Expose SameValue equality comparison algorithm

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 2ed417fa3c409aaeb00bcf04c36dd8d21ece488c..169307fb8e077c8cb4513f6f9fdaa489ac2dc26d 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -1005,8 +1005,11 @@ bool Object::SameValue(Object* other) {
   if (IsNumber() && other->IsNumber()) {
     double this_value = Number();
     double other_value = other->Number();
-    return (this_value == other_value) ||
-        (std::isnan(this_value) && std::isnan(other_value));
+    bool equal = this_value == other_value;
+    // SameValue(NaN, NaN) is true.
+    if (!equal) return std::isnan(this_value) && std::isnan(other_value);
+    // SameValue(0.0, -0.0) is false.
+    return (this_value != 0) || ((1 / this_value) == (1 / other_value));

[yusukesuzuki, 2013/09/24 12:58:26]

According to the comment of Object::SameValue in objects.h, this method
represents ECMA262 SameValue and Harmony egal operator.
So `SameValue(0.0, -0.0)` should return false.

   }
   if (IsString() && other->IsString()) {
     return String::cast(this)->Equals(String::cast(other));