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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
7 ;;;; more information.
8 ;;;;
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.
19 ;;; IR1 boolean function attributes
20 ;;;
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.
28 ;;;
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.
37 call
38 ;; may fail to return during correct execution. Errors are O.K.
39 ;; UNUSED, BEWARE OF BITROT.
40 unwind
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.
44 any
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
49 ;; around.)
50 dx-safe
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.
57 foldable
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.)
65 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.
70 unsafely-flushable
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.
74 important-result
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.
78 movable
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
83 ;; option.
84 predicate
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
88 ;; interpreter stub.)
89 recursive
90 ;; The function does explicit argument type checking, so the
91 ;; declared type should not be asserted when a definition is
92 ;; compiled.
93 explicit-check
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
97 ;; transformation.
98 always-translatable
99 ;; If a function is called with two arguments and the first one is a
100 ;; constant, then the arguments will be swapped.
101 commutative)
104 ;; boolean attributes of this function.
106 ;; TRANSFORM structures describing transforms for this function
108 ;; a function which computes the derived type for a call to this
109 ;; function by examining the arguments. This is null when there is
110 ;; no special method for this function.
112 ;; a function that does various unspecified code transformations by
113 ;; directly hacking the IR. Returns true if further optimizations of
114 ;; the call shouldn't be attempted.
115 ;;
116 ;; KLUDGE: This return convention (non-NIL if you shouldn't do
117 ;; further optimiz'ns) is backwards from the return convention for
118 ;; transforms. -- WHN 19990917
120 ;; a function computing the constant or literal arguments which are
121 ;; destructively modified by the call.
123 ;; If true, a special-case LTN annotation method that is used in
124 ;; place of the standard type/policy template selection. It may use
125 ;; arbitrary code to choose a template, decide to do a full call, or
126 ;; conspire with the IR2-CONVERT method to do almost anything. The
127 ;; COMBINATION node is passed as the argument.
129 ;; If true, the special-case IR2 conversion method for this
130 ;; function. This deals with funny functions, and anything else that
131 ;; can't be handled using the template mechanism. The COMBINATION
132 ;; node and the IR2-BLOCK are passed as arguments.
134 ;; If true, the function can stack-allocate the result. The
135 ;; COMBINATION node is passed as an argument.
137 ;; If true, the function can add flow-sensitive type information
138 ;; about the state of the world after its execution. The COMBINATION
139 ;; node is passed as an argument, along with the current set of
140 ;; active constraints for the block. The function returns a
141 ;; sequence of constraints; a constraint is a triplet of a
142 ;; constraint kind (a symbol, see (defstruct (constraint ...)) in
143 ;; constraint.lisp) and arguments, either LVARs, LAMBDA-VARs, or
144 ;; CTYPEs. If any of these arguments is NIL, the constraint is
145 ;; skipped. This simplifies integration with OK-LVAR-LAMBDA-VAR,
146 ;; which maps LVARs to LAMBDA-VARs. An optional fourth value in
147 ;; each constraint flips the meaning of the constraint if it is
148 ;; non-NIL.
150 ;; If true, the function can add flow-sensitive type information
151 ;; depending on the truthiness of its return value. Returns two
152 ;; values, a LVAR and a CTYPE. The LVAR is of that CTYPE iff the
153 ;; function returns true.
154 ;; It may also return additional third and fourth values. Each is
155 ;; a sequence of constraints (see CONSTRAINT-PROPAGATE), for the
156 ;; consequent and alternative branches, respectively.
158 ;; all the templates that could be used to translate this function
159 ;; into IR2, sorted by increasing cost.
161 ;; If non-null, then this function is a unary type predicate for
162 ;; this type.
164 ;; If non-null, the index of the argument which becomes the result
165 ;; of the function.
178 \f
179 ;;;; interfaces to defining macros
181 ;;; an IR1 transform
183 ;; the function type which enables this transform.
184 ;;
185 ;; (Note that declaring this :TYPE FUN-TYPE probably wouldn't
186 ;; work because some function types, like (SPECIFIER-TYPE 'FUNCTION0
187 ;; itself, are represented as BUILT-IN-TYPE, and at least as of
188 ;; sbcl-0.pre7.54 or so, that's inconsistent with being a
189 ;; FUN-TYPE.)
191 ;; the transformation function. Takes the COMBINATION node and
192 ;; returns a lambda expression, or throws out.
194 ;; string used in efficiency notes
196 ;; T if we should emit a failure note even if SPEED=INHIBIT-WARNINGS.
201 ;;; Grab the FUN-INFO and enter the function, replacing any old
202 ;;; one with the same type and note.
205 *)
206 %deftransform))
225 name))
227 ;;; Make a FUN-INFO structure with the specified type, attributes
228 ;;; and optimizers.
235 *)
236 %defknown))
238 &key derive-type optimizer destroyed-constant-args result-arg
239 overwrite-fndb-silently)
242 :derive-type derive-type
243 :optimizer optimizer
244 :destroyed-constant-args destroyed-constant-args
250 ;; This is handled as an error because it's generally a bad
251 ;; thing to blow away all the old optimization stuff. It's
252 ;; also a potential source of sneaky bugs:
253 ;; DEFKNOWN FOO
254 ;; DEFTRANSFORM FOO
255 ;; DEFKNOWN FOO ; possibly hidden inside some macroexpansion
256 ;; ; Now the DEFTRANSFORM doesn't exist in the target Lisp.
257 ;; However, it's continuable because it might be useful to do
258 ;; it when testing new optimization stuff interactively.
260 "~@<overwriting old FUN-INFO ~2I~_~S ~I~_for ~S~:>"
261 old-fun-info name))))
266 names)
268 ;;; Return the FUN-INFO for NAME or die trying. Since this is
269 ;;; used by callers who want to modify the info, and the info may be
270 ;;; shared, we copy it. We don't have to copy the lists, since each
271 ;;; function that has generators or transforms has already been
272 ;;; through here.
273 ;;;
274 ;;; Note that this operation is somewhat garbage-producing in the current
275 ;;; globaldb implementation. Setting a piece of INFO for a name makes
276 ;;; a shallow copy of the name's info-vector. FUN-INFO-OR-LOSE sounds
277 ;;; like a data reader, and you might be disinclined to think that it
278 ;;; copies at all, but:
279 ;;; (TIME (LOOP REPEAT 1000 COUNT (FUN-INFO-OR-LOSE '*)))
280 ;;; 294,160 bytes consed
281 ;;; whereas just copying the info per se is not half as bad:
282 ;;; (LET ((X (INFO :FUNCTION :INFO '*)))
283 ;;; (TIME (LOOP REPEAT 1000 COUNT (COPY-FUN-INFO X))))
284 ;;; 130,992 bytes consed
285 ;;;
291 \f
292 ;;;; generic type inference methods
294 ;;; Derive the type to be the type of the xxx'th arg. This can normally
295 ;;; only be done when the result value is that argument.
305 ;;; Derive the result type according to the float contagion rules, but
306 ;;; always return a float. This is used for irrational functions that
307 ;;; preserve realness of their arguments.
314 ;;; Return a closure usable as a derive-type method for accessing the
315 ;;; N'th argument. If arg is a list, result is a list. If arg is a
316 ;;; vector, result is a vector with the same element type.
328 ltype))))))))
330 ;;; Derive the type to be the type specifier which is the Nth arg.
338 ;;; Derive the type to be the type specifier which is the Nth arg,
339 ;;; with the additional restriptions noted in the CLHS for STRING and
340 ;;; SIMPLE-STRING, defined to specialize on CHARACTER, and for VECTOR
341 ;;; (under the page for MAKE-SEQUENCE).
352 lspecifier
358 lspecifier
367 ;; I don't think I'm allowed to modify what I get
368 ;; back from SPECIFIER-TYPE; it is, after all,
369 ;; cached. Better copy it, then.
375 real-ctype)
376 ctype)))))))))
383 ;;; FIXME: bad name (first because it uses 1-based indexing; second
384 ;;; because it doesn't get the nth constant arguments)
397 ;;; FIXME: a number of the sequence functions not only do not destroy
398 ;;; their argument if it is empty, but also leave it alone if :start
399 ;;; and :end bound a null sequence, or if :count is 0. This test is a
400 ;;; bit complicated to implement, verging on the impossible, but for
401 ;;; extra points (fill #\1 "abc" :start 0 :end 0) should not cause a
402 ;;; warning.
430 null-type))
431 ;; (READ-elt stream nil <x>) returns (OR (EQL <x>) elt-type)
433 element-type)
434 ;; If eof-error is unsupplied, or was but couldn't be nil
435 element-type)))
438 unexceptional-type))))