Revert "This is a speculative chain of reverts to improve a Chrome"

src/builtins/builtins-sharedarraybuffer.cc

Index: src/builtins/builtins-sharedarraybuffer.cc
diff --git a/src/builtins/builtins-sharedarraybuffer.cc b/src/builtins/builtins-sharedarraybuffer.cc
index d2b9f1efa96b4bbfc2315986f9f793205b0b3869..3c909a91e9d3bde61742a21581cf57072e05563a 100644
--- a/src/builtins/builtins-sharedarraybuffer.cc
+++ b/src/builtins/builtins-sharedarraybuffer.cc
@@ -2,10 +2,19 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "src/base/macros.h"
+#include "src/base/platform/mutex.h"
+#include "src/base/platform/time.h"
 #include "src/builtins/builtins-utils.h"
 #include "src/builtins/builtins.h"
 #include "src/code-factory.h"
 #include "src/code-stub-assembler.h"
+#include "src/conversions-inl.h"
+#include "src/counters.h"
+#include "src/factory.h"
+#include "src/futex-emulation.h"
+#include "src/globals.h"
+#include "src/objects-inl.h"
 
 namespace v8 {
 namespace internal {
@@ -337,5 +346,601 @@ TF_BUILTIN(AtomicsExchange, SharedArrayBufferBuiltinsAssembler) {
         // || V8_TARGET_ARCH_PPC || V8_TARGET_ARCH_S390 || V8_TARGET_ARCH_S390X
 }
 
+inline bool AtomicIsLockFree(uint32_t size) {
+  return size == 1 || size == 2 || size == 4;
+}
+
+// ES #sec-atomics.islockfree
+BUILTIN(AtomicsIsLockFree) {
+  HandleScope scope(isolate);
+  Handle<Object> size = args.atOrUndefined(isolate, 1);
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, size, Object::ToNumber(size));
+  return *isolate->factory()->ToBoolean(AtomicIsLockFree(size->Number()));
+}
+
+// ES #sec-validatesharedintegertypedarray
+MUST_USE_RESULT MaybeHandle<JSTypedArray> ValidateSharedIntegerTypedArray(
+    Isolate* isolate, Handle<Object> object, bool only_int32 = false) {
+  if (object->IsJSTypedArray()) {
+    Handle<JSTypedArray> typed_array = Handle<JSTypedArray>::cast(object);
+    if (typed_array->GetBuffer()->is_shared()) {
+      if (only_int32) {
+        if (typed_array->type() == kExternalInt32Array) return typed_array;
+      } else {
+        if (typed_array->type() != kExternalFloat32Array &&
+            typed_array->type() != kExternalFloat64Array &&
+            typed_array->type() != kExternalUint8ClampedArray)
+          return typed_array;
+      }
+    }
+  }
+
+  THROW_NEW_ERROR(
+      isolate,
+      NewTypeError(only_int32 ? MessageTemplate::kNotInt32SharedTypedArray
+                              : MessageTemplate::kNotIntegerSharedTypedArray,
+                   object),
+      JSTypedArray);
+}
+
+// ES #sec-validateatomicaccess
+// ValidateAtomicAccess( typedArray, requestIndex )
+MUST_USE_RESULT Maybe<size_t> ValidateAtomicAccess(
+    Isolate* isolate, Handle<JSTypedArray> typed_array,
+    Handle<Object> request_index) {
+  // TOOD(v8:5961): Use ToIndex for indexes
+  ASSIGN_RETURN_ON_EXCEPTION_VALUE(isolate, request_index,
+                                   Object::ToNumber(request_index),
+                                   Nothing<size_t>());
+  Handle<Object> offset;
+  ASSIGN_RETURN_ON_EXCEPTION_VALUE(isolate, offset,
+                                   Object::ToInteger(isolate, request_index),
+                                   Nothing<size_t>());
+  if (!request_index->SameValue(*offset)) {
+    isolate->Throw(*isolate->factory()->NewRangeError(
+        MessageTemplate::kInvalidAtomicAccessIndex));
+    return Nothing<size_t>();
+  }
+  size_t access_index;
+  uint32_t length = typed_array->length_value();
+  if (!TryNumberToSize(*request_index, &access_index) ||
+      access_index >= length) {
+    isolate->Throw(*isolate->factory()->NewRangeError(
+        MessageTemplate::kInvalidAtomicAccessIndex));
+    return Nothing<size_t>();
+  }
+  return Just<size_t>(access_index);
+}
+
+// ES #sec-atomics.wake
+// Atomics.wake( typedArray, index, count )
+BUILTIN(AtomicsWake) {
+  HandleScope scope(isolate);
+  Handle<Object> array = args.atOrUndefined(isolate, 1);
+  Handle<Object> index = args.atOrUndefined(isolate, 2);
+  Handle<Object> count = args.atOrUndefined(isolate, 3);
+
+  Handle<JSTypedArray> sta;
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
+      isolate, sta, ValidateSharedIntegerTypedArray(isolate, array, true));
+
+  Maybe<size_t> maybe_index = ValidateAtomicAccess(isolate, sta, index);
+  if (maybe_index.IsNothing()) return isolate->heap()->exception();
+  size_t i = maybe_index.FromJust();
+
+  uint32_t c;
+  if (count->IsUndefined(isolate)) {
+    c = kMaxUInt32;
+  } else {
+    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, count,
+                                       Object::ToInteger(isolate, count));
+    double count_double = count->Number();
+    if (count_double < 0)
+      count_double = 0;
+    else if (count_double > kMaxUInt32)
+      count_double = kMaxUInt32;
+    c = static_cast<uint32_t>(count_double);
+  }
+
+  Handle<JSArrayBuffer> array_buffer = sta->GetBuffer();
+  size_t addr = (i << 2) + NumberToSize(sta->byte_offset());
+
+  return FutexEmulation::Wake(isolate, array_buffer, addr, c);
+}
+
+// ES #sec-atomics.wait
+// Atomics.wait( typedArray, index, value, timeout )
+BUILTIN(AtomicsWait) {
+  HandleScope scope(isolate);
+  Handle<Object> array = args.atOrUndefined(isolate, 1);
+  Handle<Object> index = args.atOrUndefined(isolate, 2);
+  Handle<Object> value = args.atOrUndefined(isolate, 3);
+  Handle<Object> timeout = args.atOrUndefined(isolate, 4);
+
+  Handle<JSTypedArray> sta;
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
+      isolate, sta, ValidateSharedIntegerTypedArray(isolate, array, true));
+
+  Maybe<size_t> maybe_index = ValidateAtomicAccess(isolate, sta, index);
+  if (maybe_index.IsNothing()) return isolate->heap()->exception();
+  size_t i = maybe_index.FromJust();
+
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, value,
+                                     Object::ToInt32(isolate, value));
+  int32_t value_int32 = NumberToInt32(*value);
+
+  double timeout_number;
+  if (timeout->IsUndefined(isolate)) {
+    timeout_number = isolate->heap()->infinity_value()->Number();
+  } else {
+    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, timeout,
+                                       Object::ToNumber(timeout));
+    timeout_number = timeout->Number();
+    if (std::isnan(timeout_number))
+      timeout_number = isolate->heap()->infinity_value()->Number();
+    else if (timeout_number < 0)
+      timeout_number = 0;
+  }
+
+  if (!isolate->allow_atomics_wait()) {
+    THROW_NEW_ERROR_RETURN_FAILURE(
+        isolate, NewTypeError(MessageTemplate::kAtomicsWaitNotAllowed));
+  }
+
+  Handle<JSArrayBuffer> array_buffer = sta->GetBuffer();
+  size_t addr = (i << 2) + NumberToSize(sta->byte_offset());
+
+  return FutexEmulation::Wait(isolate, array_buffer, addr, value_int32,
+                              timeout_number);
+}
+
+namespace {
+
+#if V8_CC_GNU
+
+template <typename T>
+inline T CompareExchangeSeqCst(T* p, T oldval, T newval) {
+  (void)__atomic_compare_exchange_n(p, &oldval, newval, 0, __ATOMIC_SEQ_CST,
+                                    __ATOMIC_SEQ_CST);
+  return oldval;
+}
+
+template <typename T>
+inline T AddSeqCst(T* p, T value) {
+  return __atomic_fetch_add(p, value, __ATOMIC_SEQ_CST);
+}
+
+template <typename T>
+inline T SubSeqCst(T* p, T value) {
+  return __atomic_fetch_sub(p, value, __ATOMIC_SEQ_CST);
+}
+
+template <typename T>
+inline T AndSeqCst(T* p, T value) {
+  return __atomic_fetch_and(p, value, __ATOMIC_SEQ_CST);
+}
+
+template <typename T>
+inline T OrSeqCst(T* p, T value) {
+  return __atomic_fetch_or(p, value, __ATOMIC_SEQ_CST);
+}
+
+template <typename T>
+inline T XorSeqCst(T* p, T value) {
+  return __atomic_fetch_xor(p, value, __ATOMIC_SEQ_CST);
+}
+
+#elif V8_CC_MSVC
+
+#define InterlockedCompareExchange32 _InterlockedCompareExchange
+#define InterlockedExchange32 _InterlockedExchange
+#define InterlockedExchangeAdd32 _InterlockedExchangeAdd
+#define InterlockedAnd32 _InterlockedAnd
+#define InterlockedOr32 _InterlockedOr
+#define InterlockedXor32 _InterlockedXor
+#define InterlockedExchangeAdd16 _InterlockedExchangeAdd16
+#define InterlockedCompareExchange8 _InterlockedCompareExchange8
+#define InterlockedExchangeAdd8 _InterlockedExchangeAdd8
+
+#define ATOMIC_OPS(type, suffix, vctype)                                    \
+  inline type AddSeqCst(type* p, type value) {                              \
+    return InterlockedExchangeAdd##suffix(reinterpret_cast<vctype*>(p),     \
+                                          bit_cast<vctype>(value));         \
+  }                                                                         \
+  inline type SubSeqCst(type* p, type value) {                              \
+    return InterlockedExchangeAdd##suffix(reinterpret_cast<vctype*>(p),     \
+                                          -bit_cast<vctype>(value));        \
+  }                                                                         \
+  inline type AndSeqCst(type* p, type value) {                              \
+    return InterlockedAnd##suffix(reinterpret_cast<vctype*>(p),             \
+                                  bit_cast<vctype>(value));                 \
+  }                                                                         \
+  inline type OrSeqCst(type* p, type value) {                               \
+    return InterlockedOr##suffix(reinterpret_cast<vctype*>(p),              \
+                                 bit_cast<vctype>(value));                  \
+  }                                                                         \
+  inline type XorSeqCst(type* p, type value) {                              \
+    return InterlockedXor##suffix(reinterpret_cast<vctype*>(p),             \
+                                  bit_cast<vctype>(value));                 \
+  }                                                                         \
+  inline type CompareExchangeSeqCst(type* p, type oldval, type newval) {    \
+    return InterlockedCompareExchange##suffix(reinterpret_cast<vctype*>(p), \
+                                              bit_cast<vctype>(newval),     \
+                                              bit_cast<vctype>(oldval));    \
+  }
+
+ATOMIC_OPS(int8_t, 8, char)
+ATOMIC_OPS(uint8_t, 8, char)
+ATOMIC_OPS(int16_t, 16, short)  /* NOLINT(runtime/int) */
+ATOMIC_OPS(uint16_t, 16, short) /* NOLINT(runtime/int) */
+ATOMIC_OPS(int32_t, 32, long)   /* NOLINT(runtime/int) */
+ATOMIC_OPS(uint32_t, 32, long)  /* NOLINT(runtime/int) */
+
+#undef ATOMIC_OPS_INTEGER
+#undef ATOMIC_OPS
+
+#undef InterlockedCompareExchange32
+#undef InterlockedExchange32
+#undef InterlockedExchangeAdd32
+#undef InterlockedAnd32
+#undef InterlockedOr32
+#undef InterlockedXor32
+#undef InterlockedExchangeAdd16
+#undef InterlockedCompareExchange8
+#undef InterlockedExchangeAdd8
+
+#else
+
+#error Unsupported platform!
+
+#endif
+
+template <typename T>
+T FromObject(Handle<Object> number);
+
+template <>
+inline uint8_t FromObject<uint8_t>(Handle<Object> number) {
+  return NumberToUint32(*number);
+}
+
+template <>
+inline int8_t FromObject<int8_t>(Handle<Object> number) {
+  return NumberToInt32(*number);
+}
+
+template <>
+inline uint16_t FromObject<uint16_t>(Handle<Object> number) {
+  return NumberToUint32(*number);
+}
+
+template <>
+inline int16_t FromObject<int16_t>(Handle<Object> number) {
+  return NumberToInt32(*number);
+}
+
+template <>
+inline uint32_t FromObject<uint32_t>(Handle<Object> number) {
+  return NumberToUint32(*number);
+}
+
+template <>
+inline int32_t FromObject<int32_t>(Handle<Object> number) {
+  return NumberToInt32(*number);
+}
+
+inline Object* ToObject(Isolate* isolate, int8_t t) { return Smi::FromInt(t); }
+
+inline Object* ToObject(Isolate* isolate, uint8_t t) { return Smi::FromInt(t); }
+
+inline Object* ToObject(Isolate* isolate, int16_t t) { return Smi::FromInt(t); }
+
+inline Object* ToObject(Isolate* isolate, uint16_t t) {
+  return Smi::FromInt(t);
+}
+
+inline Object* ToObject(Isolate* isolate, int32_t t) {
+  return *isolate->factory()->NewNumber(t);
+}
+
+inline Object* ToObject(Isolate* isolate, uint32_t t) {
+  return *isolate->factory()->NewNumber(t);
+}
+
+template <typename T>
+inline Object* DoCompareExchange(Isolate* isolate, void* buffer, size_t index,
+                                 Handle<Object> oldobj, Handle<Object> newobj) {
+  T oldval = FromObject<T>(oldobj);
+  T newval = FromObject<T>(newobj);
+  T result =
+      CompareExchangeSeqCst(static_cast<T*>(buffer) + index, oldval, newval);
+  return ToObject(isolate, result);
+}
+
+template <typename T>
+inline Object* DoAdd(Isolate* isolate, void* buffer, size_t index,
+                     Handle<Object> obj) {
+  T value = FromObject<T>(obj);
+  T result = AddSeqCst(static_cast<T*>(buffer) + index, value);
+  return ToObject(isolate, result);
+}
+
+template <typename T>
+inline Object* DoSub(Isolate* isolate, void* buffer, size_t index,
+                     Handle<Object> obj) {
+  T value = FromObject<T>(obj);
+  T result = SubSeqCst(static_cast<T*>(buffer) + index, value);
+  return ToObject(isolate, result);
+}
+
+template <typename T>
+inline Object* DoAnd(Isolate* isolate, void* buffer, size_t index,
+                     Handle<Object> obj) {
+  T value = FromObject<T>(obj);
+  T result = AndSeqCst(static_cast<T*>(buffer) + index, value);
+  return ToObject(isolate, result);
+}
+
+template <typename T>
+inline Object* DoOr(Isolate* isolate, void* buffer, size_t index,
+                    Handle<Object> obj) {
+  T value = FromObject<T>(obj);
+  T result = OrSeqCst(static_cast<T*>(buffer) + index, value);
+  return ToObject(isolate, result);
+}
+
+template <typename T>
+inline Object* DoXor(Isolate* isolate, void* buffer, size_t index,
+                     Handle<Object> obj) {
+  T value = FromObject<T>(obj);
+  T result = XorSeqCst(static_cast<T*>(buffer) + index, value);
+  return ToObject(isolate, result);
+}
+
+}  // anonymous namespace
+
+// Duplicated from objects.h
+// V has parameters (Type, type, TYPE, C type, element_size)
+#define INTEGER_TYPED_ARRAYS(V)          \
+  V(Uint8, uint8, UINT8, uint8_t, 1)     \
+  V(Int8, int8, INT8, int8_t, 1)         \
+  V(Uint16, uint16, UINT16, uint16_t, 2) \
+  V(Int16, int16, INT16, int16_t, 2)     \
+  V(Uint32, uint32, UINT32, uint32_t, 4) \
+  V(Int32, int32, INT32, int32_t, 4)
+
+// ES #sec-atomics.wait
+// Atomics.compareExchange( typedArray, index, expectedValue, replacementValue )
+BUILTIN(AtomicsCompareExchange) {
+  HandleScope scope(isolate);
+  Handle<Object> array = args.atOrUndefined(isolate, 1);
+  Handle<Object> index = args.atOrUndefined(isolate, 2);
+  Handle<Object> expected_value = args.atOrUndefined(isolate, 3);
+  Handle<Object> replacement_value = args.atOrUndefined(isolate, 4);
+
+  Handle<JSTypedArray> sta;
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
+      isolate, sta, ValidateSharedIntegerTypedArray(isolate, array));
+
+  Maybe<size_t> maybe_index = ValidateAtomicAccess(isolate, sta, index);
+  if (maybe_index.IsNothing()) return isolate->heap()->exception();
+  size_t i = maybe_index.FromJust();
+
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
+      isolate, expected_value, Object::ToInteger(isolate, expected_value));
+
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
+      isolate, replacement_value,
+      Object::ToInteger(isolate, replacement_value));
+
+  uint8_t* source = static_cast<uint8_t*>(sta->GetBuffer()->backing_store()) +
+                    NumberToSize(sta->byte_offset());
+
+  switch (sta->type()) {
+#define TYPED_ARRAY_CASE(Type, typeName, TYPE, ctype, size)             \
+  case kExternal##Type##Array:                                          \
+    return DoCompareExchange<ctype>(isolate, source, i, expected_value, \
+                                    replacement_value);
+
+    INTEGER_TYPED_ARRAYS(TYPED_ARRAY_CASE)
+#undef TYPED_ARRAY_CASE
+
+    default:
+      break;
+  }
+
+  UNREACHABLE();
+  return isolate->heap()->undefined_value();
+}
+
+// ES #sec-atomics.add
+// Atomics.add( typedArray, index, value )
+BUILTIN(AtomicsAdd) {
+  HandleScope scope(isolate);
+  Handle<Object> array = args.atOrUndefined(isolate, 1);
+  Handle<Object> index = args.atOrUndefined(isolate, 2);
+  Handle<Object> value = args.atOrUndefined(isolate, 3);
+
+  Handle<JSTypedArray> sta;
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
+      isolate, sta, ValidateSharedIntegerTypedArray(isolate, array));
+
+  Maybe<size_t> maybe_index = ValidateAtomicAccess(isolate, sta, index);
+  if (maybe_index.IsNothing()) return isolate->heap()->exception();
+  size_t i = maybe_index.FromJust();
+
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, value,
+                                     Object::ToInteger(isolate, value));
+
+  uint8_t* source = static_cast<uint8_t*>(sta->GetBuffer()->backing_store()) +
+                    NumberToSize(sta->byte_offset());
+
+  switch (sta->type()) {
+#define TYPED_ARRAY_CASE(Type, typeName, TYPE, ctype, size) \
+  case kExternal##Type##Array:                              \
+    return DoAdd<ctype>(isolate, source, i, value);
+
+    INTEGER_TYPED_ARRAYS(TYPED_ARRAY_CASE)
+#undef TYPED_ARRAY_CASE
+
+    default:
+      break;
+  }
+
+  UNREACHABLE();
+  return isolate->heap()->undefined_value();
+}
+
+// ES #sec-atomics.sub
+// Atomics.sub( typedArray, index, value )
+BUILTIN(AtomicsSub) {
+  HandleScope scope(isolate);
+  Handle<Object> array = args.atOrUndefined(isolate, 1);
+  Handle<Object> index = args.atOrUndefined(isolate, 2);
+  Handle<Object> value = args.atOrUndefined(isolate, 3);
+
+  Handle<JSTypedArray> sta;
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
+      isolate, sta, ValidateSharedIntegerTypedArray(isolate, array));
+
+  Maybe<size_t> maybe_index = ValidateAtomicAccess(isolate, sta, index);
+  if (maybe_index.IsNothing()) return isolate->heap()->exception();
+  size_t i = maybe_index.FromJust();
+
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, value,
+                                     Object::ToInteger(isolate, value));
+
+  uint8_t* source = static_cast<uint8_t*>(sta->GetBuffer()->backing_store()) +
+                    NumberToSize(sta->byte_offset());
+
+  switch (sta->type()) {
+#define TYPED_ARRAY_CASE(Type, typeName, TYPE, ctype, size) \
+  case kExternal##Type##Array:                              \
+    return DoSub<ctype>(isolate, source, i, value);
+
+    INTEGER_TYPED_ARRAYS(TYPED_ARRAY_CASE)
+#undef TYPED_ARRAY_CASE
+
+    default:
+      break;
+  }
+
+  UNREACHABLE();
+  return isolate->heap()->undefined_value();
+}
+
+// ES #sec-atomics.and
+// Atomics.and( typedArray, index, value )
+BUILTIN(AtomicsAnd) {
+  HandleScope scope(isolate);
+  Handle<Object> array = args.atOrUndefined(isolate, 1);
+  Handle<Object> index = args.atOrUndefined(isolate, 2);
+  Handle<Object> value = args.atOrUndefined(isolate, 3);
+
+  Handle<JSTypedArray> sta;
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
+      isolate, sta, ValidateSharedIntegerTypedArray(isolate, array));
+
+  Maybe<size_t> maybe_index = ValidateAtomicAccess(isolate, sta, index);
+  if (maybe_index.IsNothing()) return isolate->heap()->exception();
+  size_t i = maybe_index.FromJust();
+
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, value,
+                                     Object::ToInteger(isolate, value));
+
+  uint8_t* source = static_cast<uint8_t*>(sta->GetBuffer()->backing_store()) +
+                    NumberToSize(sta->byte_offset());
+
+  switch (sta->type()) {
+#define TYPED_ARRAY_CASE(Type, typeName, TYPE, ctype, size) \
+  case kExternal##Type##Array:                              \
+    return DoAnd<ctype>(isolate, source, i, value);
+
+    INTEGER_TYPED_ARRAYS(TYPED_ARRAY_CASE)
+#undef TYPED_ARRAY_CASE
+
+    default:
+      break;
+  }
+
+  UNREACHABLE();
+  return isolate->heap()->undefined_value();
+}
+
+// ES #sec-atomics.or
+// Atomics.or( typedArray, index, value )
+BUILTIN(AtomicsOr) {
+  HandleScope scope(isolate);
+  Handle<Object> array = args.atOrUndefined(isolate, 1);
+  Handle<Object> index = args.atOrUndefined(isolate, 2);
+  Handle<Object> value = args.atOrUndefined(isolate, 3);
+
+  Handle<JSTypedArray> sta;
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
+      isolate, sta, ValidateSharedIntegerTypedArray(isolate, array));
+
+  Maybe<size_t> maybe_index = ValidateAtomicAccess(isolate, sta, index);
+  if (maybe_index.IsNothing()) return isolate->heap()->exception();
+  size_t i = maybe_index.FromJust();
+
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, value,
+                                     Object::ToInteger(isolate, value));
+
+  uint8_t* source = static_cast<uint8_t*>(sta->GetBuffer()->backing_store()) +
+                    NumberToSize(sta->byte_offset());
+
+  switch (sta->type()) {
+#define TYPED_ARRAY_CASE(Type, typeName, TYPE, ctype, size) \
+  case kExternal##Type##Array:                              \
+    return DoOr<ctype>(isolate, source, i, value);
+
+    INTEGER_TYPED_ARRAYS(TYPED_ARRAY_CASE)
+#undef TYPED_ARRAY_CASE
+
+    default:
+      break;
+  }
+
+  UNREACHABLE();
+  return isolate->heap()->undefined_value();
+}
+
+// ES #sec-atomics.xor
+// Atomics.xor( typedArray, index, value )
+BUILTIN(AtomicsXor) {
+  HandleScope scope(isolate);
+  Handle<Object> array = args.atOrUndefined(isolate, 1);
+  Handle<Object> index = args.atOrUndefined(isolate, 2);
+  Handle<Object> value = args.atOrUndefined(isolate, 3);
+
+  Handle<JSTypedArray> sta;
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
+      isolate, sta, ValidateSharedIntegerTypedArray(isolate, array));
+
+  Maybe<size_t> maybe_index = ValidateAtomicAccess(isolate, sta, index);
+  if (maybe_index.IsNothing()) return isolate->heap()->exception();
+  size_t i = maybe_index.FromJust();
+
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, value,
+                                     Object::ToInteger(isolate, value));
+
+  uint8_t* source = static_cast<uint8_t*>(sta->GetBuffer()->backing_store()) +
+                    NumberToSize(sta->byte_offset());
+
+  switch (sta->type()) {
+#define TYPED_ARRAY_CASE(Type, typeName, TYPE, ctype, size) \
+  case kExternal##Type##Array:                              \
+    return DoXor<ctype>(isolate, source, i, value);
+
+    INTEGER_TYPED_ARRAYS(TYPED_ARRAY_CASE)
+#undef TYPED_ARRAY_CASE
+
+    default:
+      break;
+  }
+
+  UNREACHABLE();
+  return isolate->heap()->undefined_value();
+}
+
 }  // namespace internal
 }  // namespace v8