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#| assembler.jl -- higher-level assembler
$Id$
Copyright (C) 2000 John Harper <john@dcs.warwick.ac.uk>
This file is part of librep.
librep is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
librep is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with librep; see the file COPYING. If not, write to
the Free Software Foundation, 51 Franklin Street, Fifth Floor,
Boston, MA 02110-1301 USA
|#
;; The plan is to use in the compiler at some point to remove the ugly
;; lap code representation, instead compile to assembly language, then
;; assemble that.. (with the peephole pass in between)
(define-structure rep.vm.assembler
(export assemble)
(open rep
rep.vm.bytecodes
rep.data.tables
rep.data.records)
(define-record-type :label
(make-label name)
labelp
(name label-name label-name-set)
(address label-address label-address-set)
(forwards label-forwards label-forwards-set))
;; Syntax of INSNS is a list of `(INSN [ARG])' or `LABEL'. One pseudo
;; insn: `(push-label LABEL)'
;; Example:
;; ((push 0)
;; foo
;; (push 1)
;; (add)
;; (jmp foo))
;; Returns (BYTE-CODE-VECTOR . CONSTANT-VECTOR)
(define (assemble insns #!optional start)
(let ((code '())
(pc (or start 0))
(labels (make-table symbol-hash eq))
(constants '())
(next-const-id 0))
(define (get-label name)
(or (table-ref labels name)
(let ((l (make-label name)))
(table-set labels name l)
l)))
(define (get-const-id value)
(or (cdr (assoc value constants))
(prog1 next-const-id
(setq constants (cons (cons value next-const-id) constants))
(setq next-const-id (1+ next-const-id)))))
(define (emit-byte-at byte addr)
(setq code (cons (cons byte addr) code)))
(define (emit-byte byte)
(emit-byte-at byte pc)
(setq pc (1+ pc)))
(define (emit-address-at addr pc)
(emit-byte-at (ash addr -8) pc)
(emit-byte-at (logand addr 255) (1+ pc)))
(define (emit-address addr)
(emit-address-at addr pc)
(setq pc (+ pc 2)))
(define (emit-label-addr label)
(if (label-address label)
(emit-address (label-address label))
(label-forwards-set label (cons pc (label-forwards label)))
(setq pc (+ pc 2))))
(define (emit-insn insn #!optional arg)
(let ((op (bytecode-ref insn)))
(if (>= op (bytecode last-with-args))
(progn
;; ``normal'' one-byte insn encoding
(emit-byte op)
(when arg
(cond ((memq op byte-two-byte-insns)
(if (< arg 256)
(emit-byte arg)
(error
"Argument overflow in two-byte insn: %s" insn)))
((memq op byte-three-byte-insns)
(if (< arg 65536)
(progn
(emit-byte (ash arg -8))
(emit-byte (logand arg 255)))
(error
"Argument overflow in three-byte insn: %s" insn)))
(t (error "Spurious argument to insn: %s" insn)))))
;; insn with embedded argument
(cond ((<= arg byte-max-1-byte-arg)
(emit-byte (+ op arg)))
((<= arg byte-max-2-byte-arg)
(emit-byte (+ op 6))
(emit-byte arg))
((<= arg byte-max-3-byte-arg)
(emit-byte (+ op 7))
(emit-byte (ash arg -8))
(emit-byte (logand arg 255)))
(t (error "Argument overflow in insn: %s" insn))))))
(define (emit-jmp insn dest)
(emit-byte (bytecode-ref insn))
(emit-label-addr (get-label dest)))
(define (emit-push arg)
(cond ((and (fixnump arg) (<= arg 65535) (>= arg -65535))
(cond ((zerop arg)
(emit-insn 'pushi-0))
((= arg 1)
(emit-insn 'pushi-1))
((= arg 2)
(emit-insn 'pushi-2))
((= arg -1)
(emit-insn 'pushi-minus-1))
((= arg -2)
(emit-insn 'pushi-minus-2))
((and (<= arg 127) (>= arg -128))
(emit-insn 'pushi (logand arg 255)))
((and (< arg 0) (>= arg -65535))
(emit-insn 'pushi-pair-neg (- arg)))
(t (emit-insn 'pushi-pair-pos arg))))
((eq arg '()) (emit-insn 'nil))
((eq arg 't) (emit-insn 't))
(t (emit-insn 'push (get-const-id arg)))))
(define (emit-push-label arg)
;; push address of label
(emit-byte (bytecode pushi-pair-pos))
(emit-label-addr (get-label arg)))
(define (emit-label name)
(let ((label (get-label name)))
(and (label-address label)
(error "Multiply-defined label: %s, %s" name insns))
(label-address-set label pc)
;; backpatch forward references
(do ((refs (label-forwards label) (cdr refs)))
((null refs) (label-forwards-set label '()))
(emit-byte-at (ash pc -8) (car refs))
(emit-byte-at (logand pc 255) (1+ (car refs))))))
(let loop ((rest insns))
(when rest
(let ((insn (car rest)))
(cond ((symbolp insn) (emit-label insn))
((eq (car insn) 'push) (emit-push (cadr insn)))
((eq (car insn) 'push-label) (emit-push-label (cadr insn)))
((memq (car insn) '(refg setg))
;; instruction with constant
(emit-insn (car insn) (get-const-id (cadr insn))))
((memq (car insn) byte-jmp-insns)
(emit-jmp (car insn) (cadr insn)))
(t (apply emit-insn insn)))
(loop (cdr rest)))))
(let ((byte-vec (make-string pc))
(const-vec (make-vector next-const-id)))
(do ((rest code (cdr rest)))
((null rest))
(aset byte-vec (cdar rest) (caar rest)))
(do ((rest constants (cdr rest)))
((null rest))
(aset const-vec (cdar rest) (caar rest)))
(cons byte-vec const-vec)))))
|
