Reintroduce fast path in full-codegen for VisitArrayLiteral.

src/x64/full-codegen-x64.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1518 matching lines @@
         CompileTimeValue::IsCompileTimeValue(subexpr)) {
       continue;
     }
 
     if (!result_saved) {
       __ push(rax);
       result_saved = true;
     }
     VisitForAccumulatorValue(subexpr);
 
-    // Store the subexpression value in the array's elements.
-    __ movq(rbx, Operand(rsp, 0));  // Copy of array literal.
-    __ movq(rdi, FieldOperand(rbx, JSObject::kMapOffset));
-    __ Move(rcx, Smi::FromInt(i));
-    __ Move(rdx, Smi::FromInt(expr->literal_index()));
-    StoreArrayLiteralElementStub stub;
-    __ CallStub(&stub);
+    if (constant_elements_kind == FAST_ELEMENTS) {
+      // Fast-case array literal with ElementsKind of FAST_ELEMENTS, they cannot
+      // transition and don't need to call the runtime stub.
+      int offset = FixedArray::kHeaderSize + (i * kPointerSize);
+      __ movq(rbx, Operand(rsp, 0));  // Copy of array literal.
+      __ movq(rbx, FieldOperand(rbx, JSObject::kElementsOffset));
+      // Store the subexpression value in the array's elements.
+      __ movq(FieldOperand(rbx, offset), result_register());
+      // Update the write barrier for the array store.
+      __ RecordWriteField(rbx, offset, result_register(), rcx,
+                          kDontSaveFPRegs,
+                          EMIT_REMEMBERED_SET,
+                          INLINE_SMI_CHECK);
+    } else {
+      // Store the subexpression value in the array's elements.
+      __ movq(rbx, Operand(rsp, 0));  // Copy of array literal.
+      __ movq(rdi, FieldOperand(rbx, JSObject::kMapOffset));
+      __ Move(rcx, Smi::FromInt(i));
+      __ Move(rdx, Smi::FromInt(expr->literal_index()));
+      StoreArrayLiteralElementStub stub;
+      __ CallStub(&stub);
+    }
 
     PrepareForBailoutForId(expr->GetIdForElement(i), NO_REGISTERS);
   }
 
   if (result_saved) {
     context()->PlugTOS();
   } else {
     context()->Plug(rax);
   }
 }
@@ skipping 2757 matching lines @@
   *context_length = 0;
   return previous_;
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64