Mark null and undefined as undetectable, and use it to handle abstract equality comparison in the g…

src/x64/code-stubs-x64.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/bootstrapper.h"
 #include "src/code-stubs.h"
 #include "src/codegen.h"
 #include "src/ic/handler-compiler.h"
@@ skipping 1677 matching lines @@
 
 #ifdef DEBUG
   __ Abort(kUnexpectedFallThroughFromStringComparison);
 #endif
 
   __ bind(&check_unequal_objects);
   if (cc == equal && !strict()) {
     // Not strict equality.  Objects are unequal if
     // they are both JSObjects and not undetectable,
     // and their pointers are different.
-    Label return_unequal;
+    Label return_unequal, undetectable;
     // At most one is a smi, so we can test for smi by adding the two.
     // A smi plus a heap object has the low bit set, a heap object plus
     // a heap object has the low bit clear.
     STATIC_ASSERT(kSmiTag == 0);
     STATIC_ASSERT(kSmiTagMask == 1);
     __ leap(rcx, Operand(rax, rdx, times_1, 0));
     __ testb(rcx, Immediate(kSmiTagMask));
     __ j(not_zero, &runtime_call, Label::kNear);
-    __ CmpObjectType(rax, FIRST_JS_RECEIVER_TYPE, rbx);
-    __ j(below, &runtime_call, Label::kNear);
-    __ CmpObjectType(rdx, FIRST_JS_RECEIVER_TYPE, rcx);
-    __ j(below, &runtime_call, Label::kNear);
+
+    __ movp(rbx, FieldOperand(rax, HeapObject::kMapOffset));
+    __ movp(rcx, FieldOperand(rdx, HeapObject::kMapOffset));
     __ testb(FieldOperand(rbx, Map::kBitFieldOffset),
              Immediate(1 << Map::kIsUndetectable));
-    __ j(zero, &return_unequal, Label::kNear);
+    __ j(not_zero, &undetectable);
     __ testb(FieldOperand(rcx, Map::kBitFieldOffset),
              Immediate(1 << Map::kIsUndetectable));
-    __ j(zero, &return_unequal, Label::kNear);
-    // The objects are both undetectable, so they both compare as the value
-    // undefined, and are equal.
+    __ j(not_zero, &return_unequal);
+
+    __ CmpInstanceType(rbx, FIRST_JS_RECEIVER_TYPE);
+    __ j(below, &runtime_call, Label::kNear);
+    __ CmpInstanceType(rcx, FIRST_JS_RECEIVER_TYPE);
+    __ j(below, &runtime_call, Label::kNear);
+
+    __ bind(&return_unequal);
+    // Return non-equal by returning the non-zero object pointer in rax.
+    __ ret(0);
+
+    __ bind(&undetectable);
+    __ testb(FieldOperand(rcx, Map::kBitFieldOffset),
+             Immediate(1 << Map::kIsUndetectable));
+    __ j(zero, &return_unequal);
     __ Set(rax, EQUAL);
-    __ bind(&return_unequal);
-    // Return non-equal by returning the non-zero object pointer in rax,
-    // or return equal if we fell through to here.
     __ ret(0);
   }
   __ bind(&runtime_call);
 
   // Push arguments below the return address to prepare jump to builtin.
   __ PopReturnAddressTo(rcx);
   __ Push(rdx);
   __ Push(rax);
 
   // Figure out which native to call and setup the arguments.
@@ skipping 3844 matching lines @@
                            NULL);
 }
 
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64