RFR: 8315066: Add unsigned bounds and known bits to TypeInt/Long [v20]

[Emanuel Peter]

On Wed, 18 Sep 2024 20:29:32 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) == ones`. 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 canonicalize 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 incrementally with one additional commit since the last revision:
> 
>   add comments, refactor functions to helper class

src/hotspot/share/opto/rangeinference.cpp line 118:

> 116:     // new lo (11000000 -> 11001000 -> 11001010). The final value is our
> 117:     // result.
> 118:     // Implementationwise, from 11000000 we can just | with ones to obtain the

Suggestion:

    // Implementationwise, from 11000000 we can just OR with ones to obtain the

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PR Review Comment: https://git.openjdk.org/jdk/pull/17508#discussion_r1767015403