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Improve byte-switch execution.

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* lisp/emacs-lisp/byte-opt.el,
  lisp/emacs-lisp/bytecomp.el (byte-decompile-bytecode-1),
  (byte-compile-lapcode): Calculate the actual jump address while
  compiling, store it in the jump table.

* src/bytecode.c: Jump to the looked up value directly, do a linear
  search when the number of elements is <= 5.
This commit is contained in:
Vibhav Pant 2017-02-09 12:18:54 +05:30
parent 96c4e367f9
commit dde800c8c9
3 changed files with 33 additions and 15 deletions
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4
lisp/emacs-lisp/byte-opt.el
View file

@ -1411,10 +1411,8 @@
;; Replace all addresses with TAGs.
(maphash #'(lambda (value tag)
(let (newtag)
(cl-assert (consp tag)
nil "Invalid address for byte-switch")
(setq newtag (byte-compile-make-tag))
(push (cons (+ (car tag) (lsh (cdr tag) 8)) newtag) tags)
(push (cons tag newtag) tags)
(puthash value newtag last-constant)))
last-constant)
;; Replace the hash table referenced in the lapcode with our

9
lisp/emacs-lisp/bytecomp.el
View file

@ -917,10 +917,11 @@ CONST2 may be evaluated multiple times."
(if (> (car bytes-tail) 255) (error "Bytecode overflow")))
(dolist (hash-table byte-compile-jump-tables)
(cl-loop for k being the hash-keys of hash-table do
(let ((tag (cdr (gethash k hash-table))))
(setq pc (car tag))
(puthash k (cons (logand pc 255) (lsh pc -8)) hash-table))))
(maphash #'(lambda (value tag)
(setq pc (cadr tag))
(puthash value (+ (logand pc 255) (lsh (lsh pc -8) 8))
hash-table))
hash-table))
(apply 'unibyte-string (nreverse bytes))))