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

src/crankshaft/mips64/lithium-codegen-mips64.cc

 // Copyright 2012 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.
 
 #include "src/crankshaft/mips64/lithium-codegen-mips64.h"
 
 #include "src/code-factory.h"
 #include "src/code-stubs.h"
 #include "src/crankshaft/hydrogen-osr.h"
 #include "src/crankshaft/mips64/lithium-gap-resolver-mips64.h"
@@ skipping 5439 matching lines @@
 
   } else if (String::Equals(type_name, factory->boolean_string())) {
     __ LoadRoot(at, Heap::kTrueValueRootIndex);
     __ Branch(USE_DELAY_SLOT, true_label, eq, at, Operand(input));
     __ LoadRoot(at, Heap::kFalseValueRootIndex);
     *cmp1 = at;
     *cmp2 = Operand(input);
     final_branch_condition = eq;
 
   } else if (String::Equals(type_name, factory->undefined_string())) {
-    __ LoadRoot(at, Heap::kUndefinedValueRootIndex);
-    __ Branch(USE_DELAY_SLOT, true_label, eq, at, Operand(input));
+    __ LoadRoot(at, Heap::kNullValueRootIndex);
+    __ Branch(USE_DELAY_SLOT, false_label, eq, at, Operand(input));
     // The first instruction of JumpIfSmi is an And - it is safe in the delay
     // slot.
     __ JumpIfSmi(input, false_label);
     // Check for undetectable objects => true.
     __ ld(input, FieldMemOperand(input, HeapObject::kMapOffset));
     __ lbu(at, FieldMemOperand(input, Map::kBitFieldOffset));
     __ And(at, at, 1 << Map::kIsUndetectable);
     *cmp1 = at;
     *cmp2 = Operand(zero_reg);
     final_branch_condition = ne;
@@ skipping 304 matching lines @@
   __ Push(at, ToRegister(instr->function()));
   CallRuntime(Runtime::kPushBlockContext, instr);
   RecordSafepoint(Safepoint::kNoLazyDeopt);
 }
 
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8