Constant-propagate cons and vector literals

* 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.

1 files changed, 9 insertions, 13 deletions

diff --git a/lisp/emacs-lisp/byte-opt.el b/lisp/emacs-lisp/byte-opt.el
index d046c4d401c..8fe5066c49e 100644
--- a/lisp/emacs-lisp/byte-opt.el
+++ b/lisp/emacs-lisp/byte-opt.el
@@ -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)