MIPS: Fix NaN value inconsistency with snapshots (alternate implementation).

src/serialize.cc

Index: src/serialize.cc
diff --git a/src/serialize.cc b/src/serialize.cc
index 01d5f1c7bcb034efd6a4f95c1094a4502a0001ed..0cc12528cd2dbecadc163f9a1d61a07b65089e8f 100644
--- a/src/serialize.cc
+++ b/src/serialize.cc
@@ -1444,6 +1444,21 @@ void Serializer::ObjectSerializer::Serialize() {
     sink_->PutSection(space, "NewPageSpace");
   }
 
+#ifdef V8_TARGET_ARCH_MIPS
+#define MIPS_QNAN_HI 0x7ff7ffff
+#define MIPS_QNAN_LO 0xffffffff
+  // Mips has a different encoding of qNaN than ia32, so any heap NaN built
+  // with simulator must be re-encoded for the snapshot. Performance hit not
+  // critical at mksnapshot/build time.
+  if (object_->IsNaN()) {
+    uint64_t mips_qnan_bits =
+        (static_cast<uint64_t>(MIPS_QNAN_HI) << 32) | MIPS_QNAN_LO;
+    Address value_ptr = (reinterpret_cast<byte*>(object_) +
+        HeapNumber::kValueOffset - kHeapObjectTag);
+    memcpy(value_ptr, &mips_qnan_bits, sizeof(mips_qnan_bits));
+  }
+#endif  // V8_TARGET_ARCH_MIPS
+
   // Serialize the map (first word of the object).
   serializer_->SerializeObject(object_->map(), kPlain, kStartOfObject);