RFR: 8332442: C2: refactor Mod cases in Compile::final_graph_reshaping_main_switch() [v7]

[Emanuel Peter]

On Wed, 11 Sep 2024 20:26:43 GMT, Kangcheng Xu <kxu at openjdk.org> wrote:

>> Hello all. This patch addresses [JDK-8332442](https://bugs.openjdk.org/browse/JDK-8332442) and refactors `Op_ModI`/`Op_ModL`/`Op_UModI`/`Op_UModL` cases in `DIVMOD` transforamtions. The purpose of the transformation to convert adjacent div `/`  and mod `%` operations of the same operands into one should the platform support this feature (e.g., x86-64).
>> 
>> I took the liberty adding _signed_ DIVMOD nodes (i.e., `DIV_MOD_I` and `DIV_MOD_L`) to the `IRNode` class constants as they are previously missing. Please let me know if they were left intentionally and if there are any other concerns. Thanks!
>> 
>> ~This will be a draft PR before GHA tests are confirmed passing.~
>
> Kangcheng Xu has updated the pull request incrementally with one additional commit since the last revision:
> 
>   format comments, add @bug, avoid zero divisor

test/hotspot/jtreg/compiler/c2/TestDivModNodes.java line 36:

> 34:  * @summary Test that DIV and MOD nodes are converted into DIVMOD where possible
> 35:  * @library /test/lib /
> 36:  * @requires vm.compiler2.enabled

Is `C2` really required for this test? Or could another compiler also benefit from your test?

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PR Review Comment: https://git.openjdk.org/jdk/pull/20877#discussion_r1761357488