S390: [cleanup] Drop FLAG_eliminate_prototype_chain_checks

port eac1b38d

Original Commit Message:
    This flag has been on by default for a while, along with
    FLAG_track_prototype_users which provides the prerequisite
    infrastructure. We are now sure that this is the direction
    we want to go in, so in order to simplify the code, this CL
    drops the respective flag-off code paths.

R=jkummerow@chromium.org, joransiu@ca.ibm.com, michael_dawson@ca.ibm.com, mbrandy@us.ibm.com
BUG=

Review-Url: https://codereview.chromium.org/2004173003
Cr-Commit-Position: refs/heads/master@{#36491}

src/ic/s390/handler-compiler-s390.cc

@@ -406,28 +406,25 @@ Register PropertyHandlerCompiler::CheckPrototypes(
   DCHECK(!scratch2.is(object_reg) && !scratch2.is(holder_reg) &&
          !scratch2.is(scratch1));
 
-  if (FLAG_eliminate_prototype_chain_checks) {
-    Handle<Cell> validity_cell =
-        Map::GetOrCreatePrototypeChainValidityCell(receiver_map, isolate());
-    if (!validity_cell.is_null()) {
-      DCHECK_EQ(Smi::FromInt(Map::kPrototypeChainValid),
-                validity_cell->value());
-      __ mov(scratch1, Operand(validity_cell));
-      __ LoadP(scratch1, FieldMemOperand(scratch1, Cell::kValueOffset));
-      __ CmpSmiLiteral(scratch1, Smi::FromInt(Map::kPrototypeChainValid), r0);
-      __ bne(miss);
-    }
+  Handle<Cell> validity_cell =
+      Map::GetOrCreatePrototypeChainValidityCell(receiver_map, isolate());
+  if (!validity_cell.is_null()) {
+    DCHECK_EQ(Smi::FromInt(Map::kPrototypeChainValid), validity_cell->value());
+    __ mov(scratch1, Operand(validity_cell));
+    __ LoadP(scratch1, FieldMemOperand(scratch1, Cell::kValueOffset));
+    __ CmpSmiLiteral(scratch1, Smi::FromInt(Map::kPrototypeChainValid), r0);
+    __ bne(miss);
+  }
 
-    // The prototype chain of primitives (and their JSValue wrappers) depends
-    // on the native context, which can't be guarded by validity cells.
-    // |object_reg| holds the native context specific prototype in this case;
-    // we need to check its map.
-    if (check == CHECK_ALL_MAPS) {
-      __ LoadP(scratch1, FieldMemOperand(object_reg, HeapObject::kMapOffset));
-      Handle<WeakCell> cell = Map::WeakCellForMap(receiver_map);
-      __ CmpWeakValue(scratch1, cell, scratch2);
-      __ b(ne, miss);
-    }
+  // The prototype chain of primitives (and their JSValue wrappers) depends
+  // on the native context, which can't be guarded by validity cells.
+  // |object_reg| holds the native context specific prototype in this case;
+  // we need to check its map.
+  if (check == CHECK_ALL_MAPS) {
+    __ LoadP(scratch1, FieldMemOperand(object_reg, HeapObject::kMapOffset));
+    Handle<WeakCell> cell = Map::WeakCellForMap(receiver_map);
+    __ CmpWeakValue(scratch1, cell, scratch2);
+    __ b(ne, miss);
   }
 
   // Keep track of the current object in register reg.
@@ -462,8 +459,10 @@ Register PropertyHandlerCompiler::CheckPrototypes(
            !current_map->is_access_check_needed());
 
     prototype = handle(JSObject::cast(current_map->prototype()));
-    if (current_map->is_dictionary_map() &&
-        !current_map->IsJSGlobalObjectMap()) {
+    if (current_map->IsJSGlobalObjectMap()) {
+      GenerateCheckPropertyCell(masm(), Handle<JSGlobalObject>::cast(current),
+                                name, scratch2, miss);
+    } else if (current_map->is_dictionary_map()) {
       DCHECK(!current_map->IsJSGlobalProxyMap());  // Proxy maps are fast.
       if (!name->IsUniqueName()) {
         DCHECK(name->IsString());
@@ -473,33 +472,12 @@ Register PropertyHandlerCompiler::CheckPrototypes(
              current->property_dictionary()->FindEntry(name) ==
                  NameDictionary::kNotFound);
 
-      if (FLAG_eliminate_prototype_chain_checks && depth > 1) {
+      if (depth > 1) {
         // TODO(jkummerow): Cache and re-use weak cell.
         __ LoadWeakValue(reg, isolate()->factory()->NewWeakCell(current), miss);
       }
       GenerateDictionaryNegativeLookup(masm(), miss, reg, name, scratch1,
                                        scratch2);
-      if (!FLAG_eliminate_prototype_chain_checks) {
-        __ LoadP(scratch1, FieldMemOperand(reg, HeapObject::kMapOffset));
-        __ LoadP(holder_reg, FieldMemOperand(scratch1, Map::kPrototypeOffset));
-      }
-    } else {
-      Register map_reg = scratch1;
-      if (!FLAG_eliminate_prototype_chain_checks) {
-        __ LoadP(map_reg, FieldMemOperand(reg, HeapObject::kMapOffset));
-      }
-      if (current_map->IsJSGlobalObjectMap()) {
-        GenerateCheckPropertyCell(masm(), Handle<JSGlobalObject>::cast(current),
-                                  name, scratch2, miss);
-      } else if (!FLAG_eliminate_prototype_chain_checks &&
-                 (depth != 1 || check == CHECK_ALL_MAPS)) {
-        Handle<WeakCell> cell = Map::WeakCellForMap(current_map);
-        __ CmpWeakValue(map_reg, cell, scratch2);
-        __ bne(miss);
-      }
-      if (!FLAG_eliminate_prototype_chain_checks) {
-        __ LoadP(holder_reg, FieldMemOperand(map_reg, Map::kPrototypeOffset));
-      }
     }
 
     reg = holder_reg;  // From now on the object will be in holder_reg.
@@ -513,17 +491,8 @@ Register PropertyHandlerCompiler::CheckPrototypes(
   // Log the check depth.
   LOG(isolate(), IntEvent("check-maps-depth", depth + 1));
 
-  if (!FLAG_eliminate_prototype_chain_checks &&
-      (depth != 0 || check == CHECK_ALL_MAPS)) {
-    // Check the holder map.
-    __ LoadP(scratch1, FieldMemOperand(reg, HeapObject::kMapOffset));
-    Handle<WeakCell> cell = Map::WeakCellForMap(current_map);
-    __ CmpWeakValue(scratch1, cell, scratch2);
-    __ bne(miss);
-  }
-
   bool return_holder = return_what == RETURN_HOLDER;
-  if (FLAG_eliminate_prototype_chain_checks && return_holder && depth != 0) {
+  if (return_holder && depth != 0) {
     __ LoadWeakValue(reg, isolate()->factory()->NewWeakCell(current), miss);
   }