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master 46d7d44 2/2: Strength-reduce (eq X nil) to (not X)
From: |
Mattias Engdegård |
Subject: |
master 46d7d44 2/2: Strength-reduce (eq X nil) to (not X) |
Date: |
Tue, 20 Jul 2021 13:31:26 -0400 (EDT) |
branch: master
commit 46d7d44894843bf30e9bc84473195c6ab892b752
Author: Mattias Engdegård <mattiase@acm.org>
Commit: Mattias Engdegård <mattiase@acm.org>
Strength-reduce (eq X nil) to (not X)
* lisp/emacs-lisp/byte-opt.el (byte-optimize-eq): New optimisation,
which results in better test and branch code generation where it
applies.
---
lisp/emacs-lisp/byte-opt.el | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/lisp/emacs-lisp/byte-opt.el b/lisp/emacs-lisp/byte-opt.el
index 2fff0bd..7ed04b3 100644
--- a/lisp/emacs-lisp/byte-opt.el
+++ b/lisp/emacs-lisp/byte-opt.el
@@ -969,6 +969,12 @@ See Info node `(elisp) Integer Basics'."
;; Arity errors reported elsewhere.
form)))
+(defun byte-optimize-eq (form)
+ (byte-optimize-binary-predicate
+ (pcase (cdr form)
+ ((or `(,x nil) `(nil ,x)) `(not ,x))
+ (_ form))))
+
(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. Same with fixnums.
@@ -1056,7 +1062,7 @@ See Info node `(elisp) Integer Basics'."
(put 'min 'byte-optimizer #'byte-optimize-min-max)
(put '= 'byte-optimizer #'byte-optimize-binary-predicate)
-(put 'eq 'byte-optimizer #'byte-optimize-binary-predicate)
+(put 'eq 'byte-optimizer #'byte-optimize-eq)
(put 'eql 'byte-optimizer #'byte-optimize-equal)
(put 'equal 'byte-optimizer #'byte-optimize-equal)
(put 'string= 'byte-optimizer #'byte-optimize-binary-predicate)