SICP 読み (323) 5.5 翻訳系
直前エントリな最終的にこう、なソレを再掲
((env) (val) ((assign val (op make-compiles-procedure) (label entry6) (reg env)) (goto (label after-lambda2)) entry1 (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 (op lookup-variable-value) (const n) (reg env)) (assign argl (op list) (reg val)) (assign val (const 1)) (assign argl (op cons) (reg val) (reg argl)) (test (op primitive-procedure?) (reg proc)) (branch (label primitive-branch6)) compiled-branch7 (assign continue (label after-call8)) (assign val (op compiled-procedure-entry) (reg proc)) (goto (reg val)) primitive-branch6 (assign val (op apply-primitive-procedure) (reg proc) (reg env)) after-call8 (restore continue) (restore env) (test (op false?) (reg val)) (branch (label false-branch4)) true-branch3 (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-branch9)) compiled-branch10 (assign continue (label after-call11)) (assign val (op compiled-procedure-entry) (reg proc)) (goto (reg val)) primitive-branch9 (assign val (op apply-primitive-procedure) (reg proc) (reg argl)) after-call11 (assign argl (op list) (reg val)) (restore proc) (test (op primitive-procedure?) (reg proc)) (branch (label primitive-branch12)) compiled-branch13 (assign continue (label after-call14)) (assign val (op compiled-procedure-entry) (reg proc)) (goto (reg val)) primitive-branch12 (assign val (op apply-primitive-procedure) (reg proc) (reg argl)) after-call14 (restore argl) (assign argl (op cons) (reg val) (reg argl)) (restore proc) (restore continue) (test (op primitive-procedure?) (reg proc)) (branch (label primitive-branch15)) compiled-branch16 (assign val (op compiled-procedure-entry) (reg proc)) (goto (reg val)) primitive-branch15 (assign val (op apply-primitive-procedure) (reg proc) (reg argl)) (goto (reg continue)) after-call17 afteri-if5 after-lambda2 (perform (op define-variable!) (const factorial) (reg val) (reg env)) (assign val (const ok)) (goto (reg continue))))
ラベルも修正。で、問題のソレは
(define (fact-alt n) (if (= n 1) 1 (* n (fact-alt (- n 1)))))
ってコトだったので、一部のみ、ですがこんなカンジになるんだろうか (最初間違えて上記のナニに手を入れてしまい、打ち直してたり
false-branch4 (assign proc (op lookup-variable-value) (const *) (reg env)) (save continue) (save proc) (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-branch9)) compiled-branch10 (assign continue (label after-call11)) (assign val (op compiled-procedure-entry) (reg proc)) (goto (reg val)) primitive-branch9 (assign val (op apply-primitive-procedure) (reg proc) (reg argl)) after-call11 (assign argl (op list) (reg val)) (restore proc) (test (op primitive-procedure?) (reg proc)) (branch (label primitive-branch12)) compiled-branch13 (assign continue (label after-call14)) (assign val (op compiled-procedure-entry) (reg proc)) (goto (reg val)) primitive-branch12 (assign val (op apply-primitive-procedure) (reg proc) (reg argl)) after-call14 (assign argl (op list) (reg val)) (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-branch15))
単純に順番変えて argl の save/restore ケズっただけなんですが実際はどうか。env って save/restore しなくってええのかなぁ。最初のナニだと n の値は argl に入っていたので省略可能だったんですが、factorial の呼び出しから戻った時に env の中の n って絶対 1 だよなぁ。
construct-arglist 見てみると last-arg と rest-args の連結は (env) で preserving になっております。とゆー事は以下と
(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-branch9)) compiled-branch10 (assign continue (label after-call11)) (assign val (op compiled-procedure-entry) (reg proc)) (goto (reg val)) primitive-branch9 (assign val (op apply-primitive-procedure) (reg proc) (reg argl)) after-call11 (assign argl (op list) (reg val)) (restore proc) (test (op primitive-procedure?) (reg proc)) (branch (label primitive-branch12)) compiled-branch13 (assign continue (label after-call14)) (assign val (op compiled-procedure-entry) (reg proc)) (goto (reg val)) primitive-branch12 (assign val (op apply-primitive-procedure) (reg proc) (reg argl)) after-call14 (assign argl (op list) (reg val))
と以下を
(assign val (op lookup-variable-value) (const n) (reg env)) (assign argl (op cons) (reg val) (reg argl))
env で preserving として上側の式の modified は apply 入りなんで all-regs だし下側の式の needed は (env) だと見て良いのだろうか。
だったら以下でしょうか。
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) (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-branch9)) compiled-branch10 (assign continue (label after-call11)) (assign val (op compiled-procedure-entry) (reg proc)) (goto (reg val)) primitive-branch9 (assign val (op apply-primitive-procedure) (reg proc) (reg argl)) after-call11 (assign argl (op list) (reg val)) (restore proc) (test (op primitive-procedure?) (reg proc)) (branch (label primitive-branch12)) compiled-branch13 (assign continue (label after-call14)) (assign val (op compiled-procedure-entry) (reg proc)) (goto (reg val)) primitive-branch12 (assign val (op apply-primitive-procedure) (reg proc) (reg argl)) after-call14 (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-branch15))
今の所 argl は save/restore されないが、env が save/restore 対象ってコトにしてますが、実際どうなんだろうか、という事でやってみたのが以下 (整形済み
((env continue) (val) ((assign val (op make-compiled-procedure) (label entry1) (reg env)) (goto (label after-lambda2)) entry1 (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-branch6)) compiled-branch7 (assign continue (label after-call8)) (assign val (op compiled-procedure-entry) (reg proc)) (goto (reg val)) primitive-branch6 (assign val (op apply-primitive-procedure) (reg proc) (reg argl)) after-call8 (restore env) (restore continue) (test (op false?) (reg val)) (branch (label false-branch4)) true-branch3 (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) (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-branch9)) compiled-branch10 (assign continue (label after-call11)) (assign val (op compiled-procedure-entry) (reg proc)) (goto (reg val)) primitive-branch9 (assign val (op apply-primitive-procedure) (reg proc) (reg argl)) after-call11 (assign argl (op list) (reg val)) (restore proc) (test (op primitive-procedure?) (reg proc)) (branch (label primitive-branch12)) compiled-branch13 (assign continue (label after-call14)) (assign val (op compiled-procedure-entry) (reg proc)) (goto (reg val)) primitive-branch12 (assign val (op apply-primitive-procedure) (reg proc) (reg argl)) after-call14 (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-branch15)) compiled-branch16 (assign val (op compiled-procedure-entry) (reg proc)) (goto (reg val)) primitive-branch15 (assign val (op apply-primitive-procedure) (reg proc) (reg argl)) (goto (reg continue)) after-call17 after-if5 after-lambda2 (perform (op define-variable!) (const factorial) (reg val) (reg env)) (assign val (const ok)) (goto (reg continue))))
むむ。なんかアッてる感じ??
がしかし、_Does either program execute more efficiently than the other? _って言われても困るなぁ。(何
どちらかというと env を save/restore する方が微妙じゃね??というのは素人考えなんでしょうか...
もう少し検討してみます。