generic-library/isa-l
1
0
Fork 0
mirror of https://github.com/intel/isa-l.git synced 2024-12-13 09:52:56 +01:00
Code Issues Projects Releases Wiki Activity

igzip: Optimize routine to find msb

Browse Source 
Change-Id: I40e7898e2139c04f261980ca10886debc917842a
Signed-off-by: Greg Tucker <greg.b.tucker@intel.com>
This commit is contained in:
Greg Tucker 2019-08-08 19:19:00 -07:00
parent 4b33238371
commit e2997062fb
1 changed files with 18 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
igzip/huffman.h
View File

@ -44,11 +44,27 @@
# define inline __inline
#endif //__x86_64__ || __i386__ || _M_X64 || _M_IX86
/**
* @brief Calculate the bit offset of the msb.
* @param val 32-bit unsigned integer input
*
* @returns bit offset of msb starting at 1 for first bit
*/
static inline uint32_t bsr(uint32_t val)
{
uint32_t msb;
#ifdef __LZCNT__
#if defined(_MSC_VER)
unsigned long ret = 0;
if (val != 0) {
_BitScanReverse(&ret, val);
msb = ret + 1;
}
else
msb = 0;
#elif defined( __LZCNT__)
msb = 32 - __lzcnt32(val);
#elif defined(__x86_64__) || defined(__aarch64__)
msb = (val == 0)? 0 : 32 - __builtin_clz(val);
#else
for(msb = 0; val > 0; val >>= 1)
msb++;
@ -63,7 +79,7 @@ static inline uint32_t tzbytecnt(uint64_t val)
#ifdef __BMI__
cnt = __tzcnt_u64(val);
cnt = cnt / 8;
#elif defined(__x86_64__)
#elif defined(__x86_64__) || defined(__aarch64__)
cnt = (val == 0)? 64 : __builtin_ctzll(val);
cnt = cnt / 8;