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jumps encoded using 24 bits, not 19; blocks no longer aligned

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* libguile/_scm.h (SCM_OBJCODE_MINOR_VERSION): Bump.
* libguile/vm-i-system.c (FETCH_OFFSET, BR): Labels are no longer 8-byte
  aligned; instead, jumps are encoded into 3 bytes instead of 2.
  (br, br-if, br-if-not, br-if-eq, br-if-not-eq, br-if-null)
  (br-if-not-null, mv-call): Adapt for new length of br instructions (3
  bytes instead of 2).

* libguile/vm.c (really_make_boot_program): Adapt hand-coded bytecode
  for new offset regime.

* module/language/assembly.scm (align-block): No alignment necessary.

* module/language/assembly/compile-bytecode.scm (write-bytecode): Write
  out breaks as 24-bit relative jumps.
* module/language/assembly/decompile-bytecode.scm (decode-load-program):
  Decompile break instructions.
This commit is contained in:
Andy Wingo 2009-09-17 14:58:31 +02:00
parent f95f82f8e1
commit 97fcf583b7
6 changed files with 40 additions and 39 deletions
Download patch file Download diff file Expand all files Collapse all files

2
libguile/_scm.h
View file

@ -172,7 +172,7 @@
/* Major and minor versions must be single characters. */
#define SCM_OBJCODE_MAJOR_VERSION 0
#define SCM_OBJCODE_MINOR_VERSION D
#define SCM_OBJCODE_MINOR_VERSION E
#define SCM_OBJCODE_MAJOR_VERSION_STRING \
SCM_CPP_STRINGIFY(SCM_OBJCODE_MAJOR_VERSION)
#define SCM_OBJCODE_MINOR_VERSION_STRING \

37
libguile/vm-i-system.c
View file

@ -411,61 +411,62 @@ VM_DEFINE_INSTRUCTION (30, long_toplevel_set, "long-toplevel-set", 2, 1, 0)
* branch and jump
*/
/* offset must be a signed 16 bit int!!! */
/* offset must be at least 24 bits wide, and signed */
#define FETCH_OFFSET(offset) \
{ \
int h = FETCH (); \
int l = FETCH (); \
offset = (h << 8) + l; \
offset = FETCH () << 16; \
offset += FETCH () << 8; \
offset += FETCH (); \
offset -= (offset & (1<<23)) << 1; \
}
#define BR(p) \
{ \
scm_t_int16 offset; \
scm_t_int32 offset; \
FETCH_OFFSET (offset); \
if (p) \
ip += ((scm_t_ptrdiff)offset) * 8 - (((unsigned long)ip) % 8); \
ip += offset; \
NULLSTACK (1); \
DROP (); \
NEXT; \
}
VM_DEFINE_INSTRUCTION (31, br, "br", 2, 0, 0)
VM_DEFINE_INSTRUCTION (31, br, "br", 3, 0, 0)
{
scm_t_int16 offset;
scm_t_int32 offset;
FETCH_OFFSET (offset);
ip += ((scm_t_ptrdiff)offset) * 8 - (((unsigned long)ip) % 8);
ip += offset;
NEXT;
}
VM_DEFINE_INSTRUCTION (32, br_if, "br-if", 2, 0, 0)
VM_DEFINE_INSTRUCTION (32, br_if, "br-if", 3, 0, 0)
{
BR (!SCM_FALSEP (*sp));
}
VM_DEFINE_INSTRUCTION (33, br_if_not, "br-if-not", 2, 0, 0)
VM_DEFINE_INSTRUCTION (33, br_if_not, "br-if-not", 3, 0, 0)
{
BR (SCM_FALSEP (*sp));
}
VM_DEFINE_INSTRUCTION (34, br_if_eq, "br-if-eq", 2, 0, 0)
VM_DEFINE_INSTRUCTION (34, br_if_eq, "br-if-eq", 3, 0, 0)
{
sp--; /* underflow? */
BR (SCM_EQ_P (sp[0], sp[1]));
}
VM_DEFINE_INSTRUCTION (35, br_if_not_eq, "br-if-not-eq", 2, 0, 0)
VM_DEFINE_INSTRUCTION (35, br_if_not_eq, "br-if-not-eq", 3, 0, 0)
{
sp--; /* underflow? */
BR (!SCM_EQ_P (sp[0], sp[1]));
}
VM_DEFINE_INSTRUCTION (36, br_if_null, "br-if-null", 2, 0, 0)
VM_DEFINE_INSTRUCTION (36, br_if_null, "br-if-null", 3, 0, 0)
{
BR (SCM_NULLP (*sp));
}
VM_DEFINE_INSTRUCTION (37, br_if_not_null, "br-if-not-null", 2, 0, 0)
VM_DEFINE_INSTRUCTION (37, br_if_not_null, "br-if-not-null", 3, 0, 0)
{
BR (!SCM_NULLP (*sp));
}
@ -642,15 +643,15 @@ VM_DEFINE_INSTRUCTION (42, call_nargs, "call/nargs", 0, 0, 1)
goto vm_call;
}
VM_DEFINE_INSTRUCTION (43, mv_call, "mv-call", 3, -1, 1)
VM_DEFINE_INSTRUCTION (43, mv_call, "mv-call", 4, -1, 1)
{
SCM x;
scm_t_int16 offset;
scm_t_int32 offset;
scm_t_uint8 *mvra;
nargs = FETCH ();
FETCH_OFFSET (offset);
mvra = ip + ((scm_t_ptrdiff)offset) * 8 - ((unsigned long)ip) % 8;
mvra = ip + offset;
x = sp[-nargs];

5
libguile/vm.c
View file

@ -180,9 +180,8 @@ static SCM
really_make_boot_program (long nargs)
{
SCM u8vec;
scm_t_uint8 text[] = { scm_op_mv_call, 0, 0, 1,
scm_op_make_int8_1, scm_op_nop, scm_op_nop, scm_op_nop,
scm_op_halt };
scm_t_uint8 text[] = { scm_op_mv_call, 0, 0, 0, 1,
scm_op_make_int8_1, scm_op_halt };
struct scm_objcode *bp;
SCM ret;

2
module/language/assembly.scm
View file

@ -72,7 +72,7 @@
'(nop)))
(define (align-block addr)
(code-alignment addr *block-alignment* 0))
'())
(define (align-code code addr alignment header-len)
`(,@(code-alignment addr alignment header-len)

14
module/language/assembly/compile-bytecode.scm
View file

@ -55,6 +55,10 @@
(define (write-uint16-le x)
(write-byte (logand x 255))
(write-byte (logand (ash x -8) 255)))
(define (write-uint24-be x)
(write-byte (logand (ash x -16) 255))
(write-byte (logand (ash x -8) 255))
(write-byte (logand x 255)))
(define (write-uint32-be x)
(write-byte (logand (ash x -24) 255))
(write-byte (logand (ash x -16) 255))
@ -85,12 +89,10 @@
;; Ew!
(for-each write-byte (bytevector->u8-list bv)))
(define (write-break label)
(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 ((offset (- (assq-ref labels label) (+ (get-addr) 3))))
(cond ((>= offset (ash 1 23)) (error "jump too far forward" offset))
((< offset (- (ash 1 23))) (error "jump too far backwards" offset))
(else (write-uint24-be offset)))))
(let ((inst (car asm))
(args (cdr asm))

19
module/language/assembly/decompile-bytecode.scm
View file

@ -43,11 +43,11 @@
(define (br-instruction? x)
(memq x '(br br-if br-if-not br-if-eq br-if-not-eq br-if-null br-if-not-null)))
(define (bytes->s16 a b)
(let ((x (+ (ash a 8) b)))
(if (zero? (logand (ash 1 15) x))
(define (bytes->s24 a b c)
(let ((x (+ (ash a 16) (ash b 8) c)))
(if (zero? (logand (ash 1 23) x))
x
(- x (ash 1 16)))))
(- x (ash 1 24)))))
;; FIXME: this is a little-endian disassembly!!!
(define (decode-load-program pop)
@ -60,9 +60,8 @@
(%unused-pad (begin (pop) (pop) (pop) (pop)))
(labels '())
(i 0))
(define (ensure-label rel1 rel2)
(let ((where (+ (logand i (lognot #x7))
(* (bytes->s16 rel1 rel2) 8))))
(define (ensure-label rel1 rel2 rel3)
(let ((where (+ i (bytes->s24 rel1 rel2 rel3))))
(or (assv-ref labels where)
(begin
(let ((l (gensym ":L")))
@ -87,9 +86,9 @@
(else
(let ((exp (decode-bytecode sub-pop)))
(pmatch exp
((,br ,rel1 ,rel2) (guard (br-instruction? br))
(lp (cons `(,br ,(ensure-label rel1 rel2)) out)))
((mv-call ,n ,rel1 ,rel2)
((,br ,rel1 ,rel2 ,rel3) (guard (br-instruction? br))
(lp (cons `(,br ,(ensure-label rel1 rel2 rel3)) out)))
((mv-call ,n ,rel1 ,rel2 ,rel3)
(lp (cons `(mv-call ,n ,(ensure-label rel1 rel2)) out)))
(else
(lp (cons exp out))))))))))