Fix 'typeof null' canonicalization in crankshaft

src/crankshaft/hydrogen-instructions.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/hydrogen-instructions.h"
 
 #include "src/base/bits.h"
 #include "src/base/safe_math.h"
 #include "src/crankshaft/hydrogen-infer-representation.h"
 #include "src/double.h"
@@ skipping 1185 matching lines @@
   os << NameOf(value()) << " == " << type_literal()->ToCString().get();
   return HControlInstruction::PrintDataTo(os);
 }
 
 
 namespace {
 
 String* TypeOfString(HConstant* constant, Isolate* isolate) {
   Heap* heap = isolate->heap();
   if (constant->HasNumberValue()) return heap->number_string();
+  if (constant->GetInstanceType() == ODDBALL_TYPE &&
+      constant->GetUnique().IsKnownGlobal(heap->null_value())) {
+    return heap->object_string();
+  }
   if (constant->IsUndetectable()) return heap->undefined_string();
   if (constant->HasStringValue()) return heap->string_string();
   switch (constant->GetInstanceType()) {
     case ODDBALL_TYPE: {
       Unique<Object> unique = constant->GetUnique();
       if (unique.IsKnownGlobal(heap->true_value()) ||
           unique.IsKnownGlobal(heap->false_value())) {
         return heap->boolean_string();
       }
       if (unique.IsKnownGlobal(heap->null_value())) {

[Jakob Kummerow, 2016/04/21 09:30:56]

This is dead code now, replace with DCHECK and comment that it's handled above?

         return heap->object_string();
       }
       DCHECK(unique.IsKnownGlobal(heap->undefined_value()));
       return heap->undefined_string();
     }
     case SYMBOL_TYPE:
       return heap->symbol_string();
     case SIMD128_VALUE_TYPE: {
       Unique<Map> map = constant->ObjectMap();
 #define SIMD128_TYPE(TYPE, Type, type, lane_count, lane_type) \
@@ skipping 2903 matching lines @@
     case HObjectAccess::kExternalMemory:
       os << "[external-memory]";
       break;
   }
 
   return os << "@" << access.offset();
 }
 
 }  // namespace internal
 }  // namespace v8