Revert of Remove SIMD.js from V8.

src/full-codegen/x87/full-codegen-x87.cc

Index: src/full-codegen/x87/full-codegen-x87.cc
diff --git a/src/full-codegen/x87/full-codegen-x87.cc b/src/full-codegen/x87/full-codegen-x87.cc
index f4a8a9eb1c97704a7464cabd245f7d41a27ef78d..b04623a3bdebe2e42ba9b1b704bc10ca8b7b712b 100644
--- a/src/full-codegen/x87/full-codegen-x87.cc
+++ b/src/full-codegen/x87/full-codegen-x87.cc
@@ -2532,6 +2532,16 @@
     __ test_b(FieldOperand(edx, Map::kBitFieldOffset),
               Immediate((1 << Map::kIsCallable) | (1 << Map::kIsUndetectable)));
     Split(zero, if_true, if_false, fall_through);
+// clang-format off
+#define SIMD128_TYPE(TYPE, Type, type, lane_count, lane_type)   \
+  } else if (String::Equals(check, factory->type##_string())) { \
+    __ JumpIfSmi(eax, if_false);                                \
+    __ cmp(FieldOperand(eax, HeapObject::kMapOffset),           \
+           isolate()->factory()->type##_map());                 \
+    Split(equal, if_true, if_false, fall_through);
+  SIMD128_TYPES(SIMD128_TYPE)
+#undef SIMD128_TYPE
+    // clang-format on
   } else {
     if (if_false != fall_through) __ jmp(if_false);
   }