mdw@git.distorted.org.uk Git - sod/blob - src/codegen-proto.lisp

   1 ;;; -*-lisp-*-
   2 ;;;
   3 ;;; Code generation protocol
   4 ;;;
   5 ;;; (c) 2009 Straylight/Edgeware
   6 ;;;
   7
   8 ;;;----- Licensing notice ---------------------------------------------------
   9 ;;;
  10 ;;; This file is part of the Sensble Object Design, an object system for C.
  11 ;;;
  12 ;;; SOD is free software; you can redistribute it and/or modify
  13 ;;; it under the terms of the GNU General Public License as published by
  14 ;;; the Free Software Foundation; either version 2 of the License, or
  15 ;;; (at your option) any later version.
  16 ;;;
  17 ;;; SOD is distributed in the hope that it will be useful,
  18 ;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  19 ;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20 ;;; GNU General Public License for more details.
  21 ;;;
  22 ;;; You should have received a copy of the GNU General Public License
  23 ;;; along with SOD; if not, write to the Free Software Foundation,
  24 ;;; Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  25
  26 (cl:in-package #:sod)
  27
  28 ;;;--------------------------------------------------------------------------
  29 ;;; Temporary names.
  30
  31 ;; Protocol.
  32
  33 (export 'format-temporary-name)
  34 (defgeneric format-temporary-name (var stream)
  35   (:documentation
  36    "Write the name of a temporary variable VAR to STREAM."))
  37
  38 (export 'var-in-use-p)
  39 (defgeneric var-in-use-p (var)
  40   (:documentation
  41    "Answer whether VAR is currently being used.  See `with-temporary-var'.")
  42   (:method (var)
  43     "Non-temporary variables are always in use."
  44     (declare (ignore var))
  45     t))
  46 (defgeneric (setf var-in-use-p) (value var)
  47   (:documentation
  48    "Record whether VAR is currently being used.  See `with-temporary-var'."))
  49
  50 ;; Root class.
  51
  52 (export 'temporary-name)
  53 (defclass temporary-name ()
  54   ((tag :initarg :tag :reader temp-tag))
  55   (:documentation
  56    "Base class for temporary variable and argument names."))
  57
  58 ;; Important variables.
  59
  60 (defparameter *temporary-index* 0
  61   "Index for temporary name generation.
  62
  63    This is automatically reset to zero before the output functions are
  64    invoked to write a file.  This way, we can ensure that the same output
  65    file is always produced from the same input.")
  66
  67 (define-clear-the-decks reset-codegen-index
  68   (setf *temporary-index* 0))
  69
  70 ;; Important temporary names.
  71
  72 (export '(*sod-ap* *sod-master-ap*))
  73 (defparameter *sod-ap*
  74   (make-instance 'temporary-name :tag "sod__ap"))
  75 (defparameter *sod-master-ap*
  76   (make-instance 'temporary-name :tag "sod__master_ap"))
  77
  78 ;;;--------------------------------------------------------------------------
  79 ;;; Instructions.
  80
  81 ;; Classes.
  82
  83 (export 'inst)
  84 (defclass inst () ()
  85   (:documentation
  86    "A base class for instructions.
  87
  88    An `instruction' is anything which might be useful to string into a code
  89    generator.  Both statements and expressions can be represented by trees of
  90    instructions.  The `definst' macro is a convenient way of defining new
  91    instructions.
  92
  93    The only important protocol for instructions is output, which is achieved
  94    by calling `print-object' with `*print-escape*' nil.
  95
  96    This doesn't really do very much, but it acts as a handy marker for
  97    instruction subclasses."))
  98
  99 (export 'inst-metric)
 100 (defgeneric inst-metric (inst)
 101   (:documentation
 102    "Returns a `metric' describing how complicated INST is.
 103
 104    The default metric of an inst node is simply 1; `inst' subclasses
 105    generated by `definst' (q.v.) have an automatically generated method which
 106    returns one plus the sum of the metrics of the node's children.
 107
 108    This isn't intended to be a particularly rigorous definition.  Its purpose
 109    is to allow code generators to make decisions about inlining or calling
 110    code fairly simply.")
 111   (:method ((inst t))
 112     (declare (ignore inst))
 113     1)
 114   (:method ((inst null))
 115     (declare (ignore inst))
 116     1)
 117   (:method ((inst list))
 118     (reduce #'+ inst :key #'inst-metric)))
 119
 120 ;; Instruction definition.
 121
 122 (export 'definst)
 123 (defmacro definst (code (streamvar &key export) args &body body)
 124   "Define an instruction type and describe how to output it.
 125
 126    An `inst' can represent any structured piece of output syntax: a
 127    statement, expression or declaration, for example.  This macro defines the
 128    following things:
 129
 130      * A class `CODE-inst' to represent the instruction.
 131
 132      * Instance slots named after the ARGS, with matching keyword initargs,
 133        and `inst-ARG' readers.
 134
 135      * A constructor `make-CODE-inst' which accepts the ARGS (in order, not
 136        with keywords) as arguments and returns a fresh instance.
 137
 138      * A print method, which prints a diagnostic dump if `*print-escape*' is
 139        set, or invokes the BODY (with STREAMVAR bound to the output stream)
 140        otherwise.  The BODY is expected to produce target code at this
 141        point.
 142
 143    If EXPORT is non-nil, then export the `CODE-inst' and `make-CODE-inst'
 144    symbols."
 145
 146   (let ((inst-var (gensym "INST"))
 147         (class-name (symbolicate code '-inst))
 148         (constructor-name (symbolicate 'make- code '-inst))
 149         (keys (mapcar (lambda (arg) (intern (symbol-name arg) :keyword))
 150                       args)))
 151     `(progn
 152        (defclass ,class-name (inst)
 153          ,(mapcar (lambda (arg key)
 154                     `(,arg :initarg ,key :reader ,(symbolicate 'inst- arg)))
 155                   args keys))
 156        (defun ,constructor-name (,@args)
 157          (make-instance ',class-name ,@(mappend #'list keys args)))
 158        (defmethod inst-metric ((,inst-var ,class-name))
 159          (with-slots (,@args) ,inst-var
 160            (+ 1 ,@(mapcar (lambda (arg) `(inst-metric ,arg)) args))))
 161        (defmethod print-object ((,inst-var ,class-name) ,streamvar)
 162          (with-slots (,@args) ,inst-var
 163            (if *print-escape*
 164                (print-unreadable-object (,inst-var ,streamvar :type t)
 165                  (format stream "~@<~@{~S ~@_~S~^ ~_~}~:>"
 166                          ,@(mappend #'list keys args)))
 167                (progn ,@body))))
 168        ,@(and export `((export '(,class-name ,constructor-name))))
 169        ',code)))
 170
 171 ;; Important instruction classes.
 172
 173 (definst var (stream :export t) (name type init)
 174   (pprint-c-type type stream name)
 175   (when init
 176     (format stream " = ~A" init))
 177   (write-char #\; stream))
 178 (definst set (stream :export t) (var expr)
 179   (format stream "~@<~A = ~@_~2I~A;~:>" var expr))
 180 (definst update (stream :export t) (var op expr)
 181   (format stream "~@<~A ~A= ~@_~2I~A;~:>" var op expr))
 182 (definst return (stream :export t) (expr)
 183   (format stream "return~@[ (~A)~];" expr))
 184 (definst break (stream :export t) ()
 185   (format stream "break;"))
 186 (definst continue (stream :export t) ()
 187   (format stream "continue;"))
 188 (definst expr (stream :export t) (expr)
 189   (format stream "~A;" expr))
 190 (definst block (stream :export t) (decls body)
 191   (format stream "{~:@_~@<  ~2I~@[~{~A~:@_~}~:@_~]~{~A~^~:@_~}~:>~:@_}"
 192           decls body))
 193 (definst function (stream :export t) (name type body)
 194   (pprint-logical-block (stream nil)
 195     (princ "static " stream)
 196     (pprint-c-type type stream name)
 197     (format stream "~:@_~A~:@_~:@_" body)))
 198
 199 ;; Formatting utilities.
 200
 201 (defun format-compound-statement* (stream child morep thunk)
 202   "Underlying function for `format-compound-statement'."
 203   (cond ((typep child 'block-inst)
 204          (funcall thunk stream)
 205          (write-char #\space stream)
 206          (princ child stream)
 207          (when morep (write-char #\space stream)))
 208         (t
 209          (pprint-logical-block (stream nil)
 210            (funcall thunk stream)
 211            (write-char #\space stream)
 212            (pprint-indent :block 2 stream)
 213            (pprint-newline :linear stream)
 214            (princ child stream)
 215            (pprint-indent :block 0 stream)
 216            (case morep
 217              (:space
 218               (write-char #\space stream)
 219               (pprint-newline :linear stream))
 220              ((t)
 221               (pprint-newline :mandatory stream)))))))
 222
 223 (export 'format-compound-statement)
 224 (defmacro format-compound-statement
 225     ((stream child &optional morep) &body body)
 226   "Format a compound statement to STREAM.
 227
 228    The introductory material is printed by BODY.  The CHILD is formatted
 229    properly according to whether it's a `block-inst'.  If MOREP is true, then
 230    allow for more stuff following the child."
 231   `(format-compound-statement* ,stream ,child ,morep
 232                                (lambda (,stream) ,@body)))
 233
 234 ;;;--------------------------------------------------------------------------
 235 ;;; Code generation.
 236
 237 ;; Accessors.
 238
 239 (export 'codegen-functions)
 240 (defgeneric codegen-functions (codegen)
 241   (:documentation
 242    "Return the list of `function-inst's of completed functions."))
 243
 244 (export 'ensure-var)
 245 (defgeneric ensure-var (codegen name type &optional init)
 246   (:documentation
 247    "Add a variable to CODEGEN's list.
 248
 249    The variable is called NAME (which should be comparable using `equal' and
 250    print to an identifier) and has the given TYPE.  If INIT is present and
 251    non-nil it is an expression `inst' used to provide the variable with an
 252    initial value."))
 253
 254 (export '(emit-inst emit-insts))
 255 (defgeneric emit-inst (codegen inst)
 256   (:documentation
 257    "Add INST to the end of CODEGEN's list of instructions."))
 258 (defgeneric emit-insts (codegen insts)
 259   (:documentation
 260    "Add a list of INSTS to the end of CODEGEN's list of instructions.")
 261   (:method (codegen insts)
 262     (dolist (inst insts) (emit-inst codegen inst))))
 263
 264 (export '(emit-decl emit-decls))
 265 (defgeneric emit-decl (codegen inst)
 266   (:documentation
 267    "Add INST to the end of CODEGEN's list of declarations."))
 268 (defgeneric emit-decls (codegen insts)
 269   (:documentation
 270    "Add a list of INSTS to the end of CODEGEN's list of declarations."))
 271
 272 (export 'codegen-push)
 273 (defgeneric codegen-push (codegen)
 274   (:documentation
 275    "Pushes the current code generation state onto a stack.
 276
 277    The state consists of the accumulated variables and instructions."))
 278
 279 (export 'codegen-pop)
 280 (defgeneric codegen-pop (codegen)
 281   (:documentation
 282    "Pops a saved state off of the CODEGEN's stack.
 283
 284    Returns the newly accumulated variables and instructions as lists, as
 285    separate values."))
 286
 287 (export 'codegen-add-function)
 288 (defgeneric codegen-add-function (codegen function)
 289   (:documentation
 290    "Adds a function to CODEGEN's list.
 291
 292    Actually, we're not picky: FUNCTION can be any kind of object that you're
 293    willing to find in the list returned by `codegen-functions'."))
 294
 295 (export 'temporary-var)
 296 (defgeneric temporary-var (codegen type)
 297   (:documentation
 298    "Return the name of a temporary variable.
 299
 300    The temporary variable will have the given TYPE, and will be marked
 301    in-use.  You should clear the in-use flag explicitly when you've finished
 302    with the variable -- or, better, use `with-temporary-var' to do the
 303    cleanup automatically."))
 304
 305 (export 'codegen-build-function)
 306 (defun codegen-build-function (codegen name type vars insts)
 307   "Build a function and add it to CODEGEN's list.
 308
 309    Returns the function's name."
 310   (codegen-add-function codegen
 311                         (make-function-inst name type
 312                                             (make-block-inst vars insts)))
 313   name)
 314
 315 (export 'codegen-pop-block)
 316 (defgeneric codegen-pop-block (codegen)
 317   (:documentation
 318    "Makes a block (`block-inst') out of the completed code in CODEGEN.")
 319   (:method (codegen)
 320     (multiple-value-bind (vars insts) (codegen-pop codegen)
 321       (make-block-inst vars insts))))
 322
 323 (export 'codegen-pop-function)
 324 (defgeneric codegen-pop-function (codegen name type)
 325   (:documentation
 326    "Makes a function out of the completed code in CODEGEN.
 327
 328    The NAME can be any object you like.  The TYPE should be a function type
 329    object which includes argument names.  The return value is the NAME.")
 330   (:method (codegen name type)
 331     (multiple-value-bind (vars insts) (codegen-pop codegen)
 332       (codegen-build-function codegen name type vars insts))))
 333
 334 (export 'with-temporary-var)
 335 (defmacro with-temporary-var ((codegen var type) &body body)
 336   "Evaluate BODY with VAR bound to a temporary variable name.
 337
 338    During BODY, VAR will be marked in-use; when BODY ends, VAR will be marked
 339    available for re-use."
 340   `(let ((,var (temporary-var ,codegen ,type)))
 341      (unwind-protect
 342           (progn ,@body)
 343        (setf (var-in-use-p ,var) nil))))
 344
 345 ;;;--------------------------------------------------------------------------
 346 ;;; Code generation idioms.
 347
 348 (export 'deliver-expr)
 349 (defun deliver-expr (codegen target expr)
 350   "Emit code to deliver the value of EXPR to the TARGET.
 351
 352    The TARGET may be one of the following.
 353
 354      * `:void', indicating that the value is to be discarded.  The expression
 355        will still be evaluated.
 356
 357      * `:void-return', indicating that the value is to be discarded (as for
 358        `:void') and furthermore a `return' from the current function should
 359        be forced after computing the value.
 360
 361      * `:return', indicating that the value is to be returned from the
 362        current function.
 363
 364      * A variable name, indicating that the value is to be stored in the
 365        variable.
 366
 367    In the cases of `:return', `:void' and `:void-return' targets, it is valid
 368    for EXPR to be nil; this signifies that no computation needs to be
 369    performed.  Variable-name targets require an expression."
 370
 371   (case target
 372     (:return (emit-inst codegen (make-return-inst expr)))
 373     (:void (when expr (emit-inst codegen (make-expr-inst expr))))
 374     (:void-return (when expr (emit-inst codegen (make-expr-inst expr)))
 375                   (emit-inst codegen (make-return-inst nil)))
 376     (t (emit-inst codegen (make-set-inst target expr)))))
 377
 378 (export 'convert-stmts)
 379 (defun convert-stmts (codegen target type func)
 380   "Invoke FUNC to deliver a value to a non-`:return' target.
 381
 382    FUNC is a function which accepts a single argument, a non-`:return'
 383    target, and generates statements which deliver a value (see
 384    `deliver-expr') of the specified TYPE to this target.  In general, the
 385    generated code will have the form
 386
 387      setup instructions...
 388      (deliver-expr CODEGEN TARGET (compute value...))
 389      cleanup instructions...
 390
 391    where the cleanup instructions are essential to the proper working of the
 392    generated program.
 393
 394    The `convert-stmts' function will call FUNC to generate code, and arrange
 395    that its value is correctly delivered to TARGET, regardless of what the
 396    TARGET is -- i.e., it lifts the restriction to non-`:return' targets.  It
 397    does this by inventing a new temporary variable."
 398
 399   (case target
 400     (:return (with-temporary-var (codegen var type)
 401                (funcall func var)
 402                (deliver-expr codegen target var)))
 403     (:void-return (funcall func :void)
 404                   (emit-inst codegen (make-return-inst nil)))
 405     (t (funcall func target))))
 406
 407 ;;;----- That's all, folks --------------------------------------------------