Revert of Remove SIMD.js from V8.

src/code-stub-assembler.h

Index: src/code-stub-assembler.h
diff --git a/src/code-stub-assembler.h b/src/code-stub-assembler.h
index ca5174b167dfc9eee0dd357aceea6d32b9e189dc..98b7881d4f16aefb0390edc896c57b7c290d2308 100644
--- a/src/code-stub-assembler.h
+++ b/src/code-stub-assembler.h
@@ -305,6 +305,14 @@
   // Branches to {if_true} if ToBoolean applied to {value} yields true,
   // otherwise goes to {if_false}.
   void BranchIfToBooleanIsTrue(Node* value, Label* if_true, Label* if_false);
+
+  void BranchIfSimd128Equal(Node* lhs, Node* lhs_map, Node* rhs, Node* rhs_map,
+                            Label* if_equal, Label* if_notequal);
+  void BranchIfSimd128Equal(Node* lhs, Node* rhs, Label* if_equal,
+                            Label* if_notequal) {
+    BranchIfSimd128Equal(lhs, LoadMap(lhs), rhs, LoadMap(rhs), if_equal,
+                         if_notequal);
+  }
 
   void BranchIfJSReceiver(Node* object, Label* if_true, Label* if_false);
   void BranchIfJSObject(Node* object, Label* if_true, Label* if_false);