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Constant-propagate cons and vector literals

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* lisp/emacs-lisp/byte-opt.el (byte-optimize--substitutable-p):
Allow quoted lists and conses, and vector literals, to be substituted
from lexical variables.  This can eliminate variable bindings and
create new constant folding opportunities.
This commit is contained in:
Mattias Engdegård 2023-05-04 17:37:17 +02:00
parent 3b038d46e2
commit 044392c5c5
1 changed files with 9 additions and 13 deletions
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22
lisp/emacs-lisp/byte-opt.el
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@ -221,21 +221,17 @@ for speeding up processing.")
(defun byte-optimize--substitutable-p (expr)
"Whether EXPR is a constant that can be propagated."
;; Only consider numbers, symbols and strings to be values for substitution
;; purposes. Numbers and symbols are immutable, and mutating string
;; literals (or results from constant-evaluated string-returning functions)
;; can be considered undefined.
;; (What about other quoted values, like conses?)
(or (booleanp expr)
(numberp expr)
(stringp expr)
(and (consp expr)
(or (and (memq (car expr) '(quote function))
(symbolp (cadr expr)))
;; (internal-get-closed-var N) can be considered constant for
;; const-prop purposes.
(and (eq (car expr) 'internal-get-closed-var)
(integerp (cadr expr)))))
(arrayp expr)
(let ((head (car-safe expr)))
(cond ((eq head 'quote) t)
;; Don't substitute #'(lambda ...) since that would enable
;; uncontrolled inlining.
((eq head 'function) (symbolp (cadr expr)))
;; (internal-get-closed-var N) can be considered constant for
;; const-prop purposes.
((eq head 'internal-get-closed-var) (integerp (cadr expr)))))
(keywordp expr)))
(defmacro byte-optimize--pcase (exp &rest cases)