0.8.9.6.netbsd.2:

[sbcl.git] / src / compiler / checkgen.lisp

diff --git a/src/compiler/checkgen.lisp b/src/compiler/checkgen.lisp
index 8b43ae3..2f9f907 100644 (file)
--- a/src/compiler/checkgen.lisp
+++ b/src/compiler/checkgen.lisp
@@ -43,7 +43,11 @@
 ;;; templates in the VM definition.
 (defun type-test-cost (type)
   (declare (type ctype type))
 ;;; templates in the VM definition.
 (defun type-test-cost (type)
   (declare (type ctype type))

-  (or (let ((check (type-check-template type)))
+  (or (when (eq type *universal-type*)
+        0)
+      (when (eq type *empty-type*)
+        0)
+      (let ((check (type-check-template type)))

        (if check
            (template-cost check)
            (let ((found (cdr (assoc type *backend-type-predicates*
        (if check
            (template-cost check)
            (let ((found (cdr (assoc type *backend-type-predicates*

@@ -103,35 +107,28 @@
 (defun weaken-values-type (type)
   (declare (type ctype type))
   (cond ((eq type *wild-type*) type)
 (defun weaken-values-type (type)
   (declare (type ctype type))
   (cond ((eq type *wild-type*) type)

-        ((values-type-p type)
+        ((not (values-type-p type))
+         (weaken-type type))
+        (t

          (make-values-type :required (mapcar #'weaken-type
                                              (values-type-required type))
                            :optional (mapcar #'weaken-type
                                              (values-type-optional type))
                            :rest (acond ((values-type-rest type)
          (make-values-type :required (mapcar #'weaken-type
                                              (values-type-required type))
                            :optional (mapcar #'weaken-type
                                              (values-type-optional type))
                            :rest (acond ((values-type-rest type)

-                                         (weaken-type it))
-                                        ((values-type-keyp type)
-                                         *universal-type*))))
-        (t (weaken-type type))))
+                                         (weaken-type it)))))))

 \f
 ;;;; checking strategy determination
 
 ;;; Return the type we should test for when we really want to check
 \f
 ;;;; checking strategy determination
 
 ;;; Return the type we should test for when we really want to check

-;;; for TYPE. If speed, space or compilation speed is more important
-;;; than safety, then we return a weaker type if it is easier to
-;;; check. First we try the defined type weakenings, then look for any
-;;; predicate that is cheaper.
+;;; for TYPE. If type checking policy is "fast", then we return a
+;;; weaker type if it is easier to check. First we try the defined
+;;; type weakenings, then look for any predicate that is cheaper.

 (defun maybe-weaken-check (type policy)
   (declare (type ctype type))
 (defun maybe-weaken-check (type policy)
   (declare (type ctype type))

-  (cond ((policy policy (zerop safety))
-         *wild-type*)
-        ((policy policy
-                (and (<= speed safety)
-                     (<= space safety)
-                     (<= compilation-speed safety)))
-        type)
-       (t
-        (weaken-values-type type))))
+  (ecase (policy policy type-check)
+    (0 *wild-type*)
+    (2 (weaken-values-type type))
+    (3 type)))

 
 ;;; This is like VALUES-TYPES, only we mash any complex function types
 ;;; to FUNCTION.
 
 ;;; This is like VALUES-TYPES, only we mash any complex function types
 ;;; to FUNCTION.

@@ -148,9 +145,9 @@
 ;;; Switch to disable check complementing, for evaluation.
 (defvar *complement-type-checks* t)
 
 ;;; Switch to disable check complementing, for evaluation.
 (defvar *complement-type-checks* t)
 

-;;; CONT is a continuation we are doing a type check on and TYPES is a
-;;; list of types that we are checking its values against. If we have
-;;; proven that CONT generates a fixed number of values, then for each
+;;; LVAR is an lvar we are doing a type check on and TYPES is a list
+;;; of types that we are checking its values against. If we have
+;;; proven that LVAR generates a fixed number of values, then for each

 ;;; value, we check whether it is cheaper to then difference between
 ;;; the proven type and the corresponding type in TYPES. If so, we opt
 ;;; for a :HAIRY check with that test negated. Otherwise, we try to do
 ;;; value, we check whether it is cheaper to then difference between
 ;;; the proven type and the corresponding type in TYPES. If so, we opt
 ;;; for a :HAIRY check with that test negated. Otherwise, we try to do

@@ -167,50 +164,60 @@
 ;;; FIXME: I don't quite understand this, but it looks as though
 ;;; that means type checks are weakened when SPEED=3 regardless of
 ;;; the SAFETY level, which is not the right thing to do.
 ;;; FIXME: I don't quite understand this, but it looks as though
 ;;; that means type checks are weakened when SPEED=3 regardless of
 ;;; the SAFETY level, which is not the right thing to do.

-(defun maybe-negate-check (cont types original-types force-hairy)
-  (declare (type continuation cont) (list types))
-  (multiple-value-bind (ptypes count)
-      (no-fun-values-types (continuation-proven-type cont))
-    (if (eq count :unknown)
-        (if (and (every #'type-check-template types) (not force-hairy))
-            (values :simple types)
-            (values :hairy (mapcar (lambda (x) (list nil x x)) types)))
-        (let ((res (mapcar (lambda (p c a)
-                             (let ((diff (type-difference p c)))
-                               (if (and diff
-                                        (< (type-test-cost diff)
-                                           (type-test-cost c))
-                                        *complement-type-checks*)
-                                   (list t diff a)
-                                   (list nil c a))))
-                           ptypes types original-types)))
-          (cond ((or force-hairy (find-if #'first res))
-                 (values :hairy res))
-                ((every #'type-check-template types)
-                 (values :simple types))
-                (t
-                 (values :hairy res)))))))
-
-;;; Determines whether CONT's assertion is:
+(defun maybe-negate-check (lvar types original-types force-hairy n-required)
+  (declare (type lvar lvar) (list types original-types))
+  (let ((ptypes (values-type-out (lvar-derived-type lvar) (length types))))
+    (multiple-value-bind (hairy-res simple-res)
+        (loop for p in ptypes
+              and c in types
+              and a in original-types
+              and i from 0
+              for cc = (if (>= i n-required)
+                           (type-union c (specifier-type 'null))
+                           c)
+              for diff = (type-difference p cc)
+              collect (if (and diff
+                               (< (type-test-cost diff)
+                                  (type-test-cost cc))
+                               *complement-type-checks*)
+                          (list t diff a)
+                          (list nil cc a))
+              into hairy-res
+              collect cc into simple-res
+              finally (return (values hairy-res simple-res)))
+      (cond ((or force-hairy (find-if #'first hairy-res))
+             (values :hairy hairy-res))
+            ((every #'type-check-template simple-res)
+             (values :simple simple-res))
+            (t
+             (values :hairy hairy-res))))))
+
+;;; Determines whether CAST's assertion is:

 ;;;  -- checkable by the back end (:SIMPLE), or
 ;;;  -- not checkable by the back end, but checkable via an explicit 
 ;;;     test in type check conversion (:HAIRY), or
 ;;;  -- not reasonably checkable at all (:TOO-HAIRY).
 ;;;
 ;;;  -- checkable by the back end (:SIMPLE), or
 ;;;  -- not checkable by the back end, but checkable via an explicit 
 ;;;     test in type check conversion (:HAIRY), or
 ;;;  -- not reasonably checkable at all (:TOO-HAIRY).
 ;;;

-;;; A type is checkable if it either represents a fixed number of
-;;; values (as determined by VALUES-TYPES), or it is the assertion for
-;;; an MV-BIND. A type is simply checkable if all the type assertions
-;;; have a TYPE-CHECK-TEMPLATE. In this :SIMPLE case, the second value
-;;; is a list of the type restrictions specified for the leading
-;;; positional values.
+;;; We may check only fixed number of values; in any case the number
+;;; of generated values is trusted. If we know the number of produced
+;;; values, all of them are checked; otherwise if we know the number
+;;; of consumed -- only they are checked; otherwise the check is not
+;;; performed.
+;;;
+;;; A type is simply checkable if all the type assertions have a
+;;; TYPE-CHECK-TEMPLATE. In this :SIMPLE case, the second value is a
+;;; list of the type restrictions specified for the leading positional
+;;; values.

 ;;;
 ;;;

-;;; We force a check to be hairy even when there are fixed values if
-;;; we are in a context where we may be forced to use the unknown
-;;; values convention anyway. This is because IR2tran can't generate
-;;; type checks for unknown values continuations but people could
-;;; still be depending on the check being done. We only care about
-;;; EXIT and RETURN (not MV-COMBINATION) since these are the only
-;;; contexts where the ultimate values receiver
+;;; Old comment:
+;;;
+;;;    We force a check to be hairy even when there are fixed values
+;;;    if we are in a context where we may be forced to use the
+;;;    unknown values convention anyway. This is because IR2tran can't
+;;;    generate type checks for unknown values lvars but people could
+;;;    still be depending on the check being done. We only care about
+;;;    EXIT and RETURN (not MV-COMBINATION) since these are the only
+;;;    contexts where the ultimate values receiver

 ;;;
 ;;; In the :HAIRY case, the second value is a list of triples of
 ;;; the form:
 ;;;
 ;;; In the :HAIRY case, the second value is a list of triples of
 ;;; the form:

@@ -218,82 +225,108 @@
 ;;;
 ;;; If true, the NOT-P flag indicates a test that the corresponding
 ;;; value is *not* of the specified TYPE. ORIGINAL-TYPE is the type
 ;;;
 ;;; If true, the NOT-P flag indicates a test that the corresponding
 ;;; value is *not* of the specified TYPE. ORIGINAL-TYPE is the type

-;;; asserted on this value in the continuation, for use in error
+;;; asserted on this value in the lvar, for use in error

 ;;; messages. When NOT-P is true, this will be different from TYPE.
 ;;;
 ;;; messages. When NOT-P is true, this will be different from TYPE.
 ;;;

-;;; This allows us to take what has been proven about CONT's type into
-;;; consideration. If it is cheaper to test for the difference between
-;;; the derived type and the asserted type, then we check for the
-;;; negation of this type instead.
-(defun continuation-check-types (cont force-hairy)
-  (declare (type continuation cont))
-  (let ((ctype (continuation-type-to-check cont))
-        (atype (continuation-asserted-type cont))
-       (dest (continuation-dest cont)))
+;;; This allows us to take what has been proven about CAST's argument
+;;; type into consideration. If it is cheaper to test for the
+;;; difference between the derived type and the asserted type, then we
+;;; check for the negation of this type instead.
+(defun cast-check-types (cast force-hairy)
+  (declare (type cast cast))
+  (let* ((ctype (coerce-to-values (cast-type-to-check cast)))
+         (atype (coerce-to-values (cast-asserted-type cast)))
+         (dtype (node-derived-type cast))
+         (value (cast-value cast))
+         (lvar (node-lvar cast))
+         (dest (and lvar (lvar-dest lvar)))
+         (n-consumed (cond ((not lvar)
+                            nil)
+                           ((lvar-single-value-p lvar)
+                            1)
+                           ((and (mv-combination-p dest)
+                                 (eq (mv-combination-kind dest) :local))
+                            (let ((fun-ref (lvar-use (mv-combination-fun dest))))
+                              (length (lambda-vars (ref-leaf fun-ref)))))))
+         (n-required (length (values-type-required dtype))))

     (aver (not (eq ctype *wild-type*)))
     (aver (not (eq ctype *wild-type*)))

-    (multiple-value-bind (ctypes count) (no-fun-values-types ctype)
-      (multiple-value-bind (atypes acount) (no-fun-values-types ctype)
-        (aver (eq count acount))
-        (cond ((not (eq count :unknown))
-               (if (or (exit-p dest)
-                       (and (return-p dest)
-                            (multiple-value-bind (ignore count)
-                                (values-types (return-result-type dest))
-                              (declare (ignore ignore))
-                              (eq count :unknown))))
-                   (maybe-negate-check cont ctypes atypes t)
-                   (maybe-negate-check cont ctypes atypes force-hairy)))
-              ((and (mv-combination-p dest)
-                    (eq (basic-combination-kind dest) :local))
-               (aver (values-type-p ctype))
-               (maybe-negate-check cont
-                                   (args-type-optional ctype)
-                                   (args-type-optional atype)
-                                   force-hairy))
-              (t
-               (values :too-hairy nil)))))))
+    (cond ((and (null (values-type-optional dtype))
+                (not (values-type-rest dtype)))
+           ;; we [almost] know how many values are produced
+           (maybe-negate-check value
+                               (values-type-out ctype n-required)
+                               (values-type-out atype n-required)
+                               ;; backend checks only consumed values
+                               (not (eql n-required n-consumed))
+                               n-required))
+          ((lvar-single-value-p lvar)
+           ;; exactly one value is consumed
+           (principal-lvar-single-valuify lvar)
+           (let ((creq (car (args-type-required ctype))))
+             (multiple-value-setq (ctype atype)
+               (if creq
+                   (values creq (car (args-type-required atype)))
+                   (values (car (args-type-optional ctype))
+                           (car (args-type-optional atype)))))
+             (maybe-negate-check value
+                                 (list ctype) (list atype)
+                                 force-hairy
+                                 n-required)))
+          ((and (mv-combination-p dest)
+                (eq (mv-combination-kind dest) :local))
+           ;; we know the number of consumed values
+           (maybe-negate-check value
+                               (adjust-list (values-type-types ctype)
+                                            n-consumed
+                                            *universal-type*)
+                               (adjust-list (values-type-types atype)
+                                            n-consumed
+                                            *universal-type*)
+                               force-hairy
+                               n-required))
+          (t
+           (values :too-hairy nil)))))

 
 ;;; Do we want to do a type check?
 
 ;;; Do we want to do a type check?

-(defun worth-type-check-p (cont)
-  (let ((dest (continuation-dest cont)))
-    (not (or (values-subtypep (continuation-proven-type cont)
-                              (continuation-type-to-check cont))
-             (and (combination-p dest)
-                  (eq (combination-kind dest) :full)
-                  ;; The theory is that the type assertion is from a
-                  ;; declaration in (or on) the callee, so the callee
-                  ;; should be able to do the check. We want to let
-                  ;; the callee do the check, because it is possible
-                  ;; that by the time of call that declaration will be
-                  ;; changed and we do not want to make people
-                  ;; recompile all calls to a function when they were
-                  ;; originally compiled with a bad declaration. (See
-                  ;; also bug 35.)
-                  (values-subtypep (continuation-externally-checkable-type cont)
-                                   (continuation-type-to-check cont)))
-             (and (mv-combination-p dest) ; bug 220
-                  (eq (mv-combination-kind dest) :full))))))
-
-;;; Return true if CONT is a continuation whose type the back end is
+(defun cast-externally-checkable-p (cast)
+  (declare (type cast cast))
+  (let* ((lvar (node-lvar cast))
+         (dest (and lvar (lvar-dest lvar))))
+    (and (combination-p dest)
+         ;; The theory is that the type assertion is from a
+         ;; declaration in (or on) the callee, so the callee should be
+         ;; able to do the check. We want to let the callee do the
+         ;; check, because it is possible that by the time of call
+         ;; that declaration will be changed and we do not want to
+         ;; make people recompile all calls to a function when they
+         ;; were originally compiled with a bad declaration. (See also
+         ;; bug 35.)
+         (or (immediately-used-p lvar cast)
+             (binding* ((ctran (node-next cast) :exit-if-null)
+                        (next (ctran-next ctran)))
+               (and (cast-p next)
+                    (eq (node-dest next) dest)
+                    (eq (cast-type-check next) :external))))
+         (values-subtypep (lvar-externally-checkable-type lvar)
+                          (cast-type-to-check cast)))))
+
+;;; Return true if CAST's value is an lvar whose type the back end is

 ;;; likely to want to check. Since we don't know what template the
 ;;; back end is going to choose to implement the continuation's DEST,
 ;;; we use a heuristic. We always return T unless:
 ;;;  -- nobody uses the value, or
 ;;;  -- safety is totally unimportant, or
 ;;; likely to want to check. Since we don't know what template the
 ;;; back end is going to choose to implement the continuation's DEST,
 ;;; we use a heuristic. We always return T unless:
 ;;;  -- nobody uses the value, or
 ;;;  -- safety is totally unimportant, or

-;;;  -- the continuation is an argument to an unknown function, or
-;;;  -- the continuation is an argument to a known function that has
+;;;  -- the lvar is an argument to an unknown function, or
+;;;  -- the lvar is an argument to a known function that has

 ;;;     no IR2-CONVERT method or :FAST-SAFE templates that are
 ;;;     compatible with the call's type.
 ;;;     no IR2-CONVERT method or :FAST-SAFE templates that are
 ;;;     compatible with the call's type.

-;;;
-;;; We must only return NIL when it is *certain* that a check will not
-;;; be done, since if we pass up this chance to do the check, it will
-;;; be too late. The penalty for being too conservative is duplicated
-;;; type checks. The penalty for erring by being too speculative is
-;;; much nastier, e.g. falling through without ever being able to find
-;;; an appropriate VOP.
-(defun probable-type-check-p (cont)
-  (declare (type continuation cont))
-  (let ((dest (continuation-dest cont)))
+(defun probable-type-check-p (cast)
+  (declare (type cast cast))
+  (let* ((lvar (node-lvar cast))
+         (dest (and lvar (lvar-dest lvar))))
+    (cond ((not dest) nil)
+          (t t))
+    #+nil

     (cond ((or (not dest)
               (policy dest (zerop safety)))
           nil)
     (cond ((or (not dest)
               (policy dest (zerop safety)))
           nil)

@@ -321,164 +354,104 @@
                          (when (or val (not win)) (return t)))))))))
          (t t))))
 
                          (when (or val (not win)) (return t)))))))))
          (t t))))
 

-;;; Return a form that we can convert to do a hairy type check of the
-;;; specified TYPES. TYPES is a list of the format returned by
-;;; CONTINUATION-CHECK-TYPES in the :HAIRY case. In place of the
-;;; actual value(s) we are to check, we use 'DUMMY. This constant
-;;; reference is later replaced with the actual values continuation.
+;;; Return a lambda form that we can convert to do a hairy type check
+;;; of the specified TYPES. TYPES is a list of the format returned by
+;;; LVAR-CHECK-TYPES in the :HAIRY case.

 ;;;
 ;;; Note that we don't attempt to check for required values being
 ;;; unsupplied. Such checking is impossible to efficiently do at the
 ;;; source level because our fixed-values conventions are optimized
 ;;; for the common MV-BIND case.
 ;;;
 ;;; Note that we don't attempt to check for required values being
 ;;; unsupplied. Such checking is impossible to efficiently do at the
 ;;; source level because our fixed-values conventions are optimized
 ;;; for the common MV-BIND case.

-;;;
-;;; We can always use MULTIPLE-VALUE-BIND, since the macro is clever
-;;; about binding a single variable.

 (defun make-type-check-form (types)
   (let ((temps (make-gensym-list (length types))))
 (defun make-type-check-form (types)
   (let ((temps (make-gensym-list (length types))))

-    `(multiple-value-bind ,temps 'dummy
+    `(multiple-value-bind ,temps
+         'dummy

        ,@(mapcar (lambda (temp type)
        ,@(mapcar (lambda (temp type)

-                  (let* ((spec
-                          (let ((*unparse-fun-type-simplify* t))
-                            (type-specifier (second type))))
-                         (test (if (first type) `(not ,spec) spec)))
-                    `(unless (typep ,temp ',test)
-                       (%type-check-error
-                        ,temp
-                        ',(type-specifier (third type))))))
-                temps
-                types)
+                   (let* ((spec
+                           (let ((*unparse-fun-type-simplify* t))
+                             (type-specifier (second type))))
+                          (test (if (first type) `(not ,spec) spec)))
+                     `(unless (typep ,temp ',test)
+                        (%type-check-error
+                         ,temp
+                         ',(type-specifier (third type))))))
+                 temps
+                 types)

        (values ,@temps))))
 
        (values ,@temps))))
 

-;;; Splice in explicit type check code immediately before the node
-;;; which is CONT's DEST. This code receives the value(s) that were
-;;; being passed to CONT, checks the type(s) of the value(s), then
-;;; passes them on to CONT.
-(defun convert-type-check (cont types)
-  (declare (type continuation cont) (type list types))
-  (with-ir1-environment-from-node (continuation-dest cont)
-
-    ;; Ensuring that CONT starts a block lets us freely manipulate its uses.
-    (ensure-block-start cont)
-
-    ;; Make a new continuation and move CONT's uses to it.
-    (let* ((new-start (make-continuation))
-          (dest (continuation-dest cont))
-          (prev (node-prev dest)))
-      (continuation-starts-block new-start)
-      (substitute-continuation-uses new-start cont)
-
-      ;; Setting TYPE-CHECK in CONT to :DELETED indicates that the
-      ;; check has been done.
-      (setf (continuation-%type-check cont) :deleted)
-
-      ;; Make the DEST node start its block so that we can splice in
-      ;; the type check code.
-      (when (continuation-use prev)
-       (node-ends-block (continuation-use prev)))
-
-      (let* ((prev-block (continuation-block prev))
-            (new-block (continuation-block new-start))
-            (dummy (make-continuation)))
-
-       ;; Splice in the new block before DEST, giving the new block
-       ;; all of DEST's predecessors.
-       (dolist (block (block-pred prev-block))
-         (change-block-successor block prev-block new-block))
-
-       ;; Convert the check form, using the new block start as START
-       ;; and a dummy continuation as CONT.
-       (ir1-convert new-start dummy (make-type-check-form types))
-
-       ;; TO DO: Why should this be true? -- WHN 19990601
-       (aver (eq (continuation-block dummy) new-block))
-
-       ;; KLUDGE: Comments at the head of this function in CMU CL
-       ;; said that somewhere in here we
-       ;;   Set the new block's start and end cleanups to the *start*
-       ;;   cleanup of PREV's block. This overrides the incorrect
-       ;;   default from WITH-IR1-ENVIRONMENT-FROM-NODE.
-       ;; Unfortunately I can't find any code which corresponds to this.
-       ;; Perhaps it was a stale comment? Or perhaps I just don't
-       ;; understand.. -- WHN 19990521
-
-               (let ((node (continuation-use dummy)))
-         (setf (block-last new-block) node)
-         ;; Change the use to a use of CONT. (We need to use the
-         ;; dummy continuation to get the control transfer right,
-         ;; because we want to go to PREV's block, not CONT's.)
-         (delete-continuation-use node)
-         (add-continuation-use node cont))
-       ;; Link the new block to PREV's block.
-       (link-blocks new-block prev-block))
-
-      ;; MAKE-TYPE-CHECK-FORM generated a form which checked the type
-      ;; of 'DUMMY, not a real form. At this point we convert to the
-      ;; real form by finding 'DUMMY and overwriting it with the new
-      ;; continuation. (We can find 'DUMMY because no LET conversion
-      ;; has been done yet.) The [mv-]combination code from the
-      ;; mv-bind in the check form will be the use of the new check
-      ;; continuation. We substitute for the first argument of this
-      ;; node.
-      (let* ((node (continuation-use cont))
-            (args (basic-combination-args node))
-            (victim (first args)))
-       (aver (and (= (length args) 1)
-                    (eq (constant-value
-                         (ref-leaf
-                          (continuation-use victim)))
-                        'dummy)))
-       (substitute-continuation new-start victim)))
-
-    ;; Invoking local call analysis converts this call to a LET.
-    (locall-analyze-component *current-component*))
+;;; Splice in explicit type check code immediately before CAST. This
+;;; code receives the value(s) that were being passed to CAST-VALUE,
+;;; checks the type(s) of the value(s), then passes them further.
+(defun convert-type-check (cast types)
+  (declare (type cast cast) (type list types))
+  (let ((value (cast-value cast))
+        (length (length types)))
+    (filter-lvar value (make-type-check-form types))
+    (reoptimize-lvar (cast-value cast))
+    (setf (cast-type-to-check cast) *wild-type*)
+    (setf (cast-%type-check cast) nil)
+    (let* ((atype (cast-asserted-type cast))
+           (atype (cond ((not (values-type-p atype))
+                        atype)
+                       ((= length 1)
+                         (single-value-type atype))
+                        (t
+                        (make-values-type
+                          :required (values-type-out atype length)))))
+           (dtype (node-derived-type cast))
+           (dtype (make-values-type
+                   :required (values-type-out dtype length))))
+      (setf (cast-asserted-type cast) atype)
+      (setf (node-derived-type cast) dtype)))

 
   (values))
 
 
   (values))
 

-;;; Emit a type warning for NODE. If the value of NODE is being used
-;;; for a variable binding, we figure out which one for source
-;;; context. If the value is a constant, we print it specially. We
-;;; ignore nodes whose type is NIL, since they are supposed to never
-;;; return.
-(defun emit-type-warning (node)
-  (declare (type node node))
-  (let* ((*compiler-error-context* node)
-        (cont (node-cont node))
-        (atype-spec (type-specifier (continuation-asserted-type cont)))
-        (dtype (node-derived-type node))
-        (dest (continuation-dest cont))
-        (what (when (and (combination-p dest)
-                         (eq (combination-kind dest) :local))
-                (let ((lambda (combination-lambda dest))
-                      (pos (position-or-lose cont (combination-args dest))))
-                  (format nil "~:[A possible~;The~] binding of ~S"
-                          (and (continuation-use cont)
-                               (eq (functional-kind lambda) :let))
-                          (leaf-source-name (elt (lambda-vars lambda)
-                                                 pos)))))))
-    (cond ((eq dtype *empty-type*))
-         ((and (ref-p node) (constant-p (ref-leaf node)))
-          (compiler-warn "~:[This~;~:*~A~] is not a ~<~%~9T~:;~S:~>~%  ~S"
-                         what atype-spec (constant-value (ref-leaf node))))
-         (t
-          (compiler-warn
-           "~:[Result~;~:*~A~] is a ~S, ~<~%~9T~:;not a ~S.~>"
-           what (type-specifier dtype) atype-spec))))
+;;; Check all possible arguments of CAST and emit type warnings for
+;;; those with type errors. If the value of USE is being used for a
+;;; variable binding, we figure out which one for source context. If
+;;; the value is a constant, we print it specially.
+(defun cast-check-uses (cast)
+  (declare (type cast cast))
+  (let* ((lvar (node-lvar cast))
+         (dest (and lvar (lvar-dest lvar)))
+         (value (cast-value cast))
+         (atype (cast-asserted-type cast)))
+    (do-uses (use value)
+      (let ((dtype (node-derived-type use)))
+        (unless (values-types-equal-or-intersect dtype atype)
+          (let* ((*compiler-error-context* use)
+                 (atype-spec (type-specifier atype))
+                 (what (when (and (combination-p dest)
+                                  (eq (combination-kind dest) :local))
+                         (let ((lambda (combination-lambda dest))
+                               (pos (position-or-lose
+                                     lvar (combination-args dest))))
+                           (format nil "~:[A possible~;The~] binding of ~S"
+                                   (and (lvar-has-single-use-p lvar)
+                                        (eq (functional-kind lambda) :let))
+                                   (leaf-source-name (elt (lambda-vars lambda)
+                                                          pos)))))))
+            (cond ((and (ref-p use) (constant-p (ref-leaf use)))
+                   (compiler-warn "~:[This~;~:*~A~] is not a ~<~%~9T~:;~S:~>~%  ~S"
+                                  what atype-spec (constant-value (ref-leaf use))))
+                  (t
+                   (compiler-warn
+                    "~:[Result~;~:*~A~] is a ~S, ~<~%~9T~:;not a ~S.~>"
+                    what (type-specifier dtype) atype-spec))))))))

   (values))
 
 ;;; Loop over all blocks in COMPONENT that have TYPE-CHECK set,
   (values))
 
 ;;; Loop over all blocks in COMPONENT that have TYPE-CHECK set,

-;;; looking for continuations with TYPE-CHECK T. We do two mostly
-;;; unrelated things: detect compile-time type errors and determine if
-;;; and how to do run-time type checks.
+;;; looking for CASTs with TYPE-CHECK T. We do two mostly unrelated
+;;; things: detect compile-time type errors and determine if and how
+;;; to do run-time type checks.

 ;;;
 ;;;

-;;; If there is a compile-time type error, then we mark the
-;;; continuation and emit a warning if appropriate. This part loops
-;;; over all the uses of the continuation, since after we convert the
-;;; check, the :DELETED kind will inhibit warnings about the types of
-;;; other uses.
+;;; If there is a compile-time type error, then we mark the CAST and
+;;; emit a warning if appropriate. This part loops over all the uses
+;;; of the continuation, since after we convert the check, the
+;;; :DELETED kind will inhibit warnings about the types of other uses.

 ;;;
 ;;;

-;;; If a continuation is too complex to be checked by the back end, or
-;;; is better checked with explicit code, then convert to an explicit
+;;; If the cast is too complex to be checked by the back end, or is
+;;; better checked with explicit code, then convert to an explicit

 ;;; test. Assertions that can checked by the back end are passed
 ;;; through. Assertions that can't be tested are flamed about and
 ;;; marked as not needing to be checked.
 ;;; test. Assertions that can checked by the back end are passed
 ;;; through. Assertions that can't be tested are flamed about and
 ;;; marked as not needing to be checked.

@@ -496,40 +469,36 @@
 ;;; which may lead to inappropriate template choices due to the
 ;;; modification of argument types.
 (defun generate-type-checks (component)
 ;;; which may lead to inappropriate template choices due to the
 ;;; modification of argument types.
 (defun generate-type-checks (component)

-  (collect ((conts))
+  (collect ((casts))

     (do-blocks (block component)
       (when (block-type-check block)
     (do-blocks (block component)
       (when (block-type-check block)

-       (do-nodes (node cont block)
-         (let ((type-check (continuation-type-check cont)))
-           (unless (member type-check '(nil :deleted))
-             (let ((atype (continuation-asserted-type cont)))
-               (do-uses (use cont)
-                 (unless (values-types-equal-or-intersect
-                          (node-derived-type use) atype)
-                   (unless (policy node (= inhibit-warnings 3))
-                     (emit-type-warning use))))))
-           (when (eq type-check t)
-             (cond ((worth-type-check-p cont)
-                     (conts (cons cont (not (probable-type-check-p cont)))))
-                    ((probable-type-check-p cont)
-                     (setf (continuation-%type-check cont) :deleted))
-                    (t
-                     (setf (continuation-%type-check cont) :no-check))))))
+        ;; CAST-EXTERNALLY-CHECKABLE-P wants the backward pass
+       (do-nodes-backwards (node nil block)
+          (when (and (cast-p node)
+                     (cast-type-check node))
+            (cast-check-uses node)
+            (cond ((cast-externally-checkable-p node)
+                   (setf (cast-%type-check node) :external))
+                  (t
+                   ;; it is possible that NODE was marked :EXTERNAL by
+                   ;; the previous pass
+                   (setf (cast-%type-check node) t)
+                   (casts (cons node (not (probable-type-check-p node))))))))

        (setf (block-type-check block) nil)))
        (setf (block-type-check block) nil)))

-    (dolist (cont (conts))
-      (destructuring-bind (cont . force-hairy) cont
+    (dolist (cast (casts))
+      (destructuring-bind (cast . force-hairy) cast

         (multiple-value-bind (check types)
         (multiple-value-bind (check types)

-            (continuation-check-types cont force-hairy)
+            (cast-check-types cast force-hairy)

           (ecase check
             (:simple)
             (:hairy
           (ecase check
             (:simple)
             (:hairy

-             (convert-type-check cont types))
+             (convert-type-check cast types))

             (:too-hairy
             (:too-hairy

-             (let* ((context (continuation-dest cont))
-                    (*compiler-error-context* context))
-               (when (policy context (>= safety inhibit-warnings))
-                 (compiler-note
+             (let ((*compiler-error-context* cast))
+               (when (policy cast (>= safety inhibit-warnings))
+                 (compiler-notify

                   "type assertion too complex to check:~% ~S."
                   "type assertion too complex to check:~% ~S."

-                  (type-specifier (continuation-asserted-type cont)))))
-             (setf (continuation-%type-check cont) :deleted)))))))
+                  (type-specifier (coerce-to-values (cast-asserted-type cast))))))
+             (setf (cast-type-to-check cast) *wild-type*)
+             (setf (cast-%type-check cast) nil)))))))

   (values))
   (values))