V8: Add utility functions to check SameValue and SameValueZero.

src/utils.h

 // 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.
 
 #ifndef V8_UTILS_H_
 #define V8_UTILS_H_
 
 #include <limits.h>
 #include <stdlib.h>
 #include <string.h>
@@ skipping 183 matching lines @@
 
 // Floor(-0.0) == 0.0
 inline double Floor(double x) {
 #if V8_CC_MSVC
   if (x == 0) return x;  // Fix for issue 3477.
 #endif
   return std::floor(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));
 }
 
 
 // Obtains the unsigned type corresponding to T
 // available in C++11 as std::make_unsigned
 template<typename T>
 struct make_unsigned {
@@ skipping 1534 matching lines @@
   uint32_t* ptr = reinterpret_cast<uint32_t*>(p);
   *ptr = c.u[0];
   *(ptr + 1) = c.u[1];
 #endif  // V8_TARGET_ARCH_MIPS
 }
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_UTILS_H_