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OK, this might be a bit silly, but add another popcnt() candidate.

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This commit is contained in:
Peter Wemm 2003-11-06 01:24:25 +00:00
parent 42944f1e2e
commit 6350f49c4a
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=122156
2 changed files with 12 additions and 0 deletions
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6
sys/amd64/amd64/mp_machdep.c
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@ -915,6 +915,12 @@ smp_tlb_shootdown(u_int vector, vm_offset_t addr1, vm_offset_t addr2)
* -mcpu=pentiumpro and -march=pentiumpro then gcc-3.1 will use
* an imull, and in that case it is faster. In most other cases
* it appears slightly slower.
*
* Another variant (also from fortune):
* #define BITCOUNT(x) (((BX_(x)+(BX_(x)>>4)) & 0x0F0F0F0F) % 255)
* #define BX_(x) ((x) - (((x)>>1)&0x77777777) \
* - (((x)>>2)&0x33333333) \
* - (((x)>>3)&0x11111111))
*/
static __inline u_int32_t
popcnt(u_int32_t m)

6
sys/i386/i386/mp_machdep.c
View file

@ -915,6 +915,12 @@ smp_tlb_shootdown(u_int vector, vm_offset_t addr1, vm_offset_t addr2)
* -mcpu=pentiumpro and -march=pentiumpro then gcc-3.1 will use
* an imull, and in that case it is faster. In most other cases
* it appears slightly slower.
*
* Another variant (also from fortune):
* #define BITCOUNT(x) (((BX_(x)+(BX_(x)>>4)) & 0x0F0F0F0F) % 255)
* #define BX_(x) ((x) - (((x)>>1)&0x77777777) \
* - (((x)>>2)&0x33333333) \
* - (((x)>>3)&0x11111111))
*/
static __inline u_int32_t
popcnt(u_int32_t m)