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

[Emanuel Peter]

On Wed, 14 Aug 2024 16:30:26 GMT, Quan Anh Mai <qamai at openjdk.org> wrote:

>> Hi,
>> 
>> This patch adds unsigned bounds and known bits constraints to TypeInt and TypeLong. This opens more transformation opportunities in an elegant manner as well as helps avoid some ad-hoc rules in Hotspot.
>> 
>> In general, a TypeInt/Long represents a set of values x that satisfies: x s>= lo && x s<= hi && x u>= ulo && x u<= uhi && (x & zeros) == 0 && (~x & ones) == 0. These constraints are not independent, e.g. an int that lies in [0, 3] in signed domain must also lie in [0, 3] in unsigned domain and have all bits but the last 2 being unset. As a result, we must normalize the constraints (tighten the constraints so that they are optimal) before constructing a TypeInt/Long instance.
>> 
>> This is extracted from #15440 , node value transformations are left for later PRs. I have also added unit tests to verify the soundness of constraint normalization.
>> 
>> Please kindly review, thanks a lot.
>> 
>> Testing
>> 
>> - [x] GHA
>> - [x] Linux x64, tier 1-4
>
> 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.

test/hotspot/gtest/opto/test_rangeinference.cpp line 148:

> 146:   test_normalize_constraints_random<jint, juint>();
> 147:   test_normalize_constraints_random<jlong, julong>();
> 148: }

I would appreciate it if there were some explicit examples with explicit result verification. Just to make sure the methods are not systematically wrong in some silly way.

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PR Comment: https://git.openjdk.org/jdk/pull/17508#issuecomment-2326671282
PR Review Comment: https://git.openjdk.org/jdk/pull/17508#discussion_r1742176314