diff options
Diffstat (limited to 'src/runtime/mbitmap.go')
| -rw-r--r-- | src/runtime/mbitmap.go | 65 |
1 files changed, 6 insertions, 59 deletions
diff --git a/src/runtime/mbitmap.go b/src/runtime/mbitmap.go index 387fb8535d..f2a5238c31 100644 --- a/src/runtime/mbitmap.go +++ b/src/runtime/mbitmap.go @@ -190,62 +190,7 @@ func (s *mspan) allocBitsForIndex(allocBitIndex uintptr) markBits { return markBits{bytePtr, uint8(1 << whichBit), allocBitIndex} } -// ctzVals contains the count of trailing zeros for the -// index. 0 returns 8 indicating 8 zeros. -var ctzVals = [256]int8{ - 8, 0, 1, 0, 2, 0, 1, 0, - 3, 0, 1, 0, 2, 0, 1, 0, - 4, 0, 1, 0, 2, 0, 1, 0, - 3, 0, 1, 0, 2, 0, 1, 0, - 5, 0, 1, 0, 2, 0, 1, 0, - 3, 0, 1, 0, 2, 0, 1, 0, - 4, 0, 1, 0, 2, 0, 1, 0, - 3, 0, 1, 0, 2, 0, 1, 0, - 6, 0, 1, 0, 2, 0, 1, 0, - 3, 0, 1, 0, 2, 0, 1, 0, - 4, 0, 1, 0, 2, 0, 1, 0, - 3, 0, 1, 0, 2, 0, 1, 0, - 5, 0, 1, 0, 2, 0, 1, 0, - 3, 0, 1, 0, 2, 0, 1, 0, - 4, 0, 1, 0, 2, 0, 1, 0, - 3, 0, 1, 0, 2, 0, 1, 0, - 7, 0, 1, 0, 2, 0, 1, 0, - 3, 0, 1, 0, 2, 0, 1, 0, - 4, 0, 1, 0, 2, 0, 1, 0, - 3, 0, 1, 0, 2, 0, 1, 0, - 5, 0, 1, 0, 2, 0, 1, 0, - 3, 0, 1, 0, 2, 0, 1, 0, - 4, 0, 1, 0, 2, 0, 1, 0, - 3, 0, 1, 0, 2, 0, 1, 0, - 6, 0, 1, 0, 2, 0, 1, 0, - 3, 0, 1, 0, 2, 0, 1, 0, - 4, 0, 1, 0, 2, 0, 1, 0, - 3, 0, 1, 0, 2, 0, 1, 0, - 5, 0, 1, 0, 2, 0, 1, 0, - 3, 0, 1, 0, 2, 0, 1, 0, - 4, 0, 1, 0, 2, 0, 1, 0, - 3, 0, 1, 0, 2, 0, 1, 0} - -// A temporary stand in for the count trailing zero ctz instruction. -// IA bsf works on 64 bit non-zero word. -func ctz64(markBits uint64) uint64 { - ctz8 := ctzVals[markBits&0xff] - if ctz8 != 8 { - return uint64(ctz8) - } else if markBits == 0 { // low byte is zero check fill word. - return 64 // bits in 64 bit word, ensures loop terminates - } - result := uint64(8) - markBits >>= 8 - for ctz8 = ctzVals[markBits&0xff]; ctz8 == 8; ctz8 = ctzVals[markBits&0xff] { - result += 8 - markBits >>= 8 - } - result += uint64(ctz8) - return result -} - -// refillAllocCache takes 8 bytes s.allocBits starting at whichByte +// refillaCache takes 8 bytes s.allocBits starting at whichByte // and negates them so that ctz (count trailing zeros) instructions // can be used. It then places these 8 bytes into the cached 64 bit // s.allocCache. @@ -278,7 +223,8 @@ func (s *mspan) nextFreeIndex() uintptr { } aCache := s.allocCache - bitIndex := ctz64(aCache) + + bitIndex := sys.Ctz64(aCache) for bitIndex == 64 { // Move index to start of next cached bits. sfreeindex = (sfreeindex + 64) &^ (64 - 1) @@ -290,8 +236,9 @@ func (s *mspan) nextFreeIndex() uintptr { // Refill s.allocCache with the next 64 alloc bits. s.refillAllocCache(whichByte) aCache = s.allocCache - bitIndex = ctz64(aCache) - // Nothing was available try again now allocCache has been refilled. + bitIndex = sys.Ctz64(aCache) + // nothing available in cached bits + // grab the next 8 bytes and try again. } result := sfreeindex + uintptr(bitIndex) if result >= snelems { |