RFR: 8315066: Add unsigned bounds and known bits to TypeInt/Long [v7]

[Quan Anh Mai]

On Tue, 3 Sep 2024 14:27:22 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> Quan Anh Mai has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 11 commits:
>> 
>>  - fix compile errors
>>  - Merge branch 'master' into unsignedbounds
>>  - add comments
>>  - Merge branch 'master' into unsignedbounds
>>  - fix release build
>>  - add comments, group arguments to reduce C-style reference passing arguments
>>  - fix tests, add verify
>>  - add unit tests
>>  - fix template parameter
>>  - refactor
>>  - ... and 1 more: https://git.openjdk.org/jdk/compare/d8e4d3f2...d5ad9f1a
>
> What are your thoughts on how we are going to debug-print the new int-type? We probably do not always want to print the KnownBits, in general that is way too verbose. But in some alignment example, it would be nice to know that it is the `int/long` range, but the lowest 3 bits are always zero, hence 8 byte aligned.

@eme64 I have just found out a proof for the `adjust_bounds_from_bits`. It seems more rigorous and easier to understand.

@vnkozlov It is because the result of a `make` can be not a `TypeInt` but an empty type. It would be possible to have a `TypeInt` instance representing the empty set. However, we expose `_lo` and `_hi`, and accessing them of an empty set seems to be a nonsensical operation and potentially dangerous. As a result, I think it is safer we return `Type::TOP` for the empty set.

-------------

PR Comment: https://git.openjdk.org/jdk/pull/17508#issuecomment-2332074013