (UWord) high;
+	code[MI_LITERALS_START] = (BeamInstr) low;
+	code[MI_LITERALS_END] = (BeamInstr) high;
 	ptr = low;
 	for (i = 0; i < stp->num_literals; i++) {
 	    Uint offset;
@@ -3532,7 +3533,7 @@ freeze_code(LoaderState* stp)
 	}
 	lp = stp->literal_patches;
 	while (lp != 0) {
-	    UWord* op_ptr;
+	    BeamInstr* op_ptr;
 	    Uint literal;
 	    Literal* lit;
 
@@ -3559,8 +3560,8 @@ freeze_code(LoaderState* stp)
     if (attr_size) {
 	byte* attr = str_table + strtab_size;
 	sys_memcpy(attr, stp->chunks[ATTR_CHUNK].start, stp->chunks[ATTR_CHUNK].size);
-	code[MI_ATTR_PTR] = (UWord) attr;
-	code[MI_ATTR_SIZE] = (UWord) stp->chunks[ATTR_CHUNK].size;
+	code[MI_ATTR_PTR] = (BeamInstr) attr;
+	code[MI_ATTR_SIZE] = (BeamInstr) stp->chunks[ATTR_CHUNK].size;
 	decoded_size = erts_decode_ext_size(attr, attr_size, 0);
 	if (decoded_size < 0) {
  	    LoadError0(stp, "bad external term representation of module attributes");
@@ -3574,9 +3575,9 @@ freeze_code(LoaderState* stp)
 	sys_memcpy(compile_info, stp->chunks[COMPILE_CHUNK].start,
 	       stp->chunks[COMPILE_CHUNK].size);
     CHKBLK(ERTS_ALC_T_CODE,code);
-	code[MI_COMPILE_PTR] = (UWord) compile_info;
+	code[MI_COMPILE_PTR] = (BeamInstr) compile_info;
     CHKBLK(ERTS_ALC_T_CODE,code);
-	code[MI_COMPILE_SIZE] = (UWord) stp->chunks[COMPILE_CHUNK].size;
+	code[MI_COMPILE_SIZE] = (BeamInstr) stp->chunks[COMPILE_CHUNK].size;
     CHKBLK(ERTS_ALC_T_CODE,code);
 	decoded_size = erts_decode_ext_size(compile_info, compile_size, 0);
     CHKBLK(ERTS_ALC_T_CODE,code);
@@ -3599,7 +3600,7 @@ freeze_code(LoaderState* stp)
     while (index != 0) {
 	Uint next = code[index];
 	code[index] = BeamOpCode(op_put_string_IId);
-	code[index+2] = (UWord) (str_table + code[index+2] + code[index+1] - 1);
+	code[index+2] = (BeamInstr) (str_table + code[index+2] + code[index+1] - 1);
 	index = next;
     }
     CHKBLK(ERTS_ALC_T_CODE,code);
@@ -3614,7 +3615,7 @@ freeze_code(LoaderState* stp)
     while (index != 0) {
 	Uint next = code[index];
 	code[index] = BeamOpCode(op_bs_put_string_II);
-	code[index+2] = (UWord) (str_table + code[index+2]);
+	code[index+2] = (BeamInstr) (str_table + code[index+2]);
 	index = next;
     }
     CHKBLK(ERTS_ALC_T_CODE,code);
@@ -3623,12 +3624,12 @@ freeze_code(LoaderState* stp)
 	StringPatch* sp = stp->string_patches;
 
 	while (sp != 0) {
-	    UWord* op_ptr;
+	    BeamInstr* op_ptr;
 	    byte* strp;
 
 	    op_ptr = code + sp->pos;
 	    strp = str_table + op_ptr[0];
-	    op_ptr[0] = (UWord) strp;
+	    op_ptr[0] = (BeamInstr) strp;
 	    sp = sp->next;
 	}
     }
@@ -3652,7 +3653,7 @@ freeze_code(LoaderState* stp)
 	    ASSERT(this_patch < stp->ci);
 	    next_patch = code[this_patch];
 	    ASSERT(next_patch < stp->ci);
-	    code[this_patch] = (UWord) (code + value);
+	    code[this_patch] = (BeamInstr) (code + value);
 	    this_patch = next_patch;
 	}
     }
@@ -3664,9 +3665,9 @@ freeze_code(LoaderState* stp)
     index = stp->catches;
     catches = BEAM_CATCHES_NIL;
     while (index != 0) {
-	UWord next = code[index];
+	BeamInstr next = code[index];
 	code[index] = BeamOpCode(op_catch_yf);
-	catches = beam_catches_cons((UWord *)code[index+2], catches);
+	catches = beam_catches_cons((BeamInstr *)code[index+2], catches);
 	code[index+2] = make_catch(catches);
 	index = next;
     }
@@ -3714,7 +3715,7 @@ final_touch(LoaderState* stp)
 	     * callable yet.
 	     */
 	    ep->address = ep->code+3;
-	    ep->code[4] = (UWord) stp->export[i].address;
+	    ep->code[4] = (BeamInstr) stp->export[i].address;
 	}
     }
 
@@ -3726,14 +3727,14 @@ final_touch(LoaderState* stp)
 	Eterm mod;
 	Eterm func;
 	Uint arity;
-	UWord import;
+	BeamInstr import;
 	Uint current;
 	Uint next;
 
 	mod = stp->import[i].module;
 	func = stp->import[i].function;
 	arity = stp->import[i].arity;
-	import = (UWord) erts_export_put(mod, func, arity);
+	import = (BeamInstr) erts_export_put(mod, func, arity);
 	current = stp->import[i].patches;
 	while (current != 0) {
 	    ASSERT(current < stp->ci);
@@ -3751,7 +3752,7 @@ final_touch(LoaderState* stp)
 	for (i = 0; i < stp->num_lambdas; i++) {
 	    unsigned entry_label = stp->lambdas[i].label;
 	    ErlFunEntry* fe = stp->lambdas[i].fe;
-	    UWord* code_ptr = (UWord *) (stp->code + stp->labels[entry_label].value);
+	    BeamInstr* code_ptr = (BeamInstr *) (stp->code + stp->labels[entry_label].value);
 
 	    if (fe->address[0] != 0) {
 		/*
@@ -3883,7 +3884,7 @@ transform_engine(LoaderState* st)
 		if (i >= st->num_imports || st->import[i].bf == NULL)
 		    goto restart;
 		if (bif_number != -1 &&
-		    bif_export[bif_number]->code[4] != (UWord) st->import[i].bf) {
+		    bif_export[bif_number]->code[4] != (BeamInstr) st->import[i].bf) {
 		    goto restart;
 		}
 	    }
@@ -4147,7 +4148,7 @@ load_printf(int line, LoaderState* context, char *fmt,...)
 
 
 static int
-get_int_val(LoaderState* stp, Uint len_code, UWord* result)
+get_int_val(LoaderState* stp, Uint len_code, BeamInstr* result)
 {
     Uint count;
     Uint val;
@@ -4179,7 +4180,7 @@ get_int_val(LoaderState* stp, Uint len_code, UWord* result)
 
 
 static int
-get_erlang_integer(LoaderState* stp, Uint len_code, UWord* result)
+get_erlang_integer(LoaderState* stp, Uint len_code, BeamInstr* result)
 {
     Uint count;
     Sint val;
@@ -4453,7 +4454,7 @@ functions_in_module(Process* p, /* Process whose heap to use. */
 		     Eterm mod) /* Tagged atom for module. */
 {
     Module* modp;
-    UWord* code;
+    BeamInstr* code;
     int i;
     Uint num_functions;
     Eterm* hp;
@@ -4471,7 +4472,7 @@ functions_in_module(Process* p, /* Process whose heap to use. */
     num_functions = code[MI_NUM_FUNCTIONS];
     hp = HAlloc(p, 5*num_functions);
     for (i = num_functions-1; i >= 0 ; i--) {
-	UWord* func_info = (UWord *) code[MI_FUNCTIONS+i];
+	BeamInstr* func_info = (BeamInstr *) code[MI_FUNCTIONS+i];
 	Eterm name = (Eterm) func_info[3];
 	int arity = (int) func_info[4];
 	Eterm tuple;
@@ -4496,7 +4497,7 @@ static Eterm
 native_addresses(Process* p, Eterm mod)
 {
     Module* modp;
-    UWord* code;
+    BeamInstr* code;
     int i;
     Eterm* hp;
     Uint num_functions;
@@ -4519,7 +4520,7 @@ native_addresses(Process* p, Eterm mod)
     hp = HAlloc(p, need);
     hp_end = hp + need;
     for (i = num_functions-1; i >= 0 ; i--) {
-	UWord* func_info = (UWord *) code[MI_FUNCTIONS+i];
+	BeamInstr* func_info = (BeamInstr *) code[MI_FUNCTIONS+i];
 	Eterm name = (Eterm) func_info[3];
 	int arity = (int) func_info[4];
 	Eterm tuple;
@@ -4563,7 +4564,7 @@ exported_from_module(Process* p, /* Process whose heap to use. */
 	    Eterm tuple;
 	    
 	    if (ep->address == ep->code+3 &&
-		ep->code[3] == (UWord) em_call_error_handler) {
+		ep->code[3] == (BeamInstr) em_call_error_handler) {
 		/* There is a call to the function, but it does not exist. */ 
 		continue;
 	    }
@@ -4596,7 +4597,7 @@ attributes_for_module(Process* p, /* Process whose heap to use. */
 
 {
     Module* modp;
-    UWord* code;
+    BeamInstr* code;
     Eterm* hp;
     byte* ext;
     Eterm result = NIL;
@@ -4636,7 +4637,7 @@ compilation_info_for_module(Process* p, /* Process whose heap to use. */
 			    Eterm mod) /* Tagged atom for module. */
 {
     Module* modp;
-    UWord* code;
+    BeamInstr* code;
     Eterm* hp;
     byte* ext;
     Eterm result = NIL;
@@ -4668,8 +4669,8 @@ compilation_info_for_module(Process* p, /* Process whose heap to use. */
 /*
  * Returns a pointer to {module, function, arity}, or NULL if not found.
  */
-UWord *
-find_function_from_pc(UWord* pc)
+BeamInstr *
+find_function_from_pc(BeamInstr* pc)
 {
     Range* low = modules;
     Range* high = low + num_loaded_modules;
@@ -4681,9 +4682,9 @@ find_function_from_pc(UWord* pc)
 	} else if (pc > mid->end) {
 	    low = mid + 1;
 	} else {
-	    UWord** low1 = (UWord **) (mid->start + MI_FUNCTIONS);
-	    UWord** high1 = low1 + mid->start[MI_NUM_FUNCTIONS];
-	    UWord** mid1;
+	    BeamInstr** low1 = (BeamInstr **) (mid->start + MI_FUNCTIONS);
+	    BeamInstr** high1 = low1 + mid->start[MI_NUM_FUNCTIONS];
+	    BeamInstr** mid1;
 
 	    while (low1 < high1) {
 		mid1 = low1 + (high1-low1) / 2;
@@ -4796,10 +4797,10 @@ code_module_md5_1(Process* p, Eterm Bin)
 
 #define WORDS_PER_FUNCTION 6
 
-static UWord*
-make_stub(UWord* fp, Eterm mod, Eterm func, Uint arity, Uint native, UWord OpCode)
+static BeamInstr*
+make_stub(BeamInstr* fp, Eterm mod, Eterm func, Uint arity, Uint native, BeamInstr OpCode)
 {
-    fp[0] = (UWord) BeamOp(op_i_func_info_IaaI);
+    fp[0] = (BeamInstr) BeamOp(op_i_func_info_IaaI);
     fp[1] = native;
     fp[2] = mod;
     fp[3] = func;
@@ -4818,14 +4819,14 @@ static byte*
 stub_copy_info(LoaderState* stp,
 	       int chunk,	/* Chunk: ATTR_CHUNK or COMPILE_CHUNK */
 	       byte* info,	/* Where to store info. */
-	       UWord* ptr_word,	/* Where to store pointer into info. */
-	       UWord* size_word) /* Where to store size of info. */
+	       BeamInstr* ptr_word,	/* Where to store pointer into info. */
+	       BeamInstr* size_word) /* Where to store size of info. */
 {
     Sint decoded_size;
     Uint size = stp->chunks[chunk].size;
     if (size != 0) {
 	memcpy(info, stp->chunks[chunk].start, size);
-	*ptr_word = (UWord) info;
+	*ptr_word = (BeamInstr) info;
 	decoded_size = erts_decode_ext_size(info, size, 0);
 	if (decoded_size < 0) {
  	    return 0;
@@ -4868,7 +4869,7 @@ stub_read_export_table(LoaderState* stp)
 }
 
 static void
-stub_final_touch(LoaderState* stp, UWord* fp)
+stub_final_touch(LoaderState* stp, BeamInstr* fp)
 {
     int i;
     int n = stp->num_exps;
@@ -5055,12 +5056,12 @@ Eterm
 erts_make_stub_module(Process* p, Eterm Mod, Eterm Beam, Eterm Info)
 {
     LoaderState state;
-    UWord Funcs;
-    UWord Patchlist;
+    BeamInstr Funcs;
+    BeamInstr Patchlist;
     Eterm* tp;
-    UWord* code = NULL;
-    UWord* ptrs;
-    UWord* fp;
+    BeamInstr* code = NULL;
+    BeamInstr* ptrs;
+    BeamInstr* fp;
     byte* info;
     Uint ci;
     int n;
@@ -5149,7 +5150,7 @@ erts_make_stub_module(Process* p, Eterm Mod, Eterm Beam, Eterm Info)
      * Allocate memory for the stub module.
      */
 
-    code_size = ((WORDS_PER_FUNCTION+1)*n + MI_FUNCTIONS + 2) * sizeof(UWord);
+    code_size = ((WORDS_PER_FUNCTION+1)*n + MI_FUNCTIONS + 2) * sizeof(BeamInstr);
     code_size += state.chunks[ATTR_CHUNK].size;
     code_size += state.chunks[COMPILE_CHUNK].size;
     code = erts_alloc_fnf(ERTS_ALC_T_CODE, code_size);
@@ -5218,7 +5219,7 @@ erts_make_stub_module(Process* p, Eterm Mod, Eterm Beam, Eterm Info)
 	 * Set the pointer and make the stub. Put a return instruction
 	 * as the body until we know what kind of trap we should put there.
 	 */
-	ptrs[i] = (UWord) fp;
+	ptrs[i] = (BeamInstr) fp;
 #ifdef HIPE
 	op = (Eterm) BeamOpCode(op_hipe_trap_call); /* Might be changed later. */
 #else
@@ -5231,8 +5232,8 @@ erts_make_stub_module(Process* p, Eterm Mod, Eterm Beam, Eterm Info)
      * Insert the last pointer and the int_code_end instruction.
      */
 
-    ptrs[i] = (UWord) fp;
-    *fp++ = (UWord) BeamOp(op_int_code_end);
+    ptrs[i] = (BeamInstr) fp;
+    *fp++ = (BeamInstr) BeamOp(op_int_code_end);
 
     /*
      * Copy attributes and compilation information.
diff --git a/erts/emulator/beam/beam_load.h b/erts/emulator/beam/beam_load.h
index a24460d2a5..ce6bd5b678 100644
--- a/erts/emulator/beam/beam_load.h
+++ b/erts/emulator/beam/beam_load.h
@@ -44,13 +44,13 @@ extern void** beam_ops;
 #endif
 
 
-extern UWord beam_debug_apply[];
-extern UWord* em_call_error_handler;
-extern UWord* em_apply_bif;
-extern UWord* em_call_traced_function;
+extern BeamInstr beam_debug_apply[];
+extern BeamInstr* em_call_error_handler;
+extern BeamInstr* em_apply_bif;
+extern BeamInstr* em_call_traced_function;
 typedef struct {
-    UWord* start;		/* Pointer to start of module. */
-    UWord* end;			/* Points one word beyond last function in module. */
+    BeamInstr* start;		/* Pointer to start of module. */
+    BeamInstr* end;			/* Points one word beyond last function in module. */
 } Range;
 
 /*
diff --git a/erts/emulator/beam/bif.c b/erts/emulator/beam/bif.c
index 3aa258b675..c06d92ed45 100644
--- a/erts/emulator/beam/bif.c
+++ b/erts/emulator/beam/bif.c
@@ -4125,8 +4125,8 @@ void erts_init_bif(void)
 #else
     bif_return_trap_export.code[2] = 1;
 #endif
-    bif_return_trap_export.code[3] = (UWord) em_apply_bif;
-    bif_return_trap_export.code[4] = (UWord) &bif_return_trap;
+    bif_return_trap_export.code[3] = (BeamInstr) em_apply_bif;
+    bif_return_trap_export.code[4] = (BeamInstr) &bif_return_trap;
 
     flush_monitor_message_trap = erts_export_put(am_erlang,
 						 am_flush_monitor_message,
diff --git a/erts/emulator/beam/break.c b/erts/emulator/beam/break.c
index 0b7afcac02..c5aa00bc07 100644
--- a/erts/emulator/beam/break.c
+++ b/erts/emulator/beam/break.c
@@ -381,7 +381,7 @@ loaded(int to, void *to_arg)
     int i;
     int old = 0;
     int cur = 0;
-    UWord* code;
+    BeamInstr* code;
 
     /*
      * Calculate and print totals.
diff --git a/erts/emulator/beam/erl_alloc_util.h b/erts/emulator/beam/erl_alloc_util.h
index e805883ddc..79f0348dd2 100644
--- a/erts/emulator/beam/erl_alloc_util.h
+++ b/erts/emulator/beam/erl_alloc_util.h
@@ -150,7 +150,7 @@ void    erts_alcu_current_size(Allctr_t *, AllctrSize_t *);
 
 #undef ERTS_ALLOC_UTIL_HARD_DEBUG
 #ifdef DEBUG
-#  if 1
+#  if 0
 #    define ERTS_ALLOC_UTIL_HARD_DEBUG
 #  endif
 #endif
diff --git a/erts/emulator/beam/erl_bif_chksum.c b/erts/emulator/beam/erl_bif_chksum.c
index e76b0b9252..a5c9944789 100644
--- a/erts/emulator/beam/erl_bif_chksum.c
+++ b/erts/emulator/beam/erl_bif_chksum.c
@@ -49,9 +49,9 @@ void erts_init_bif_chksum(void)
     chksum_md5_2_exp.code[1] = am_atom_put("md5_trap",8);
     chksum_md5_2_exp.code[2] = 2;
     chksum_md5_2_exp.code[3] =
-	(UWord) em_apply_bif;
+	(BeamInstr) em_apply_bif;
     chksum_md5_2_exp.code[4] = 
-	(UWord) &md5_2;
+	(BeamInstr) &md5_2;
 }
     
 
diff --git a/erts/emulator/beam/erl_bif_info.c b/erts/emulator/beam/erl_bif_info.c
index 40f8b7f23a..fc8d876bc4 100644
--- a/erts/emulator/beam/erl_bif_info.c
+++ b/erts/emulator/beam/erl_bif_info.c
@@ -1010,7 +1010,7 @@ process_info_aux(Process *BIF_P,
 	    hp = HAlloc(BIF_P, 3);
 	    res = am_undefined;
 	} else {
-	    UWord* current;
+	    BeamInstr* current;
 
 	    if (rp->current[0] == am_erlang &&
 		rp->current[1] == am_process_info &&
diff --git a/erts/emulator/beam/erl_bif_re.c b/erts/emulator/beam/erl_bif_re.c
index 4b527ce215..d4a8a3aaa7 100644
--- a/erts/emulator/beam/erl_bif_re.c
+++ b/erts/emulator/beam/erl_bif_re.c
@@ -76,8 +76,8 @@ void erts_init_bif_re(void)
     re_exec_trap_export.code[0] = am_erlang;
     re_exec_trap_export.code[1] = am_re_run_trap;
     re_exec_trap_export.code[2] = 3;
-    re_exec_trap_export.code[3] = (UWord) em_apply_bif;
-    re_exec_trap_export.code[4] = (UWord) &re_exec_trap;
+    re_exec_trap_export.code[3] = (BeamInstr) em_apply_bif;
+    re_exec_trap_export.code[4] = (BeamInstr) &re_exec_trap;
 
     grun_trap_exportp =  erts_export_put(am_re,am_grun,3);
     urun_trap_exportp =  erts_export_put(am_re,am_urun,3);
diff --git a/erts/emulator/beam/erl_bif_trace.c b/erts/emulator/beam/erl_bif_trace.c
index c46a0074fc..76e6a74112 100644
--- a/erts/emulator/beam/erl_bif_trace.c
+++ b/erts/emulator/beam/erl_bif_trace.c
@@ -954,7 +954,7 @@ static int function_is_traced(Eterm mfa[3],
     Export e;
     Export* ep;
     int i;
-    Uint *code;
+    BeamInstr *code;
 
     /* First look for an export entry */
     e.code[0] = mfa[0];
@@ -962,12 +962,12 @@ static int function_is_traced(Eterm mfa[3],
     e.code[2] = mfa[2];
     if ((ep = export_get(&e)) != NULL) {
 	if (ep->address == ep->code+3 &&
-	    ep->code[3] != (UWord) em_call_error_handler) {
-	    if (ep->code[3] == (UWord) em_call_traced_function) {
+	    ep->code[3] != (BeamInstr) em_call_error_handler) {
+	    if (ep->code[3] == (BeamInstr) em_call_traced_function) {
 		*ms = ep->match_prog_set;
 		return FUNC_TRACE_GLOBAL_TRACE;
 	    }
-	    if (ep->code[3] == (UWord) em_apply_bif) {
+	    if (ep->code[3] == (BeamInstr) em_apply_bif) {
 		for (i = 0; i < BIF_SIZE; ++i) {
 		    if (bif_export[i] == ep) {
 			int r = 0;
@@ -1321,7 +1321,7 @@ erts_set_trace_pattern(Eterm* mfa, int specified,
 		    if (erts_bif_trace_flags[i] & BIF_TRACE_AS_META) {
 			ASSERT(ExportIsBuiltIn(bif_export[i]));
 			erts_clear_mtrace_bif
-			    ((Uint *)bif_export[i]->code + 3);
+			    ((BeamInstr *)bif_export[i]->code + 3);
 			erts_bif_trace_flags[i] &= ~BIF_TRACE_AS_META;
 		    }
 		    set_trace_bif(i, match_prog_set);
@@ -1350,7 +1350,7 @@ erts_set_trace_pattern(Eterm* mfa, int specified,
 		    }
 		    if (flags.meta) {
 			erts_set_mtrace_bif
-			    ((Uint *)bif_export[i]->code + 3,
+			    ((BeamInstr *)bif_export[i]->code + 3,
 			     meta_match_prog_set, meta_tracer_pid);
 			erts_bif_trace_flags[i] |= BIF_TRACE_AS_META;
 			erts_bif_trace_flags[i] &= ~BIF_TRACE_AS_GLOBAL;
@@ -1370,7 +1370,7 @@ erts_set_trace_pattern(Eterm* mfa, int specified,
 		    if (flags.meta) {
 			if (erts_bif_trace_flags[i] & BIF_TRACE_AS_META) {
 			    erts_clear_mtrace_bif
-				((Uint *)bif_export[i]->code + 3);
+				((BeamInstr *)bif_export[i]->code + 3);
 			    erts_bif_trace_flags[i] &= ~BIF_TRACE_AS_META;
 			}
 			m = 1;
@@ -1439,9 +1439,9 @@ static int
 setup_func_trace(Export* ep, void* match_prog)
 {
     if (ep->address == ep->code+3) {
-	if (ep->code[3] == (UWord) em_call_error_handler) {
+	if (ep->code[3] == (BeamInstr) em_call_error_handler) {
 	    return 0;
-	} else if (ep->code[3] == (UWord) em_call_traced_function) {
+	} else if (ep->code[3] == (BeamInstr) em_call_traced_function) {
 	    MatchSetUnref(ep->match_prog_set);
 	    ep->match_prog_set = match_prog;
 	    MatchSetRef(ep->match_prog_set);
@@ -1461,8 +1461,8 @@ setup_func_trace(Export* ep, void* match_prog)
 	return 0;
     }
     
-    ep->code[3] = (UWord) em_call_traced_function;
-    ep->code[4] = (UWord) ep->address;
+    ep->code[3] = (BeamInstr) em_call_traced_function;
+    ep->code[4] = (BeamInstr) ep->address;
     ep->address = ep->code+3;
     ep->match_prog_set = match_prog;
     MatchSetRef(ep->match_prog_set);
@@ -1474,7 +1474,7 @@ static void setup_bif_trace(int bif_index) {
     
     ASSERT(ExportIsBuiltIn(ep));
     ASSERT(ep->code[4]);
-    ep->code[4] = (UWord) bif_table[bif_index].traced;
+    ep->code[4] = (BeamInstr) bif_table[bif_index].traced;
 }
 
 static void set_trace_bif(int bif_index, void* match_prog) {
@@ -1501,9 +1501,9 @@ static int
 reset_func_trace(Export* ep)
 {
     if (ep->address == ep->code+3) {
-	if (ep->code[3] == (UWord) em_call_error_handler) {
+	if (ep->code[3] == (BeamInstr) em_call_error_handler) {
 	    return 0;
-	} else if (ep->code[3] == (UWord) em_call_traced_function) {
+	} else if (ep->code[3] == (BeamInstr) em_call_traced_function) {
 	    ep->address = (Uint *) ep->code[4];
 	    MatchSetUnref(ep->match_prog_set);
 	    ep->match_prog_set = NULL;
@@ -1536,8 +1536,8 @@ static void reset_bif_trace(int bif_index) {
     ASSERT(ExportIsBuiltIn(ep));
     ASSERT(ep->code[4]);
     ASSERT(! ep->match_prog_set);
-    ASSERT(! erts_is_mtrace_bif((UWord *)ep->code+3, NULL, NULL));
-    ep->code[4] = (UWord) bif_table[bif_index].f;
+    ASSERT(! erts_is_mtrace_bif((BeamInstr *)ep->code+3, NULL, NULL));
+    ep->code[4] = (BeamInstr) bif_table[bif_index].f;
 }
 
 static void clear_trace_bif(int bif_index) {
diff --git a/erts/emulator/beam/erl_db.c b/erts/emulator/beam/erl_db.c
index 959f7fa37c..88a9e56854 100644
--- a/erts/emulator/beam/erl_db.c
+++ b/erts/emulator/beam/erl_db.c
@@ -2624,7 +2624,7 @@ void init_db(void)
 {
     DbTable init_tb;
     int i;
-    extern UWord* em_apply_bif;
+    extern BeamInstr* em_apply_bif;
     Eterm *hp;
     unsigned bits;
     size_t size;
@@ -2753,9 +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] =
-	(UWord) em_apply_bif;
+	(BeamInstr) em_apply_bif;
     ets_select_delete_continue_exp.code[4] = 
-	(UWord) &ets_select_delete_1;
+	(BeamInstr) &ets_select_delete_1;
 
     /* Non visual BIF to trap to. */
     memset(&ets_select_count_continue_exp, 0, sizeof(Export));
@@ -2765,9 +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] =
-	(UWord) em_apply_bif;
+	(BeamInstr) em_apply_bif;
     ets_select_count_continue_exp.code[4] = 
-	(UWord) &ets_select_count_1;
+	(BeamInstr) &ets_select_count_1;
 
     /* Non visual BIF to trap to. */
     memset(&ets_select_continue_exp, 0, sizeof(Export));
@@ -2777,9 +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] =
-	(UWord) em_apply_bif;
+	(BeamInstr) em_apply_bif;
     ets_select_continue_exp.code[4] = 
-	(UWord) &ets_select_trap_1;
+	(BeamInstr) &ets_select_trap_1;
 
     /* Non visual BIF to trap to. */
     memset(&ets_delete_continue_exp, 0, sizeof(Export));
@@ -2787,8 +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] = (UWord) em_apply_bif;
-    ets_delete_continue_exp.code[4] = (UWord) &ets_delete_trap;
+    ets_delete_continue_exp.code[3] = (BeamInstr) em_apply_bif;
+    ets_delete_continue_exp.code[4] = (BeamInstr) &ets_delete_trap;
 
     hp = ms_delete_all_buff;
     ms_delete_all = CONS(hp, am_true, NIL);
diff --git a/erts/emulator/beam/erl_db_tree.c b/erts/emulator/beam/erl_db_tree.c
index 71c594854b..f9ed5fe292 100644
--- a/erts/emulator/beam/erl_db_tree.c
+++ b/erts/emulator/beam/erl_db_tree.c
@@ -443,9 +443,9 @@ void db_initialize_tree(void)
     ets_select_reverse_exp.code[1] = am_reverse;
     ets_select_reverse_exp.code[2] = 3;
     ets_select_reverse_exp.code[3] =
-	(UWord) em_apply_bif;
+	(BeamInstr) em_apply_bif;
     ets_select_reverse_exp.code[4] = 
-	(UWord) &ets_select_reverse;
+	(BeamInstr) &ets_select_reverse;
     return;
 };
 
diff --git a/erts/emulator/beam/erl_db_util.c b/erts/emulator/beam/erl_db_util.c
index c565e1ee89..f8baf44e10 100644
--- a/erts/emulator/beam/erl_db_util.c
+++ b/erts/emulator/beam/erl_db_util.c
@@ -1601,7 +1601,7 @@ Eterm db_prog_match(Process *c_p, Binary *bprog, Eterm term,
     Eterm **sp;
     Eterm *esp;
     Eterm *hp;
-    UWord *cp;
+    BeamInstr *cp;
     UWord *pc = prog->text;
     Eterm *ehp;
     Eterm ret;
@@ -4235,7 +4235,7 @@ static Eterm match_spec_test(Process *p, Eterm against, Eterm spec, int trace)
     Eterm l;
     Uint32 ret_flags;
     Uint sz;
-    UWord *save_cp;
+    BeamInstr *save_cp;
 
     if (trace && !(is_list(against) || against == NIL)) {
 	return THE_NON_VALUE;
diff --git a/erts/emulator/beam/erl_fun.c b/erts/emulator/beam/erl_fun.c
index e6884c1179..5dea774cd0 100644
--- a/erts/emulator/beam/erl_fun.c
+++ b/erts/emulator/beam/erl_fun.c
@@ -50,8 +50,8 @@ static void fun_free(ErlFunEntry* obj);
  * to unloaded_fun[]. The -1 in unloaded_fun[0] will be interpreted
  * as an illegal arity when attempting to call a fun.
  */
-static UWord unloaded_fun_code[3] = {NIL, -1, 0};
-static UWord* unloaded_fun = unloaded_fun_code + 2;
+static BeamInstr unloaded_fun_code[3] = {NIL, -1, 0};
+static BeamInstr* unloaded_fun = unloaded_fun_code + 2;
 
 void
 erts_init_fun_table(void)
@@ -207,7 +207,7 @@ erts_cleanup_funs(ErlFunThing* funp)
 #endif
 
 void
-erts_cleanup_funs_on_purge(UWord* start, UWord* end)
+erts_cleanup_funs_on_purge(BeamInstr* start, BeamInstr* end)
 {
     int limit;
     HashBucket** bucket;
@@ -222,7 +222,7 @@ erts_cleanup_funs_on_purge(UWord* start, UWord* end)
 
 	while (b) {
 	    ErlFunEntry* fe = (ErlFunEntry *) b;
-	    UWord* addr = fe->address;
+	    BeamInstr* addr = fe->address;
 
 	    if (start <= addr && addr < end) {
 		fe->address = unloaded_fun;
diff --git a/erts/emulator/beam/erl_fun.h b/erts/emulator/beam/erl_fun.h
index 980cdd414a..781e3c764c 100644
--- a/erts/emulator/beam/erl_fun.h
+++ b/erts/emulator/beam/erl_fun.h
@@ -33,7 +33,7 @@ typedef struct erl_fun_entry {
     int index;			/* New style index. */
     int old_uniq;		/* Unique number (old_style) */
     int old_index;		/* Old style index */
-    UWord* address;		/* Pointer to code for fun */
+    BeamInstr* address;		/* Pointer to code for fun */
 
 #ifdef HIPE
     UWord* native_address;	/* Native entry code for fun. */
@@ -86,7 +86,7 @@ void erts_erase_fun_entry(ErlFunEntry* fe);
 #ifndef HYBRID /* FIND ME! */
 void erts_cleanup_funs(ErlFunThing* funp);
 #endif
-void erts_cleanup_funs_on_purge(UWord* start, UWord* end);
+void erts_cleanup_funs_on_purge(BeamInstr* start, BeamInstr* end);
 void erts_dump_fun_entries(int, void *);
 
 #endif
diff --git a/erts/emulator/beam/erl_nif.c b/erts/emulator/beam/erl_nif.c
index 7c62bcb016..f0c4d81f0b 100644
--- a/erts/emulator/beam/erl_nif.c
+++ b/erts/emulator/beam/erl_nif.c
@@ -975,17 +975,17 @@ unsigned enif_sizeof_resource(ErlNifEnv* env, void* obj)
  ***************************************************************************/
 
 
-static UWord** get_func_pp(UWord* mod_code, Eterm f_atom, unsigned arity)
+static BeamInstr** get_func_pp(BeamInstr* mod_code, Eterm f_atom, unsigned arity)
 {
     int n = (int) mod_code[MI_NUM_FUNCTIONS];
     int j;
     for (j = 0; j < n; ++j) {
-	UWord* code_ptr = (UWord*) mod_code[MI_FUNCTIONS+j];
-	ASSERT(code_ptr[0] == (UWord) BeamOp(op_i_func_info_IaaI));
+	BeamInstr* code_ptr = (BeamInstr*) mod_code[MI_FUNCTIONS+j];
+	ASSERT(code_ptr[0] == (BeamInstr) BeamOp(op_i_func_info_IaaI));
 	if (f_atom == ((Eterm) code_ptr[3])
 	    && arity == ((unsigned) code_ptr[4])) {
 
-	    return (UWord**) &mod_code[MI_FUNCTIONS+j];
+	    return (BeamInstr**) &mod_code[MI_FUNCTIONS+j];
 	}
     }
     return NULL;
@@ -1002,7 +1002,7 @@ static UWord** get_func_pp(UWord* mod_code, Eterm f_atom, unsigned arity)
 	
 	erts_atom_get(func->name, sys_strlen(func->name), &f_atom); 
 	code_ptr = *get_func_pp(mod_code, f_atom, func->arity);
-	code_ptr[5+2] = (UWord) mod_nif->priv_data;
+	code_ptr[5+2] = ((BeamInstr) mod_nif->priv_data;
     }
 }*/
 
@@ -1106,7 +1106,7 @@ BIF_RETTYPE load_nif_2(BIF_ALIST_2)
     Module* mod;
     Eterm mod_atom;
     Eterm f_atom;
-    UWord* caller;
+    BeamInstr* caller;
     ErtsSysDdllError errdesc = ERTS_SYS_DDLL_ERROR_INIT;
     Eterm ret = am_ok;
     int veto;
@@ -1173,7 +1173,7 @@ BIF_RETTYPE load_nif_2(BIF_ALIST_2)
 	/*erts_fprintf(stderr, "Found module %T\r\n", mod_atom);*/
     
 	for (i=0; i < entry->num_of_funcs && ret==am_ok; i++) {
-	    UWord** code_pp;
+	    BeamInstr** code_pp;
 	    ErlNifFunc* f = &entry->funcs[i];
 	    if (!erts_atom_get(f->name, sys_strlen(f->name), &f_atom)
 		|| (code_pp = get_func_pp(mod->code, f_atom, f->arity))==NULL) { 
@@ -1291,7 +1291,7 @@ BIF_RETTYPE load_nif_2(BIF_ALIST_2)
 	    code_ptr[5+2] = (BeamInstr) lib;
 	}
     }
-    else {    
+    else {
     error:
 	ASSERT(ret != am_ok);
         if (lib != NULL) {
diff --git a/erts/emulator/beam/erl_process.c b/erts/emulator/beam/erl_process.c
index 429bdd74fb..b12402600b 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 UWord beam_apply[];
-extern UWord beam_exit[];
-extern UWord beam_continue_exit[];
+extern BeamInstr beam_apply[];
+extern BeamInstr beam_exit[];
+extern BeamInstr 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, UWord* x);
+static void print_function_from_pc(int to, void *to_arg, BeamInstr* x);
 static int stack_element_dump(int to, void *to_arg, Process* p, Eterm* sp,
 			      int yreg);
 #ifdef ERTS_SMP
@@ -6769,8 +6769,8 @@ erl_create_process(Process* parent, /* Parent of process (default group leader).
 
     p->current = p->initial+INITIAL_MOD;
 
-    p->i = (UWord *) beam_apply;
-    p->cp = (UWord *) beam_apply+1;
+    p->i = (BeamInstr *) beam_apply;
+    p->cp = (BeamInstr *) 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]);
@@ -7355,7 +7355,7 @@ set_proc_exiting(Process *p, Eterm reason, ErlHeapFragment *bp)
     p->freason = EXTAG_EXIT;
     KILL_CATCHES(p);
     cancel_timer(p);
-    p->i = (UWord *) beam_exit;
+    p->i = (BeamInstr *) beam_exit;
 }
 
 
@@ -8283,7 +8283,7 @@ continue_exit_process(Process *p
 
     ASSERT(p->status == P_EXITING);
 
-    p->i = (UWord *) beam_continue_exit;
+    p->i = (BeamInstr *) beam_continue_exit;
 
     if (!(curr_locks & ERTS_PROC_LOCK_STATUS)) {
 	erts_smp_proc_lock(p, ERTS_PROC_LOCK_STATUS);
@@ -8303,7 +8303,7 @@ continue_exit_process(Process *p
 static void
 timeout_proc(Process* p)
 {
-    p->i = *((UWord **) (UWord) p->def_arg_reg);
+    p->i = *((BeamInstr **) (UWord) p->def_arg_reg);
     p->flags |= F_TIMO;
     p->flags &= ~F_INSLPQUEUE;
 
@@ -8402,9 +8402,9 @@ erts_program_counter_info(int to, void *to_arg, Process *p)
 }
 
 static void
-print_function_from_pc(int to, void *to_arg, UWord* x)
+print_function_from_pc(int to, void *to_arg, BeamInstr* x)
 {
-    UWord* addr = find_function_from_pc(x);
+    BeamInstr* addr = find_function_from_pc(x);
     if (addr == NULL) {
         if (x == beam_exit) {
             erts_print(to, to_arg, "<terminate process>");
@@ -9267,8 +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] = (UWord) em_apply_bif;
-    processes_trap_export.code[4] = (UWord) &processes_trap;
+    processes_trap_export.code[3] = (BeamInstr) em_apply_bif;
+    processes_trap_export.code[4] = (BeamInstr) &processes_trap;
 
 #if ERTS_PROCESSES_BIF_DEBUGLEVEL >= ERTS_PROCS_DBGLVL_CHK_TERM_PROC_LIST
     erts_get_emu_time(&debug_tv_start);
diff --git a/erts/emulator/beam/erl_process.h b/erts/emulator/beam/erl_process.h
index df08f2474c..de9664398d 100644
--- a/erts/emulator/beam/erl_process.h
+++ b/erts/emulator/beam/erl_process.h
@@ -529,8 +529,8 @@ struct process {
     unsigned max_arg_reg;	/* Maximum number of argument registers available. */
     Eterm def_arg_reg[6];	/* Default array for argument registers. */
 
-    UWord* cp;			/* Continuation pointer (for threaded code). */
-    UWord* i;			/* Program counter for threaded code. */
+    BeamInstr* cp;		/* (untagged) Continuation pointer (for threaded code). */
+    BeamInstr* i;		/* Program counter for threaded code. */
     Sint catches;		/* Number of catches on stack */
     Sint fcalls;		/* 
 				 * Number of reductions left to execute.
@@ -577,11 +577,12 @@ struct process {
     Uint seq_trace_lastcnt;
     Eterm seq_trace_token;	/* Sequential trace token (tuple size 5 see below) */
 
-    UWord initial[3];		/* Initial module(0), function(1), arity(2) */
-    UWord* current;		/* Current Erlang function, part of the funcinfo:
+    BeamInstr initial[3];	/* Initial module(0), function(1), arity(2), often used instead
+				   of pointer to funcinfo instruction, hence the BeamInstr datatype */
+    BeamInstr* current;		/* Current Erlang function, part of the funcinfo:
 				 * module(0), function(1), arity(2)
 				 * (module and functions are tagged atoms;
-				 * arity an untagged integer). UWord * because it references code
+				 * arity an untagged integer). BeamInstr * because it references code
 				 */
     
     /*
diff --git a/erts/emulator/beam/erl_process_dump.c b/erts/emulator/beam/erl_process_dump.c
index 0b776367ed..a79612568e 100644
--- a/erts/emulator/beam/erl_process_dump.c
+++ b/erts/emulator/beam/erl_process_dump.c
@@ -45,16 +45,16 @@ static void dump_dist_ext(int to, void *to_arg, ErtsDistExternal *edep);
 static void dump_element_nl(int to, void *to_arg, Eterm x);
 static int stack_element_dump(int to, void *to_arg, Process* p, Eterm* sp,
 			      int yreg);
-static void print_function_from_pc(int to, void *to_arg, UWord* x);
+static void print_function_from_pc(int to, void *to_arg, BeamInstr* x);
 static void heap_dump(int to, void *to_arg, Eterm x);
 static void dump_binaries(int to, void *to_arg, Binary* root);
 static void dump_externally(int to, void *to_arg, Eterm term);
 
 static Binary* all_binaries;
 
-extern UWord beam_apply[];
-extern UWord beam_exit[];
-extern UWord beam_continue_exit[];
+extern BeamInstr beam_apply[];
+extern BeamInstr beam_exit[];
+extern BeamInstr beam_continue_exit[];
 
 
 void
@@ -239,9 +239,9 @@ stack_element_dump(int to, void *to_arg, Process* p, Eterm* sp, int yreg)
 }
 
 static void
-print_function_from_pc(int to, void *to_arg, UWord* x)
+print_function_from_pc(int to, void *to_arg, BeamInstr* x)
 {
-    UWord* addr = find_function_from_pc(x);
+    BeamInstr* addr = find_function_from_pc(x);
     if (addr == NULL) {
         if (x == beam_exit) {
             erts_print(to, to_arg, "<terminate process>");
diff --git a/erts/emulator/beam/erl_term.h b/erts/emulator/beam/erl_term.h
index 8e74502022..25d12bf16e 100644
--- a/erts/emulator/beam/erl_term.h
+++ b/erts/emulator/beam/erl_term.h
@@ -987,14 +987,14 @@ _ET_DECLARE_CHECKED(struct erl_node_*,external_ref_node,Eterm)
 #endif
 
 #define _unchecked_make_cp(x)	((Eterm) COMPRESS_POINTER(x))
-_ET_DECLARE_CHECKED(Eterm,make_cp,UWord*);
+_ET_DECLARE_CHECKED(Eterm,make_cp,BeamInstr*);
 #define make_cp(x)	_ET_APPLY(make_cp,(x))
 
 #define is_not_CP(x)	((x) & _CPMASK)
 #define is_CP(x)	(!is_not_CP(x))
 
-#define _unchecked_cp_val(x)	((UWord*) EXPAND_POINTER(x))
-_ET_DECLARE_CHECKED(UWord*,cp_val,Eterm);
+#define _unchecked_cp_val(x)	((BeamInstr*) EXPAND_POINTER(x))
+_ET_DECLARE_CHECKED(BeamInstr*,cp_val,Eterm);
 #define cp_val(x)	_ET_APPLY(cp_val,(x))
 
 #define make_catch(x)	(((x) << _TAG_IMMED2_SIZE) | _TAG_IMMED2_CATCH)
diff --git a/erts/emulator/beam/erl_trace.c b/erts/emulator/beam/erl_trace.c
index eb61c72e90..8addfcf5ad 100644
--- a/erts/emulator/beam/erl_trace.c
+++ b/erts/emulator/beam/erl_trace.c
@@ -1182,7 +1182,7 @@ seq_trace_output_generic(Eterm token, Eterm msg, Uint type,
  * or   {trace, Pid, return_to, {Mod, Func, Arity}}
  */
 void 
-erts_trace_return_to(Process *p, UWord *pc)
+erts_trace_return_to(Process *p, BeamInstr *pc)
 {
 #define LOCAL_HEAP_SIZE (4+5+5)
     Eterm* hp;
@@ -1190,7 +1190,7 @@ erts_trace_return_to(Process *p, UWord *pc)
     Eterm mess;
     DeclareTmpHeapNoproc(local_heap,LOCAL_HEAP_SIZE);
 
-    UWord *code_ptr = find_function_from_pc(pc);
+    BeamInstr *code_ptr = find_function_from_pc(pc);
 
 
     UseTmpHeapNoproc(LOCAL_HEAP_SIZE);
@@ -1249,7 +1249,7 @@ erts_trace_return_to(Process *p, UWord *pc)
  * or   {trace, Pid, return_from, {Mod, Name, Arity}, Retval}
  */
 void
-erts_trace_return(Process* p, UWord* fi, Eterm retval, Eterm *tracer_pid)
+erts_trace_return(Process* p, BeamInstr* fi, Eterm retval, Eterm *tracer_pid)
 {
     Eterm* hp;
     Eterm mfa;
@@ -1380,7 +1380,7 @@ erts_trace_return(Process* p, UWord* fi, Eterm retval, Eterm *tracer_pid)
  * Where Class is atomic but Value is any term.
  */
 void
-erts_trace_exception(Process* p, UWord mfa[3], Eterm class, Eterm value,
+erts_trace_exception(Process* p, BeamInstr mfa[3], Eterm class, Eterm value,
 		     Eterm *tracer_pid)
 {
     Eterm* hp;
@@ -1522,7 +1522,7 @@ erts_trace_exception(Process* p, UWord mfa[3], Eterm class, Eterm value,
  * if it is a pid or port we do a meta trace.
  */
 Uint32
-erts_call_trace(Process* p, UWord mfa[3], Binary *match_spec,
+erts_call_trace(Process* p, BeamInstr mfa[3], Binary *match_spec,
 		Eterm* args, int local, Eterm *tracer_pid)
 {
     Eterm* hp;
@@ -2092,7 +2092,7 @@ void save_calls(Process *p, Export *e)
  */
 Eterm
 erts_bif_trace(int bif_index, Process* p, 
-	       Eterm arg1, Eterm arg2, Eterm arg3, UWord *I)
+	       Eterm arg1, Eterm arg2, Eterm arg3, BeamInstr *I)
 {
     Eterm result;
     int meta = !!(erts_bif_trace_flags[bif_index] & BIF_TRACE_AS_META);
@@ -2106,10 +2106,10 @@ erts_bif_trace(int bif_index, Process* p,
 	 * no tracing will occur. Doing the whole else branch will 
 	 * also do nothing, only slower.
 	 */
-	Eterm (*func)(Process*, Eterm, Eterm, Eterm, UWord*) = bif_table[bif_index].f;
+	Eterm (*func)(Process*, Eterm, Eterm, Eterm, BeamInstr*) = bif_table[bif_index].f;
 	result = func(p, arg1, arg2, arg3, I);
     } else {
-	Eterm (*func)(Process*, Eterm, Eterm, Eterm, UWord*);
+	Eterm (*func)(Process*, Eterm, Eterm, Eterm, BeamInstr*);
 	Export* ep = bif_export[bif_index];
 	Uint32 flags = 0, flags_meta = 0;
 	int global = !!(erts_bif_trace_flags[bif_index] & BIF_TRACE_AS_GLOBAL);
@@ -2118,7 +2118,7 @@ erts_bif_trace(int bif_index, Process* p,
 	int applying = (I == &(ep->code[3])); /* Yup, the apply code for a bif
 					       * is actually in the 
 					       * export entry */
-	UWord *cp = p->cp;
+	BeamInstr *cp = p->cp;
 	
 	Eterm args[3] = {arg1, arg2, arg3};
 	
diff --git a/erts/emulator/beam/erl_unicode.c b/erts/emulator/beam/erl_unicode.c
index 8f16f7338f..ca800dbe8d 100644
--- a/erts/emulator/beam/erl_unicode.c
+++ b/erts/emulator/beam/erl_unicode.c
@@ -90,9 +90,9 @@ void erts_init_unicode(void)
 	am_atom_put("characters_to_utf8_trap",23);
     characters_to_utf8_trap_exp.code[2] = 3;
     characters_to_utf8_trap_exp.code[3] =
-	(UWord) em_apply_bif;
+	(BeamInstr) em_apply_bif;
     characters_to_utf8_trap_exp.code[4] = 
-	(UWord) &characters_to_utf8_trap;
+	(BeamInstr) &characters_to_utf8_trap;
 
     memset(&characters_to_list_trap_1_exp, 0, sizeof(Export));
     characters_to_list_trap_1_exp.address = 
@@ -102,9 +102,9 @@ void erts_init_unicode(void)
 	am_atom_put("characters_to_list_trap_1",25);
     characters_to_list_trap_1_exp.code[2] = 3;
     characters_to_list_trap_1_exp.code[3] =
-	(UWord) em_apply_bif;
+	(BeamInstr) em_apply_bif;
     characters_to_list_trap_1_exp.code[4] = 
-	(UWord) &characters_to_list_trap_1;
+	(BeamInstr) &characters_to_list_trap_1;
 
     memset(&characters_to_list_trap_2_exp, 0, sizeof(Export));
     characters_to_list_trap_2_exp.address = 
@@ -114,9 +114,9 @@ void erts_init_unicode(void)
 	am_atom_put("characters_to_list_trap_2",25);
     characters_to_list_trap_2_exp.code[2] = 3;
     characters_to_list_trap_2_exp.code[3] =
-	(UWord) em_apply_bif;
+	(BeamInstr) em_apply_bif;
     characters_to_list_trap_2_exp.code[4] = 
-	(UWord) &characters_to_list_trap_2;
+	(BeamInstr) &characters_to_list_trap_2;
 
 
     memset(&characters_to_list_trap_3_exp, 0, sizeof(Export));
@@ -127,9 +127,9 @@ void erts_init_unicode(void)
 	am_atom_put("characters_to_list_trap_3",25);
     characters_to_list_trap_3_exp.code[2] = 3;
     characters_to_list_trap_3_exp.code[3] =
-	(UWord) em_apply_bif;
+	(BeamInstr) em_apply_bif;
     characters_to_list_trap_3_exp.code[4] = 
-	(UWord) &characters_to_list_trap_3;
+	(BeamInstr) &characters_to_list_trap_3;
 
     memset(&characters_to_list_trap_4_exp, 0, sizeof(Export));
     characters_to_list_trap_4_exp.address = 
@@ -139,9 +139,9 @@ void erts_init_unicode(void)
 	am_atom_put("characters_to_list_trap_4",25);
     characters_to_list_trap_4_exp.code[2] = 1;
     characters_to_list_trap_4_exp.code[3] =
-	(UWord) em_apply_bif;
+	(BeamInstr) em_apply_bif;
     characters_to_list_trap_4_exp.code[4] = 
-	(UWord) &characters_to_list_trap_4;
+	(BeamInstr) &characters_to_list_trap_4;
 
     c_to_b_int_trap_exportp =  erts_export_put(am_unicode,am_characters_to_binary_int,2);
     c_to_l_int_trap_exportp =  erts_export_put(am_unicode,am_characters_to_list_int,2);
diff --git a/erts/emulator/beam/error.h b/erts/emulator/beam/error.h
index 8f95140864..bbccb5e529 100644
--- a/erts/emulator/beam/error.h
+++ b/erts/emulator/beam/error.h
@@ -187,10 +187,10 @@ extern Eterm exception_tag[NUMBER_EXC_TAGS];
 struct StackTrace {
     Eterm header;	/* bignum header - must be first in struct */
     Eterm freason; /* original exception reason is saved in the struct */
-    UWord* pc;
-    UWord* current;
+    BeamInstr* pc;
+    BeamInstr* current;
     int depth;	/* number of saved pointers in trace[] */
-    UWord *trace[1];  /* varying size - must be last in struct */
+    BeamInstr *trace[1];  /* varying size - must be last in struct */
 };
 
 #endif /* __ERROR_H__ */
diff --git a/erts/emulator/beam/export.c b/erts/emulator/beam/export.c
index c39f610924..d251a0e375 100644
--- a/erts/emulator/beam/export.c
+++ b/erts/emulator/beam/export.c
@@ -46,8 +46,8 @@ static erts_smp_rwmtx_t export_table_lock; /* Locks the secondary export table.
 #define export_init_lock()	erts_smp_rwmtx_init(&export_table_lock, \
 						    "export_tab")
 
-extern UWord* em_call_error_handler;
-extern UWord* em_call_traced_function;
+extern BeamInstr* em_call_error_handler;
+extern BeamInstr* em_call_traced_function;
 
 void
 export_info(int to, void *to_arg)
@@ -93,7 +93,7 @@ export_alloc(Export* tmpl)
     obj->code[2] = tmpl->code[2];
     obj->slot.index = -1;
     obj->address = obj->code+3;
-    obj->code[3] = (UWord) em_call_error_handler;
+    obj->code[3] = (BeamInstr) em_call_error_handler;
     obj->code[4] = 0;
     obj->match_prog_set = NULL;
     return obj;
@@ -140,7 +140,7 @@ init_export_table(void)
 Export*
 erts_find_export_entry(Eterm m, Eterm f, unsigned int a)
 {
-    HashValue hval = EXPORT_HASH((UWord) m, (UWord) f, (UWord) a);
+    HashValue hval = EXPORT_HASH((BeamInstr) m, (BeamInstr) f, (BeamInstr) a);
     int ix;
     HashBucket* b;
 
@@ -185,7 +185,7 @@ erts_find_function(Eterm m, Eterm f, unsigned int a)
 
     ep = hash_get(&export_table.htable, (void*) &e);
     if (ep != NULL && ep->address == ep->code+3 &&
-	ep->code[3] != (UWord) em_call_traced_function) {
+	ep->code[3] != (BeamInstr) em_call_traced_function) {
 	ep = NULL;
     }
     return ep;
diff --git a/erts/emulator/beam/export.h b/erts/emulator/beam/export.h
index 57b6a7afcf..2758d71a3c 100644
--- a/erts/emulator/beam/export.h
+++ b/erts/emulator/beam/export.h
@@ -53,7 +53,7 @@ typedef struct export
      *		Otherwise: 0.
      */
 #if HALFWORD_HEAP
-    UWord code[5];
+    BeamInstr code[5];
 #else
     Eterm code[5];
 #endif
@@ -78,6 +78,6 @@ Export *export_get(Export*);
 #include "beam_load.h" /* For em_* extern declarations */ 
 #define ExportIsBuiltIn(EntryPtr) 			\
 (((EntryPtr)->address == (EntryPtr)->code + 3) && 	\
- ((EntryPtr)->code[3] == (UWord) em_apply_bif))
+ ((EntryPtr)->code[3] == (BeamInstr) em_apply_bif))
 
 #endif
diff --git a/erts/emulator/beam/global.h b/erts/emulator/beam/global.h
index ebe7302373..cefdf80fb4 100644
--- a/erts/emulator/beam/global.h
+++ b/erts/emulator/beam/global.h
@@ -856,7 +856,7 @@ void erts_system_profile_clear(Process *c_p);
 int erts_load_module(Process *c_p, ErtsProcLocks c_p_locks,
 		     Eterm group_leader, Eterm* mod, byte* code, int size);
 void init_load(void);
-UWord* find_function_from_pc(UWord* pc);
+BeamInstr* find_function_from_pc(BeamInstr* pc);
 Eterm erts_module_info_0(Process* p, Eterm module);
 Eterm erts_module_info_1(Process* p, Eterm module, Eterm what);
 Eterm erts_make_stub_module(Process* p, Eterm Mod, Eterm Beam, Eterm Info);
@@ -1611,12 +1611,12 @@ void erts_queue_error_logger_message(Eterm, Eterm, ErlHeapFragment *);
 void erts_send_sys_msg_proc(Eterm, Eterm, Eterm, ErlHeapFragment *);
 void trace_send(Process*, Eterm, Eterm);
 void trace_receive(Process*, Eterm);
-Uint32 erts_call_trace(Process *p, UWord mfa[], Binary *match_spec, Eterm* args,
+Uint32 erts_call_trace(Process *p, BeamInstr mfa[], Binary *match_spec, Eterm* args,
 		       int local, Eterm *tracer_pid);
-void erts_trace_return(Process* p, UWord* fi, Eterm retval, Eterm *tracer_pid);
-void erts_trace_exception(Process* p, UWord mfa[], Eterm class, Eterm value,
+void erts_trace_return(Process* p, BeamInstr* fi, Eterm retval, Eterm *tracer_pid);
+void erts_trace_exception(Process* p, BeamInstr mfa[], Eterm class, Eterm value,
 			  Eterm *tracer);
-void erts_trace_return_to(Process *p, UWord *pc);
+void erts_trace_return_to(Process *p, BeamInstr *pc);
 void trace_sched(Process*, Eterm);
 void trace_proc(Process*, Process*, Eterm, Eterm);
 void trace_proc_spawn(Process*, Eterm pid, Eterm mod, Eterm func, Eterm args);
@@ -1646,7 +1646,7 @@ Uint erts_trace_flag2bit(Eterm flag);
 int erts_trace_flags(Eterm List, 
 		 Uint *pMask, Eterm *pTracer, int *pCpuTimestamp);
 Eterm erts_bif_trace(int bif_index, Process* p, 
-		     Eterm arg1, Eterm arg2, Eterm arg3, UWord *I);
+		     Eterm arg1, Eterm arg2, Eterm arg3, BeamInstr *I);
 
 #ifdef ERTS_SMP
 void erts_send_pending_trace_msgs(ErtsSchedulerData *esdp);
diff --git a/erts/emulator/beam/module.h b/erts/emulator/beam/module.h
index a09d5985db..694e4ab72f 100644
--- a/erts/emulator/beam/module.h
+++ b/erts/emulator/beam/module.h
@@ -29,8 +29,8 @@ typedef struct erl_module {
     IndexSlot slot;		/* Must be located at top of struct! */
     int module;			/* Atom index for module (not tagged). */
 
-    UWord* code;
-    UWord* old_code;
+    BeamInstr* code;
+    BeamInstr* old_code;
     int code_length;		/* Length of loaded code in bytes. */
     int old_code_length;	/* Length of old loaded code in bytes */
     unsigned catches, old_catches;
diff --git a/erts/emulator/beam/sys.h b/erts/emulator/beam/sys.h
index b48b147953..7ddf1d8278 100644
--- a/erts/emulator/beam/sys.h
+++ b/erts/emulator/beam/sys.h
@@ -231,6 +231,7 @@ EXTERN_FUNCTION(int, real_printf, (const char *fmt, ...));
 ** Data types:
 **
 ** Eterm: A tagged erlang term (possibly 64 bits)
+** BeamInstr: A beam code instruction unit, possibly larger than Eterm, not smaller.
 ** UInt:  An unsigned integer exactly as large as an Eterm.
 ** SInt:  A signed integer exactly as large as an eterm and therefor large
 **        enough to hold the return value of the signed_val() macro.
@@ -314,6 +315,8 @@ typedef Sint SWord;
 
 #endif /* HALFWORD_HEAP */
 
+typedef UWord BeamInstr;
+
 #ifndef HAVE_INT64
 #if SIZEOF_LONG == 8
 #define HAVE_INT64 1