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Finding a procedure's arity uses binary search

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* module/system/vm/assembler.scm (pack-arity-flags):
  (write-arity-headers): Add a flag to indicate that an arity is part of
  a case-lambda, so that we can use binary search to find arities.

* module/system/vm/debug.scm (is-in-case-lambda?)
  (arity-is-in-case-lambda?, find-first-arity): Use binary search.
This commit is contained in:
Andy Wingo 2013-11-09 16:02:13 +01:00
parent 695e6b7551
commit d8595af555
2 changed files with 36 additions and 25 deletions
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26
module/system/vm/assembler.scm
View file

@ -1322,6 +1322,7 @@ it will be added to the GC roots at runtime."
;;; #x2: allow-other-keys?
;;; #x4: has-keyword-args?
;;; #x8: is-case-lambda?
;;; #x10: is-in-case-lambda?
;;;
;;; Functions with a single arity specify their number of required and
;;; optional arguments in nreq and nopt, and do not have the
@ -1341,10 +1342,10 @@ it will be added to the GC roots at runtime."
;;; Functions with multiple arities are preceded by a header with
;;; is-case-lambda? set. All other fields are 0, except low-pc and
;;; high-pc which should be the bounds of the whole function. Headers
;;; for the individual arities follow. In this way the whole headers
;;; array is sorted in increasing low-pc order, and case-lambda clauses
;;; are contained within the [low-pc, high-pc] of the case-lambda
;;; header.
;;; for the individual arities follow, with the is-in-case-lambda? flag
;;; set. In this way the whole headers array is sorted in increasing
;;; low-pc order, and case-lambda clauses are contained within the
;;; [low-pc, high-pc] of the case-lambda header.
;; Length of the prefix to the arities section, in bytes.
(define arities-prefix-len 4)
@ -1356,11 +1357,13 @@ it will be added to the GC roots at runtime."
(define arity-header-offset-offset (* 2 4))
(define-syntax-rule (pack-arity-flags has-rest? allow-other-keys?
has-keyword-args? is-case-lambda?)
has-keyword-args? is-case-lambda?
is-in-case-lambda?)
(logior (if has-rest? (ash 1 0) 0)
(if allow-other-keys? (ash 1 1) 0)
(if has-keyword-args? (ash 1 2) 0)
(if is-case-lambda? (ash 1 3) 0)))
(if is-case-lambda? (ash 1 3) 0)
(if is-in-case-lambda? (ash 1 4) 0)))
(define (meta-arities-size meta)
(define (lambda-size arity)
@ -1387,13 +1390,14 @@ it will be added to the GC roots at runtime."
(bytevector-u32-set! bv (+ pos 12) flags endianness)
(bytevector-u32-set! bv (+ pos 16) nreq endianness)
(bytevector-u32-set! bv (+ pos 20) nopt endianness))
(define (write-arity-header pos arity)
(define (write-arity-header pos arity in-case-lambda?)
(write-arity-header* pos (arity-low-pc arity)
(arity-high-pc arity)
(pack-arity-flags (arity-rest arity)
(arity-allow-other-keys? arity)
(pair? (arity-kw-indices arity))
#f)
#f
in-case-lambda?)
(length (arity-req arity))
(length (arity-opt arity))))
(let lp ((metas metas) (pos arities-prefix-len) (offsets '()))
@ -1406,7 +1410,7 @@ it will be added to the GC roots at runtime."
(match (meta-arities meta)
(() (lp metas pos offsets))
((arity)
(write-arity-header pos arity)
(write-arity-header pos arity #f)
(lp metas
(+ pos arity-header-len)
(acons arity (+ pos arity-header-offset-offset) offsets)))
@ -1414,13 +1418,13 @@ it will be added to the GC roots at runtime."
;; Write a case-lambda header, then individual arities.
;; The case-lambda header's offset link is 0.
(write-arity-header* pos (meta-low-pc meta) (meta-high-pc meta)
(pack-arity-flags #f #f #f #t) 0 0)
(pack-arity-flags #f #f #f #t #f) 0 0)
(let lp* ((arities arities) (pos (+ pos arity-header-len))
(offsets offsets))
(match arities
(() (lp metas pos offsets))
((arity . arities)
(write-arity-header pos arity)
(write-arity-header pos arity #t)
(lp* arities
(+ pos arity-header-len)
(acons arity

35
module/system/vm/debug.scm
View file

@ -272,11 +272,13 @@ section of the ELF image. Returns an ELF symbol, or @code{#f}."
;;; #x2: allow-other-keys?
;;; #x4: has-keyword-args?
;;; #x8: is-case-lambda?
;;; #x10: is-in-case-lambda?
(define (has-rest? flags) (not (zero? (logand flags (ash 1 0)))))
(define (allow-other-keys? flags) (not (zero? (logand flags (ash 1 1)))))
(define (has-keyword-args? flags) (not (zero? (logand flags (ash 1 2)))))
(define (is-case-lambda? flags) (not (zero? (logand flags (ash 1 3)))))
(define (is-in-case-lambda? flags) (not (zero? (logand flags (ash 1 4)))))
(define (arity-low-pc arity)
(let ((ctx (arity-context arity)))
@ -308,6 +310,7 @@ section of the ELF image. Returns an ELF symbol, or @code{#f}."
(define (arity-allow-other-keys? arity) (allow-other-keys? (arity-flags arity)))
(define (arity-has-keyword-args? arity) (has-keyword-args? (arity-flags arity)))
(define (arity-is-case-lambda? arity) (is-case-lambda? (arity-flags arity)))
(define (arity-is-in-case-lambda? arity) (is-in-case-lambda? (arity-flags arity)))
(define (arity-load-symbol arity)
(let ((elf (debug-context-elf (arity-context arity))))
@ -358,19 +361,24 @@ section of the ELF image. Returns an ELF symbol, or @code{#f}."
(let* ((bv (elf-bytes (debug-context-elf context)))
(text-offset (- addr
(debug-context-text-base context)
(debug-context-base context)))
(headers-start (+ base arities-prefix-len))
(headers-end (+ base (bytevector-u32-native-ref bv base))))
;; FIXME: This is linear search. Change to binary search.
(let lp ((pos headers-start))
(cond
((>= pos headers-end) #f)
((< text-offset (arity-low-pc* bv pos))
#f)
((<= (arity-high-pc* bv pos) text-offset)
(lp (+ pos arity-header-len)))
(else
(make-arity context base pos))))))
(debug-context-base context))))
(binary-search
(+ base arities-prefix-len)
(+ base (bytevector-u32-native-ref bv base))
arity-header-len
(lambda (pos continue-before continue-after)
(let lp ((pos pos))
(cond
((is-in-case-lambda? (arity-flags* bv pos))
(lp (- pos arity-header-len)))
((< text-offset (arity-low-pc* bv pos))
(continue-before))
((<= (arity-high-pc* bv pos) text-offset)
(continue-after))
(else
(make-arity context base pos)))))
(lambda ()
#f))))
(define (read-sub-arities context base outer-header-offset)
(let* ((bv (elf-bytes (debug-context-elf context)))
@ -391,7 +399,6 @@ section of the ELF image. Returns an ELF symbol, or @code{#f}."
(lambda (sec)
(let* ((base (elf-section-offset sec))
(first (find-first-arity context base addr)))
;; FIXME: Handle case-lambda arities.
(cond
((not first) '())
((arity-is-case-lambda? first)