Exercise 5.33.  Consider the following definition of a factorial 
procedure, which is slightly different from the one given above:

(define (factorial-alt n)
  (if (= n 1)
      1
      (* n (factorial-alt (- n 1)))))

Compile this procedure and compare the resulting code with that produced 
for factorial. Explain any differences you find. Does either program 
execute more efficiently than the other?

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The original:

(compile '(define (factorial n) (if (= n 1) 1 (* (factorial (- n 1)) n))) 'val 'next)

((env)
(val)
((assign val (op make-compiled-procedure)
(label entry2)
(reg env))
(goto (label after-lambda1)) entry2 (assign env (op compiled-procedure-env)
(reg proc))
(assign env (op extend-environment)
(const (n))
(reg argl)
(reg env))
(save continue)
(save env)
(assign proc (op lookup-variable-value)
(const =)
(reg env))
(assign val (const 1))
(assign argl (op list)
(reg val))
(assign val (op lookup-variable-value)
(const n)
(reg env))
(assign argl (op cons)
(reg val)
(reg argl))
(test (op primitive-procedure?)
(reg proc))
(branch (label primitive-branch17)) compiled-branch16 (assign continue (label after-call15))
(assign val (op compiled-procedure-entry)
(reg proc))
(goto (reg val)) primitive-branch17 (assign val (op apply-primitive-procedure)
(reg proc)
(reg argl)) after-call15 (restore env)
(restore continue)
(test (op false?)
(reg val))
(branch (label false-branch4)) true-branch5 (assign val (const 1))
(goto (reg continue)) false-branch4 (assign proc (op lookup-variable-value)
(const *)
(reg env))
(save continue)
(save proc)
(assign val (op lookup-variable-value)
(const n)
(reg env))
(assign argl (op list)
(reg val))
(save argl)
(assign proc (op lookup-variable-value)
(const factorial)
(reg env))
(save proc)
(assign proc (op lookup-variable-value)
(const -)
(reg env))
(assign val (const 1))
(assign argl (op list)
(reg val))
(assign val (op lookup-variable-value)
(const n)
(reg env))
(assign argl (op cons)
(reg val)
(reg argl))
(test (op primitive-procedure?)
(reg proc))
(branch (label primitive-branch8)) compiled-branch7 (assign continue (label after-call6))
(assign val (op compiled-procedure-entry)
(reg proc))
(goto (reg val)) primitive-branch8 (assign val (op apply-primitive-procedure)
(reg proc)
(reg argl)) after-call6 (assign argl (op list)
(reg val))
(restore proc)
(test (op primitive-procedure?)
(reg proc))
(branch (label primitive-branch11)) compiled-branch10 (assign continue (label after-call9))
(assign val (op compiled-procedure-entry)
(reg proc))
(goto (reg val)) primitive-branch11 (assign val (op apply-primitive-procedure)
(reg proc)
(reg argl)) after-call9 (restore argl)
(assign argl (op cons)
(reg val)
(reg argl))
(restore proc)
(restore continue)
(test (op primitive-procedure?)
(reg proc))
(branch (label primitive-branch14)) compiled-branch13 (assign val (op compiled-procedure-entry)
(reg proc))
(goto (reg val)) primitive-branch14 (assign val (op apply-primitive-procedure)
(reg proc)
(reg argl))
(goto (reg continue)) after-call12 after-if3 after-lambda1 (perform (op define-variable!)
(const factorial)
(reg val)
(reg env))
(assign val (const ok))))

The alternate:

(compile '(define (factorial-alt n) (if (= n 1) 1 (* n (factorial-alt (- n 1))))) 'val 'next)

((env)
(val)
((assign val (op make-compiled-procedure)
(label entry2)
(reg env))
(goto (label after-lambda1)) entry2 (assign env (op compiled-procedure-env)
(reg proc))
(assign env (op extend-environment)
(const (n))
(reg argl)
(reg env))
(save continue)
(save env)
(assign proc (op lookup-variable-value)
(const =)
(reg env))
(assign val (const 1))
(assign argl (op list)
(reg val))
(assign val (op lookup-variable-value)
(const n)
(reg env))
(assign argl (op cons)
(reg val)
(reg argl))
(test (op primitive-procedure?)
(reg proc))
(branch (label primitive-branch17)) compiled-branch16 (assign continue (label after-call15))
(assign val (op compiled-procedure-entry)
(reg proc))
(goto (reg val)) primitive-branch17 (assign val (op apply-primitive-procedure)
(reg proc)
(reg argl)) after-call15 (restore env)
(restore continue)
(test (op false?)
(reg val))
(branch (label false-branch4)) true-branch5 (assign val (const 1))
(goto (reg continue)) false-branch4 (assign proc (op lookup-variable-value)
(const *)
(reg env))
(save continue)
(save proc)
(save env)
(assign proc (op lookup-variable-value)
(const factorial-alt)
(reg env))
(save proc)
(assign proc (op lookup-variable-value)
(const -)
(reg env))
(assign val (const 1))
(assign argl (op list)
(reg val))
(assign val (op lookup-variable-value)
(const n)
(reg env))
(assign argl (op cons)
(reg val)
(reg argl))
(test (op primitive-procedure?)
(reg proc))
(branch (label primitive-branch8)) compiled-branch7 (assign continue (label after-call6))
(assign val (op compiled-procedure-entry)
(reg proc))
(goto (reg val)) primitive-branch8 (assign val (op apply-primitive-procedure)
(reg proc)
(reg argl)) after-call6 (assign argl (op list)
(reg val))
(restore proc)
(test (op primitive-procedure?)
(reg proc))
(branch (label primitive-branch11)) compiled-branch10 (assign continue (label after-call9))
(assign val (op compiled-procedure-entry)
(reg proc))
(goto (reg val)) primitive-branch11 (assign val (op apply-primitive-procedure)
(reg proc)
(reg argl)) after-call9 (assign argl (op list)
(reg val))
(restore env)
(assign val (op lookup-variable-value)
(const n)
(reg env))
(assign argl (op cons)
(reg val)
(reg argl))
(restore proc)
(restore continue)
(test (op primitive-procedure?)
(reg proc))
(branch (label primitive-branch14)) compiled-branch13 (assign val (op compiled-procedure-entry)
(reg proc))
(goto (reg val)) primitive-branch14 (assign val (op apply-primitive-procedure)
(reg proc)
(reg argl))
(goto (reg continue)) after-call12 after-if3 after-lambda1 (perform (op define-variable!)
(const factorial-alt)
(reg val)
(reg env))
(assign val (const ok))))

The diff:

((env)                                                             ((env)
(val)                                                              (val)
((assign val (op make-compiled-procedure)                          ((assign val (op make-compiled-procedure)
(label entry2)                                                     (label entry2)
(reg env))                                                         (reg env))
(goto (label after-lambda1)) entry2 (assign env (op compiled-pr    (goto (label after-lambda1)) entry2 (assign env (op compiled-pr
(reg proc))                                                        (reg proc))
(assign env (op extend-environment)                                (assign env (op extend-environment)
(const (n))                                                        (const (n))
(reg argl)                                                         (reg argl)
(reg env))                                                         (reg env))
(save continue)                                                    (save continue)
(save env)                                                         (save env)
(assign proc (op lookup-variable-value)                            (assign proc (op lookup-variable-value)
(const =)                                                          (const =)
(reg env))                                                         (reg env))
(assign val (const 1))                                             (assign val (const 1))
(assign argl (op list)                                             (assign argl (op list)
(reg val))                                                         (reg val))
(assign val (op lookup-variable-value)                             (assign val (op lookup-variable-value)
(const n)                                                          (const n)
(reg env))                                                         (reg env))
(assign argl (op cons)                                             (assign argl (op cons)
(reg val)                                                          (reg val)
(reg argl))                                                        (reg argl))
(test (op primitive-procedure?)                                    (test (op primitive-procedure?)
(reg proc))                                                        (reg proc))
(branch (label primitive-branch17)) compiled-branch16 (assign c    (branch (label primitive-branch17)) compiled-branch16 (assign c
(assign val (op compiled-procedure-entry)                          (assign val (op compiled-procedure-entry)
(reg proc))                                                        (reg proc))
(goto (reg val)) primitive-branch17 (assign val (op apply-primi    (goto (reg val)) primitive-branch17 (assign val (op apply-primi
(reg proc)                                                         (reg proc)
(reg argl)) after-call15 (restore env)                             (reg argl)) after-call15 (restore env)
(restore continue)                                                 (restore continue)
(test (op false?)                                                  (test (op false?)
(reg val))                                                         (reg val))
(branch (label false-branch4)) true-branch5 (assign val (const     (branch (label false-branch4)) true-branch5 (assign val (const 
(goto (reg continue)) false-branch4 (assign proc (op lookup-var    (goto (reg continue)) false-branch4 (assign proc (op lookup-var
(const *)                                                          (const *)
(reg env))                                                         (reg env))
(save continue)                                                    (save continue)
(save proc)                                                        (save proc)
(assign val (op lookup-variable-value)                          |  (save env)
(const n)                                                       <
(reg env))                                                      <
(assign argl (op list)                                          <
(reg val))                                                      <
(save argl)                                                     <
(assign proc (op lookup-variable-value)                            (assign proc (op lookup-variable-value)
(const factorial)                                               |  (const factorial-alt)
(reg env))                                                         (reg env))
(save proc)                                                        (save proc)
(assign proc (op lookup-variable-value)                            (assign proc (op lookup-variable-value)
(const -)                                                          (const -)
(reg env))                                                         (reg env))
(assign val (const 1))                                             (assign val (const 1))
(assign argl (op list)                                             (assign argl (op list)
(reg val))                                                         (reg val))
(assign val (op lookup-variable-value)                             (assign val (op lookup-variable-value)
(const n)                                                          (const n)
(reg env))                                                         (reg env))
(assign argl (op cons)                                             (assign argl (op cons)
(reg val)                                                          (reg val)
(reg argl))                                                        (reg argl))
(test (op primitive-procedure?)                                    (test (op primitive-procedure?)
(reg proc))                                                        (reg proc))
(branch (label primitive-branch8)) compiled-branch7 (assign con    (branch (label primitive-branch8)) compiled-branch7 (assign con
(assign val (op compiled-procedure-entry)                          (assign val (op compiled-procedure-entry)
(reg proc))                                                        (reg proc))
(goto (reg val)) primitive-branch8 (assign val (op apply-primit    (goto (reg val)) primitive-branch8 (assign val (op apply-primit
(reg proc)                                                         (reg proc)
(reg argl)) after-call6 (assign argl (op list)                     (reg argl)) after-call6 (assign argl (op list)
(reg val))                                                         (reg val))
(restore proc)                                                     (restore proc)
(test (op primitive-procedure?)                                    (test (op primitive-procedure?)
(reg proc))                                                        (reg proc))
(branch (label primitive-branch11)) compiled-branch10 (assign c    (branch (label primitive-branch11)) compiled-branch10 (assign c
(assign val (op compiled-procedure-entry)                          (assign val (op compiled-procedure-entry)
(reg proc))                                                        (reg proc))
(goto (reg val)) primitive-branch11 (assign val (op apply-primi    (goto (reg val)) primitive-branch11 (assign val (op apply-primi
(reg proc)                                                         (reg proc)
(reg argl)) after-call9 (restore argl)                          |  (reg argl)) after-call9 (assign argl (op list)
                                                                >  (reg val))
                                                                >  (restore env)
                                                                >  (assign val (op lookup-variable-value)
                                                                >  (const n)
                                                                >  (reg env))
(assign argl (op cons)                                             (assign argl (op cons)
(reg val)                                                          (reg val)
(reg argl))                                                        (reg argl))
(restore proc)                                                     (restore proc)
(restore continue)                                                 (restore continue)
(test (op primitive-procedure?)                                    (test (op primitive-procedure?)
(reg proc))                                                        (reg proc))
(branch (label primitive-branch14)) compiled-branch13 (assign v    (branch (label primitive-branch14)) compiled-branch13 (assign v
(reg proc))                                                        (reg proc))
(goto (reg val)) primitive-branch14 (assign val (op apply-primi    (goto (reg val)) primitive-branch14 (assign val (op apply-primi
(reg proc)                                                         (reg proc)
(reg argl))                                                        (reg argl))
(goto (reg continue)) after-call12 after-if3 after-lambda1 (per    (goto (reg continue)) after-call12 after-if3 after-lambda1 (per
(const factorial)                                               |  (const factorial-alt)
(reg val)                                                          (reg val)
(reg env))                                                         (reg env))
(assign val (const ok))))                                          (assign val (const ok))))