throw("xadd64 failed")
	}
	if atomic.Load64(&test_z64) != (2<<40)+2 {
		throw("xadd64 failed")
	}
	if atomic.Xchg64(&test_z64, (3<<40)+3) != (2<<40)+2 {
		throw("xchg64 failed")
	}
	if atomic.Load64(&test_z64) != (3<<40)+3 {
		throw("xchg64 failed")
	}
}

func check() {
	var (
		a     int8
		b     uint8
		c     int16
		d     uint16
		e     int32

	shouldPanic(t, "Loadint64", func() { atomic.Loadint64(p64) })
	shouldPanic(t, "Store64", func() { atomic.Store64(up64, 0) })
	shouldPanic(t, "Xadd64", func() { atomic.Xadd64(up64, 1) })
	shouldPanic(t, "Xchg64", func() { atomic.Xchg64(up64, 1) })
	shouldPanic(t, "Cas64", func() { atomic.Cas64(up64, 1, 2) })
}

func TestAnd8(t *testing.T) {
	// Basic sanity check.
	x := uint8(0xff)
	for i := uint8(0); i < 8; i++ {

//go:noescape
func Cas64(addr *uint64, old, new uint64) bool

//go:noescape
func CasRel(addr *uint32, old, new uint32) bool

//go:noescape
func Xadd64(addr *uint64, delta int64) uint64

//go:noescape
func Xchg64(addr *uint64, v uint64) uint64

//go:noescape
func Load64(addr *uint64) uint64

//go:noescape
func Store8(addr *uint8, v uint8)

//go:noescape

TEXT ·Xaddint64(SB),NOSPLIT,$0-20
	JMP	·Xadd64(SB)

TEXT ·Casp1(SB),NOSPLIT,$0-13
	JMP	·Cas(SB)

TEXT ·Xchgint32(SB),NOSPLIT,$0-12
	JMP	·Xchg(SB)

TEXT ·Xchgint64(SB),NOSPLIT,$0-20
	JMP	·Xchg64(SB)

TEXT ·Xchguintptr(SB),NOSPLIT,$0-12
	JMP	·Xchg(SB)

TEXT ·StorepNoWB(SB),NOSPLIT,$0-8
	JMP	·Store(SB)

TEXT ·StoreRel(SB),NOSPLIT,$0-8
	JMP	·Store(SB)

	return Cas64(&u.value, old, new)
}

// Swap replaces u's value with new, returning
// u's value before the replacement.
//
//go:nosplit
func (u *Uint64) Swap(value uint64) uint64 {
	return Xchg64(&u.value, value)
}

// Add adds delta to u atomically, returning
// the new updated value.
//
// This operation wraps around in the usual
// two's-complement way.
//
//go:nosplit

	alias("sync/atomic", "SwapInt64", "internal/runtime/atomic", "Xchg64", all...)
	alias("sync/atomic", "SwapUint32", "internal/runtime/atomic", "Xchg", all...)
	alias("sync/atomic", "SwapUint64", "internal/runtime/atomic", "Xchg64", all...)
	alias("sync/atomic", "SwapUintptr", "internal/runtime/atomic", "Xchg", p4...)
	alias("sync/atomic", "SwapUintptr", "internal/runtime/atomic", "Xchg64", p8...)

// license that can be found in the LICENSE file.

package rand

import (
	"errors"
	"internal/byteorder"
	"math/bits"
)

// https://numpy.org/devdocs/reference/random/upgrading-pcg64.html
// https://github.com/imneme/pcg-cpp/commit/871d0494ee9c9a7b7c43f753e3d8ca47c26f8005

// A PCG is a PCG generator with 128 bits of internal state.
// A zero PCG is equivalent to NewPCG(0, 0).
type PCG struct {