;;; Tree-IL partial evaluator
-;; Copyright (C) 2011 Free Software Foundation, Inc.
+;; Copyright (C) 2011, 2012, 2013 Free Software Foundation, Inc.
;;;; This library is free software; you can redistribute it and/or
;;;; modify it under the terms of the GNU Lesser General Public
(define-module (language tree-il peval)
#:use-module (language tree-il)
#:use-module (language tree-il primitives)
+ #:use-module (language tree-il effects)
#:use-module (ice-9 vlist)
#:use-module (ice-9 match)
#:use-module (srfi srfi-1)
;; First, some helpers.
;;
+(define-syntax *logging* (identifier-syntax #f))
+
;; For efficiency we define *logging* to inline to #f, so that the call
-;; to log* gets optimized out. If you want to log, do:
+;; to log* gets optimized out. If you want to log, uncomment these
+;; lines:
;;
-;; (define %logging #f)
-;; (define-syntax *logging* (identifier-syntax %logging)
+;; (define %logging #f)
+;; (define-syntax *logging* (identifier-syntax %logging))
;;
;; Then you can change %logging at runtime.
-;;
-(define-syntax *logging* (identifier-syntax #f))
(define-syntax log
(syntax-rules (quote)
(or (proc (vlist-ref vlist i))
(lp (1+ i)))))))
+(define (singly-valued-expression? exp)
+ (match exp
+ (($ <const>) #t)
+ (($ <lexical-ref>) #t)
+ (($ <void>) #t)
+ (($ <lexical-ref>) #t)
+ (($ <primitive-ref>) #t)
+ (($ <module-ref>) #t)
+ (($ <toplevel-ref>) #t)
+ (($ <primcall> _ (? singly-valued-primitive?)) #t)
+ (($ <primcall> _ 'values (val)) #t)
+ (($ <lambda>) #t)
+ (else #f)))
+
+(define (truncate-values x)
+ "Discard all but the first value of X."
+ (if (singly-valued-expression? x)
+ x
+ (make-primcall (tree-il-src x) 'values (list x))))
+
;; Peval will do a one-pass analysis on the source program to determine
;; the set of assigned lexicals, and to identify unreferenced and
;; singly-referenced lexicals.
;;
-;; If peval introduces more code, via copy-propagation, it will need to
-;; run `build-var-table' on the new code to add to make sure it can find
-;; a <var> for each gensym bound in the program.
-;;
(define-record-type <var>
(make-var name gensym refcount set?)
var?
(lambda (exp res)
(match exp
(($ <lexical-ref> src name gensym)
- (let ((var (vhash-assq gensym res)))
- (if var
- (begin
- (set-var-refcount! (cdr var) (1+ (var-refcount (cdr var))))
- res)
- (vhash-consq gensym (make-var name gensym 1 #f) res))))
+ (let ((var (cdr (vhash-assq gensym res))))
+ (set-var-refcount! var (1+ (var-refcount var)))
+ res))
(_ res)))
(lambda (exp res)
(match exp
+ (($ <lambda-case> src req opt rest kw init gensyms body alt)
+ (fold (lambda (name sym res)
+ (vhash-consq sym (make-var name sym 0 #f) res))
+ res
+ (append req (or opt '()) (if rest (list rest) '())
+ (match kw
+ ((aok? (kw name sym) ...) name)
+ (_ '())))
+ gensyms))
+ (($ <let> src names gensyms vals body)
+ (fold (lambda (name sym res)
+ (vhash-consq sym (make-var name sym 0 #f) res))
+ res names gensyms))
+ (($ <letrec> src in-order? names gensyms vals body)
+ (fold (lambda (name sym res)
+ (vhash-consq sym (make-var name sym 0 #f) res))
+ res names gensyms))
+ (($ <fix> src names gensyms vals body)
+ (fold (lambda (name sym res)
+ (vhash-consq sym (make-var name sym 0 #f) res))
+ res names gensyms))
(($ <lexical-set> src name gensym exp)
- (let ((var (vhash-assq gensym res)))
- (if var
- (begin
- (set-var-set?! (cdr var) #t)
- res)
- (vhash-consq gensym (make-var name gensym 0 #t) res))))
+ (set-var-set?! (cdr (vhash-assq gensym res)) #t)
+ res)
(_ res)))
(lambda (exp res) res)
table exp))
(effort effort-counter)
(size size-counter)
(continuation counter-continuation)
- (recursive? counter-recursive?)
+ (recursive? counter-recursive? set-counter-recursive?!)
(data counter-data)
(prev counter-prev))
(transfer! current c effort-limit size-limit)
c))
+;; Operand structures allow bindings to be processed lazily instead of
+;; eagerly. By doing so, hopefully we can get process them in a way
+;; appropriate to their use contexts. Operands also prevent values from
+;; being visited multiple times, wasting effort.
+;;
+;; TODO: Record value size in operand structure?
+;;
+(define-record-type <operand>
+ (%make-operand var sym visit source visit-count use-count
+ copyable? residual-value constant-value alias-value)
+ operand?
+ (var operand-var)
+ (sym operand-sym)
+ (visit %operand-visit)
+ (source operand-source)
+ (visit-count operand-visit-count set-operand-visit-count!)
+ (use-count operand-use-count set-operand-use-count!)
+ (copyable? operand-copyable? set-operand-copyable?!)
+ (residual-value operand-residual-value %set-operand-residual-value!)
+ (constant-value operand-constant-value set-operand-constant-value!)
+ (alias-value operand-alias-value set-operand-alias-value!))
+
+(define* (make-operand var sym #:optional source visit alias)
+ ;; Bind SYM to VAR, with value SOURCE. Unassigned bound operands are
+ ;; considered copyable until we prove otherwise. If we have a source
+ ;; expression, truncate it to one value. Copy propagation does not
+ ;; work on multiply-valued expressions.
+ (let ((source (and=> source truncate-values)))
+ (%make-operand var sym visit source 0 0
+ (and source (not (var-set? var))) #f #f
+ (and (not (var-set? var)) alias))))
+
+(define* (make-bound-operands vars syms sources visit #:optional aliases)
+ (if aliases
+ (map (lambda (name sym source alias)
+ (make-operand name sym source visit alias))
+ vars syms sources aliases)
+ (map (lambda (name sym source)
+ (make-operand name sym source visit #f))
+ vars syms sources)))
+
+(define (make-unbound-operands vars syms)
+ (map make-operand vars syms))
+
+(define (set-operand-residual-value! op val)
+ (%set-operand-residual-value!
+ op
+ (match val
+ (($ <primcall> src 'values (first))
+ ;; The continuation of a residualized binding does not need the
+ ;; introduced `values' node, so undo the effects of truncation.
+ first)
+ (else
+ val))))
+
+(define* (visit-operand op counter ctx #:optional effort-limit size-limit)
+ ;; Peval is O(N) in call sites of the source program. However,
+ ;; visiting an operand can introduce new call sites. If we visit an
+ ;; operand outside a counter -- i.e., outside an inlining attempt --
+ ;; this can lead to divergence. So, if we are visiting an operand to
+ ;; try to copy it, and there is no counter, make a new one.
+ ;;
+ ;; This will only happen at most as many times as there are lexical
+ ;; references in the source program.
+ (and (zero? (operand-visit-count op))
+ (dynamic-wind
+ (lambda ()
+ (set-operand-visit-count! op (1+ (operand-visit-count op))))
+ (lambda ()
+ (and (operand-source op)
+ (if (or counter (and (not effort-limit) (not size-limit)))
+ ((%operand-visit op) (operand-source op) counter ctx)
+ (let/ec k
+ (define (abort)
+ ;; If we abort when visiting the value in a
+ ;; fresh context, we won't succeed in any future
+ ;; attempt, so don't try to copy it again.
+ (set-operand-copyable?! op #f)
+ (k #f))
+ ((%operand-visit op)
+ (operand-source op)
+ (make-top-counter effort-limit size-limit abort op)
+ ctx)))))
+ (lambda ()
+ (set-operand-visit-count! op (1- (operand-visit-count op)))))))
+
+;; A helper for constant folding.
+;;
(define (types-check? primitive-name args)
(case primitive-name
((values) #t)
;; FIXME: add more cases?
(else #f)))
-(define (fresh-gensyms syms)
- (map (lambda (x) (gensym (string-append (symbol->string x) " ")))
- syms))
-
-;; Copy propagation of terms that bind variables, like `lambda' terms,
-;; will need to bind fresh variables. This procedure renames all the
-;; lexicals in a term.
-;;
-(define (alpha-rename exp)
- "Alpha-rename EXP. For any lambda in EXP, generate new symbols and
-replace all lexical references to the former symbols with lexical
-references to the new symbols."
- ;; XXX: This should be factorized somehow.
- (let loop ((exp exp)
- (mapping vlist-null)) ; maps old to new gensyms
- (match exp
- (($ <lambda-case> src req opt rest kw inits gensyms body alt)
- ;; Create new symbols to replace GENSYMS and propagate them down
- ;; in BODY and ALT.
- (let* ((new (fresh-gensyms
- (append req
- (or opt '())
- (if rest (list rest) '())
- (match kw
- ((aok? (_ name _) ...) name)
- (_ '())))))
- (mapping (fold vhash-consq mapping gensyms new)))
- (make-lambda-case src req opt rest
- (match kw
- ((aok? (kw name old) ...)
- (cons aok? (map list
- kw
- name
- (take-right new (length old)))))
- (_ #f))
- (map (cut loop <> mapping) inits)
- new
- (loop body mapping)
- (and alt (loop alt mapping)))))
- (($ <lexical-ref> src name gensym)
- ;; Possibly replace GENSYM by the new gensym defined in MAPPING.
- (let ((val (vhash-assq gensym mapping)))
- (if val
- (make-lexical-ref src name (cdr val))
- exp)))
- (($ <lexical-set> src name gensym exp)
- (let ((val (vhash-assq gensym mapping)))
- (make-lexical-set src name (if val (cdr val) gensym)
- (loop exp mapping))))
- (($ <lambda> src meta body)
- (make-lambda src meta (loop body mapping)))
- (($ <let> src names gensyms vals body)
- ;; As for `lambda-case' rename GENSYMS to avoid any collision.
- (let* ((new (fresh-gensyms names))
- (mapping (fold vhash-consq mapping gensyms new))
- (vals (map (cut loop <> mapping) vals))
- (body (loop body mapping)))
- (make-let src names new vals body)))
- (($ <letrec> src in-order? names gensyms vals body)
- ;; Likewise.
- (let* ((new (fresh-gensyms names))
- (mapping (fold vhash-consq mapping gensyms new))
- (vals (map (cut loop <> mapping) vals))
- (body (loop body mapping)))
- (make-letrec src in-order? names new vals body)))
- (($ <fix> src names gensyms vals body)
- ;; Likewise.
- (let* ((new (fresh-gensyms names))
- (mapping (fold vhash-consq mapping gensyms new))
- (vals (map (cut loop <> mapping) vals))
- (body (loop body mapping)))
- (make-fix src names new vals body)))
- (($ <let-values> src exp body)
- (make-let-values src (loop exp mapping) (loop body mapping)))
- (($ <const>)
- exp)
- (($ <void>)
- exp)
- (($ <toplevel-ref>)
- exp)
- (($ <module-ref>)
- exp)
- (($ <primitive-ref>)
- exp)
- (($ <toplevel-set> src name exp)
- (make-toplevel-set src name (loop exp mapping)))
- (($ <toplevel-define> src name exp)
- (make-toplevel-define src name (loop exp mapping)))
- (($ <module-set> src mod name public? exp)
- (make-module-set src mod name public? (loop exp mapping)))
- (($ <dynlet> src fluids vals body)
- (make-dynlet src
- (map (cut loop <> mapping) fluids)
- (map (cut loop <> mapping) vals)
- (loop body mapping)))
- (($ <dynwind> src winder body unwinder)
- (make-dynwind src
- (loop winder mapping)
- (loop body mapping)
- (loop unwinder mapping)))
- (($ <dynref> src fluid)
- (make-dynref src (loop fluid mapping)))
- (($ <dynset> src fluid exp)
- (make-dynset src (loop fluid mapping) (loop exp mapping)))
- (($ <conditional> src condition subsequent alternate)
- (make-conditional src
- (loop condition mapping)
- (loop subsequent mapping)
- (loop alternate mapping)))
- (($ <application> src proc args)
- (make-application src (loop proc mapping)
- (map (cut loop <> mapping) args)))
- (($ <sequence> src exps)
- (make-sequence src (map (cut loop <> mapping) exps)))
- (($ <prompt> src tag body handler)
- (make-prompt src (loop tag mapping) (loop body mapping)
- (loop handler mapping)))
- (($ <abort> src tag args tail)
- (make-abort src (loop tag mapping) (map (cut loop <> mapping) args)
- (loop tail mapping))))))
-
(define* (peval exp #:optional (cenv (current-module)) (env vlist-null)
#:key
(operator-size-limit 40)
(define local-toplevel-env
;; The top-level environment of the module being compiled.
- (match exp
- (($ <toplevel-define> _ name)
- (vhash-consq name #t env))
- (($ <sequence> _ exps)
- (fold (lambda (x r)
- (match x
- (($ <toplevel-define> _ name)
- (vhash-consq name #t r))
- (_ r)))
- env
- exps))
- (_ env)))
+ (let ()
+ (define (env-folder x env)
+ (match x
+ (($ <toplevel-define> _ name)
+ (vhash-consq name #t env))
+ (($ <seq> _ head tail)
+ (env-folder tail (env-folder head env)))
+ (_ env)))
+ (env-folder exp vlist-null)))
(define (local-toplevel? name)
(vhash-assq name local-toplevel-env))
;;
(define store (build-var-table exp))
- (define (assigned-lexical? sym)
+ (define (record-new-temporary! name sym refcount)
+ (set! store (vhash-consq sym (make-var name sym refcount #f) store)))
+
+ (define (lookup-var sym)
(let ((v (vhash-assq sym store)))
- (and v (var-set? (cdr v)))))
+ (if v (cdr v) (error "unbound var" sym (vlist->list store)))))
+
+ (define (fresh-gensyms vars)
+ (map (lambda (var)
+ (let ((new (gensym (string-append (symbol->string (var-name var))
+ " "))))
+ (set! store (vhash-consq new var store))
+ new))
+ vars))
+
+ (define (fresh-temporaries ls)
+ (map (lambda (elt)
+ (let ((new (gensym "tmp ")))
+ (record-new-temporary! 'tmp new 1)
+ new))
+ ls))
+
+ (define (assigned-lexical? sym)
+ (var-set? (lookup-var sym)))
(define (lexical-refcount sym)
- (let ((v (vhash-assq sym store)))
- (if v (var-refcount (cdr v)) 0)))
+ (var-refcount (lookup-var sym)))
;; ORIG has been alpha-renamed to NEW. Analyze NEW and record a link
;; from it to ORIG.
;;
(define (record-source-expression! orig new)
- (set! store (vhash-consq new
- (source-expression orig)
- (build-var-table new store)))
+ (set! store (vhash-consq new (source-expression orig) store))
new)
;; Find the source expression corresponding to NEW. Used to detect
(let ((x (vhash-assq new store)))
(if x (cdr x) new)))
- (define residual-lexical-references (make-hash-table))
+ (define (record-operand-use op)
+ (set-operand-use-count! op (1+ (operand-use-count op))))
- (define (record-residual-lexical-reference! sym)
- (hashq-set! residual-lexical-references sym #t))
+ (define (unrecord-operand-uses op n)
+ (let ((count (- (operand-use-count op) n)))
+ (when (zero? count)
+ (set-operand-residual-value! op #f))
+ (set-operand-use-count! op count)))
- (define (apply-primitive name args)
- ;; todo: further optimize commutative primitives
- (catch #t
- (lambda ()
- (call-with-values
- (lambda ()
- (apply (module-ref the-scm-module name) args))
- (lambda results
- (values #t results))))
- (lambda _
- (values #f '()))))
+ (define* (residualize-lexical op #:optional ctx val)
+ (log 'residualize op)
+ (record-operand-use op)
+ (if (memq ctx '(value values))
+ (set-operand-residual-value! op val))
+ (make-lexical-ref #f (var-name (operand-var op)) (operand-sym op)))
+
+ (define (fold-constants src name args ctx)
+ (define (apply-primitive name args)
+ ;; todo: further optimize commutative primitives
+ (catch #t
+ (lambda ()
+ (call-with-values
+ (lambda ()
+ (apply (module-ref the-scm-module name) args))
+ (lambda results
+ (values #t results))))
+ (lambda _
+ (values #f '()))))
+ (define (make-values src values)
+ (match values
+ ((single) single) ; 1 value
+ ((_ ...) ; 0, or 2 or more values
+ (make-primcall src 'values values))))
+ (define (residualize-call)
+ (make-primcall src name args))
+ (cond
+ ((every const? args)
+ (let-values (((success? values)
+ (apply-primitive name (map const-exp args))))
+ (log 'fold success? values name args)
+ (if success?
+ (case ctx
+ ((effect) (make-void src))
+ ((test)
+ ;; Values truncation: only take the first
+ ;; value.
+ (if (pair? values)
+ (make-const src (car values))
+ (make-values src '())))
+ (else
+ (make-values src (map (cut make-const src <>) values))))
+ (residualize-call))))
+ ((and (eq? ctx 'effect) (types-check? name args))
+ (make-void #f))
+ (else
+ (residualize-call))))
- (define (inline-values exp src names gensyms body)
+ (define (inline-values src exp nmin nmax consumer)
(let loop ((exp exp))
(match exp
;; Some expression types are always singly-valued.
($ <toplevel-set>) ; could return zero values in
($ <toplevel-define>) ; the future
($ <module-set>) ;
- ($ <dynset>)) ;
- (and (= (length names) 1)
- (make-let src names gensyms (list exp) body)))
- (($ <application> src
- ($ <primitive-ref> _ (? singly-valued-primitive? name)))
- (and (= (length names) 1)
- (make-let src names gensyms (list exp) body)))
+ ($ <dynset>) ;
+ ($ <primcall> src (? singly-valued-primitive?)))
+ (and (<= nmin 1) (or (not nmax) (>= nmax 1))
+ (make-call src (make-lambda #f '() consumer) (list exp))))
;; Statically-known number of values.
- (($ <application> src ($ <primitive-ref> _ 'values) vals)
- (and (= (length names) (length vals))
- (make-let src names gensyms vals body)))
+ (($ <primcall> src 'values vals)
+ (and (<= nmin (length vals)) (or (not nmax) (>= nmax (length vals)))
+ (make-call src (make-lambda #f '() consumer) vals)))
;; Not going to copy code into both branches.
(($ <conditional>) #f)
;; Bail on other applications.
- (($ <application>) #f)
+ (($ <call>) #f)
+ (($ <primcall>) #f)
;; Bail on prompt and abort.
(($ <prompt>) #f)
(make-let-values src exp
(make-lambda-case src2 req opt rest kw
inits gensyms body #f)))))
- (($ <dynwind> src winder body unwinder)
+ (($ <dynwind> src winder pre body post unwinder)
(let ((body (loop body)))
(and body
- (make-dynwind src winder body unwinder))))
+ (make-dynwind src winder pre body post unwinder))))
(($ <dynlet> src fluids vals body)
(let ((body (loop body)))
(and body
(make-dynlet src fluids vals body))))
- (($ <sequence> src exps)
- (match exps
- ((head ... tail)
- (let ((tail (loop tail)))
- (and tail
- (make-sequence src (append head (list tail)))))))))))
-
- (define (make-values src values)
- (match values
- ((single) single) ; 1 value
- ((_ ...) ; 0, or 2 or more values
- (make-application src (make-primitive-ref src 'values)
- values))))
+ (($ <seq> src head tail)
+ (let ((tail (loop tail)))
+ (and tail (make-seq src head tail)))))))
+
+ (define compute-effects
+ (make-effects-analyzer assigned-lexical?))
(define (constant-expression? x)
- ;; Return true if X is constant---i.e., if it is known to have no
- ;; effects, does not allocate storage for a mutable object, and does
- ;; not access mutable data (like `car' or toplevel references).
- (let loop ((x x))
- (match x
- (($ <void>) #t)
- (($ <const>) #t)
- (($ <lambda>) #t)
- (($ <lambda-case> _ req opt rest kw inits _ body alternate)
- (and (every loop inits) (loop body)
- (or (not alternate) (loop alternate))))
- (($ <lexical-ref> _ _ gensym)
- (not (assigned-lexical? gensym)))
- (($ <primitive-ref>) #t)
- (($ <conditional> _ condition subsequent alternate)
- (and (loop condition) (loop subsequent) (loop alternate)))
- (($ <application> _ ($ <primitive-ref> _ name) args)
- (and (effect-free-primitive? name)
- (not (constructor-primitive? name))
- (types-check? name args)
- (every loop args)))
- (($ <application> _ ($ <lambda> _ _ body) args)
- (and (loop body) (every loop args)))
- (($ <sequence> _ exps)
- (every loop exps))
- (($ <let> _ _ _ vals body)
- (and (every loop vals) (loop body)))
- (($ <letrec> _ _ _ _ vals body)
- (and (every loop vals) (loop body)))
- (($ <fix> _ _ _ vals body)
- (and (every loop vals) (loop body)))
- (($ <let-values> _ exp body)
- (and (loop exp) (loop body)))
- (($ <prompt> _ tag body handler)
- (and (loop tag) (loop body) (loop handler)))
- (_ #f))))
-
- (define (prune-bindings names syms vals body for-effect
- build-result)
- (let lp ((names names) (syms syms) (vals vals)
- (names* '()) (syms* '()) (vals* '())
- (effects '()))
- (match (list names syms vals)
- ((() () ())
- (let ((body (if (null? effects)
- body
- (make-sequence #f (reverse (cons body effects))))))
- (if (null? names*)
+ ;; Return true if X is constant, for the purposes of copying or
+ ;; elision---i.e., if it is known to have no effects, does not
+ ;; allocate storage for a mutable object, and does not access
+ ;; mutable data (like `car' or toplevel references).
+ (constant? (compute-effects x)))
+
+ (define (prune-bindings ops in-order? body counter ctx build-result)
+ ;; This helper handles both `let' and `letrec'/`fix'. In the latter
+ ;; cases we need to make sure that if referenced binding A needs
+ ;; as-yet-unreferenced binding B, that B is processed for value.
+ ;; Likewise if C, when processed for effect, needs otherwise
+ ;; unreferenced D, then D needs to be processed for value too.
+ ;;
+ (define (referenced? op)
+ ;; When we visit lambdas in operator context, we just copy them,
+ ;; as we will process their body later. However this does have
+ ;; the problem that any free var referenced by the lambda is not
+ ;; marked as needing residualization. Here we hack around this
+ ;; and treat all bindings as referenced if we are in operator
+ ;; context.
+ (or (eq? ctx 'operator)
+ (not (zero? (operand-use-count op)))))
+
+ ;; values := (op ...)
+ ;; effects := (op ...)
+ (define (residualize values effects)
+ ;; Note, values and effects are reversed.
+ (cond
+ (in-order?
+ (let ((values (filter operand-residual-value ops)))
+ (if (null? values)
+ body
+ (build-result (map (compose var-name operand-var) values)
+ (map operand-sym values)
+ (map operand-residual-value values)
+ body))))
+ (else
+ (let ((body
+ (if (null? effects)
+ body
+ (let ((effect-vals (map operand-residual-value effects)))
+ (list->seq #f (reverse (cons body effect-vals)))))))
+ (if (null? values)
body
- (build-result (reverse names*) (reverse syms*)
- (reverse vals*) body))))
- (((name . names) (sym . syms) (val . vals))
- (if (hashq-ref residual-lexical-references sym)
- (lp names syms vals
- (cons name names*) (cons sym syms*) (cons val vals*)
- effects)
- (let ((effect (for-effect val)))
- (lp names syms vals
- names* syms* vals*
- (if (void? effect)
- (begin
- (log 'prune sym)
- effects)
- (cons effect effects)))))))))
+ (let ((values (reverse values)))
+ (build-result (map (compose var-name operand-var) values)
+ (map operand-sym values)
+ (map operand-residual-value values)
+ body)))))))
+
+ ;; old := (bool ...)
+ ;; values := (op ...)
+ ;; effects := ((op . value) ...)
+ (let prune ((old (map referenced? ops)) (values '()) (effects '()))
+ (let lp ((ops* ops) (values values) (effects effects))
+ (cond
+ ((null? ops*)
+ (let ((new (map referenced? ops)))
+ (if (not (equal? new old))
+ (prune new values '())
+ (residualize values
+ (map (lambda (op val)
+ (set-operand-residual-value! op val)
+ op)
+ (map car effects) (map cdr effects))))))
+ (else
+ (let ((op (car ops*)))
+ (cond
+ ((memq op values)
+ (lp (cdr ops*) values effects))
+ ((operand-residual-value op)
+ (lp (cdr ops*) (cons op values) effects))
+ ((referenced? op)
+ (set-operand-residual-value! op (visit-operand op counter 'value))
+ (lp (cdr ops*) (cons op values) effects))
+ (else
+ (lp (cdr ops*)
+ values
+ (let ((effect (visit-operand op counter 'effect)))
+ (if (void? effect)
+ effects
+ (acons op effect effects))))))))))))
(define (small-expression? x limit)
(let/ec k
0 x)
#t))
+ (define (extend-env sym op env)
+ (vhash-consq (operand-sym op) op (vhash-consq sym op env)))
+
(let loop ((exp exp)
- (env vlist-null) ; static environment
+ (env vlist-null) ; vhash of gensym -> <operand>
(counter #f) ; inlined call stack
- (ctx 'value)) ; effect, value, test, operator, or operand
+ (ctx 'values)) ; effect, value, values, test, operator, or call
(define (lookup var)
- (and=> (vhash-assq var env) cdr))
+ (cond
+ ((vhash-assq var env) => cdr)
+ (else (error "unbound var" var))))
+
+ ;; Find a value referenced a specific number of times. This is a hack
+ ;; that's used for propagating fresh data structures like rest lists and
+ ;; prompt tags. Usually we wouldn't copy consed data, but we can do so in
+ ;; some special cases like `apply' or prompts if we can account
+ ;; for all of its uses.
+ ;;
+ ;; You don't want to use this in general because it introduces a slight
+ ;; nonlinearity by running peval again (though with a small effort and size
+ ;; counter).
+ ;;
+ (define (find-definition x n-aliases)
+ (cond
+ ((lexical-ref? x)
+ (cond
+ ((lookup (lexical-ref-gensym x))
+ => (lambda (op)
+ (let ((y (or (operand-residual-value op)
+ (visit-operand op counter 'value 10 10)
+ (operand-source op))))
+ (cond
+ ((and (lexical-ref? y)
+ (= (lexical-refcount (lexical-ref-gensym x)) 1))
+ ;; X is a simple alias for Y. Recurse, regardless of
+ ;; the number of aliases we were expecting.
+ (find-definition y n-aliases))
+ ((= (lexical-refcount (lexical-ref-gensym x)) n-aliases)
+ ;; We found a definition that is aliased the right
+ ;; number of times. We still recurse in case it is a
+ ;; lexical.
+ (values (find-definition y 1)
+ op))
+ (else
+ ;; We can't account for our aliases.
+ (values #f #f))))))
+ (else
+ ;; A formal parameter. Can't say anything about that.
+ (values #f #f))))
+ ((= n-aliases 1)
+ ;; Not a lexical: success, but only if we are looking for an
+ ;; unaliased value.
+ (values x #f))
+ (else (values #f #f))))
(define (visit exp ctx)
(loop exp env counter ctx))
(define (for-value exp) (visit exp 'value))
- (define (for-operand exp) (visit exp 'operand))
+ (define (for-values exp) (visit exp 'values))
(define (for-test exp) (visit exp 'test))
(define (for-effect exp) (visit exp 'effect))
+ (define (for-call exp) (visit exp 'call))
(define (for-tail exp) (visit exp ctx))
(if counter
((test) (make-const #f #t))
(else exp)))
(($ <lexical-ref> _ _ gensym)
- (case ctx
- ((effect) (make-void #f))
- (else
- (log 'begin-copy gensym)
- (let ((val (lookup gensym)))
- (cond
- ((or (not val)
- (assigned-lexical? gensym)
- (not (constant-expression? val)))
- ;; Don't copy-propagate through assigned variables,
- ;; and don't reorder effects.
- (log 'unbound-or-not-constant gensym val)
- (record-residual-lexical-reference! gensym)
- exp)
- ((lexical-ref? val)
- (for-tail val))
- ((or (const? val)
- (void? val)
- (primitive-ref? val))
- ;; Always propagate simple values that cannot lead to
- ;; code bloat.
- (log 'copy-simple gensym val)
- (for-tail val))
- ((= 1 (lexical-refcount gensym))
- ;; Always propagate values referenced only once.
- ;; There is no need to rename the bindings, as they
- ;; are only being moved, not copied. However in
- ;; operator context we do rename it, as that
- ;; effectively clears out the residualized-lexical
- ;; flags that may have been set when this value was
- ;; visited previously as an operand.
- (log 'copy-single gensym val)
- (case ctx
- ((test) (for-test val))
- ((operator) (record-source-expression! val (alpha-rename val)))
- (else val)))
- ;; FIXME: do demand-driven size accounting rather than
- ;; these heuristics.
- ((eq? ctx 'operator)
- ;; A pure expression in the operator position. Inline
- ;; if it's a lambda that's small enough.
- (if (and (lambda? val)
- (small-expression? val operator-size-limit))
- (begin
- (log 'copy-operator gensym val)
- (record-source-expression! val (alpha-rename val)))
- (begin
- (log 'too-big-for-operator gensym val)
- (record-residual-lexical-reference! gensym)
- exp)))
- ((eq? ctx 'operand)
- ;; A pure expression in the operand position. Inline
- ;; if it's small enough.
- (if (small-expression? val operand-size-limit)
- (begin
- (log 'copy-operand gensym val)
- (record-source-expression! val (alpha-rename val)))
- (begin
- (log 'too-big-for-operand gensym val)
- (record-residual-lexical-reference! gensym)
- exp)))
- (else
- ;; A pure expression, processed for value. Don't
- ;; inline lambdas, because they will probably won't
- ;; fold because we don't know the operator.
- (if (and (small-expression? val value-size-limit)
- (not (tree-il-any lambda? val)))
- (begin
- (log 'copy-value gensym val)
- (record-source-expression! val (alpha-rename val)))
- (begin
- (log 'too-big-or-has-lambda gensym val)
- (record-residual-lexical-reference! gensym)
- exp))))))))
+ (log 'begin-copy gensym)
+ (let ((op (lookup gensym)))
+ (cond
+ ((eq? ctx 'effect)
+ (log 'lexical-for-effect gensym)
+ (make-void #f))
+ ((operand-alias-value op)
+ ;; This is an unassigned operand that simply aliases some
+ ;; other operand. Recurse to avoid residualizing the leaf
+ ;; binding.
+ => for-tail)
+ ((eq? ctx 'call)
+ ;; Don't propagate copies if we are residualizing a call.
+ (log 'residualize-lexical-call gensym op)
+ (residualize-lexical op))
+ ((var-set? (operand-var op))
+ ;; Assigned lexicals don't copy-propagate.
+ (log 'assigned-var gensym op)
+ (residualize-lexical op))
+ ((not (operand-copyable? op))
+ ;; We already know that this operand is not copyable.
+ (log 'not-copyable gensym op)
+ (residualize-lexical op))
+ ((and=> (operand-constant-value op)
+ (lambda (x) (or (const? x) (void? x) (primitive-ref? x))))
+ ;; A cache hit.
+ (let ((val (operand-constant-value op)))
+ (log 'memoized-constant gensym val)
+ (for-tail val)))
+ ((visit-operand op counter (if (eq? ctx 'values) 'value ctx)
+ recursive-effort-limit operand-size-limit)
+ =>
+ ;; If we end up deciding to residualize this value instead of
+ ;; copying it, save that residualized value.
+ (lambda (val)
+ (cond
+ ((not (constant-expression? val))
+ (log 'not-constant gensym op)
+ ;; At this point, ctx is operator, test, or value. A
+ ;; value that is non-constant in one context will be
+ ;; non-constant in the others, so it's safe to record
+ ;; that here, and avoid future visits.
+ (set-operand-copyable?! op #f)
+ (residualize-lexical op ctx val))
+ ((or (const? val)
+ (void? val)
+ (primitive-ref? val))
+ ;; Always propagate simple values that cannot lead to
+ ;; code bloat.
+ (log 'copy-simple gensym val)
+ ;; It could be this constant is the result of folding.
+ ;; If that is the case, cache it. This helps loop
+ ;; unrolling get farther.
+ (if (or (eq? ctx 'value) (eq? ctx 'values))
+ (begin
+ (log 'memoize-constant gensym val)
+ (set-operand-constant-value! op val)))
+ val)
+ ((= 1 (var-refcount (operand-var op)))
+ ;; Always propagate values referenced only once.
+ (log 'copy-single gensym val)
+ val)
+ ;; FIXME: do demand-driven size accounting rather than
+ ;; these heuristics.
+ ((eq? ctx 'operator)
+ ;; A pure expression in the operator position. Inline
+ ;; if it's a lambda that's small enough.
+ (if (and (lambda? val)
+ (small-expression? val operator-size-limit))
+ (begin
+ (log 'copy-operator gensym val)
+ val)
+ (begin
+ (log 'too-big-for-operator gensym val)
+ (residualize-lexical op ctx val))))
+ (else
+ ;; A pure expression, processed for call or for value.
+ ;; Don't inline lambdas, because they will probably won't
+ ;; fold because we don't know the operator.
+ (if (and (small-expression? val value-size-limit)
+ (not (tree-il-any lambda? val)))
+ (begin
+ (log 'copy-value gensym val)
+ val)
+ (begin
+ (log 'too-big-or-has-lambda gensym val)
+ (residualize-lexical op ctx val)))))))
+ (else
+ ;; Visit failed. Either the operand isn't bound, as in
+ ;; lambda formal parameters, or the copy was aborted.
+ (log 'unbound-or-aborted gensym op)
+ (residualize-lexical op)))))
(($ <lexical-set> src name gensym exp)
- (if (zero? (lexical-refcount gensym))
- (let ((exp (for-effect exp)))
- (if (void? exp)
- exp
- (make-sequence src (list exp (make-void #f)))))
- (begin
- (record-residual-lexical-reference! gensym)
- (make-lexical-set src name gensym (for-value exp)))))
+ (let ((op (lookup gensym)))
+ (if (zero? (var-refcount (operand-var op)))
+ (let ((exp (for-effect exp)))
+ (if (void? exp)
+ exp
+ (make-seq src exp (make-void #f))))
+ (begin
+ (record-operand-use op)
+ (make-lexical-set src name (operand-sym op) (for-value exp))))))
+ (($ <let> src
+ (names ... rest)
+ (gensyms ... rest-sym)
+ (vals ... ($ <primcall> _ 'list rest-args))
+ ($ <primcall> asrc (or 'apply '@apply)
+ (proc args ...
+ ($ <lexical-ref> _
+ (? (cut eq? <> rest))
+ (? (lambda (sym)
+ (and (eq? sym rest-sym)
+ (= (lexical-refcount sym) 1))))))))
+ (let* ((tmps (make-list (length rest-args) 'tmp))
+ (tmp-syms (fresh-temporaries tmps)))
+ (for-tail
+ (make-let src
+ (append names tmps)
+ (append gensyms tmp-syms)
+ (append vals rest-args)
+ (make-call
+ asrc
+ proc
+ (append args
+ (map (cut make-lexical-ref #f <> <>)
+ tmps tmp-syms)))))))
(($ <let> src names gensyms vals body)
- (let* ((vals (map for-operand vals))
- (body (loop body
- (fold vhash-consq env gensyms vals)
- counter
- ctx)))
+ (define (compute-alias exp)
+ ;; It's very common for macros to introduce something like:
+ ;;
+ ;; ((lambda (x y) ...) x-exp y-exp)
+ ;;
+ ;; In that case you might end up trying to inline something like:
+ ;;
+ ;; (let ((x x-exp) (y y-exp)) ...)
+ ;;
+ ;; But if x-exp is itself a lexical-ref that aliases some much
+ ;; larger expression, perhaps it will fail to inline due to
+ ;; size. However we don't want to introduce a useless alias
+ ;; (in this case, x). So if the RHS of a let expression is a
+ ;; lexical-ref, we record that expression. If we end up having
+ ;; to residualize X, then instead we residualize X-EXP, as long
+ ;; as it isn't assigned.
+ ;;
+ (match exp
+ (($ <lexical-ref> _ _ sym)
+ (let ((op (lookup sym)))
+ (and (not (var-set? (operand-var op)))
+ (or (operand-alias-value op)
+ exp))))
+ (_ #f)))
+
+ (let* ((vars (map lookup-var gensyms))
+ (new (fresh-gensyms vars))
+ (ops (make-bound-operands vars new vals
+ (lambda (exp counter ctx)
+ (loop exp env counter ctx))
+ (map compute-alias vals)))
+ (env (fold extend-env env gensyms ops))
+ (body (loop body env counter ctx)))
(cond
((const? body)
- (for-tail (make-sequence src (append vals (list body)))))
+ (for-tail (list->seq src (append vals (list body)))))
((and (lexical-ref? body)
- (memq (lexical-ref-gensym body) gensyms))
+ (memq (lexical-ref-gensym body) new))
(let ((sym (lexical-ref-gensym body))
- (pairs (map cons gensyms vals)))
+ (pairs (map cons new vals)))
;; (let ((x foo) (y bar) ...) x) => (begin bar ... foo)
(for-tail
- (make-sequence
+ (list->seq
src
(append (map cdr (alist-delete sym pairs eq?))
(list (assq-ref pairs sym)))))))
(else
;; Only include bindings for which lexical references
;; have been residualized.
- (prune-bindings names gensyms vals body for-effect
+ (prune-bindings ops #f body counter ctx
(lambda (names gensyms vals body)
(if (null? names) (error "what!" names))
(make-let src names gensyms vals body)))))))
(($ <letrec> src in-order? names gensyms vals body)
- ;; Things could be done more precisely when IN-ORDER? but
- ;; it's OK not to do it---at worst we lost an optimization
- ;; opportunity.
- (let* ((vals (map for-operand vals))
- (body (loop body
- (fold vhash-consq env gensyms vals)
- counter
- ctx)))
- (if (and (const? body)
- (every constant-expression? vals))
- body
- (prune-bindings names gensyms vals body for-effect
+ ;; Note the difference from the `let' case: here we use letrec*
+ ;; so that the `visit' procedure for the new operands closes over
+ ;; an environment that includes the operands. Also we don't try
+ ;; to elide aliases, because we can't sensibly reduce something
+ ;; like (letrec ((a b) (b a)) a).
+ (letrec* ((visit (lambda (exp counter ctx)
+ (loop exp env* counter ctx)))
+ (vars (map lookup-var gensyms))
+ (new (fresh-gensyms vars))
+ (ops (make-bound-operands vars new vals visit))
+ (env* (fold extend-env env gensyms ops))
+ (body* (visit body counter ctx)))
+ (if (and (const? body*) (every constant-expression? vals))
+ ;; We may have folded a loop completely, even though there
+ ;; might be cyclical references between the bound values.
+ ;; Handle this degenerate case specially.
+ body*
+ (prune-bindings ops in-order? body* counter ctx
(lambda (names gensyms vals body)
(make-letrec src in-order?
names gensyms vals body))))))
(($ <fix> src names gensyms vals body)
- (let* ((vals (map for-operand vals))
- (body (loop body
- (fold vhash-consq env gensyms vals)
- counter
- ctx)))
- (if (const? body)
- body
- (prune-bindings names gensyms vals body for-effect
+ (letrec* ((visit (lambda (exp counter ctx)
+ (loop exp env* counter ctx)))
+ (vars (map lookup-var gensyms))
+ (new (fresh-gensyms vars))
+ (ops (make-bound-operands vars new vals visit))
+ (env* (fold extend-env env gensyms ops))
+ (body* (visit body counter ctx)))
+ (if (const? body*)
+ body*
+ (prune-bindings ops #f body* counter ctx
(lambda (names gensyms vals body)
(make-fix src names gensyms vals body))))))
(($ <let-values> lv-src producer consumer)
;; Peval the producer, then try to inline the consumer into
;; the producer. If that succeeds, peval again. Otherwise
;; reconstruct the let-values, pevaling the consumer.
- (let ((producer (for-value producer)))
+ (let ((producer (for-values producer)))
(or (match consumer
- (($ <lambda-case> src req #f #f #f () gensyms body #f)
- (cond
- ((inline-values producer src req gensyms body)
- => for-tail)
- (else #f)))
+ (($ <lambda-case> src req opt rest #f inits gensyms body #f)
+ (let* ((nmin (length req))
+ (nmax (and (not rest) (+ nmin (if opt (length opt) 0)))))
+ (cond
+ ((inline-values lv-src producer nmin nmax consumer)
+ => for-tail)
+ (else #f))))
(_ #f))
(make-let-values lv-src producer (for-tail consumer)))))
- (($ <dynwind> src winder body unwinder)
- (make-dynwind src (for-value winder) (for-tail body)
- (for-value unwinder)))
+ (($ <dynwind> src winder pre body post unwinder)
+ (make-dynwind src (for-value winder) (for-effect pre)
+ (for-tail body)
+ (for-effect post) (for-value unwinder)))
(($ <dynlet> src fluids vals body)
(make-dynlet src (map for-value fluids) (map for-value vals)
(for-tail body)))
(($ <dynset> src fluid exp)
(make-dynset src (for-value fluid) (for-value exp)))
(($ <toplevel-ref> src (? effect-free-primitive? name))
- (if (local-toplevel? name)
- exp
- (resolve-primitives! exp cenv)))
+ exp)
(($ <toplevel-ref>)
;; todo: open private local bindings.
exp)
((test) (make-const #f #t))
(else exp)))
(($ <conditional> src condition subsequent alternate)
- (let ((condition (for-test condition)))
- (if (const? condition)
- (if (const-exp condition)
- (for-tail subsequent)
- (for-tail alternate))
- (make-conditional src condition
- (for-tail subsequent)
- (for-tail alternate)))))
- (($ <application> src
- ($ <primitive-ref> _ '@call-with-values)
+ (define (call-with-failure-thunk exp proc)
+ (match exp
+ (($ <call> _ _ ()) (proc exp))
+ (($ <primcall> _ _ ()) (proc exp))
+ (($ <const>) (proc exp))
+ (($ <void>) (proc exp))
+ (($ <lexical-ref>) (proc exp))
+ (_
+ (let ((t (gensym "failure-")))
+ (record-new-temporary! 'failure t 2)
+ (make-let
+ src (list 'failure) (list t)
+ (list
+ (make-lambda
+ #f '()
+ (make-lambda-case #f '() #f #f #f '() '() exp #f)))
+ (proc (make-call #f (make-lexical-ref #f 'failure t)
+ '())))))))
+ (define (simplify-conditional c)
+ (match c
+ ;; Swap the arms of (if (not FOO) A B), to simplify.
+ (($ <conditional> src ($ <primcall> _ 'not (pred))
+ subsequent alternate)
+ (simplify-conditional
+ (make-conditional src pred alternate subsequent)))
+ ;; Special cases for common tests in the predicates of chains
+ ;; of if expressions.
+ (($ <conditional> src
+ ($ <conditional> src* outer-test inner-test ($ <const> _ #f))
+ inner-subsequent
+ alternate)
+ (let lp ((alternate alternate))
+ (match alternate
+ ;; Lift a common repeated test out of a chain of if
+ ;; expressions.
+ (($ <conditional> _ (? (cut tree-il=? outer-test <>))
+ other-subsequent alternate)
+ (make-conditional
+ src outer-test
+ (simplify-conditional
+ (make-conditional src* inner-test inner-subsequent
+ other-subsequent))
+ alternate))
+ ;; Likewise, but punching through any surrounding
+ ;; failure continuations.
+ (($ <let> let-src (name) (sym) ((and thunk ($ <lambda>))) body)
+ (make-let
+ let-src (list name) (list sym) (list thunk)
+ (lp body)))
+ ;; Otherwise, rotate AND tests to expose a simple
+ ;; condition in the front. Although this may result in
+ ;; lexically binding failure thunks, the thunks will be
+ ;; compiled to labels allocation, so there's no actual
+ ;; code growth.
+ (_
+ (call-with-failure-thunk
+ alternate
+ (lambda (failure)
+ (make-conditional
+ src outer-test
+ (simplify-conditional
+ (make-conditional src* inner-test inner-subsequent failure))
+ failure)))))))
+ (_ c)))
+ (match (for-test condition)
+ (($ <const> _ val)
+ (if val
+ (for-tail subsequent)
+ (for-tail alternate)))
+ (c
+ (simplify-conditional
+ (make-conditional src c (for-tail subsequent)
+ (for-tail alternate))))))
+ (($ <primcall> src '@call-with-values
(producer
($ <lambda> _ _
(and consumer
;; No optional or kwargs.
($ <lambda-case>
_ req #f rest #f () gensyms body #f)))))
- (for-tail (make-let-values src (make-application src producer '())
+ (for-tail (make-let-values src (make-call src producer '())
consumer)))
+ (($ <primcall> src 'dynamic-wind (w thunk u))
+ (for-tail
+ (cond
+ ((not (constant-expression? w))
+ (cond
+ ((not (constant-expression? u))
+ (let ((w-sym (gensym "w ")) (u-sym (gensym "u ")))
+ (record-new-temporary! 'w w-sym 2)
+ (record-new-temporary! 'u u-sym 2)
+ (make-let src '(w u) (list w-sym u-sym) (list w u)
+ (make-dynwind
+ src
+ (make-lexical-ref #f 'w w-sym)
+ (make-call #f (make-lexical-ref #f 'w w-sym) '())
+ (make-call #f thunk '())
+ (make-call #f (make-lexical-ref #f 'u u-sym) '())
+ (make-lexical-ref #f 'u u-sym)))))
+ (else
+ (let ((w-sym (gensym "w ")))
+ (record-new-temporary! 'w w-sym 2)
+ (make-let src '(w) (list w-sym) (list w)
+ (make-dynwind
+ src
+ (make-lexical-ref #f 'w w-sym)
+ (make-call #f (make-lexical-ref #f 'w w-sym) '())
+ (make-call #f thunk '())
+ (make-call #f u '())
+ u))))))
+ ((not (constant-expression? u))
+ (let ((u-sym (gensym "u ")))
+ (record-new-temporary! 'u u-sym 2)
+ (make-let src '(u) (list u-sym) (list u)
+ (make-dynwind
+ src
+ w
+ (make-call #f w '())
+ (make-call #f thunk '())
+ (make-call #f (make-lexical-ref #f 'u u-sym) '())
+ (make-lexical-ref #f 'u u-sym)))))
+ (else
+ (make-dynwind src w (make-call #f w '()) (make-call #f thunk '())
+ (make-call #f u '()) u)))))
+
+ (($ <primcall> src 'values exps)
+ (cond
+ ((null? exps)
+ (if (eq? ctx 'effect)
+ (make-void #f)
+ exp))
+ (else
+ (let ((vals (map for-value exps)))
+ (if (and (case ctx
+ ((value test effect) #t)
+ (else (null? (cdr vals))))
+ (every singly-valued-expression? vals))
+ (for-tail (list->seq src (append (cdr vals) (list (car vals)))))
+ (make-primcall src 'values vals))))))
+
+ (($ <primcall> src (or 'apply '@apply) (proc args ... tail))
+ (let lp ((tail* (find-definition tail 1)) (speculative? #t))
+ (define (copyable? x)
+ ;; Inlining a result from find-definition effectively copies it,
+ ;; relying on the let-pruning to remove its original binding. We
+ ;; shouldn't copy non-constant expressions.
+ (or (not speculative?) (constant-expression? x)))
+ (match tail*
+ (($ <const> _ (args* ...))
+ (let ((args* (map (cut make-const #f <>) args*)))
+ (for-tail (make-call src proc (append args args*)))))
+ (($ <primcall> _ 'cons
+ ((and head (? copyable?)) (and tail (? copyable?))))
+ (for-tail (make-primcall src '@apply
+ (cons proc
+ (append args (list head tail))))))
+ (($ <primcall> _ 'list
+ (and args* ((? copyable?) ...)))
+ (for-tail (make-call src proc (append args args*))))
+ (tail*
+ (if speculative?
+ (lp (for-value tail) #f)
+ (let ((args (append (map for-value args) (list tail*))))
+ (make-primcall src '@apply
+ (cons (for-value proc) args))))))))
+
+ (($ <primcall> src (? constructor-primitive? name) args)
+ (cond
+ ((and (memq ctx '(effect test))
+ (match (cons name args)
+ ((or ('cons _ _)
+ ('list . _)
+ ('vector . _)
+ ('make-prompt-tag)
+ ('make-prompt-tag ($ <const> _ (? string?))))
+ #t)
+ (_ #f)))
+ ;; Some expressions can be folded without visiting the
+ ;; arguments for value.
+ (let ((res (if (eq? ctx 'effect)
+ (make-void #f)
+ (make-const #f #t))))
+ (for-tail (list->seq src (append args (list res))))))
+ (else
+ (match (cons name (map for-value args))
+ (('cons x ($ <const> _ (? (cut eq? <> '()))))
+ (make-primcall src 'list (list x)))
+ (('cons x ($ <primcall> _ 'list elts))
+ (make-primcall src 'list (cons x elts)))
+ ((name . args)
+ (make-primcall src name args))))))
+
+ (($ <primcall> src (? accessor-primitive? name) args)
+ (match (cons name (map for-value args))
+ ;; FIXME: these for-tail recursions could take place outside
+ ;; an effort counter.
+ (('car ($ <primcall> src 'cons (head tail)))
+ (for-tail (make-seq src tail head)))
+ (('cdr ($ <primcall> src 'cons (head tail)))
+ (for-tail (make-seq src head tail)))
+ (('car ($ <primcall> src 'list (head . tail)))
+ (for-tail (list->seq src (append tail (list head)))))
+ (('cdr ($ <primcall> src 'list (head . tail)))
+ (for-tail (make-seq src head (make-primcall #f 'list tail))))
+
+ (('car ($ <const> src (head . tail)))
+ (for-tail (make-const src head)))
+ (('cdr ($ <const> src (head . tail)))
+ (for-tail (make-const src tail)))
+ (((or 'memq 'memv) k ($ <const> _ (elts ...)))
+ ;; FIXME: factor
+ (case ctx
+ ((effect)
+ (for-tail
+ (make-seq src k (make-void #f))))
+ ((test)
+ (cond
+ ((const? k)
+ ;; A shortcut. The `else' case would handle it, but
+ ;; this way is faster.
+ (let ((member (case name ((memq) memq) ((memv) memv))))
+ (make-const #f (and (member (const-exp k) elts) #t))))
+ ((null? elts)
+ (for-tail
+ (make-seq src k (make-const #f #f))))
+ (else
+ (let ((t (gensym "t "))
+ (eq (if (eq? name 'memq) 'eq? 'eqv?)))
+ (record-new-temporary! 't t (length elts))
+ (for-tail
+ (make-let
+ src (list 't) (list t) (list k)
+ (let lp ((elts elts))
+ (define test
+ (make-primcall #f eq
+ (list (make-lexical-ref #f 't t)
+ (make-const #f (car elts)))))
+ (if (null? (cdr elts))
+ test
+ (make-conditional src test
+ (make-const #f #t)
+ (lp (cdr elts)))))))))))
+ (else
+ (cond
+ ((const? k)
+ (let ((member (case name ((memq) memq) ((memv) memv))))
+ (make-const #f (member (const-exp k) elts))))
+ ((null? elts)
+ (for-tail (make-seq src k (make-const #f #f))))
+ (else
+ (make-primcall src name (list k (make-const #f elts))))))))
+ ((name . args)
+ (fold-constants src name args ctx))))
+
+ (($ <primcall> src (? equality-primitive? name) (a b))
+ (let ((val-a (for-value a))
+ (val-b (for-value b)))
+ (log 'equality-primitive name val-a val-b)
+ (cond ((and (lexical-ref? val-a) (lexical-ref? val-b)
+ (eq? (lexical-ref-gensym val-a)
+ (lexical-ref-gensym val-b)))
+ (for-tail (make-const #f #t)))
+ (else
+ (fold-constants src name (list val-a val-b) ctx)))))
+
+ (($ <primcall> src (? effect-free-primitive? name) args)
+ (fold-constants src name (map for-value args) ctx))
- (($ <application> src orig-proc orig-args)
+ (($ <primcall> src name args)
+ (make-primcall src name (map for-value args)))
+
+ (($ <call> src orig-proc orig-args)
;; todo: augment the global env with specialized functions
- (let ((proc (loop orig-proc env counter 'operator)))
+ (let revisit-proc ((proc (visit orig-proc 'operator)))
(match proc
- (($ <primitive-ref> _ (? constructor-primitive? name))
- (case ctx
- ((effect test)
- (let ((res (if (eq? ctx 'effect)
- (make-void #f)
- (make-const #f #t))))
- (match (for-value exp)
- (($ <application> _ ($ <primitive-ref> _ 'cons) (x xs))
- (for-tail
- (make-sequence src (list x xs res))))
- (($ <application> _ ($ <primitive-ref> _ 'list) elts)
- (for-tail
- (make-sequence src (append elts (list res)))))
- (($ <application> _ ($ <primitive-ref> _ 'vector) elts)
- (for-tail
- (make-sequence src (append elts (list res)))))
- (($ <application> _ ($ <primitive-ref> _ 'make-prompt-tag) ())
- res)
- (($ <application> _ ($ <primitive-ref> _ 'make-prompt-tag)
- (($ <const> _ (? string?))))
- res)
- (exp exp))))
- (else
- (match (cons name (map for-value orig-args))
- (('cons head tail)
- (match tail
- (($ <const> src ())
- (make-application src (make-primitive-ref #f 'list)
- (list head)))
- (($ <application> src ($ <primitive-ref> _ 'list) elts)
- (make-application src (make-primitive-ref #f 'list)
- (cons head elts)))
- (_ (make-application src proc
- (list head tail)))))
-
- ;; FIXME: these for-tail recursions could take
- ;; place outside an effort counter.
- (('car ($ <application> src ($ <primitive-ref> _ 'cons) (head tail)))
- (for-tail (make-sequence src (list tail head))))
- (('cdr ($ <application> src ($ <primitive-ref> _ 'cons) (head tail)))
- (for-tail (make-sequence src (list head tail))))
- (('car ($ <application> src ($ <primitive-ref> _ 'list) (head . tail)))
- (for-tail (make-sequence src (append tail (list head)))))
- (('cdr ($ <application> src ($ <primitive-ref> _ 'list) (head . tail)))
- (for-tail (make-sequence
- src
- (list head
- (make-application
- src (make-primitive-ref #f 'list) tail)))))
-
- (('car ($ <const> src (head . tail)))
- (for-tail (make-const src head)))
- (('cdr ($ <const> src (head . tail)))
- (for-tail (make-const src tail)))
-
- ((_ . args)
- (make-application src proc args))))))
- (($ <primitive-ref> _ (? effect-free-primitive? name))
- (let ((args (map for-value orig-args)))
- (if (every const? args) ; only simple constants
- (let-values (((success? values)
- (apply-primitive name
- (map const-exp args))))
- (log 'fold success? values exp)
- (if success?
- (case ctx
- ((effect) (make-void #f))
- ((test)
- ;; Values truncation: only take the first
- ;; value.
- (if (pair? values)
- (make-const #f (car values))
- (make-values src '())))
- (else
- (make-values src (map (cut make-const src <>)
- values))))
- (make-application src proc args)))
- (cond
- ((and (eq? ctx 'effect) (types-check? name args))
- (make-void #f))
- (else
- (make-application src proc args))))))
+ (($ <primitive-ref> _ name)
+ (for-tail (make-primcall src name orig-args)))
(($ <lambda> _ _
- ($ <lambda-case> _ req opt #f #f inits gensyms body #f))
- ;; Simple case: no rest, no keyword arguments.
+ ($ <lambda-case> _ req opt rest #f inits gensyms body #f))
+ ;; Simple case: no keyword arguments.
;; todo: handle the more complex cases
(let* ((nargs (length orig-args))
(nreq (length req))
(nopt (if opt (length opt) 0))
(key (source-expression proc)))
+ (define (inlined-call)
+ (make-let src
+ (append req
+ (or opt '())
+ (if rest (list rest) '()))
+ gensyms
+ (if (> nargs (+ nreq nopt))
+ (append (list-head orig-args (+ nreq nopt))
+ (list
+ (make-primcall
+ #f 'list
+ (drop orig-args (+ nreq nopt)))))
+ (append orig-args
+ (drop inits (- nargs nreq))
+ (if rest
+ (list (make-const #f '()))
+ '())))
+ body))
+
(cond
- ((or (< nargs nreq) (> nargs (+ nreq nopt)))
+ ((or (< nargs nreq) (and (not rest) (> nargs (+ nreq nopt))))
;; An error, or effecting arguments.
- (make-application src (for-value orig-proc)
- (map for-value orig-args)))
+ (make-call src (for-call orig-proc) (map for-value orig-args)))
((or (and=> (find-counter key counter) counter-recursive?)
(lambda? orig-proc))
;; A recursive call, or a lambda in the operator
;; position of the source expression. Process again in
;; tail context.
+ ;;
+ ;; In the recursive case, mark intervening counters as
+ ;; recursive, so we can handle a toplevel counter that
+ ;; recurses mutually with some other procedure.
+ ;; Otherwise, the next time we see the other procedure,
+ ;; the effort limit would be clamped to 100.
+ ;;
+ (let ((found (find-counter key counter)))
+ (if (and found (counter-recursive? found))
+ (let lp ((counter counter))
+ (if (not (eq? counter found))
+ (begin
+ (set-counter-recursive?! counter #t)
+ (lp (counter-prev counter)))))))
+
(log 'inline-recurse key)
- (loop (make-let src (append req (or opt '()))
- gensyms
- (append orig-args
- (drop inits (- nargs nreq)))
- body)
- env counter ctx))
+ (loop (inlined-call) env counter ctx))
(else
;; An integration at the top-level, the first
;; recursion of a recursive procedure, or a nested
(let/ec k
(define (abort)
(log 'inline-abort exp)
- (k (make-application src
- (for-value orig-proc)
- (map for-value orig-args))))
+ (k (make-call src (for-call orig-proc)
+ (map for-value orig-args))))
(define new-counter
(cond
;; These first two cases will transfer effort
(make-top-counter effort-limit operand-size-limit
abort key))))
(define result
- (loop (make-let src (append req (or opt '()))
- gensyms
- (append orig-args
- (drop inits (- nargs nreq)))
- body)
- env new-counter ctx))
+ (loop (inlined-call) env new-counter ctx))
(if counter
;; The nested inlining attempt succeeded.
(log 'inline-end result exp)
result)))))
+ (($ <let> _ _ _ vals _)
+ ;; Attempt to inline `let' in the operator position.
+ ;;
+ ;; We have to re-visit the proc in value mode, since the
+ ;; `let' bindings might have been introduced or renamed,
+ ;; whereas the lambda (if any) in operator position has not
+ ;; been renamed.
+ (if (or (and-map constant-expression? vals)
+ (and-map constant-expression? orig-args))
+ ;; The arguments and the let-bound values commute.
+ (match (for-value orig-proc)
+ (($ <let> lsrc names syms vals body)
+ (log 'inline-let orig-proc)
+ (for-tail
+ (make-let lsrc names syms vals
+ (make-call src body orig-args))))
+ ;; It's possible for a `let' to go away after the
+ ;; visit due to the fact that visiting a procedure in
+ ;; value context will prune unused bindings, whereas
+ ;; visiting in operator mode can't because it doesn't
+ ;; traverse through lambdas. In that case re-visit
+ ;; the procedure.
+ (proc (revisit-proc proc)))
+ (make-call src (for-call orig-proc)
+ (map for-value orig-args))))
(_
- (make-application src proc
- (map for-value orig-args))))))
+ (make-call src (for-call orig-proc) (map for-value orig-args))))))
(($ <lambda> src meta body)
(case ctx
((effect) (make-void #f))
((test) (make-const #f #t))
((operator) exp)
- (else
- (make-lambda src meta (for-value body)))))
+ (else (record-source-expression!
+ exp
+ (make-lambda src meta (and body (for-values body)))))))
(($ <lambda-case> src req opt rest kw inits gensyms body alt)
- (make-lambda-case src req opt rest kw
- (map for-value inits)
- gensyms
- (for-tail body)
- (and alt (for-tail alt))))
- (($ <sequence> src exps)
- (let lp ((exps exps) (effects '()))
- (match exps
- ((last)
- (if (null? effects)
- (for-tail last)
- (make-sequence
- src
- (reverse (cons (for-tail last) effects)))))
- ((head . rest)
- (let ((head (for-effect head)))
- (cond
- ((sequence? head)
- (lp (append (sequence-exps head) rest) effects))
- ((void? head)
- (lp rest effects))
- (else
- (lp rest (cons head effects)))))))))
+ (define (lift-applied-lambda body gensyms)
+ (and (not opt) rest (not kw)
+ (match body
+ (($ <primcall> _ '@apply
+ (($ <lambda> _ _ (and lcase ($ <lambda-case>)))
+ ($ <lexical-ref> _ _ sym)
+ ...))
+ (and (equal? sym gensyms)
+ (not (lambda-case-alternate lcase))
+ lcase))
+ (_ #f))))
+ (let* ((vars (map lookup-var gensyms))
+ (new (fresh-gensyms vars))
+ (env (fold extend-env env gensyms
+ (make-unbound-operands vars new)))
+ (new-sym (lambda (old)
+ (operand-sym (cdr (vhash-assq old env)))))
+ (body (loop body env counter ctx)))
+ (or
+ ;; (lambda args (apply (lambda ...) args)) => (lambda ...)
+ (lift-applied-lambda body new)
+ (make-lambda-case src req opt rest
+ (match kw
+ ((aok? (kw name old) ...)
+ (cons aok? (map list kw name (map new-sym old))))
+ (_ #f))
+ (map (cut loop <> env counter 'value) inits)
+ new
+ body
+ (and alt (for-tail alt))))))
+ (($ <seq> src head tail)
+ (let ((head (for-effect head))
+ (tail (for-tail tail)))
+ (if (void? head)
+ tail
+ (make-seq src
+ (if (and (seq? head)
+ (void? (seq-tail head)))
+ (seq-head head)
+ head)
+ tail))))
(($ <prompt> src tag body handler)
- (define (singly-used-definition x)
+ (define (make-prompt-tag? x)
+ (match x
+ (($ <primcall> _ 'make-prompt-tag (or () ((? constant-expression?))))
+ #t)
+ (_ #f)))
+
+ (let ((tag (for-value tag))
+ (body (for-tail body)))
(cond
- ((and (lexical-ref? x)
- ;; Only fetch definitions with single uses.
- (= (lexical-refcount (lexical-ref-gensym x)) 1)
- (lookup (lexical-ref-gensym x)))
- => singly-used-definition)
- (else x)))
- (match (singly-used-definition tag)
- (($ <application> _ ($ <primitive-ref> _ 'make-prompt-tag)
- (or () ((? constant-expression?))))
- ;; There is no way that an <abort> could know the tag
- ;; for this <prompt>, so we can elide the <prompt>
- ;; entirely.
- (for-tail body))
- (_
- (make-prompt src (for-value tag) (for-tail body)
- (for-value handler)))))
+ ((find-definition tag 1)
+ (lambda (val op)
+ (make-prompt-tag? val))
+ => (lambda (val op)
+ ;; There is no way that an <abort> could know the tag
+ ;; for this <prompt>, so we can elide the <prompt>
+ ;; entirely.
+ (unrecord-operand-uses op 1)
+ body))
+ ((find-definition tag 2)
+ (lambda (val op)
+ (and (make-prompt-tag? val)
+ (abort? body)
+ (tree-il=? (abort-tag body) tag)))
+ => (lambda (val op)
+ ;; (let ((t (make-prompt-tag)))
+ ;; (call-with-prompt t
+ ;; (lambda () (abort-to-prompt t val ...))
+ ;; (lambda (k arg ...) e ...)))
+ ;; => (let-values (((k arg ...) (values values val ...)))
+ ;; e ...)
+ (unrecord-operand-uses op 2)
+ (for-tail
+ (make-let-values
+ src
+ (make-primcall #f 'apply
+ `(,(make-primitive-ref #f 'values)
+ ,(make-primitive-ref #f 'values)
+ ,@(abort-args body)
+ ,(abort-tail body)))
+ (for-value handler)))))
+ (else
+ (make-prompt src tag body (for-value handler))))))
(($ <abort> src tag args tail)
(make-abort src (for-value tag) (map for-value args)
(for-value tail))))))
HCoop / bpt / guile.git / blobdiff