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increase range of relative jumps by aligning blocks to 8-byte boundaries

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* libguile/objcodes.c (OBJCODE_COOKIE): Bump again, as our jump offsets
  are now multiplied by 8.

* libguile/vm-i-system.c (BR): Interpret the 16-bit offset as a relative
  jump to the nearest 8-byte-aligned block -- increasing relative jump
  range from +/-32K to +/-240K.
  (mvra): Do the same for the mvra jump.

* libguile/vm.c (really_make_boot_program): Align the mvra.

* module/language/assembly.scm (align-block): New export, for aligning
  blocks.

* module/language/assembly/compile-bytecode.scm (write-bytecode): Emit
  jumps to the nearest 8-byte-aligned block. Effectively our range is 18
  bits in either direction. I would like to do this differently -- have
  long-br and long-br-if, and all the other br instructions go to 8 bits
  only. But the assembler doesn't have an appropriate representation to
  allow me to do this yet, so for now this is what we have.

* module/language/assembly/decompile-bytecode.scm (decode-load-program):
  Decode the 19-bit jumps.
This commit is contained in:
Andy Wingo 2009-07-26 14:01:56 +02:00
parent 28b119ee3d
commit e5dc27b86d
7 changed files with 39 additions and 26 deletions
Download patch file Download diff file Expand all files Collapse all files

2
libguile/objcodes.c
View file

@ -50,7 +50,7 @@
/* The objcode magic header. */
#define OBJCODE_COOKIE \
"GOOF-0.8-" OBJCODE_ENDIANNESS "-" OBJCODE_WORD_SIZE "---"
"GOOF-0.9-" OBJCODE_ENDIANNESS "-" OBJCODE_WORD_SIZE "---"
/* The length of the header must be a multiple of 8 bytes. */
verify (((sizeof (OBJCODE_COOKIE) - 1) & 7) == 0);

20
libguile/vm-i-system.c
View file

@ -426,7 +426,7 @@ VM_DEFINE_INSTRUCTION (34, long_toplevel_set, "long-toplevel-set", 2, 1, 0)
* branch and jump
*/
/* offset must be a signed short!!! */
/* offset must be a signed 16 bit int!!! */
#define FETCH_OFFSET(offset) \
{ \
int h = FETCH (); \
@ -436,10 +436,10 @@ VM_DEFINE_INSTRUCTION (34, long_toplevel_set, "long-toplevel-set", 2, 1, 0)
#define BR(p) \
{ \
signed short offset; \
scm_t_int16 offset; \
FETCH_OFFSET (offset); \
if (p) \
ip += offset; \
ip += ((scm_t_ptrdiff)offset) * 8 - (((unsigned long)ip) % 8); \
NULLSTACK (1); \
DROP (); \
NEXT; \
@ -447,9 +447,9 @@ VM_DEFINE_INSTRUCTION (34, long_toplevel_set, "long-toplevel-set", 2, 1, 0)
VM_DEFINE_INSTRUCTION (35, br, "br", 2, 0, 0)
{
int h = FETCH ();
int l = FETCH ();
ip += (signed short) (h << 8) + l;
scm_t_int16 offset;
FETCH_OFFSET (offset);
ip += ((scm_t_ptrdiff)offset) * 8 - (((unsigned long)ip) % 8);
NEXT;
}
@ -812,10 +812,12 @@ VM_DEFINE_INSTRUCTION (46, call_nargs, "call/nargs", 0, 0, 1)
VM_DEFINE_INSTRUCTION (47, mv_call, "mv-call", 3, -1, 1)
{
SCM x;
signed short offset;
scm_t_int16 offset;
scm_t_uint8 *mvra;
nargs = FETCH ();
FETCH_OFFSET (offset);
mvra = ip + ((scm_t_ptrdiff)offset) * 8 - ((unsigned long)ip) % 8;
x = sp[-nargs];
@ -828,7 +830,7 @@ VM_DEFINE_INSTRUCTION (47, mv_call, "mv-call", 3, -1, 1)
CACHE_PROGRAM ();
INIT_ARGS ();
NEW_FRAME ();
SCM_FRAME_DATA_ADDRESS (fp)[1] = (SCM)(SCM_FRAME_RETURN_ADDRESS (fp) + offset);
SCM_FRAME_DATA_ADDRESS (fp)[1] = (SCM)mvra;
ENTER_HOOK ();
APPLY_HOOK ();
NEXT;
@ -853,7 +855,7 @@ VM_DEFINE_INSTRUCTION (47, mv_call, "mv-call", 3, -1, 1)
len = scm_length (values);
PUSH_LIST (values, SCM_NULLP);
PUSH (len);
ip += offset;
ip = mvra;
}
NEXT;
}

2
libguile/vm.c
View file

@ -226,7 +226,7 @@ really_make_boot_program (long nargs)
SCM u8vec;
/* Make sure "bytes" is 64-bit aligned. */
scm_t_uint8 text[] = { scm_op_mv_call, 0, 0, 1,
scm_op_make_int8_1,
scm_op_make_int8_1, scm_op_nop, scm_op_nop, scm_op_nop,
scm_op_halt };
struct scm_objcode *bp;
SCM ret;

17
module/language/assembly.scm
View file

@ -24,7 +24,7 @@
#:use-module (system vm instruction)
#:use-module ((srfi srfi-1) #:select (fold))
#:export (byte-length
addr+ align-program align-code
addr+ align-program align-code align-block
assembly-pack assembly-unpack
object->assembly assembly->object))
@ -63,17 +63,24 @@
(define *program-alignment* 8)
(define *block-alignment* 8)
(define (addr+ addr code)
(fold (lambda (x len) (+ (byte-length x) len))
addr
code))
(define (code-alignment addr alignment header-len)
(make-list (modulo (- alignment
(modulo (+ addr header-len) alignment))
alignment)
'(nop)))
(define (align-block addr)
(code-alignment addr *block-alignment* 0))
(define (align-code code addr alignment header-len)
`(,@(make-list (modulo (- alignment
(modulo (+ addr header-len) alignment))
alignment)
'(nop))
`(,@(code-alignment addr alignment header-len)
,code))
(define (align-program prog addr)

10
module/language/assembly/compile-bytecode.scm
View file

@ -77,10 +77,12 @@
;; Ew!
(for-each write-byte (bytevector->u8-list bv)))
(define (write-break label)
(let ((offset (- (assq-ref labels label) (+ (get-addr) 2))))
(cond ((>= offset (ash 1 15)) (error "jump too big" offset))
((< offset (- (ash 1 15))) (error "reverse jump too big" offset))
(else (write-uint16-be offset)))))
(let ((offset (- (assq-ref labels label)
(logand (+ (get-addr) 2) (lognot #x7)))))
(cond ((not (= 0 (modulo offset 8))) (error "unaligned jump" offset))
((>= offset (ash 1 18)) (error "jump too far forward" offset))
((< offset (- (ash 1 18))) (error "jump too far backwards" offset))
(else (write-uint16-be (ash offset -3))))))
(let ((inst (car asm))
(args (cdr asm))

3
module/language/assembly/decompile-bytecode.scm
View file

@ -61,7 +61,8 @@
(labels '())
(i 0))
(define (ensure-label rel1 rel2)
(let ((where (+ i (bytes->s16 rel1 rel2))))
(let ((where (+ (logand i (lognot #x7))
(* (bytes->s16 rel1 rel2) 8))))
(or (assv-ref labels where)
(begin
(let ((l (gensym ":L")))

11
module/language/glil/compile-assembly.scm
View file

@ -340,11 +340,12 @@
(error "unknown module var kind" op key)))))
((<glil-label> label)
(values '()
bindings
source-alist
(acons label addr label-alist)
object-alist))
(let ((code (align-block addr)))
(values code
bindings
source-alist
(acons label (addr+ addr code) label-alist)
object-alist)))
((<glil-branch> inst label)
(emit-code `((,inst ,label))))