Store pointers to heap data in 32-bit words

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

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

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

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

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

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

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

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

1 files changed, 23 insertions, 22 deletions

diff --git a/erts/emulator/beam/erl_term.h b/erts/emulator/beam/erl_term.h
index 016d6e66a7..8e74502022 100644
--- a/erts/emulator/beam/erl_term.h
+++ b/erts/emulator/beam/erl_term.h
@@ -20,10 +20,7 @@
 #ifndef __ERL_TERM_H
 #define __ERL_TERM_H
 
-#ifdef ARCH_64
-#define HALFWORD_HEAP 1
-#define HALFWORD_ASSERT 1
-#endif
+#include "sys.h" /* defines HALFWORD_HEAP */
 
 #if HALFWORD_HEAP
 #  define HEAP_ON_C_STACK 0
@@ -35,8 +32,8 @@
 #  endif
 #  if 1
 #    define CHECK_POINTER_MASK 0xFFFFFFFF00000000UL
-#    define COMPRESS_POINTER(AnUint) (AnUint)
-#    define EXPAND_POINTER(APointer) (APointer)
+#    define COMPRESS_POINTER(APointer) ((Eterm) (UWord) (APointer))
+#    define EXPAND_POINTER(AnEterm) ((UWord) (AnEterm))
 #  else
 #    define CHECK_POINTER_MASK 0x0UL
 #    define COMPRESS_POINTER(AnUint) (AnUint)
@@ -188,14 +185,14 @@ struct erl_node_; /* Declared in erl_node_tables.h */
 
 /* boxed object access methods */
 #if HALFWORD_HEAP
-#define _is_taggable_pointer(x)	 (((Uint)(x) & (CHECK_POINTER_MASK | 0x3)) == 0)
+#define _is_taggable_pointer(x)	 (((UWord)(x) & (CHECK_POINTER_MASK | 0x3)) == 0)
 #define _boxed_precond(x)        (is_boxed(x))
 #else
 #define _is_taggable_pointer(x)	 (((Uint)(x) & 0x3) == 0)
 #define  _boxed_precond(x)       (is_boxed(x))
 #endif
 #define _is_aligned(x)		(((Uint)(x) & 0x3) == 0)
-#define _unchecked_make_boxed(x) COMPRESS_POINTER((Uint)(x) + TAG_PRIMARY_BOXED)
+#define _unchecked_make_boxed(x) ((Uint) COMPRESS_POINTER(x) + TAG_PRIMARY_BOXED)
 _ET_DECLARE_CHECKED(Eterm,make_boxed,Eterm*);
 #define make_boxed(x)		_ET_APPLY(make_boxed,(x))
 #if 1
@@ -206,12 +203,12 @@ _ET_DECLARE_CHECKED(int,is_boxed,Eterm)
 #else
 #define is_boxed(x)		(((x) & _TAG_PRIMARY_MASK) == TAG_PRIMARY_BOXED)
 #endif
-#define _unchecked_boxed_val(x) EXPAND_POINTER((Eterm*)((x) - TAG_PRIMARY_BOXED))
+#define _unchecked_boxed_val(x) ((Eterm*) EXPAND_POINTER(((x) - TAG_PRIMARY_BOXED)))
 _ET_DECLARE_CHECKED(Eterm*,boxed_val,Eterm);
 #define boxed_val(x)		_ET_APPLY(boxed_val,(x))
 
 /* cons cell ("list") access methods */
-#define _unchecked_make_list(x)	COMPRESS_POINTER((Uint)(x) + TAG_PRIMARY_LIST)
+#define _unchecked_make_list(x)	((Uint) COMPRESS_POINTER(x) + TAG_PRIMARY_LIST)
 _ET_DECLARE_CHECKED(Eterm,make_list,Eterm*);
 #define make_list(x)		_ET_APPLY(make_list,(x))
 #if 1
@@ -228,7 +225,7 @@ _ET_DECLARE_CHECKED(int,is_not_list,Eterm)
 #else
 #define _list_precond(x)       (is_list(x))
 #endif
-#define _unchecked_list_val(x)	EXPAND_POINTER((Eterm*)((x) - TAG_PRIMARY_LIST))
+#define _unchecked_list_val(x) ((Eterm*) EXPAND_POINTER((x) - TAG_PRIMARY_LIST))
 _ET_DECLARE_CHECKED(Eterm*,list_val,Eterm);
 #define list_val(x)		_ET_APPLY(list_val,(x))
 
@@ -239,13 +236,13 @@ _ET_DECLARE_CHECKED(Eterm*,list_val,Eterm);
 #define CDR(x)  ((x)[1])
 
 /* generic tagged pointer (boxed or list) access methods */
-#define _unchecked_ptr_val(x)	EXPAND_POINTER((Eterm*)((x) & ~((Uint) 0x3)))
+#define _unchecked_ptr_val(x)	((Eterm*) EXPAND_POINTER((x) & ~((Uint) 0x3)))
 #define ptr_val(x)		_unchecked_ptr_val((x))	/*XXX*/
 #define _unchecked_offset_ptr(x,offs)	((x)+((offs)*sizeof(Eterm)))
 #define offset_ptr(x,offs)	_unchecked_offset_ptr(x,offs)	/*XXX*/
 
 /* fixnum ("small") access methods */
-#if defined(ARCH_64)
+#if defined(ARCH_64) && !HALFWORD_HEAP
 #define SMALL_BITS	(64-4)
 #define SMALL_DIGITS	(17)
 #else
@@ -370,7 +367,11 @@ _ET_DECLARE_CHECKED(Eterm*,fun_val,Eterm)
 _ET_DECLARE_CHECKED(Eterm*,export_val,Eterm)
 #define export_val(x)	_ET_APPLY(export_val,(x))
 #define is_export_header(x)	((x) == HEADER_EXPORT)
+#if HALFWORD_HEAP
+#define HEADER_EXPORT   _make_header(2,_TAG_HEADER_EXPORT)
+#else
 #define HEADER_EXPORT   _make_header(1,_TAG_HEADER_EXPORT)
+#endif
 
 /* bignum access methods */
 #define make_pos_bignum_header(sz)	_make_header((sz),_TAG_HEADER_POS_BIG)
@@ -394,7 +395,7 @@ _ET_DECLARE_CHECKED(Eterm*,big_val,Eterm)
 #define big_val(x)		_ET_APPLY(big_val,(x))
 
 /* flonum ("float") access methods */
-#ifdef ARCH_64
+#if defined(ARCH_64) && !HALFWORD_HEAP
 #define HEADER_FLONUM   _make_header(1,_TAG_HEADER_FLOAT)
 #else
 #define HEADER_FLONUM	_make_header(2,_TAG_HEADER_FLOAT)
@@ -415,12 +416,12 @@ typedef union float_def
     byte   fb[sizeof(ieee754_8)];
     Uint16 fs[sizeof(ieee754_8) / sizeof(Uint16)];
     Uint32 fw[sizeof(ieee754_8) / sizeof(Uint32)];
-#ifdef ARCH_64
+#if defined(ARCH_64) && !HALFWORD_HEAP
     Uint   fdw;
 #endif
 } FloatDef;
 
-#ifdef ARCH_64
+#if defined(ARCH_64) && !HALFWORD_HEAP
 #define GET_DOUBLE(x, f) (f).fdw = *(float_val(x)+1)
 
 #define PUT_DOUBLE(f, x)  *(x) = HEADER_FLONUM, \
@@ -720,7 +721,7 @@ _ET_DECLARE_CHECKED(struct erl_node_*,internal_port_node,Eterm)
 #define ERTS_MAX_REF_NUMBERS	3
 #define ERTS_REF_NUMBERS	ERTS_MAX_REF_NUMBERS
 
-#ifdef ARCH_64
+#if defined(ARCH_64) && !HALFWORD_HEAP
 #  define ERTS_REF_WORDS	(ERTS_REF_NUMBERS/2 + 1)
 #  define ERTS_REF_32BIT_WORDS  (ERTS_REF_NUMBERS+1)
 #else
@@ -742,7 +743,7 @@ typedef struct {
 #define make_ref_thing_header(DW) \
   _make_header((DW)+REF_THING_HEAD_SIZE-1,_TAG_HEADER_REF)
 
-#ifdef ARCH_64
+#if defined(ARCH_64) && !HALFWORD_HEAP
 
 /*
  * Ref layout on a 64-bit little endian machine:
@@ -985,15 +986,15 @@ _ET_DECLARE_CHECKED(struct erl_node_*,external_ref_node,Eterm)
 #error "fix yer arch, like"
 #endif
 
-#define _unchecked_make_cp(x)	((Eterm)(x))
-_ET_DECLARE_CHECKED(Eterm,make_cp,Uint*)
+#define _unchecked_make_cp(x)	((Eterm) COMPRESS_POINTER(x))
+_ET_DECLARE_CHECKED(Eterm,make_cp,UWord*);
 #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)	((Uint*)(x))
-_ET_DECLARE_CHECKED(Uint*,cp_val,Eterm)
+#define _unchecked_cp_val(x)	((UWord*) EXPAND_POINTER(x))
+_ET_DECLARE_CHECKED(UWord*,cp_val,Eterm);
 #define cp_val(x)	_ET_APPLY(cp_val,(x))
 
 #define make_catch(x)	(((x) << _TAG_IMMED2_SIZE) | _TAG_IMMED2_CATCH)