BuildNumberToString: Check for undefined keys in the cache

src/hydrogen.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.
 
 #include "hydrogen.h"
 
 #include <algorithm>
 
 #include "v8.h"
 #include "allocation-site-scopes.h"
@@ skipping 1659 matching lines @@
             HObjectAccess::ForHeapNumberValueHighestBits());
         HValue* hash = AddUncasted<HBitwise>(Token::BIT_XOR, low, high);
         hash = AddUncasted<HBitwise>(Token::BIT_AND, hash, mask);
 
         // Load the key.
         HValue* key_index = AddUncasted<HShl>(hash, graph()->GetConstant1());
         HValue* key = Add<HLoadKeyed>(number_string_cache, key_index,
                                       static_cast<HValue*>(NULL),
                                       FAST_ELEMENTS, ALLOW_RETURN_HOLE);
 
-        // Check if key is a heap number (the number string cache contains only
-        // SMIs and heap number, so it is sufficient to do a SMI check here).

[Jakob Kummerow, 2014/05/30 16:56:52]

This comment is a lie! Unused entries in the cache are |undefined|.

+        // Check if the key is a heap number and compare it with the object.
         IfBuilder if_keyisnotsmi(this);
         HValue* keyisnotsmi = if_keyisnotsmi.IfNot<HIsSmiAndBranch>(key);
         if_keyisnotsmi.Then();
         {
-          // Check if values of key and object match.

[Jakob Kummerow, 2014/05/30 16:56:52]

This entire block is actually unchanged, just indented one level deeper.

-          IfBuilder if_keyeqobject(this);
-          if_keyeqobject.If<HCompareNumericAndBranch>(
-              Add<HLoadNamedField>(key, keyisnotsmi,
-                                   HObjectAccess::ForHeapNumberValue()),
-              Add<HLoadNamedField>(object, objectisnumber,
-                                   HObjectAccess::ForHeapNumberValue()),
-              Token::EQ);
-          if_keyeqobject.Then();
+          IfBuilder if_keyisheapnumber(this);
+          if_keyisheapnumber.If<HCompareMap>(
+              key, isolate()->factory()->heap_number_map());
+          if_keyisheapnumber.Then();
           {
-            // Make the key_index available.
-            Push(key_index);
+            // Check if values of key and object match.
+            IfBuilder if_keyeqobject(this);
+            if_keyeqobject.If<HCompareNumericAndBranch>(
+                Add<HLoadNamedField>(key, keyisnotsmi,
+                                     HObjectAccess::ForHeapNumberValue()),
+                Add<HLoadNamedField>(object, objectisnumber,
+                                     HObjectAccess::ForHeapNumberValue()),
+                Token::EQ);
+            if_keyeqobject.Then();
+            {
+              // Make the key_index available.
+              Push(key_index);
+            }
+            if_keyeqobject.JoinContinuation(&found);
           }
-          if_keyeqobject.JoinContinuation(&found);
+          if_keyisheapnumber.JoinContinuation(&found);
         }
         if_keyisnotsmi.JoinContinuation(&found);
       }
       if_objectisnumber.Else();
       {
         if (type->Is(Type::Number())) {
           if_objectisnumber.Deopt("Expected heap number");
         }
       }
       if_objectisnumber.JoinContinuation(&found);
@@ skipping 10078 matching lines @@
   if (ShouldProduceTraceOutput()) {
     isolate()->GetHTracer()->TraceHydrogen(name(), graph_);
   }
 
 #ifdef DEBUG
   graph_->Verify(false);  // No full verify.
 #endif
 }
 
 } }  // namespace v8::internal