Reapply CL "Option to truncate integers to 64 bits, part 2"

runtime/lib/integers.cc

Index: runtime/lib/integers.cc
diff --git a/runtime/lib/integers.cc b/runtime/lib/integers.cc
index a8d093956acedc415b2194f1b7f04293fca611e1..544319780193ff9c80d32dbd57e2cf95b3a49dbc 100644
--- a/runtime/lib/integers.cc
+++ b/runtime/lib/integers.cc
@@ -27,7 +27,7 @@ DEFINE_FLAG(bool,
 // when it could have been a Smi.
 static bool CheckInteger(const Integer& i) {
   if (i.IsBigint()) {
-    ASSERT(!FLAG_limit_ints_to_64_bits);
+    ASSERT(!Bigint::IsDisabled());
     const Bigint& bigint = Bigint::Cast(i);
     return !bigint.FitsIntoSmi() && !bigint.FitsIntoInt64();
   }
@@ -272,7 +272,7 @@ static RawInteger* ShiftOperationHelper(Token::Kind kind,
   } else {
     ASSERT(value.IsBigint());
   }
-  ASSERT(!FLAG_limit_ints_to_64_bits);
+  ASSERT(!Bigint::IsDisabled());
   return Integer::null();
 }
 
@@ -387,9 +387,7 @@ DEFINE_NATIVE_ENTRY(Bigint_getDigits, 1) {
 }
 
 DEFINE_NATIVE_ENTRY(Bigint_allocate, 4) {
-  // TODO(alexmarkov): Revise this assertion if this native method can be used
-  // to explicitly allocate Bigint objects in --limit-ints-to-64-bits mode.
-  ASSERT(!FLAG_limit_ints_to_64_bits);
+  ASSERT(!Bigint::IsDisabled());
   // First arg is null type arguments, since class Bigint is not parameterized.
   const Bool& neg = Bool::CheckedHandle(arguments->NativeArgAt(1));
   const Smi& used = Smi::CheckedHandle(arguments->NativeArgAt(2));