RFR: 8323429: Missing C2 optimization for FP min/max when both inputs are same

[Roland Westrelin]

On Thu, 11 Apr 2024 12:10:38 GMT, Galder Zamarreño <galder at openjdk.org> wrote:

> Added C2 identity optimization for min/max calls, whereby if both inputs are the same, either is returned.
> 
> It includes an IR test to verify that the optimization gets applied. The optimization applies not only to floating points, but also long and ints. The test includes tests for all of those.
> 
> `BasicDoubleOpTest.vectorMax_8322090` has also been adjusted to match expectations after implementing the optimization.
> 
> I've run hotspot compiler tests successfully on x86_64.

Looks good to me.

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Marked as reviewed by roland (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/18738#pullrequestreview-1994058981