Prefer stdbit.h to count-one-bits.h etc

C23's <stdbit.h> in the long run should be better supported than
Gnulib's count-one-bits.h and similar headers, so switch to the
C23 primitives, with a Gnulib fallback for platforms lacking C23.
* admin/merge-gnulib (GNULIB_MODULES): Remove count-leading-zeros,
count-one-bits, count-trailing-zeros.  Add stdc_bit_width,
stdc_count_ones, stdc_trailing_zeros.
* lib/count-leading-zeros.c, lib/count-leading-zeros.h:
* lib/count-one-bits.c, lib/count-one-bits.h:
* lib/count-trailing-zeros.c, lib/count-trailing-zeros.h: Remove.
* lib/stdbit.c, lib/stdbit.in.h, lib/stdc_bit_width.c:
* lib/stdc_count_ones.c, lib/stdc_leading_zeros.c:
* lib/stdc_trailing_zeros.c, m4/stdbit_h.m4:
New files, copied from Gnulib.
* lib/gnulib.mk.in, m4/gnulib-comp.m4: Regenerate.
* src/data.c: Do not include count-one-bits.h, count-trailing-zeros.h.
Instead, rely on lisp.h including stdbit.h.
(Flogcount, Fbool_vector_count_population)
(Fbool_vector_count_consecutive): Use stdbit.h macros instead of
count-one-bits.h and count-trailing-zeros.h macros.
(shift_right_ull, count_one_bits_word, pre_value)
(count_trailing_zero_bits): Remove; no longer needed.
* src/lisp.h: Include stdbit.h instead of count-leading-zeros.h.
(elogb): Use stdbit.h macro instead of count-leading-zeros.h macro.

1 files changed, 4 insertions, 3 deletions

diff --git a/src/lisp.h b/src/lisp.h
index 8ee37f5298a..d61a4d5c982 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -23,6 +23,7 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
 #include <alloca.h>
 #include <setjmp.h>
 #include <stdarg.h>
+#include <stdbit.h>
 #include <stdckdint.h>
 #include <stddef.h>
 #include <string.h>
@@ -37,7 +38,6 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
 
 #include <attribute.h>
 #include <byteswap.h>
-#include <count-leading-zeros.h>
 #include <intprops.h>
 #include <verify.h>
 
@@ -4148,11 +4148,12 @@ integer_to_uintmax (Lisp_Object num, uintmax_t *n)
     }
 }
 
-/* Return floor (log2 (N)) as an int, where 0 < N <= ULLONG_MAX.  */
+/* Return floor (log2 (N)) as an int.  If N is zero, return -1.  */
 INLINE int
 elogb (unsigned long long int n)
 {
-  return ULLONG_WIDTH - 1 - count_leading_zeros_ll (n);
+  int width = stdc_bit_width (n);
+  return width - 1;
 }
 
 /* A modification count.  These are wide enough, and incremented