pmt: initial 3.0.2 update

include/libgnulib/count-leading-zeros.h

@@ -0,0 +1,140 @@
+/* count-leading-zeros.h -- counts the number of leading 0 bits in a word.
+   Copyright (C) 2012-2024 Free Software Foundation, Inc.
+
+   This file is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Lesser General Public License as
+   published by the Free Software Foundation; either version 2.1 of the
+   License, or (at your option) any later version.
+
+   This file 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 Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
+
+/* Written by Eric Blake.  */
+
+#ifndef COUNT_LEADING_ZEROS_H
+#define COUNT_LEADING_ZEROS_H 1
+
+/* This file uses _GL_INLINE_HEADER_BEGIN, _GL_INLINE.  */
+#if !_GL_CONFIG_H_INCLUDED
+ #error "Please include config.h first."
+#endif
+
+#include <limits.h>
+#include <stdlib.h>
+
+_GL_INLINE_HEADER_BEGIN
+#ifndef COUNT_LEADING_ZEROS_INLINE
+# define COUNT_LEADING_ZEROS_INLINE _GL_INLINE
+#endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* Assuming the GCC builtin is BUILTIN and the MSC builtin is MSC_BUILTIN,
+   expand to code that computes the number of leading zeros 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) \
+    || (__clang_major__ >= 4)
+# define COUNT_LEADING_ZEROS(BUILTIN, MSC_BUILTIN, TYPE)                \
+  return x ? BUILTIN (x) : CHAR_BIT * sizeof x;
+#elif _MSC_VER
+extern unsigned char _BitScanReverse (unsigned long *, unsigned long);
+# pragma intrinsic (_BitScanReverse)
+# if defined _M_X64
+extern unsigned char _BitScanReverse64 (unsigned long *, unsigned long long);
+#  pragma intrinsic (_BitScanReverse64)
+# endif
+# define COUNT_LEADING_ZEROS(BUILTIN, MSC_BUILTIN, TYPE)                \
+    do                                                                  \
+      {                                                                 \
+        unsigned long result;                                           \
+        if (MSC_BUILTIN (&result, x))                                   \
+          return CHAR_BIT * sizeof x - 1 - result;                      \
+        return CHAR_BIT * sizeof x;                                     \
+      }                                                                 \
+    while (0)
+#else
+# define COUNT_LEADING_ZEROS(BUILTIN, MSC_BUILTIN, TYPE)                \
+    do                                                                  \
+      {                                                                 \
+        int count;                                                      \
+        unsigned int leading_32;                                        \
+        if (! x)                                                        \
+          return CHAR_BIT * sizeof x;                                   \
+        for (count = 0;                                                 \
+             (leading_32 = ((x >> (sizeof (TYPE) * CHAR_BIT - 32))      \
+                            & 0xffffffffU),                             \
+              count < CHAR_BIT * sizeof x - 32 && !leading_32);         \
+             count += 32)                                               \
+          x = x << 31 << 1;                                             \
+        return count + count_leading_zeros_32 (leading_32);             \
+      }                                                                 \
+    while (0)
+
+/* Compute and return the number of leading zeros in X,
+   where 0 < X < 2**32.  */
+COUNT_LEADING_ZEROS_INLINE int
+count_leading_zeros_32 (unsigned int x)
+{
+  /* <https://github.com/gibsjose/BitHacks>
+     <https://www.fit.vutbr.cz/~ibarina/pub/bithacks.pdf> */
+  static const char de_Bruijn_lookup[32] = {
+    31, 22, 30, 21, 18, 10, 29, 2, 20, 17, 15, 13, 9, 6, 28, 1,
+    23, 19, 11, 3, 16, 14, 7, 24, 12, 4, 8, 25, 5, 26, 27, 0
+  };
+
+  x |= x >> 1;
+  x |= x >> 2;
+  x |= x >> 4;
+  x |= x >> 8;
+  x |= x >> 16;
+  return de_Bruijn_lookup[((x * 0x07c4acddU) & 0xffffffffU) >> 27];
+}
+#endif
+
+/* Compute and return the number of leading zeros in X. */
+COUNT_LEADING_ZEROS_INLINE int
+count_leading_zeros (unsigned int x)
+{
+  COUNT_LEADING_ZEROS (__builtin_clz, _BitScanReverse, unsigned int);
+}
+
+/* Compute and return the number of leading zeros in X. */
+COUNT_LEADING_ZEROS_INLINE int
+count_leading_zeros_l (unsigned long int x)
+{
+  COUNT_LEADING_ZEROS (__builtin_clzl, _BitScanReverse, unsigned long int);
+}
+
+/* Compute and return the number of leading zeros in X. */
+COUNT_LEADING_ZEROS_INLINE int
+count_leading_zeros_ll (unsigned long long int x)
+{
+#if (defined _MSC_VER && !defined __clang__) && !defined _M_X64
+  /* 32-bit MSVC does not have _BitScanReverse64, only _BitScanReverse.  */
+  unsigned long result;
+  if (_BitScanReverse (&result, (unsigned long) (x >> 32)))
+    return CHAR_BIT * sizeof x - 1 - 32 - result;
+  if (_BitScanReverse (&result, (unsigned long) x))
+    return CHAR_BIT * sizeof x - 1 - result;
+  return CHAR_BIT * sizeof x;
+#else
+  COUNT_LEADING_ZEROS (__builtin_clzll, _BitScanReverse64,
+                       unsigned long long int);
+#endif
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+_GL_INLINE_HEADER_END
+
+#endif /* COUNT_LEADING_ZEROS_H */