RFR: 8353842: C2: Add graph dumps before and after loop opts phase [v3]

[duke]

On Tue, 8 Apr 2025 14:10:42 GMT, Manuel Hässig <duke at openjdk.org> wrote:

>> This PR adds graph dumps before and after loop optimizations, but only if the compiled method actually contains loops. This helps to distinguish loop optimizations in IGV and to match loop related nodes like opaque template assertion predicates.
>> 
>> I tested this by compiling a few test methods and looking at the ideal graph. Also, I ran tier1 through tier3 and Oracle internal testing.
>
> Manuel Hässig has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix capitalization

@mhaessig 
Your change (at version 951c516e60f248627770df058df07aa6a0a08b48) is now ready to be sponsored by a Committer.

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PR Comment: https://git.openjdk.org/jdk/pull/24509#issuecomment-2791769314