RFR: 8371955: Support AVX10 floating point comparison instructions [v4]

[Mohamed Issa]

> Intel® AVX10 ISA [1] extensions added new floating point comparison instructions. They set the EFLAGS register so that relationships can be tested independently to avoid extra checks when one of the inputs is NaN.
> 
> Most of the work is covered in the architecture definition (`x86.ad`) file. A new comparison operand was created to be used by new CMove and JMP definitions with the APX specific portions of the CMove section being updated to rely on the new instructions because both sets of instructions are always expected to be available on the same platform. New floating point comparison definitions were also added.
> 
> This change uses the new AVX10.2 (UCOMXSS or UCOMXSD) instructions on supported platforms to avoid the extra handling required with existing (UCOMISS or UCOMISD) instructions. To make sure no new failures were introduced, tier1, tier2, and tier3 tests were run on builds with and without the changes. Additionally, the JTREG tests listed below were used to verify correctness with `-XX:-UseAPX` / `-XX:+UseAPX` options. The baseline build used is [OpenJDK v26-b26](https://github.com/openjdk/jdk/releases/tag/jdk-26%2B26).
> 
> 1. `jtreg:test/hotspot/jtreg/compiler/c2/irTests/CMoveLConstants.java`
> 2. `jtreg:test/hotspot/jtreg/compiler/c2/irTests/TestFPComparison.java`
> 3. `jtreg:test/hotspot/jtreg/compiler/intrinsics/math/TestSignumIntrinsic.java`
> 4. `jtreg:test/hotspot/jtreg/compiler/vectorization/TestSignumVector.java`
> 
> Finally, the JMH micro-benchmark listed below was updated to separately exercise CMove and JMP code paths.
> 
> 1. `micro:test/micro/org/openjdk/bench/java/lang/FPComparison.java`
> 
> [1] https://www.intel.com/content/www/us/en/content-details/856721/intel-advanced-vector-extensions-10-2-intel-avx10-2-architecture-specification.html?wapkw=AVX10

Mohamed Issa has updated the pull request incrementally with one additional commit since the last revision:

  Remove extra jump instruction in signum floating point and unify three-way floating point comparison logic in x86.ad

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/28337/files
  - new: https://git.openjdk.org/jdk/pull/28337/files/38735c37..cd7acad7

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=28337&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28337&range=02-03

  Stats: 23 lines in 2 files changed: 9 ins; 11 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/28337.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28337/head:pull/28337

PR: https://git.openjdk.org/jdk/pull/28337