master: expt: use (= (ftruncate n) n) to check for integers

The branch "master" has been updated in SBCL:
       via  94b68202423cf0d220c0c690a9b9ae8a554985f7 (commit)
      from  c33aaa910bbff76a97f6347dc2df1b7cd99ac976 (commit)

- Log -----------------------------------------------------------------
commit 94b68202423cf0d220c0c690a9b9ae8a554985f7
Author: Stas Boukarev <[email protected]>
Date:   Sun Aug 30 08:59:42 2026 +0300

    expt: use (= (ftruncate n) n) to check for integers
    
    It's no slower, and can be faster if #+round-float is available.
    It's certainly simpler and more compact.
---
 src/code/irrat.lisp | 47 ++---------------------------------------------
 1 file changed, 2 insertions(+), 45 deletions(-)

diff --git a/src/code/irrat.lisp b/src/code/irrat.lisp
index ea148e5b9..231772b0f 100644
--- a/src/code/irrat.lisp
+++ b/src/code/irrat.lisp
@@ -215,51 +215,8 @@
   "Return BASE raised to the POWER."
   (declare (explicit-check)
            (maybe-inline expt))
-  (labels (;; determine if the double float is an integer
-           #+64-bit
-           (isint (n)
-             (or (zerop n)
-                 (let* ((bits (sb-kernel:double-float-bits n))
-                        (exponent (ldb sb-vm:double-float-exponent-byte bits)))
-                   (cond
-                     ((> exponent (+ sb-vm:double-float-bias sb-vm:double-float-digits)))
-                     ((> exponent sb-vm:double-float-bias)
-                      (not (logtest bits
-                                    (1- (ash 1 (- (+ sb-vm:double-float-bias sb-vm:double-float-digits)
-                                                  exponent))))))))))
-           #-64-bit
-           (isint (x)
-             (or (zerop x)
-                 (let* ((hi (double-float-high-bits x))
-                        (lo (double-float-low-bits x))
-                        (ihi (logand hi #x7fffffff)))
-                   (declare (type (unsigned-byte 31) ihi)
-                            (type (unsigned-byte 32) lo)
-                            (optimize (speed 3) (safety 0)))
-                   (let ((isint 0))
-                     (declare (type fixnum isint))
-                     (cond ((>= ihi #x43400000) ; exponent >= 53
-                            (setq isint 2))
-                           ((>= ihi #x3ff00000)
-                            (let ((k (- (ash ihi -20) #x3ff))) ; exponent
-                              (declare (type (mod 53) k))
-                              (cond ((> k 20)
-                                     (let* ((shift (- 52 k))
-                                            (j (ash lo (- shift)))
-                                            (j2 (ash j shift)))
-                                       (declare (type (mod 32) shift)
-                                                (type (unsigned-byte 32) j j2))
-                                       (when (= j2 lo)
-                                         (setq isint (- 2 (logand j 1))))))
-                                    ((= lo 0)
-                                     (let* ((shift (- 20 k))
-                                            (j (ash ihi (- shift)))
-                                            (j2 (ash j shift)))
-                                       (declare (type (mod 32) shift)
-                                                (type (unsigned-byte 31) j j2))
-                                       (when (= j2 ihi)
-                                         (setq isint (- 2 (logand j 1))))))))))
-                     (/= isint 0)))))
+  (labels ((isint (n)
+             (= (ftruncate n) n))
            (real-expt (x y rtype)
              (let ((x (coerce x 'double-float))
                    (y (coerce y 'double-float)))

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