bug#48261: 28.0.50; Optimize `eql' to `eq' for fixnums

[Philipp Stephani]

It would be nice if the byte optimizer could optimize `eql' to `eq' if
one of the arguments is guaranteed to be a fixnum.  Patch is attached.

>From 8b6f76df20454bb0caaba71cac9c5c3a7cb2aa62 Mon Sep 17 00:00:00 2001
From: Philipp Stephani <phst@google.com>
Date: Thu, 6 May 2021 19:13:00 +0200
Subject: [PATCH] Optimize calls to 'eql', 'memql' and similar for fixnums.

It's good practice to compare integers using 'eql' because two bignum
objects representing the same integer might not be 'eq'.  However,
'eql' is slower and doesn't have its own byte code.  Therefore,
replace it with 'eq' if one argument is guaranteed to be a fixnum on
all platforms.

* lisp/emacs-lisp/byte-opt.el (byte-optimize--fixnump): New helper
function.
(byte-optimize-equal, byte-optimize-member, byte-optimize-assoc): Use
it to optimize 'eql' etc. to 'eq' if it will always compare fixnums.
---
 lisp/emacs-lisp/byte-opt.el | 25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

diff --git a/lisp/emacs-lisp/byte-opt.el b/lisp/emacs-lisp/byte-opt.el
index 33b4d4b3c8..4dd8b90b3a 100644
--- a/lisp/emacs-lisp/byte-opt.el
+++ b/lisp/emacs-lisp/byte-opt.el
@@ -951,12 +951,20 @@ byte-optimize--constant-symbol-p
   "Whether EXPR is a constant symbol."
   (and (macroexp-const-p expr) (symbolp (eval expr))))
 
+(defun byte-optimize--fixnump (o)
+  "Return whether O is guaranteed to be a fixnum in all Emacsen.
+See Info node `(elisp) Integer Basics'."
+  (and (fixnump o) (<= -536870912 o 536870911)))
+
 (defun byte-optimize-equal (form)
-  ;; Replace `equal' or `eql' with `eq' if at least one arg is a symbol.
+  ;; Replace `equal' or `eql' with `eq' if at least one arg is a
+  ;; symbol or fixnum.
   (byte-optimize-binary-predicate
    (if (= (length (cdr form)) 2)
        (if (or (byte-optimize--constant-symbol-p (nth 1 form))
-               (byte-optimize--constant-symbol-p (nth 2 form)))
+               (byte-optimize--constant-symbol-p (nth 2 form))
+               (byte-optimize--fixnump (nth 1 form))
+               (byte-optimize--fixnump (nth 2 form)))
            (cons 'eq (cdr form))
          form)
      ;; Arity errors reported elsewhere.
@@ -964,14 +972,18 @@ byte-optimize-equal
 
 (defun byte-optimize-member (form)
   ;; Replace `member' or `memql' with `memq' if the first arg is a symbol,
-  ;; or the second arg is a list of symbols.
+  ;; or the second arg is a list of symbols.  Same with fixnums.
   (if (= (length (cdr form)) 2)
       (if (or (byte-optimize--constant-symbol-p (nth 1 form))
+              (byte-optimize--fixnump (nth 1 form))
               (let ((arg2 (nth 2 form)))
                 (and (macroexp-const-p arg2)
                      (let ((listval (eval arg2)))
                        (and (listp listval)
-                            (not (memq nil (mapcar #'symbolp listval))))))))
+                            (cl-every
+                             (lambda (o)
+                               (or (symbolp o) (byte-optimize--fixnump o)))
+                             listval))))))
           (cons 'memq (cdr form))
         form)
     ;; Arity errors reported elsewhere.
@@ -979,11 +991,12 @@ byte-optimize-member
 
 (defun byte-optimize-assoc (form)
   ;; Replace 2-argument `assoc' with `assq', `rassoc' with `rassq',
-  ;; if the first arg is a symbol.
+  ;; if the first arg is a symbol or fixnum.
   (cond
    ((/= (length form) 3)
     form)
-   ((byte-optimize--constant-symbol-p (nth 1 form))
+   ((or (byte-optimize--constant-symbol-p (nth 1 form))
+        (byte-optimize--fixnump (nth 1 form)))
     (cons (if (eq (car form) 'assoc) 'assq 'rassq)
           (cdr form)))
    (t (byte-optimize-constant-args form))))
-- 
2.31.1.607.g51e8a6a459-goog



In GNU Emacs 28.0.50 (build 95, x86_64-pc-linux-gnu, GTK+ Version 3.24.24, 
cairo version 1.16.0)
 of 2021-05-06
Repository revision: 8b7495a722a57071cb2a978665f95f8227db2863
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12010000
System Description: Debian GNU/Linux rodete

Configured using:
 'configure --enable-gcc-warnings=warn-only
 --enable-gtk-deprecation-warnings --without-pop --with-mailutils
 --enable-checking=all --enable-check-lisp-object-type --with-modules
 'CFLAGS=-O0 -ggdb3''

Configured features:
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Important settings:
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Memory information:
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