Improve support for popcount and counting trailing zeros.

Do this by using the Gnulib modules for this.
This should generate faster code on non-GCC, non-MSC platforms,
and make the code a bit more portable, at least in theory.
* admin/merge-gnulib (GNULIB_MODULES): Add count-one-bits
and count-trailing-zeros.
* lib/count-one-bits.c, lib/count-one-bits.h:
* lib/count-trailing-zeros.c, lib/count-trailing-zeros.h:
* m4/count-one-bits.m4, m4/count-trailing-zeros.m4:
New files, copied from gnulib.
* lib/gnulib.mk, m4/gnulib-comp.m4: Regenerate.
* nt/gnulib.mk: Merge changes from lib/gnulib.mk.
* src/data.c: Include <count-one-bits.h>, <count-trailing-zeros.h>.
(USE_MSC_POPCOUNT, POPCOUNT_STATIC_INLINE)
(NEED_GENERIC_POPCOUNT, popcount_size_t_generic)
(popcount_size_t_msc, popcount_size_t_gcc):
Remove; now done by Gnulib.
(popcount_size_t): Now a macro that defers to Gnulib.
(count_trailing_zero_bits): Return int, for consistency with
Gnulib and because Emacs prefers signed to unsigned int.
Don't assume that size_t is either unsigned int or unsigned long
or unsigned long long.
(size_t_to_host_endian): Do not assume that size_t is either
exactly 32 or exactly 64 bits wide.
* src/lisp.h (BITS_PER_SIZE_T): Define consistently with BITS_PER_LONG
etc., so that it's now an enum constant, not a macro.
No need to assume that it's either 32 or 64.

Fixes: debbugs:15550

1 files changed, 136 insertions, 0 deletions

diff --git a/lib/count-one-bits.h b/lib/count-one-bits.h
new file mode 100644
index 00000000000..2a7e93c3f40
--- /dev/null
+++ b/lib/count-one-bits.h
@@ -0,0 +1,136 @@
+/* count-one-bits.h -- counts the number of 1-bits in a word.
+   Copyright (C) 2007-2013 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+/* Written by Ben Pfaff.  */
+
+#ifndef COUNT_ONE_BITS_H
+#define COUNT_ONE_BITS_H 1
+
+#include <limits.h>
+#include <stdlib.h>
+
+#ifndef _GL_INLINE_HEADER_BEGIN
+ #error "Please include config.h first."
+#endif
+_GL_INLINE_HEADER_BEGIN
+#ifndef COUNT_ONE_BITS_INLINE
+# define COUNT_ONE_BITS_INLINE _GL_INLINE
+#endif
+
+/* Expand to code that computes the number of 1-bits of the local
+   variable 'x' of type TYPE (an unsigned integer type) and return it
+   from the current function.  */
+#define COUNT_ONE_BITS_GENERIC(TYPE)                                   \
+    do                                                                  \
+      {                                                                 \
+        int count = 0;                                                  \
+        int bits;                                                       \
+        for (bits = 0; bits < sizeof (TYPE) * CHAR_BIT; bits += 32)     \
+          {                                                             \
+            count += count_one_bits_32 (x);                             \
+            x = x >> 31 >> 1;                                           \
+          }                                                             \
+        return count;                                                   \
+      }                                                                 \
+    while (0)
+
+/* Assuming the GCC builtin is BUILTIN and the MSC builtin is MSC_BUILTIN,
+   expand to code that computes the number of 1-bits of the local
+   variable 'x' of type TYPE (an unsigned integer type) and return it
+   from the current function.  */
+#if __GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4)
+# define COUNT_ONE_BITS(BUILTIN, MSC_BUILTIN, TYPE) return BUILTIN (x)
+#else
+
+/* Compute and return the number of 1-bits set in the least
+   significant 32 bits of X. */
+COUNT_ONE_BITS_INLINE int
+count_one_bits_32 (unsigned int x)
+{
+  x = ((x & 0xaaaaaaaaU) >> 1) + (x & 0x55555555U);
+  x = ((x & 0xccccccccU) >> 2) + (x & 0x33333333U);
+  x = (x >> 16) + (x & 0xffff);
+  x = ((x & 0xf0f0) >> 4) + (x & 0x0f0f);
+  return (x >> 8) + (x & 0x00ff);
+}
+
+# if 1500 <= _MSC_VER && (defined _M_IX86 || defined _M_X64)
+
+/* While gcc falls back to its own generic code if the machine
+   on which it's running doesn't support popcount, with Microsoft's
+   compiler we need to detect and fallback ourselves.  */
+#  pragma intrinsic __cpuid
+#  pragma intrinsic __popcnt
+#  pragma intrinsic __popcnt64
+
+/* Return nonzero if popcount is supported.  */
+
+/* 1 if supported, 0 if not supported, -1 if unknown.  */
+extern int popcount_support;
+
+COUNT_ONE_BITS_INLINE int
+popcount_supported (void)
+{
+  if (popcount_support < 0)
+    {
+      int cpu_info[4];
+      __cpuid (cpu_info, 1);
+      popcount_support = (cpu_info[2] >> 23) & 1;  /* See MSDN.  */
+    }
+  return popcount_support;
+}
+
+#  define COUNT_ONE_BITS(BUILTIN, MSC_BUILTIN, TYPE)    \
+     do                                                 \
+       {                                                \
+         if (popcount_supported ())                     \
+           return MSC_BUILTIN (x);                      \
+         else                                           \
+           COUNT_ONE_BITS_GENERIC (TYPE);               \
+       }                                                \
+     while (0)
+# else
+#  define COUNT_ONE_BITS(BUILTIN, MSC_BUILTIN, TYPE)	\
+     COUNT_ONE_BITS_GENERIC (TYPE)
+# endif
+#endif
+
+/* Compute and return the number of 1-bits set in X. */
+COUNT_ONE_BITS_INLINE int
+count_one_bits (unsigned int x)
+{
+  COUNT_ONE_BITS (__builtin_popcount, __popcnt, unsigned int);
+}
+
+/* Compute and return the number of 1-bits set in X. */
+COUNT_ONE_BITS_INLINE int
+count_one_bits_l (unsigned long int x)
+{
+  COUNT_ONE_BITS (__builtin_popcountl, __popcnt, unsigned long int);
+}
+
+#if HAVE_UNSIGNED_LONG_LONG_INT
+/* Compute and return the number of 1-bits set in X. */
+COUNT_ONE_BITS_INLINE int
+count_one_bits_ll (unsigned long long int x)
+{
+  COUNT_ONE_BITS (__builtin_popcountll, __popcnt64, unsigned long long int);
+}
+#endif
+
+_GL_INLINE_HEADER_END
+
+#endif /* COUNT_ONE_BITS_H */