src/compiler/policy.lisp

   1 ;;;; compiler optimization policy stuff
   2
   3 ;;;; This software is part of the SBCL system. See the README file for
   4 ;;;; more information.
   5 ;;;;
   6 ;;;; This software is derived from the CMU CL system, which was
   7 ;;;; written at Carnegie Mellon University and released into the
   8 ;;;; public domain. The software is in the public domain and is
   9 ;;;; provided with absolutely no warranty. See the COPYING and CREDITS
  10 ;;;; files for more information.
  11
  12 (in-package "SB!C")
  13
  14 ;;; a value for an optimization declaration
  15 (def!type policy-quality () '(integer 0 3))
  16
  17 ;;; CMU CL used a special STRUCTURE-OBJECT type POLICY to represent
  18 ;;; the state of optimization policy at any point in compilation. This
  19 ;;; was a natural choice, but in SBCL it became a little troublesome
  20 ;;; because of stupid technicalities involving the cold initialization
  21 ;;; of structure LAYOUTs and structure accessors, so now we just use
  22 ;;; alists instead.
  23 (def!type policy () 'list)
  24
  25 (defstruct policy-dependent-quality
  26   name
  27   expression
  28   getter
  29   values-documentation)
  30
  31 ;;; names of recognized optimization policy qualities
  32 (defvar *policy-qualities*) ; (initialized at cold init)
  33 (defvar *policy-dependent-qualities* nil) ; alist of POLICY-DEPENDENT-QUALITYs
  34
  35 ;;; Is X the name of an optimization policy quality?
  36 (defun policy-quality-name-p (x)
  37   (or (memq x *policy-qualities*)
  38       (assq x *policy-dependent-qualities*)))
  39
  40 ;;; *POLICY* holds the current global compiler policy information, as
  41 ;;; an alist mapping from optimization quality name to quality value.
  42 ;;; Inside the scope of declarations, new entries are added at the
  43 ;;; head of the alist.
  44 (declaim (type policy *policy*))
  45 (defvar *policy*)          ; initialized in cold init
  46
  47 ;;; This is to be called early in cold init to set things up, and may
  48 ;;; also be called again later in cold init in order to reset default
  49 ;;; optimization policy back to default values after toplevel PROCLAIM
  50 ;;; OPTIMIZE forms have messed with it.
  51 (defun !policy-cold-init-or-resanify ()
  52   (setf *policy-qualities*
  53         '(;; ANSI standard qualities
  54           compilation-speed
  55           debug
  56           safety
  57           space
  58           speed
  59           ;; SBCL extensions
  60           ;;
  61           ;; FIXME: INHIBIT-WARNINGS is a misleading name for this.
  62           ;; Perhaps BREVITY would be better. But the ideal name would
  63           ;; have connotations of suppressing not warnings but only
  64           ;; optimization-related notes, which is already mostly the
  65           ;; behavior, and should probably become the exact behavior.
  66           ;; Perhaps INHIBIT-NOTES?
  67           inhibit-warnings))
  68   (setf *policy*
  69         (mapcar (lambda (name)
  70                   ;; CMU CL didn't use 1 as the default for
  71                   ;; everything, but since ANSI says 1 is the ordinary
  72                   ;; value, we do.
  73                   (cons name 1))
  74                 *policy-qualities*))
  75   ;; not actually POLICY, but very similar
  76   (setf *handled-conditions* nil
  77         *disabled-package-locks* nil))
  78
  79 ;;; On the cross-compilation host, we initialize immediately (not
  80 ;;; waiting for "cold init", since cold init doesn't exist on
  81 ;;; cross-compilation host).
  82 #+sb-xc-host (!policy-cold-init-or-resanify)
  83
  84 ;;; Look up a named optimization quality in POLICY. This is only
  85 ;;; called by compiler code for known-valid QUALITY-NAMEs, e.g. SPEED;
  86 ;;; it's an error if it's called for a quality which isn't defined.
  87 (defun policy-quality (policy quality-name)
  88   (aver (policy-quality-name-p quality-name))
  89   (let* ((acons (assoc quality-name policy))
  90          (result (or (cdr acons) 1)))
  91     result))
  92
  93 ;;; syntactic sugar for querying optimization policy qualities
  94 ;;;
  95 ;;; Evaluate EXPR in terms of the optimization policy associated with
  96 ;;; THING. EXPR is a form which accesses optimization qualities by
  97 ;;; referring to them by name, e.g. (> SPEED SPACE).
  98 (defmacro policy (thing expr)
  99   (let* ((n-policy (gensym "N-POLICY-"))
 100          (binds (mapcar (lambda (name)
 101                           `(,name (policy-quality ,n-policy ',name)))
 102                         *policy-qualities*))
 103          (dependent-binds
 104           (loop for (name . info) in *policy-dependent-qualities*
 105                collect `(,name (policy-quality ,n-policy ',name))
 106                collect `(,name (if (= ,name 1)
 107                                    ,(policy-dependent-quality-expression info)
 108                                    ,name)))))
 109     `(let* ((,n-policy (%coerce-to-policy ,thing))
 110             ,@binds
 111             ,@dependent-binds)
 112        (declare (ignorable ,@*policy-qualities*
 113                            ,@(mapcar #'car *policy-dependent-qualities*)))
 114        ,expr)))
 115
 116 ;;; Dependent qualities
 117 (defmacro define-optimization-quality
 118     (name expression &optional documentation)
 119   `(eval-when (:compile-toplevel :load-toplevel :execute)
 120      (let ((acons (assoc ',name *policy-dependent-qualities*))
 121            (item (make-policy-dependent-quality
 122                   :name ',name
 123                   :expression ',expression
 124                   :getter (lambda (policy) (policy policy ,expression))
 125                   :values-documentation ',documentation)))
 126        (if acons
 127            (setf (cdr acons) item)
 128            (setf *policy-dependent-qualities*
 129                  (nconc *policy-dependent-qualities* (list `(,',name . ,item))))))
 130      ',name))