| blob | eece0c766b2de71c18f08eaf28585a7e3e7c6abc |
1 ;;;; This file implements the IR1 optimization phase of the compiler.
2 ;;;; IR1 optimization is a grab-bag of optimizations that don't make
3 ;;;; major changes to the block-level control flow and don't use flow
4 ;;;; analysis. These optimizations can mostly be classified as
5 ;;;; "meta-evaluation", but there is a sizable top-down component as
6 ;;;; well.
8 ;;;; This software is part of the SBCL system. See the README file for
9 ;;;; more information.
10 ;;;;
11 ;;;; This software is derived from the CMU CL system, which was
12 ;;;; written at Carnegie Mellon University and released into the
13 ;;;; public domain. The software is in the public domain and is
14 ;;;; provided with absolutely no warranty. See the COPYING and CREDITS
15 ;;;; files for more information.
18 \f
19 ;;;; interface for obtaining results of constant folding
21 ;;; Return true for an LVAR whose sole use is a reference to a
22 ;;; constant leaf.
28 ;; check for EQL types (but not singleton numeric types)
32 ;;; Return the constant value for an LVAR whose only use is a constant
33 ;;; node.
38 leaf)
45 value))))
46 \f
47 ;;;; interface for obtaining results of type inference
49 ;;; Our best guess for the type of this lvar's value. Note that this
50 ;;; may be VALUES or FUNCTION type, which cannot be passed as an
51 ;;; argument to the normal type operations. See LVAR-TYPE.
52 ;;;
53 ;;; The result value is cached in the LVAR-%DERIVED-TYPE slot. If the
54 ;;; slot is true, just return that value, otherwise recompute and
55 ;;; stash the value there.
65 res))
68 res)))
81 ;;; Return the derived type for LVAR's first value. This is guaranteed
82 ;;; not to be a VALUES or FUNCTION type.
87 ;;; LVAR-CONSERVATIVE-TYPE
88 ;;;
89 ;;; Certain types refer to the contents of an object, which can
90 ;;; change without type derivation noticing: CONS types and ARRAY
91 ;;; types suffer from this:
92 ;;;
93 ;;; (let ((x (the (cons fixnum fixnum) (cons a b))))
94 ;;; (setf (car x) c)
95 ;;; (+ (car x) (cdr x)))
96 ;;;
97 ;;; Python doesn't realize that the SETF CAR can change the type of X -- so we
98 ;;; cannot use LVAR-TYPE which gets the derived results. Worse, still, instead
99 ;;; of (SETF CAR) we might have a call to a user-defined function FOO which
100 ;;; does the same -- so there is no way to use the derived information in
101 ;;; general.
102 ;;;
103 ;;; So, the conservative option is to use the derived type if the leaf has
104 ;;; only a single ref -- in which case there cannot be a prior call that
105 ;;; mutates it. Otherwise we use the declared type or punt to the most general
106 ;;; type we know to be correct for sure.
110 ;; Recompute using NODE-CONSERVATIVE-TYPE instead of derived type if
111 ;; necessary -- picking off some easy cases up front.
113 ;; Can't use CSUBTYPEP!
116 derived-type)
120 derived-type)
126 derived-type)
130 derived-type))))
143 derived-values-type))
144 derived-values-type)))
150 type)
156 ;; ADJUST-ARRAY may change dimensions, but rank stays same.
157 :dimensions
160 old
162 ;; Complexity cannot change.
164 ;; Element type cannot change.
167 ;; Simple arrays cannot change at all.
168 type))
170 ;; Conservative union type is an union of conservative types.
175 ;; Catch-all.
176 ;;
177 ;; If the type contains some CONS types, the conservative type contains all
178 ;; of them.
181 ;; Similarly for non-simple arrays -- it should be possible to preserve
182 ;; more information here, but really...
186 type)))
190 ;; Excluding T is necessary, because we do want type derivation to
191 ;; be able to narrow it down in case someone (most like a macro-expansion...)
192 ;; actually declares something as having type T.
193 nil)
195 ;; Covered by the next case as well, but this is a quick test.
196 t)
198 t)))
200 ;;; If LVAR is an argument of a function, return a type which the
201 ;;; function checks LVAR for.
210 ;; TODO: MV-COMBINATION
218 ;; FUN-TYPE might be (AND FUNCTION (SATISFIES ...)).
231 dest)))))
237 \f
238 ;;;; interface routines used by optimizers
248 ;;; This function is called by optimizers to indicate that something
249 ;;; interesting has happened to the value of LVAR. Optimizers must
250 ;;; make sure that they don't call for reoptimization when nothing has
251 ;;; happened, since optimization will fail to terminate.
252 ;;;
253 ;;; We clear any cached type for the lvar and set the reoptimize flags
254 ;;; on everything in sight.
264 ;; PREV may be missing.
283 ;;; Annotate NODE to indicate that its result has been proven to be
284 ;;; TYPEP to RTYPE. After IR1 conversion has happened, this is the
285 ;;; only correct way to supply information discovered about a node's
286 ;;; type. If you screw with the NODE-DERIVED-TYPE directly, then
287 ;;; information may be lost and reoptimization may not happen.
288 ;;;
289 ;;; What we do is intersect RTYPE with NODE's DERIVED-TYPE. If the
290 ;;; intersection is different from the old type, then we do a
291 ;;; REOPTIMIZE-LVAR on the NODE-LVAR.
297 initial-type)))
308 "New inferred type ~S conflicts with old type:~
309 ~% ~S~%*** possible internal error? Please report this."
312 ;; If the new type consists of only one object, replace the
313 ;; node with a constant reference.
324 ;;; This is similar to DERIVE-NODE-TYPE, but asserts that it is an
325 ;;; error for LVAR's value not to be TYPEP to TYPE. We implement it
326 ;;; splitting off DEST a new CAST node; old LVAR will deliver values
327 ;;; to CAST. If we improve the assertion, we set TYPE-CHECK and
328 ;;; TYPE-ASSERTED to guarantee that the new assertion will be checked.
337 t))))
339 \f
340 ;;;; IR1-OPTIMIZE
342 ;;; Do one forward pass over COMPONENT, deleting unreachable blocks
343 ;;; and doing IR1 optimizations. We can ignore all blocks that don't
344 ;;; have the REOPTIMIZE flag set. If COMPONENT-REOPTIMIZE is true when
345 ;;; we are done, then another iteration would be beneficial.
351 for last-block = block
354 ;; We delete blocks when there is either no predecessor or the
355 ;; block is in a lambda that has been deleted. These blocks
356 ;; would eventually be deleted by DFO recomputation, but doing
357 ;; it here immediately makes the effect available to IR1
358 ;; optimization.
364 ;; Preserve the BLOCK-SUCC invariant that almost every block has
365 ;; one successor (and a block with DELETE-P set is an acceptable
366 ;; exception).
401 ;;; Loop over the nodes in BLOCK, acting on (and clearing) REOPTIMIZE
402 ;;; flags.
403 ;;;
404 ;;; Note that although they are cleared here, REOPTIMIZE flags might
405 ;;; still be set upon return from this function, meaning that further
406 ;;; optimization is wanted (as a consequence of optimizations we did).
409 ;; We clear the node and block REOPTIMIZE flags before doing the
410 ;; optimization, not after. This ensures that the node or block will
411 ;; be reoptimized if necessary.
415 ;; As above, we clear the node REOPTIMIZE flag before optimizing.
420 ;; With a COMBINATION, we call PROPAGATE-FUN-CHANGE whenever
421 ;; the function changes, and call IR1-OPTIMIZE-COMBINATION if
422 ;; any argument changes.
427 ;; KLUDGE: We leave the NODE-OPTIMIZE flag set going into
428 ;; IR1-OPTIMIZE-RETURN, since IR1-OPTIMIZE-RETURN wants to
429 ;; clear the flag itself. -- WHN 2002-02-02, quoting original
430 ;; CMU CL comments
436 ;; With an EXIT, we derive the node's type from the VALUE's
437 ;; type.
442 ;; PROPAGATE-FROM-SETS can do a better job if NODE-REOPTIMIZE
443 ;; is accurate till the node actually has been reoptimized.
451 ;;; Try to join with a successor block. If we succeed, we return true,
452 ;;; otherwise false.
459 ;; the successor has more than one predecessor;
461 ;; the successor is the current block (infinite loop);
463 ;; the next block has a different cleanup, and thus
464 ;; we may want to insert cleanup code between the
465 ;; two blocks at some point;
468 ;; the next block has a different home lambda, and
469 ;; thus the control transfer is a non-local exit.
472 ;; Stack analysis phase wants ENTRY to start a block...
478 ;; ... and a DX-allocator to end a block.
480 ;; FIXME: This is a partial workaround for bug 303.
482 nil)
485 t)))))
487 ;;; Join together two blocks. The code in BLOCK2 is moved into BLOCK1
488 ;;; and BLOCK2 is deleted from the DFO. We combine the optimize flags
489 ;;; for the two blocks so that any indicated optimization gets done.
522 ;;; Delete any nodes in BLOCK whose value is unused and which have no
523 ;;; side effects. We can delete sets of lexical variables when the set
524 ;;; variable has no references.
570 victim)
571 \f
572 ;;;; local call return type propagation
574 ;;; This function is called on RETURN nodes that have their REOPTIMIZE
575 ;;; flag set. It iterates over the uses of the RESULT, looking for
576 ;;; interesting stuff to update the TAIL-SET. If a use isn't a local
577 ;;; call, then we union its type together with the types of other such
578 ;;; uses. We assign to the RETURN-RESULT-TYPE the intersection of this
579 ;;; type with the RESULT's asserted type. We can make this
580 ;;; intersection now (potentially before type checking) because this
581 ;;; assertion on the result will eventually be checked (if
582 ;;; appropriate.)
583 ;;;
584 ;;; We call MAYBE-CONVERT-TAIL-LOCAL-CALL on each local non-MV
585 ;;; combination, which may change the successor of the call to be the
586 ;;; called function, and if so, checks if the call can become an
587 ;;; assignment. If we convert to an assignment, we abort, since the
588 ;;; RETURN has been deleted.
607 ;; (values-type-intersection
608 ;; (continuation-asserted-type result) ; FIXME -- APD, 2002-01-26
610 ;; )
611 ))
613 nil)
615 ;;; Do stuff to realize that something has changed about the value
616 ;;; delivered to a return node. Since we consider the return values of
617 ;;; all functions in the tail set to be equivalent, this amounts to
618 ;;; bringing the entire tail set up to date. We iterate over the
619 ;;; returns for all the functions in the tail set, reanalyzing them
620 ;;; all (not treating NODE specially.)
621 ;;;
622 ;;; When we are done, we check whether the new type is different from
623 ;;; the old TAIL-SET-TYPE. If so, we set the type and also reoptimize
624 ;;; all the lvars for references to functions in the tail set. This
625 ;;; will cause IR1-OPTIMIZE-COMBINATION to derive the new type as the
626 ;;; results of the calls.
630 :restart
650 \f
651 ;;;; IF optimization
653 ;;; Utility: return T if both argument cblocks are equivalent. For now,
654 ;;; detect only blocks that read the same leaf into the same lvar, and
655 ;;; continue to the same block.
668 ;;; Check whether the predicate is known to be true or false,
669 ;;; deleting the IF node in favor of the appropriate branch when this
670 ;;; is the case.
671 ;;; Similarly, when both branches are equivalent, branch directly to either
672 ;;; of them.
673 ;;; Also, if the test has multiple uses, replicate the node when possible...
674 ;;; in fact, splice in direct jumps to the right branch if possible.
686 alternative)
688 consequent)
691 alternative))))
699 ;; When we know that we only have a single successor, kill the victim
700 ;; ... unless the victim and the remaining successor are the same.
709 ;; When if/if conversion would leave (if ... (if nil ...)) or
710 ;; (if ... (if not-nil ...)), splice the correct successor right
711 ;; in.
730 ;; only one use left. Just kill the now-useless
731 ;; branch to avoid spurious code deletion notes.
734 node test block
740 ;; Finally, duplicate EQ-nil tests
747 ;; leave the last use as is, instead of replacing
748 ;; the (singly-referenced) CIF node with a duplicate.
751 ;;; Create a new copy of an IF node that tests the value of the node
752 ;;; USE. The test must have >1 use, and must be immediately used by
753 ;;; USE. NODE must be the only node in its block (implying that
754 ;;; block-start = if-test).
755 ;;;
756 ;;; This optimization has an effect semantically similar to the
757 ;;; source-to-source transformation:
758 ;;; (IF (IF A B C) D E) ==>
759 ;;; (IF A (IF B D E) (IF C D E))
760 ;;;
761 ;;; We clobber the NODE-SOURCE-PATH of both the original and the new
762 ;;; node so that dead code deletion notes will definitely not consider
763 ;;; either node to be part of the original source. One node might
764 ;;; become unreachable, resulting in a spurious note.
776 :consequent cblock
798 \f
799 ;;;; exit IR1 optimization
801 ;;; This function attempts to delete an exit node, returning true if
802 ;;; it deletes the block as a consequence:
803 ;;; -- If the exit is degenerate (has no ENTRY), then we don't do
804 ;;; anything, since there is nothing to be done.
805 ;;; -- If the exit node and its ENTRY have the same home lambda then
806 ;;; we know the exit is local, and can delete the exit. We change
807 ;;; uses of the Exit-Value to be uses of the original lvar,
808 ;;; then unlink the node. If the exit is to a TR context, then we
809 ;;; must do MERGE-TAIL-SETS on any local calls which delivered
810 ;;; their value to this exit.
811 ;;; -- If there is no value (as in a GO), then we skip the value
812 ;;; semantics.
813 ;;;
814 ;;; This function is also called by environment analysis, since it
815 ;;; wants all exits to be optimized even if normal optimization was
816 ;;; omitted.
828 \f
829 ;;;; combination IR1 optimization
831 ;;; Report as we try each transform?
832 #!+sb-show
840 "The return value of ~A should not be discarded."
843 ;;; Do IR1 optimizations on a COMBINATION node.
853 (:local
858 (:error
862 (:full
885 ;; Check against the DEFINED-TYPE unless TYPE is already good.
895 (:known
903 ;; If somebody is really sure that they want to modify
904 ;; constants, let them.
917 ;; KLUDGE: The next test could be made more sensitive,
918 ;; only suppressing constant-folding of functions with
919 ;; CALL attributes when they're actually passed
920 ;; function arguments. -- WHN 19990918
940 ;; First give the VM a peek at the call
944 (:direct
945 ;; The VM knows how to handle this.
946 )
947 (:transform
948 ;; The VM mostly knows how to handle this. We need
949 ;; to massage the call slightly, though.
952 ;; Let transforms have a crack at it.
954 #!+sb-show
960 #!+sb-show
975 ;;; If NODE doesn't return (i.e. return type is NIL), then terminate
976 ;;; the block there, and link it to the component tail.
977 ;;;
978 ;;; Except when called during IR1 convertion, we delete the
979 ;;; continuation if it has no other uses. (If it does have other uses,
980 ;;; we reoptimize.)
981 ;;;
982 ;;; Termination on the basis of a continuation type is
983 ;;; inhibited when:
984 ;;; -- The continuation is deleted (hence the assertion is spurious), or
985 ;;; -- We are in IR1 conversion (where THE assertions are subject to
986 ;;; weakening.) FIXME: Now THE assertions are not weakened, but new
987 ;;; uses can(?) be added later. -- APD, 2003-07-17
988 ;;;
989 ;;; Why do we need to consider LVAR type? -- APD, 2003-07-30
1000 ;; Even if the combination will never return, don't terminate if this
1001 ;; is the tail call of a XEP: doing that would inhibit TCO.
1028 t))))
1030 ;;; This is called both by IR1 conversion and IR1 optimization when
1031 ;;; they have verified the type signature for the call, and are
1032 ;;; wondering if something should be done to special-case the call. If
1033 ;;; CALL is a call to a global function, then see whether it defined
1034 ;;; or known:
1035 ;;; -- If a DEFINED-FUN should be inline expanded, then convert
1036 ;;; the expansion and change the call to call it. Expansion is
1037 ;;; enabled if :INLINE or if SPACE=0. If the FUNCTIONAL slot is
1038 ;;; true, we never expand, since this function has already been
1039 ;;; converted. Local call analysis will duplicate the definition
1040 ;;; if necessary. We claim that the parent form is LABELS for
1041 ;;; context declarations, since we don't want it to be considered
1042 ;;; a real global function.
1043 ;;; -- If it is a known function, mark it as such by setting the KIND.
1044 ;;;
1045 ;;; We return the leaf referenced (NIL if not a leaf) and the
1046 ;;; FUN-INFO assigned.
1070 ;; Inline: if the function has already been converted at another call
1071 ;; site in this component, we point this REF to the functional. If not,
1072 ;; we convert the expansion.
1073 ;;
1074 ;; For :INLINE case local call analysis will copy the expansion later,
1075 ;; but for :MAYBE-INLINE and NIL cases we only get one copy of the
1076 ;; expansion per component.
1077 ;;
1078 ;; FIXME: We also convert in :INLINE & FUNCTIONAL-KIND case below. What
1079 ;; is it for?
1083 name
1085 leaf
1086 inlinep
1088 ;; Allow backward references to this function from following
1089 ;; forms. (Reused only if policy matches.)
1095 ;; Convert.
1101 ;; If we've already converted, change ref to the converted
1102 ;; functional.
1114 ;;; Check whether CALL satisfies TYPE. If so, apply the type to the
1115 ;;; call, and do MAYBE-TERMINATE-BLOCK and return the values of
1116 ;;; RECOGNIZE-KNOWN-CALL. If an error, set the combination kind and
1117 ;;; return NIL, NIL. If the type is just FUNCTION, then skip the
1118 ;;; syntax check, arg/result type processing, but still call
1119 ;;; RECOGNIZE-KNOWN-CALL, since the call might be to a known lambda,
1120 ;;; and that checking is done by local call analysis.
1129 ;; Using the defined-type too early is a bit of a waste: during
1130 ;; conversion we cannot use the untrusted ASSERT-CALL-TYPE, etc.
1135 ;; Don't validate multiple times against the same leaf --
1136 ;; it doesn't add any information, but may generate the same warning
1137 ;; multiple times.
1141 :result-test nil
1143 #'compiler-warn
1146 same-file-p)
1152 :result-test nil
1162 ;;; This is called by IR1-OPTIMIZE when the function for a call has
1163 ;;; changed. If the call is local, we try to LET-convert it, and
1164 ;;; derive the result type. If it is a :FULL call, we validate it
1165 ;;; against the type, which recognizes known calls, does inline
1166 ;;; expansion, etc. If a call to a predicate in a non-conditional
1167 ;;; position or to a function with a source transform, then we
1168 ;;; reconvert the form to give IR1 another chance.
1175 (:local
1180 (:full
1188 call))
1196 predicate)
1210 \f
1211 ;;;; known function optimization
1213 ;;; Add a failed optimization note to FAILED-OPTIMZATIONS for NODE,
1214 ;;; FUN and ARGS. If there is already a note for NODE and TRANSFORM,
1215 ;;; replace it, otherwise add a new one.
1226 ;;; Attempt to transform NODE using TRANSFORM-FUNCTION, subject to the
1227 ;;; call type constraint TRANSFORM-TYPE. If we are inhibited from
1228 ;;; doing the transform for some reason and FLAME is true, then we
1229 ;;; make a note of the message in FAILED-OPTIMIZATIONS for IR1
1230 ;;; finalize to pick up. We return true if the transform failed, and
1231 ;;; thus further transformation should be attempted. We return false
1232 ;;; if either the transform succeeded or was aborted.
1252 (:none
1254 nil)
1255 (:aborted
1260 nil)
1261 (:failure
1267 t)
1268 (:delayed
1270 nil))))
1273 type
1277 t)
1279 t))))
1281 ;;; When we don't like an IR1 transform, we throw the severity/reason
1282 ;;; and args.
1283 ;;;
1284 ;;; GIVE-UP-IR1-TRANSFORM is used to throw out of an IR1 transform,
1285 ;;; aborting this attempt to transform the call, but admitting the
1286 ;;; possibility that this or some other transform will later succeed.
1287 ;;; If arguments are supplied, they are format arguments for an
1288 ;;; efficiency note.
1289 ;;;
1290 ;;; ABORT-IR1-TRANSFORM is used to throw out of an IR1 transform and
1291 ;;; force a normal call to the function at run time. No further
1292 ;;; optimizations will be attempted.
1293 ;;;
1294 ;;; DELAY-IR1-TRANSFORM is used to throw out of an IR1 transform, and
1295 ;;; delay the transform on the node until later. REASONS specifies
1296 ;;; when the transform will be later retried. The :OPTIMIZE reason
1297 ;;; causes the transform to be delayed until after the current IR1
1298 ;;; optimization pass. The :CONSTRAINT reason causes the transform to
1299 ;;; be delayed until after constraint propagation.
1300 ;;;
1301 ;;; FIXME: Now (0.6.11.44) that there are 4 variants of this (GIVE-UP,
1302 ;;; ABORT, DELAY/:OPTIMIZE, DELAY/:CONSTRAINT) and we're starting to
1303 ;;; do CASE operations on the various REASON values, it might be a
1304 ;;; good idea to go OO, representing the reasons by objects, using
1305 ;;; CLOS methods on the objects instead of CASE, and (possibly) using
1306 ;;; SIGNAL instead of THROW.
1323 ;;; Clear any delayed transform with no reasons - these should have
1324 ;;; been tried in the last pass. Then remove the reason from the
1325 ;;; delayed transform reasons, and if any become empty then set
1326 ;;; reoptimize flags for the node. Return true if any transforms are
1327 ;;; to be retried.
1343 reoptimize))
1345 ;;; Take the lambda-expression RES, IR1 convert it in the proper
1346 ;;; environment, and then install it as the function for the call
1347 ;;; NODE. We do local call analysis so that the new function is
1348 ;;; integrated into the control flow.
1349 ;;;
1350 ;;; We require the original function source name in order to generate
1351 ;;; a meaningful debug name for the lambda we set up. (It'd be
1352 ;;; possible to do this starting from debug names as well as source
1353 ;;; names, but as of sbcl-0.7.1.5, there was no need for this
1354 ;;; generality, since source names are always known to our callers.)
1360 ;; The internal variables of a transform are not going to be
1361 ;; interesting to the debugger, so there's no sense in
1362 ;; suppressing the substitution of variables with only one use
1363 ;; (the extra variables can slow down constraint propagation).
1364 ;;
1365 ;; This needs to be done before the WITH-IR1-ENVIRONMENT-FROM-NODE,
1366 ;; so that it will bind *LEXENV* to the right environment.
1379 res
1388 ;;; Replace a call to a foldable function of constant arguments with
1389 ;;; the result of evaluating the form. If there is an error during the
1390 ;;; evaluation, we give a warning and leave the call alone, making the
1391 ;;; call a :ERROR call.
1392 ;;;
1393 ;;; If there is more than one value, then we transform the call into a
1394 ;;; VALUES form.
1400 args
1401 call
1402 ;; Note: CMU CL had COMPILER-WARN here, and that
1403 ;; seems more natural, but it's probably not.
1404 ;;
1405 ;; It's especially not while bug 173 exists:
1406 ;; Expressions like
1407 ;; (COND (END
1408 ;; (UNLESS (OR UNSAFE? (<= END SIZE)))
1409 ;; ...))
1410 ;; can cause constant-folding TYPE-ERRORs (in
1411 ;; #'<=) when END can be proved to be NIL, even
1412 ;; though the code is perfectly legal and safe
1413 ;; because a NIL value of END means that the
1414 ;; #'<= will never be executed.
1415 ;;
1416 ;; Moreover, even without bug 173,
1417 ;; quite-possibly-valid code like
1418 ;; (COND ((NONINLINED-PREDICATE END)
1419 ;; (UNLESS (<= END SIZE))
1420 ;; ...))
1421 ;; (where NONINLINED-PREDICATE is something the
1422 ;; compiler can't do at compile time, but which
1423 ;; turns out to make the #'<= expression
1424 ;; unreachable when END=NIL) could cause errors
1425 ;; when the compiler tries to constant-fold (<=
1426 ;; END SIZE).
1427 ;;
1428 ;; So, with or without bug 173, it'd be
1429 ;; unnecessarily evil to do a full
1430 ;; COMPILER-WARNING (and thus return FAILURE-P=T
1431 ;; from COMPILE-FILE) for legal code, so we we
1432 ;; use a wimpier COMPILE-STYLE-WARNING instead.
1434 ;; On the other hand, for code we control, we
1435 ;; should be able to work around any bug
1436 ;; 173-related problems, and in particular we
1437 ;; want to be alerted to calls to our own
1438 ;; functions which aren't being folded away; a
1439 ;; COMPILER-WARNING is butch enough to stop the
1440 ;; SBCL build itself in its tracks.
1460 call
1464 fun-name))))))
1466 \f
1467 ;;;; local call optimization
1469 ;;; Propagate TYPE to LEAF and its REFS, marking things changed.
1470 ;;;
1471 ;;; If the leaf type is a function type, then just leave it alone, since TYPE
1472 ;;; is never going to be more specific than that (and TYPE-INTERSECTION would
1473 ;;; choke.)
1474 ;;;
1475 ;;; Also, if the type is one requiring special care don't touch it if the leaf
1476 ;;; has multiple references -- otherwise LVAR-CONSERVATIVE-TYPE is screwed.
1491 ;; KLUDGE: LET var substitution
1497 ;;; Iteration variable: exactly one SETQ of the form:
1498 ;;;
1499 ;;; (let ((var initial))
1500 ;;; ...
1501 ;;; (setq var (+ var step))
1502 ;;; ...)
1528 ;; Detect cases like (LOOP FOR 1.0 to 5.0 ...), where
1529 ;; the initial and the step are of different types,
1530 ;; and the step is less contagious.
1533 step-type))))
1572 :low low
1573 :high high
1576 "check for iteration variable reoptimization"
1586 ;;; Figure out the type of a LET variable that has sets. We compute
1587 ;;; the union of the INITIAL-TYPE and the types of all the set
1588 ;;; values and to a PROPAGATE-TO-REFS with this type.
1608 ;;; If a LET variable, find the initial value's type and do
1609 ;;; PROPAGATE-FROM-SETS. We also derive the VALUE's type as the node's
1610 ;;; type.
1626 ;;; Return true if the value of REF will always be the same (and is
1627 ;;; thus legal to substitute.)
1639 (:global-function
1646 ;;; If we have a non-set LET var with a single use, then (if possible)
1647 ;;; replace the variable reference's LVAR with the arg lvar.
1648 ;;;
1649 ;;; We change the REF to be a reference to NIL with unused value, and
1650 ;;; let it be flushed as dead code. A side effect of this substitution
1651 ;;; is to delete the variable.
1659 ;; Think about (LET ((A ...)) (IF ... A ...)): two
1660 ;; LVAR-USEs should not be met on one path. Another problem
1661 ;; is with dynamic-extent.
1664 ;; If the destinatation is dynamic extent, don't substitute unless
1665 ;; the source is as well.
1670 ;; we should not change lifetime of unknown values lvars
1682 ;; While CRETURN and EXIT nodes may be known-values,
1683 ;; they have their own complications, such as
1684 ;; substitution into CRETURN may create new tail calls.
1685 nil)
1688 t))
1694 ;; Really it is (EQ (LVAR-USES LVAR) REF):
1695 t)
1700 ;; KLUDGE: it should be (TYPE-CHECK 0)
1704 ;; FIXME
1705 t)
1713 t)))
1715 ;;; Delete a LET, removing the call and bind nodes, and warning about
1716 ;;; any unreferenced variables. Note that FLUSH-DEAD-CODE will come
1717 ;;; along right away and delete the REF and then the lambda, since we
1718 ;;; flush the FUN lvar.
1733 ;;; This function is called when one of the arguments to a LET
1734 ;;; changes. We look at each changed argument. If the corresponding
1735 ;;; variable is set, then we call PROPAGATE-FROM-SETS. Otherwise, we
1736 ;;; consider substituting for the variable, and also propagate
1737 ;;; derived-type information for the arg to all the VAR's refs.
1738 ;;;
1739 ;;; Substitution is inhibited when the arg leaf's derived type isn't a
1740 ;;; subtype of the argument's leaf type. This prevents type checking
1741 ;;; from being defeated, and also ensures that the best representation
1742 ;;; for the variable can be used.
1743 ;;;
1744 ;;; Substitution of individual references is inhibited if the
1745 ;;; reference is in a different component from the home. This can only
1746 ;;; happen with closures over top level lambda vars. In such cases,
1747 ;;; the references may have already been compiled, and thus can't be
1748 ;;; retroactively modified.
1749 ;;;
1750 ;;; If all of the variables are deleted (have no references) when we
1751 ;;; are done, then we delete the LET.
1752 ;;;
1753 ;;; Note that we are responsible for clearing the LVAR-REOPTIMIZE
1754 ;;; flags.
1769 ;; (NODE-DERIVED-TYPE USE) would
1770 ;; be better -- APD, 2003-05-15
1777 t)
1780 nil)))
1781 leaf var)))
1782 t)))))
1794 ;;; This function is called when one of the args to a non-LET local
1795 ;;; call changes. For each changed argument corresponding to an unset
1796 ;;; variable, we compute the union of the types across all calls and
1797 ;;; propagate this type information to the var's refs.
1798 ;;;
1799 ;;; If the function has an entry-fun, then we don't do anything: since
1800 ;;; it has a XEP we would not discover anything.
1801 ;;;
1802 ;;; If the function is an optional-entry-point, we will just make sure
1803 ;;; &REST lists are known to be lists. Doing the regular rigamarole
1804 ;;; can erronously propagate too strict types into refs: see
1805 ;;; BUG-655203-REGRESSION in tests/compiler.pure.lisp.
1806 ;;;
1807 ;;; We can clear the LVAR-REOPTIMIZE flags for arguments in all calls
1808 ;;; corresponding to changed arguments in CALL, since the only use in
1809 ;;; IR1 optimization of the REOPTIMIZE flag for local call args is
1810 ;;; right here.
1815 ;; We can still make sure &REST is known to be a list.
1820 ;; The normal case.
1828 vars))
1844 union)))))
1847 and type in union
1851 \f
1852 ;;;; multiple values optimization
1854 ;;; Do stuff to notice a change to a MV combination node. There are
1855 ;;; two main branches here:
1856 ;;; -- If the call is local, then it is already a MV let, or should
1857 ;;; become one. Note that although all :LOCAL MV calls must eventually
1858 ;;; be converted to :MV-LETs, there can be a window when the call
1859 ;;; is local, but has not been LET converted yet. This is because
1860 ;;; the entry-point lambdas may have stray references (in other
1861 ;;; entry points) that have not been deleted yet.
1862 ;;; -- The call is full. This case is somewhat similar to the non-MV
1863 ;;; combination optimization: we propagate return type information and
1864 ;;; notice non-returning calls. We also have an optimization
1865 ;;; which tries to convert MV-CALLs into MV-binds.
1868 (:local
1877 (:full
1900 ;;; Propagate derived type info from the values lvar to the vars.
1907 n-vars)))
1909 and type in types
1916 ;;; If possible, convert a general MV call to an MV-BIND. We can do
1917 ;;; this if:
1918 ;;; -- The call has only one argument, and
1919 ;;; -- The function has a known fixed number of arguments, or
1920 ;;; -- The argument yields a known fixed number of values.
1921 ;;;
1922 ;;; What we do is change the function in the MV-CALL to be a lambda
1923 ;;; that "looks like an MV bind", which allows
1924 ;;; IR1-OPTIMIZE-MV-COMBINATION to notice that this call can be
1925 ;;; converted (the next time around.) This new lambda just calls the
1926 ;;; actual function with the MV-BIND variables as arguments. Note that
1927 ;;; this new MV bind is not let-converted immediately, as there are
1928 ;;; going to be stray references from the entry-point functions until
1929 ;;; they get deleted.
1930 ;;;
1931 ;;; In order to avoid loss of argument count checking, we only do the
1932 ;;; transformation according to a known number of expected argument if
1933 ;;; safety is unimportant. We can always convert if we know the number
1934 ;;; of actual values, since the normal call that we build will still
1935 ;;; do any appropriate argument count checking.
1936 ;;;
1937 ;;; We only attempt the transformation if the called function is a
1938 ;;; constant reference. This allows us to just splice the leaf into
1939 ;;; the new function, instead of trying to somehow bind the function
1940 ;;; expression. The leaf must be constant because we are evaluating it
1941 ;;; again in a different place. This also has the effect of squelching
1942 ;;; multiple warnings when there is an argument count error.
1964 "MULTIPLE-VALUE-CALL with ~R values when the function expects ~
1965 at least ~R."
1966 total-nvals min)
1971 "MULTIPLE-VALUE-CALL with ~R values when the function expects ~
1972 at most ~R."
1973 total-nvals max)
1980 min)
1999 ;;; If we see:
2000 ;;; (multiple-value-bind
2001 ;;; (x y)
2002 ;;; (values xx yy)
2003 ;;; ...)
2004 ;;; Convert to:
2005 ;;; (let ((x xx)
2006 ;;; (y yy))
2007 ;;; ...)
2008 ;;;
2009 ;;; What we actually do is convert the VALUES combination into a
2010 ;;; normal LET combination calling the original :MV-LET lambda. If
2011 ;;; there are extra args to VALUES, discard the corresponding
2012 ;;; lvars. If there are insufficient args, insert references to NIL.
2035 for prev = node-prev then ctran
2041 use ctran))
2055 ;; Propagate derived types from the VALUES call to its args:
2056 ;; transforms can leave the VALUES call with a better type
2057 ;; than its args have, so make sure not to throw that away.
2063 ;; Propagate declared types of MV-BIND variables.
2066 t)))
2068 ;;; If we see:
2069 ;;; (values-list (list x y z))
2070 ;;;
2071 ;;; Convert to:
2072 ;;; (values x y z)
2073 ;;;
2074 ;;; In implementation, this is somewhat similar to
2075 ;;; CONVERT-MV-BIND-TO-LET. We grab the args of LIST and make them
2076 ;;; args of the VALUES-LIST call, flushing the old argument lvar
2077 ;;; (allowing the LIST to be flushed.)
2078 ;;;
2079 ;;; FIXME: Thus we lose possible type assertions on (LIST ...).
2086 ;; FIXME: VALUES might not satisfy an assertion on NODE-LVAR.
2098 t)))
2100 ;;; If VALUES appears in a non-MV context, then effectively convert it
2101 ;;; to a PROG1. This allows the computation of the additional values
2102 ;;; to become dead code.
2114 val))
2115 nil))
2117 ;;; TODO:
2118 ;;; - CAST chains;
2142 lvar)
2143 ;; Pathwise removing of CAST
2146 next-block)
2174 ;; FIXME: Do it in one step.
2178 value
2184 ;; FIXME: Derived type.
2189 ;; KLUDGE: FILTER-LVAR does not work for non-returning
2190 ;; functions, so we declare the return type of
2191 ;; %COMPILE-TIME-TYPE-ERROR to be * and derive the real type
2192 ;; here.
2196 ;; FIXME: Is it necessary?