Tim Starling
81 linhas
2.6 KiB
C++
81 linhas
2.6 KiB
C++
/*
|
|
+----------------------------------------------------------------------+
|
|
| HipHop for PHP |
|
|
+----------------------------------------------------------------------+
|
|
| Copyright (c) 2010-2013 Facebook, Inc. (http://www.facebook.com) |
|
|
+----------------------------------------------------------------------+
|
|
| This source file is subject to version 3.01 of the PHP license, |
|
|
| that is bundled with this package in the file LICENSE, and is |
|
|
| available through the world-wide-web at the following url: |
|
|
| http://www.php.net/license/3_01.txt |
|
|
| If you did not receive a copy of the PHP license and are unable to |
|
|
| obtain it through the world-wide-web, please send a note to |
|
|
| license@php.net so we can mail you a copy immediately. |
|
|
+----------------------------------------------------------------------+
|
|
*/
|
|
|
|
#ifndef incl_HPHP_BITOPS_H_
|
|
#define incl_HPHP_BITOPS_H_
|
|
|
|
namespace HPHP {
|
|
|
|
// GLIBC doesn't provide an fls primitive. Since we're rolling our own
|
|
// anyway, fix ffs's wacky offset-by-one historical implementation. These
|
|
// guys return success/failure (failure for input of all zeros) and the
|
|
// unoffset bit position in their reference param.
|
|
template<typename I64>
|
|
inline bool ffs64(I64 input, I64 &out) {
|
|
bool retval;
|
|
#if defined(__x86_64__)
|
|
asm volatile (
|
|
"bsfq %2, %1\n\t" // bit scan forward
|
|
"setnz %0\n\t": // zero retval if input == 0
|
|
"=r"(retval), "=r"(out):
|
|
"r"(input):
|
|
"cc"
|
|
);
|
|
#elif defined(__AARCH64EL__)
|
|
asm volatile (
|
|
"rbit %2, %2\n\t" // reverse bits
|
|
"clz %1, %2\n\t" // count leading zeros
|
|
"cmp %1, #64\n\t"
|
|
"cset %0, NE": // return (result != 64)
|
|
"=r"(retval), "=r"(out), "+r"(input):
|
|
:
|
|
"cc"
|
|
);
|
|
#endif
|
|
return retval;
|
|
}
|
|
|
|
template<typename I64>
|
|
inline bool fls64(I64 input, I64 &out) {
|
|
bool retval;
|
|
#if defined(__x86_64__)
|
|
asm volatile (
|
|
"bsrq %2, %1\n\t" // bit scan reverse
|
|
"setnz %0\n\t": // zero retval if input == 0
|
|
"=r"(retval), "=r"(out):
|
|
"r"(input):
|
|
"cc"
|
|
);
|
|
#elif defined(__AARCH64EL__)
|
|
asm volatile (
|
|
"clz %1, %2\n\t" // count leading zeros
|
|
"neg %1, %1\n\t"
|
|
"adds %1, %1, #63\n\t" // result = 63 - (# of leading zeros)
|
|
// "s" suffix sets condition flags
|
|
"cset %0, PL": // return (result >= 0)
|
|
// because result < 0 iff input == 0
|
|
"=r"(retval), "=r"(out):
|
|
"r"(input):
|
|
"cc"
|
|
);
|
|
#endif
|
|
return retval;
|
|
}
|
|
|
|
} // HPHP
|
|
|
|
#endif
|