Option to truncate integers to 64 bits, part 1 (core VM changes)

runtime/vm/flag_list.h

Index: runtime/vm/flag_list.h
diff --git a/runtime/vm/flag_list.h b/runtime/vm/flag_list.h
index 2c327819c2edf3458bafa0de18d7fae51ec573d0..fc6da80c78fb22972c8f849316a11cea16757899 100644
--- a/runtime/vm/flag_list.h
+++ b/runtime/vm/flag_list.h
@@ -96,6 +96,8 @@
   P(link_natives_lazily, bool, false, "Link native calls lazily")              \
   R(limit_ints_to_64_bits, false, bool, false,                                 \

[regis, 2017/07/07 20:10:30]

Do we need to keep this flag? Having both is somewhat confusing.
Or we should name this one more accurately, like
"throw_on_ints_larger_than_64_bits".

[alexmarkov, 2017/07/07 20:46:38]

If you think it is no longer useful, I'll remove it in the future CLs, when I
will revise Integer/Bigint construction and add errors for huge literals (I left
TODOs for them).
Is that OK with you?

[regis, 2017/07/07 21:46:53]

It is OK to keep it for now, but I think we need to rename it to make it clear
that it throws.

     "Throw a RangeError on 64-bit integer overflow");                          \
+  R(truncate_ints_to_64_bits, false, bool, false,                              \
+    "Truncate integers to 64 bits")                                            \
   C(load_deferred_eagerly, true, true, bool, false,                            \
     "Load deferred libraries eagerly.")                                        \
   R(log_marker_tasks, false, bool, false,                                      \