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HV:treewide:Update return type for bit operations fls and clz

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Change the return type of function fls and clz as uint16_t;
When the input is zero, INVALID_BIT_INDEX is returned;
Update temporary variable type and return value check of caller
when it call fls or clz;
When input value is zero, clz returns 32 directly.

V1-->V2:
        INVALID_BIT_INDEX instead of INVALID_NUMBER;
        Add type conversion as needed;
        Add "U/UL" for constant value as needed;
        Codeing style fixing.
V2-->V3:
       Use type conversion to remove side effect of
       the variable which stores fls/clz return value;
       fls return INVALID_BIT_INDEX directly when the
       input value is zero.
V3-->v4:
       Clean up comments for fls.

Note: For instruction "bsrl", destination register value
      is undefined when source register value is zero.

Signed-off-by: Xiangyang Wu <xiangyang.wu@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>
This commit is contained in:
Xiangyang Wu
2018-07-02 13:48:11 +08:00
committed by lijinxia
parent 4110f3a87f
commit 13d354e7a6
3 changed files with 41 additions and 23 deletions
Download Patch File Download Diff File Expand all files Collapse all files

40
hypervisor/include/lib/bits.h
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@@ -31,6 +31,14 @@
#define BITS_H
#define BUS_LOCK "lock ; "
/**
*
* INVALID_BIT_INDEX means when input paramter is zero,
* bit operations function can't find bit set and return
* the invalid bit index directly.
*
**/
#define INVALID_BIT_INDEX 0xffffU
/**
*
@@ -38,28 +46,32 @@
* return the bit index of that bit.
*
* Bits are numbered starting at 0,the least significant bit.
* A return value of -1 means that the argument was zero.
* A return value of INVALID_BIT_INDEX means return value is
* invalid bit index when the input argument was zero.
*
* Examples:
* fls (0x0) = -1
* fls (0x0) = INVALID_BIT_INDEX
* fls (0x01) = 0
* fls (0xf0) = 7
* fls (0x80) = 7
* ...
* fls (0x80000001) = 31
*
* @param value: 'unsigned int' type value
* @param value: 'uint32_t' type value
*
* @return value: zero-based bit index, -1 means 'value' was zero.
* @return value: zero-based bit index, INVALID_BIT_INDEX means
* when 'value' was zero, bit operations function can't find bit
* set and return the invalid bit index directly.
*
* **/
static inline int fls(unsigned int value)
static inline uint16_t fls(uint32_t value)
{
int ret;
uint32_t ret = 0U;
if (value == 0U)
return (INVALID_BIT_INDEX);
asm volatile("bsrl %1,%0"
: "=r" (ret)
: "rm" (value), "0" (-1));
return ret;
: "rm" (value));
return (uint16_t)ret;
}
static inline int fls64(unsigned long value)
@@ -124,9 +136,13 @@ static inline int ffz64(unsigned long value)
*
* @return The number of leading zeros in 'value'.
*/
static inline int clz(unsigned int value)
static inline uint16_t clz(uint32_t value)
{
return (31 - fls(value));
if (value == 0U)
return 32U;
else{
return (31U - fls(value));
}
}
/**