[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[PATCH 3/3] New module 'count-trailing-zeros'.
|
From: |
Paul Eggert |
|
Subject: |
[PATCH 3/3] New module 'count-trailing-zeros'. |
|
Date: |
Mon, 07 Oct 2013 00:02:03 -0700 |
|
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.0 |
* MODULES.html.sh: Mention it.
* lib/count-trailing-zeros.c, lib/count-trailing-zeros.h:
* m4/count-trailing-zeros.m4, modules/count-trailing-zeros:
* modules/count-trailing-zeros-tests:
* tests/test-count-trailing-zeros.c:
New files.
---
ChangeLog | 8 +++
MODULES.html.sh | 1 +
lib/count-trailing-zeros.c | 3 ++
lib/count-trailing-zeros.h | 106 +++++++++++++++++++++++++++++++++++++
m4/count-trailing-zeros.m4 | 12 +++++
modules/count-trailing-zeros | 25 +++++++++
modules/count-trailing-zeros-tests | 11 ++++
tests/test-count-trailing-zeros.c | 71 +++++++++++++++++++++++++
8 files changed, 237 insertions(+)
create mode 100644 lib/count-trailing-zeros.c
create mode 100644 lib/count-trailing-zeros.h
create mode 100644 m4/count-trailing-zeros.m4
create mode 100644 modules/count-trailing-zeros
create mode 100644 modules/count-trailing-zeros-tests
create mode 100644 tests/test-count-trailing-zeros.c
diff --git a/ChangeLog b/ChangeLog
index 9e80e07..01dca10 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,13 @@
2013-10-06 Paul Eggert <address@hidden>
+ New module 'count-trailing-zeros'.
+ * MODULES.html.sh: Mention it.
+ * lib/count-trailing-zeros.c, lib/count-trailing-zeros.h:
+ * m4/count-trailing-zeros.m4, modules/count-trailing-zeros:
+ * modules/count-trailing-zeros-tests:
+ * tests/test-count-trailing-zeros.c:
+ New files.
+
count-leading-zeros: port to MSC; support types wider than 64 bits
The ideas behind the MSC port are stolen from Emacs.
* lib/count-leading-zeros.h:
diff --git a/MODULES.html.sh b/MODULES.html.sh
index 5a563d4..5a0405c 100755
--- a/MODULES.html.sh
+++ b/MODULES.html.sh
@@ -1757,6 +1757,7 @@ func_all_modules ()
func_begin_table
func_module count-leading-zeros
func_module count-one-bits
+ func_module count-trailing-zeros
func_module ffs
func_module ffsl
func_module ffsll
diff --git a/lib/count-trailing-zeros.c b/lib/count-trailing-zeros.c
new file mode 100644
index 0000000..f3da886
--- /dev/null
+++ b/lib/count-trailing-zeros.c
@@ -0,0 +1,3 @@
+#include <config.h>
+#define COUNT_TRAILING_ZEROS_INLINE _GL_EXTERN_INLINE
+#include "count-trailing-zeros.h"
diff --git a/lib/count-trailing-zeros.h b/lib/count-trailing-zeros.h
new file mode 100644
index 0000000..1dab45d
--- /dev/null
+++ b/lib/count-trailing-zeros.h
@@ -0,0 +1,106 @@
+/* count-trailing-zeros.h -- counts the number of trailing 0 bits in a word.
+ Copyright 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 Paul Eggert. */
+
+#ifndef COUNT_TRAILING_ZEROS_H
+#define COUNT_TRAILING_ZEROS_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_TRAILING_ZEROS_INLINE
+# define COUNT_TRAILING_ZEROS_INLINE _GL_INLINE
+#endif
+
+/* Assuming the GCC builtin is BUILTIN and the MSC builtin is MSC_BUILTIN,
+ expand to code that computes the number of trailing 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)
+# define COUNT_TRAILING_ZEROS(BUILTIN, MSC_BUILTIN, TYPE) \
+ return x ? BUILTIN (x) : CHAR_BIT * sizeof x;
+#elif _MSC_VER
+# pragma intrinsic _BitScanForward
+# pragma intrinsic _BitScanForward64
+# define COUNT_TRAILING_ZEROS(BUILTIN, MSC_BUILTIN, TYPE) \
+ do \
+ { \
+ unsigned long result; \
+ return MSC_BUILTIN (&result, x) ? result : CHAR_BIT * sizeof x; \
+ } \
+ while (0)
+#else
+# define COUNT_TRAILING_ZEROS(BUILTIN, MSC_BUILTIN, TYPE) \
+ do \
+ { \
+ int count = 0; \
+ if (! x) \
+ return CHAR_BIT * sizeof x; \
+ for (count = 0; \
+ (count < CHAR_BIT * sizeof x - 32 \
+ && ! (x & 0xffffffffU)); \
+ count += 32) \
+ x = x >> 31 >> 1; \
+ return count + count_trailing_zeros_32 (x); \
+ } \
+ while (0)
+
+/* Compute and return the number of trailing zeros in the least
+ significant 32 bits of X. One of these bits must be nonzero. */
+COUNT_TRAILING_ZEROS_INLINE int
+count_trailing_zeros_32 (unsigned int x)
+{
+ /* http://graphics.stanford.edu/~seander/bithacks.html */
+ static const char de_Bruijn_lookup[32] = {
+ 0, 1, 28, 2, 29, 14, 24, 3, 30, 22, 20, 15, 25, 17, 4, 8,
+ 31, 27, 13, 23, 21, 19, 16, 7, 26, 12, 18, 6, 11, 5, 10, 9
+ };
+ return de_Bruijn_lookup[(((x & -x) * 0x077cb531U) & 0xffffffffU) >> 27];
+}
+#endif
+
+/* Compute and return the number of trailing zeros in X. */
+COUNT_TRAILING_ZEROS_INLINE int
+count_trailing_zeros (unsigned int x)
+{
+ COUNT_TRAILING_ZEROS (__builtin_ctz, _BitScanForward, unsigned int);
+}
+
+/* Compute and return the number of trailing zeros in X. */
+COUNT_TRAILING_ZEROS_INLINE int
+count_trailing_zeros_l (unsigned long int x)
+{
+ COUNT_TRAILING_ZEROS (__builtin_ctzl, _BitScanForward, unsigned long int);
+}
+
+#if HAVE_UNSIGNED_LONG_LONG_INT
+/* Compute and return the number of trailing zeros in X. */
+COUNT_TRAILING_ZEROS_INLINE int
+count_trailing_zeros_ll (unsigned long long int x)
+{
+ COUNT_TRAILING_ZEROS (__builtin_ctzll, _BitScanForward64,
+ unsigned long long int);
+}
+#endif
+
+_GL_INLINE_HEADER_END
+
+#endif
diff --git a/m4/count-trailing-zeros.m4 b/m4/count-trailing-zeros.m4
new file mode 100644
index 0000000..b4a13c1
--- /dev/null
+++ b/m4/count-trailing-zeros.m4
@@ -0,0 +1,12 @@
+# count-trailing-zeros.m4
+dnl Copyright (C) 2013 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.
+
+AC_DEFUN([gl_COUNT_TRAILING_ZEROS],
+[
+ dnl We don't need (and can't compile) count_trailing_zeros_ll
+ dnl unless the type 'unsigned long long int' exists.
+ AC_REQUIRE([AC_TYPE_UNSIGNED_LONG_LONG_INT])
+])
diff --git a/modules/count-trailing-zeros b/modules/count-trailing-zeros
new file mode 100644
index 0000000..841cfda
--- /dev/null
+++ b/modules/count-trailing-zeros
@@ -0,0 +1,25 @@
+Description:
+Counts the number of trailing 0-bits in a word.
+
+Files:
+lib/count-trailing-zeros.c
+lib/count-trailing-zeros.h
+m4/count-trailing-zeros.m4
+
+Depends-on:
+extern-inline
+
+configure.ac:
+gl_COUNT_TRAILING_ZEROS
+
+Makefile.am:
+lib_SOURCES += count-trailing-zeros.c
+
+Include:
+"count-trailing-zeros.h"
+
+License:
+LGPLv2+
+
+Maintainer:
+all
diff --git a/modules/count-trailing-zeros-tests
b/modules/count-trailing-zeros-tests
new file mode 100644
index 0000000..88b2d0a
--- /dev/null
+++ b/modules/count-trailing-zeros-tests
@@ -0,0 +1,11 @@
+Files:
+tests/test-count-trailing-zeros.c
+tests/macros.h
+
+Depends-on:
+
+configure.ac:
+
+Makefile.am:
+TESTS += test-count-trailing-zeros
+check_PROGRAMS += test-count-trailing-zeros
diff --git a/tests/test-count-trailing-zeros.c
b/tests/test-count-trailing-zeros.c
new file mode 100644
index 0000000..98a5f87
--- /dev/null
+++ b/tests/test-count-trailing-zeros.c
@@ -0,0 +1,71 @@
+/* Test counting of trailing zeros.
+ Copyright (C) 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 Paul Eggert. */
+
+#include <config.h>
+
+#include "count-trailing-zeros.h"
+
+#include <limits.h>
+#include <stdio.h>
+
+#include "macros.h"
+
+#define UINT_BIT (sizeof (unsigned int) * CHAR_BIT)
+#define ULONG_BIT (sizeof (unsigned long int) * CHAR_BIT)
+#define ULLONG_BIT (sizeof (unsigned long long int) * CHAR_BIT)
+
+#ifndef ULLONG_MAX
+# define HALF (1ULL << (sizeof (unsigned long long int) * CHAR_BIT - 1))
+# define ULLONG_MAX (HALF - 1 + HALF)
+#endif
+
+int
+main (int argc, char *argv[])
+{
+ int i, j;
+
+#define TEST_COUNT_TRAILING_ZEROS(FUNC, TYPE, BITS, MAX, ONE) \
+ ASSERT (FUNC (0) == BITS); \
+ for (i = 0; i < BITS; i++) \
+ { \
+ ASSERT (FUNC (ONE << i) == i); \
+ for (j = 0; j < i; j++) \
+ ASSERT (FUNC ((ONE << i) | (ONE << j)) == j); \
+ } \
+ for (i = 0; i < 1000; i++) \
+ { \
+ TYPE value = rand () ^ (rand () << 31 << 1); \
+ int count = 0; \
+ for (j = BITS - 1; 0 <= j; j--) \
+ if (value & (ONE << j)) \
+ count = j; \
+ ASSERT (count == FUNC (value)); \
+ } \
+ ASSERT (FUNC (MAX) == 0);
+
+ TEST_COUNT_TRAILING_ZEROS (count_trailing_zeros, unsigned int,
+ UINT_BIT, UINT_MAX, 1U);
+ TEST_COUNT_TRAILING_ZEROS (count_trailing_zeros_l, unsigned long int,
+ ULONG_BIT, ULONG_MAX, 1UL);
+#ifdef HAVE_UNSIGNED_LONG_LONG_INT
+ TEST_COUNT_TRAILING_ZEROS (count_trailing_zeros_ll, unsigned long long int,
+ ULLONG_BIT, ULLONG_MAX, 1ULL);
+#endif
+
+ return 0;
+}
--
1.8.3.1