0.pre7.90:

[sbcl.git] / src / compiler / macros.lisp

;;;; miscellaneous types and macros used in writing the compiler

;;;; This software is part of the SBCL system. See the README file for
;;;; more information.
;;;;
;;;; This software is derived from the CMU CL system, which was
;;;; written at Carnegie Mellon University and released into the
;;;; public domain. The software is in the public domain and is
;;;; provided with absolutely no warranty. See the COPYING and CREDITS
;;;; files for more information.

(in-package "SB!C")

(declaim (special *wild-type* *universal-type* *compiler-error-context*))

;;; An INLINEP value describes how a function is called. The values
;;; have these meanings:
;;;     NIL     No declaration seen: do whatever you feel like, but don't 
;;;             dump an inline expansion.
;;; :NOTINLINE  NOTINLINE declaration seen: always do full function call.
;;;    :INLINE  INLINE declaration seen: save expansion, expanding to it 
;;;             if policy favors.
;;; :MAYBE-INLINE
;;;             Retain expansion, but only use it opportunistically.
(deftype inlinep () '(member :inline :maybe-inline :notinline nil))
\f
;;;; source-hacking defining forms

;;; to be passed to PARSE-DEFMACRO when we want compiler errors
;;; instead of real errors
#!-sb-fluid (declaim (inline convert-condition-into-compiler-error))
(defun convert-condition-into-compiler-error (datum &rest stuff)
  (if (stringp datum)
      (apply #'compiler-error datum stuff)
      (compiler-error "~A"
                      (if (symbolp datum)
                          (apply #'make-condition datum stuff)
                          datum))))

;;; Parse a DEFMACRO-style lambda-list, setting things up so that a
;;; compiler error happens if the syntax is invalid.
;;;
;;; Define a function that converts a special form or other magical
;;; thing into IR1. LAMBDA-LIST is a defmacro style lambda list.
;;; START-VAR and CONT-VAR are bound to the start and result
;;; continuations for the resulting IR1. KIND is the function kind to
;;; associate with NAME.
(defmacro def-ir1-translator (name (lambda-list start-var cont-var
                                                &key (kind :special-form))
                                   &body body)
  (let ((fn-name (symbolicate "IR1-CONVERT-" name))
        (n-form (gensym))
        (n-env (gensym)))
    (multiple-value-bind (body decls doc)
        (parse-defmacro lambda-list n-form body name "special form"
                        :environment n-env
                        :error-fun 'convert-condition-into-compiler-error)
      `(progn
         (declaim (ftype (function (continuation continuation t) (values))
                         ,fn-name))
         (defun ,fn-name (,start-var ,cont-var ,n-form)
           (let ((,n-env *lexenv*))
             ,@decls
             ,body
             (values)))
         ,@(when doc
             `((setf (fdocumentation ',name 'function) ,doc)))
         ;; FIXME: Evidently "there can only be one!" -- we overwrite any
         ;; other :IR1-CONVERT value. This deserves a warning, I think.
         (setf (info :function :ir1-convert ',name) #',fn-name)
         (setf (info :function :kind ',name) ,kind)
         ;; It's nice to do this for error checking in the target
         ;; SBCL, but it's not nice to do this when we're running in
         ;; the cross-compilation host Lisp, which owns the
         ;; SYMBOL-FUNCTION of its COMMON-LISP symbols.
         #-sb-xc-host
         ,@(when (eq kind :special-form)
             `((setf (symbol-function ',name)
                     (lambda (&rest rest)
                       (declare (ignore rest))
                       (error "can't FUNCALL the SYMBOL-FUNCTION of ~
                               special forms")))))))))

;;; (This is similar to DEF-IR1-TRANSLATOR, except that we pass if the
;;; syntax is invalid.)
;;;
;;; Define a macro-like source-to-source transformation for the
;;; function NAME. A source transform may "pass" by returning a
;;; non-nil second value. If the transform passes, then the form is
;;; converted as a normal function call. If the supplied arguments are
;;; not compatible with the specified LAMBDA-LIST, then the transform
;;; automatically passes.
;;;
;;; Source transforms may only be defined for functions. Source
;;; transformation is not attempted if the function is declared
;;; NOTINLINE. Source transforms should not examine their arguments.
;;; If it matters how the function is used, then DEFTRANSFORM should
;;; be used to define an IR1 transformation.
;;;
;;; If the desirability of the transformation depends on the current
;;; OPTIMIZE parameters, then the POLICY macro should be used to
;;; determine when to pass.
(defmacro define-source-transform (name lambda-list &body body)
  (let ((fn-name
         (if (listp name)
             (collect ((pieces))
               (dolist (piece name)
                 (pieces "-")
                 (pieces piece))
               (apply #'symbolicate "SOURCE-TRANSFORM" (pieces)))
             (symbolicate "SOURCE-TRANSFORM-" name)))
        (n-form (gensym))
        (n-env (gensym)))
    (multiple-value-bind (body decls)
        (parse-defmacro lambda-list n-form body name "form"
                        :environment n-env
                        :error-fun `(lambda (&rest stuff)
                                      (declare (ignore stuff))
                                      (return-from ,fn-name
                                        (values nil t))))
      `(progn
         (defun ,fn-name (,n-form)
           (let ((,n-env *lexenv*))
             ,@decls
             ,body))
         (setf (info :function :source-transform ',name) #',fn-name)))))
\f
;;;; boolean attribute utilities
;;;;
;;;; We need to maintain various sets of boolean attributes for known
;;;; functions and VOPs. To save space and allow for quick set
;;;; operations, we represent the attributes as bits in a fixnum.

(deftype attributes () 'fixnum)

(eval-when (:compile-toplevel :load-toplevel :execute)

;;; Given a list of attribute names and an alist that translates them
;;; to masks, return the OR of the masks.
(defun compute-attribute-mask (names alist)
  (collect ((res 0 logior))
    (dolist (name names)
      (let ((mask (cdr (assoc name alist))))
        (unless mask
          (error "unknown attribute name: ~S" name))
        (res mask)))
    (res)))

) ; EVAL-WHEN

;;; Define a new class of boolean attributes, with the attributes
;;; having the specified Attribute-Names. Name is the name of the
;;; class, which is used to generate some macros to manipulate sets of
;;; the attributes:
;;;
;;;    NAME-attributep attributes attribute-name*
;;;      Return true if one of the named attributes is present, false
;;;      otherwise. When set with SETF, updates the place Attributes
;;;      setting or clearing the specified attributes.
;;;
;;;    NAME-attributes attribute-name*
;;;      Return a set of the named attributes.
;;;
;;; KLUDGE: This is expanded out twice, by cut-and-paste, in a
;;;   (DEF!MACRO FOO (..) .. CL:GET-SETF-EXPANSION ..)
;;;   #+SB-XC-HOST
;;;   (SB!XC:DEFMACRO FOO (..) .. SB!XC:GET-SETF-EXPANSION ..)
;;; arrangement, in order to get it to work in cross-compilation. This
;;; duplication should be removed, perhaps by rewriting the macro in a
;;; more cross-compiler-friendly way, or perhaps just by using some
;;; (MACROLET ((FROB ..)) .. FROB .. FROB) form, but I don't want to
;;; do it now, because the system isn't running yet, so it'd be too
;;; hard to check that my changes were correct -- WHN 19990806
(def!macro def-boolean-attribute (name &rest attribute-names)

  (let ((translations-name (symbolicate "*" name "-ATTRIBUTE-TRANSLATIONS*"))
        (test-name (symbolicate name "-ATTRIBUTEP")))
    (collect ((alist))
      (do ((mask 1 (ash mask 1))
           (names attribute-names (cdr names)))
          ((null names))
        (alist (cons (car names) mask)))

      `(progn

         (eval-when (:compile-toplevel :load-toplevel :execute)
           (defparameter ,translations-name ',(alist)))

         (defmacro ,test-name (attributes &rest attribute-names)
           "Automagically generated boolean attribute test function. See
            Def-Boolean-Attribute."
           `(logtest ,(compute-attribute-mask attribute-names
                                              ,translations-name)
                     (the attributes ,attributes)))

         (define-setf-expander ,test-name (place &rest attributes
                                                 &environment env)
           "Automagically generated boolean attribute setter. See
            Def-Boolean-Attribute."
           #-sb-xc-host (declare (type sb!c::lexenv env))
           ;; FIXME: It would be better if &ENVIRONMENT arguments
           ;; were automatically declared to have type LEXENV by the
           ;; hairy-argument-handling code.
           (multiple-value-bind (temps values stores set get)
               (get-setf-expansion place env)
             (when (cdr stores)
               (error "multiple store variables for ~S" place))
             (let ((newval (gensym))
                   (n-place (gensym))
                   (mask (compute-attribute-mask attributes
                                                 ,translations-name)))
               (values `(,@temps ,n-place)
                       `(,@values ,get)
                       `(,newval)
                       `(let ((,(first stores)
                               (if ,newval
                                   (logior ,n-place ,mask)
                                   (logand ,n-place ,(lognot mask)))))
                          ,set
                          ,newval)
                       `(,',test-name ,n-place ,@attributes)))))

         (defmacro ,(symbolicate name "-ATTRIBUTES") (&rest attribute-names)
           "Automagically generated boolean attribute creation function. See
            Def-Boolean-Attribute."
           (compute-attribute-mask attribute-names ,translations-name))))))
;;; #+SB-XC-HOST SB!XC:DEFMACRO version is in late-macros.lisp. -- WHN 19990806

;;; And now for some gratuitous pseudo-abstraction...
;;;
;;; ATTRIBUTES-UNION 
;;;   Return the union of all the sets of boolean attributes which are its
;;;   arguments.
;;; ATTRIBUTES-INTERSECTION
;;;   Return the intersection of all the sets of boolean attributes which
;;;   are its arguments.
;;; ATTRIBUTES=
;;;   True if the attributes present in Attr1 are identical to
;;;   those in Attr2.
(defmacro attributes-union (&rest attributes)
  `(the attributes
        (logior ,@(mapcar #'(lambda (x) `(the attributes ,x)) attributes))))
(defmacro attributes-intersection (&rest attributes)
  `(the attributes
        (logand ,@(mapcar #'(lambda (x) `(the attributes ,x)) attributes))))
(declaim (ftype (function (attributes attributes) boolean) attributes=))
#!-sb-fluid (declaim (inline attributes=))
(defun attributes= (attr1 attr2)
  (eql attr1 attr2))
\f
;;;; lambda-list parsing utilities
;;;;
;;;; IR1 transforms, optimizers and type inferencers need to be able
;;;; to parse the IR1 representation of a function call using a
;;;; standard function lambda-list.

(eval-when (:compile-toplevel :load-toplevel :execute)

;;; Given a DEFTRANSFORM-style lambda-list, generate code that parses
;;; the arguments of a combination with respect to that lambda-list.
;;; BODY is the the list of forms which are to be evaluated within the
;;; bindings. ARGS is the variable that holds list of argument
;;; continuations. ERROR-FORM is a form which is evaluated when the
;;; syntax of the supplied arguments is incorrect or a non-constant
;;; argument keyword is supplied. Defaults and other gunk are ignored.
;;; The second value is a list of all the arguments bound. We make the
;;; variables IGNORABLE so that we don't have to manually declare them
;;; Ignore if their only purpose is to make the syntax work.
(defun parse-deftransform (lambda-list body args error-form)
  (multiple-value-bind (req opt restp rest keyp keys allowp)
      (parse-lambda-list lambda-list)
    (let* ((min-args (length req))
           (max-args (+ min-args (length opt)))
           (n-keys (gensym)))
      (collect ((binds)
                (vars)
                (pos 0 +)
                (keywords))
        (dolist (arg req)
          (vars arg)
          (binds `(,arg (nth ,(pos) ,args)))
          (pos 1))

        (dolist (arg opt)
          (let ((var (if (atom arg) arg (first  arg))))
            (vars var)
            (binds `(,var (nth ,(pos) ,args)))
            (pos 1)))

        (when restp
          (vars rest)
          (binds `(,rest (nthcdr ,(pos) ,args))))

        (dolist (spec keys)
          (if (or (atom spec) (atom (first spec)))
              (let* ((var (if (atom spec) spec (first spec)))
                     (key (keywordicate var)))
                (vars var)
                (binds `(,var (find-keyword-continuation ,n-keys ,key)))
                (keywords key))
              (let* ((head (first spec))
                     (var (second head))
                     (key (first head)))
                (vars var)
                (binds `(,var (find-keyword-continuation ,n-keys ,key)))
                (keywords key))))

        (let ((n-length (gensym))
              (limited-legal (not (or restp keyp))))
          (values
           `(let ((,n-length (length ,args))
                  ,@(when keyp `((,n-keys (nthcdr ,(pos) ,args)))))
              (unless (and
                       ;; FIXME: should be PROPER-LIST-OF-LENGTH-P
                       ,(if limited-legal
                            `(<= ,min-args ,n-length ,max-args)
                            `(<= ,min-args ,n-length))
                       ,@(when keyp
                           (if allowp
                               `((check-key-args-constant ,n-keys))
                               `((check-transform-keys ,n-keys ',(keywords))))))
                ,error-form)
              (let ,(binds)
                (declare (ignorable ,@(vars)))
                ,@body))
           (vars)))))))

) ; EVAL-WHEN
\f
;;;; DEFTRANSFORM

;;; Define an IR1 transformation for NAME. An IR1 transformation
;;; computes a lambda that replaces the function variable reference
;;; for the call. A transform may pass (decide not to transform the
;;; call) by calling the GIVE-UP-IR1-TRANSFORM function. LAMBDA-LIST
;;; both determines how the current call is parsed and specifies the
;;; LAMBDA-LIST for the resulting lambda.
;;;
;;; We parse the call and bind each of the lambda-list variables to
;;; the continuation which represents the value of the argument. When
;;; parsing the call, we ignore the defaults, and always bind the
;;; variables for unsupplied arguments to NIL. If a required argument
;;; is missing, an unknown keyword is supplied, or an argument keyword
;;; is not a constant, then the transform automatically passes. The
;;; DECLARATIONS apply to the bindings made by DEFTRANSFORM at
;;; transformation time, rather than to the variables of the resulting
;;; lambda. Bound-but-not-referenced warnings are suppressed for the
;;; lambda-list variables. The DOC-STRING is used when printing
;;; efficiency notes about the defined transform.
;;;
;;; Normally, the body evaluates to a form which becomes the body of
;;; an automatically constructed lambda. We make LAMBDA-LIST the
;;; lambda-list for the lambda, and automatically insert declarations
;;; of the argument and result types. If the second value of the body
;;; is non-null, then it is a list of declarations which are to be
;;; inserted at the head of the lambda. Automatic lambda generation
;;; may be inhibited by explicitly returning a lambda from the body.
;;;
;;; The ARG-TYPES and RESULT-TYPE are used to create a function type
;;; which the call must satisfy before transformation is attempted.
;;; The function type specifier is constructed by wrapping (FUNCTION
;;; ...) around these values, so the lack of a restriction may be
;;; specified by omitting the argument or supplying *. The argument
;;; syntax specified in the ARG-TYPES need not be the same as that in
;;; the LAMBDA-LIST, but the transform will never happen if the
;;; syntaxes can't be satisfied simultaneously. If there is an
;;; existing transform for the same function that has the same type,
;;; then it is replaced with the new definition.
;;;
;;; These are the legal keyword options:
;;;   :RESULT - A variable which is bound to the result continuation.
;;;   :NODE   - A variable which is bound to the combination node for the call.
;;;   :POLICY - A form which is supplied to the POLICY macro to determine
;;;             whether this transformation is appropriate. If the result
;;;             is false, then the transform automatically gives up.
;;;   :EVAL-NAME
;;;           - The name and argument/result types are actually forms to be
;;;             evaluated. Useful for getting closures that transform similar
;;;             functions.
;;;   :DEFUN-ONLY
;;;           - Don't actually instantiate a transform, instead just DEFUN
;;;             Name with the specified transform definition function. This
;;;             may be later instantiated with %DEFTRANSFORM.
;;;   :IMPORTANT
;;;           - If supplied and non-NIL, note this transform as ``important,''
;;;             which means efficiency notes will be generated when this
;;;             transform fails even if INHIBIT-WARNINGS=SPEED (but not if
;;;             INHIBIT-WARNINGS>SPEED).
;;;   :WHEN {:NATIVE | :BYTE | :BOTH}
;;;           - Indicates whether this transform applies to native code,
;;;             byte-code or both (default :native.)
(defmacro deftransform (name (lambda-list &optional (arg-types '*)
                                          (result-type '*)
                                          &key result policy node defun-only
                                          eval-name important (when :native))
                             &body body-decls-doc)
  (when (and eval-name defun-only)
    (error "can't specify both DEFUN-ONLY and EVAL-NAME"))
  (multiple-value-bind (body decls doc) (parse-body body-decls-doc)
    (let ((n-args (gensym))
          (n-node (or node (gensym)))
          (n-decls (gensym))
          (n-lambda (gensym))
          (decls-body `(,@decls ,@body)))
      (multiple-value-bind (parsed-form vars)
          (parse-deftransform lambda-list
                              (if policy
                                  `((unless (policy ,n-node ,policy)
                                      (give-up-ir1-transform))
                                    ,@decls-body)
                                  body)
                              n-args
                              '(give-up-ir1-transform))
        (let ((stuff
               `((,n-node)
                 (let* ((,n-args (basic-combination-args ,n-node))
                        ,@(when result
                            `((,result (node-cont ,n-node)))))
                   (multiple-value-bind (,n-lambda ,n-decls)
                       ,parsed-form
                     (if (and (consp ,n-lambda) (eq (car ,n-lambda) 'lambda))
                         ,n-lambda
                       `(lambda ,',lambda-list
                          (declare (ignorable ,@',vars))
                          ,@,n-decls
                          ,,n-lambda)))))))
          (if defun-only
              `(defun ,name ,@(when doc `(,doc)) ,@stuff)
              `(%deftransform
                ,(if eval-name name `',name)
                ,(if eval-name
                     ``(function ,,arg-types ,,result-type)
                     `'(function ,arg-types ,result-type))
                #'(lambda ,@stuff)
                ,doc
                ,(if important t nil)
                ,when)))))))
\f
;;;; DEFKNOWN and DEFOPTIMIZER

;;; This macro should be the way that all implementation independent
;;; information about functions is made known to the compiler.
;;;
;;; FIXME: The comment above suggests that perhaps some of my added
;;; FTYPE declarations are in poor taste. Should I change my
;;; declarations, or change the comment, or what?
;;;
;;; FIXME: DEFKNOWN is needed only at build-the-system time. Figure
;;; out some way to keep it from appearing in the target system.
;;;
;;; Declare the function NAME to be a known function. We construct a
;;; type specifier for the function by wrapping (FUNCTION ...) around
;;; the ARG-TYPES and RESULT-TYPE. ATTRIBUTES is an unevaluated list
;;; of boolean attributes of the function. These attributes are
;;; meaningful here:
;;;
;;;     CALL
;;;        May call functions that are passed as arguments. In order
;;;        to determine what other effects are present, we must find
;;;        the effects of all arguments that may be functions.
;;;
;;;     UNSAFE
;;;        May incorporate arguments in the result or somehow pass
;;;        them upward.
;;;
;;;     UNWIND
;;;        May fail to return during correct execution. Errors
;;;        are O.K.
;;;
;;;     ANY
;;;        The (default) worst case. Includes all the other bad
;;;        things, plus any other possible bad thing.
;;;
;;;     FOLDABLE
;;;        May be constant-folded. The function has no side effects,
;;;        but may be affected by side effects on the arguments. E.g.
;;;        SVREF, MAPC.
;;;
;;;     FLUSHABLE
;;;        May be eliminated if value is unused. The function has
;;;        no side effects except possibly CONS. If a function is
;;;        defined to signal errors, then it is not flushable even
;;;        if it is movable or foldable.
;;;
;;;     MOVABLE
;;;        May be moved with impunity. Has no side effects except
;;;        possibly CONS, and is affected only by its arguments.
;;;
;;;     PREDICATE
;;;         A true predicate likely to be open-coded. This is a
;;;         hint to IR1 conversion that it should ensure calls always
;;;         appear as an IF test. Not usually specified to DEFKNOWN,
;;;         since this is implementation dependent, and is usually
;;;         automatically set by the DEFINE-VOP :CONDITIONAL option.
;;;
;;; NAME may also be a list of names, in which case the same
;;; information is given to all the names. The keywords specify the
;;; initial values for various optimizers that the function might
;;; have.
(defmacro defknown (name arg-types result-type &optional (attributes '(any))
                         &rest keys)
  (when (and (intersection attributes '(any call unwind))
             (intersection attributes '(movable)))
    (error "function cannot have both good and bad attributes: ~S" attributes))

  `(%defknown ',(if (and (consp name)
                         (not (eq (car name) 'setf)))
                    name
                    (list name))
              '(function ,arg-types ,result-type)
              (ir1-attributes ,@(if (member 'any attributes)
                                    (union '(call unsafe unwind) attributes)
                                    attributes))
              ,@keys))

;;; Create a function which parses combination args according to WHAT
;;; and LAMBDA-LIST, where WHAT is either a function name or a list
;;; (FUN-NAME KIND) and does some KIND of optimization.
;;;
;;; The FUN-NAME must name a known function. LAMBDA-LIST is used
;;; to parse the arguments to the combination as in DEFTRANSFORM. If
;;; the argument syntax is invalid or there are non-constant keys,
;;; then we simply return NIL.
;;;
;;; The function is DEFUN'ed as FUNCTION-KIND-OPTIMIZER. Possible
;;; kinds are DERIVE-TYPE, OPTIMIZER, LTN-ANNOTATE and IR2-CONVERT. If
;;; a symbol is specified instead of a (FUNCTION KIND) list, then we
;;; just do a DEFUN with the symbol as its name, and don't do anything
;;; with the definition. This is useful for creating optimizers to be
;;; passed by name to DEFKNOWN.
;;;
;;; If supplied, NODE-VAR is bound to the combination node being
;;; optimized. If additional VARS are supplied, then they are used as
;;; the rest of the optimizer function's lambda-list. LTN-ANNOTATE
;;; methods are passed an additional POLICY argument, and IR2-CONVERT
;;; methods are passed an additional IR2-BLOCK argument.
(defmacro defoptimizer (what (lambda-list &optional (n-node (gensym))
                                          &rest vars)
                             &body body)
  (let ((name (if (symbolp what) what
                  (symbolicate (first what) "-" (second what) "-OPTIMIZER"))))

    (let ((n-args (gensym)))
      `(progn
        (defun ,name (,n-node ,@vars)
          (let ((,n-args (basic-combination-args ,n-node)))
            ,(parse-deftransform lambda-list body n-args
                                 `(return-from ,name nil))))
        ,@(when (consp what)
            `((setf (,(symbolicate "FUNCTION-INFO-" (second what))
                     (function-info-or-lose ',(first what)))
                    #',name)))))))
\f
;;;; IR groveling macros

;;; Iterate over the blocks in a component, binding BLOCK-VAR to each
;;; block in turn. The value of ENDS determines whether to iterate
;;; over dummy head and tail blocks:
;;;    NIL  -- Skip Head and Tail (the default)
;;;   :HEAD -- Do head but skip tail
;;;   :TAIL -- Do tail but skip head
;;;   :BOTH -- Do both head and tail
;;;
;;; If supplied, RESULT-FORM is the value to return.
(defmacro do-blocks ((block-var component &optional ends result) &body body)
  (unless (member ends '(nil :head :tail :both))
    (error "losing ENDS value: ~S" ends))
  (let ((n-component (gensym))
        (n-tail (gensym)))
    `(let* ((,n-component ,component)
            (,n-tail ,(if (member ends '(:both :tail))
                          nil
                          `(component-tail ,n-component))))
       (do ((,block-var ,(if (member ends '(:both :head))
                             `(component-head ,n-component)
                             `(block-next (component-head ,n-component)))
                        (block-next ,block-var)))
           ((eq ,block-var ,n-tail) ,result)
         ,@body))))
;;; like DO-BLOCKS, only iterating over the blocks in reverse order
(defmacro do-blocks-backwards ((block-var component &optional ends result) &body body)
  (unless (member ends '(nil :head :tail :both))
    (error "losing ENDS value: ~S" ends))
  (let ((n-component (gensym))
        (n-head (gensym)))
    `(let* ((,n-component ,component)
            (,n-head ,(if (member ends '(:both :head))
                          nil
                          `(component-head ,n-component))))
       (do ((,block-var ,(if (member ends '(:both :tail))
                             `(component-tail ,n-component)
                             `(block-prev (component-tail ,n-component)))
                        (block-prev ,block-var)))
           ((eq ,block-var ,n-head) ,result)
         ,@body))))

;;; Iterate over the uses of CONTINUATION, binding NODE to each one
;;; successively.
;;;
;;; XXX Could change it not to replicate the code someday perhaps...
(defmacro do-uses ((node-var continuation &optional result) &body body)
  (once-only ((n-cont continuation))
    `(ecase (continuation-kind ,n-cont)
       (:unused)
       (:inside-block
        (block nil
          (let ((,node-var (continuation-use ,n-cont)))
            ,@body
            ,result)))
       ((:block-start :deleted-block-start)
        (dolist (,node-var (block-start-uses (continuation-block ,n-cont))
                           ,result)
          ,@body)))))

;;; Iterate over the nodes in BLOCK, binding NODE-VAR to the each node
;;; and CONT-VAR to the node's CONT. The only keyword option is
;;; RESTART-P, which causes iteration to be restarted when a node is
;;; deleted out from under us. (If not supplied, this is an error.)
;;;
;;; In the forward case, we terminate on LAST-CONT so that we don't
;;; have to worry about our termination condition being changed when
;;; new code is added during the iteration. In the backward case, we
;;; do NODE-PREV before evaluating the body so that we can keep going
;;; when the current node is deleted.
;;;
;;; When RESTART-P is supplied to DO-NODES, we start iterating over
;;; again at the beginning of the block when we run into a
;;; continuation whose block differs from the one we are trying to
;;; iterate over, either because the block was split, or because a
;;; node was deleted out from under us (hence its block is NIL.) If
;;; the block start is deleted, we just punt. With RESTART-P, we are
;;; also more careful about termination, re-indirecting the BLOCK-LAST
;;; each time.
(defmacro do-nodes ((node-var cont-var block &key restart-p) &body body)
  (let ((n-block (gensym))
        (n-last-cont (gensym)))
    `(let* ((,n-block ,block)
            ,@(unless restart-p
                `((,n-last-cont (node-cont (block-last ,n-block))))))
       (do* ((,node-var (continuation-next (block-start ,n-block))
                        ,(if restart-p
                             `(cond
                               ((eq (continuation-block ,cont-var) ,n-block)
                                (aver (continuation-next ,cont-var))
                                (continuation-next ,cont-var))
                               (t
                                (let ((start (block-start ,n-block)))
                                  (unless (eq (continuation-kind start)
                                              :block-start)
                                    (return nil))
                                  (continuation-next start))))
                             `(continuation-next ,cont-var)))
             (,cont-var (node-cont ,node-var) (node-cont ,node-var)))
            (())
         ,@body
         (when ,(if restart-p
                    `(eq ,node-var (block-last ,n-block))
                    `(eq ,cont-var ,n-last-cont))
           (return nil))))))
;;; like Do-Nodes, only iterating in reverse order
(defmacro do-nodes-backwards ((node-var cont-var block) &body body)
  (let ((n-block (gensym))
        (n-start (gensym))
        (n-last (gensym))
        (n-next (gensym)))
    `(let* ((,n-block ,block)
            (,n-start (block-start ,n-block))
            (,n-last (block-last ,n-block)))
       (do* ((,cont-var (node-cont ,n-last) ,n-next)
             (,node-var ,n-last (continuation-use ,cont-var))
             (,n-next (node-prev ,node-var) (node-prev ,node-var)))
            (())
         ,@body
         (when (eq ,n-next ,n-start)
           (return nil))))))

;;; Bind the IR1 context variables so that IR1 conversion can be done
;;; after the main conversion pass has finished.
;;;
;;; The lexical environment is presumably already null...
(defmacro with-ir1-environment (node &rest forms)
  (let ((n-node (gensym)))
    `(let* ((,n-node ,node)
            (*current-component* (block-component (node-block ,n-node)))
            (*lexenv* (node-lexenv ,n-node))
            (*current-path* (node-source-path ,n-node)))
       ,@forms)))

;;; Bind the hashtables used for keeping track of global variables,
;;; functions, &c. Also establish condition handlers.
(defmacro with-ir1-namespace (&body forms)
  `(let ((*free-variables* (make-hash-table :test 'eq))
         (*free-functions* (make-hash-table :test 'equal))
         (*constants* (make-hash-table :test 'equal))
         (*source-paths* (make-hash-table :test 'eq)))
     (handler-bind ((compiler-error #'compiler-error-handler)
                    (style-warning #'compiler-style-warning-handler)
                    (warning #'compiler-warning-handler))
       ,@forms)))

;;; Look up NAME in the lexical environment namespace designated by
;;; SLOT, returning the <value, T>, or <NIL, NIL> if no entry. The
;;; :TEST keyword may be used to determine the name equality
;;; predicate.
(defmacro lexenv-find (name slot &key test)
  (once-only ((n-res `(assoc ,name (,(symbolicate "LEXENV-" slot) *lexenv*)
                             :test ,(or test '#'eq))))
    `(if ,n-res
         (values (cdr ,n-res) t)
         (values nil nil))))
\f
;;;; the EVENT statistics/trace utility

;;; FIXME: This seems to be useful for troubleshooting and
;;; experimentation, not for ordinary use, so it should probably
;;; become conditional on SB-SHOW.

(eval-when (:compile-toplevel :load-toplevel :execute)

(defstruct (event-info (:copier nil))
  ;; The name of this event.
  (name (missing-arg) :type symbol)
  ;; The string rescribing this event.
  (description (missing-arg) :type string)
  ;; The name of the variable we stash this in.
  (var (missing-arg) :type symbol)
  ;; The number of times this event has happened.
  (count 0 :type fixnum)
  ;; The level of significance of this event.
  (level (missing-arg) :type unsigned-byte)
  ;; If true, a function that gets called with the node that the event
  ;; happened to.
  (action nil :type (or function null)))

;;; A hashtable from event names to event-info structures.
(defvar *event-info* (make-hash-table :test 'eq))

;;; Return the event info for Name or die trying.
(declaim (ftype (function (t) event-info) event-info-or-lose))
(defun event-info-or-lose (name)
  (let ((res (gethash name *event-info*)))
    (unless res
      (error "~S is not the name of an event." name))
    res))

) ; EVAL-WHEN

;;; Return the number of times that EVENT has happened.
(declaim (ftype (function (symbol) fixnum) event-count))
(defun event-count (name)
  (event-info-count (event-info-or-lose name)))

;;; Return the function that is called when Event happens. If this is
;;; null, there is no action. The function is passed the node to which
;;; the event happened, or NIL if there is no relevant node. This may
;;; be set with SETF.
(declaim (ftype (function (symbol) (or function null)) event-action))
(defun event-action (name)
  (event-info-action (event-info-or-lose name)))
(declaim (ftype (function (symbol (or function null)) (or function null))
                %set-event-action))
(defun %set-event-action (name new-value)
  (setf (event-info-action (event-info-or-lose name))
        new-value))
(defsetf event-action %set-event-action)

;;; Return the non-negative integer which represents the level of
;;; significance of the event Name. This is used to determine whether
;;; to print a message when the event happens. This may be set with
;;; SETF.
(declaim (ftype (function (symbol) unsigned-byte) event-level))
(defun event-level (name)
  (event-info-level (event-info-or-lose name)))
(declaim (ftype (function (symbol unsigned-byte) unsigned-byte) %set-event-level))
(defun %set-event-level (name new-value)
  (setf (event-info-level (event-info-or-lose name))
        new-value))
(defsetf event-level %set-event-level)

;;; Define a new kind of event. Name is a symbol which names the event
;;; and Description is a string which describes the event. Level
;;; (default 0) is the level of significance associated with this
;;; event; it is used to determine whether to print a Note when the
;;; event happens.
(defmacro defevent (name description &optional (level 0))
  (let ((var-name (symbolicate "*" name "-EVENT-INFO*")))
    `(eval-when (:compile-toplevel :load-toplevel :execute)
       (defvar ,var-name
         (make-event-info :name ',name
                          :description ',description
                          :var ',var-name
                          :level ,level))
       (setf (gethash ',name *event-info*) ,var-name)
       ',name)))

;;; the lowest level of event that will print a note when it occurs
(declaim (type unsigned-byte *event-note-threshold*))
(defvar *event-note-threshold* 1)

;;; Note that the event with the specified Name has happened. Node is
;;; evaluated to determine the node to which the event happened.
(defmacro event (name &optional node)
  ;; Increment the counter and do any action. Mumble about the event if
  ;; policy indicates.
  `(%event ,(event-info-var (event-info-or-lose name)) ,node))

;;; Print a listing of events and their counts, sorted by the count.
;;; Events that happened fewer than Min-Count times will not be
;;; printed. Stream is the stream to write to.
(declaim (ftype (function (&optional unsigned-byte stream) (values)) event-statistics))
(defun event-statistics (&optional (min-count 1) (stream *standard-output*))
  (collect ((info))
    (maphash #'(lambda (k v)
                 (declare (ignore k))
                 (when (>= (event-info-count v) min-count)
                   (info v)))
             *event-info*)
    (dolist (event (sort (info) #'> :key #'event-info-count))
      (format stream "~6D: ~A~%" (event-info-count event)
              (event-info-description event)))
    (values))
  (values))

(declaim (ftype (function nil (values)) clear-event-statistics))
(defun clear-event-statistics ()
  (maphash #'(lambda (k v)
               (declare (ignore k))
               (setf (event-info-count v) 0))
           *event-info*)
  (values))
\f
;;;; functions on directly-linked lists (linked through specialized
;;;; NEXT operations)

#!-sb-fluid (declaim (inline find-in position-in map-in))

;;; Find Element in a null-terminated List linked by the accessor
;;; function Next. Key, Test and Test-Not are the same as for generic
;;; sequence functions.
(defun find-in (next
                element
                list
                &key
                (key #'identity)
                (test #'eql test-p)
                (test-not nil not-p))
  (when (and test-p not-p)
    (error "It's silly to supply both :TEST and :TEST-NOT arguments."))
  (if not-p
      (do ((current list (funcall next current)))
          ((null current) nil)
        (unless (funcall test-not (funcall key current) element)
          (return current)))
      (do ((current list (funcall next current)))
          ((null current) nil)
        (when (funcall test (funcall key current) element)
          (return current)))))

;;; Return the position of Element (or NIL if absent) in a
;;; null-terminated List linked by the accessor function Next. Key,
;;; Test and Test-Not are the same as for generic sequence functions.
(defun position-in (next
                    element
                    list
                    &key
                    (key #'identity)
                    (test #'eql test-p)
                    (test-not nil not-p))
  (when (and test-p not-p)
    (error "It's silly to supply both :TEST and :TEST-NOT arguments."))
  (if not-p
      (do ((current list (funcall next current))
           (i 0 (1+ i)))
          ((null current) nil)
        (unless (funcall test-not (funcall key current) element)
          (return i)))
      (do ((current list (funcall next current))
           (i 0 (1+ i)))
          ((null current) nil)
        (when (funcall test (funcall key current) element)
          (return i)))))

;;; Map FUNCTION over the elements in a null-terminated LIST linked by the
;;; accessor function NEXT, returning an ordinary list of the results.
(defun map-in (next function list)
  (collect ((res))
    (do ((current list (funcall next current)))
        ((null current))
      (res (funcall function current)))
    (res)))

;;; KLUDGE: This is expanded out twice, by cut-and-paste, in a
;;;   (DEF!MACRO FOO (..) .. CL:GET-SETF-EXPANSION ..)
;;;   #+SB-XC-HOST
;;;   (SB!XC:DEFMACRO FOO (..) .. SB!XC:GET-SETF-EXPANSION ..)
;;; arrangement, in order to get it to work in cross-compilation. This
;;; duplication should be removed, perhaps by rewriting the macro in a more
;;; cross-compiler-friendly way, or perhaps just by using some (MACROLET ((FROB
;;; ..)) .. FROB .. FROB) form, or perhaps by completely eliminating this macro
;;; and its partner PUSH-IN, but I don't want to do it now, because the system
;;; isn't running yet, so it'd be too hard to check that my changes were
;;; correct -- WHN 19990806
(def!macro deletef-in (next place item &environment env)
  (multiple-value-bind (temps vals stores store access)
      (get-setf-expansion place env)
    (when (cdr stores)
      (error "multiple store variables for ~S" place))
    (let ((n-item (gensym))
          (n-place (gensym))
          (n-current (gensym))
          (n-prev (gensym)))
      `(let* (,@(mapcar #'list temps vals)
              (,n-place ,access)
              (,n-item ,item))
         (if (eq ,n-place ,n-item)
             (let ((,(first stores) (,next ,n-place)))
               ,store)
             (do ((,n-prev ,n-place ,n-current)
                  (,n-current (,next ,n-place)
                              (,next ,n-current)))
                 ((eq ,n-current ,n-item)
                  (setf (,next ,n-prev)
                        (,next ,n-current)))))
         (values)))))
;;; #+SB-XC-HOST SB!XC:DEFMACRO version is in late-macros.lisp. -- WHN 19990806

;;; Push ITEM onto a list linked by the accessor function NEXT that is
;;; stored in PLACE.
;;;
;;; KLUDGE: This is expanded out twice, by cut-and-paste, in a
;;;   (DEF!MACRO FOO (..) .. CL:GET-SETF-EXPANSION ..)
;;;   #+SB-XC-HOST
;;;   (SB!XC:DEFMACRO FOO (..) .. SB!XC:GET-SETF-EXPANSION ..)
;;; arrangement, in order to get it to work in cross-compilation. This
;;; duplication should be removed, perhaps by rewriting the macro in a more
;;; cross-compiler-friendly way, or perhaps just by using some (MACROLET ((FROB
;;; ..)) .. FROB .. FROB) form, or perhaps by completely eliminating this macro
;;; and its partner DELETEF-IN, but I don't want to do it now, because the
;;; system isn't running yet, so it'd be too hard to check that my changes were
;;; correct -- WHN 19990806
(def!macro push-in (next item place &environment env)
  (multiple-value-bind (temps vals stores store access)
      (get-setf-expansion place env)
    (when (cdr stores)
      (error "multiple store variables for ~S" place))
    `(let (,@(mapcar #'list temps vals)
           (,(first stores) ,item))
       (setf (,next ,(first stores)) ,access)
       ,store
       (values))))
;;; #+SB-XC-HOST SB!XC:DEFMACRO version is in late-macros.lisp. -- WHN 19990806

(defmacro position-or-lose (&rest args)
  `(or (position ,@args)
       (error "shouldn't happen?")))