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host-utils: Add revbit functions

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Backports commit 652a4b7e736f432a6809d1d2b52d169ab0b9aa3b from qemu.
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Richard Henderson 2018-02-11 01:55:25 -05:00 committed by Lioncash
parent eb5ed2a844
commit a5d6a31d69
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GPG key ID: 4E3C3CC1031BA9C7
1 changed files with 77 additions and 0 deletions
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77
qemu/include/qemu/host-utils.h
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@ -26,6 +26,7 @@
#define HOST_UTILS_H 1
#include "qemu/compiler.h" /* QEMU_GNUC_PREREQ */
#include "qemu/bswap.h"
#include <limits.h>
#ifdef CONFIG_INT128
@ -361,6 +362,80 @@ static inline int ctpop64(uint64_t val)
#endif
}
/**
* revbit8 - reverse the bits in an 8-bit value.
* @x: The value to modify.
*/
static inline uint8_t revbit8(uint8_t x)
{
/* Assign the correct nibble position. */
x = ((x & 0xf0) >> 4)
| ((x & 0x0f) << 4);
/* Assign the correct bit position. */
x = ((x & 0x88) >> 3)
| ((x & 0x44) >> 1)
| ((x & 0x22) << 1)
| ((x & 0x11) << 3);
return x;
}
/**
* revbit16 - reverse the bits in a 16-bit value.
* @x: The value to modify.
*/
static inline uint16_t revbit16(uint16_t x)
{
/* Assign the correct byte position. */
x = bswap16(x);
/* Assign the correct nibble position. */
x = ((x & 0xf0f0) >> 4)
| ((x & 0x0f0f) << 4);
/* Assign the correct bit position. */
x = ((x & 0x8888) >> 3)
| ((x & 0x4444) >> 1)
| ((x & 0x2222) << 1)
| ((x & 0x1111) << 3);
return x;
}
/**
* revbit32 - reverse the bits in a 32-bit value.
* @x: The value to modify.
*/
static inline uint32_t revbit32(uint32_t x)
{
/* Assign the correct byte position. */
x = bswap32(x);
/* Assign the correct nibble position. */
x = ((x & 0xf0f0f0f0u) >> 4)
| ((x & 0x0f0f0f0fu) << 4);
/* Assign the correct bit position. */
x = ((x & 0x88888888u) >> 3)
| ((x & 0x44444444u) >> 1)
| ((x & 0x22222222u) << 1)
| ((x & 0x11111111u) << 3);
return x;
}
/**
* revbit64 - reverse the bits in a 64-bit value.
* @x: The value to modify.
*/
static inline uint64_t revbit64(uint64_t x)
{
/* Assign the correct byte position. */
x = bswap64(x);
/* Assign the correct nibble position. */
x = ((x & 0xf0f0f0f0f0f0f0f0ull) >> 4)
| ((x & 0x0f0f0f0f0f0f0f0full) << 4);
/* Assign the correct bit position. */
x = ((x & 0x8888888888888888ull) >> 3)
| ((x & 0x4444444444444444ull) >> 1)
| ((x & 0x2222222222222222ull) << 1)
| ((x & 0x1111111111111111ull) << 3);
return x;
}
/* Host type specific sizes of these routines. */
#if ULONG_MAX == UINT32_MAX
@ -369,12 +444,14 @@ static inline int ctpop64(uint64_t val)
# define clol clo32
# define ctol cto32
# define ctpopl ctpop32
# define revbitl revbit32
#elif ULONG_MAX == UINT64_MAX
# define clzl clz64
# define ctzl ctz64
# define clol clo64
# define ctol cto64
# define ctpopl ctpop64
# define revbitl revbit64
#else
# error Unknown sizeof long
#endif