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adjust required-keyword expansion to improve optimization

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Make the definition of a function with a required keyword expand in a
way that allows the optimizer to recognize it as a form that has no
errors or externally visible side effects.

The old expansion of

 (define (f #:x x) ...)

included

 (define lifted-constructor (make-required ....))
 (define f (lifted-constructor (lambda ....) ....))

where `make-required` calls `make-struct-type` and returns just the
constructor.

The new expansion instead has

 (define-values (_ lifted-constructor _ _ _)
   (make-struct-type ....))
 (define f (lifted-constructor (lambda ....) ....))

In other words, `make-required` is inlined by macro expansion,
so that the optimizer will be able to see it and eventually
conclude that no side effects have taken place.
This commit is contained in:
Matthew Flatt 2016-08-07 05:46:13 -06:00
parent 62b8f7aaa3
commit 7bcc9afd4c
1 changed files with 82 additions and 35 deletions
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117
racket/collects/racket/private/kw.rkt
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@ -142,31 +142,6 @@
(define-values (prop:named-keyword-procedure named-keyword-procedure? keyword-procedure-name+fail) (define-values (prop:named-keyword-procedure named-keyword-procedure? keyword-procedure-name+fail)
(make-struct-type-property 'named-keyword-procedure)) (make-struct-type-property 'named-keyword-procedure))
;; Constructor generator for a procedure with a required keyword.
;; (This is used with lift-expression, so that the same constructor
;; is used for each evaluation of a keyword lambda.)
;; The `procedure' property is a per-type method that has exactly
;; the right arity, and that sends all arguments to `missing-kw'.
(define (make-required name fail-proc method? impersonator?)
(let-values ([(s: mk ? -ref -set!)
(make-struct-type (or name 'unknown)
(if impersonator?
(if method?
struct:keyword-method-impersonator
struct:keyword-procedure-impersonator)
(if method?
struct:keyword-method
struct:keyword-procedure))
0 0 #f
(list (cons prop:arity-string
generate-arity-string)
(cons prop:named-keyword-procedure
(cons name fail-proc))
(cons prop:incomplete-arity
#t))
(current-inspector) fail-proc)])
mk))
;; Allows support for new-prop:procedure to extract a field (i.e., this property ;; Allows support for new-prop:procedure to extract a field (i.e., this property
;; makes it possible to extract a field for an integer `new-prop:procedure` value): ;; makes it possible to extract a field for an integer `new-prop:procedure` value):
(define-values (prop:procedure-accessor procedure-accessor? procedure-accessor-ref) (define-values (prop:procedure-accessor procedure-accessor? procedure-accessor-ref)
@ -187,8 +162,9 @@
;; value is an integer: ;; value is an integer:
(cons prop:procedure-accessor values)))) (cons prop:procedure-accessor values))))
;; ----------------------------------------
;; Proxies ;; Proxies
(define-values (struct:keyword-procedure-impersonator make-kpp keyword-procedure-impersonator? kpp-ref kpp-set!) (define-values (struct:keyword-procedure-impersonator make-kpp keyword-procedure-impersonator? kpp-ref kpp-set!)
(make-struct-type 'procedure (make-struct-type 'procedure
struct:keyword-procedure struct:keyword-procedure
@ -210,6 +186,74 @@
1 0 #f 1 0 #f
(list (cons prop:keyword-impersonator (lambda (v) (okmp-ref v 0)))))) (list (cons prop:keyword-impersonator (lambda (v) (okmp-ref v 0))))))
;; ----------------------------------------
;; Functions and proxies with required keyword arguments
(define-values (struct:keyword-procedure/arity-error make-kp/ae kp/ae? kp/ae-ref kp/ae-set!)
(make-struct-type 'procedure
struct:keyword-procedure
0 0 #f
(list (cons prop:arity-string generate-arity-string)
(cons prop:incomplete-arity #t))))
(define-values (struct:keyword-method/arity-error make-km/ae km/ae? km/ae-ref km/ae-set!)
(make-struct-type 'procedure
struct:keyword-method
0 0 #f
(list (cons prop:arity-string generate-arity-string)
(cons prop:incomplete-arity #t))))
(define-values (struct:keyword-procedure-impersonator/arity-error make-kpi/ae kpi/ae? kpi/ae-ref kpi/ae-set!)
(make-struct-type 'procedure
struct:keyword-procedure-impersonator
0 0 #f
(list (cons prop:arity-string generate-arity-string)
(cons prop:incomplete-arity #t))))
(define-values (struct:keyword-method-impersonator/arity-error make-kmi/ae kmi/ae? kmi/ae-ref kmi/ae-set!)
(make-struct-type 'procedure
struct:keyword-method-impersonator
0 0 #f
(list (cons prop:arity-string generate-arity-string)
(cons prop:incomplete-arity #t))))
;; Constructor generator for a wrapper on a procedure with a required keyword.
;; The `procedure' property is a per-type method that has exactly
;; the right arity, and that sends all arguments to `missing-kw'.
(define (make-required name fail-proc method? impersonator?)
(let-values ([(s: mk ? -ref -set!)
(make-struct-type (or name 'unknown)
(if impersonator?
(if method?
struct:keyword-method-impersonator/arity-error
struct:keyword-procedure-impersonator/arity-error)
(if method?
struct:keyword-method/arity-error
struct:keyword-procedure/arity-error))
0 0 #f
(list (cons prop:named-keyword-procedure
(cons name fail-proc)))
(current-inspector)
fail-proc)])
mk))
;; Macro variant of `make-required`, used for lambda form with a required
;; keyword. We use a macro so that the `make-struct-type` is visible
;; to the optimizer, which in turn allows it to determine that the first
;; result is a constructor that always succeeds.
;; >> Beware that `name` and `fail-proc` are duplicated in the macro expansion. <<
;; The `name` expresison is expected to be a quoted symbol, and `fail-proc` is
;; expected to be a small procedure, so that duplication is ok.
;; (This macro is used with lift-values-expression, so that the same constructor
;; is used for each evaluation of a keyword lambda.)
(define-syntax (make-required* stx)
(syntax-case stx ()
[(_ struct:km/ae name fail-proc)
#'(make-struct-type name
struct:km/ae
0 0 #f
(list (cons prop:named-keyword-procedure
(cons name fail-proc)))
(current-inspector)
fail-proc)]))
;; ---------------------------------------- ;; ----------------------------------------
(define make-keyword-procedure (define make-keyword-procedure
@ -467,7 +511,9 @@
[make-okp (if method? [make-okp (if method?
#'make-optional-keyword-method #'make-optional-keyword-method
#'make-optional-keyword-procedure)] #'make-optional-keyword-procedure)]
[method? method?] [struct:kp/ae (if method?
#'struct:keyword-method/arity-error
#'struct:keyword-procedure/arity-error)]
[with-kw-min-args (+ 2 (length plain-ids))] [with-kw-min-args (+ 2 (length plain-ids))]
[with-kw-max-arg (if (null? (syntax-e #'rest)) [with-kw-max-arg (if (null? (syntax-e #'rest))
(+ 2 (length plain-ids) (length opts)) (+ 2 (length plain-ids) (length opts))
@ -609,11 +655,12 @@
[needed-kws needed-kws] [needed-kws needed-kws]
[no-kws (mk-no-kws #t)] [no-kws (mk-no-kws #t)]
[with-kws (mk-with-kws)] [with-kws (mk-with-kws)]
[mk-id (with-syntax ([n (or local-name [(_ mk-id . _) (with-syntax ([n (or local-name
(syntax-local-infer-name stx))] (syntax-local-infer-name stx))]
[call-fail (mk-kw-arity-stub)]) [call-fail (mk-kw-arity-stub)])
(syntax-local-lift-expression (syntax-local-lift-values-expression
#'(make-required 'n call-fail method? #f)))]) 5
#'(make-required* struct:kp/ae 'n call-fail)))])
(quasisyntax/loc stx (quasisyntax/loc stx
(mk-id (mk-id
(lambda (given-kws given-argc) (lambda (given-kws given-argc)
@ -1323,9 +1370,9 @@
(format "\n ~a ~e" kw kw-arg)) (format "\n ~a ~e" kw kw-arg))
kws kw-args))))] kws kw-args))))]
[proc-name (lambda (p) (or (and (named-keyword-procedure? p) [proc-name (lambda (p) (or (and (named-keyword-procedure? p)
(car (keyword-procedure-name+fail p))) (car (keyword-procedure-name+fail p)))
(object-name p) (object-name p)
p))]) p))])
(raise (raise
(exn:fail:contract (exn:fail:contract
(if extra-kw (if extra-kw