RFR: 8353686: Optimize Math.cbrt for x86 64 bit platforms [v4]
Mohamed Issa
duke at openjdk.org
Wed May 28 18:39:13 UTC 2025
> The goal of this PR is to implement an x86_64 intrinsic for java.lang.Math.cbrt() using libm. There is a new set of micro-benchmarks are included to check the performance of specific input value ranges to help prevent regressions in the future.
>
> The command to run all range specific micro-benchmarks is posted below.
>
> `make test TEST="micro:CbrtPerf.CbrtPerfRanges"`
>
> The results of all tests posted below were captured with an [Intel® Xeon 6761P](https://www.intel.com/content/www/us/en/products/sku/241842/intel-xeon-6761p-processor-336m-cache-2-50-ghz/specifications.html) using [OpenJDK v25-b21](https://github.com/openjdk/jdk/releases/tag/jdk-25%2B21) as the baseline version.
>
> For performance data collected with the new built in range micro-benchmark, see the table below. Each result is the mean of 8 individual runs, and the input ranges used match those from the original Java implementation. Overall, the intrinsic provides a major uplift of 169% when very small inputs are used and a more modest uplift of 45% for all other inputs.
>
> | Input range(s) | Baseline throughput (ops/ms) | Intrinsic throughput (ops/ms) | Speedup |
> | :-------------------------------------: | :-------------------------------: | :-------------------------------: | :---------: |
> | [-2^(-1022), 2^(-1022)] | 6568 | 17678 | 2.69x |
> | (-INF, -2^(-1022)], [2^(-1022), INF) | 138932 | 200897 | 1.45x |
>
> Finally, the `jtreg:test/jdk/java/lang/Math/CubeRootTests.java` test passed with the changes.
Mohamed Issa has updated the pull request incrementally with four additional commits since the last revision:
- Remove comment mentioning invalid exception when NaN input is provided
- Use rcx as base and r8 as index for address calculations in certain cbrt stub generator instructions
- Remove unnecessary unpckhpd and unpcklpd definitions in macro-assembler header file
- Remove unnecessary movapd definitions in macro-assembler header file
-------------
Changes:
- all: https://git.openjdk.org/jdk/pull/24470/files
- new: https://git.openjdk.org/jdk/pull/24470/files/57412f0d..ff4d4f22
Webrevs:
- full: https://webrevs.openjdk.org/?repo=jdk&pr=24470&range=03
- incr: https://webrevs.openjdk.org/?repo=jdk&pr=24470&range=02-03
Stats: 10 lines in 2 files changed: 0 ins; 4 del; 6 mod
Patch: https://git.openjdk.org/jdk/pull/24470.diff
Fetch: git fetch https://git.openjdk.org/jdk.git pull/24470/head:pull/24470
PR: https://git.openjdk.org/jdk/pull/24470
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