Restore traditional lsh behavior on fixnums

* doc/lispref/numbers.texi (Bitwise Operations): Document that
the traditional (lsh A B) behavior is for fixnums, and that it
is an error if A and B are both negative and A is a bignum.
See Bug#32463.
* lisp/subr.el (lsh): New function, moved here from src/data.c.
* src/data.c (ash_lsh_impl): Remove, moving body into Fash
since it’s the only caller now.
(Fash): Check for out-of-range counts.  If COUNT is zero,
return first argument instead of going through libgmp.  Omit
lsh code since lsh is now done in Lisp.  Add code for shifting
fixnums right, to avoid a round trip through libgmp.
(Flsh): Remove; moved to lisp/subr.el.
* test/lisp/international/ccl-tests.el (shift):
Test for traditional lsh behavior, instead of assuming
lsh is like ash when bignums are present.
* test/src/data-tests.el (data-tests-logand)
(data-tests-logior, data-tests-logxor, data-tests-ash-lsh):
New tests.

1 files changed, 12 insertions, 0 deletions

diff --git a/lisp/subr.el b/lisp/subr.el
index fbb3e49a35c..cafa4835eaf 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -366,6 +366,18 @@ was called."
   (declare (compiler-macro (lambda (_) `(= 0 ,number))))
   (= 0 number))
 
+(defun lsh (value count)
+  "Return VALUE with its bits shifted left by COUNT.
+If COUNT is negative, shifting is actually to the right.
+In this case, if VALUE is a negative fixnum treat it as unsigned,
+i.e., subtract 2 * most-negative-fixnum from VALUE before shifting it."
+  (when (and (< value 0) (< count 0))
+    (when (< value most-negative-fixnum)
+      (signal 'args-out-of-range (list value count)))
+    (setq value (logand (ash value -1) most-positive-fixnum))
+    (setq count (1+ count)))
+  (ash value count))
+
 
 ;;;; List functions.