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

src/full-codegen/mips/full-codegen-mips.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.
 
 #if V8_TARGET_ARCH_MIPS
 
 // Note on Mips implementation:
 //
 // The result_register() for mips is the 'v0' register, which is defined
 // by the ABI to contain function return values. However, the first
@@ skipping 509 matching lines @@
   __ li(result_register(), Operand(lit));
   __ push(result_register());
 }
 
 
 void FullCodeGenerator::TestContext::Plug(Handle<Object> lit) const {
   codegen()->PrepareForBailoutBeforeSplit(condition(),
                                           true,
                                           true_label_,
                                           false_label_);
-  DCHECK(!lit->IsUndetectableObject());  // There are no undetectable literals.
+  DCHECK(lit->IsNull() || lit->IsUndefined() || !lit->IsUndetectableObject());
   if (lit->IsUndefined() || lit->IsNull() || lit->IsFalse()) {
     if (false_label_ != fall_through_) __ Branch(false_label_);
   } else if (lit->IsTrue() || lit->IsJSObject()) {
     if (true_label_ != fall_through_) __ Branch(true_label_);
   } else if (lit->IsString()) {
     if (String::cast(*lit)->length() == 0) {
       if (false_label_ != fall_through_) __ Branch(false_label_);
     } else {
       if (true_label_ != fall_through_) __ Branch(true_label_);
     }
@@ skipping 3750 matching lines @@
   } else if (String::Equals(check, factory->symbol_string())) {
     __ JumpIfSmi(v0, if_false);
     __ GetObjectType(v0, v0, a1);
     Split(eq, a1, Operand(SYMBOL_TYPE), if_true, if_false, fall_through);
   } else if (String::Equals(check, factory->boolean_string())) {
     __ LoadRoot(at, Heap::kTrueValueRootIndex);
     __ Branch(if_true, eq, v0, Operand(at));
     __ LoadRoot(at, Heap::kFalseValueRootIndex);
     Split(eq, v0, Operand(at), if_true, if_false, fall_through);
   } else if (String::Equals(check, factory->undefined_string())) {
-    __ LoadRoot(at, Heap::kUndefinedValueRootIndex);
-    __ Branch(if_true, eq, v0, Operand(at));
+    __ LoadRoot(at, Heap::kNullValueRootIndex);
+    __ Branch(if_false, eq, v0, Operand(at));
     __ JumpIfSmi(v0, if_false);
     // Check for undetectable objects => true.
     __ lw(v0, FieldMemOperand(v0, HeapObject::kMapOffset));
     __ lbu(a1, FieldMemOperand(v0, Map::kBitFieldOffset));
     __ And(a1, a1, Operand(1 << Map::kIsUndetectable));
     Split(ne, a1, Operand(zero_reg), if_true, if_false, fall_through);
   } else if (String::Equals(check, factory->function_string())) {
     __ JumpIfSmi(v0, if_false);
     __ lw(v0, FieldMemOperand(v0, HeapObject::kMapOffset));
     __ lbu(a1, FieldMemOperand(v0, Map::kBitFieldOffset));
@@ skipping 325 matching lines @@
          reinterpret_cast<uint32_t>(
              isolate->builtins()->OsrAfterStackCheck()->entry()));
   return OSR_AFTER_STACK_CHECK;
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_MIPS