X87: Skip the mapcheck on the global object since the global proxy and cell are already checked

port 6af7ca6b (r26886)

original commit message:

  Skip the mapcheck on the global object since the global proxy and cell are already
  checked (or the global object map for contextual global loads).

BUG=

Review URL: https://codereview.chromium.org/965693002

Cr-Commit-Position: refs/heads/master@{#26908}

src/ic/x87/handler-compiler-x87.cc

@@ -476,16 +476,15 @@ Register PropertyHandlerCompiler::CheckPrototypes(
     } else {
       Register map_reg = scratch1;
       __ mov(map_reg, FieldOperand(reg, HeapObject::kMapOffset));
-      if (depth != 1 || check == CHECK_ALL_MAPS) {
+      if (current_map->IsJSGlobalObjectMap()) {
+        GenerateCheckPropertyCell(masm(), Handle<JSGlobalObject>::cast(current),
+                                  name, scratch2, miss);
+      } else if (depth != 1 || check == CHECK_ALL_MAPS) {
         Handle<WeakCell> cell = Map::WeakCellForMap(current_map);
         __ CmpWeakValue(map_reg, cell, scratch2);
         __ j(not_equal, miss);
       }
 
-      if (current_map->IsJSGlobalObjectMap()) {
-        GenerateCheckPropertyCell(masm(), Handle<JSGlobalObject>::cast(current),
-                                  name, scratch2, miss);
-      }
       reg = holder_reg;  // From now on the object will be in holder_reg.
       __ mov(reg, FieldOperand(map_reg, Map::kPrototypeOffset));
     }
@@ -495,6 +494,8 @@ Register PropertyHandlerCompiler::CheckPrototypes(
     current_map = handle(current->map());
   }
 
+  DCHECK(!current_map->IsJSGlobalProxyMap());
+
   // Log the check depth.
   LOG(isolate(), IntEvent("check-maps-depth", depth + 1));