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| author | peter <peter@FreeBSD.org> | 2003-11-06 01:24:25 +0000 |
|---|---|---|
| committer | peter <peter@FreeBSD.org> | 2003-11-06 01:24:25 +0000 |
| commit | be32bf80013e9d5a8db96d9daaa5c555cc972c15 (patch) | |
| tree | 60231ee958121a2bc115413640571fe508927597 /sys | |
| parent | 776db871bd81c1be4a8245d7e02cfd23378f0f9a (diff) | |
| download | FreeBSD-src-be32bf80013e9d5a8db96d9daaa5c555cc972c15.zip FreeBSD-src-be32bf80013e9d5a8db96d9daaa5c555cc972c15.tar.gz | |
OK, this might be a bit silly, but add another popcnt() candidate.
Diffstat (limited to 'sys')
| -rw-r--r-- | sys/amd64/amd64/mp_machdep.c | 6 | ||||
| -rw-r--r-- | sys/i386/i386/mp_machdep.c | 6 |
2 files changed, 12 insertions, 0 deletions
diff --git a/sys/amd64/amd64/mp_machdep.c b/sys/amd64/amd64/mp_machdep.c index a826dd8..f0b1d43 100644 --- a/sys/amd64/amd64/mp_machdep.c +++ b/sys/amd64/amd64/mp_machdep.c @@ -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) diff --git a/sys/i386/i386/mp_machdep.c b/sys/i386/i386/mp_machdep.c index a826dd8..f0b1d43 100644 --- a/sys/i386/i386/mp_machdep.c +++ b/sys/i386/i386/mp_machdep.c @@ -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) |
