RFR: 8326135: Enhance adlc to report unused operands [v2]

[kuaiwei]

On Wed, 21 Feb 2024 15:59:37 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> Thanks for suggestion. I added the example in comments.
>
> Good. Please update comment for vectors too (add `only`):
> 
> // special generic vector operands only used in Matcher::pd_specialize_generic_vector_operand
> 
> 
> I will submit our testing meanwhile.

comments fixed

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PR Review Comment: https://git.openjdk.org/jdk/pull/17910#discussion_r1498572930