RFR: 8315066: Add unsigned bounds and known bits to TypeInt/Long [v13]

[Vladimir Kozlov]

On Thu, 5 Sep 2024 15:41:30 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 incrementally with two additional commits since the last revision:
> 
>  - rename tests
>  - more explanation

src/hotspot/share/opto/type.cpp line 1705:

> 1703: bool TypeInt::empty(void) const {
> 1704:   return false;
> 1705: }

I would like to see assert(_lo <= _hi) here since you unconditionally return `false`.

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PR Review Comment: https://git.openjdk.org/jdk/pull/17508#discussion_r1745842143