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qemu/host-utils: Use __builtin_bitreverseN 

Clang has added some builtins for these operations;
use them if available.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Richard Henderson 2020-11-06 10:59:36 -08:00
parent 6d34aa9969
commit 5140d6be5e
1 changed files with 16 additions and 0 deletions
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16
include/qemu/host-utils.h
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@ -272,6 +272,9 @@ static inline int ctpop64(uint64_t val)
*/
static inline uint8_t revbit8(uint8_t x)
{
#if __has_builtin(__builtin_bitreverse8)
return __builtin_bitreverse8(x);
#else
/* Assign the correct nibble position. */
x = ((x & 0xf0) >> 4)
| ((x & 0x0f) << 4);
@ -281,6 +284,7 @@ static inline uint8_t revbit8(uint8_t x)
| ((x & 0x22) << 1)
| ((x & 0x11) << 3);
return x;
#endif
}
/**
@ -289,6 +293,9 @@ static inline uint8_t revbit8(uint8_t x)
*/
static inline uint16_t revbit16(uint16_t x)
{
#if __has_builtin(__builtin_bitreverse16)
return __builtin_bitreverse16(x);
#else
/* Assign the correct byte position. */
x = bswap16(x);
/* Assign the correct nibble position. */
@ -300,6 +307,7 @@ static inline uint16_t revbit16(uint16_t x)
| ((x & 0x2222) << 1)
| ((x & 0x1111) << 3);
return x;
#endif
}
/**
@ -308,6 +316,9 @@ static inline uint16_t revbit16(uint16_t x)
*/
static inline uint32_t revbit32(uint32_t x)
{
#if __has_builtin(__builtin_bitreverse32)
return __builtin_bitreverse32(x);
#else
/* Assign the correct byte position. */
x = bswap32(x);
/* Assign the correct nibble position. */
@ -319,6 +330,7 @@ static inline uint32_t revbit32(uint32_t x)
| ((x & 0x22222222u) << 1)
| ((x & 0x11111111u) << 3);
return x;
#endif
}
/**
@ -327,6 +339,9 @@ static inline uint32_t revbit32(uint32_t x)
*/
static inline uint64_t revbit64(uint64_t x)
{
#if __has_builtin(__builtin_bitreverse64)
return __builtin_bitreverse64(x);
#else
/* Assign the correct byte position. */
x = bswap64(x);
/* Assign the correct nibble position. */
@ -338,6 +353,7 @@ static inline uint64_t revbit64(uint64_t x)
| ((x & 0x2222222222222222ull) << 1)
| ((x & 0x1111111111111111ull) << 3);
return x;
#endif
}
/* Host type specific sizes of these routines. */