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5_13.scm
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5_13.scm
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(load "ch5-regsim.scm")
(define (extract-register-name inst)
(cond ((symbol? inst) '())
((eq? (car inst) 'assign)
(assign-reg-name inst))
((or (eq? (car inst) 'save) (eq? (car inst) 'restore))
(stack-inst-reg-name inst))
((eq? (car inst) 'goto)
(let ((dest (goto-dest inst)))
(if (register-exp? dest)
(register-exp-reg dest)
'())))
(else '())))
(define (not-null? x)
(not (null? x)))
(define (make-machine ops controller-text)
(let* ((machine (make-new-machine))
(registers-with-dups (filter not-null?
(map extract-register-name controller-text)))
(register-names (delete-duplicates registers-with-dups)))
(for-each (lambda (register-name)
((machine 'allocate-register) register-name))
register-names)
((machine 'install-operations) ops)
((machine 'install-instruction-sequence)
(assemble controller-text machine))
machine))
(define expt-machine-rec
(make-machine
(list (list '= =) (list '* *) (list '- -))
'((assign continue (label expt-done))
(assign n (const 2))
(assign b (const 4))
expt-loop
(test (op =) (reg n) (const 0))
(branch (label base-case))
(save continue)
(assign n (op -) (reg n) (const 1))
(assign continue (label after-expt))
(goto (label expt-loop))
after-expt
(restore continue)
(assign val (op *) (reg b) (reg val))
(goto (reg continue))
base-case
(assign val (const 1))
(goto (reg continue))
expt-done)))
(start expt-machine-rec)
(get-register-contents expt-machine-rec 'val)