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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
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14
module/language/assembly/compile-bytecode.scm
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@ -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))