[x64] Fixed a rounding error on x64 for the Uint64ToF64 conversion.

test/cctest/compiler/value-helper.h

Index: test/cctest/compiler/value-helper.h
diff --git a/test/cctest/compiler/value-helper.h b/test/cctest/compiler/value-helper.h
index 20be67a97506f25a3f8095f455b16c1f538b36f8..6a9df71e2e48b877b42317651c4a9b2f7d9d4bb9 100644
--- a/test/cctest/compiler/value-helper.h
+++ b/test/cctest/compiler/value-helper.h
@@ -159,7 +159,9 @@ class ValueHelper {
         0x00003fff,         0x00001fff,         0x00000fff,
         0x000007ff,         0x000003ff,         0x000001ff,
         0x00003fffffffffff, 0x00001fffffffffff, 0x00000fffffffffff,
-        0x000007ffffffffff, 0x000003ffffffffff, 0x000001ffffffffff};
+        0x000007ffffffffff, 0x000003ffffffffff, 0x000001ffffffffff,
+        0x8000008000000000, 0x8000008000000001, 0x8000000000000400,
+        0x8000000000000401};
     return std::vector<uint64_t>(&kValues[0], &kValues[arraysize(kValues)]);
   }