master: Transform floor/ceiling to truncate when used as a divisibility test

The branch "master" has been updated in SBCL:
       via  3eb58efbbe070e67ad7968f36e8d9c59b2e81e1f (commit)
      from  914726b494c081ae0a4cfe5e21c92f7532ff7f98 (commit)

- Log -----------------------------------------------------------------
commit 3eb58efbbe070e67ad7968f36e8d9c59b2e81e1f
Author: Stas Boukarev <[email protected]>
Date:   Mon Apr 20 04:26:35 2026 +0300

    Transform floor/ceiling to truncate when used as a divisibility test
---
 src/compiler/srctran.lisp | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/compiler/srctran.lisp b/src/compiler/srctran.lisp
index d48a4d38c..1af378318 100644
--- a/src/compiler/srctran.lisp
+++ b/src/compiler/srctran.lisp
@@ -4653,6 +4653,16 @@
                          (truly-the ,rem-type rem)))))
         (give-up-ir1-transform))))
 
+;;; (zerop (mod x y)) => (zerop (rem x y))
+(deftransforms (floor ceiling) ((number divisor) (rational rational) * :result result :node node)
+  (let ((rem (and (mv-bind-unused-p result 0)
+                  (mv-bind-dest result 1 t))))
+    (cond ((combination-matches 'eq '(* 0) rem)
+           (erase-node-type node (values-specifier-type '(values integer rational &optional)))
+           `(truncate number divisor))
+          (t
+           (give-up-ir1-transform)))))
+
 (deftransform ceiling ((number divisor) ((and unsigned-byte fixnum) (and unsigned-byte fixnum)) * :result result)
   (if (and result
            (lvar-single-value-p result))

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