RFR: 8364970: Redo JDK-8327381 by updating the CmpU type instead of the Bool type

[Francisco Ferrari Bihurriet]

On Wed, 6 Aug 2025 23:33:23 GMT, Francisco Ferrari Bihurriet <fferrari at openjdk.org> wrote:

> Hi, this pull request is a second take of 1383fec41756322bf2832c55633e46395b937b40, by updating the `CmpUNode` type as either `TypeInt::CC_LE` (case 1a) or `TypeInt::CC_LT` (case 1b) instead of updating the `BoolNode` type as `TypeInt::ONE`.
> 
> With this approach a56cd371a2c497e4323756f8b8a08a0bba059bf2 becomes unnecessary. Additionally, having the right type in `CmpUNode` could potentially enable further optimizations.
> 
> #### Testing
> 
> In order to evaluate the changes, the following testing has been performed:
> 
> * `jdk:tier1` (see [GitHub Actions run](https://github.com/franferrax/jdk/actions/runs/16789994433))
> * [`TestBoolNodeGVN.java`](https://github.com/openjdk/jdk/blob/jdk-26+9/test/hotspot/jtreg/compiler/c2/gvn/TestBoolNodeGVN.java), created for [JDK-8327381: Refactor type-improving transformations in BoolNode::Ideal to BoolNode::Value](https://bugs.openjdk.org/browse/JDK-8327381) (1383fec41756322bf2832c55633e46395b937b40)
>     * I also checked it breaks if I remove the `CmpUNode::Value_cmpu_and_mask` call
> * Private reproducer for [JDK-8349584: Improve compiler processing](https://bugs.openjdk.org/browse/JDK-8349584) (a56cd371a2c497e4323756f8b8a08a0bba059bf2)
> * A local slowdebug run of the `test/hotspot/jtreg/compiler/c2` category on _Fedora Linux x86_64_
>     * Same results as with `master` (f95af744b07a9ec87e2507b3d584cbcddc827bbd)

@rwestrel / @TobiHartmann / @chhagedorn: this is my first contribution in C2 besides [OJVG](https://openjdk.org/groups/vulnerability/) reviews and backports, please let me know if I should be testing something else.

@tabjy: as the original 1383fec41756322bf2832c55633e46395b937b40 author, I would greatly appreciate an additional review from you.

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PR Comment: https://git.openjdk.org/jdk/pull/26666#issuecomment-3163534821