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base.rkt
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base.rkt
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#lang racket
(require "../../utility.rkt")
(define (make-machine ops
controller-text)
(let ((machine (make-new-machine)))
((machine 'install-operations) ops)
(let-values ([(seq labels) (assemble controller-text machine)])
((machine 'install-instruction-sequence) seq labels))
machine))
(define (make-register name)
(let ((contents *UNASSIGNED-VALUE*)
(trace-enabled false))
(define (dispatch message)
(cond ((eq? message 'get) contents)
((eq? message 'set)
(lambda (value)
(define (print-reg-val val)
(if (pair? val)
(if (instruction-labels (car val))
(display (string-join (map ~s (instruction-labels (car val))) "/"))
(begin
(display (instruction-text (car val)))
(display "...")))
(display val)))
(when trace-enabled
(display "reg ")
(display name)
(display " -- ")
(print-reg-val contents)
(display " -> ")
(print-reg-val value)
(newline))
(set! contents value)))
((eq? message 'trace-on)
(set! trace-enabled true))
((eq? message 'trace-off)
(set! trace-enabled false))
(else
(error "Unknown request:
REGISTER"
message))))
dispatch))
(define *UNASSIGNED-VALUE* '*unassigned*)
(define (get-contents register)
(register 'get))
(define (set-contents! register value)
((register 'set) value))
(define (make-stack)
(let ((s '())
(number-pushes 0)
(max-depth 0)
(current-depth 0))
(define (push x)
(set! s (cons x s))
(set! number-pushes (+ 1 number-pushes))
(set! current-depth (+ 1 current-depth))
(set! max-depth
(max current-depth max-depth)))
(define (pop)
(if (null? s)
(error "Empty stack: POP")
(let ((top (car s)))
(set! s (cdr s))
(set! current-depth
(- current-depth 1))
top)))
(define (initialize)
(set! s '())
(set! number-pushes 0)
(set! max-depth 0)
(set! current-depth 0)
'done)
(define (print-statistics)
(display (list 'total-pushes
'=
number-pushes
'maximum-depth
'=
max-depth))
(newline))
(define (dispatch message)
(cond ((eq? message 'push) push)
((eq? message 'pop) (pop))
((eq? message 'initialize)
(initialize))
((eq? message 'print-statistics)
(print-statistics))
(else
(error "Unknown request: STACK"
message))))
dispatch))
(define (pop stack) (stack 'pop))
(define (push stack value)
((stack 'push) value))
(define (make-new-machine)
(let ((pc (make-register 'pc))
(flag (make-register 'flag))
(stack (make-stack))
(the-instruction-sequence '())
(execution-count 0)
(trace-enabled false)
(labels '()))
(define (get-execution-count)
(display "instructions executed since last call: ")
(display execution-count)
(newline)
(set! execution-count 0))
(let ((the-ops
(list
(list 'initialize-stack
(lambda ()
(stack 'initialize)))
(list 'print-stack-statistics
(lambda ()
(stack 'print-statistics)))
(list 'get-execution-count
(lambda ()
(get-execution-count)))))
(register-table
(list (list 'pc pc)
(list 'flag flag))))
(define (inst-at label offset)
(let ([ref-entry (assoc label labels)])
(if (not ref-entry)
false
(with-handlers ([exn:fail:contract? (λ (e) false)])
(list-ref (cdr ref-entry) offset)))))
(define (set-breakpoint label offset)
(let ([inst (inst-at label offset)])
(if (not inst)
(displayln "could not find instruction")
(set-instruction-breakpoint! inst (make-breakpoint label offset)))))
(define (cancel-breakpoint label offset)
(let ([inst (inst-at label offset)])
(if (not inst)
(displayln "could not find instruction")
(let ([bp (instruction-breakpoint inst)])
(if (not bp)
(displayln "Could not cancel breakpoint (existing breakpoint not found)")
(set-instruction-breakpoint! inst false))))))
(define (allocate-register name)
(if (assoc name register-table)
(error
"Multiply defined register: "
name)
(let ([register (make-register name)])
(set! register-table
(cons
(list name register)
register-table))
register)))
(define (lookup-register name)
(let ((val
(assoc name register-table)))
(if val
(cadr val)
(error "Unknown register:"
name))))
(define (get-or-create-register name)
(let ([val (assoc name register-table)])
(if val
(cadr val)
(allocate-register name))))
(define (proceed-with-instruction inst)
((instruction-execution-proc inst))
(set! execution-count (+ execution-count 1))
(execute))
(define (proceed-execution)
(let ([insts (get-contents pc)])
(cond [(null? insts) 'done]
[(eq? (car insts) *UNASSIGNED-VALUE*)
(error "Machine not started")]
[else (proceed-with-instruction (car insts))])))
(define (execute)
(let ((insts (get-contents pc)))
(if (null? insts)
'done
(begin
(when trace-enabled
(for-each
(lambda (label)
(display label)
(display ":")
(newline))
(instruction-labels (car insts)))
(display (instruction-text (car insts)))
(newline))
(let ([bp (instruction-breakpoint (car insts))])
(if bp
(begin
(display "breakpoint -- ")
(display (breakpoint-label bp))
(display " + ")
(display (breakpoint-offset bp))
(newline))
(proceed-with-instruction (car insts))))))))
(define (trace-register name)
(let ([reg (assoc name register-table)])
(if (not reg)
(error "Register not found:" name)
((cadr reg) 'trace-on))))
(define (stop-trace-register name)
(let ([reg (assoc name register-table)])
(if (not reg)
(error "Register not found:" name)
((cadr reg) 'trace-off))))
(define (dispatch message)
(cond ((eq? message 'start)
(set-contents!
pc
the-instruction-sequence)
(execute))
((eq? message 'proceed)
(proceed-execution))
((eq?
message
'install-instruction-sequence)
(lambda (seq new-labels)
(set! the-instruction-sequence seq)
(set! labels new-labels)))
((eq? message
'allocate-register)
allocate-register)
((eq? message 'get-register)
lookup-register)
((eq? message 'get-or-create-register)
get-or-create-register)
((eq? message
'install-operations)
(lambda (ops)
(set! the-ops
(append the-ops ops))))
((eq? message 'stack) stack)
((eq? message 'operations)
the-ops)
((eq? message 'sorted-instructions)
(groupby car (rm-dupes (map mcar the-instruction-sequence))))
((eq? message 'entry-point-regs)
(entry-point-regs (map mcar the-instruction-sequence)))
((eq? message 'save-restore-regs)
(save-restore-regs (map mcar the-instruction-sequence)))
((eq? message 'assignment-sources)
(assignment-sources-grouped (map mcar the-instruction-sequence)))
((eq? message 'trace-on)
(set! trace-enabled true))
((eq? message 'trace-off)
(set! trace-enabled false))
((eq? message 'trace-register)
trace-register)
((eq? message 'stop-trace-register)
stop-trace-register)
((eq? message 'set-breakpoint)
set-breakpoint)
((eq? message 'cancel-breakpoint)
cancel-breakpoint)
((eq? message 'cancel-all-breakpoints)
(for-each
(lambda (inst)
(set-instruction-breakpoint! inst false))
the-instruction-sequence))
(else (error "Unknown request:
MACHINE"
message))))
dispatch)))
(define (set-breakpoint machine label offset)
((machine 'set-breakpoint) label offset))
(define (cancel-breakpoint machine label offset)
((machine 'cancel-breakpoint) label offset))
(define (cancel-all-breakpoints machine)
(machine 'cancel-all-breakpoints))
(define (assignment-sources-grouped insts)
(map
(lambda (pair)
(list
(car pair)
(map
(lambda (inst)
(assign-value-exp inst))
(cadr pair))))
(groupby
assign-reg-name
(filter
(lambda (inst) (equal? (car inst) 'assign))
(rm-dupes insts)))))
(define (save-restore-regs insts)
(rm-dupes
(map
stack-inst-reg-name
(filter
(lambda (inst)
(or
(eq? (car inst) 'save)
(eq? (car inst) 'restore)))
insts))))
(define (entry-point-regs insts)
(rm-dupes
(map
(lambda (inst)
(cadr (goto-dest inst)))
(filter
(lambda (inst)
(and
(eq? (car inst) 'goto)
(register-exp? (goto-dest inst))))
insts))))
(define (start machine)
(machine 'start))
(define (proceed-machine machine)
(machine 'proceed))
(define (get-register-contents
machine register-name)
(get-contents
(get-register machine register-name)))
(define (set-register-contents!
machine register-name value)
(set-contents!
(get-register machine register-name)
value)
'done)
(define (get-register machine reg-name)
((machine 'get-register) reg-name))
(define (get-or-create-register machine reg-name)
((machine 'get-or-create-register) reg-name))
(define (assemble controller-text machine)
(extract-labels controller-text
(lambda (insts labels)
(update-insts! insts labels machine)
(values insts labels))))
(define (extract-labels text receive)
(if (null? text)
(receive '() '())
(extract-labels
(cdr text)
(lambda (insts labels)
(let ((next-inst (car text)))
(if (symbol? next-inst)
(if (assoc next-inst labels)
(error "Label already exists --" next-inst)
(receive
insts
(cons
(make-label-entry
next-inst
insts)
labels)))
(receive
(cons (make-instruction
next-inst)
insts)
labels)))))))
(define (update-insts! insts labels machine)
(let ((pc (get-register machine 'pc))
(flag (get-register machine 'flag))
(stack (machine 'stack))
(ops (machine 'operations)))
(for-each
(lambda (inst)
(set-instruction-execution-proc!
inst
(make-execution-procedure
(instruction-text inst)
labels
machine
pc
flag
stack
ops)))
insts)
(for-each
(lambda (pair)
(let ([label (car pair)]
[inst (cadr pair)])
(set-instruction-labels! inst (append (instruction-labels inst) (list label)))))
labels)))
(define (make-breakpoint label offset)
(cons label offset))
(define breakpoint-label car)
(define breakpoint-offset cdr)
(define (make-instruction text)
(mcons text (mcons '() (mcons '() false))))
(define (instruction-text inst) (mcar inst))
(define (instruction-execution-proc inst)
(mcadr inst))
(define (instruction-labels inst)
(mcaddr inst))
(define (set-instruction-execution-proc!
inst
proc)
(set-mcar! (mcdr inst) proc))
(define (set-instruction-labels! inst labels)
(set-mcar! (mcddr inst) labels))
(define (set-instruction-breakpoint! inst b)
(set-mcdr! (mcddr inst) b))
(define (instruction-breakpoint inst)
(mcdddr inst))
(define (make-label-entry label-name insts)
(cons label-name insts))
(define (lookup-label labels label-name)
(let ((val (assoc label-name labels)))
(if val
(cdr val)
(error "Undefined label: ASSEMBLE"
label-name))))
(define (make-execution-procedure
inst labels machine pc flag stack ops)
(cond ((eq? (car inst) 'assign)
(make-assign
inst machine labels ops pc))
((eq? (car inst) 'test)
(make-test
inst machine labels ops flag pc))
((eq? (car inst) 'branch)
(make-branch
inst machine labels flag pc))
((eq? (car inst) 'goto)
(make-goto inst machine labels pc))
((eq? (car inst) 'save)
(make-save inst machine stack pc))
((eq? (car inst) 'restore)
(make-restore inst machine stack pc))
((eq? (car inst) 'perform)
(make-perform
inst machine labels ops pc))
(else (error "Unknown instruction
type: ASSEMBLE"
inst))))
(define (make-assign
inst machine labels operations pc)
(let ((target
(get-or-create-register
machine
(assign-reg-name inst)))
(value-exp (assign-value-exp inst)))
(let ((value-proc
(if (operation-exp? value-exp)
(make-operation-exp
value-exp
machine
labels
operations)
(make-primitive-exp
(car value-exp)
machine
labels))))
(lambda () ; execution procedure
; for assign
(set-contents! target (value-proc))
(advance-pc pc)))))
(define (assign-reg-name assign-instruction)
(cadr assign-instruction))
(define (assign-value-exp assign-instruction)
(cddr assign-instruction))
(define (advance-pc pc)
(set-contents! pc (cdr (get-contents pc))))
(define
(make-test
inst machine labels operations flag pc)
(let ((condition (test-condition inst)))
(if (operation-exp? condition)
(let ((condition-proc
(make-operation-exp
condition
machine
labels
operations)))
(lambda ()
(set-contents!
flag (condition-proc))
(advance-pc pc)))
(error "Bad TEST instruction:
ASSEMBLE" inst))))
(define (test-condition test-instruction)
(cdr test-instruction))
(define
(make-branch
inst machine labels flag pc)
(let ((dest (branch-dest inst)))
(if (label-exp? dest)
(let ((insts
(lookup-label
labels
(label-exp-label dest))))
(lambda ()
(if (get-contents flag)
(set-contents! pc insts)
(advance-pc pc))))
(error "Bad BRANCH instruction:
ASSEMBLE"
inst))))
(define (branch-dest branch-instruction)
(cadr branch-instruction))
(define (make-goto inst machine labels pc)
(let ((dest (goto-dest inst)))
(cond ((label-exp? dest)
(let ((insts
(lookup-label
labels
(label-exp-label dest))))
(lambda ()
(set-contents! pc insts))))
((register-exp? dest)
(let ((reg
(get-or-create-register
machine
(register-exp-reg dest))))
(lambda ()
(set-contents!
pc
(get-contents reg)))))
(else (error "Bad GOTO instruction:
ASSEMBLE"
inst)))))
(define (goto-dest goto-instruction)
(cadr goto-instruction))
(define (make-save inst machine stack pc)
(let ((reg (get-or-create-register
machine
(stack-inst-reg-name inst))))
(lambda ()
(push stack (get-contents reg))
(advance-pc pc))))
(define (make-restore inst machine stack pc)
(let ((reg (get-or-create-register
machine
(stack-inst-reg-name inst))))
(lambda ()
(set-contents! reg (pop stack))
(advance-pc pc))))
(define (stack-inst-reg-name
stack-instruction)
(cadr stack-instruction))
(define (make-perform
inst machine labels operations pc)
(let ((action (perform-action inst)))
(if (operation-exp? action)
(let ((action-proc
(make-operation-exp
action
machine
labels
operations)))
(lambda ()
(action-proc)
(advance-pc pc)))
(error "Bad PERFORM instruction:
ASSEMBLE"
inst))))
(define (perform-action inst) (cdr inst))
(define (make-primitive-exp exp machine labels)
(cond ((constant-exp? exp)
(let ((c (constant-exp-value exp)))
(lambda () c)))
((label-exp? exp)
(let ((insts
(lookup-label
labels
(label-exp-label exp))))
(lambda () insts)))
((register-exp? exp)
(let ((r (get-or-create-register
machine
(register-exp-reg exp))))
(lambda () (get-contents r))))
(else (error "Unknown expression type:
ASSEMBLE"
exp))))
(define (tagged-list? exp tag)
(if (pair? exp)
(eq? (car exp) tag)
false))
(define (register-exp? exp)
(tagged-list? exp 'reg))
(define (register-exp-reg exp)
(cadr exp))
(define (constant-exp? exp)
(tagged-list? exp 'const))
(define (constant-exp-value exp)
(cadr exp))
(define (label-exp? exp)
(tagged-list? exp 'label))
(define (label-exp-label exp)
(cadr exp))
(define (make-operation-exp
exp machine labels operations)
(let ((op (lookup-prim
(operation-exp-op exp)
operations))
(aprocs
(map (lambda (e)
(if (label-exp? e)
(error "Operation cannot operate on label expression")
(make-primitive-exp
e machine labels)))
(operation-exp-operands exp))))
(lambda () (apply op (map (lambda (p) (p))
aprocs)))))
(define (operation-exp? exp)
(and (pair? exp)
(tagged-list? (car exp) 'op)))
(define (operation-exp-op operation-exp)
(cadr (car operation-exp)))
(define (operation-exp-operands operation-exp)
(cdr operation-exp))
(define (lookup-prim symbol operations)
(let ((val (assoc symbol operations)))
(if val
(cadr val)
(error "Unknown operation: ASSEMBLE"
symbol))))
(define fact-machine
(make-machine
(list (list '= =) (list '* *) (list '- -))
'( (assign continue (label fact-done)) ; set up final return address
fact-loop
(test (op =) (reg n) (const 1))
(branch (label base-case))
(save continue) ; Set up for the recursive call
(save n) ; by saving n and continue.
(assign n (op -) (reg n) (const 1)) ; Set up continue so that the
(assign continue (label after-fact)) ; computation will continue
(goto (label fact-loop)) ; at after-fact when the
after-fact ; subroutine returns.
(restore n)
(restore continue)
(assign val (op *) (reg n) (reg val)) ; val now contains n(n - 1)!
(goto (reg continue)) ; return to caller
base-case
base-case2
(assign val (const 1)) ; base case: 1! = 1
(goto (reg continue)) ; return to caller
fact-done
(perform (op print-stack-statistics)))))
(set-register-contents! fact-machine 'n 5)
;(fact-machine 'trace-on)
;((fact-machine 'trace-register) 'continue)
;((fact-machine 'trace-register) 'val)
(set-breakpoint fact-machine 'after-fact 2)
(set-breakpoint fact-machine 'after-fact 2)
(start fact-machine)
(proceed-machine fact-machine)
(cancel-breakpoint fact-machine 'after-fact 2)
(cancel-breakpoint fact-machine 'after-fact 2)
(cancel-breakpoint fact-machine 'after-fact 1)
(set-breakpoint fact-machine 'after-fact 2)
(cancel-all-breakpoints fact-machine)
(proceed-machine fact-machine)
(display "fact-machine: ")
(display (get-register-contents fact-machine 'val))
(newline)