RFR: 8315066: Add unsigned bounds and known bits to TypeInt/Long [v15]

[Jasmine Karthikeyan]

On Thu, 5 Sep 2024 18:12:55 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:
> 
>   fix builds

src/hotspot/share/opto/rangeinference.cpp line 470:

> 468:   // Neither contains each other, weird?
> 469:   // fatal("Integer value range is not subset");
> 470:   // return this;

This looks like leftover dead code.

src/hotspot/share/opto/type.hpp line 621:

> 619:   bool contains(const TypeInt* t) const;
> 620:   // Excluding the cases where this and t are the same
> 621:   bool properly_contains(const TypeInt* t) const;

It doesn't look like this method is used in the changeset (or at least, I couldn't find any references with grep.) I think you could potentially remove it.

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PR Review Comment: https://git.openjdk.org/jdk/pull/17508#discussion_r1747853142
PR Review Comment: https://git.openjdk.org/jdk/pull/17508#discussion_r1747687314