X64: Fix bugs affecting Win64.

test/cctest/test-api.cc

Index: test/cctest/test-api.cc
diff --git a/test/cctest/test-api.cc b/test/cctest/test-api.cc
index 2a35014aa8d2ec39362796e6ddde99748c189a89..1d1874c4f9a8dcc943d7462b07bba244aaca347c 100644
--- a/test/cctest/test-api.cc
+++ b/test/cctest/test-api.cc
@@ -728,7 +728,10 @@ THREADED_TEST(BigInteger) {
   LocalContext env;
   // We cannot add one to a Smi::kMaxValue without wrapping.
   if (i::kSmiValueSize < 32) {
-    int32_t value = i::Smi::kMaxValue + 1;
+    // The casts allow this to compile, even if Smi::kMaxValue is 2^31-1.
+    // The code will not be run in that case, due to the "if" guard.
+    int32_t value =
+        static_cast<int32_t>(static_cast<uint32_t>(i::Smi::kMaxValue) + 1);
     CHECK(value > i::Smi::kMaxValue);
     CHECK(!i::Smi::IsValid(value));
     Local<v8::Integer> value_obj = v8::Integer::New(value);