Bug 1741392 introduced a transformation which creates Int64-typed `MBitNot`
nodes. Unfortunately `MBitNot::foldsTo` asserts that its operand is Int32,
and the assertion was not updated. This fix returns from `MBitNot::foldsTo`
immediately in such a case. No folding happens, but it doesn't happen at the
moment anyway, so there's no perf loss. A longer term fix would be to extend
the routine to handle the Int64 case properly.
`MBitNot::writeRecoverData` also assumes -- although without an assertion --
that the operand has Int32 type. However, this is a JS-only path, so we never
expect to see Int64 here. An assertion has nevertheless been added for safety.
Differential Revision: https://phabricator.services.mozilla.com/D132573
da12dd183f