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* Mitigate possible speed 3 miss-optimization

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Do not perform trampoline optimization at speed 3 on function if their
name is not unique inside the compilation unit.  Note that the
function can still be redefined in any other way therefore this is a
mitigation.

	* lisp/emacs-lisp/comp.el (comp-func-unique-in-cu-p): New
	predicate.
	(comp-call-optim-form-call): Perform trampoline optimization
	for named functions only if they are unique within the current
	compilation unit.
This commit is contained in:
Andrea Corallo 2020-06-06 16:53:34 +02:00
parent dcfcbb14f5
commit 489a79de96
1 changed files with 14 additions and 1 deletions
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15
lisp/emacs-lisp/comp.el
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@ -399,6 +399,18 @@ structure.")
"Type hint predicate for function name FUNC."
(when (memq func comp-type-hints) t))
(defun comp-func-unique-in-cu-p (func)
"Return t if FUNC is know to be unique in the current compilation unit."
(if (symbolp func)
(cl-loop with h = (make-hash-table :test #'eq)
for f being the hash-value in (comp-ctxt-funcs-h comp-ctxt)
for name = (comp-func-name f)
when (gethash name h)
return nil
do (puthash name t h)
finally return t)
t))
(defsubst comp-alloc-class-to-container (alloc-class)
"Given ALLOC-CLASS return the data container for the current context.
Assume allocaiton class 'd-default as default."
@ -2018,7 +2030,8 @@ FUNCTION can be a function-name or byte compiled function."
;; Intra compilation unit procedure call optimization.
;; Attention speed 3 triggers this for non self calls too!!
((and comp-func-callee
(or (>= comp-speed 3)
(or (and (>= comp-speed 3)
(comp-func-unique-in-cu-p callee))
(and (>= comp-speed 2)
;; Anonymous lambdas can't be redefined so are
;; always safe to optimize.