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utils: Use gcc's __uint128_t for 64bit unsigned integer scaling

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This is available in newer gcc releases and it should only exist
on platforms that provide some native 128bit integer arithmetic
instructions.

The x86-64 assembly for this is still kept for non-gcc compilers
that don't provide __uint128_t magic.
This commit is contained in:
Sebastian Dröge 2009-09-09 14:53:16 +02:00
parent 575e50fbbc
commit 8d1aeeb2af
2 changed files with 52 additions and 4 deletions
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16
configure.ac
View file

@ -346,6 +346,22 @@ dnl *** checks for structures ***
dnl *** checks for compiler characteristics ***
dnl check if the compiler supports __uint128_t (gcc)
AC_CACHE_CHECK(for __uint128_t, gst_cv_uint128_t,
AC_TRY_COMPILE([ ], [
__uint128_t u = 0;
return 0;
], [
gst_cv_uint128_t=yes
], [
gst_cv_uint128_t=no
])
)
if test x$gst_cv_uint128_t = xyes; then
AC_DEFINE(HAVE_UINT128_T, 1, [Have __uint128_t type])
fi
OPT_CFLAGS=
dnl Check for some compiler flags that optimize our code.
if test "x$GCC" = xyes; then

40
gst/gstutils.c
View file

@ -189,6 +189,7 @@ gst_util_gdouble_to_guint64 (gdouble value)
return ((guint64) ((gint64) value));
}
#ifndef HAVE_UINT128_T
/* convenience struct for getting high and low uint32 parts of
* a guint64 */
typedef union
@ -382,8 +383,39 @@ gst_util_uint64_scale_uint64_unchecked (guint64 val, guint64 num,
/* compute quotient, fits in 64 bits */
return gst_util_div128_64 (c1, c0, denom);
}
#else
#if !defined (__x86_64__)
#define GST_MAXUINT128 ((__uint128_t) -1)
static guint64
gst_util_uint64_scale_uint64_unchecked (guint64 val, guint64 num,
guint64 denom, guint64 correct)
{
__uint128_t tmp;
/* Calculate val * num */
tmp = ((__uint128_t) val) * ((__uint128_t) num);
/* overflow checks */
if (G_UNLIKELY (GST_MAXUINT128 - correct < tmp))
return G_MAXUINT64;
/* perform rounding correction */
tmp += correct;
/* Divide by denom */
tmp /= denom;
/* if larger than G_MAXUINT64 --> overflow */
if (G_UNLIKELY (tmp > G_MAXUINT64))
return G_MAXUINT64;
/* compute quotient, fits in 64 bits */
return (guint64) tmp;
}
#endif
#if !defined (__x86_64__) && !defined (HAVE_UINT128_T)
static inline void
gst_util_uint64_mul_uint32 (GstUInt64 * c1, GstUInt64 * c0, guint64 arg1,
guint32 arg2)
@ -442,7 +474,7 @@ _gst_util_uint64_scale (guint64 val, guint64 num, guint64 denom,
return val;
/* on 64bits we always use a full 128bits multipy/division */
#if !defined (__x86_64__)
#if !defined (__x86_64__) && !defined (HAVE_UINT128_T)
/* denom is low --> try to use 96 bit muldiv */
if (G_LIKELY (denom <= G_MAXUINT32)) {
/* num is low --> use 96 bit muldiv */
@ -455,7 +487,7 @@ _gst_util_uint64_scale (guint64 val, guint64 num, guint64 denom,
return gst_util_uint64_scale_uint32_unchecked (num, (guint32) val,
(guint32) denom, correct);
}
#endif /* !defined (__x86_64__) */
#endif /* !defined (__x86_64__) && !defined (HAVE_UINT128_T) */
/* val is high and num is high --> use 128-bit muldiv */
return gst_util_uint64_scale_uint64_unchecked (val, num, denom, correct);
@ -560,7 +592,7 @@ _gst_util_uint64_scale_int (guint64 val, gint num, gint denom, gint correct)
return val / (guint64) denom;
}
#if !defined (__x86_64__)
#if !defined (__x86_64__) && !defined (HAVE_UINT128_T)
/* num and denom are not negative so casts are OK */
return gst_util_uint64_scale_uint32_unchecked (val, (guint32) num,
(guint32) denom, (guint32) correct);