1 ;;;; This file contains stuff for maintaining a database of special
2 ;;;; information about functions known to the compiler. This includes
3 ;;;; semantic information such as side effects and type inference
4 ;;;; functions as well as transforms and IR2 translators.
6 ;;;; This software is part of the SBCL system. See the README file for
9 ;;;; This software is derived from the CMU CL system, which was
10 ;;;; written at Carnegie Mellon University and released into the
11 ;;;; public domain. The software is in the public domain and is
12 ;;;; provided with absolutely no warranty. See the COPYING and CREDITS
13 ;;;; files for more information.
17 (/show0 "knownfun.lisp 17")
19 ;;; IR1 boolean function attributes
21 ;;; There are a number of boolean attributes of known functions which
22 ;;; we like to have in IR1. This information is mostly side effect
23 ;;; information of a sort, but it is different from the kind of
24 ;;; information we want in IR2. We aren't interested in a fine
25 ;;; breakdown of side effects, since we do very little code motion on
26 ;;; IR1. We are interested in some deeper semantic properties such as
27 ;;; whether it is safe to pass stack closures to.
29 ;;; FIXME: This whole notion of "bad" explicit attributes is bad for
30 ;;; maintenance. How confident are we that we have no defknowns for functions
31 ;;; with functional arguments that are missing the CALL attribute? Much better
32 ;;; to have NO-CALLS, as it is much less likely to break accidentally.
33 (!def-boolean-attribute ir1
34 ;; may call functions that are passed as arguments. In order to
35 ;; determine what other effects are present, we must find the
36 ;; effects of all arguments that may be functions.
38 ;; may fail to return during correct execution. Errors are O.K.
39 ;; UNUSED, BEWARE OF BITROT.
41 ;; the (default) worst case. Includes all the other bad things, plus
42 ;; any other possible bad thing. If this is present, the above bad
43 ;; attributes will be explicitly present as well.
45 ;; all arguments are safe for dynamic extent.
46 ;; (We used to have an UNSAFE attribute, which was basically the inverse
47 ;; of this, but it was unused and bitrotted, so when we started making
48 ;; use of the information we flipped the name and meaning the safe way
51 ;; may be constant-folded. The function has no side effects, but may
52 ;; be affected by side effects on the arguments. e.g. SVREF, MAPC.
53 ;; Functions that side-effect their arguments are not considered to
54 ;; be foldable. Although it would be "legal" to constant fold them
55 ;; (since it "is an error" to modify a constant), we choose not to
56 ;; mark these functions as foldable in this database.
58 ;; may be eliminated if value is unused. The function has no side
59 ;; effects except possibly cons. If a function might signal errors,
60 ;; then it is not flushable even if it is movable, foldable or
61 ;; unsafely-flushable. Implies UNSAFELY-FLUSHABLE. (In safe code
62 ;; type checking of arguments is always performed by the caller, so
63 ;; a function which SHOULD signal an error if arguments are not of
64 ;; declared types may be FLUSHABLE.)
66 ;; unsafe call may be eliminated if value is unused. The function
67 ;; has no side effects except possibly cons and signalling an error
68 ;; in the safe code. If a function MUST signal errors, then it is
69 ;; not unsafely-flushable even if it is movable or foldable.
71 ;; return value is important, and ignoring it is probably a mistake.
72 ;; Unlike the other attributes, this is used only for style
73 ;; warnings and has no effect on optimization.
75 ;; may be moved with impunity. Has no side effects except possibly
76 ;; consing, and is affected only by its arguments.
77 ;; UNUSED, BEWARE OF BITROT.
79 ;; The function is a true predicate likely to be open-coded. Convert
80 ;; any non-conditional uses into (IF <pred> T NIL). Not usually
81 ;; specified to DEFKNOWN, since this is implementation dependent,
82 ;; and is usually automatically set by the DEFINE-VOP :CONDITIONAL
85 ;; Inhibit any warning for compiling a recursive definition.
86 ;; (Normally the compiler warns when compiling a recursive
87 ;; definition for a known function, since it might be a botched
90 ;; The function does explicit argument type checking, so the
91 ;; declared type should not be asserted when a definition is
94 ;; The function should always be translated by a VOP (i.e. it should
95 ;; should never be converted into a full call). This is used strictly
96 ;; as a consistency checking mechanism inside the compiler during IR2
100 (defstruct (fun-info #-sb-xc-host (:pure t))
101 ;; boolean attributes of this function.
102 (attributes (missing-arg) :type attributes)
103 ;; TRANSFORM structures describing transforms for this function
104 (transforms () :type list)
105 ;; a function which computes the derived type for a call to this
106 ;; function by examining the arguments. This is null when there is
107 ;; no special method for this function.
108 (derive-type nil :type (or function null))
109 ;; a function that does various unspecified code transformations by
110 ;; directly hacking the IR. Returns true if further optimizations of
111 ;; the call shouldn't be attempted.
113 ;; KLUDGE: This return convention (non-NIL if you shouldn't do
114 ;; further optimiz'ns) is backwards from the return convention for
115 ;; transforms. -- WHN 19990917
116 (optimizer nil :type (or function null))
117 ;; a function computing the constant or literal arguments which are
118 ;; destructively modified by the call.
119 (destroyed-constant-args nil :type (or function null))
120 ;; If true, a special-case LTN annotation method that is used in
121 ;; place of the standard type/policy template selection. It may use
122 ;; arbitrary code to choose a template, decide to do a full call, or
123 ;; conspire with the IR2-CONVERT method to do almost anything. The
124 ;; COMBINATION node is passed as the argument.
125 (ltn-annotate nil :type (or function null))
126 ;; If true, the special-case IR2 conversion method for this
127 ;; function. This deals with funny functions, and anything else that
128 ;; can't be handled using the template mechanism. The COMBINATION
129 ;; node and the IR2-BLOCK are passed as arguments.
130 (ir2-convert nil :type (or function null))
131 ;; If true, the function can stack-allocate the result. The
132 ;; COMBINATION node is passed as an argument.
133 (stack-allocate-result nil :type (or function null))
134 ;; all the templates that could be used to translate this function
135 ;; into IR2, sorted by increasing cost.
136 (templates nil :type list)
137 ;; If non-null, then this function is a unary type predicate for
139 (predicate-type nil :type (or ctype null))
140 ;; If non-null, the index of the argument which becomes the result
142 (result-arg nil :type (or index null)))
144 (defprinter (fun-info)
145 (attributes :test (not (zerop attributes))
146 :prin1 (decode-ir1-attributes attributes))
147 (transforms :test transforms)
148 (derive-type :test derive-type)
149 (optimizer :test optimizer)
150 (ltn-annotate :test ltn-annotate)
151 (ir2-convert :test ir2-convert)
152 (templates :test templates)
153 (predicate-type :test predicate-type))
155 ;;;; interfaces to defining macros
158 (defstruct (transform (:copier nil))
159 ;; the function type which enables this transform.
161 ;; (Note that declaring this :TYPE FUN-TYPE probably wouldn't
162 ;; work because some function types, like (SPECIFIER-TYPE 'FUNCTION0
163 ;; itself, are represented as BUILT-IN-TYPE, and at least as of
164 ;; sbcl-0.pre7.54 or so, that's inconsistent with being a
166 (type (missing-arg) :type ctype)
167 ;; the transformation function. Takes the COMBINATION node and
168 ;; returns a lambda expression, or throws out.
169 (function (missing-arg) :type function)
170 ;; string used in efficiency notes
171 (note (missing-arg) :type string)
172 ;; T if we should emit a failure note even if SPEED=INHIBIT-WARNINGS.
173 (important nil :type (member t nil)))
175 (defprinter (transform) type note important)
177 ;;; Grab the FUN-INFO and enter the function, replacing any old
178 ;;; one with the same type and note.
179 (declaim (ftype (function (t list function &optional (or string null)
183 (defun %deftransform (name type fun &optional note important)
184 (let* ((ctype (specifier-type type))
185 (note (or note "optimize"))
186 (info (fun-info-or-lose name))
187 (old (find-if (lambda (x)
188 (and (type= (transform-type x) ctype)
189 (string-equal (transform-note x) note)
190 (eq (transform-important x) important)))
191 (fun-info-transforms info))))
193 (style-warn 'sb!kernel:redefinition-with-deftransform
195 (setf (transform-function old) fun
196 (transform-note old) note))
198 (push (make-transform :type ctype :function fun :note note
199 :important important)
200 (fun-info-transforms info))))
203 ;;; Make a FUN-INFO structure with the specified type, attributes
205 (declaim (ftype (function (list list attributes &key
206 (:derive-type (or function null))
207 (:optimizer (or function null))
208 (:destroyed-constant-args (or function null))
209 (:result-arg (or index null)))
212 (defun %defknown (names type attributes &key derive-type optimizer destroyed-constant-args result-arg)
213 (let ((ctype (specifier-type type))
214 (info (make-fun-info :attributes attributes
215 :derive-type derive-type
217 :destroyed-constant-args destroyed-constant-args
218 :result-arg result-arg)))
220 (let ((old-fun-info (info :function :info name)))
222 ;; This is handled as an error because it's generally a bad
223 ;; thing to blow away all the old optimization stuff. It's
224 ;; also a potential source of sneaky bugs:
227 ;; DEFKNOWN FOO ; possibly hidden inside some macroexpansion
228 ;; ; Now the DEFTRANSFORM doesn't exist in the target Lisp.
229 ;; However, it's continuable because it might be useful to do
230 ;; it when testing new optimization stuff interactively.
231 (cerror "Go ahead, overwrite it."
232 "~@<overwriting old FUN-INFO ~2I~_~S ~I~_for ~S~:>"
234 (setf (info :function :type name) ctype)
235 (setf (info :function :where-from name) :declared)
236 (setf (info :function :kind name) :function)
237 (setf (info :function :info name) info)))
240 ;;; Return the FUN-INFO for NAME or die trying. Since this is
241 ;;; used by callers who want to modify the info, and the info may be
242 ;;; shared, we copy it. We don't have to copy the lists, since each
243 ;;; function that has generators or transforms has already been
245 (declaim (ftype (sfunction (t) fun-info) fun-info-or-lose))
246 (defun fun-info-or-lose (name)
247 (let (;; FIXME: Do we need this rebinding here? It's a literal
248 ;; translation of the old CMU CL rebinding to
249 ;; (OR *BACKEND-INFO-ENVIRONMENT* *INFO-ENVIRONMENT*),
250 ;; and it's not obvious whether the rebinding to itself is
251 ;; needed that SBCL doesn't need *BACKEND-INFO-ENVIRONMENT*.
252 (*info-environment* *info-environment*))
253 (let ((old (info :function :info name)))
254 (unless old (error "~S is not a known function." name))
255 (setf (info :function :info name) (copy-fun-info old)))))
257 ;;;; generic type inference methods
259 ;;; Derive the type to be the type of the xxx'th arg. This can normally
260 ;;; only be done when the result value is that argument.
261 (defun result-type-first-arg (call)
262 (declare (type combination call))
263 (let ((lvar (first (combination-args call))))
264 (when lvar (lvar-type lvar))))
265 (defun result-type-last-arg (call)
266 (declare (type combination call))
267 (let ((lvar (car (last (combination-args call)))))
268 (when lvar (lvar-type lvar))))
270 ;;; Derive the result type according to the float contagion rules, but
271 ;;; always return a float. This is used for irrational functions that
272 ;;; preserve realness of their arguments.
273 (defun result-type-float-contagion (call)
274 (declare (type combination call))
275 (reduce #'numeric-contagion (combination-args call)
277 :initial-value (specifier-type 'single-float)))
279 ;;; Return a closure usable as a derive-type method for accessing the
280 ;;; N'th argument. If arg is a list, result is a list. If arg is a
281 ;;; vector, result is a vector with the same element type.
282 (defun sequence-result-nth-arg (n)
284 (declare (type combination call))
285 (let ((lvar (nth (1- n) (combination-args call))))
287 (let ((type (lvar-type lvar)))
288 (if (array-type-p type)
290 `(vector ,(type-specifier (array-type-element-type type))))
291 (let ((ltype (specifier-type 'list)))
292 (when (csubtypep type ltype)
295 ;;; Derive the type to be the type specifier which is the Nth arg.
296 (defun result-type-specifier-nth-arg (n)
298 (declare (type combination call))
299 (let ((lvar (nth (1- n) (combination-args call))))
300 (when (and lvar (constant-lvar-p lvar))
301 (careful-specifier-type (lvar-value lvar))))))
303 ;;; Derive the type to be the type specifier which is the Nth arg,
304 ;;; with the additional restriptions noted in the CLHS for STRING and
305 ;;; SIMPLE-STRING, defined to specialize on CHARACTER, and for VECTOR
306 ;;; (under the page for MAKE-SEQUENCE).
307 (defun creation-result-type-specifier-nth-arg (n)
309 (declare (type combination call))
310 (let ((lvar (nth (1- n) (combination-args call))))
311 (when (and lvar (constant-lvar-p lvar))
312 (let* ((specifier (lvar-value lvar))
313 (lspecifier (if (atom specifier) (list specifier) specifier)))
315 ((eq (car lspecifier) 'string)
316 (destructuring-bind (string &rest size)
318 (declare (ignore string))
319 (careful-specifier-type
320 `(vector character ,@(when size size)))))
321 ((eq (car lspecifier) 'simple-string)
322 (destructuring-bind (simple-string &rest size)
324 (declare (ignore simple-string))
325 (careful-specifier-type
326 `(simple-array character ,@(if size (list size) '((*)))))))
328 (let ((ctype (careful-specifier-type specifier)))
329 (if (and (array-type-p ctype)
330 (eq (array-type-specialized-element-type ctype)
332 ;; I don't think I'm allowed to modify what I get
333 ;; back from SPECIFIER-TYPE; it is, after all,
334 ;; cached. Better copy it, then.
335 (let ((real-ctype (copy-structure ctype)))
336 (setf (array-type-element-type real-ctype)
338 (array-type-specialized-element-type real-ctype)
343 (defun remove-non-constants-and-nils (fun)
345 (remove-if-not #'lvar-value
346 (remove-if-not #'constant-lvar-p (funcall fun list)))))
348 ;;; FIXME: bad name (first because it uses 1-based indexing; second
349 ;;; because it doesn't get the nth constant arguments)
350 (defun nth-constant-args (&rest indices)
354 (list list (cdr list))
356 ((null indices) (nreverse result))
357 (when (= i (car indices))
358 (when (constant-lvar-p (car list))
359 (push (car list) result))
360 (setf indices (cdr indices)))))))
362 ;;; FIXME: a number of the sequence functions not only do not destroy
363 ;;; their argument if it is empty, but also leave it alone if :start
364 ;;; and :end bound a null sequence, or if :count is 0. This test is a
365 ;;; bit complicated to implement, verging on the impossible, but for
366 ;;; extra points (fill #\1 "abc" :start 0 :end 0) should not cause a
368 (defun nth-constant-nonempty-sequence-args (&rest indices)
372 (list list (cdr list))
374 ((null indices) (nreverse result))
375 (when (= i (car indices))
376 (when (constant-lvar-p (car list))
377 (let ((value (lvar-value (car list))))
378 (unless (or (typep value 'null)
379 (typep value '(vector * 0)))
380 (push (car list) result))))
381 (setf indices (cdr indices)))))))
383 (/show0 "knownfun.lisp end of file")