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qemu/host-utils.h: Add clz and ctz functions for lower-bit integers

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This is for use in the RISC-V vclz and vctz instructions (implemented in
proceeding commit).

Signed-off-by: Kiran Ostrolenk <kiran.ostrolenk@codethink.co.uk>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230428144757.57530-11-lawrence.hunter@codethink.co.uk>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Kiran Ostrolenk 2023-04-28 15:47:48 +01:00 • committed by Richard Henderson
parent 8841c815a9
commit 31fe256d32
1 changed files with 54 additions and 0 deletions
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54
include/qemu/host-utils.h
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@ -107,6 +107,36 @@ static inline uint64_t muldiv64(uint64_t a, uint32_t b, uint32_t c)
} }
#endif #endif
/**
* clz8 - count leading zeros in a 8-bit value.
* @val: The value to search
*
* Returns 8 if the value is zero. Note that the GCC builtin is
* undefined if the value is zero.
*
* Note that the GCC builtin will upcast its argument to an `unsigned int`
* so this function subtracts off the number of prepended zeroes.
*/
static inline int clz8(uint8_t val)
{
return val ? __builtin_clz(val) - 24 : 8;
}
/**
* clz16 - count leading zeros in a 16-bit value.
* @val: The value to search
*
* Returns 16 if the value is zero. Note that the GCC builtin is
* undefined if the value is zero.
*
* Note that the GCC builtin will upcast its argument to an `unsigned int`
* so this function subtracts off the number of prepended zeroes.
*/
static inline int clz16(uint16_t val)
{
return val ? __builtin_clz(val) - 16 : 16;
}
/** /**
* clz32 - count leading zeros in a 32-bit value. * clz32 - count leading zeros in a 32-bit value.
* @val: The value to search * @val: The value to search
@ -153,6 +183,30 @@ static inline int clo64(uint64_t val)
return clz64(~val); return clz64(~val);
} }
/**
* ctz8 - count trailing zeros in a 8-bit value.
* @val: The value to search
*
* Returns 8 if the value is zero. Note that the GCC builtin is
* undefined if the value is zero.
*/
static inline int ctz8(uint8_t val)
{
return val ? __builtin_ctz(val) : 8;
}
/**
* ctz16 - count trailing zeros in a 16-bit value.
* @val: The value to search
*
* Returns 16 if the value is zero. Note that the GCC builtin is
* undefined if the value is zero.
*/
static inline int ctz16(uint16_t val)
{
return val ? __builtin_ctz(val) : 16;
}
/** /**
* ctz32 - count trailing zeros in a 32-bit value. * ctz32 - count trailing zeros in a 32-bit value.
* @val: The value to search * @val: The value to search