V8: Add utility functions to check SameValue and SameValueZero.

src/utils.h

Index: src/utils.h
diff --git a/src/utils.h b/src/utils.h
index 582c5769936947698217cf5fd5ef219ab7e919eb..1cbcdf4aafb6677eac00ad5911f95bc149aaa129 100644
--- a/src/utils.h
+++ b/src/utils.h
@@ -201,6 +201,24 @@ inline double Floor(double x) {
 }
 
 
+template <typename T>
+bool SameValue(T x, T y) {

[adamk, 2015/07/14 18:26:58]

Can you add a comment linking to:

http://www.ecma-international.org/ecma-262/6.0/#sec-samevalue

[bbudge, 2015/07/14 20:26:24]

Done.

+  // SameValue(NaN, NaN) is true.
+  if (x != y) return std::isnan(x) && std::isnan(y);
+  // SameValue(0, -0) is false.
+  if (std::signbit(x) != std::signbit(y)) return false;
+  return true;
+}
+
+
+template <typename T>
+bool SameValueZero(T x, T y) {

[adamk, 2015/07/14 18:26:58]

And here linking to:

http://www.ecma-international.org/ecma-262/6.0/#sec-samevaluezero

[bbudge, 2015/07/14 20:26:24]

Done.

+  if (x != y) return std::isnan(x) && std::isnan(y);
+  // SameValueZero doesn't distinguish between 0 and -0.
+  return true;
+}
+
+
 // TODO(svenpanne) Clean up the whole power-of-2 mess.
 inline int32_t WhichPowerOf2Abs(int32_t x) {
   return (x == kMinInt) ? 31 : WhichPowerOf2(Abs(x));