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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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18
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)))
(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.
(and (eq (car expr) 'internal-get-closed-var)
(integerp (cadr expr)))))
((eq head 'internal-get-closed-var) (integerp (cadr expr)))))
(keywordp expr)))
(defmacro byte-optimize--pcase (exp &rest cases)