-;;;; This file contains the control analysis pass in the compiler. This
-;;;; pass determines the order in which the IR2 blocks are to be
+;;;; This file contains the control analysis pass in the compiler.
+;;;; This pass determines the order in which the IR2 blocks are to be
;;;; emitted, attempting to minimize the associated branching costs.
;;;;
;;;; At this point, we commit to generating IR2 (and ultimately
(in-package "SB!C")
-;;; Insert Block in the emission order after the block After.
+;;; Insert BLOCK in the emission order after the block AFTER.
(defun add-to-emit-order (block after)
(declare (type block-annotation block after))
(let ((next (block-annotation-next after)))
(setf (block-annotation-prev next) block))
(values))
-;;; If Block looks like the head of a loop, then attempt to rotate it.
+;;; If BLOCK looks like the head of a loop, then attempt to rotate it.
;;; A block looks like a loop head if the number of some predecessor
;;; is less than the block's number. Since blocks are numbered in
;;; reverse DFN, this will identify loop heads in a reducible flow
;;; suppress rotation of loop heads which are the start of a function
;;; (i.e. tail calls), as the debugger wants functions to start at the
;;; start.
+;;;
+;;; The rotation also is not done if the back edge identified in the
+;;; first step originates from a block that has more than one successor.
+;;; This matches loops that have their terminating condition tested at
+;;; the end, for which the original block order already minimizes the
+;;; number of branches: the back edge starts at a conditional branch at
+;;; the loop's tail and no other branches are needed. We used not to
+;;; test for this situation, rotating these loops, too, resulting in
+;;; machine code that looked like this
+;;; jump to L1
+;;; L0: body of loop
+;;; conditionally branch to L2 if the loop should terminate
+;;; L1: jump to L0
+;;; L2:
+;;; which is ugly, and larger and often slower than what is generated
+;;; when not rotating these loops.
(defun find-rotated-loop-head (block)
(declare (type cblock block))
(let* ((num (block-number block))
- (env (block-environment block))
- (pred (dolist (pred (block-pred block) nil)
- (when (and (not (block-flag pred))
- (eq (block-environment pred) env)
- (< (block-number pred) num))
- (return pred)))))
+ (env (block-physenv block))
+ (pred (dolist (pred (block-pred block) nil)
+ (when (and (not (block-flag pred))
+ (eq (block-physenv pred) env)
+ (< (block-number pred) num))
+ (return pred)))))
(cond
((and pred
- (not (environment-nlx-info env))
- (not (eq (node-block (lambda-bind (block-home-lambda block)))
- block)))
+ (not (physenv-nlx-info env))
+ (not (eq (lambda-block (block-home-lambda block)) block))
+ (null (cdr (block-succ pred))))
(let ((current pred)
- (current-num (block-number pred)))
- (block DONE
- (loop
- (dolist (pred (block-pred current) (return-from DONE))
- (when (eq pred block)
- (return-from DONE))
- (when (and (not (block-flag pred))
- (eq (block-environment pred) env)
- (> (block-number pred) current-num))
- (setq current pred current-num (block-number pred))
- (return)))))
- (aver (not (block-flag current)))
- current))
+ (current-num (block-number pred)))
+ (block DONE
+ (loop
+ (dolist (pred (block-pred current) (return-from DONE))
+ (when (eq pred block)
+ (return-from DONE))
+ (when (and (not (block-flag pred))
+ (eq (block-physenv pred) env)
+ (> (block-number pred) current-num))
+ (setq current pred current-num (block-number pred))
+ (return)))))
+ (aver (not (block-flag current)))
+ current))
(t
block))))
-;;; Do a graph walk linking blocks into the emit order as we go. We call
-;;; FIND-ROTATED-LOOP-HEAD to do while-loop optimization.
+;;; Do a graph walk linking blocks into the emit order as we go. We
+;;; call FIND-ROTATED-LOOP-HEAD to do while-loop optimization.
;;;
;;; We treat blocks ending in tail local calls to other environments
-;;; specially. We can't walked the called function immediately, since it is in
-;;; a different function and we must keep the code for a function contiguous.
-;;; Instead, we return the function that we want to call so that it can be
-;;; walked as soon as possible, which is hopefully immediately.
+;;; specially. We can't walked the called function immediately, since
+;;; it is in a different function and we must keep the code for a
+;;; function contiguous. Instead, we return the function that we want
+;;; to call so that it can be walked as soon as possible, which is
+;;; hopefully immediately.
;;;
-;;; If any of the recursive calls ends in a tail local call, then we return
-;;; the last such function, since it is the only one we can possibly drop
-;;; through to. (But it doesn't have to be from the last block walked, since
-;;; that call might not have added anything.)
+;;; If any of the recursive calls ends in a tail local call, then we
+;;; return the last such function, since it is the only one we can
+;;; possibly drop through to. (But it doesn't have to be from the last
+;;; block walked, since that call might not have added anything.)
;;;
-;;; We defer walking successors whose successor is the component tail (end
-;;; in an error, NLX or tail full call.) This is to discourage making error
-;;; code the drop-through.
+;;; We defer walking successors whose successor is the component tail
+;;; (end in an error, NLX or tail full call.) This is to discourage
+;;; making error code the drop-through.
(defun control-analyze-block (block tail block-info-constructor)
- (declare (type cblock block) (type block-annotation tail))
+ (declare (type cblock block)
+ (type block-annotation tail)
+ (type function block-info-constructor))
(unless (block-flag block)
(let ((block (find-rotated-loop-head block)))
(setf (block-flag block) t)
(aver (and (block-component block) (not (block-delete-p block))))
(add-to-emit-order (or (block-info block)
- (setf (block-info block)
- (funcall block-info-constructor block)))
- (block-annotation-prev tail))
+ (setf (block-info block)
+ (funcall block-info-constructor block)))
+ (block-annotation-prev tail))
(let ((last (block-last block)))
- (cond ((and (combination-p last) (node-tail-p last)
- (eq (basic-combination-kind last) :local)
- (not (eq (node-environment last)
- (lambda-environment (combination-lambda last)))))
- (combination-lambda last))
- (t
- (let ((component-tail (component-tail (block-component block)))
- (block-succ (block-succ block))
- (fun nil))
- (dolist (succ block-succ)
- (unless (eq (first (block-succ succ)) component-tail)
- (let ((res (control-analyze-block
- succ tail block-info-constructor)))
- (when res (setq fun res)))))
- (dolist (succ block-succ)
- (control-analyze-block succ tail block-info-constructor))
- fun)))))))
+ (cond ((and (combination-p last) (node-tail-p last)
+ (eq (basic-combination-kind last) :local)
+ (not (eq (node-physenv last)
+ (lambda-physenv (combination-lambda last)))))
+ (combination-lambda last))
+ (t
+ (let ((component-tail (component-tail (block-component block)))
+ (block-succ (block-succ block))
+ (fun nil))
+ (dolist (succ block-succ)
+ (unless (eq (first (block-succ succ)) component-tail)
+ (let ((res (control-analyze-block
+ succ tail block-info-constructor)))
+ (when res (setq fun res)))))
+ (dolist (succ block-succ)
+ (control-analyze-block succ tail block-info-constructor))
+ fun)))))))
-;;; Analyze all of the NLX EPs first to ensure that code reachable only from
-;;; a NLX is emitted contiguously with the code reachable from the Bind. Code
-;;; reachable from the Bind is inserted *before* the NLX code so that the Bind
-;;; marks the beginning of the code for the function. If the walks from NLX
-;;; EPs reach the bind block, then we just move it to the beginning.
+;;; Analyze all of the NLX EPs first to ensure that code reachable
+;;; only from a NLX is emitted contiguously with the code reachable
+;;; from the BIND. Code reachable from the BIND is inserted *before*
+;;; the NLX code so that the BIND marks the beginning of the code for
+;;; the function. If the walks from NLX EPs reach the BIND block, then
+;;; we just move it to the beginning.
;;;
-;;; If the walk from the bind node encountered a tail local call, then we
-;;; start over again there to help the call drop through. Of course, it will
-;;; never get a drop-through if either function has NLX code.
+;;; If the walk from the BIND node encountered a tail local call, then
+;;; we start over again there to help the call drop through. Of
+;;; course, it will never get a drop-through if either function has
+;;; NLX code.
(defun control-analyze-1-fun (fun component block-info-constructor)
- (declare (type clambda fun) (type component component))
+ (declare (type clambda fun)
+ (type component component)
+ (type function block-info-constructor))
(let* ((tail-block (block-info (component-tail component)))
- (prev-block (block-annotation-prev tail-block))
- (bind-block (node-block (lambda-bind fun))))
+ (prev-block (block-annotation-prev tail-block))
+ (bind-block (node-block (lambda-bind fun))))
(unless (block-flag bind-block)
- (dolist (nlx (environment-nlx-info (lambda-environment fun)))
- (control-analyze-block (nlx-info-target nlx) tail-block
- block-info-constructor))
+ (dolist (nlx (physenv-nlx-info (lambda-physenv fun)))
+ (control-analyze-block (nlx-info-target nlx) tail-block
+ block-info-constructor))
(cond
((block-flag bind-block)
- (let* ((block-note (block-info bind-block))
- (prev (block-annotation-prev block-note))
- (next (block-annotation-next block-note)))
- (setf (block-annotation-prev next) prev)
- (setf (block-annotation-next prev) next)
- (add-to-emit-order block-note prev-block)))
+ (let* ((block-note (block-info bind-block))
+ (prev (block-annotation-prev block-note))
+ (next (block-annotation-next block-note)))
+ (setf (block-annotation-prev next) prev)
+ (setf (block-annotation-next prev) next)
+ (add-to-emit-order block-note prev-block)))
(t
- (let ((new-fun (control-analyze-block bind-block
- (block-annotation-next
- prev-block)
- block-info-constructor)))
- (when new-fun
- (control-analyze-1-fun new-fun component
- block-info-constructor)))))))
+ (let ((new-fun (control-analyze-block bind-block
+ (block-annotation-next
+ prev-block)
+ block-info-constructor)))
+ (when new-fun
+ (control-analyze-1-fun new-fun component
+ block-info-constructor)))))))
(values))
-;;; Do control analysis on Component, finding the emit order. Our only
-;;; cleverness here is that we walk XEP's first to increase the probability
-;;; that the tail call will be a drop-through.
+;;; Do control analysis on COMPONENT, finding the emit order. Our only
+;;; cleverness here is that we walk XEP's first to increase the
+;;; probability that the tail call will be a drop-through.
;;;
-;;; When we are done, we delete blocks that weren't reached by the walk.
-;;; Some return blocks are made unreachable by LTN without setting
-;;; COMPONENT-REANALYZE. We remove all deleted blocks from the IR2-COMPONENT
-;;; VALUES-RECEIVERS to keep stack analysis from getting confused.
+;;; When we are done, we delete blocks that weren't reached by the
+;;; walk. Some return blocks are made unreachable by LTN without
+;;; setting COMPONENT-REANALYZE. We remove all deleted blocks from the
+;;; IR2-COMPONENT VALUES-RECEIVERS to keep stack analysis from getting
+;;; confused.
(defevent control-deleted-block "control analysis deleted dead block")
(defun control-analyze (component block-info-constructor)
(declare (type component component)
- (type function block-info-constructor))
+ (type function block-info-constructor))
(let* ((head (component-head component))
- (head-block (funcall block-info-constructor head))
- (tail (component-tail component))
- (tail-block (funcall block-info-constructor tail)))
+ (head-block (funcall block-info-constructor head))
+ (tail (component-tail component))
+ (tail-block (funcall block-info-constructor tail)))
(setf (block-info head) head-block)
(setf (block-info tail) tail-block)
(setf (block-annotation-prev tail-block) head-block)
(clear-flags component)
(dolist (fun (component-lambdas component))
- (when (external-entry-point-p fun)
- (control-analyze-1-fun fun component block-info-constructor)))
+ (when (xep-p fun)
+ (control-analyze-1-fun fun component block-info-constructor)))
(dolist (fun (component-lambdas component))
(control-analyze-1-fun fun component block-info-constructor))
(do-blocks (block component)
(unless (block-flag block)
- (event control-deleted-block (continuation-next (block-start block)))
- (delete-block block))))
+ (event control-deleted-block (block-start-node block))
+ (delete-block block))))
(let ((2comp (component-info component)))
(when (ir2-component-p 2comp)
- ;; If it's not an ir2-component, don't worry about it.
+ ;; If it's not an IR2-COMPONENT, don't worry about it.
(setf (ir2-component-values-receivers 2comp)
- (delete-if-not #'block-component
- (ir2-component-values-receivers 2comp)))))
+ (delete-if-not #'block-component
+ (ir2-component-values-receivers 2comp)))))
(values))
projects / sbcl.git / blobdiff