X-Git-Url: http://repo.macrolet.net/gitweb/?a=blobdiff_plain;f=src%2Fcompiler%2Fstack.lisp;h=02839bf983c167fe144a95c822e98936f7d4402d;hb=1d46d379bb7a6424524b978f213ef69be5f1ad69;hp=00dd5a6e30860a1ffa412cc5586c48d9a76ed791;hpb=7fd2eb4b1bc68e8aaec233c4a39bdfc40225bda2;p=sbcl.git diff --git a/src/compiler/stack.lisp b/src/compiler/stack.lisp index 00dd5a6..02839bf 100644 --- a/src/compiler/stack.lisp +++ b/src/compiler/stack.lisp @@ -1,6 +1,6 @@ ;;;; 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 @@ -14,150 +14,171 @@ (in-package "SB!C") -;;; Scan through Block looking for uses of :Unknown continuations that have -;;; their Dest outside of the block. We do some checking to verify the +;;; 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-continuations (block) +(defun find-pushed-lvars (block) (let* ((2block (block-info block)) (popped (ir2-block-popped 2block)) (last-pop (if popped - (continuation-dest (car (last popped))) + (lvar-dest (car (last popped))) nil))) (collect ((pushed)) (let ((saw-last nil)) - (do-nodes (node cont block) + (do-nodes (node lvar block) (when (eq node last-pop) (setq saw-last t)) - (let ((dest (continuation-dest cont)) - (2cont (continuation-info cont))) - (when (and dest - (not (eq (node-block dest) block)) - 2cont - (eq (ir2-continuation-kind 2cont) :unknown)) - (aver (or saw-last (not last-pop))) - (pushed cont))))) + (when lvar + (let ((dest (lvar-dest lvar)) + (2lvar (lvar-info lvar))) + (when (and (not (eq (node-block dest) block)) + 2lvar + (eq (ir2-lvar-kind 2lvar) :unknown)) + (aver (or saw-last (not last-pop))) + (pushed lvar)))))) (setf (ir2-block-pushed 2block) (pushed)))) (values)) ;;;; 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)) (stack (ir2-block-end-stack 2block)) (last (block-last block)) - (tailp-cont (if (node-tail-p last) (node-cont last)))) + (tailp-lvar (if (node-tail-p last) (node-lvar last)))) (do ((pushes (ir2-block-pushed 2block) (rest pushes)) (popping nil)) ((null pushes)) (let ((push (first pushes))) (cond ((member push stack) (aver (not popping))) - ((eq push tailp-cont) + ((eq push tailp-lvar) (aver (null (rest pushes)))) (t (push push (ir2-block-end-stack 2block)) (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 + ))))) ;;; 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))) @@ -169,7 +190,7 @@ (aver (tailp block2-stack block1-stack)) (let* ((block (insert-cleanup-code block1 block2 - (continuation-next (block-start block2)) + (block-start-node block2) `(%pop-values ',last-popped))) (2block (make-ir2-block block))) (setf (block-info block) 2block) @@ -180,9 +201,9 @@ ;;;; 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)) @@ -193,15 +214,17 @@ (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 are nested -;;; values receivers that have already been reached on another walk. We don't -;;; want to clobber that result with our null initial stack. +;;; Do the backward graph walk, starting at each values receiver. We +;;; ignore receivers that already have a non-null START-STACK. These +;;; are nested values receivers that have already been reached on +;;; another walk. We don't want to clobber that result with our null +;;; initial stack. (defun stack-analyze (component) (declare (type component component)) (let* ((2comp (component-info component)) @@ -209,11 +232,18 @@ (generators (find-values-generators receivers))) (dolist (block generators) - (find-pushed-continuations block)) + (find-pushed-lvars block)) + + (loop for did-something = nil + do (do-blocks-backwards (block component) + (when (stack-update block) + (setq did-something t))) + while did-something) - (dolist (block receivers) - (unless (ir2-block-start-stack (block-info block)) - (stack-simulation-walk block ()))) + (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))