Make SNaN verification universal for all arches.

The mips HW prior to revision 5 has opposite encoding for NaNs.

TEST=mjsunit/regress/*, regress-1167, regress-undefined-nan2
BUG=

Review URL: https://codereview.chromium.org/912833003

Cr-Commit-Position: refs/heads/master@{#26568}

src/objects-debug.cc

@@ -390,8 +390,12 @@ void FixedDoubleArray::FixedDoubleArrayVerify() {
   for (int i = 0; i < length(); i++) {
     if (!is_the_hole(i)) {
       uint64_t value = get_representation(i);
-      CHECK((value & V8_UINT64_C(0x7FF8000000000000)) !=
-                V8_UINT64_C(0x7FF0000000000000) ||
+      uint64_t unexpected =
+          bit_cast<uint64_t>(std::numeric_limits<double>::quiet_NaN()) &
+          V8_UINT64_C(0x7FF8000000000000);
+      // Create implementation specific sNaN by inverting relevant bit.
+      unexpected ^= V8_UINT64_C(0x0008000000000000);
+      CHECK((value & V8_UINT64_C(0x7FF8000000000000)) != unexpected ||
             (value & V8_UINT64_C(0x0007FFFFFFFFFFFF)) == V8_UINT64_C(0));
     }
   }

src/objects-inl.h

@@ -2335,7 +2335,7 @@ void FixedDoubleArray::set(int index, double value) {
          map() != GetHeap()->fixed_array_map());
   int offset = kHeaderSize + index * kDoubleSize;
   if (std::isnan(value)) {
-    WRITE_UINT64_FIELD(this, offset, V8_UINT64_C(0xFFFFFFFFFFFFFFFF));
+    WRITE_DOUBLE_FIELD(this, offset, std::numeric_limits<double>::quiet_NaN());
   } else {
     WRITE_DOUBLE_FIELD(this, offset, value);
   }