Eli Friedman <eli.friedman at gmail.com> writes:
>> Yes, we know the high bits are the same but it's surprising to me that
>> this would be represented as "undef."
>
> We don't represent that as undef in the IR; constant folding will fold
> "sext i32 undef to i64" to zero, not undef.
Ok, so why the fuss over sext?
-Dave