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|
; Copyright (C) 1999 J Strother Moore
; This book 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 of the License, or
; (at your option) any later version.
; This book 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 this book; if not, write to the Free Software
; Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
; This book defines the ``Toy Java Virtual Machine'' tjvm, discussed in the
; paper
; Proving Theorems about Java-like Byte Code
; by J Strother Moore
#|
; Certification Instructions.
; To certify this book, connect to the directory containing this file, fire
; up ACL2 and execute
(DEFPKG "TJVM"
(set-difference-equal (union-eq '(ASSOC-EQUAL LEN NTH ZP SYNTAXP
QUOTEP FIX NFIX E0-ORDINALP E0-ORD-<)
(union-eq *acl2-exports*
*common-lisp-symbols-from-main-lisp-package*))
'(PC PROGRAM PUSH POP REVERSE STEP ++)))
; Notes on the Imports Above
; The first set of symbols, ASSOC-EQUAL, NTH, ..., NFIX are among many
; useful function symbols defined in ACL2 that have been omitted from
; *acl2-exports*! I delete PUSH, ..., ++ because they are defined in
; Common Lisp in ways different than I wish to define them below.
; Then do
(certify-book "tjvm" 1)
|#
(in-package "TJVM")
; -----------------------------------------------------------------------------
; Utilities
(defun push (obj stack) (cons obj stack))
(defun top (stack) (car stack))
(defun pop (stack) (cdr stack))
;(defun assoc-equal (x alist)
; (cond ((endp alist) nil)
; ((equal x (car (car alist)))
; (car alist))
; (t (assoc-equal x (cdr alist)))))
(defun bound? (x alist) (assoc-equal x alist))
(defun bind (x y alist)
(cond ((endp alist) (list (cons x y)))
((equal x (car (car alist)))
(cons (cons x y) (cdr alist)))
(t (cons (car alist) (bind x y (cdr alist))))))
(defun binding (x alist) (cdr (assoc-equal x alist)))
(defun op-code (inst) (car inst))
(defun arg1 (inst) (car (cdr inst)))
(defun arg2 (inst) (car (cdr (cdr inst))))
(defun arg3 (inst) (car (cdr (cdr (cdr inst)))))
;(defun nth (i lst)
; (if (zp i)
; (car lst)
; (nth (- i 1) (cdr lst))))
(defun reverse (x)
(if (consp x)
(append (reverse (cdr x)) (list (car x)))
nil))
; -----------------------------------------------------------------------------
; States
(defun make-state (call-stack heap class-table)
(list call-stack heap class-table))
(defun call-stack (s) (nth 0 s))
(defun heap (s) (nth 1 s))
(defun class-table (s) (nth 2 s))
; -----------------------------------------------------------------------------
; Frames
(defun make-frame (pc locals stack program)
(list pc locals stack program))
(defun pc (frame) (nth 0 frame))
(defun locals (frame) (nth 1 frame))
(defun stack (frame) (nth 2 frame))
(defun program (frame) (nth 3 frame))
(defun top-frame (s) (top (call-stack s)))
; -----------------------------------------------------------------------------
; Class Declarations and the Class Table
; The class table of a state is an alist. Each entry in a class table is
; a "class declaration" and is of the form
; (class-name super-class-names fields defs)
(defun make-class-decl (name superclasses fields methods)
(list name superclasses fields methods))
(defun class-decl-name (dcl)
(nth 0 dcl))
(defun class-decl-superclasses (dcl)
(nth 1 dcl))
(defun class-decl-fields (dcl)
(nth 2 dcl))
(defun class-decl-methods (dcl)
(nth 3 dcl))
; -----------------------------------------------------------------------------
; Method Declarations
; The methods component of a class declaration is a list of method definitions.
; A method definition is a list of the form
; (name formals . program)
; We never build these declarations but just enter list constants for them,
; Note the similarity to our old notion of a program definition. We
; will use strings to name methods now.
; Method definitions will be constructed by expressions such as:
; ("move" (dx dy)
; (load this)
; (load this)
; (getfield "Point" "x")
; (load dx)
; (add)
; (putfield "Point" "x") ; this.x = this.x + dx;
; (load this)
; (load this)
; (getfield "Point" "y")
; (load dy)
; (add)
; (putfield "Point" "y") ; this.y = this.y + dy;
; (push 1)
; (xreturn))) ; return 1;
; Provided this method is defined in the class "Point" it can be invoked by
; (invokevirtual "Point" "move" 2)
; This assumes that the stack, at the time of invocation, contains an
; reference to an object of type "Point" and two numbers, dx and dy.
; The accessors for methods are:
(defun method-name (m)
(nth 0 m))
(defun method-formals (m)
(nth 1 m))
(defun method-program (m)
(cddr m))
; -----------------------------------------------------------------------------
; (PUSH const) Instruction
(defun execute-PUSH (inst s)
(make-state
(push (make-frame (+ 1 (pc (top-frame s)))
(locals (top-frame s))
(push (arg1 inst)
(stack (top-frame s)))
(program (top-frame s)))
(pop (call-stack s)))
(heap s)
(class-table s)))
; -----------------------------------------------------------------------------
; (POP) Instruction
(defun execute-POP (inst s)
(declare (ignore inst))
(make-state
(push (make-frame (+ 1 (pc (top-frame s)))
(locals (top-frame s))
(pop (stack (top-frame s)))
(program (top-frame s)))
(pop (call-stack s)))
(heap s)
(class-table s)))
; -----------------------------------------------------------------------------
; (LOAD var) Instruction
(defun execute-LOAD (inst s)
(make-state
(push (make-frame (+ 1 (pc (top-frame s)))
(locals (top-frame s))
(push (binding (arg1 inst)
(locals (top-frame s)))
(stack (top-frame s)))
(program (top-frame s)))
(pop (call-stack s)))
(heap s)
(class-table s)))
; -----------------------------------------------------------------------------
; (STORE var) Instruction
(defun execute-STORE (inst s)
(make-state
(push (make-frame (+ 1 (pc (top-frame s)))
(bind (arg1 inst)
(top (stack (top-frame s)))
(locals (top-frame s)))
(pop (stack (top-frame s)))
(program (top-frame s)))
(pop (call-stack s)))
(heap s)
(class-table s)))
; -----------------------------------------------------------------------------
; (ADD) Instruction
(defun execute-ADD (inst s)
(declare (ignore inst))
(make-state
(push (make-frame (+ 1 (pc (top-frame s)))
(locals (top-frame s))
(push (+ (top (pop (stack (top-frame s))))
(top (stack (top-frame s))))
(pop (pop (stack (top-frame s)))))
(program (top-frame s)))
(pop (call-stack s)))
(heap s)
(class-table s)))
; -----------------------------------------------------------------------------
; (SUB) Instruction
(defun execute-SUB (inst s)
(declare (ignore inst))
(make-state
(push (make-frame (+ 1 (pc (top-frame s)))
(locals (top-frame s))
(push (- (top (pop (stack (top-frame s))))
(top (stack (top-frame s))))
(pop (pop (stack (top-frame s)))))
(program (top-frame s)))
(pop (call-stack s)))
(heap s)
(class-table s)))
; -----------------------------------------------------------------------------
; (MUL) Instruction
(defun execute-MUL (inst s)
(declare (ignore inst))
(make-state
(push (make-frame (+ 1 (pc (top-frame s)))
(locals (top-frame s))
(push (* (top (pop (stack (top-frame s))))
(top (stack (top-frame s))))
(pop (pop (stack (top-frame s)))))
(program (top-frame s)))
(pop (call-stack s)))
(heap s)
(class-table s)))
; -----------------------------------------------------------------------------
; (GOTO pc) Instruction
(defun execute-GOTO (inst s)
(make-state
(push (make-frame (+ (arg1 inst) (pc (top-frame s)))
(locals (top-frame s))
(stack (top-frame s))
(program (top-frame s)))
(pop (call-stack s)))
(heap s)
(class-table s)))
; -----------------------------------------------------------------------------
; (IFEQ pc) Instruction
(defun execute-IFEQ (inst s)
(make-state
(push (make-frame (if (equal (top (stack (top-frame s))) 0)
(+ (arg1 inst) (pc (top-frame s)))
(+ 1 (pc (top-frame s))))
(locals (top-frame s))
(pop (stack (top-frame s)))
(program (top-frame s)))
(pop (call-stack s)))
(heap s)
(class-table s)))
; -----------------------------------------------------------------------------
; (IFGT pc) Instruction
(defun execute-IFGT (inst s)
(make-state
(push (make-frame (if (> (top (stack (top-frame s))) 0)
(+ (arg1 inst) (pc (top-frame s)))
(+ 1 (pc (top-frame s))))
(locals (top-frame s))
(pop (stack (top-frame s)))
(program (top-frame s)))
(pop (call-stack s)))
(heap s)
(class-table s)))
; -----------------------------------------------------------------------------
; (IFLE pc) Instruction
(defun execute-IFLE (inst s)
(make-state
(push (make-frame (if (<= (top (stack (top-frame s))) 0)
(+ (arg1 inst) (pc (top-frame s)))
(+ 1 (pc (top-frame s))))
(locals (top-frame s))
(pop (stack (top-frame s)))
(program (top-frame s)))
(pop (call-stack s)))
(heap s)
(class-table s)))
; -----------------------------------------------------------------------------
; (NEW "class") Instruction
(defun build-class-field-bindings (field-names)
(if (endp field-names)
nil
(cons (cons (car field-names) 0)
(build-class-field-bindings (cdr field-names)))))
(defun build-immediate-instance-data (class-name class-table)
(cons class-name
(build-class-field-bindings
(class-decl-fields
(bound? class-name class-table)))))
(defun build-an-instance (class-names class-table)
(if (endp class-names)
nil
(cons (build-immediate-instance-data (car class-names) class-table)
(build-an-instance (cdr class-names) class-table))))
(defun refp (x)
(and (consp x)
(equal (car x) 'ref)
(consp (cdr x))
(integerp (cadr x))
(equal (cddr x) nil)))
(defun execute-NEW (inst s)
(let* ((class-name (arg1 inst))
(class-table (class-table s))
(new-object (build-an-instance
(cons class-name
(class-decl-superclasses
(bound? class-name class-table)))
class-table))
(new-address (len (heap s))))
(make-state
(push (make-frame (+ 1 (pc (top-frame s)))
(locals (top-frame s))
(push (list 'REF new-address)
(stack (top-frame s)))
(program (top-frame s)))
(pop (call-stack s)))
(bind new-address new-object (heap s))
(class-table s))))
; -----------------------------------------------------------------------------
; (GETFIELD "class" "field") Instruction
(defun deref (ref heap)
(binding (cadr ref) heap))
(defun field-value (class-name field-name instance)
(binding field-name
(binding class-name instance)))
(defun execute-GETFIELD (inst s)
(let* ((class-name (arg1 inst))
(field-name (arg2 inst))
(instance (deref (top (stack (top-frame s))) (heap s)))
(field-value (field-value class-name field-name instance)))
(make-state
(push (make-frame (+ 1 (pc (top-frame s)))
(locals (top-frame s))
(push field-value
(pop (stack (top-frame s))))
(program (top-frame s)))
(pop (call-stack s)))
(heap s)
(class-table s))))
; -----------------------------------------------------------------------------
; (PUTFIELD "class" "field") Instruction
(defun set-instance-field (class-name field-name value instance)
(bind class-name
(bind field-name value
(binding class-name instance))
instance))
(defun execute-PUTFIELD (inst s)
(let* ((class-name (arg1 inst))
(field-name (arg2 inst))
(value (top (stack (top-frame s))))
(instance (deref (top (pop (stack (top-frame s)))) (heap s)))
(address (cadr (top (pop (stack (top-frame s)))))))
(make-state
(push (make-frame (+ 1 (pc (top-frame s)))
(locals (top-frame s))
(pop (pop (stack (top-frame s))))
(program (top-frame s)))
(pop (call-stack s)))
(bind address
(set-instance-field class-name field-name value instance)
(heap s))
(class-table s))))
; -----------------------------------------------------------------------------
; (INSTANCEOF "class")
(defun execute-INSTANCEOF (inst s)
(let* ((class-name (arg1 inst))
(instance (deref (top (stack (top-frame s))) (heap s))))
(make-state
(push (make-frame (+ 1 (pc (top-frame s)))
(locals (top-frame s))
(push (if (bound? class-name instance)
1
0)
(pop (stack (top-frame s))))
(program (top-frame s)))
(pop (call-stack s)))
(heap s)
(class-table s))))
; -----------------------------------------------------------------------------
; (INVOKEVIRTUAL "class" "name" n) Instruction
(defun bind-formals (rformals stack)
(if (endp rformals)
nil
(cons (cons (car rformals) (top stack))
(bind-formals (cdr rformals) (pop stack)))))
(defun popn (n stack)
(if (zp n)
stack
(popn (- n 1) (pop stack))))
(defun class-name-of-ref (ref heap)
(car (car (deref ref heap))))
(defun lookup-method-in-superclasses (name classes class-table)
(cond ((endp classes) nil)
(t (let* ((class-name (car classes))
(class-decl (bound? class-name class-table))
(method (bound? name (class-decl-methods class-decl))))
(if method
method
(lookup-method-in-superclasses name (cdr classes)
class-table))))))
(defun lookup-method (name class-name class-table)
(lookup-method-in-superclasses name
(cons class-name
(class-decl-superclasses
(bound? class-name class-table)))
class-table))
(defun execute-INVOKEVIRTUAL (inst s)
(let* ((method-name (arg2 inst))
(nformals (arg3 inst))
(obj-ref (top (popn nformals (stack (top-frame s)))))
(obj-class-name (class-name-of-ref obj-ref (heap s)))
(closest-method
(lookup-method method-name
obj-class-name
(class-table s)))
(vars (cons 'this (method-formals closest-method)))
(prog (method-program closest-method)))
(make-state
(push (make-frame 0
(reverse
(bind-formals (reverse vars)
(stack (top-frame s))))
nil
prog)
(push (make-frame (+ 1 (pc (top-frame s)))
(locals (top-frame s))
(popn (len vars)
(stack (top-frame s)))
(program (top-frame s)))
(pop (call-stack s))))
(heap s)
(class-table s))))
; -----------------------------------------------------------------------------
; (INVOKESTATIC "class" "name" n) Instruction
(defun execute-INVOKESTATIC (inst s)
(let* ((class-name (arg1 inst))
(method-name (arg2 inst))
(closest-method
(lookup-method method-name
class-name
(class-table s)))
(vars (method-formals closest-method))
(prog (method-program closest-method)))
(make-state
(push (make-frame 0
(reverse
(bind-formals (reverse vars)
(stack (top-frame s))))
nil
prog)
(push (make-frame (+ 1 (pc (top-frame s)))
(locals (top-frame s))
(popn (len vars)
(stack (top-frame s)))
(program (top-frame s)))
(pop (call-stack s))))
(heap s)
(class-table s))))
; -----------------------------------------------------------------------------
; (RETURN) Instruction
(defun execute-RETURN (inst s)
(declare (ignore inst))
(let ((caller-frame (top (pop (call-stack s)))))
(make-state
(push (make-frame (pc caller-frame)
(locals caller-frame)
(stack caller-frame)
(program caller-frame))
(pop (pop (call-stack s))))
(heap s)
(class-table s))))
; -----------------------------------------------------------------------------
; (XRETURN) Instruction
(defun execute-XRETURN (inst s)
(declare (ignore inst))
(let ((val (top (stack (top-frame s))))
(caller-frame (top (pop (call-stack s)))))
(make-state
(push (make-frame (pc caller-frame)
(locals caller-frame)
(push val (stack caller-frame))
(program caller-frame))
(pop (pop (call-stack s))))
(heap s)
(class-table s))))
; -----------------------------------------------------------------------------
; Putting it all together
(defun next-inst (s)
(nth (pc (top-frame s))
(program (top-frame s))))
(defun do-inst (inst s)
(case (op-code inst)
(PUSH (execute-PUSH inst s))
(POP (execute-POP inst s))
(LOAD (execute-LOAD inst s))
(STORE (execute-STORE inst s))
(ADD (execute-ADD inst s))
(SUB (execute-SUB inst s))
(MUL (execute-MUL inst s))
(GOTO (execute-GOTO inst s))
(IFEQ (execute-IFEQ inst s))
(IFGT (execute-IFGT inst s))
(IFLE (execute-IFLE inst s))
(INVOKEVIRTUAL (execute-INVOKEVIRTUAL inst s))
(INVOKESTATIC (execute-INVOKESTATIC inst s))
(RETURN (execute-RETURN inst s))
(XRETURN (execute-XRETURN inst s))
(NEW (execute-NEW inst s))
(GETFIELD (execute-GETFIELD inst s))
(PUTFIELD (execute-PUTFIELD inst s))
(INSTANCEOF (execute-INSTANCEOF inst s))
(HALT s)
(otherwise s)))
(defun step (s)
(do-inst (next-inst s) s))
(defun tjvm (s n)
(if (zp n)
s
(tjvm (step s) (- n 1))))
|
