diff options
Diffstat (limited to 'vendor/golang.org/x/sys/unix/affinity_linux.go')
-rw-r--r-- | vendor/golang.org/x/sys/unix/affinity_linux.go | 42 |
1 files changed, 2 insertions, 40 deletions
diff --git a/vendor/golang.org/x/sys/unix/affinity_linux.go b/vendor/golang.org/x/sys/unix/affinity_linux.go index 72afe3338..6e5c81acd 100644 --- a/vendor/golang.org/x/sys/unix/affinity_linux.go +++ b/vendor/golang.org/x/sys/unix/affinity_linux.go @@ -7,6 +7,7 @@ package unix import ( + "math/bits" "unsafe" ) @@ -79,46 +80,7 @@ func (s *CPUSet) IsSet(cpu int) bool { func (s *CPUSet) Count() int { c := 0 for _, b := range s { - c += onesCount64(uint64(b)) + c += bits.OnesCount64(uint64(b)) } return c } - -// onesCount64 is a copy of Go 1.9's math/bits.OnesCount64. -// Once this package can require Go 1.9, we can delete this -// and update the caller to use bits.OnesCount64. -func onesCount64(x uint64) int { - const m0 = 0x5555555555555555 // 01010101 ... - const m1 = 0x3333333333333333 // 00110011 ... - const m2 = 0x0f0f0f0f0f0f0f0f // 00001111 ... - const m3 = 0x00ff00ff00ff00ff // etc. - const m4 = 0x0000ffff0000ffff - - // Implementation: Parallel summing of adjacent bits. - // See "Hacker's Delight", Chap. 5: Counting Bits. - // The following pattern shows the general approach: - // - // x = x>>1&(m0&m) + x&(m0&m) - // x = x>>2&(m1&m) + x&(m1&m) - // x = x>>4&(m2&m) + x&(m2&m) - // x = x>>8&(m3&m) + x&(m3&m) - // x = x>>16&(m4&m) + x&(m4&m) - // x = x>>32&(m5&m) + x&(m5&m) - // return int(x) - // - // Masking (& operations) can be left away when there's no - // danger that a field's sum will carry over into the next - // field: Since the result cannot be > 64, 8 bits is enough - // and we can ignore the masks for the shifts by 8 and up. - // Per "Hacker's Delight", the first line can be simplified - // more, but it saves at best one instruction, so we leave - // it alone for clarity. - const m = 1<<64 - 1 - x = x>>1&(m0&m) + x&(m0&m) - x = x>>2&(m1&m) + x&(m1&m) - x = (x>>4 + x) & (m2 & m) - x += x >> 8 - x += x >> 16 - x += x >> 32 - return int(x) & (1<<7 - 1) -} |