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utils: optimize for x86_64 with some inline asm

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64bit x86 has native 64x64->128 bit multiply that we can use with some inline
assembler to speed up large multiplications.
Use bsr to find the number of leading zeros more efficiently.
This commit is contained in:
Wim Taymans 2009-08-28 12:43:43 +02:00
parent 0ef7a5af52
commit d8911f269f
1 changed files with 40 additions and 0 deletions
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40
gst/gstutils.c
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@ -204,6 +204,16 @@ typedef union
} l;
} GstUInt64;
#if defined (__x86_64__) && defined (__GNUC__)
static void
gst_util_uint64_mul_uint64 (GstUInt64 * c1, GstUInt64 * c0, guint64 arg1,
guint64 arg2)
{
__asm__ __volatile__ ("mul %3":"=a" (c0->ll), "=d" (c1->ll)
:"a" (arg1), "g" (arg2)
);
}
#else /* defined (__x86_64__) */
/* multiply two 64-bit unsigned ints into a 128-bit unsigned int. the high
* and low 64 bits of the product are placed in c1 and c0 respectively.
* this operation cannot overflow. */
@ -246,8 +256,21 @@ gst_util_uint64_mul_uint64 (GstUInt64 * c1, GstUInt64 * c0, guint64 arg1,
* the high words of a1 and b0 to b1, the result is c1. */
c1->ll = (guint64) v.l.high * n.l.high + c1->l.high + a1.l.high + b0.l.high;
}
#endif /* defined (__x86_64__) */
/* count leading zeros */
#if defined (__x86_64__) && defined (__GNUC__)
static guint
gst_util_clz (guint32 val)
{
guint s;
__asm__ __volatile__ ("bsrl %0, %0 \n\t"
"xor $31, %0 \n\t":"=r" (s):"0" (val)
);
return s;
}
#else /* defined (__x86_64__) */
static guint
gst_util_clz (guint32 val)
{
@ -266,6 +289,7 @@ gst_util_clz (guint32 val)
return s;
}
#endif /* defined (__x86_64__) */
/* based on Hacker's Delight p152 */
static guint64
@ -329,6 +353,21 @@ gst_util_div128_64 (GstUInt64 c1, GstUInt64 c0, guint64 denom)
/* multiply a 64-bit unsigned int by a 32-bit unsigned int into a 96-bit
* unsigned int. the high 64 bits and low 32 bits of the product are
* placed in c1 and c0 respectively. this operation cannot overflow. */
#if defined (__x86_64__) && defined (__GNUC__)
static void
gst_util_uint64_mul_uint32 (GstUInt64 * c1, GstUInt64 * c0, guint64 arg1,
guint32 arg2)
{
__asm__ __volatile__ ("mul %%rcx \n\t"
"mov %%rax, %%rcx \n\t"
"shl $32, %%rdx \n\t"
"shr $32, %%rcx \n\t"
"or %%rcx, %%rdx \n\t"
"and $0xffffffff, %%eax \n\t":"=a" (c0->ll), "=d" (c1->ll)
:"a" (arg1), "c" ((guint64) arg2)
);
}
#else /* defined (__x86_64__) */
static void
gst_util_uint64_mul_uint32 (GstUInt64 * c1, GstUInt64 * c0, guint64 arg1,
guint32 arg2)
@ -341,6 +380,7 @@ gst_util_uint64_mul_uint32 (GstUInt64 * c1, GstUInt64 * c0, guint64 arg1,
c1->ll = (guint64) a.l.high * arg2 + c0->l.high;
c0->l.high = 0;
}
#endif /* defined (__x86_64__) */
/* divide a 96-bit unsigned int by a 32-bit unsigned int when we know the
* quotient fits into 64 bits. the high 64 bits and low 32 bits of the