Golang atomic.Or8函数代码示例

// obj is the start of an object with mark mbits.
// If it isn't already marked, mark it and enqueue into gcw.
// base and off are for debugging only and could be removed.
//go:nowritebarrierrec
func greyobject(obj, base, off uintptr, hbits heapBits, span *mspan, gcw *gcWork, objIndex uintptr) {
	// obj should be start of allocation, and so must be at least pointer-aligned.
	if obj&(sys.PtrSize-1) != 0 {
		throw("greyobject: obj not pointer-aligned")
	}
	mbits := span.markBitsForIndex(objIndex)

	if useCheckmark {
		if !mbits.isMarked() {
			printlock()
			print("runtime:greyobject: checkmarks finds unexpected unmarked object obj=", hex(obj), "\n")
			print("runtime: found obj at *(", hex(base), "+", hex(off), ")\n")

			// Dump the source (base) object
			gcDumpObject("base", base, off)

			// Dump the object
			gcDumpObject("obj", obj, ^uintptr(0))

			throw("checkmark found unmarked object")
		}
		if hbits.isCheckmarked(span.elemsize) {
			return
		}
		hbits.setCheckmarked(span.elemsize)
		if !hbits.isCheckmarked(span.elemsize) {
			throw("setCheckmarked and isCheckmarked disagree")
		}
	} else {
		if debug.gccheckmark > 0 && span.isFree(objIndex) {
			print("runtime: marking free object ", hex(obj), " found at *(", hex(base), "+", hex(off), ")\n")
			gcDumpObject("base", base, off)
			gcDumpObject("obj", obj, ^uintptr(0))
			throw("marking free object")
		}

		// If marked we have nothing to do.
		if mbits.isMarked() {
			return
		}
		// mbits.setMarked() // Avoid extra call overhead with manual inlining.
		atomic.Or8(mbits.bytep, mbits.mask)
		// If this is a noscan object, fast-track it to black
		// instead of greying it.
		if !hbits.hasPointers(span.elemsize) {
			gcw.bytesMarked += uint64(span.elemsize)
			return
		}
	}

	// Queue the obj for scanning. The PREFETCH(obj) logic has been removed but
	// seems like a nice optimization that can be added back in.
	// There needs to be time between the PREFETCH and the use.
	// Previously we put the obj in an 8 element buffer that is drained at a rate
	// to give the PREFETCH time to do its work.
	// Use of PREFETCHNTA might be more appropriate than PREFETCH
	if !gcw.putFast(obj) {
		gcw.put(obj)
	}
}

//.........这里部分代码省略.........
	}
	if unsafe.Offsetof(y1.y) != 1 {
		throw("bad offsetof y1.y")
	}
	if unsafe.Sizeof(y1) != 2 {
		throw("bad unsafe.Sizeof y1")
	}

	if timediv(12345*1000000000+54321, 1000000000, &e) != 12345 || e != 54321 {
		throw("bad timediv")
	}

	var z uint32
	z = 1
	if !atomic.Cas(&z, 1, 2) {
		throw("cas1")
	}
	if z != 2 {
		throw("cas2")
	}

	z = 4
	if atomic.Cas(&z, 5, 6) {
		throw("cas3")
	}
	if z != 4 {
		throw("cas4")
	}

	z = 0xffffffff
	if !atomic.Cas(&z, 0xffffffff, 0xfffffffe) {
		throw("cas5")
	}
	if z != 0xfffffffe {
		throw("cas6")
	}

	k = unsafe.Pointer(uintptr(0xfedcb123))
	if sys.PtrSize == 8 {
		k = unsafe.Pointer(uintptr(k) << 10)
	}
	if casp(&k, nil, nil) {
		throw("casp1")
	}
	k1 = add(k, 1)
	if !casp(&k, k, k1) {
		throw("casp2")
	}
	if k != k1 {
		throw("casp3")
	}

	m = [4]byte{1, 1, 1, 1}
	atomic.Or8(&m[1], 0xf0)
	if m[0] != 1 || m[1] != 0xf1 || m[2] != 1 || m[3] != 1 {
		throw("atomicor8")
	}

	*(*uint64)(unsafe.Pointer(&j)) = ^uint64(0)
	if j == j {
		throw("float64nan")
	}
	if !(j != j) {
		throw("float64nan1")
	}

	*(*uint64)(unsafe.Pointer(&j1)) = ^uint64(1)
	if j == j1 {
		throw("float64nan2")
	}
	if !(j != j1) {
		throw("float64nan3")
	}

	*(*uint32)(unsafe.Pointer(&i)) = ^uint32(0)
	if i == i {
		throw("float32nan")
	}
	if i == i {
		throw("float32nan1")
	}

	*(*uint32)(unsafe.Pointer(&i1)) = ^uint32(1)
	if i == i1 {
		throw("float32nan2")
	}
	if i == i1 {
		throw("float32nan3")
	}

	testAtomic64()

	if _FixedStack != round2(_FixedStack) {
		throw("FixedStack is not power-of-2")
	}

	if !checkASM() {
		throw("assembly checks failed")
	}
}

func mapiterinit(t *maptype, h *hmap, it *hiter) {
	// Clear pointer fields so garbage collector does not complain.
	it.key = nil
	it.value = nil
	it.t = nil
	it.h = nil
	it.buckets = nil
	it.bptr = nil
	it.overflow[0] = nil
	it.overflow[1] = nil

	if raceenabled && h != nil {
		callerpc := getcallerpc(unsafe.Pointer(&t))
		racereadpc(unsafe.Pointer(h), callerpc, funcPC(mapiterinit))
	}

	if h == nil || h.count == 0 {
		it.key = nil
		it.value = nil
		return
	}

	if unsafe.Sizeof(hiter{})/sys.PtrSize != 12 {
		throw("hash_iter size incorrect") // see ../../cmd/internal/gc/reflect.go
	}
	it.t = t
	it.h = h

	// grab snapshot of bucket state
	it.B = h.B
	it.buckets = h.buckets
	if t.bucket.kind&kindNoPointers != 0 {
		// Allocate the current slice and remember pointers to both current and old.
		// This preserves all relevant overflow buckets alive even if
		// the table grows and/or overflow buckets are added to the table
		// while we are iterating.
		h.createOverflow()
		it.overflow = *h.overflow
	}

	// decide where to start
	r := uintptr(fastrand())
	if h.B > 31-bucketCntBits {
		r += uintptr(fastrand()) << 31
	}
	it.startBucket = r & (uintptr(1)<<h.B - 1)
	it.offset = uint8(r >> h.B & (bucketCnt - 1))

	// iterator state
	it.bucket = it.startBucket
	it.wrapped = false
	it.bptr = nil

	// Remember we have an iterator.
	// Can run concurrently with another hash_iter_init().
	if old := h.flags; old&(iterator|oldIterator) != iterator|oldIterator {
		atomic.Or8(&h.flags, iterator|oldIterator)
	}

	mapiternext(it)
}

//.........这里部分代码省略.........
	}
	if unsafe.Offsetof(y1.y) != 1 {
		throw("bad offsetof y1.y")
	}
	if unsafe.Sizeof(y1) != 2 {
		throw("bad unsafe.Sizeof y1")
	}

	if timediv(12345*1000000000+54321, 1000000000, &e) != 12345 || e != 54321 {
		throw("bad timediv")
	}

	var z uint32
	z = 1
	if !atomic.Cas(&z, 1, 2) {
		throw("cas1")
	}
	if z != 2 {
		throw("cas2")
	}

	z = 4
	if atomic.Cas(&z, 5, 6) {
		throw("cas3")
	}
	if z != 4 {
		throw("cas4")
	}

	z = 0xffffffff
	if !atomic.Cas(&z, 0xffffffff, 0xfffffffe) {
		throw("cas5")
	}
	if z != 0xfffffffe {
		throw("cas6")
	}

	k = unsafe.Pointer(uintptr(0xfedcb123))
	if sys.PtrSize == 8 {
		k = unsafe.Pointer(uintptr(k) << 10)
	}
	if casp(&k, nil, nil) {
		throw("casp1")
	}
	k1 = add(k, 1)
	if !casp(&k, k, k1) {
		throw("casp2")
	}
	if k != k1 {
		throw("casp3")
	}

	m = [4]byte{1, 1, 1, 1}
	atomic.Or8(&m[1], 0xf0)
	if m[0] != 1 || m[1] != 0xf1 || m[2] != 1 || m[3] != 1 {
		throw("atomicor8")
	}

	*(*uint64)(unsafe.Pointer(&j)) = ^uint64(0)
	if j == j {
		throw("float64nan")
	}
	if !(j != j) {
		throw("float64nan1")
	}

	*(*uint64)(unsafe.Pointer(&j1)) = ^uint64(1)
	if j == j1 {
		throw("float64nan2")
	}
	if !(j != j1) {
		throw("float64nan3")
	}

	*(*uint32)(unsafe.Pointer(&i)) = ^uint32(0)
	if i == i {
		throw("float32nan")
	}
	if i == i {
		throw("float32nan1")
	}

	*(*uint32)(unsafe.Pointer(&i1)) = ^uint32(1)
	if i == i1 {
		throw("float32nan2")
	}
	if i == i1 {
		throw("float32nan3")
	}

	testAtomic64()

	// if _FixedStack != round2(_FixedStack) {
	// 	throw("FixedStack is not power-of-2")
	// }

	if !checkASM() {
		throw("assembly checks failed")
	}
}