;;;; This file implements the stack analysis phase in the compiler. We
-;;;; do a graph walk to determine which unknown-values continuations
-;;;; are on the stack at each point in the program, and then we insert
+;;;; do a graph walk to determine which unknown-values lvars are on
+;;;; the stack at each point in the program, and then we insert
;;;; cleanup code to pop off unused values.
;;;; This software is part of the SBCL system. See the README file for
(in-package "SB!C")
\f
-;;; Scan through BLOCK looking for uses of :UNKNOWN continuations that
-;;; have their DEST outside of the block. We do some checking to
-;;; verify the invariant that all pushes come after the last pop.
+;;; Scan through BLOCK looking for uses of :UNKNOWN lvars that have
+;;; their DEST outside of the block. We do some checking to verify the
+;;; invariant that all pushes come after the last pop.
(defun find-pushed-lvars (block)
(let* ((2block (block-info block))
(popped (ir2-block-popped 2block))
\f
;;;; annotation graph walk
-;;; Do a backward walk in the flow graph simulating the run-time stack
-;;; of unknown-values continuations and annotating the blocks with the
-;;; result.
-;;;
-;;; BLOCK is the block that is currently being walked and STACK is the
-;;; stack of unknown-values continuations in effect immediately after
-;;; block. We simulate the stack by popping off the unknown-values
-;;; generated by this block (if any) and pushing the continuations for
-;;; values received by this block. (The role of push and pop are
-;;; interchanged because we are doing a backward walk.)
-;;;
-;;; If we run into a values generator whose continuation isn't on
-;;; stack top, then the receiver hasn't yet been reached on any walk
-;;; to this use. In this case, we ignore the push for now, counting on
-;;; Annotate-Dead-Values to clean it up if we discover that it isn't
-;;; reachable at all.
-;;;
-;;; If our final stack isn't empty, then we walk all the predecessor
-;;; blocks that don't have all the continuations that we have on our
-;;; START-STACK on their END-STACK. This is our termination condition
-;;; for the graph walk. We put the test around the recursive call so
-;;; that the initial call to this function will do something even
-;;; though there isn't initially anything on the stack.
-;;;
-;;; We can use the tailp test, since the only time we want to bottom
-;;; out with a non-empty stack is when we intersect with another path
-;;; from the same top level call to this function that has more values
-;;; receivers on that path. When we bottom out in this way, we are
-;;; counting on DISCARD-UNUSED-VALUES doing its thing.
-;;;
-;;; When we do recurse, we check that predecessor's END-STACK is a
-;;; subsequence of our START-STACK. There may be extra stuff on the
-;;; top of our stack because the last path to the predecessor may have
-;;; discarded some values that we use. There may be extra stuff on the
-;;; bottom of our stack because this walk may be from a values
-;;; receiver whose lifetime encloses that of the previous walk.
-;;;
-;;; If a predecessor block is the component head, then it must be the
-;;; case that this is a NLX entry stub. If so, we just stop our walk,
-;;; since the stack at the exit point doesn't have anything to do with
-;;; our stack.
-(defun stack-simulation-walk (block stack)
- (declare (type cblock block) (list stack))
- (let ((2block (block-info block)))
- (setf (ir2-block-end-stack 2block) stack)
- (let ((new-stack stack))
- (dolist (push (reverse (ir2-block-pushed 2block)))
- (if (eq (car new-stack) push)
- (pop new-stack)
- (aver (not (member push new-stack)))))
+;;; Add LVARs from LATE to EARLY; use EQ to check whether EARLY has
+;;; been changed.
+(defun merge-stacks (early late)
+ (declare (type list early late))
+ (cond ((null early) late)
+ ((null late) early)
+ ((tailp early late) late)
+ ((tailp late early) early)
+ ;; FIXME
+ (t (bug "Lexical unwinding of UVL stack is not implemented."))))
- (dolist (pop (reverse (ir2-block-popped 2block)))
- (push pop new-stack))
+;;; Update information on stacks of unknown-values LVARs on the
+;;; boundaries of BLOCK. Return true if the start stack has been
+;;; changed.
+(defun stack-update (block)
+ (declare (type cblock block))
+ (declare (optimize (debug 3)))
+ (let* ((2block (block-info block))
+ (end (ir2-block-end-stack 2block))
+ (new-end end)
+ (cleanup (block-end-cleanup block))
+ (found-similar-p nil))
+ (dolist (succ (block-succ block))
+ #+nil
+ (when (and (< block succ)
+ (eq cleanup (block-end-cleanup succ)))
+ (setq found-similar-p t))
+ (setq new-end (merge-stacks new-end (ir2-block-start-stack (block-info succ)))))
+ (unless found-similar-p
+ (map-block-nlxes (lambda (nlx-info)
+ (let* ((nle (nlx-info-target nlx-info))
+ (nle-start-stack (ir2-block-start-stack
+ (block-info nle)))
+ (exit-lvar (nlx-info-lvar nlx-info)))
+ (when (eq exit-lvar (car nle-start-stack))
+ (pop nle-start-stack))
+ (setq new-end (merge-stacks new-end
+ nle-start-stack))))
+ block))
- (setf (ir2-block-start-stack 2block) new-stack)
+ (setf (ir2-block-end-stack 2block) new-end)
+ (let ((start new-end))
+ (dolist (push (reverse (ir2-block-pushed 2block)))
+ (if (eq (car start) push)
+ (pop start)
+ (aver (not (member push start)))))
- (when new-stack
- (dolist (pred (block-pred block))
- (if (eq pred (component-head (block-component block)))
- (aver (find block
- (physenv-nlx-info (block-physenv block))
- :key #'nlx-info-target))
- (let ((pred-stack (ir2-block-end-stack (block-info pred))))
- (unless (tailp new-stack pred-stack)
- (aver (search pred-stack new-stack))
- (stack-simulation-walk pred new-stack))))))))
+ (dolist (pop (reverse (ir2-block-popped 2block)))
+ (push pop start))
- (values))
+ (cond ((equal-but-no-car-recursion start
+ (ir2-block-start-stack 2block))
+ nil)
+ (t
+ (setf (ir2-block-start-stack 2block) start)
+ t)))))
;;; Do stack annotation for any values generators in Block that were
-;;; unreached by all walks (i.e. the continuation isn't live at the point that
+;;; unreached by all walks (i.e. the lvar isn't live at the point that
;;; it is generated.) This will only happen when the values receiver cannot be
;;; reached from this particular generator (due to an unconditional control
;;; transfer.)
;;;
-;;; What we do is push on the End-Stack all continuations in Pushed that
+;;; What we do is push on the End-Stack all lvars in Pushed that
;;; aren't already present in the End-Stack. When we find any pushed
-;;; continuation that isn't live, it must be the case that all continuations
+;;; lvar that isn't live, it must be the case that all lvars
;;; pushed after (on top of) it aren't live.
;;;
-;;; If we see a pushed continuation that is the CONT of a tail call, then we
-;;; ignore it, since the tail call didn't actually push anything. The tail
-;;; call must always the last in the block.
+;;; If we see a pushed lvar that is the LVAR of a tail call, then we
+;;; ignore it, since the tail call didn't actually push anything. The
+;;; tail call must always the last in the block.
+;;;
+;;; [This function also fixes End-Stack in NLEs.]
(defun annotate-dead-values (block)
(declare (type cblock block))
(let* ((2block (block-info block))
(setq popping t))))))
(values))
+
+;;; For every NLE block push all LVARs that are live in its ENTRY to
+;;; its start stack. (We cannot pop unused LVARs on a control transfer
+;;; to an NLE block, so we must do it later.)
+(defun fix-nle-block-stacks (component)
+ (declare (type component component))
+ (dolist (block (block-succ (component-head component)))
+ (let ((start-node (block-start-node block)))
+ (unless (bind-p start-node)
+ (let* ((2block (block-info block))
+ (start-stack (block-start-stack 2block))
+ (nlx-ref (ctran-next (node-next start-node)))
+ (nlx-info (constant-value (ref-leaf nlx-ref)))
+ (mess-up (cleanup-mess-up (nlx-info-cleanup nlx-info)))
+ (entry-block (node-block mess-up))
+ (entry-stack (ir2-block-start-stack (block-info entry-block)))
+ (exit-lvar (nlx-info-lvar nlx-info)))
+ (when (and exit-lvar
+ (eq exit-lvar (car start-stack)))
+ (when *check-consistency*
+ (aver (not (memq exit-lvar entry-stack))))
+ (push exit-lvar entry-stack))
+ (when *check-consistency*
+ (aver (subsetp start-stack entry-stack)))
+ (setf (ir2-block-start-stack 2block) entry-stack)
+ (setf (ir2-block-end-stack 2block) entry-stack)
+ ; ANNOTATE-DEAD-VALUES will do the rest
+ )))))
\f
;;; This is called when we discover that the stack-top unknown-values
-;;; continuation at the end of BLOCK1 is different from that at the
-;;; start of BLOCK2 (its successor).
+;;; lvar at the end of BLOCK1 is different from that at the start of
+;;; BLOCK2 (its successor).
;;;
;;; We insert a call to a funny function in a new cleanup block
;;; introduced between BLOCK1 and BLOCK2. Since control analysis and
;;; LTN have already run, we must do make an IR2 block, then do
-;;; ADD-TO-EMIT-ORDER and LTN-ANALYZE-BELATED-BLOCK on the new block.
-;;; The new block is inserted after BLOCK1 in the emit order.
+;;; ADD-TO-EMIT-ORDER and LTN-ANALYZE-BELATED-BLOCK on the new
+;;; block. The new block is inserted after BLOCK1 in the emit order.
;;;
;;; If the control transfer between BLOCK1 and BLOCK2 represents a
-;;; tail-recursive return (:DELETED IR2-continuation) or a non-local
-;;; exit, then the cleanup code will never actually be executed. It
-;;; doesn't seem to be worth the risk of trying to optimize this,
-;;; since this rarely happens and wastes only space.
+;;; tail-recursive return or a non-local exit, then the cleanup code
+;;; will never actually be executed. It doesn't seem to be worth the
+;;; risk of trying to optimize this, since this rarely happens and
+;;; wastes only space.
(defun discard-unused-values (block1 block2)
(declare (type cblock block1 block2))
(let* ((block1-stack (ir2-block-end-stack (block-info block1)))
\f
;;;; stack analysis
-;;; Return a list of all the blocks containing genuine uses of one of the
-;;; RECEIVERS. Exits are excluded, since they don't drop through to the
-;;; receiver.
+;;; Return a list of all the blocks containing genuine uses of one of
+;;; the RECEIVERS. Exits are excluded, since they don't drop through
+;;; to the receiver.
(defun find-values-generators (receivers)
(declare (list receivers))
(collect ((res nil adjoin))
(res (node-block use))))))
(res)))
-;;; Analyze the use of unknown-values continuations in COMPONENT,
-;;; inserting cleanup code to discard values that are generated but
-;;; never received. This phase doesn't need to be run when
-;;; Values-Receivers is null, i.e. there are no unknown-values
-;;; continuations used across block boundaries.
+;;; Analyze the use of unknown-values lvars in COMPONENT, inserting
+;;; cleanup code to discard values that are generated but never
+;;; received. This phase doesn't need to be run when Values-Receivers
+;;; is null, i.e. there are no unknown-values lvars used across block
+;;; boundaries.
;;;
;;; Do the backward graph walk, starting at each values receiver. We
;;; ignore receivers that already have a non-null START-STACK. These
(dolist (block generators)
(find-pushed-lvars block))
- (dolist (block receivers)
- (unless (ir2-block-start-stack (block-info block))
- (stack-simulation-walk block ())))
+ (loop for did-something = nil
+ do (do-blocks-backwards (block component)
+ (when (stack-update block)
+ (setq did-something t)))
+ while did-something)
+
+ (when *check-consistency*
+ (dolist (block (block-succ (component-head component)))
+ (when (bind-p (block-start-node block))
+ (aver (null (ir2-block-start-stack (block-info block)))))))
(dolist (block generators)
(annotate-dead-values block))
projects / sbcl.git / blobdiff