Reland of [turbofan] Restore basic write barrier elimination.

src/compiler/simplified-operator.cc

Index: src/compiler/simplified-operator.cc
diff --git a/src/compiler/simplified-operator.cc b/src/compiler/simplified-operator.cc
index f383ace587470e46ea00dd5055bfdc1c55e0e196..707bf098bc4c32aef532c914c89c36ea4bf48bfc 100644
--- a/src/compiler/simplified-operator.cc
+++ b/src/compiler/simplified-operator.cc
@@ -12,6 +12,10 @@
 namespace v8 {
 namespace internal {
 namespace compiler {
+
+size_t hash_value(BaseTaggedness base_taggedness) {
+  return static_cast<uint8_t>(base_taggedness);
+}
 
 std::ostream& operator<<(std::ostream& os, BaseTaggedness base_taggedness) {
   switch (base_taggedness) {
@@ -84,6 +88,9 @@
 
 
 bool operator==(FieldAccess const& lhs, FieldAccess const& rhs) {
+  // On purpose we don't include the write barrier kind here, as this method is
+  // really only relevant for eliminating loads and they don't care about the
+  // write barrier mode.
   return lhs.base_is_tagged == rhs.base_is_tagged && lhs.offset == rhs.offset &&
          lhs.machine_type == rhs.machine_type;
 }
@@ -95,6 +102,9 @@
 
 
 size_t hash_value(FieldAccess const& access) {
+  // On purpose we don't include the write barrier kind here, as this method is
+  // really only relevant for eliminating loads and they don't care about the
+  // write barrier mode.
   return base::hash_combine(access.base_is_tagged, access.offset,
                             access.machine_type);
 }
@@ -110,12 +120,15 @@
   }
 #endif
   access.type->PrintTo(os);
-  os << ", " << access.machine_type << "]";
+  os << ", " << access.machine_type << ", " << access.write_barrier_kind << "]";
   return os;
 }
 
 
 bool operator==(ElementAccess const& lhs, ElementAccess const& rhs) {
+  // On purpose we don't include the write barrier kind here, as this method is
+  // really only relevant for eliminating loads and they don't care about the
+  // write barrier mode.
   return lhs.base_is_tagged == rhs.base_is_tagged &&
          lhs.header_size == rhs.header_size &&
          lhs.machine_type == rhs.machine_type;
@@ -128,6 +141,9 @@
 
 
 size_t hash_value(ElementAccess const& access) {
+  // On purpose we don't include the write barrier kind here, as this method is
+  // really only relevant for eliminating loads and they don't care about the
+  // write barrier mode.
   return base::hash_combine(access.base_is_tagged, access.header_size,
                             access.machine_type);
 }
@@ -136,7 +152,7 @@
 std::ostream& operator<<(std::ostream& os, ElementAccess const& access) {
   os << access.base_is_tagged << ", " << access.header_size << ", ";
   access.type->PrintTo(os);
-  os << ", " << access.machine_type;
+  os << ", " << access.machine_type << ", " << access.write_barrier_kind;
   return os;
 }