mirror of
https://github.com/netwide-assembler/nasm.git
synced 2025-10-10 00:25:06 -04:00
c138e6a4b2
On x86-64 platforms, we can rely on BSR not changing the destination operand when the input is zero. Signed-off-by: H. Peter Anvin <hpa@zytor.com>
161 lines
3.6 KiB
C
161 lines
3.6 KiB
C
/* ----------------------------------------------------------------------- *
|
|
*
|
|
* Copyright 1996-2010 The NASM Authors - All Rights Reserved
|
|
* See the file AUTHORS included with the NASM distribution for
|
|
* the specific copyright holders.
|
|
*
|
|
* Redistribution and use in source and binary forms, with or without
|
|
* modification, are permitted provided that the following
|
|
* conditions are met:
|
|
*
|
|
* * Redistributions of source code must retain the above copyright
|
|
* notice, this list of conditions and the following disclaimer.
|
|
* * Redistributions in binary form must reproduce the above
|
|
* copyright notice, this list of conditions and the following
|
|
* disclaimer in the documentation and/or other materials provided
|
|
* with the distribution.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
|
|
* CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
|
|
* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
|
|
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
|
|
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
|
|
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
|
|
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
|
|
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
|
|
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
|
|
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
|
|
* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
|
|
* EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|
|
*
|
|
* ----------------------------------------------------------------------- */
|
|
|
|
#include "compiler.h"
|
|
#include "nasmlib.h"
|
|
|
|
#define ROUND(v, a, w) \
|
|
do { \
|
|
if (v & (((1 << w) - 1) << w)) { \
|
|
a += w; \
|
|
v >>= w; \
|
|
} \
|
|
} while (0)
|
|
|
|
#if defined(__GNUC__) && defined(__x86_64__)
|
|
|
|
int ilog2_32(uint32_t v)
|
|
{
|
|
int n;
|
|
|
|
__asm__("bsrl %1,%0"
|
|
: "=r" (n)
|
|
: "rm" (v), "0" (0));
|
|
return n;
|
|
}
|
|
|
|
#elif defined(__GNUC__) && defined(__i386__)
|
|
|
|
int ilog2_32(uint32_t v)
|
|
{
|
|
int n;
|
|
|
|
__asm__("bsrl %1,%0 ; jnz 1f ; xorl %0,%0\n"
|
|
"1:"
|
|
: "=&r" (n)
|
|
: "rm" (v));
|
|
return n;
|
|
}
|
|
|
|
#elif defined(HAVE_GNUC_4)
|
|
|
|
int ilog2_32(uint32_t v)
|
|
{
|
|
if (!v)
|
|
return 0;
|
|
|
|
return __builtin_clz(v) ^ 31;
|
|
}
|
|
|
|
#else
|
|
|
|
int ilog2_32(uint32_t v)
|
|
{
|
|
int p = 0;
|
|
|
|
ROUND(v, p, 16);
|
|
ROUND(v, p, 8);
|
|
ROUND(v, p, 4);
|
|
ROUND(v, p, 2);
|
|
ROUND(v, p, 1);
|
|
|
|
return p;
|
|
}
|
|
|
|
#endif
|
|
|
|
#if defined(__GNUC__) && defined(__x86_64__)
|
|
|
|
int ilog2_64(uint64_t v)
|
|
{
|
|
uint64_t n;
|
|
|
|
__asm__("bsrq %1,%0"
|
|
: "=r" (n)
|
|
: "rm" (v), "0" (UINT64_C(0)));
|
|
return n;
|
|
}
|
|
|
|
#elif defined(HAVE_GNUC_4)
|
|
|
|
int ilog2_64(uint64_t v)
|
|
{
|
|
if (!v)
|
|
return 0;
|
|
|
|
return __builtin_clzll(v) ^ 63;
|
|
}
|
|
|
|
#else
|
|
|
|
int ilog2_64(uint64_t vv)
|
|
{
|
|
int p = 0;
|
|
uint32_t v;
|
|
|
|
v = vv >> 32;
|
|
if (v)
|
|
p += 32;
|
|
else
|
|
v = vv;
|
|
|
|
ROUND(v, p, 16);
|
|
ROUND(v, p, 8);
|
|
ROUND(v, p, 4);
|
|
ROUND(v, p, 2);
|
|
ROUND(v, p, 1);
|
|
|
|
return p;
|
|
}
|
|
|
|
#endif
|
|
|
|
/*
|
|
* v == 0 ? 0 : is_power2(x) ? ilog2_X(v) : -1
|
|
*/
|
|
int alignlog2_32(uint32_t v)
|
|
{
|
|
if (unlikely(v & (v-1)))
|
|
return -1; /* invalid alignment */
|
|
|
|
return ilog2_32(v);
|
|
}
|
|
|
|
int alignlog2_64(uint64_t v)
|
|
{
|
|
if (unlikely(v & (v-1)))
|
|
return -1; /* invalid alignment */
|
|
|
|
return ilog2_64(v);
|
|
}
|