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add some call optimizer doc

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Andrea Corallo 2019-09-23 09:13:46 +02:00
parent 414a2b5bbc
commit bdea0f62b5
1 changed files with 14 additions and 1 deletions
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15
lisp/emacs-lisp/comp.el
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@ -1341,7 +1341,19 @@ This can run just once."
;;; Call optimizer pass specific code.
;; Try to avoid funcall trampoline use when possible.
;; This pass is responsible for the following optimizations:
;; - Call to subrs that are in defined in the C source and are passing through
;; funcall trampoline gets optimized into normal indirect calls.
;; This makes effectively this calls equivalent to all the subrs that got
;; dedicated byte-code ops.
;; Triggered at comp-speed >= 2.
;; - Recursive calls gets optimized into direct calls.
;; Triggered at comp-speed >= 2.
;; - Intra compilation unit procedure calls gets optimized into direct calls.
;; This can be a big win and even allow gcc to inline but does not make
;; function in the compilation unit re-definable safely without recompiling
;; the full compilation unit.
;; For this reason this is triggered only at comp-speed == 3.
(defun comp-call-optim-form-call (callee args self)
""
@ -1361,6 +1373,7 @@ This can run just once."
(callee-in-unit (gethash callee
(comp-ctxt-funcs-h comp-ctxt))))
(if (and subrp (not (subr-native-elispp f)))
;; Trampoline removal.
(let* ((maxarg (cdr (subr-arity f)))
(call-type (if (if subrp
(not (numberp maxarg))