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;;;; This file implements the constraint propagation phase of the
;;;; compiler, which uses global flow analysis to obtain dynamic type
;;;; information.
;;;; This software is part of the SBCL system. See the README file for
;;;; more information.
;;;;
;;;; This software is derived from the CMU CL system, which was
;;;; written at Carnegie Mellon University and released into the
;;;; public domain. The software is in the public domain and is
;;;; provided with absolutely no warranty. See the COPYING and CREDITS
;;;; files for more information.
;;; TODO:
;;;
;;; -- documentation
;;;
;;; -- MV-BIND, :ASSIGNMENT
;;;
;;; Note: The functions in this file that accept constraint sets are
;;; actually receiving the constraint sets associated with nodes,
;;; blocks, and lambda-vars. It might be make CP easier to understand
;;; and work on if these functions traded in nodes, blocks, and
;;; lambda-vars directly.
;;; Problems:
;;;
;;; -- Constraint propagation badly interacts with bottom-up type
;;; inference. Consider
;;;
;;; (defun foo (n &aux (i 42))
;;; (declare (optimize speed))
;;; (declare (fixnum n)
;;; #+nil (type (integer 0) i))
;;; (tagbody
;;; (setq i 0)
;;; :loop
;;; (when (>= i n) (go :exit))
;;; (setq i (1+ i))
;;; (go :loop)
;;; :exit))
;;;
;;; In this case CP cannot even infer that I is of class INTEGER.
;;;
;;; -- In the above example if we place the check after SETQ, CP will
;;; fail to infer (< I FIXNUM): it does not understand that this
;;; constraint follows from (TYPEP I (INTEGER 0 0)).
(in-package "SB!C")
;;; *CONSTRAINT-UNIVERSE* gets bound in IR1-PHASES to a fresh,
;;; zero-length, non-zero-total-size vector-with-fill-pointer.
(declaim (type (and vector (not simple-vector)) *constraint-universe*))
(defvar *constraint-universe*)
(deftype constraint-y () '(or ctype lvar lambda-var constant))
(defstruct (constraint
(:include sset-element)
(:constructor make-constraint (number kind x y not-p))
(:copier nil))
;; the kind of constraint we have:
;;
;; TYPEP
;; X is a LAMBDA-VAR and Y is a CTYPE. The value of X is
;; constrained to be of type Y.
;;
;; > or <
;; X is a lambda-var and Y is a CTYPE. The relation holds
;; between X and some object of type Y.
;;
;; EQL
;; X is a LAMBDA-VAR and Y is a LVAR, a LAMBDA-VAR or a CONSTANT.
;; The relation is asserted to hold.
(kind nil :type (member typep < > eql))
;; The operands to the relation.
(x nil :type lambda-var)
(y nil :type constraint-y)
;; If true, negates the sense of the constraint, so the relation
;; does *not* hold.
(not-p nil :type boolean))
;;; Historically, CMUCL and SBCL have used a sparse set implementation
;;; for which most operations are O(n) (see sset.lisp), but at the
;;; cost of at least a full word of pointer for each constraint set
;;; element. Using bit-vectors instead of pointer structures saves a
;;; lot of space and thus GC time (particularly on 64-bit machines),
;;; and saves time on copy, union, intersection, and difference
;;; operations; but makes iteration slower. Circa September 2008,
;;; switching to bit-vectors gave a modest (5-10%) improvement in real
;;; compile time for most Lisp systems, and as much as 20-30% for some
;;; particularly CP-dependent systems.
;;; It's bad to leave commented code in files, but if some clever
;;; person comes along and makes SSETs better than bit-vectors as sets
;;; for constraint propagation, or if bit-vectors on some XC host
;;; really lose compared to SSETs, here's the conset API as a wrapper
;;; around SSETs:
#+nil
(progn
(deftype conset () 'sset)
(declaim (ftype (sfunction (conset) boolean) conset-empty))
(declaim (ftype (sfunction (conset) conset) copy-conset))
(declaim (ftype (sfunction (constraint conset) boolean) conset-member))
(declaim (ftype (sfunction (constraint conset) boolean) conset-adjoin))
(declaim (ftype (sfunction (conset conset) boolean) conset=))
(declaim (ftype (sfunction (conset conset) (values)) conset-union))
(declaim (ftype (sfunction (conset conset) (values)) conset-intersection))
(declaim (ftype (sfunction (conset conset) (values)) conset-difference))
(defun make-conset () (make-sset))
(defmacro do-conset-elements ((constraint conset &optional result) &body body)
`(do-sset-elements (,constraint ,conset ,result) ,@body))
(defmacro do-conset-intersection
((constraint conset1 conset2 &optional result) &body body)
`(do-conset-elements (,constraint ,conset1 ,result)
(when (conset-member ,constraint ,conset2)
,@body)))
(defun conset-empty (conset) (sset-empty conset))
(defun copy-conset (conset) (copy-sset conset))
(defun conset-member (constraint conset) (sset-member constraint conset))
(defun conset-adjoin (constraint conset) (sset-adjoin constraint conset))
(defun conset= (conset1 conset2) (sset= conset1 conset2))
;; Note: CP doesn't ever care whether union, intersection, and
;; difference change the first set. (This is an important degree of
;; freedom, since some ways of implementing sets lose a great deal
;; when these operations are required to track changes.)
(defun conset-union (conset1 conset2)
(sset-union conset1 conset2) (values))
(defun conset-intersection (conset1 conset2)
(sset-intersection conset1 conset2) (values))
(defun conset-difference (conset1 conset2)
(sset-difference conset1 conset2) (values)))
(locally
;; This is performance critical for the compiler, and benefits
;; from the following declarations. Probably you'll want to
;; disable these declarations when debugging consets.
(declare #-sb-xc-host (optimize (speed 3) (safety 0) (space 0)))
(declaim (inline %constraint-number))
(defun %constraint-number (constraint)
(sset-element-number constraint))
(defstruct (conset
(:constructor make-conset ())
(:copier %copy-conset))
(vector (make-array
;; FIXME: make POWER-OF-TWO-CEILING available earlier?
(ash 1 (integer-length (1- (length *constraint-universe*))))
:element-type 'bit :initial-element 0)
:type simple-bit-vector)
;; Bit-vectors win over lightweight hashes for copy, union,
;; intersection, difference, but lose for iteration if you iterate
;; over the whole vector. Tracking extrema helps a bit.
(min 0 :type fixnum)
(max 0 :type fixnum))
(defmacro do-conset-elements ((constraint conset &optional result) &body body)
(with-unique-names (vector index start end
#-sb-xc-host ignore
#-sb-xc-host constraint-universe-end)
(let* ((constraint-universe #+sb-xc-host '*constraint-universe*
#-sb-xc-host (sb!xc:gensym "UNIVERSE"))
(with-array-data
#+sb-xc-host '(progn)
#-sb-xc-host `(with-array-data
((,constraint-universe *constraint-universe*)
(,ignore 0) (,constraint-universe-end nil)
:check-fill-pointer t)
(declare (ignore ,ignore))
(aver (<= ,end ,constraint-universe-end)))))
`(let* ((,vector (conset-vector ,conset))
(,start (conset-min ,conset))
(,end (min (conset-max ,conset) (length ,vector))))
(,@with-array-data
(do ((,index ,start (1+ ,index))) ((>= ,index ,end) ,result)
(when (plusp (sbit ,vector ,index))
(let ((,constraint (elt ,constraint-universe ,index)))
,@body))))))))
;; Oddly, iterating just between the maximum of the two sets' minima
;; and the minimum of the sets' maxima slowed down CP.
(defmacro do-conset-intersection
((constraint conset1 conset2 &optional result) &body body)
`(do-conset-elements (,constraint ,conset1 ,result)
(when (conset-member ,constraint ,conset2)
,@body)))
(defun conset-empty (conset)
(or (= (conset-min conset) (conset-max conset))
;; TODO: I bet FIND on bit-vectors can be optimized, if it
;; isn't.
(not (find 1 (conset-vector conset)
:start (conset-min conset)
;; By inspection, supplying :END here breaks the
;; build with a "full call to
;; DATA-VECTOR-REF-WITH-OFFSET" in the
;; cross-compiler. If that should change, add
;; :end (conset-max conset)
))))
(defun copy-conset (conset)
(let ((ret (%copy-conset conset)))
(setf (conset-vector ret) (copy-seq (conset-vector conset)))
ret))
(defun %conset-grow (conset new-size)
(declare (type index new-size))
(setf (conset-vector conset)
(replace (the simple-bit-vector
(make-array
(ash 1 (integer-length (1- new-size)))
:element-type 'bit
:initial-element 0))
(the simple-bit-vector
(conset-vector conset)))))
(declaim (inline conset-grow))
(defun conset-grow (conset new-size)
(declare (type index new-size))
(when (< (length (conset-vector conset)) new-size)
(%conset-grow conset new-size))
(values))
(defun conset-member (constraint conset)
(let ((number (%constraint-number constraint))
(vector (conset-vector conset)))
(when (< number (length vector))
(plusp (sbit vector number)))))
(defun conset-adjoin (constraint conset)
(prog1
(not (conset-member constraint conset))
(let ((number (%constraint-number constraint)))
(conset-grow conset (1+ number))
(setf (sbit (conset-vector conset) number) 1)
(setf (conset-min conset) (min number (conset-min conset)))
(when (>= number (conset-max conset))
(setf (conset-max conset) (1+ number))))))
(defun conset= (conset1 conset2)
(let* ((vector1 (conset-vector conset1))
(vector2 (conset-vector conset2))
(length1 (length vector1))
(length2 (length vector2)))
(if (= length1 length2)
;; When the lengths are the same, we can rely on EQUAL being
;; nicely optimized on bit-vectors.
(equal vector1 vector2)
(multiple-value-bind (shorter longer)
(if (< length1 length2)
(values vector1 vector2)
(values vector2 vector1))
;; FIXME: make MISMATCH fast on bit-vectors.
(dotimes (index (length shorter))
(when (/= (sbit vector1 index) (sbit vector2 index))
(return-from conset= nil)))
(if (find 1 longer :start (length shorter))
nil
t)))))
(macrolet
((defconsetop (name bit-op)
`(defun ,name (conset-1 conset-2)
(declare (optimize (speed 3) (safety 0)))
(let* ((size-1 (length (conset-vector conset-1)))
(size-2 (length (conset-vector conset-2)))
(new-size (max size-1 size-2)))
(conset-grow conset-1 new-size)
(conset-grow conset-2 new-size))
(let ((vector1 (conset-vector conset-1))
(vector2 (conset-vector conset-2)))
(declare (simple-bit-vector vector1 vector2))
(setf (conset-vector conset-1) (,bit-op vector1 vector2 t))
;; Update the extrema.
,(ecase name
((conset-union)
`(setf (conset-min conset-1)
(min (conset-min conset-1)
(conset-min conset-2))
(conset-max conset-1)
(max (conset-max conset-1)
(conset-max conset-2))))
((conset-intersection)
`(let ((start (max (conset-min conset-1)
(conset-min conset-2)))
(end (min (conset-max conset-1)
(conset-max conset-2))))
(setf (conset-min conset-1)
(if (> start end)
0
(or (position 1 (conset-vector conset-1)
:start start :end end)
0))
(conset-max conset-1)
(if (> start end)
0
(let ((position
(position
1 (conset-vector conset-1)
:start start :end end :from-end t)))
(if position
(1+ position)
0))))))
((conset-difference)
`(setf (conset-min conset-1)
(or (position 1 (conset-vector conset-1)
:start (conset-min conset-1)
:end (conset-max conset-1))
0)
(conset-max conset-1)
(let ((position
(position
1 (conset-vector conset-1)
:start (conset-min conset-1)
:end (conset-max conset-1)
:from-end t)))
(if position
(1+ position)
0))))))
(values))))
(defconsetop conset-union bit-ior)
(defconsetop conset-intersection bit-and)
(defconsetop conset-difference bit-andc2)))
(defun find-constraint (kind x y not-p)
(declare (type lambda-var x) (type constraint-y y) (type boolean not-p))
(etypecase y
(ctype
(do-conset-elements (con (lambda-var-constraints x) nil)
(when (and (eq (constraint-kind con) kind)
(eq (constraint-not-p con) not-p)
(type= (constraint-y con) y))
(return con))))
((or lvar constant)
(do-conset-elements (con (lambda-var-constraints x) nil)
(when (and (eq (constraint-kind con) kind)
(eq (constraint-not-p con) not-p)
(eq (constraint-y con) y))
(return con))))
(lambda-var
(do-conset-elements (con (lambda-var-constraints x) nil)
(when (and (eq (constraint-kind con) kind)
(eq (constraint-not-p con) not-p)
(let ((cx (constraint-x con)))
(eq (if (eq cx x)
(constraint-y con)
cx)
y)))
(return con))))))
;;; Return a constraint for the specified arguments. We only create a
;;; new constraint if there isn't already an equivalent old one,
;;; guaranteeing that all equivalent constraints are EQ. This
;;; shouldn't be called on LAMBDA-VARs with no CONSTRAINTS set.
(defun find-or-create-constraint (kind x y not-p)
(declare (type lambda-var x) (type constraint-y y) (type boolean not-p))
(or (find-constraint kind x y not-p)
(let ((new (make-constraint (length *constraint-universe*)
kind x y not-p)))
(vector-push-extend new *constraint-universe*
(1+ (length *constraint-universe*)))
(conset-adjoin new (lambda-var-constraints x))
(when (lambda-var-p y)
(conset-adjoin new (lambda-var-constraints y)))
new)))
;;; If REF is to a LAMBDA-VAR with CONSTRAINTs (i.e. we can do flow
;;; analysis on it), then return the LAMBDA-VAR, otherwise NIL.
#!-sb-fluid (declaim (inline ok-ref-lambda-var))
(defun ok-ref-lambda-var (ref)
(declare (type ref ref))
(let ((leaf (ref-leaf ref)))
(when (and (lambda-var-p leaf)
(lambda-var-constraints leaf))
leaf)))
;;; See if LVAR's single USE is a REF to a LAMBDA-VAR and they are EQL
;;; according to CONSTRAINTS. Return LAMBDA-VAR if so.
(defun ok-lvar-lambda-var (lvar constraints)
(declare (type lvar lvar))
(let ((use (lvar-uses lvar)))
(cond ((ref-p use)
(let ((lambda-var (ok-ref-lambda-var use)))
(when lambda-var
(let ((constraint (find-constraint 'eql lambda-var lvar nil)))
(when (and constraint (conset-member constraint constraints))
lambda-var)))))
((cast-p use)
(ok-lvar-lambda-var (cast-value use) constraints)))))
(defmacro do-eql-vars ((symbol (var constraints) &optional result) &body body)
(once-only ((var var))
`(let ((,symbol ,var))
(flet ((body-fun ()
,@body))
(body-fun)
(do-conset-elements (con ,constraints ,result)
(let ((other (and (eq (constraint-kind con) 'eql)
(eq (constraint-not-p con) nil)
(cond ((eq ,var (constraint-x con))
(constraint-y con))
((eq ,var (constraint-y con))
(constraint-x con))
(t
nil)))))
(when other
(setq ,symbol other)
(when (lambda-var-p ,symbol)
(body-fun)))))))))
;;;; Searching constraints
;;; Add the indicated test constraint to BLOCK. We don't add the
;;; constraint if the block has multiple predecessors, since it only
;;; holds on this particular path.
(defun add-test-constraint (fun x y not-p constraints target)
(cond ((and (eq 'eql fun) (lambda-var-p y) (not not-p))
(add-eql-var-var-constraint x y constraints target))
(t
(do-eql-vars (x (x constraints))
(let ((con (find-or-create-constraint fun x y not-p)))
(conset-adjoin con target)))))
(values))
;;; Add complementary constraints to the consequent and alternative
;;; blocks of IF. We do nothing if X is NIL.
(defun add-complement-constraints (fun x y not-p constraints
consequent-constraints
alternative-constraints)
(when x
(add-test-constraint fun x y not-p constraints
consequent-constraints)
(add-test-constraint fun x y (not not-p) constraints
alternative-constraints))
(values))
;;; Add test constraints to the consequent and alternative blocks of
;;; the test represented by USE.
(defun add-test-constraints (use if constraints)
(declare (type node use) (type cif if))
;; Note: Even if we do (IF test exp exp) => (PROGN test exp)
;; optimization, the *MAX-OPTIMIZE-ITERATIONS* cutoff means that we
;; can't guarantee that the optimization will be done, so we still
;; need to avoid barfing on this case.
(unless (eq (if-consequent if) (if-alternative if))
(let ((consequent-constraints (make-conset))
(alternative-constraints (make-conset)))
(macrolet ((add (fun x y not-p)
`(add-complement-constraints ,fun ,x ,y ,not-p
constraints
consequent-constraints
alternative-constraints)))
(typecase use
(ref
(add 'typep (ok-lvar-lambda-var (ref-lvar use) constraints)
(specifier-type 'null) t))
(combination
(unless (eq (combination-kind use)
:error)
(let ((name (lvar-fun-name
(basic-combination-fun use)))
(args (basic-combination-args use)))
(case name
((%typep %instance-typep)
(let ((type (second args)))
(when (constant-lvar-p type)
(let ((val (lvar-value type)))
(add 'typep
(ok-lvar-lambda-var (first args) constraints)
(if (ctype-p val)
val
(let ((*compiler-error-context* use))
(specifier-type val)))
nil)))))
((eq eql)
(let* ((arg1 (first args))
(var1 (ok-lvar-lambda-var arg1 constraints))
(arg2 (second args))
(var2 (ok-lvar-lambda-var arg2 constraints)))
;; The code below assumes that the constant is the
;; second argument in case of variable to constant
;; comparision which is sometimes true (see source
;; transformations for EQ, EQL and CHAR=). Fixing
;; that would result in more constant substitutions
;; which is not a universally good thing, thus the
;; unnatural asymmetry of the tests.
(cond ((not var1)
(when var2
(add-test-constraint 'typep var2 (lvar-type arg1)
nil constraints
consequent-constraints)))
(var2
(add 'eql var1 var2 nil))
((constant-lvar-p arg2)
(add 'eql var1 (ref-leaf (principal-lvar-use arg2))
nil))
(t
(add-test-constraint 'typep var1 (lvar-type arg2)
nil constraints
consequent-constraints)))))
((< >)
(let* ((arg1 (first args))
(var1 (ok-lvar-lambda-var arg1 constraints))
(arg2 (second args))
(var2 (ok-lvar-lambda-var arg2 constraints)))
(when var1
(add name var1 (lvar-type arg2) nil))
(when var2
(add (if (eq name '<) '> '<) var2 (lvar-type arg1) nil))))
(t
(let ((ptype (gethash name *backend-predicate-types*)))
(when ptype
(add 'typep (ok-lvar-lambda-var (first args) constraints)
ptype nil))))))))))
(values consequent-constraints alternative-constraints))))
;;;; Applying constraints
;;; Return true if X is an integer NUMERIC-TYPE.
(defun integer-type-p (x)
(declare (type ctype x))
(and (numeric-type-p x)
(eq (numeric-type-class x) 'integer)
(eq (numeric-type-complexp x) :real)))
;;; Given that an inequality holds on values of type X and Y, return a
;;; new type for X. If GREATER is true, then X was greater than Y,
;;; otherwise less. If OR-EQUAL is true, then the inequality was
;;; inclusive, i.e. >=.
;;;
;;; If GREATER (or not), then we max (or min) in Y's lower (or upper)
;;; bound into X and return that result. If not OR-EQUAL, we can go
;;; one greater (less) than Y's bound.
(defun constrain-integer-type (x y greater or-equal)
(declare (type numeric-type x y))
(flet ((exclude (x)
(cond ((not x) nil)
(or-equal x)
(greater (1+ x))
(t (1- x))))
(bound (x)
(if greater (numeric-type-low x) (numeric-type-high x))))
(let* ((x-bound (bound x))
(y-bound (exclude (bound y)))
(new-bound (cond ((not x-bound) y-bound)
((not y-bound) x-bound)
(greater (max x-bound y-bound))
(t (min x-bound y-bound)))))
(if greater
(modified-numeric-type x :low new-bound)
(modified-numeric-type x :high new-bound)))))
;;; Return true if X is a float NUMERIC-TYPE.
(defun float-type-p (x)
(declare (type ctype x))
(and (numeric-type-p x)
(eq (numeric-type-class x) 'float)
(eq (numeric-type-complexp x) :real)))
;;; Exactly the same as CONSTRAIN-INTEGER-TYPE, but for float numbers.
(defun constrain-float-type (x y greater or-equal)
(declare (type numeric-type x y))
(declare (ignorable x y greater or-equal)) ; for CROSS-FLOAT-INFINITY-KLUDGE
(aver (eql (numeric-type-class x) 'float))
(aver (eql (numeric-type-class y) 'float))
#+sb-xc-host ; (See CROSS-FLOAT-INFINITY-KLUDGE.)
x
#-sb-xc-host ; (See CROSS-FLOAT-INFINITY-KLUDGE.)
(labels ((exclude (x)
(cond ((not x) nil)
(or-equal x)
(t
(if (consp x)
x
(list x)))))
(bound (x)
(if greater (numeric-type-low x) (numeric-type-high x)))
(tighter-p (x ref)
(cond ((null x) nil)
((null ref) t)
((and or-equal
(= (type-bound-number x) (type-bound-number ref)))
;; X is tighter if REF is not an open bound and X is
(and (not (consp ref)) (consp x)))
(greater
(< (type-bound-number ref) (type-bound-number x)))
(t
(> (type-bound-number ref) (type-bound-number x))))))
(let* ((x-bound (bound x))
(y-bound (exclude (bound y)))
(new-bound (cond ((not x-bound)
y-bound)
((not y-bound)
x-bound)
((tighter-p y-bound x-bound)
y-bound)
(t
x-bound))))
(if greater
(modified-numeric-type x :low new-bound)
(modified-numeric-type x :high new-bound)))))
;;; Given the set of CONSTRAINTS for a variable and the current set of
;;; restrictions from flow analysis IN, set the type for REF
;;; accordingly.
(defun constrain-ref-type (ref constraints in)
(declare (type ref ref) (type conset constraints in))
;; KLUDGE: The NOT-SET and NOT-FPZ here are so that we don't need to
;; cons up endless union types when propagating large number of EQL
;; constraints -- eg. from large CASE forms -- instead we just
;; directly accumulate one XSET, and a set of fp zeroes, which we at
;; the end turn into a MEMBER-TYPE.
;;
;; Since massive symbol cases are an especially atrocious pattern
;; and the (NOT (MEMBER ...ton of symbols...)) will never turn into
;; a more useful type, don't propagate their negation except for NIL
;; unless SPEED > COMPILATION-SPEED.
(let ((res (single-value-type (node-derived-type ref)))
(constrain-symbols (policy ref (> speed compilation-speed)))
(not-set (alloc-xset))
(not-fpz nil)
(not-res *empty-type*)
(leaf (ref-leaf ref)))
(flet ((note-not (x)
(if (fp-zero-p x)
(push x not-fpz)
(when (or constrain-symbols (null x) (not (symbolp x)))
(add-to-xset x not-set)))))
;; KLUDGE: the implementations of DO-CONSET-INTERSECTION will
;; probably run faster when the smaller set comes first, so
;; don't change the order here.
(do-conset-intersection (con constraints in)
(let* ((x (constraint-x con))
(y (constraint-y con))
(not-p (constraint-not-p con))
(other (if (eq x leaf) y x))
(kind (constraint-kind con)))
(case kind
(typep
(if not-p
(if (member-type-p other)
(mapc-member-type-members #'note-not other)
(setq not-res (type-union not-res other)))
(setq res (type-approx-intersection2 res other))))
(eql
(unless (lvar-p other)
(let ((other-type (leaf-type other)))
(if not-p
(when (and (constant-p other)
(member-type-p other-type))
(note-not (constant-value other)))
(let ((leaf-type (leaf-type leaf)))
(cond
((or (constant-p other)
(and (leaf-refs other) ; protect from
; deleted vars
(csubtypep other-type leaf-type)
(not (type= other-type leaf-type))))
(change-ref-leaf ref other)
(when (constant-p other) (return)))
(t
(setq res (type-approx-intersection2
res other-type)))))))))
((< >)
(cond
((and (integer-type-p res) (integer-type-p y))
(let ((greater (eq kind '>)))
(let ((greater (if not-p (not greater) greater)))
(setq res
(constrain-integer-type res y greater not-p)))))
((and (float-type-p res) (float-type-p y))
(let ((greater (eq kind '>)))
(let ((greater (if not-p (not greater) greater)))
(setq res
(constrain-float-type res y greater not-p)))))))))))
(cond ((and (if-p (node-dest ref))
(or (xset-member-p nil not-set)
(csubtypep (specifier-type 'null) not-res)))
(setf (node-derived-type ref) *wild-type*)
(change-ref-leaf ref (find-constant t)))
(t
(setf not-res
(type-union not-res (make-member-type :xset not-set :fp-zeroes not-fpz)))
(derive-node-type ref
(make-single-value-type
(or (type-difference res not-res)
res)))
(maybe-terminate-block ref nil))))
(values))
;;;; Flow analysis
(defun maybe-add-eql-var-lvar-constraint (ref gen)
(let ((lvar (ref-lvar ref))
(leaf (ref-leaf ref)))
(when (and (lambda-var-p leaf) lvar)
(conset-adjoin (find-or-create-constraint 'eql leaf lvar nil)
gen))))
;;; Copy all CONSTRAINTS involving FROM-VAR - except the (EQL VAR
;;; LVAR) ones - to all of the variables in the VARS list.
(defun inherit-constraints (vars from-var constraints target)
(do-conset-elements (con constraints)
;; Constant substitution is controversial.
(unless (constant-p (constraint-y con))
(dolist (var vars)
(let ((eq-x (eq from-var (constraint-x con)))
(eq-y (eq from-var (constraint-y con))))
(when (or (and eq-x (not (lvar-p (constraint-y con))))
eq-y)
(conset-adjoin (find-or-create-constraint
(constraint-kind con)
(if eq-x var (constraint-x con))
(if eq-y var (constraint-y con))
(constraint-not-p con))
target)))))))
;; Add an (EQL LAMBDA-VAR LAMBDA-VAR) constraint on VAR1 and VAR2 and
;; inherit each other's constraints.
(defun add-eql-var-var-constraint (var1 var2 constraints
&optional (target constraints))
(let ((con (find-or-create-constraint 'eql var1 var2 nil)))
(when (conset-adjoin con target)
(collect ((eql1) (eql2))
(do-eql-vars (var1 (var1 constraints))
(eql1 var1))
(do-eql-vars (var2 (var2 constraints))
(eql2 var2))
(inherit-constraints (eql1) var2 constraints target)
(inherit-constraints (eql2) var1 constraints target))
t)))
;; Add an (EQL LAMBDA-VAR LAMBDA-VAR) constraint on VAR and LVAR's
;; LAMBDA-VAR if possible.
(defun maybe-add-eql-var-var-constraint (var lvar constraints
&optional (target constraints))
(declare (type lambda-var var) (type lvar lvar))
(let ((lambda-var (ok-lvar-lambda-var lvar constraints)))
(when lambda-var
(add-eql-var-var-constraint var lambda-var constraints target))))
;;; Local propagation
;;; -- [TODO: For any LAMBDA-VAR ref with a type check, add that
;;; constraint.]
;;; -- For any LAMBDA-VAR set, delete all constraints on that var; add
;;; a type constraint based on the new value type.
(declaim (ftype (function (cblock conset boolean)
conset)
constraint-propagate-in-block))
(defun constraint-propagate-in-block (block gen preprocess-refs-p)
(do-nodes (node lvar block)
(typecase node
(bind
(let ((fun (bind-lambda node)))
(when (eq (functional-kind fun) :let)
(loop with call = (lvar-dest (node-lvar (first (lambda-refs fun))))
for var in (lambda-vars fun)
and val in (combination-args call)
when (and val (lambda-var-constraints var))
do (let* ((type (lvar-type val))
(con (find-or-create-constraint 'typep var type
nil)))
(conset-adjoin con gen))
(maybe-add-eql-var-var-constraint var val gen)))))
(ref
(when (ok-ref-lambda-var node)
(maybe-add-eql-var-lvar-constraint node gen)
(when preprocess-refs-p
(let* ((var (ref-leaf node))
(con (lambda-var-constraints var)))
(constrain-ref-type node con gen)))))
(cast
(let ((lvar (cast-value node)))
(let ((var (ok-lvar-lambda-var lvar gen)))
(when var
(let ((atype (single-value-type (cast-derived-type node)))) ;FIXME
(do-eql-vars (var (var gen))
(let ((con (find-or-create-constraint 'typep var atype nil)))
(conset-adjoin con gen))))))))
(cset
(binding* ((var (set-var node))
(nil (lambda-var-p var) :exit-if-null)
(cons (lambda-var-constraints var) :exit-if-null))
(conset-difference gen cons)
(let* ((type (single-value-type (node-derived-type node)))
(con (find-or-create-constraint 'typep var type nil)))
(conset-adjoin con gen))
(maybe-add-eql-var-var-constraint var (set-value node) gen)))))
gen)
(defun constraint-propagate-if (block gen)
(let ((node (block-last block)))
(when (if-p node)
(let ((use (lvar-uses (if-test node))))
(when (node-p use)
(add-test-constraints use node gen))))))
;;; Starting from IN compute OUT and (consequent/alternative
;;; constraints if the block ends with and IF). Return the list of
;;; successors that may need to be recomputed.
(defun find-block-type-constraints (block final-pass-p)
(declare (type cblock block))
(let ((gen (constraint-propagate-in-block
block
(if final-pass-p
(block-in block)
(copy-conset (block-in block)))
final-pass-p)))
(setf (block-gen block) gen)
(multiple-value-bind (consequent-constraints alternative-constraints)
(constraint-propagate-if block gen)
(if consequent-constraints
(let* ((node (block-last block))
(old-consequent-constraints (if-consequent-constraints node))
(old-alternative-constraints (if-alternative-constraints node))
(succ ()))
;; Add the consequent and alternative constraints to GEN.
(cond ((conset-empty consequent-constraints)
(setf (if-consequent-constraints node) gen)
(setf (if-alternative-constraints node) gen))
(t
(setf (if-consequent-constraints node) (copy-conset gen))
(conset-union (if-consequent-constraints node)
consequent-constraints)
(setf (if-alternative-constraints node) gen)
(conset-union (if-alternative-constraints node)
alternative-constraints)))
;; Has the consequent been changed?
(unless (and old-consequent-constraints
(conset= (if-consequent-constraints node)
old-consequent-constraints))
(push (if-consequent node) succ))
;; Has the alternative been changed?
(unless (and old-alternative-constraints
(conset= (if-alternative-constraints node)
old-alternative-constraints))
(push (if-alternative node) succ))
succ)
;; There is no IF.
(unless (and (block-out block)
(conset= gen (block-out block)))
(setf (block-out block) gen)
(block-succ block))))))
;;; Deliver the results of constraint propagation to REFs in BLOCK.
;;; During this pass, we also do local constraint propagation by
;;; adding in constraints as we see them during the pass through the
;;; block.
(defun use-result-constraints (block)
(declare (type cblock block))
(constraint-propagate-in-block block (block-in block) t))
;;; Give an empty constraints set to any var that doesn't have one and
;;; isn't a set closure var. Since a var that we previously rejected
;;; looks identical to one that is new, so we optimistically keep
;;; hoping that vars stop being closed over or lose their sets.
(defun init-var-constraints (component)
(declare (type component component))
(dolist (fun (component-lambdas component))
(flet ((frob (x)
(dolist (var (lambda-vars x))
(unless (lambda-var-constraints var)
(when (or (null (lambda-var-sets var))
(not (closure-var-p var)))
(setf (lambda-var-constraints var) (make-conset)))))))
(frob fun)
(dolist (let (lambda-lets fun))
(frob let)))))
;;; Return the constraints that flow from PRED to SUCC. This is
;;; BLOCK-OUT unless PRED ends with an IF and test constraints were
;;; added.
(defun block-out-for-successor (pred succ)
(declare (type cblock pred succ))
(let ((last (block-last pred)))
(or (when (if-p last)
(cond ((eq succ (if-consequent last))
(if-consequent-constraints last))
((eq succ (if-alternative last))
(if-alternative-constraints last))))
(block-out pred))))
(defun compute-block-in (block)
(let ((in nil))
(dolist (pred (block-pred block))
;; If OUT has not been calculated, assume it to be the universal
;; set.
(let ((out (block-out-for-successor pred block)))
(when out
(if in
(conset-intersection in out)
(setq in (copy-conset out))))))
(or in (make-conset))))
(defun update-block-in (block)
(let ((in (compute-block-in block)))
(cond ((and (block-in block) (conset= in (block-in block)))
nil)
(t
(setf (block-in block) in)))))
;;; Return two lists: one of blocks that precede all loops and
;;; therefore require only one constraint propagation pass and the
;;; rest. This implementation does not find all such blocks.
;;;
;;; A more complete implementation would be:
;;;
;;; (do-blocks (block component)
;;; (if (every #'(lambda (pred)
;;; (or (member pred leading-blocks)
;;; (eq pred head)))
;;; (block-pred block))
;;; (push block leading-blocks)
;;; (push block rest-of-blocks)))
;;;
;;; Trailing blocks that succeed all loops could be found and handled
;;; similarly. In practice though, these more complex solutions are
;;; slightly worse performancewise.
(defun leading-component-blocks (component)
(declare (type component component))
(flet ((loopy-p (block)
(let ((n (block-number block)))
(dolist (pred (block-pred block))
(unless (< n (block-number pred))
(return t))))))
(let ((leading-blocks ())
(rest-of-blocks ())
(seen-loop-p ()))
(do-blocks (block component)
(when (and (not seen-loop-p) (loopy-p block))
(setq seen-loop-p t))
(if seen-loop-p
(push block rest-of-blocks)
(push block leading-blocks)))
(values (nreverse leading-blocks) (nreverse rest-of-blocks)))))
;;; Append OBJ to the end of LIST as if by NCONC but only if it is not
;;; a member already.
(defun nconc-new (obj list)
(do ((x list (cdr x))
(prev nil x))
((endp x) (if prev
(progn
(setf (cdr prev) (list obj))
list)
(list obj)))
(when (eql (car x) obj)
(return-from nconc-new list))))
(defun find-and-propagate-constraints (component)
(let ((blocks-to-process ()))
(flet ((enqueue (blocks)
(dolist (block blocks)
(setq blocks-to-process (nconc-new block blocks-to-process)))))
(multiple-value-bind (leading-blocks rest-of-blocks)
(leading-component-blocks component)
;; Update every block once to account for changes in the
;; IR1. The constraints of the lead blocks cannot be changed
;; after the first pass so we might as well use them and skip
;; USE-RESULT-CONSTRAINTS later.
(dolist (block leading-blocks)
(setf (block-in block) (compute-block-in block))
(find-block-type-constraints block t))
(setq blocks-to-process (copy-list rest-of-blocks))
;; The rest of the blocks.
(dolist (block rest-of-blocks)
(aver (eq block (pop blocks-to-process)))
(setf (block-in block) (compute-block-in block))
(enqueue (find-block-type-constraints block nil)))
;; Propagate constraints
(loop for block = (pop blocks-to-process)
while block do
(unless (eq block (component-tail component))
(when (update-block-in block)
(enqueue (find-block-type-constraints block nil)))))
rest-of-blocks))))
(defun constraint-propagate (component)
(declare (type component component))
(init-var-constraints component)
(unless (block-out (component-head component))
(setf (block-out (component-head component)) (make-conset)))
(dolist (block (find-and-propagate-constraints component))
(unless (block-delete-p block)
(use-result-constraints block)))
(values))