Coalesce constant strings more aggressively maybe.

[sbcl.git] / src / pcl / low.lisp

;;;; This file contains portable versions of low-level functions and macros
;;;; which are ripe for implementation specific customization. None of the code
;;;; in this file *has* to be customized for a particular Common Lisp
;;;; implementation. Moreover, in some implementations it may not make any
;;;; sense to customize some of this code.
;;;;
;;;; The original version was intended to support portable customization to
;;;; lotso different Lisp implementations. This functionality is gone in the
;;;; current version, and it now runs only under SBCL. (Now that ANSI Common
;;;; Lisp has mixed CLOS into the insides of the system (e.g. error handling
;;;; and printing) so deeply that it's not very meaningful to bootstrap Common
;;;; Lisp without CLOS, the old functionality is of dubious use. -- WHN
;;;; 19981108)

;;;; This software is part of the SBCL system. See the README file for more
;;;; information.

;;;; This software is derived from software originally released by Xerox
;;;; Corporation. Copyright and release statements follow. Later modifications
;;;; to the software are in the public domain and are provided with
;;;; absolutely no warranty. See the COPYING and CREDITS files for more
;;;; information.

;;;; copyright information from original PCL sources:
;;;;
;;;; Copyright (c) 1985, 1986, 1987, 1988, 1989, 1990 Xerox Corporation.
;;;; All rights reserved.
;;;;
;;;; Use and copying of this software and preparation of derivative works based
;;;; upon this software are permitted. Any distribution of this software or
;;;; derivative works must comply with all applicable United States export
;;;; control laws.
;;;;
;;;; This software is made available AS IS, and Xerox Corporation makes no
;;;; warranty about the software, its performance or its conformity to any
;;;; specification.

(in-package "SB!PCL")
\f
(eval-when (:compile-toplevel :load-toplevel :execute)
(defvar *optimize-speed*
  '(optimize (speed 3) (safety 0) (sb!ext:inhibit-warnings 3) (debug 0)))
) ; EVAL-WHEN

(defmacro dotimes-fixnum ((var count &optional (result nil)) &body body)
  `(dotimes (,var (the fixnum ,count) ,result)
     (declare (fixnum ,var))
     ,@body))

(declaim (inline random-fixnum))
(defun random-fixnum ()
  (random (1+ most-positive-fixnum)))

;;; Lambda which executes its body (or not) randomly. Used to drop
;;; random cache entries.
;;; This formerly punted with slightly greater than 50% probability,
;;; and there was a periodicity to the nonrandomess.
;;; If that was intentional, it should have been commented to that effect.
(defmacro randomly-punting-lambda (lambda-list &body body)
  (with-unique-names (drops drop-pos)
    `(let ((,drops (random-fixnum)) ; means a POSITIVE fixnum
           (,drop-pos sb!vm:n-positive-fixnum-bits))
       (declare (fixnum ,drops)
                (type (mod #.sb!vm:n-fixnum-bits) ,drop-pos))
       (lambda ,lambda-list
         (when (logbitp (the unsigned-byte (decf ,drop-pos)) ,drops)
           (locally ,@body))
         (when (zerop ,drop-pos)
           (setf ,drops (random-fixnum)
                 ,drop-pos sb!vm:n-positive-fixnum-bits))))))
\f
(import 'sb!kernel:funcallable-instance-p) ; why?

(defun set-funcallable-instance-function (fin new-value)
  (declare (type function new-value)
           ;; KLUDGE: it might be nice to restrict
           ;; SB-MOP:SET-FUNCALLABLE-INSTANCE-FUNCTION to operate only
           ;; on generalized instances of
           ;; SB-MOP:FUNCALLABLE-STANDARD-OBJECT; at present, even
           ;; PCL's internal use of SET-FUNCALLABLE-INSTANCE-FUNCTION
           ;; doesn't obey this restriction.
           (type funcallable-instance fin))
  (setf (funcallable-instance-fun fin) new-value))

;;; FIXME: these macros should just go away.  It's not clear whether
;;; the inline functions defined by
;;; !DEFSTRUCT-WITH-ALTERNATE-METACLASS are as efficient as they could
;;; be; ordinary defstruct accessors are defined as source transforms.
(declaim (inline fsc-instance-p))
(defun fsc-instance-p (fin)
  (funcallable-instance-p fin))
(defmacro fsc-instance-slots (fin)
  `(%funcallable-instance-info ,fin sb!vm:instance-data-start))
\f
(declaim (inline clos-slots-ref (setf clos-slots-ref)))
(declaim (ftype (function (simple-vector index) t) clos-slots-ref))
(defun clos-slots-ref (slots index)
  (svref slots index))
(declaim (ftype (function (t simple-vector index) t) (setf clos-slots-ref)))
(defun (setf clos-slots-ref) (new-value slots index)
  (setf (svref slots index) new-value))

;;; Note on implementation under CMU CL >=17 and SBCL: STD-INSTANCE-P
;;; is only used to discriminate between functions (including FINs)
;;; and normal instances, so we can return true on structures also. A
;;; few uses of (OR STD-INSTANCE-P FSC-INSTANCE-P) are changed to
;;; PCL-INSTANCE-P.
(declaim (inline std-instance-p))
(defun std-instance-p (x)
  (%instancep x))
\f
;;; When given a funcallable instance, SET-FUN-NAME *must* side-effect
;;; that FIN to give it the name. When given any other kind of
;;; function SET-FUN-NAME is allowed to return a new function which is
;;; "the same" except that it has the name.
;;;
;;; In all cases, SET-FUN-NAME must return the new (or same)
;;; function. (Unlike other functions to set stuff, it does not return
;;; the new value.)
;; This is an absolutely terrible name for a function which both assigns
;; the name slot of a function, and _sometimes_ binds a name to a function.
(defun set-fun-name (fun new-name)
  "Set the name of a compiled function object. Return the function."
  (when (valid-function-name-p fun)
    (setq fun (fdefinition fun)))
  (typecase fun
    (%method-function fun)
    ;; a closure potentially becomes a different closure
    (closure (setq fun (sb!impl::set-closure-name fun new-name)))
    (t (setf (%fun-name fun) new-name)))
  ;; Fixup name-to-function mappings in cases where the function
  ;; hasn't been defined by DEFUN.  (FIXME: is this right?  This logic
  ;; comes from CMUCL).  -- CSR, 2004-12-31
  ;;
  ;; Now, given this logic is somewhat suspect to begin with, and is the final
  ;; remaining contributor to the immortalization of EQL-specialized methods,
  ;; I'm going to say that we don't create an fdefn for anything
  ;; whose specializers are not symbols.
  ;; Otherwise, adding+removing N methods named
  ;;  (SLOW-METHOD BLAH ((EQL <HAIRY-LIST-OBJECT>)))
  ;; makes them all permanent because FDEFNs are compared by name EQUALity,
  ;; so each gets its own FDEFN. This is bad, and pretty much useless anyway.
  (when (and (consp new-name)
             (or (eq (car new-name) 'slot-accessor)
                 (and (member (car new-name) '(slow-method fast-method))
                      ;; name is: ({SLOW|FAST}-METHOD root <qual>* spec+)
                      (every #'symbolp (car (last new-name))))))
    (setf (fdefinition new-name) fun))
  fun)
\f
;;; FIXME: probably no longer needed after init
(defmacro precompile-random-code-segments (&optional system)
  `(progn
     (eval-when (:compile-toplevel)
       (update-dispatch-dfuns))
     (precompile-function-generators ,system)
     (precompile-dfun-constructors ,system)
     (precompile-ctors)))
\f
;;; Return true of any object which is either a funcallable-instance,
;;; or an ordinary instance that is not a structure-object.
;;; This used to be implemented as (LAYOUT-FOR-STD-CLASS-P (LAYOUT-OF x))
;;; but LAYOUT-OF is more general than need be here. So this bails out
;;; after the first two clauses of the equivalent COND in LAYOUT-OF
;;; because nothing else could possibly return T.
(declaim (inline %pcl-instance-p))
(defun %pcl-instance-p (x)
  (layout-for-std-class-p
   (cond ((%instancep x) (%instance-layout x))
         ((funcallable-instance-p x) (%funcallable-instance-layout x))
         (t (return-from %pcl-instance-p nil)))))

;;; This definition is for interpreted code.
(defun pcl-instance-p (x) (declare (explicit-check)) (%pcl-instance-p x))

;;; Both of these operations "work" on structures, which allows the above
;;; weakening of STD-INSTANCE-P.
;;; FIXME: what does the preceding comment mean? You can't use instance-slots
;;; on a structure. (Consider especially a structure of 0 slots.)
(defmacro std-instance-slots (x) `(%instance-ref ,x sb!vm:instance-data-start))

;;; FIXME: These functions are called every place we do a
;;; CALL-NEXT-METHOD, and probably other places too. It's likely worth
;;; selectively optimizing them with DEFTRANSFORMs and stuff, rather
;;; than just indiscriminately expanding them inline everywhere.
(declaim (inline get-slots get-slots-or-nil))
(declaim (ftype (function (t) simple-vector) get-slots))
(declaim (ftype (function (t) (or simple-vector null)) get-slots-or-nil))
(defun get-slots (instance)
  (if (std-instance-p instance)
      (std-instance-slots instance)
      (fsc-instance-slots instance)))
(defun get-slots-or-nil (instance)
  ;; Suppress a code-deletion note.  FIXME: doing the FIXME above,
  ;; integrating PCL more with the compiler, would remove the need for
  ;; this icky stuff.
  (declare (optimize (inhibit-warnings 3)))
  (when (pcl-instance-p instance)
    (get-slots instance)))

;; This macro is used only by %CHANGE-CLASS. Can we just do this there?
;; [The code in 'fsc.lisp' which looks like it needs it is commented out]
(defmacro get-wrapper (inst)
  (once-only ((wrapper `(layout-of ,inst)))
    `(progn
       (aver (layout-for-std-class-p ,wrapper))
       ,wrapper)))
\f
;;;; structure-instance stuff
;;;;
;;;; FIXME: Now that the code is SBCL-only, this extra layer of
;;;; abstraction around our native structure representation doesn't
;;;; seem to add anything useful, and could probably go away.

;;; The definition of STRUCTURE-TYPE-P was moved to early-low.lisp.

(defun structure-type-slot-description-list (type)
  (let* ((dd (find-defstruct-description type))
         (include (dd-include dd))
         (all-slots (dd-slots dd)))
    (multiple-value-bind (super slot-overrides)
        (if (consp include)
            (values (car include) (mapcar #'car (cdr include)))
            (values include nil))
      (let ((included-slots
             (when super
               (dd-slots (find-defstruct-description super)))))
        (loop for slot = (pop all-slots)
              for included-slot = (pop included-slots)
              while slot
              when (or (not included-slot)
                       (member (dsd-name included-slot) slot-overrides :test #'eq))
              collect slot)))))

(defun uninitialized-accessor-function (type slotd)
  (lambda (&rest args)
    (declare (ignore args))
    (error "~:(~A~) function~@[ for ~S ~] not yet initialized."
           type slotd)))

(defun structure-slotd-name (slotd)
  (dsd-name slotd))

(defun structure-slotd-accessor-symbol (slotd)
  (dsd-accessor-name slotd))

(defun structure-slotd-reader-function (slotd)
  (let ((name (dsd-accessor-name slotd)))
    (if (fboundp name)
        (fdefinition name)
        (uninitialized-accessor-function :reader slotd))))

;;; Return a function to write the slot identified by SLOTD.
;;; This is easy for read/write slots - we just return the accessor
;;; that was already set up - but it requires work for read-only slots.
;;; Basically we get the slotter-setter-lambda-form and compile it.
;;; Using (COERCE lambda-form 'FUNCTION) as used to be done might produce
;;; an interpreted function. I'm not sure whether that's right or wrong,
;;; because if the DEFSTRUCT itself were evaluated, then the ordinary
;;; accessors would indeed be interpreted. However if the DEFSTRUCT were
;;; compiled, and the fasl loaded in a Lisp with *EVALUATOR-MODE* = :INTERPRET,
;;; arguably this is against the expectation that all things got compiled.
;;; But can people really expect that manipulating read-only slots
;;; via (SETF SLOT-VALUE) should be fast?
;;;
;;; Damned-if-you-do / damned-if-you don't - the best thing would be to
;;; compile all accessors at "really" compile-time but not store the writer
;;; for a reaadonly slot under the #<fdefn> for #'(SETF slot-name).
;;;
(defun structure-slotd-writer-function (type slotd)
  ;; TYPE is not used, because the DD is taken from runtime data.
  (declare (ignore type))
  (if (dsd-read-only slotd)
      ;; We'd like to compile the writer just-in-time and store it
      ;; back into the STRUCTURE-DIRECT-SLOT-DEFINITION and also
      ;; the LAYOUT for the class, but we don't have a handle on
      ;; any of the containing objects. So this has to be a closure.
      (let ((setter 0))
        (lambda (newval instance)
          (if (eql setter 0)
              (let* ((dd (layout-info (%instance-layout instance)))
                     (f (compile nil (slot-setter-lambda-form dd slotd))))
                (if (functionp f)
                    (funcall (setq setter f) newval instance)
                    (uninitialized-accessor-function :writer slotd)))
              (funcall (truly-the function setter) newval instance))))
      (let ((name `(setf ,(dsd-accessor-name slotd))))
        (if (fboundp name)
            (fdefinition name)
            (uninitialized-accessor-function :writer slotd)))))

(defun structure-slotd-type (slotd)
  (dsd-type slotd))

(defun structure-slotd-init-form (slotd)
  (dsd-default slotd))