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;;; -*- Package: C; Log: C.Log -*-
;;;
;;; **********************************************************************
;;; This code was written as part of the Spice Lisp project at
;;; Carnegie-Mellon University, and has been placed in the public domain.
;;; If you want to use this code or any part of Spice Lisp, please contact
;;; Scott Fahlman (FAHLMAN@CMUC). 
;;; **********************************************************************
;;;
;;;    This file contains implementation-independent facilities used for
;;; defining the compiler's interface to the VM in a given implementation.
;;;
;;; Written by Rob MacLachlan
;;;
(in-package 'c)

;;;
;;; Translates from SC numbers to SC info structures.  SC numbers are always
;;; used instead of names at run time, so changing this vector changes all the
;;; references.
(defvar *sc-numbers* (make-array sc-number-limit))
(proclaim '(type sc-vector *sc-numbers*))

;;;
;;; A list of all the SBs defined, so that we can easily iterate over them.
(defvar *sb-list* ())
(proclaim '(type list *sb-list*))

;;;
;;; Translates from template names to template structures.
(defvar *template-names* (make-hash-table :test #'eq))
(proclaim '(type hash-table *template-names*))

;;; Template-Or-Lose  --  Internal
;;;
;;;    Return the template having the specified name, or die trying.
;;;
(defun template-or-lose (x)
  (the template
       (or (gethash x *template-names*)
	   (error "~S is not a defined template." x))))


(eval-when (compile load eval)

;;; Hashtable from SC and SB names the corresponding structures.  The META
;;; versions are only used at meta-compile and load times, so the defining
;;; macros can change these at meta-compile time without breaking the compiler.
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;;;
(defvar *sc-names* (make-hash-table :test #'eq))
(defvar *sb-names* (make-hash-table :test #'eq))
(defvar *meta-sc-names* (make-hash-table :test #'eq))
(defvar *meta-sb-names* (make-hash-table :test #'eq))
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(proclaim '(hash-table *sc-names* *sb-names*))

;;;
;;; Like *SC-Numbers*, but is updated at meta-compile time.
(defvar *meta-sc-numbers* (make-array sc-number-limit))
(proclaim '(type sc-vector *meta-sc-numbers*))


;;; SC-Or-Lose, SB-Or-Lose, SC-Number-Or-Lose  --  Internal
;;;
;;;    Return the SC structure, SB structure or SC number corresponding to a
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;;;
(defun sc-or-lose (x)
  (the sc
       (or (gethash x *sc-names*)
	   (error "~S is not a defined storage class." x))))
;;;
(defun sb-or-lose (x)
  (the sb
       (or (gethash x *sb-names*)
	   (error "~S is not a defined storage base." x))))
;;;
(defun sc-number-or-lose (x)
  (the sc-number (sc-number (sc-or-lose x))))


;;; META-SC-OR-LOSE, META-SB-OR-LOSE, META-SC-NUMBER-OR-LOSE  --  Internal
;;;
;;;    Like the non-meta versions, but go for the meta-compile-time info.
;;; These should not be used after load time, since compiling the compiler
;;; changes the definitions.
;;;
(defun meta-sc-or-lose (x)
  (the sc
       (or (gethash x *meta-sc-names*)
	   (error "~S is not a defined storage class." x))))
;;;
(defun meta-sb-or-lose (x)
  (the sb
       (or (gethash x *meta-sb-names*)
	   (error "~S is not a defined storage base." x))))
;;;
(defun meta-sc-number-or-lose (x)
  (the sc-number (sc-number (meta-sc-or-lose x))))

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); Eval-When (Compile Load Eval)


;;;; Storage class and storage base definition:

;;; Define-Storage-Base  --  Public
;;;
;;;    Enter the basic structure at meta-compile time, and then fill in the
;;; missing slots at load time.
;;;
(defmacro define-storage-base (name kind &key size)
  "Define-Storage-Base Name Kind {Key Value}*
  Define a storage base having the specified Name.  Kind may be :Finite,
  :Unbounded or :Non-Packed.  The following keywords are legal:

  :Size <Size>
      Specify the number of locations in a :Finite SB or the initial size of a
      :Unbounded SB."
  (check-type name symbol)
  (check-type kind (member :finite :unbounded :non-packed))
  (ecase kind
    (:non-packed
     (when size
       (error "Size specification meaningless in a ~S SB." kind)))
    ((:finite :unbounded)
     (unless size (error "Size not specified in a ~S SB." kind))
     (check-type size unsigned-byte)))
    
  (let ((res (if (eq kind :non-packed)
		 (make-sb :name name :kind kind)
		 (make-finite-sb :name name :kind kind :size size))))
    `(progn
       (eval-when (compile load eval)
	 (setf (gethash ',name *meta-sb-names*) ',res))
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       ,(if (eq kind :non-packed)
	    `(setf (gethash ',name *sb-names*) (copy-sb ',res))
	    `(let ((res (copy-finite-sb ',res)))
	       (setf (finite-sb-always-live res)
		     (make-array ',size :initial-element #*))
	       (setf (finite-sb-conflicts res)
		     (make-array ',size :initial-element '#()))
	       (setf (finite-sb-live-tns res)
		     (make-array ',size :initial-element nil))
	       (setf (gethash ',name *sb-names*) res)))

       (setq *sb-list* (cons (sb-or-lose ',name)
			     (remove ',name *sb-list* :key #'sb-name)))
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       ',name)))


;;; Define-Storage-Class  --  Public
;;;
;;;
(defmacro define-storage-class (name number sb-name &key (element-size '1) 
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				     locations save-p alternate-scs
				     constant-scs)
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  "Define-Storage-Class Name Number Storage-Base {Key Value}*
  Define a storage class Name that uses the named Storage-Base.  Number is a
  small, non-negative integer that is used as an alias.  The following
  keywords are defined:

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  :Element-Size Size
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      The size of objects in this SC in whatever units the SB uses.  This
      defaults to 1.

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  :Locations (Location*)
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      If the SB is :Finite, then this is a list of the offsets within the SB
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      that are in this SC.

  :Save-P {T | NIL}
      If T, then values stored in this SC must be saved in one of the
      non-save-p :Alternate-SCs across calls.

  :Alternate-SCs (SC*)
      Indicates other SCs that can be used to hold values from this SC across
      calls or when storage in this SC is exhausted.  The SCs should be
      specified in order of decreasing \"goodness\".  Unless this SC is only
      used for restricted or wired TNs, then there must be a last SC in an
      unbounded SB.

  :Constant-SCs (SC*)
      A list of the names of all the constant SCs that can be loaded into this
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  (check-type name symbol)
  (check-type number sc-number)
  (check-type sb-name symbol)
  (check-type locations list)
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  (check-type save-p boolean)
  (check-type alternate-scs list)
  (check-type constant-scs list)
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  (let ((sb (meta-sb-or-lose sb-name)))
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    (if (eq (sb-kind sb) :finite)
	(let ((size (sb-size sb))
	      (element-size (eval element-size)))
	  (check-type element-size unsigned-byte)
	  (dolist (el locations)
	    (check-type el unsigned-byte)
	    (unless (<= 1 (+ el element-size) size)
	      (error "SC element ~D out of bounds for ~S." el sb))))
	(when locations
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	  (error ":Locations is meaningless in a ~S SB." (sb-kind sb))))

    (when (and (or alternate-scs constant-scs)
	       (eq (sb-kind sb) :non-packed))
      (error "Meaningless to specify alternate or constant SCs in a ~S SB."
	     (sb-kind sb))))

  (let ((nstack-p
	 (if (or (eq sb-name 'non-descriptor-stack)
		 (find 'non-descriptor-stack
		       (mapcar #'meta-sc-or-lose alternate-scs)
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		       :key #'(lambda (x)
				(sb-name (sc-sb x)))))
	     t nil)))
    `(progn
       (eval-when (compile load eval)
	 (let ((res (make-sc :name ',name :number ',number
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			     :sb (meta-sb-or-lose ',sb-name)
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			     :element-size ,element-size
			     :locations ',locations
			     :save-p ',save-p
			     :number-stack-p ,nstack-p
			     :alternate-scs (mapcar #'meta-sc-or-lose
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						    ',alternate-scs)
			     :constant-scs (mapcar #'meta-sc-or-lose
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						   ',constant-scs))))
	   (setf (gethash ',name *meta-sc-names*) res)
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	   (setf (svref *meta-sc-numbers* ',number) res)
	   (setf (svref (sc-load-costs res) ',number) 0)))
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       (let ((old (svref *sc-numbers* ',number)))
	 (when (and old (not (eq (sc-name old) ',name)))
	   (warn "Redefining SC number ~D from ~S to ~S." ',number
		 (sc-name old) ',name)))
       
       (setf (svref *sc-numbers* ',number) (meta-sc-or-lose ',name))
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       (setf (gethash ',name *sc-names*) (meta-sc-or-lose ',name))
       (setf (sc-sb (sc-or-lose ',name)) (sb-or-lose ',sb-name))
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       ',name)))
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;;;; Move/coerce definition:
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;;; DO-SC-PAIRS  --  Internal
;;;
;;;    Given a list of paris of lists of SCs (as given to DEFINE-MOVE-VOP,
;;; etc.), bind TO-SC and FROM-SC to all the combinations.
;;;
(eval-when (compile load eval)
  (defmacro do-sc-pairs ((from-sc-var to-sc-var scs) &body body)
    `(do ((froms ,scs (cddr froms))
	  (tos (cdr ,scs) (cddr tos)))
	 ((null froms))
       (dolist (from (car froms))
	 (let ((,from-sc-var (meta-sc-or-lose from)))
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	   (dolist (to (car tos))
	     (let ((,to-sc-var (meta-sc-or-lose to)))
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	       ,@body)))))))


;;; DEFINE-MOVE-FUNCTION  --  Public
;;;
(defmacro define-move-function ((name cost) lambda-list scs &body body)
  "Define-Move-Function (Name Cost) lambda-list ({(From-SC*) (To-SC*)}*) form*
  Define the function Name and note it as the function used for moving operands
  from the From-SCs to the To-SCs.  Cost is the cost of this move operation.
  The function is called with three arguments: the VOP (for context), and the
  source and destination TNs.  An ASSEMBLE form is wrapped around the body.
  All uses of DEFINE-MOVE-FUNCTION should be compiled before any uses of
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  DEFINE-VOP."
  (when (or (oddp (length scs)) (null scs))
    (error "Malformed SCs spec: ~S." scs))
  (check-type cost index)
  `(progn
     (eval-when (compile load eval)
       (do-sc-pairs (from-sc to-sc ',scs)
	 (unless (eq from-sc to-sc)
	   (let ((num (sc-number from-sc)))
	     (setf (svref (sc-move-functions to-sc) num) ',name)
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	     (setf (svref (sc-load-costs to-sc) num) ',cost)))))

     (defun ,name ,lambda-list
       (assemble (*code-segment* ,(first lambda-list))
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(defconstant sc-vop-slots '((:move . sc-move-vops)
			    (:move-argument . sc-move-arg-vops)))


;;; COMPUTE-MOVE-COSTS  --  Internal
;;;
;;;    Compute at meta-compile time the costs for moving between all SCs that
;;; can be loaded from FROM-SC and to TO-SC given a base move cost Cost.
;;;
(defun compute-move-costs (from-sc to-sc cost)
  (declare (type sc from-sc to-sc) (type index cost))
  (let ((to-scn (sc-number to-sc))
	(from-costs (sc-load-costs from-sc)))
    (dolist (dest-sc (cons to-sc (sc-alternate-scs to-sc)))
      (let ((vec (sc-move-costs dest-sc))
	    (dest-costs (sc-load-costs dest-sc)))
	(setf (svref vec (sc-number from-sc)) cost)
	(dolist (sc (append (sc-alternate-scs from-sc)
			    (sc-constant-scs from-sc)))
	  (let* ((scn (sc-number sc))
		 (total (+ (svref from-costs scn)
			   (svref dest-costs to-scn)
			   cost))
		 (old (svref vec scn)))
	    (unless (and old (< old total))
	      (setf (svref vec scn) total))))))))
    
    
;;; DEFINE-MOVE-VOP  --  Public
;;;
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;;;    We record the VOP and costs for all SCs that we can move between
;;; (including implicit loading).
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;;;
(defmacro define-move-vop (name kind &rest scs)
  "Define-Move-VOP Name {:Move | :Move-Argument} {(From-SC*) (To-SC*)}*
  Make Name be the VOP used to move values in the specified From-SCs to the
  representation of the To-SCs.  If kind is :Move-Argument, then the VOP takes
  an extra argument, which is the frame pointer of the frame to move into." 
  (when (or (oddp (length scs)) (null scs))
    (error "Malformed SCs spec: ~S." scs))
  (let ((accessor (or (cdr (assoc kind sc-vop-slots))
		      (error "Unknown kind ~S." kind))))
    `(progn
       ,@(when (eq kind :move)
	   `((eval-when (compile load eval)
	       (do-sc-pairs (from-sc to-sc ',scs)
		 (compute-move-costs from-sc to-sc
				     ,(vop-parse-cost
				       (vop-parse-or-lose name)))))))
       
       (let ((vop (template-or-lose ',name)))
	 (do-sc-pairs (from-sc to-sc ',scs)
	   (dolist (dest-sc (cons to-sc (sc-alternate-scs to-sc)))
	     (let ((vec (,accessor dest-sc)))
	       (setf (svref vec (sc-number from-sc)) vop)
	       (dolist (sc (append (sc-alternate-scs from-sc)
				   (sc-constant-scs from-sc)))
		 (let ((scn (sc-number sc)))
		   (unless (svref vec scn) 
		     (setf (svref vec scn) vop)))))))))))
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;;;; Primitive type definition:

;;; Translates from primitive type names to the corresponding primitive-type
;;; structure.
;;;
(defvar *primitive-type-names* (make-hash-table :test #'eq))

;;; Establishes a convenient handle on primitive type unions, or whatever.
;;; These names can only be used as the :arg-types or :result-types for VOPs
;;; and can map to anything else that can be used as :arg-types or
;;; :result-types (e.g. :or, :constant).
;;; 
(defvar *primitive-type-aliases* (make-hash-table :test #'eq))

;;; Meta-compile time translation from names to primitive types.
;;;
(eval-when (compile load eval)
  (defvar *meta-primitive-type-names* (make-hash-table :test #'eq)))


;;; PRIMITIVE-TYPE-OR-LOSE, META-PRIMITIVE-TYPE-OR-LOSE  --  Interface
;;;
;;;    Return the primitive type corresponding to the specified name, or die
;;; trying.
;;;
(defun primitive-type-or-lose (name)
  (the primitive-type
       (or (gethash name *primitive-type-names*)
	   (error "~S is not a defined primitive type." name))))
;;;
(defun meta-primitive-type-or-lose (name)
  (the primitive-type
       (or (gethash name *meta-primitive-type-names*)
	   (error "~S is not a defined primitive type." name))))


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;;; The primitive type T is somewhat magical, in that it is the only primitive
;;; type that overlaps with other primitive types.  An object of primitive-type
;;; T is in the canonical descriptor (boxed or pointer) representation.
;;;
;;; We stick the T primitive-type in a variable so that people who have to
;;; special-case it can get at it conveniently.  This is done by the machine
;;; specific VM definition, since the DEF-PRIMITIVE-TYPE for T must specify the
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;;; SCs that boxed objects can be allocated in.
;;;
(proclaim '(special *any-primitive-type*))
(proclaim '(type primitive-type *any-primitive-type*))


;;; Def-Primitive-Type  --  Public
;;;
;;;    If the primitive-type structure already exists, we destructively modify
;;; it so that existing references in templates won't be invalidated.
;;; Primitive-type definition isn't done at meta-compile time, so this doesn't
;;; break the running compiler.
;;;
(defmacro def-primitive-type (name scs &key (type name))
  "Def-Primitive-Type Name (SC*) {Key Value}*
   Define a primitive type Name.  Each SC specifies a Storage Class that values
   of this type may be allocated in.  The following keyword options are
   defined:
  
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  :Type
      The type descriptor for the Lisp type that is equivalent to this type
      (defaults to Name.)"
  (check-type name symbol)
  (check-type scs list)
  (let ((scns (mapcar #'meta-sc-number-or-lose scs))
	(get-type `(specifier-type ',type)))
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    `(progn
       (eval-when (compile load eval)
	 (setf (gethash ',name *meta-primitive-type-names*)
	       (make-primitive-type :name ',name  :scs ',scns
				    ;; ### Bootstrap hack: The type system
				    ;; isn't avaiable during cross compile.
				    :type (if (fboundp 'specifier-type)
					      ,get-type))))
       ,(once-only ((n-old `(gethash ',name *primitive-type-names*))
		    (n-type get-type))
	  `(progn
	     (cond (,n-old
		    (setf (primitive-type-scs ,n-old) ',scns)
		    (setf (primitive-type-type ,n-old) ,n-type))
		   (t
		    (setf (gethash ',name *primitive-type-names*)
			  (make-primitive-type :name ',name  :scs ',scns
					       :type ,n-type))))
	     ',name)))))
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;;; Def-Primitive-Type-Alias  --  Public
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;;;
;;; Just record the translation.
;;; 
(defmacro def-primitive-type-alias (name result)
  "DEF-PRIMITIVE-TYPE-ALIAS Name Result
  Define name to be an alias for Result in VOP operand type restrictions."
  `(eval-when (compile load eval)
     (setf (gethash ',name *primitive-type-aliases*)
	   ',result)
     ',name))
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(eval-when (compile load eval)
  (defparameter primitive-type-slot-alist
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    '((:check . primitive-type-check))))
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;;; Primitive-Type-Vop  --  Public
;;;
(defmacro primitive-type-vop (vop kinds &rest types)
  "Primitive-Type-VOP Vop (Kind*) Type*
  Annotate all the specified primitive Types with the named VOP under each of
  the specified kinds:

  :Check
      A one argument one result VOP that moves the argument to the result,
      checking that the value is of this type in the process."
  (let ((n-vop (gensym))
	(n-type (gensym)))
    `(let ((,n-vop (template-or-lose ',vop)))
       ,@(mapcar
	  #'(lambda (type)
	      `(let ((,n-type (primitive-type-or-lose ',type)))
		 ,@(mapcar
		    #'(lambda (kind)
			(let ((slot (or (cdr (assoc kind
						    primitive-type-slot-alist))
					(error "Unknown kind: ~S." kind))))
			  `(setf (,slot ,n-type) ,n-vop)))
		    kinds)))
	  types)
       nil)))


;;; SC-ALLOWED-BY-PRIMITIVE-TYPE  --  Interface
;;;
;;;    Return true if SC is either one of Ptype's SC's, or one of those SC's
;;; alternate or constant SCs.  If Meta-P is true, use meta-compile time info.
;;;
(defun sc-allowed-by-primitive-type (sc ptype &optional meta-p)
  (declare (type sc sc) (type primitive-type ptype))
  (let ((scn (sc-number sc)))
    (dolist (allowed (primitive-type-scs ptype) nil)
      (when (eql allowed scn)
	(return t))
      (let ((allowed-sc (svref (if meta-p
				   *meta-sc-numbers*
				   *sc-numbers*)
			       allowed)))
	(when (or (member sc (sc-alternate-scs allowed-sc))
		  (member sc (sc-constant-scs allowed-sc)))
	  (return t))))))

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;;;; VOP definition structures:
;;;
;;;    Define-VOP uses some fairly complex data structures at meta-compile
;;; time, both to hold the results of parsing the elaborate syntax and to
;;; retain the information so that it can be inherited by other VOPs.

(eval-when (compile load eval)

;;;
;;; Hashtable translating from VOP names to the corresponding VOP-Parse
;;; structures.  This information is only used at meta-compile time.
(defvar *parsed-vops* (make-hash-table :test #'eq))
(proclaim '(type hash-table *parsed-vops*))

;;; The VOP-Parse structure holds everything we need to know about a VOP at
;;; meta-compile time.
;;;
(defstruct (vop-parse
	    (:print-function %print-vop-parse))
  ;;
  ;; The name of this VOP.
  (name nil :type symbol)
  ;;
  ;; If true, then the name of the VOP we inherit from.
  (inherits nil :type (or symbol null))
  ;;
  ;; Lists of Operand-Parse structures describing the arguments, results and
  ;; temporaries of the VOP.
  (args nil :type list)
  (results nil :type list)
  (temps nil :type list)
  ;;
  ;; Operand-Parse structures containing information about more args and
  ;; results.  If null, then there there are no more operands of that kind.
  (more-args nil :type (or operand-parse null))
  (more-results nil :type (or operand-parse null))
  ;;
  ;; A list of all the above together.
  (operands nil :type list)
  ;;
  ;; Names of variables that should be declared ignore.
  (ignores () :type list)
  ;;
  ;; True if this is a :Conditional VOP.
  (conditional-p nil)
  ;;
  ;; Argument and result primitive types.  These are pulled out of the
  ;; operands, since we often want to change them without respecifying the
  ;; operands.
  (arg-types :unspecified :type (or (member :unspecified) list))
  (result-types :unspecified :type (or (member :unspecified) list))
  ;;
  ;; The guard expression specified, or NIL if none.
  (guard nil)
  ;;
  ;; The cost of and body code for the generator.
  (cost 0 :type unsigned-byte)
  (body :unspecified :type (or (member :unspecified) list))
  ;;
  ;; Info for VOP variants.  The list of forms to be evaluated to get the
  ;; variant args for this VOP, and the list of variables to be bound to the
  ;; variant args.
  (variant () :type list)
  (variant-vars () :type list)
  ;;
  ;; Variables bound to the VOP and Vop-Node when in the generator body.
  (vop-var (gensym) :type symbol)
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  (node-var nil :type (or symbol null))
  ;;
  ;; A list of the names of the codegen-info arguments to this VOP.
  (info-args () :type list)
  ;;
  ;; An efficiency note associated with this VOP.
  (note nil :type (or string null))
  ;;
  ;; A list of the names of the Effects and Affected attributes for this VOP.
  (effects '(any) :type list)
  (affected '(any) :type list)
  ;;
  ;; A list of the names of functions this VOP is a translation of and the
  ;; policy that allows this translation to be done.  :Fast is a safe default,
  ;; since it isn't a safe policy.
  (translate () :type list)
  (policy :fast :type policies)
  ;;
  ;; Stuff used by life analysis.
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  (save-p nil :type (member t nil :compute-only :force-to-stack))
  ;;
  ;; Info about how to emit move-argument VOPs for the more operand in
  ;; call/return VOPs.
  (move-args nil :type (member nil :local-call :full-call :known-return)))

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(defprinter vop-parse
  name
  (inherits :test inherits)
  args
  results
  temps
  (more-args :test more-args)
  (more-results :test more-results)
  (conditional-p :test conditional-p)
  ignores
  arg-types
  result-types
  cost
  body
  (variant :test variant)
  (variant-vars :test variant-vars)
  (info-args :test info-args)
  (note :test note)
  effects
  affected
  translate
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  policy
  (save-p :test save-p)
  (move-args :test move-args))
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;;; The Operand-Parse structure contains stuff we need to know about and
;;; operand or temporary at meta-compile time.  Besides the obvious stuff, we
;;; also store the names of per-operand temporaries here.
;;;
(defstruct (operand-parse
	    (:print-function %print-operand-parse))
  ;;
  ;; Name of the operand (which we bind to the TN).
  (name nil :type symbol)
  ;;
  ;; The way this operand is used:
  (kind nil :type (member :argument :result :temporary
			  :more-argument :more-result))
  ;;
  ;; If true, the name of an operand that this operand is targeted to.  This is
  ;; only meaningful in :Argument and :Temporary operands.
  (target nil :type (or symbol null))
  ;;
  ;; Temporary that holds the TN-Ref for this operand.  Temp-Temp holds the
  ;; write reference that begins a temporary's lifetime.
  (temp (gensym) :type symbol)
  (temp-temp nil :type (or symbol null))
  ;;
  ;; The time that this operand is first live and the time at which it becomes
  ;; dead again.  These are time-specs, as returned by parse-time-spec. 
  born
  dies
  ;;
  ;; A list of the names of the SCs that this operand is allowed into.  If
  ;; false, there is no restriction.
  (scs nil :type list)
  ;;
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  ;; Variable that is bound to the load TN allocated for this operand, or to
  ;; NIL if no load-TN was allocated.
  (load-tn (gensym) :type symbol)
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  ;;
  ;; An expression that tests whether to do automatic operand loading.
  (load t)
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  ;;
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  ;; In a wired or restricted temporary this is the SC the TN is to be packed
  ;; in.  Null otherwise.
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  (sc nil :type (or symbol null))
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  ;;
  ;; If non-null, we are a temp wired to this offset in SC.
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  (offset nil :type (or unsigned-byte null)))


(defprinter operand-parse
  name
  kind
  (target :test target)
  born
  dies
  (scs :test scs)
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  (load :test load)
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  (sc :test sc)
  (offset :test offset))

); Eval-When (Compile Load Eval)


;;;; Random utilities:

(eval-when (compile load eval)

;;; Find-Operand  --  Internal
;;;
;;;    Find the operand or temporary with the specifed Name in the VOP Parse.
;;; If there is no such operand, signal an error.  Also error if the operand
;;; kind isn't one of the specified Kinds.
;;;
(defun find-operand (name parse &optional
			  (kinds '(:argument :result :temporary)))
  (declare (symbol name) (type vop-parse parse) (list kinds))
  (let ((found (find name (vop-parse-operands parse)
		     :key #'operand-parse-name)))
    (unless found
      (error "~S is not an operand to ~S." name (vop-parse-name parse)))
    (unless (member (operand-parse-kind found) kinds)
      (error "Operand ~S isn't one of these kinds: ~S." name kinds))
    found))


;;; VOP-Parse-Or-Lose  --  Internal
;;;
;;;    Get the VOP-Parse structure for Name or die trying.  For all
;;; meta-compile time uses, the VOP-Parse should be used instead of the
;;; VOP-Info
;;;
(defun vop-parse-or-lose (name)
  (the vop-parse
       (or (gethash name *parsed-vops*)
	   (error "~S is not the name of a defined VOP." name))))


;;; Access-Operands  --  Internal
;;;
;;;    Return a list of let-forms to parse a tn-ref list into a the temps
;;; specified by the operand-parse structures.  More-Operand is the
;;; Operand-Parse describing any more operand, or NIL if none.  Refs is an
;;; expression that evaluates into the first tn-ref.
;;;
(defun access-operands (operands more-operand refs)
  (declare (list operands))
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  (collect ((res))
    (let ((prev refs))
      (dolist (op operands)
	(let ((n-ref (operand-parse-temp op)))
	  (res `(,n-ref ,prev))
	  (setq prev `(tn-ref-across ,n-ref))))

      (when more-operand
	(res `(,(operand-parse-name more-operand) ,prev))))
    (res)))


;;; Ignore-Unreferenced-Temps --  Internal
;;;
;;;    Used with Access-Operands to prevent warnings for TN-Ref temps not used
;;; by some particular function.  It returns the name of the last operand, or
;;; NIL if Operands is NIL.
;;;
(defun ignore-unreferenced-temps (operands)
  (when operands
    (operand-parse-temp (car (last operands)))))


;;; VOP-Spec-Arg  --  Internal
;;;
;;;    Grab an arg out of a VOP spec, checking the type and syntax and stuff.
;;;
(defun vop-spec-arg (spec type &optional (n 1) (last t))
  (let ((len (length spec)))
    (when (<= len n)
      (error "~:R argument missing: ~S." n spec))
    (when (and last (> len (1+ n)))
      (error "Extra junk at end of ~S." spec))
    (let ((thing (elt spec n)))
      (unless (typep thing type)
	(error "~:R argument is not a ~S: ~S." n type spec))
      thing)))


;;;; Time specs:

;;; Parse-Time-Spec  --  Internal
;;;
;;;    Return a time spec describing a time during the evaluation of a VOP,
;;; used to delimit operand and temporary lifetimes.  The representation is a
;;; cons whose CAR is the number of the evaluation phase and the CDR is the
;;; sub-phase.  The sub-phase is 0 in the :Load and :Save phases. 
;;;
(defun parse-time-spec (spec)
  (let ((dspec (if (atom spec) (list spec 0) spec)))
    (unless (and (= (length dspec) 2)
		 (typep (second dspec) 'unsigned-byte))
      (error "Malformed time specifier: ~S." spec))

    (cons (case (first dspec)
	    (:load 0)
	    (:argument 1)
	    (:eval 2)
	    (:result 3)
	    (:save 4)
	    (t
	     (error "Unknown phase in time specifier: ~S." spec)))
	  (second dspec))))


;;; Time-Spec-Order  --  Internal
;;;
;;;    Return true if the time spec X is the same or later time than Y.
;;;
(defun time-spec-order (x y)
  (or (> (car x) (car y))
      (and (= (car x) (car y))
	   (>= (cdr x) (cdr y)))))
 

;;;; Emit function generation:

;;; Compute-Reference-Order  --  Internal
;;;
;;;    Return a list of 2-lists (<Temporary> <More-P>) in reverse reference
;;; order describing how to build the next-ref linkage for Parse.  If More-P is
;;; false, then the Temporary points to a single TN-Ref that should be linked
;;; in.  If More-P is true, then Temporary points to a chain of Tn-Refs linked
;;; together by Tn-Ref-Across that should be linked in reverse order.
;;;
;;;    In implementation, we build a temporary list containing the result
;;; tuples augmented with reference time and whether the reference is a write.
;;; We sort this list using Time-Spec-Order augmented by the subsidiary rule
;;; that when the specs are equal, we do read references first.  This
;;; implements the desired semantics of open intervals for temporary lifetimes.
;;;
(defun compute-reference-order (parse)
  (declare (type vop-parse parse))
  (collect ((refs))
    (dolist (op (vop-parse-operands parse))
      (let ((born (operand-parse-born op))
	    (dies (operand-parse-dies op))
	    (name (operand-parse-name op))
	    (temp (operand-parse-temp op))
	    (temp-temp (operand-parse-temp-temp op)))
	(ecase (operand-parse-kind op)
	  (:argument
	   (refs (list (cons dies nil) temp nil)))
	  (:more-argument
	   (refs (list (cons dies nil) name t)))
	  (:result
	   (refs (list (cons born t) temp nil)))
	  (:more-result
	   (refs (list (cons born t) name t)))
	  (:temporary
	   (refs (list (cons born t) temp nil))
	   (refs (list (cons dies nil) temp-temp nil))))))

    (mapcar #'cdr
	    (sort (refs)
		  #'(lambda (x y)
		      (let ((x-time (car x))
			    (y-time (car y)))
		      (if (time-spec-order x-time y-time)
			  (if (time-spec-order y-time x-time)
			      (or (cdr x) (not (cdr y)))
			      t)
			  nil)))
		  :key #'first))))


;;; Make-Next-Ref-Linkage  --  Internal
;;;
;;;    Use the operand lifetime annotations to set up the next-ref slots in all
;;; the TN-Refs used in the VOP.  We set the Refs in the VOP to point to the
;;; head of this list.  More operands make life a bit interesting, since they
;;; introduce uncertainty as to whether we have seen any operands yet, and also
;;; must be linked together contiguously with the other TN-Refs.
;;;
(defun make-next-ref-linkage (parse n-vop)
  (declare (type vop-parse parse))
  (collect ((forms)
	    (binds))
    (let ((first-seen :no)
	  (prev nil))
      (dolist (x (compute-reference-order parse))
	(let* ((var (first x))
	       (more-p (second x))
	       (n-tail (if more-p (gensym) var)))
	  (ecase first-seen
	    (:no
	     (forms `(setf (vop-refs ,n-vop) ,n-tail)))
	    (:yes
	     (forms `(setf (tn-ref-next-ref ,prev) ,n-tail)))
	    (:maybe
	     (forms `(if ,prev
			 (setf (tn-ref-next-ref ,prev) ,n-tail)
			 (setf (vop-refs ,n-vop) ,n-tail)))))
	  
	  (unless (eq first-seen :yes)
	    (setq first-seen (if more-p :maybe :yes)))
	  
	  (if more-p
	      (let ((n-current (gensym))
		    (n-prev (gensym))
		    (n-head (gensym)))
		(binds `(,n-head (or ,var ,prev)))
		(binds
		 `(,n-tail
		   (do ((,n-current ,var (tn-ref-across ,n-current))
			(,n-prev nil ,n-current))
		       ((null ,n-current) ,n-prev)
		     (setf (tn-ref-next-ref ,n-current) ,n-prev))))
		(setq prev n-head))
	      (setq prev var)))))
    
    `((let* ,(binds)
	,@(forms)))))


;;; Make-Temporary  --  Internal
;;;
;;;    Return a form that creates a TN as specified by Temp.  This requires
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;;; deciding whether the temp is wired or restricted.
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;;;
(defun make-temporary (temp)
  (declare (type operand-parse temp))
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  (let ((sc (operand-parse-sc temp))
	(offset (operand-parse-offset temp)))
    (assert sc)
    (if offset
	`(make-wired-tn nil ,(meta-sc-number-or-lose sc) ,offset)
	`(make-restricted-tn nil ,(meta-sc-number-or-lose sc)))))
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;;; Allocate-Temporaries  --  Internal
;;;
;;;    Allocate VOP temporary TNs, making TN-Refs for their start and end, and
;;; setting up various per-ref information.  N-Vop is the temporary holding the
;;; VOP we are emitting.  We return a list of let* binding forms that create
;;; the TN-Refs, a list of forms that initialize the TN-Refs.
;;;
(defun allocate-temporaries (parse n-vop)
  (declare (type vop-parse parse))
  (collect ((binds)
	    (forms))
    (let ((prev-write nil))
      (dolist (temp (vop-parse-temps parse))
	(let ((n-write (operand-parse-temp temp))
	      (n-read (operand-parse-temp-temp temp))
	      (n-tn (gensym)))
	  (binds `(,n-tn ,(make-temporary temp)))
	  (binds `(,n-write (reference-tn ,n-tn t)))
	  (binds `(,n-read (reference-tn ,n-tn nil)))
	  (if prev-write
	      (forms `(setf (tn-ref-across ,prev-write) ,n-write))
	      (forms `(setf (vop-temps ,n-vop) ,n-write)))
	  (setq prev-write n-write)
	  (forms `(setf (tn-ref-vop ,n-read) ,n-vop))
	  (forms `(setf (tn-ref-vop ,n-write) ,n-vop)))))

    (values (binds) (forms))))


;;; Set-VOP-Pointers  --  Internal
;;;
;;;    Return code to set the TN-Ref-Vop slots in some operands to the value of
;;; N-Vop.  If there is no more operand, set the set the slots individually,
;;; otherwise loop over the whole list N-Refs.
;;;
(defun set-vop-pointers (operands more-operand n-vop n-refs)
  (if more-operand
      `((do ((,n-refs ,n-refs (tn-ref-across ,n-refs)))
	    ((null ,n-refs))
	  (setf (tn-ref-vop ,n-refs) ,n-vop)))
      (mapcar #'(lambda (op)
		  `(setf (tn-ref-vop ,(operand-parse-temp op)) ,n-vop))
	      operands)))


;;; Make-Emit-Function  --  Internal
;;;
;;;    Make the Template Emit-Function for a VOP.
;;;
(defun make-emit-function (parse)
  (declare (type vop-parse parse))
  (let ((n-node (gensym)) (n-block (gensym))
	(n-template (gensym)) (n-args (gensym))
	(n-results (gensym)) (n-info (gensym))
	(n-vop (gensym))
	(info-args (vop-parse-info-args parse)))
    (multiple-value-bind (temp-binds temp-forms)
			 (allocate-temporaries parse n-vop)
      `#'(lambda (,n-node ,n-block ,n-template ,n-args ,n-results
			  ,@(when info-args `(,n-info)))
	   (let ((,n-vop (make-vop ,n-block ,n-node ,n-template
				   ,n-args ,n-results)))

	     ,@(when info-args
		 `((setf (vop-codegen-info ,n-vop) ,n-info)))
	     
	     (let* (,@(access-operands (vop-parse-args parse)
				       (vop-parse-more-args parse)
				       n-args)
		    ,@(access-operands (vop-parse-results parse)
				       (vop-parse-more-results parse)
				       n-results)
		    ,@temp-binds)
	       ,@temp-forms
	       ,@(set-vop-pointers (vop-parse-args parse)
				   (vop-parse-more-args parse)
				   n-vop n-args)
	       ,@(set-vop-pointers (vop-parse-results parse)
				   (vop-parse-more-results parse)
				   n-vop n-results)
	       ,@(make-next-ref-linkage parse n-vop))
	     (values ,n-vop ,n-vop))))))