mirror of
https://github.com/superseriousbusiness/gotosocial.git
synced 2024-11-22 11:46:40 +00:00
67 lines
1.4 KiB
Go
67 lines
1.4 KiB
Go
package xsync
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import (
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"math/bits"
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"runtime"
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_ "unsafe"
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)
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// test-only assert()-like flag
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var assertionsEnabled = false
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const (
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// cacheLineSize is used in paddings to prevent false sharing;
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// 64B are used instead of 128B as a compromise between
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// memory footprint and performance; 128B usage may give ~30%
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// improvement on NUMA machines.
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cacheLineSize = 64
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)
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// nextPowOf2 computes the next highest power of 2 of 32-bit v.
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// Source: https://graphics.stanford.edu/~seander/bithacks.html#RoundUpPowerOf2
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func nextPowOf2(v uint32) uint32 {
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if v == 0 {
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return 1
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}
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v--
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v |= v >> 1
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v |= v >> 2
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v |= v >> 4
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v |= v >> 8
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v |= v >> 16
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v++
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return v
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}
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func parallelism() uint32 {
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maxProcs := uint32(runtime.GOMAXPROCS(0))
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numCores := uint32(runtime.NumCPU())
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if maxProcs < numCores {
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return maxProcs
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}
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return numCores
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}
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//go:noescape
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//go:linkname runtime_fastrand runtime.fastrand
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func runtime_fastrand() uint32
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func broadcast(b uint8) uint64 {
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return 0x101010101010101 * uint64(b)
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}
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func firstMarkedByteIndex(w uint64) int {
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return bits.TrailingZeros64(w) >> 3
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}
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// SWAR byte search: may produce false positives, e.g. for 0x0100,
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// so make sure to double-check bytes found by this function.
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func markZeroBytes(w uint64) uint64 {
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return ((w - 0x0101010101010101) & (^w) & 0x8080808080808080)
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}
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func setByte(w uint64, b uint8, idx int) uint64 {
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shift := idx << 3
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return (w &^ (0xff << shift)) | (uint64(b) << shift)
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}
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