Merge changes up to V8 version 2.1.3 into the partial snapshots

src/conversions-inl.h

Index: src/conversions-inl.h
===================================================================
--- src/conversions-inl.h	(revision 3964)
+++ src/conversions-inl.h	(working copy)
@@ -59,6 +59,32 @@
 }
 
 
+// The fast double-to-unsigned-int conversion routine does not guarantee
+// rounding towards zero.
+static inline unsigned int FastD2UI(double x) {
+  // There is no unsigned version of lrint, so there is no fast path
+  // in this function as there is in FastD2I. Using lrint doesn't work
+  // for values of 2^31 and above.
+
+  // Convert "small enough" doubles to uint32_t by fixing the 32
+  // least significant non-fractional bits in the low 32 bits of the
+  // double, and reading them from there.
+  const double k2Pow52 = 4503599627370496.0;
+  bool negative = x < 0;
+  if (negative) {
+    x = -x;
+  }
+  if (x < k2Pow52) {
+    x += k2Pow52;
+    uint32_t result;
+    memcpy(&result, &x, sizeof(result));  // Copy low 32 bits.
+    return negative ? ~result + 1 : result;
+  }
+  // Large number (outside uint32 range), Infinity or NaN.
+  return 0x80000000u;  // Return integer indefinite.
+}
+
+
 static inline double DoubleToInteger(double x) {
   if (isnan(x)) return 0;
   if (!isfinite(x) || x == 0) return x;