Reland of [turbofan] Restore basic write barrier elimination.

src/globals.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_GLOBALS_H_
 #define V8_GLOBALS_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 434 matching lines @@
 const int kSpaceTagSize = 3;
 const int kSpaceTagMask = (1 << kSpaceTagSize) - 1;
 
 enum AllocationAlignment {
   kWordAligned,
   kDoubleAligned,
   kDoubleUnaligned,
   kSimd128Unaligned
 };
 
+// Supported write barrier modes.
+enum WriteBarrierKind : uint8_t {
+  kNoWriteBarrier,
+  kMapWriteBarrier,
+  kPointerWriteBarrier,
+  kFullWriteBarrier
+};
+
+inline size_t hash_value(WriteBarrierKind kind) {
+  return static_cast<uint8_t>(kind);
+}
+
+inline std::ostream& operator<<(std::ostream& os, WriteBarrierKind kind) {
+  switch (kind) {
+    case kNoWriteBarrier:
+      return os << "NoWriteBarrier";
+    case kMapWriteBarrier:
+      return os << "MapWriteBarrier";
+    case kPointerWriteBarrier:
+      return os << "PointerWriteBarrier";
+    case kFullWriteBarrier:
+      return os << "FullWriteBarrier";
+  }
+  UNREACHABLE();
+  return os;
+}
+
 // A flag that indicates whether objects should be pretenured when
 // allocated (allocated directly into the old generation) or not
 // (allocated in the young generation if the object size and type
 // allows).
 enum PretenureFlag { NOT_TENURED, TENURED };
 
 inline std::ostream& operator<<(std::ostream& os, const PretenureFlag& flag) {
   switch (flag) {
     case NOT_TENURED:
       return os << "NotTenured";
@@ skipping 566 matching lines @@
   return static_cast<uint32_t>(bit_cast<uintptr_t>(address) >>
                                kPointerSizeLog2);
 }
 
 }  // namespace internal
 }  // namespace v8
 
 namespace i = v8::internal;
 
 #endif  // V8_GLOBALS_H_