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.

2 files changed, 74 insertions, 9 deletions

diff --git a/m4/gnulib-comp.m4 b/m4/gnulib-comp.m4
index 61040987b57..4dd1e68d15c 100644
--- a/m4/gnulib-comp.m4
+++ b/m4/gnulib-comp.m4
@@ -63,9 +63,6 @@ AC_DEFUN([gl_EARLY],
   # Code from module cloexec:
   # Code from module close-stream:
   # Code from module copy-file-range:
-  # Code from module count-leading-zeros:
-  # Code from module count-one-bits:
-  # Code from module count-trailing-zeros:
   # Code from module crypto/md5:
   # Code from module crypto/md5-buffer:
   # Code from module crypto/sha1-buffer:
@@ -174,7 +171,12 @@ AC_DEFUN([gl_EARLY],
   # Code from module ssize_t:
   # Code from module stat-time:
   # Code from module std-gnu11:
+  # Code from module stdbit-h:
   # Code from module stdbool:
+  # Code from module stdc_bit_width:
+  # Code from module stdc_count_ones:
+  # Code from module stdc_leading_zeros:
+  # Code from module stdc_trailing_zeros:
   # Code from module stdckdint:
   # Code from module stddef:
   # Code from module stdint:
@@ -514,7 +516,18 @@ AC_DEFUN([gl_INIT],
   gt_TYPE_SSIZE_T
   gl_STAT_TIME
   gl_STAT_BIRTHTIME
+  gl_STDBIT_H
+  gl_CONDITIONAL_HEADER([stdbit.h])
+  AC_PROG_MKDIR_P
   gl_C_BOOL
+  AC_REQUIRE([gl_STDBIT_H])
+  GL_STDC_BIT_WIDTH=1
+  AC_REQUIRE([gl_STDBIT_H])
+  GL_STDC_COUNT_ONES=1
+  AC_REQUIRE([gl_STDBIT_H])
+  GL_STDC_LEADING_ZEROS=1
+  AC_REQUIRE([gl_STDBIT_H])
+  GL_STDC_TRAILING_ZEROS=1
   AC_CHECK_HEADERS_ONCE([stdckdint.h])
   if test $ac_cv_header_stdckdint_h = yes; then
     GL_GENERATE_STDCKDINT_H=false
@@ -673,6 +686,7 @@ AC_DEFUN([gl_INIT],
   gl_gnulib_enabled_6099e9737f757db36c47fa9d9f02e88c=false
   gl_gnulib_enabled_strtoll=false
   gl_gnulib_enabled_utimens=false
+  gl_gnulib_enabled_verify=false
   gl_gnulib_enabled_682e609604ccaac6be382e4ee3a4eaec=false
   func_gl_gnulib_m4code_260941c0e5dc67ec9e87d1fb321c300b ()
   {
@@ -953,6 +967,12 @@ AC_DEFUN([gl_INIT],
       gl_gnulib_enabled_utimens=true
     fi
   }
+  func_gl_gnulib_m4code_verify ()
+  {
+    if $gl_gnulib_enabled_verify; then :; else
+      gl_gnulib_enabled_verify=true
+    fi
+  }
   func_gl_gnulib_m4code_682e609604ccaac6be382e4ee3a4eaec ()
   {
     if $gl_gnulib_enabled_682e609604ccaac6be382e4ee3a4eaec; then :; else
@@ -1016,6 +1036,9 @@ AC_DEFUN([gl_INIT],
   if case $host_os in mingw* | windows*) false;; *) test $HAVE_GETRANDOM = 0 || test $REPLACE_GETRANDOM = 1;; esac; then
     func_gl_gnulib_m4code_open
   fi
+  if test $REPLACE_MKTIME = 1; then
+    func_gl_gnulib_m4code_verify
+  fi
   if test $HAVE_READLINKAT = 0 || test $REPLACE_READLINKAT = 1; then
     func_gl_gnulib_m4code_260941c0e5dc67ec9e87d1fb321c300b
   fi
@@ -1025,6 +1048,9 @@ AC_DEFUN([gl_INIT],
   if test $ac_use_included_regex = yes; then
     func_gl_gnulib_m4code_fd38c7e463b54744b77b98aeafb4fa7c
   fi
+  if test $ac_use_included_regex = yes; then
+    func_gl_gnulib_m4code_verify
+  fi
   if test $HAVE_DECL_STRTOIMAX = 0 || test $REPLACE_STRTOIMAX = 1; then
     func_gl_gnulib_m4code_strtoll
   fi
@@ -1065,6 +1091,7 @@ AC_DEFUN([gl_INIT],
   AM_CONDITIONAL([gl_GNULIB_ENABLED_6099e9737f757db36c47fa9d9f02e88c], [$gl_gnulib_enabled_6099e9737f757db36c47fa9d9f02e88c])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_strtoll], [$gl_gnulib_enabled_strtoll])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_utimens], [$gl_gnulib_enabled_utimens])
+  AM_CONDITIONAL([gl_GNULIB_ENABLED_verify], [$gl_gnulib_enabled_verify])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_682e609604ccaac6be382e4ee3a4eaec], [$gl_gnulib_enabled_682e609604ccaac6be382e4ee3a4eaec])
   # End of code from modules
   m4_ifval(gl_LIBSOURCES_LIST, [
@@ -1276,12 +1303,6 @@ AC_DEFUN([gl_FILE_LIST], [
   lib/close-stream.c
   lib/close-stream.h
   lib/copy-file-range.c
-  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
   lib/diffseq.h
   lib/dirent-private.h
   lib/dirent.in.h
@@ -1414,6 +1435,12 @@ AC_DEFUN([gl_FILE_LIST], [
   lib/signal.in.h
   lib/stat-time.c
   lib/stat-time.h
+  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
   lib/stdckdint.in.h
   lib/stddef.in.h
   lib/stdint.in.h
@@ -1567,6 +1594,7 @@ AC_DEFUN([gl_FILE_LIST], [
   m4/stat-time.m4
   m4/std-gnu11.m4
   m4/stdalign.m4
+  m4/stdbit_h.m4
   m4/stddef_h.m4
   m4/stdint.m4
   m4/stdio_h.m4
diff --git a/m4/stdbit_h.m4 b/m4/stdbit_h.m4
new file mode 100644
index 00000000000..6af813f39dc
--- /dev/null
+++ b/m4/stdbit_h.m4
@@ -0,0 +1,37 @@
+# stdbit_h.m4
+# serial 2
+dnl Copyright 2024 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+dnl A placeholder for <stdbit.h>, for platforms that have issues.
+
+AC_DEFUN_ONCE([gl_STDBIT_H],
+[
+  AC_REQUIRE([gl_BIGENDIAN])
+
+  AC_CHECK_HEADERS_ONCE([stdbit.h])
+  if test $ac_cv_header_stdbit_h = yes; then
+    GL_GENERATE_STDBIT_H=false
+  else
+    GL_GENERATE_STDBIT_H=true
+  fi
+
+  dnl We don't use gl_MODULE_INDICATOR_INIT_VARIABLE here, because stdbit.in.h
+  dnl does not use #include_next.
+  GL_STDC_LEADING_ZEROS=0;       AC_SUBST([GL_STDC_LEADING_ZEROS])
+  GL_STDC_LEADING_ONES=0;        AC_SUBST([GL_STDC_LEADING_ONES])
+  GL_STDC_TRAILING_ZEROS=0;      AC_SUBST([GL_STDC_TRAILING_ZEROS])
+  GL_STDC_TRAILING_ONES=0;       AC_SUBST([GL_STDC_TRAILING_ONES])
+  GL_STDC_FIRST_LEADING_ZERO=0;  AC_SUBST([GL_STDC_FIRST_LEADING_ZERO])
+  GL_STDC_FIRST_LEADING_ONE=0;   AC_SUBST([GL_STDC_FIRST_LEADING_ONE])
+  GL_STDC_FIRST_TRAILING_ZERO=0; AC_SUBST([GL_STDC_FIRST_TRAILING_ZERO])
+  GL_STDC_FIRST_TRAILING_ONE=0;  AC_SUBST([GL_STDC_FIRST_TRAILING_ONE])
+  GL_STDC_COUNT_ZEROS=0;         AC_SUBST([GL_STDC_COUNT_ZEROS])
+  GL_STDC_COUNT_ONES=0;          AC_SUBST([GL_STDC_COUNT_ONES])
+  GL_STDC_HAS_SINGLE_BIT=0;      AC_SUBST([GL_STDC_HAS_SINGLE_BIT])
+  GL_STDC_BIT_WIDTH=0;           AC_SUBST([GL_STDC_BIT_WIDTH])
+  GL_STDC_BIT_FLOOR=0;           AC_SUBST([GL_STDC_BIT_FLOOR])
+  GL_STDC_BIT_CEIL=0;            AC_SUBST([GL_STDC_BIT_CEIL])
+])