RFR: 8315066: Add unsigned bounds and known bits to TypeInt/Long [v22]

[Emanuel Peter]

On Thu, 19 Sep 2024 17:12:22 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:
> 
>   formality

src/hotspot/share/opto/rangeinference.cpp line 65:

> 63: };
> 64: 
> 65: // Find the minimum value that is not less than lo and satisfies bits.

What happens if this is impossible? Imagine lo is `max_uint = FFFFFFFF`, but the known bits know that some specific bit must be zero? Or is there some guarantee that this will never happen? Can we have an assert for that?

src/hotspot/share/opto/rangeinference.cpp line 90:

> 88:   }
> 89: 
> 90:   /*

Everywhere else you use `//`, and that seems to be generally our style, so I'd keep it consistent ;)

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PR Review Comment: https://git.openjdk.org/jdk/pull/17508#discussion_r1767404352
PR Review Comment: https://git.openjdk.org/jdk/pull/17508#discussion_r1767405832