Function: byte-optimize-lapcode
byte-optimize-lapcode is an autoloaded and byte-compiled function
defined in byte-opt.el.gz.
Signature
(byte-optimize-lapcode LAP &optional FOR-EFFECT)
Documentation
Simple peephole optimizer. LAP is both modified and returned.
If FOR-EFFECT is non-nil, the return value is assumed to be of no importance.
Source Code
;; Defined in /usr/src/emacs/lisp/emacs-lisp/byte-opt.el.gz
;; This crock is because of the way DEFVAR_BOOL variables work.
;; Consider the code
;;
;; (defun foo (flag)
;; (let ((old-pop-ups pop-up-windows)
;; (pop-up-windows flag))
;; (cond ((not (eq pop-up-windows old-pop-ups))
;; (setq old-pop-ups pop-up-windows)
;; ...))))
;;
;; Uncompiled, old-pop-ups will always be set to nil or t, even if FLAG is
;; something else. But if we optimize
;;
;; varref flag
;; varbind pop-up-windows
;; varref pop-up-windows
;; not
;; to
;; varref flag
;; dup
;; varbind pop-up-windows
;; not
;;
;; we break the program, because it will appear that pop-up-windows and
;; old-pop-ups are not EQ when really they are. So we have to know what
;; the BOOL variables are, and not perform this optimization on them.
;; The variable `byte-boolean-vars' is now primitive and updated
;; automatically by DEFVAR_BOOL.
(defun byte-optimize-lapcode (lap &optional _for-effect)
"Simple peephole optimizer. LAP is both modified and returned.
If FOR-EFFECT is non-nil, the return value is assumed to be of no importance."
(let (lap0
lap1
lap2
(keep-going 'first-time)
(add-depth 0)
rest tmp tmp2 tmp3
(side-effect-free (if byte-compile-delete-errors
byte-compile-side-effect-free-ops
byte-compile-side-effect-and-error-free-ops)))
(while keep-going
(or (eq keep-going 'first-time)
(byte-compile-log-lap " ---- next pass"))
(setq rest lap
keep-going nil)
(while rest
(setq lap0 (car rest)
lap1 (nth 1 rest)
lap2 (nth 2 rest))
;; You may notice that sequences like "dup varset discard" are
;; optimized but sequences like "dup varset TAG1: discard" are not.
;; You may be tempted to change this; resist that temptation.
(cond
;; <side-effect-free> pop --> <deleted>
;; ...including:
;; const-X pop --> <deleted>
;; varref-X pop --> <deleted>
;; dup pop --> <deleted>
;;
((and (eq 'byte-discard (car lap1))
(memq (car lap0) side-effect-free))
(setq keep-going t)
(setq tmp (aref byte-stack+-info (symbol-value (car lap0))))
(setq rest (cdr rest))
(cond ((= tmp 1)
(byte-compile-log-lap
" %s discard\t-->\t<deleted>" lap0)
(setq lap (delq lap0 (delq lap1 lap))))
((= tmp 0)
(byte-compile-log-lap
" %s discard\t-->\t<deleted> discard" lap0)
(setq lap (delq lap0 lap)))
((= tmp -1)
(byte-compile-log-lap
" %s discard\t-->\tdiscard discard" lap0)
(setcar lap0 'byte-discard)
(setcdr lap0 0))
((error "Optimizer error: too much on the stack"))))
;;
;; goto*-X X: --> X:
;;
((and (memq (car lap0) byte-goto-ops)
(eq (cdr lap0) lap1))
(cond ((eq (car lap0) 'byte-goto)
(setq lap (delq lap0 lap))
(setq tmp "<deleted>"))
((memq (car lap0) byte-goto-always-pop-ops)
(setcar lap0 (setq tmp 'byte-discard))
(setcdr lap0 0))
((error "Depth conflict at tag %d" (nth 2 lap0))))
(and (memq byte-optimize-log '(t byte))
(byte-compile-log " (goto %s) %s:\t-->\t%s %s:"
(nth 1 lap1) (nth 1 lap1)
tmp (nth 1 lap1)))
(setq keep-going t))
;;
;; varset-X varref-X --> dup varset-X
;; varbind-X varref-X --> dup varbind-X
;; const/dup varset-X varref-X --> const/dup varset-X const/dup
;; const/dup varbind-X varref-X --> const/dup varbind-X const/dup
;; The latter two can enable other optimizations.
;;
;; For lexical variables, we could do the same
;; stack-set-X+1 stack-ref-X --> dup stack-set-X+2
;; but this is a very minor gain, since dup is stack-ref-0,
;; i.e. it's only better if X>5, and even then it comes
;; at the cost of an extra stack slot. Let's not bother.
((and (eq 'byte-varref (car lap2))
(eq (cdr lap1) (cdr lap2))
(memq (car lap1) '(byte-varset byte-varbind)))
(if (and (setq tmp (memq (car (cdr lap2)) byte-boolean-vars))
(not (eq (car lap0) 'byte-constant)))
nil
(setq keep-going t)
(if (memq (car lap0) '(byte-constant byte-dup))
(progn
(setq tmp (if (or (not tmp)
(macroexp--const-symbol-p
(car (cdr lap0))))
(cdr lap0)
(byte-compile-get-constant t)))
(byte-compile-log-lap " %s %s %s\t-->\t%s %s %s"
lap0 lap1 lap2 lap0 lap1
(cons (car lap0) tmp))
(setcar lap2 (car lap0))
(setcdr lap2 tmp))
(byte-compile-log-lap " %s %s\t-->\tdup %s" lap1 lap2 lap1)
(setcar lap2 (car lap1))
(setcar lap1 'byte-dup)
(setcdr lap1 0)
;; The stack depth gets locally increased, so we will
;; increase maxdepth in case depth = maxdepth here.
;; This can cause the third argument to byte-code to
;; be larger than necessary.
(setq add-depth 1))))
;;
;; dup varset-X discard --> varset-X
;; dup varbind-X discard --> varbind-X
;; dup stack-set-X discard --> stack-set-X-1
;; (the varbind variant can emerge from other optimizations)
;;
((and (eq 'byte-dup (car lap0))
(eq 'byte-discard (car lap2))
(memq (car lap1) '(byte-varset byte-varbind
byte-stack-set)))
(byte-compile-log-lap " dup %s discard\t-->\t%s" lap1 lap1)
(setq keep-going t
rest (cdr rest))
(if (eq 'byte-stack-set (car lap1)) (cl-decf (cdr lap1)))
(setq lap (delq lap0 (delq lap2 lap))))
;;
;; not goto-X-if-nil --> goto-X-if-non-nil
;; not goto-X-if-non-nil --> goto-X-if-nil
;;
;; it is wrong to do the same thing for the -else-pop variants.
;;
((and (eq 'byte-not (car lap0))
(memq (car lap1) '(byte-goto-if-nil byte-goto-if-not-nil)))
(byte-compile-log-lap " not %s\t-->\t%s"
lap1
(cons
(if (eq (car lap1) 'byte-goto-if-nil)
'byte-goto-if-not-nil
'byte-goto-if-nil)
(cdr lap1)))
(setcar lap1 (if (eq (car lap1) 'byte-goto-if-nil)
'byte-goto-if-not-nil
'byte-goto-if-nil))
(setq lap (delq lap0 lap))
(setq keep-going t))
;;
;; goto-X-if-nil goto-Y X: --> goto-Y-if-non-nil X:
;; goto-X-if-non-nil goto-Y X: --> goto-Y-if-nil X:
;;
;; it is wrong to do the same thing for the -else-pop variants.
;;
((and (memq (car lap0)
'(byte-goto-if-nil byte-goto-if-not-nil)) ; gotoX
(eq 'byte-goto (car lap1)) ; gotoY
(eq (cdr lap0) lap2)) ; TAG X
(let ((inverse (if (eq 'byte-goto-if-nil (car lap0))
'byte-goto-if-not-nil 'byte-goto-if-nil)))
(byte-compile-log-lap " %s %s %s:\t-->\t%s %s:"
lap0 lap1 lap2
(cons inverse (cdr lap1)) lap2)
(setq lap (delq lap0 lap))
(setcar lap1 inverse)
(setq keep-going t)))
;;
;; const goto-if-* --> whatever
;;
((and (eq 'byte-constant (car lap0))
(memq (car lap1) byte-conditional-ops)
;; If the `byte-constant's cdr is not a cons cell, it has
;; to be an index into the constant pool); even though
;; it'll be a constant, that constant is not known yet
;; (it's typically a free variable of a closure, so will
;; only be known when the closure will be built at
;; run-time).
(consp (cdr lap0)))
(cond ((if (memq (car lap1) '(byte-goto-if-nil
byte-goto-if-nil-else-pop))
(car (cdr lap0))
(not (car (cdr lap0))))
(byte-compile-log-lap " %s %s\t-->\t<deleted>"
lap0 lap1)
(setq rest (cdr rest)
lap (delq lap0 (delq lap1 lap))))
(t
(byte-compile-log-lap " %s %s\t-->\t%s"
lap0 lap1
(cons 'byte-goto (cdr lap1)))
(when (memq (car lap1) byte-goto-always-pop-ops)
(setq lap (delq lap0 lap)))
(setcar lap1 'byte-goto)))
(setq keep-going t))
;;
;; varref-X varref-X --> varref-X dup
;; varref-X [dup ...] varref-X --> varref-X [dup ...] dup
;; stackref-X [dup ...] stackref-X+N --> stackref-X [dup ...] dup
;; We don't optimize the const-X variations on this here,
;; because that would inhibit some goto optimizations; we
;; optimize the const-X case after all other optimizations.
;;
((and (memq (car lap0) '(byte-varref byte-stack-ref))
(progn
(setq tmp (cdr rest))
(setq tmp2 0)
(while (eq (car (car tmp)) 'byte-dup)
(setq tmp2 (1+ tmp2))
(setq tmp (cdr tmp)))
t)
(eq (if (eq 'byte-stack-ref (car lap0))
(+ tmp2 1 (cdr lap0))
(cdr lap0))
(cdr (car tmp)))
(eq (car lap0) (car (car tmp))))
(if (memq byte-optimize-log '(t byte))
(let ((str ""))
(setq tmp2 (cdr rest))
(while (not (eq tmp tmp2))
(setq tmp2 (cdr tmp2)
str (concat str " dup")))
(byte-compile-log-lap " %s%s %s\t-->\t%s%s dup"
lap0 str lap0 lap0 str)))
(setq keep-going t)
(setcar (car tmp) 'byte-dup)
(setcdr (car tmp) 0)
(setq rest tmp))
;;
;; TAG1: TAG2: --> TAG1: <deleted>
;; (and other references to TAG2 are replaced with TAG1)
;;
((and (eq (car lap0) 'TAG)
(eq (car lap1) 'TAG))
(and (memq byte-optimize-log '(t byte))
(byte-compile-log " adjacent tags %d and %d merged"
(nth 1 lap1) (nth 1 lap0)))
(setq tmp3 lap)
(while (setq tmp2 (rassq lap0 tmp3))
(setcdr tmp2 lap1)
(setq tmp3 (cdr (memq tmp2 tmp3))))
(setq lap (delq lap0 lap)
keep-going t)
;; replace references to tag in jump tables, if any
(dolist (table byte-compile-jump-tables)
(maphash #'(lambda (value tag)
(when (equal tag lap0)
(puthash value lap1 table)))
table)))
;;
;; unused-TAG: --> <deleted>
;;
((and (eq 'TAG (car lap0))
(not (rassq lap0 lap))
;; make sure this tag isn't used in a jump-table
(cl-loop for table in byte-compile-jump-tables
when (member lap0 (hash-table-values table))
return nil finally return t))
(and (memq byte-optimize-log '(t byte))
(byte-compile-log " unused tag %d removed" (nth 1 lap0)))
(setq lap (delq lap0 lap)
keep-going t))
;;
;; goto ... --> goto <delete until TAG or end>
;; return ... --> return <delete until TAG or end>
;; (unless a jump-table is being used, where deleting may affect
;; other valid case bodies)
;;
((and (memq (car lap0) '(byte-goto byte-return))
(not (memq (car lap1) '(TAG nil)))
;; FIXME: Instead of deferring simply when jump-tables are
;; being used, keep a list of tags used for switch tags and
;; use them instead (see `byte-compile-inline-lapcode').
(not byte-compile-jump-tables))
(setq tmp rest)
(let ((i 0)
(opt-p (memq byte-optimize-log '(t lap)))
str deleted)
(while (and (setq tmp (cdr tmp))
(not (eq 'TAG (car (car tmp)))))
(if opt-p (setq deleted (cons (car tmp) deleted)
str (concat str " %s")
i (1+ i))))
(if opt-p
(let ((tagstr
(if (eq 'TAG (car (car tmp)))
(format "%d:" (car (cdr (car tmp))))
(or (car tmp) ""))))
(if (< i 6)
(apply 'byte-compile-log-lap-1
(concat " %s" str
" %s\t-->\t%s <deleted> %s")
lap0
(nconc (nreverse deleted)
(list tagstr lap0 tagstr)))
(byte-compile-log-lap
" %s <%d unreachable op%s> %s\t-->\t%s <deleted> %s"
lap0 i (if (= i 1) "" "s")
tagstr lap0 tagstr))))
(rplacd rest tmp))
(setq keep-going t))
;;
;; <safe-op> unbind --> unbind <safe-op>
;; (this may enable other optimizations.)
;;
((and (eq 'byte-unbind (car lap1))
(memq (car lap0) byte-after-unbind-ops))
(byte-compile-log-lap " %s %s\t-->\t%s %s" lap0 lap1 lap1 lap0)
(setcar rest lap1)
(setcar (cdr rest) lap0)
(setq keep-going t))
;;
;; varbind-X unbind-N --> discard unbind-(N-1)
;; save-excursion unbind-N --> unbind-(N-1)
;; save-restriction unbind-N --> unbind-(N-1)
;;
((and (eq 'byte-unbind (car lap1))
(memq (car lap0) '(byte-varbind byte-save-excursion
byte-save-restriction))
(< 0 (cdr lap1)))
(if (zerop (setcdr lap1 (1- (cdr lap1))))
(delq lap1 rest))
(if (eq (car lap0) 'byte-varbind)
(setcar rest (cons 'byte-discard 0))
(setq lap (delq lap0 lap)))
(byte-compile-log-lap " %s %s\t-->\t%s %s"
lap0 (cons (car lap1) (1+ (cdr lap1)))
(if (eq (car lap0) 'byte-varbind)
(car rest)
(car (cdr rest)))
(if (and (/= 0 (cdr lap1))
(eq (car lap0) 'byte-varbind))
(car (cdr rest))
""))
(setq keep-going t))
;;
;; goto*-X ... X: goto-Y --> goto*-Y
;; goto-X ... X: return --> return
;;
((and (memq (car lap0) byte-goto-ops)
(memq (car (setq tmp (nth 1 (memq (cdr lap0) lap))))
'(byte-goto byte-return)))
(cond ((and (not (eq tmp lap0))
(or (eq (car lap0) 'byte-goto)
(eq (car tmp) 'byte-goto)))
(byte-compile-log-lap " %s [%s]\t-->\t%s"
(car lap0) tmp tmp)
(if (eq (car tmp) 'byte-return)
(setcar lap0 'byte-return))
(setcdr lap0 (cdr tmp))
(setq keep-going t))))
;;
;; goto-*-else-pop X ... X: goto-if-* --> whatever
;; goto-*-else-pop X ... X: discard --> whatever
;;
((and (memq (car lap0) '(byte-goto-if-nil-else-pop
byte-goto-if-not-nil-else-pop))
(memq (car (car (setq tmp (cdr (memq (cdr lap0) lap)))))
(eval-when-compile
(cons 'byte-discard byte-conditional-ops)))
(not (eq lap0 (car tmp))))
(setq tmp2 (car tmp))
(setq tmp3 (assq (car lap0) '((byte-goto-if-nil-else-pop
byte-goto-if-nil)
(byte-goto-if-not-nil-else-pop
byte-goto-if-not-nil))))
(if (memq (car tmp2) tmp3)
(progn (setcar lap0 (car tmp2))
(setcdr lap0 (cdr tmp2))
(byte-compile-log-lap " %s-else-pop [%s]\t-->\t%s"
(car lap0) tmp2 lap0))
;; Get rid of the -else-pop's and jump one step further.
(or (eq 'TAG (car (nth 1 tmp)))
(setcdr tmp (cons (byte-compile-make-tag)
(cdr tmp))))
(byte-compile-log-lap " %s [%s]\t-->\t%s <skip>"
(car lap0) tmp2 (nth 1 tmp3))
(setcar lap0 (nth 1 tmp3))
(setcdr lap0 (nth 1 tmp)))
(setq keep-going t))
;;
;; const goto-X ... X: goto-if-* --> whatever
;; const goto-X ... X: discard --> whatever
;;
((and (eq (car lap0) 'byte-constant)
(eq (car lap1) 'byte-goto)
(memq (car (car (setq tmp (cdr (memq (cdr lap1) lap)))))
(eval-when-compile
(cons 'byte-discard byte-conditional-ops)))
(not (eq lap1 (car tmp))))
(setq tmp2 (car tmp))
(cond ((when (consp (cdr lap0))
(memq (car tmp2)
(if (null (car (cdr lap0)))
'(byte-goto-if-nil byte-goto-if-nil-else-pop)
'(byte-goto-if-not-nil
byte-goto-if-not-nil-else-pop))))
(byte-compile-log-lap " %s goto [%s]\t-->\t%s %s"
lap0 tmp2 lap0 tmp2)
(setcar lap1 (car tmp2))
(setcdr lap1 (cdr tmp2))
;; Let next step fix the (const,goto-if*) sequence.
(setq rest (cons nil rest))
(setq keep-going t))
((or (consp (cdr lap0))
(eq (car tmp2) 'byte-discard))
;; Jump one step further
(byte-compile-log-lap
" %s goto [%s]\t-->\t<deleted> goto <skip>"
lap0 tmp2)
(or (eq 'TAG (car (nth 1 tmp)))
(setcdr tmp (cons (byte-compile-make-tag)
(cdr tmp))))
(setcdr lap1 (car (cdr tmp)))
(setq lap (delq lap0 lap))
(setq keep-going t))))
;;
;; X: varref-Y ... varset-Y goto-X -->
;; X: varref-Y Z: ... dup varset-Y goto-Z
;; (varset-X goto-BACK, BACK: varref-X --> copy the varref down.)
;; (This is so usual for while loops that it is worth handling).
;;
;; Here again, we could do it for stack-ref/stack-set, but
;; that's replacing a stack-ref-Y with a stack-ref-0, which
;; is a very minor improvement (if any), at the cost of
;; more stack use and more byte-code. Let's not do it.
;;
((and (eq (car lap1) 'byte-varset)
(eq (car lap2) 'byte-goto)
(not (memq (cdr lap2) rest)) ;Backwards jump
(eq (car (car (setq tmp (cdr (memq (cdr lap2) lap)))))
'byte-varref)
(eq (cdr (car tmp)) (cdr lap1))
(not (memq (car (cdr lap1)) byte-boolean-vars)))
;;(byte-compile-log-lap " Pulled %s to end of loop" (car tmp))
(let ((newtag (byte-compile-make-tag)))
(byte-compile-log-lap
" %s: %s ... %s %s\t-->\t%s: %s %s: ... %s %s %s"
(nth 1 (cdr lap2)) (car tmp)
lap1 lap2
(nth 1 (cdr lap2)) (car tmp)
(nth 1 newtag) 'byte-dup lap1
(cons 'byte-goto newtag)
)
(setcdr rest (cons (cons 'byte-dup 0) (cdr rest)))
(setcdr tmp (cons (setcdr lap2 newtag) (cdr tmp))))
(setq add-depth 1)
(setq keep-going t))
;;
;; goto-X Y: ... X: goto-if*-Y --> goto-if-not-*-X+1 Y:
;; (This can pull the loop test to the end of the loop)
;;
((and (eq (car lap0) 'byte-goto)
(eq (car lap1) 'TAG)
(eq lap1
(cdr (car (setq tmp (cdr (memq (cdr lap0) lap))))))
(memq (car (car tmp))
'(byte-goto byte-goto-if-nil byte-goto-if-not-nil
byte-goto-if-nil-else-pop)))
;; (byte-compile-log-lap " %s %s, %s %s --> moved conditional"
;; lap0 lap1 (cdr lap0) (car tmp))
(let ((newtag (byte-compile-make-tag)))
(byte-compile-log-lap
"%s %s: ... %s: %s\t-->\t%s ... %s:"
lap0 (nth 1 lap1) (nth 1 (cdr lap0)) (car tmp)
(cons (cdr (assq (car (car tmp))
'((byte-goto-if-nil . byte-goto-if-not-nil)
(byte-goto-if-not-nil . byte-goto-if-nil)
(byte-goto-if-nil-else-pop .
byte-goto-if-not-nil-else-pop)
(byte-goto-if-not-nil-else-pop .
byte-goto-if-nil-else-pop))))
newtag)
(nth 1 newtag)
)
(setcdr tmp (cons (setcdr lap0 newtag) (cdr tmp)))
(if (eq (car (car tmp)) 'byte-goto-if-nil-else-pop)
;; We can handle this case but not the -if-not-nil case,
;; because we won't know which non-nil constant to push.
(setcdr rest (cons (cons 'byte-constant
(byte-compile-get-constant nil))
(cdr rest))))
(setcar lap0 (nth 1 (memq (car (car tmp))
'(byte-goto-if-nil-else-pop
byte-goto-if-not-nil
byte-goto-if-nil
byte-goto-if-not-nil
byte-goto byte-goto))))
)
(setq keep-going t))
;;
;; stack-set-M [discard/discardN ...] --> discardN-preserve-tos
;; stack-set-M [discard/discardN ...] --> discardN
;;
((and (eq (car lap0) 'byte-stack-set)
(memq (car lap1) '(byte-discard byte-discardN))
(progn
;; See if enough discard operations follow to expose or
;; destroy the value stored by the stack-set.
(setq tmp (cdr rest))
(setq tmp2 (1- (cdr lap0)))
(setq tmp3 0)
(while (memq (car (car tmp)) '(byte-discard byte-discardN))
(setq tmp3
(+ tmp3 (if (eq (car (car tmp)) 'byte-discard)
1
(cdr (car tmp)))))
(setq tmp (cdr tmp)))
(>= tmp3 tmp2)))
;; Do the optimization.
(setq lap (delq lap0 lap))
(setcar lap1
(if (= tmp2 tmp3)
;; The value stored is the new TOS, so pop one more
;; value (to get rid of the old value) using the
;; TOS-preserving discard operator.
'byte-discardN-preserve-tos
;; Otherwise, the value stored is lost, so just use a
;; normal discard.
'byte-discardN))
(setcdr lap1 (1+ tmp3))
(setcdr (cdr rest) tmp)
(byte-compile-log-lap " %s [discard/discardN]...\t-->\t%s"
lap0 lap1))
;;
;; discardN-preserve-tos return --> return
;; dup return --> return
;; stack-set-N return --> return ; where N is TOS-1
;;
((and (eq (car lap1) 'byte-return)
(or (memq (car lap0) '(byte-discardN-preserve-tos byte-dup))
(and (eq (car lap0) 'byte-stack-set)
(= (cdr lap0) 1))))
(setq keep-going t)
;; The byte-code interpreter will pop the stack for us, so
;; we can just leave stuff on it.
(setq lap (delq lap0 lap))
(byte-compile-log-lap " %s %s\t-->\t%s" lap0 lap1 lap1))
;;
;; goto-X ... X: discard ==> discard goto-Y ... X: discard Y:
;;
((and (eq (car lap0) 'byte-goto)
(setq tmp (cdr (memq (cdr lap0) lap)))
(memq (caar tmp) '(byte-discard byte-discardN
byte-discardN-preserve-tos)))
(byte-compile-log-lap
" goto-X .. X: \t-->\t%s goto-X.. X: %s Y:"
(car tmp) (car tmp))
(setq keep-going t)
(let* ((newtag (byte-compile-make-tag))
;; Make a copy, since we sometimes modify insts in-place!
(newdiscard (cons (caar tmp) (cdar tmp)))
(newjmp (cons (car lap0) newtag)))
(push newtag (cdr tmp)) ;Push new tag after the discard.
(setcar rest newdiscard)
(push newjmp (cdr rest))))
;;
;; const discardN-preserve-tos ==> discardN const
;;
((and (eq (car lap0) 'byte-constant)
(eq (car lap1) 'byte-discardN-preserve-tos))
(setq keep-going t)
(let ((newdiscard (cons 'byte-discardN (cdr lap1))))
(byte-compile-log-lap
" %s %s\t-->\t%s %s" lap0 lap1 newdiscard lap0)
(setf (car rest) newdiscard)
(setf (cadr rest) lap0)))
)
(setq rest (cdr rest)))
)
;; Cleanup stage:
;; Rebuild byte-compile-constants / byte-compile-variables.
;; Simple optimizations that would inhibit other optimizations if they
;; were done in the optimizing loop, and optimizations which there is no
;; need to do more than once.
(setq byte-compile-constants nil
byte-compile-variables nil)
(setq rest lap)
(byte-compile-log-lap " ---- final pass")
(while rest
(setq lap0 (car rest)
lap1 (nth 1 rest))
(if (memq (car lap0) byte-constref-ops)
(if (memq (car lap0) '(byte-constant byte-constant2))
(unless (memq (cdr lap0) byte-compile-constants)
(setq byte-compile-constants (cons (cdr lap0)
byte-compile-constants)))
(unless (memq (cdr lap0) byte-compile-variables)
(setq byte-compile-variables (cons (cdr lap0)
byte-compile-variables)))))
(cond (;;
;; const-C varset-X const-C --> const-C dup varset-X
;; const-C varbind-X const-C --> const-C dup varbind-X
;;
(and (eq (car lap0) 'byte-constant)
(eq (car (nth 2 rest)) 'byte-constant)
(eq (cdr lap0) (cdr (nth 2 rest)))
(memq (car lap1) '(byte-varbind byte-varset)))
(byte-compile-log-lap " %s %s %s\t-->\t%s dup %s"
lap0 lap1 lap0 lap0 lap1)
(setcar (cdr (cdr rest)) (cons (car lap1) (cdr lap1)))
(setcar (cdr rest) (cons 'byte-dup 0))
(setq add-depth 1))
;;
;; const-X [dup/const-X ...] --> const-X [dup ...] dup
;; varref-X [dup/varref-X ...] --> varref-X [dup ...] dup
;;
((memq (car lap0) '(byte-constant byte-varref))
(setq tmp rest
tmp2 nil)
(while (progn
(while (eq 'byte-dup (car (car (setq tmp (cdr tmp))))))
(and (eq (cdr lap0) (cdr (car tmp)))
(eq (car lap0) (car (car tmp)))))
(setcar tmp (cons 'byte-dup 0))
(setq tmp2 t))
(if tmp2
(byte-compile-log-lap
" %s [dup/%s]...\t-->\t%s dup..." lap0 lap0 lap0)))
;;
;; unbind-N unbind-M --> unbind-(N+M)
;;
((and (eq 'byte-unbind (car lap0))
(eq 'byte-unbind (car lap1)))
(byte-compile-log-lap " %s %s\t-->\t%s" lap0 lap1
(cons 'byte-unbind
(+ (cdr lap0) (cdr lap1))))
(setq lap (delq lap0 lap))
(setcdr lap1 (+ (cdr lap1) (cdr lap0))))
;;
;; discard/discardN/discardN-preserve-tos-X discard/discardN-Y -->
;; discardN-(X+Y)
;;
((and (memq (car lap0)
'(byte-discard byte-discardN
byte-discardN-preserve-tos))
(memq (car lap1) '(byte-discard byte-discardN)))
(setq lap (delq lap0 lap))
(byte-compile-log-lap
" %s %s\t-->\t(discardN %s)"
lap0 lap1
(+ (if (eq (car lap0) 'byte-discard) 1 (cdr lap0))
(if (eq (car lap1) 'byte-discard) 1 (cdr lap1))))
(setcdr lap1 (+ (if (eq (car lap0) 'byte-discard) 1 (cdr lap0))
(if (eq (car lap1) 'byte-discard) 1 (cdr lap1))))
(setcar lap1 'byte-discardN))
;;
;; discardN-preserve-tos-X discardN-preserve-tos-Y -->
;; discardN-preserve-tos-(X+Y)
;;
((and (eq (car lap0) 'byte-discardN-preserve-tos)
(eq (car lap1) 'byte-discardN-preserve-tos))
(setq lap (delq lap0 lap))
(setcdr lap1 (+ (cdr lap0) (cdr lap1)))
(byte-compile-log-lap " %s %s\t-->\t%s" lap0 lap1 (car rest)))
)
(setq rest (cdr rest)))
(setq byte-compile-maxdepth (+ byte-compile-maxdepth add-depth)))
lap)