RFR: 8323429: Missing C2 optimization for FP min/max when both inputs are same [v2]

[Galder Zamarreño]

> 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.

Galder Zamarreño has updated the pull request incrementally with one additional commit since the last revision:

  Small IR test fixes
  
  * Fixed bug ID number.
  * Added test summary.
  * Removed unnecessary @requires.
  * Added @Check methods to verify optimizations return the expected result.

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/18738/files
  - new: https://git.openjdk.org/jdk/pull/18738/files/e8f64095..f3d20ced

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18738&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18738&range=00-01

  Stats: 61 lines in 2 files changed: 57 ins; 1 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/18738.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18738/head:pull/18738

PR: https://git.openjdk.org/jdk/pull/18738