Integrated: 8371955: Support AVX10 floating point comparison instructions

[Mohamed Issa]

On Sun, 16 Nov 2025 03:48:31 GMT, Mohamed Issa <missa at openjdk.org> wrote:

> 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

This pull request has now been integrated.

Changeset: 161aa5d5
Author:    Mohamed Issa <missa at openjdk.org>
Committer: Sandhya Viswanathan <sviswanathan at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/161aa5d52865295059f9506b2ba4ffc4b98324de
Stats:     876 lines in 10 files changed: 677 ins; 105 del; 94 mod

8371955: Support AVX10 floating point comparison instructions

Reviewed-by: epeter, sviswanathan, sparasa

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