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Fix bug in g_bit_nth_lsf (#371631) and use __builtin_clzl for

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2007-01-03  Behdad Esfahbod  <behdad@gnome.org>

        * glib/gutils.h: Fix bug in g_bit_nth_lsf (#371631) and use 
        __builtin_clzl for g_bit_storage if available (#371670).

        * tests/Makefile.am:
        * tests/bit-test.c: New test, to test g_bit_* operations against
        naive and builtin implementations.


svn path=/trunk/; revision=5200
This commit is contained in:
Behdad Esfahbod 2007-01-03 20:08:53 +00:00 committed by Behdad Esfahbod
parent bf1b1d2711
commit 048efdfbd5
4 changed files with 168 additions and 8 deletions
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9
ChangeLog
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@ -1,3 +1,12 @@
2007-01-03 Behdad Esfahbod <behdad@gnome.org>
* glib/gutils.h: Fix bug in g_bit_nth_lsf (#371631) and use
__builtin_clzl for g_bit_storage if available (#371670).
* tests/Makefile.am:
* tests/bit-test.c: New test, to test g_bit_* operations against
naive and builtin implementations.
2007-01-02 Behdad Esfahbod <behdad@gnome.org>
* configure.in: Avoid more warnings from running libtool --config.

20
glib/gutils.h
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@ -250,10 +250,10 @@ gchar* g_find_program_in_path (const gchar *program);
/* Bit tests
*/
G_INLINE_FUNC gint g_bit_nth_lsf (gulong mask,
gint nth_bit);
gint nth_bit) G_GNUC_CONST;
G_INLINE_FUNC gint g_bit_nth_msf (gulong mask,
gint nth_bit);
G_INLINE_FUNC guint g_bit_storage (gulong number);
gint nth_bit) G_GNUC_CONST;
G_INLINE_FUNC guint g_bit_storage (gulong number) G_GNUC_CONST;
/* Trash Stacks
* elements need to be >= sizeof (gpointer)
@ -277,33 +277,36 @@ G_INLINE_FUNC gint
g_bit_nth_lsf (gulong mask,
gint nth_bit)
{
do
if (G_UNLIKELY (nth_bit < -1))
nth_bit = -1;
while (nth_bit < ((GLIB_SIZEOF_LONG * 8) - 1))
{
nth_bit++;
if (mask & (1UL << nth_bit))
return nth_bit;
}
while (nth_bit < ((GLIB_SIZEOF_LONG * 8) - 1));
return -1;
}
G_INLINE_FUNC gint
g_bit_nth_msf (gulong mask,
gint nth_bit)
{
if (nth_bit < 0)
if (nth_bit < 0 || G_UNLIKELY (nth_bit > GLIB_SIZEOF_LONG * 8))
nth_bit = GLIB_SIZEOF_LONG * 8;
do
while (nth_bit > 0)
{
nth_bit--;
if (mask & (1UL << nth_bit))
return nth_bit;
}
while (nth_bit > 0);
return -1;
}
G_INLINE_FUNC guint
g_bit_storage (gulong number)
{
#if defined(__GNUC__) && (__GNUC__ >= 4) && defined(__OPTIMIZE__)
return number ? GLIB_SIZEOF_LONG * 8 - __builtin_clzl(number) : 1;
#else
register guint n_bits = 0;
do
@ -313,6 +316,7 @@ g_bit_storage (gulong number)
}
while (number);
return n_bits;
#endif
}
G_INLINE_FUNC void
g_trash_stack_push (GTrashStack **stack_p,

2
tests/Makefile.am
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@ -65,6 +65,7 @@ test_programs = \
atomic-test \
array-test \
base64-test \
bit-test \
$(CXX_TEST) \
child-test \
completion-test \
@ -130,6 +131,7 @@ module_ldadd = $(libgmodule) $(G_MODULE_LIBS) $(progs_ldadd)
atomic_test_LDADD = $(progs_ldadd)
array_test_LDADD = $(progs_ldadd)
base64_test_LDADD = $(progs_ldadd)
bit_test_LDADD = $(progs_ldadd)
bookmarkfile_test_LDADD = $(progs_ldadd)
child_test_LDADD = $(thread_ldadd)
completion_test_LDADD = $(progs_ldadd)

145
tests/bit-test.c Normal file
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@ -0,0 +1,145 @@
#include <glib.h>
#if defined(__GNUC__) && (__GNUC__ >= 4)
# define TEST_BUILTINS 1
#else
# define TEST_BUILTINS 0
#endif
#if TEST_BUILTINS
static gint
builtin_bit_nth_lsf1 (gulong mask, gint nth_bit)
{
if (nth_bit >= 0)
{
if (G_LIKELY (nth_bit < GLIB_SIZEOF_LONG * 8 - 1))
mask &= -(1<<(nth_bit+1));
else
mask = 0;
}
return __builtin_ffsl(mask) - 1;
}
static gint
builtin_bit_nth_lsf2 (gulong mask, gint nth_bit)
{
if (nth_bit >= 0)
{
if (G_LIKELY (nth_bit < GLIB_SIZEOF_LONG * 8 - 1))
mask &= -(1<<(nth_bit+1));
else
mask = 0;
}
return mask ? __builtin_ctzl(mask) : -1;
}
static gint
builtin_bit_nth_msf (gulong mask, gint nth_bit)
{
if (nth_bit >= 0 && nth_bit < GLIB_SIZEOF_LONG * 8)
mask &= (1<<nth_bit)-1;
return mask ? GLIB_SIZEOF_LONG * 8 - 1 - __builtin_clzl(mask) : -1;
}
static guint
builtin_bit_storage (gulong number)
{
return number ? GLIB_SIZEOF_LONG * 8 - __builtin_clzl(number) : 1;
}
#endif
static gint
naive_bit_nth_lsf (gulong mask, gint nth_bit)
{
if (G_UNLIKELY (nth_bit < -1))
nth_bit = -1;
while (nth_bit < ((GLIB_SIZEOF_LONG * 8) - 1))
{
nth_bit++;
if (mask & (1UL << nth_bit))
return nth_bit;
}
return -1;
}
static gint
naive_bit_nth_msf (gulong mask, gint nth_bit)
{
if (nth_bit < 0 || G_UNLIKELY (nth_bit > GLIB_SIZEOF_LONG * 8))
nth_bit = GLIB_SIZEOF_LONG * 8;
while (nth_bit > 0)
{
nth_bit--;
if (mask & (1UL << nth_bit))
return nth_bit;
}
return -1;
}
static guint
naive_bit_storage (gulong number)
{
register guint n_bits = 0;
do
{
n_bits++;
number >>= 1;
}
while (number);
return n_bits;
}
#define TEST(f1, f2, i) \
if (f1 (i) != f2 (i)) { \
g_error (G_STRINGIFY (f1) " (%lu) = %d; " \
G_STRINGIFY (f2) " (%lu) = %d; ", \
i, f1 (i), \
i, f2 (i)); \
return 1; \
}
#define TEST2(f1, f2, i, n) \
if (f1 (i, n) != f2 (i, n)) { \
g_error (G_STRINGIFY (f1) " (%lu, %d) = %d; " \
G_STRINGIFY (f2) " (%lu, %d) = %d; ", \
i, n, f1 (i, n), \
i, n, f2 (i, n)); \
return 1; \
}
int
main (void)
{
gulong i;
gint nth_bit;
/* we loop like this: 0, -1, 1, -2, 2, -3, 3, ... */
for (i = 0; (glong)i < 1500 ; i = -(i+((glong)i>=0))) {
#if TEST_BUILTINS
TEST (naive_bit_storage, builtin_bit_storage, i);
#endif
TEST (naive_bit_storage, g_bit_storage, i);
for (nth_bit = -3; nth_bit <= 2 + GLIB_SIZEOF_LONG * 8; nth_bit++) {
#if TEST_BUILTINS
TEST2 (naive_bit_nth_lsf, builtin_bit_nth_lsf1, i, nth_bit);
TEST2 (naive_bit_nth_lsf, builtin_bit_nth_lsf2, i, nth_bit);
#endif
TEST2 (naive_bit_nth_lsf, g_bit_nth_lsf, i, nth_bit);
#if TEST_BUILTINS
TEST2 (naive_bit_nth_msf, builtin_bit_nth_msf, i, nth_bit);
#endif
TEST2 (naive_bit_nth_msf, g_bit_nth_msf, i, nth_bit);
}
}
return 0;
}