internal const val B0_FLAG_RSV3 = 16

  /** Byte 0 mask for the frame opcode. */
  internal const val B0_MASK_OPCODE = 15

  /** Flag in the opcode which indicates a control frame. */
  internal const val OPCODE_FLAG_CONTROL = 8

  /**
   * Byte 1 flag for whether the payload data is masked.
   *
   * If this flag is set, the next four

		return x
	case x < 0:
		return NaN()
	}
	ix := Float64bits(x)
	// normalize x
	exp := int((ix >> shift) & mask)
	if exp == 0 { // subnormal x
		for ix&(1<<shift) == 0 {
			ix <<= 1
			exp--
		}
		exp++
	}
	exp -= bias // unbias exponent
	ix &^= mask << shift
	ix |= 1 << shift
	if exp&1 == 1 { // odd exp, double x to make it even
		ix <<= 1
	}

	mtop := int((logM - 2) / _W) // -2 because the top word of N bits is the (N-1)/W'th word.
	mmask := ^Word(0)
	if mbits := (logM - 1) & (_W - 1); mbits != 0 {
		mmask = (1 << mbits) - 1
	}
	if i > mtop {
		i = mtop
	}
	advance := false
	z = z.setWord(1)
	for ; i >= 0; i-- {
		yi := y[i]
		if i == mtop {
			yi &= mmask
		}
		for j := 0; j < _W; j += n {
			if advance {

	// ITypeImmMask is a mask including only the immediate portion of
	// I-type instructions.
	ITypeImmMask = 0xfff00000

	// JTypeImmMask is a mask including only the immediate portion of
	// J-type instructions.
	JTypeImmMask = 0xfffff000

	// STypeImmMask is a mask including only the immediate portion of
	// S-type instructions.
	STypeImmMask = 0xfe000f80

	// UTypeImmMask is a mask including only the immediate portion of

func (c *pageCache) allocN(npages uintptr) (uintptr, uintptr) {
	i := findBitRange64(c.cache, uint(npages))
	if i >= 64 {
		return 0, 0
	}
	mask := ((uint64(1) << npages) - 1) << i
	scav := sys.OnesCount64(c.scav & mask)
	c.cache &^= mask // mark in-use bits
	c.scav &^= mask  // clear scavenged bits
	return c.base + uintptr(i*pageSize), uintptr(scav) * pageSize
}

// flush empties out unallocated free pages in the given cache

//go:linkname abigen_sync_atomic_OrInt64 sync/atomic.OrInt64
func abigen_sync_atomic_OrInt64(addr *int64, mask int64) (old int64)

//go:linkname abigen_sync_atomic_OrUint64 sync/atomic.OrUint64
func abigen_sync_atomic_OrUint64(addr *uint64, mask uint64) (old uint64)

//go:linkname abigen_sync_atomic_OrUintptr sync/atomic.OrUintptr
func abigen_sync_atomic_OrUintptr(addr *uintptr, mask uintptr) (old uintptr)

	// Considering only the top 4 bits, the conditional instructions use mask=0, value=0,
	// while the unconditional instructions use mask=f, value=f.
	// Prepare a version of x with the condition cleared to 0 in conditional instructions
	// and then assume mask=f during matching.
	const condMask = 0xf0000000
	xNoCond := x
	if x&condMask != condMask {
		xNoCond &^= condMask
	}

the SIGPROF signal in particular.

The non-Go code should not change the signal mask on any threads
created by the Go runtime. If the non-Go code starts new threads
itself, those threads may set the signal mask as they please.

If the non-Go code starts a new thread, changes the signal mask, and
then invokes a Go function in that thread, the Go runtime will

    this.lastInKeyInsertionOrder = null;
    this.size = 0;
    this.mask = tableSize - 1;
    this.modCount = 0;
  }

  /**
   * Finds and removes {@code entry} from the bucket linked lists in both the key-to-value direction
   * and the value-to-key direction.
   */
  private void delete(BiEntry<K, V> entry) {
    int keyBucket = entry.keyHash & mask;
    BiEntry<K, V> prevBucketEntry = null;

type WaitStatus uint32

const (
	mask  = 0x7F
	core  = 0x80
	shift = 8

	exited  = 0
	killed  = 9
	stopped = 0x7F
)

func (w WaitStatus) Exited() bool { return w&mask == exited }

func (w WaitStatus) ExitStatus() int {
	if w&mask != exited {
		return -1
	}
	return int(w >> shift)
}

func (w WaitStatus) Signaled() bool { return w&mask != stopped && w&mask != 0 }