8353786: Migrate Vector API math library support to FFM API #24462

iwanowww · 2025-04-04T22:52:24Z

Migrate Vector API math library (SVML and SLEEF) linkage from native code (in JVM) to Java FFM API.

Since FFM API doesn't support vector calling conventions yet, migration affects only symbol lookup for now. But it still enables significant simplifications on JVM side.

The patch consists of the following parts:

on-demand symbol lookup in Java code replaces eager lookup from native code during JVM startup;
2 new VM intrinsics for vector calls (support unary and binary shapes) (code separated from unary/binary vector operations);
new internal interface to query supported CPU ISA extensions (jdk.incubator.vector.CPUFeatures) used for CPU dispatching.

java.lang.foreign API is used to perform symbol lookup in vector math library, then the address is cached and fed into corresponding JVM intrinsic, so C2 can turn it into a direct vector call in generated code.

Once java.lang.foreign supports vectors & vector calling conventions, VM intrinsics can go away.

Performance is on par with original implementation (tested with microbenchmarks on linux-x64 and macosx-aarch64).

Testing: hs-tier1 - hs-tier6, microbenchmarks (on linux-x64 and macosx-aarch64)

Thanks!

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JDK-8353786: Migrate Vector API math library support to FFM API (Enhancement - P3)

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Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/24462/head:pull/24462
$ git checkout pull/24462

Update a local copy of the PR:
$ git checkout pull/24462
$ git pull https://git.openjdk.org/jdk.git pull/24462/head

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Checkout this PR locally:
$ git pr checkout 24462

View PR using the GUI difftool:
$ git pr show -t 24462

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https://git.openjdk.org/jdk/pull/24462.diff

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bridgekeeper · 2025-04-04T22:53:18Z

👋 Welcome back vlivanov! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

openjdk · 2025-04-04T22:53:50Z

❗ This change is not yet ready to be integrated.
See the Progress checklist in the description for automated requirements.

openjdk · 2025-04-04T22:54:18Z

@iwanowww
The core-libs label was successfully added.

The hotspot-compiler label was successfully added.

liach · 2025-04-04T23:27:11Z

Moving vector API library selection to Java code looks like a right step to me.

iwanowww · 2025-04-05T02:19:06Z

/cc hotspot

openjdk · 2025-04-05T02:20:13Z

@iwanowww
The hotspot label was successfully added.

mlbridge · 2025-04-05T02:42:36Z

Webrevs

minborg · 2025-04-07T06:44:16Z

src/jdk.incubator.vector/share/classes/jdk/incubator/vector/VectorMathLibrary.java

+    Entry<T> constructEntry(Operator op, int opc, VectorSpecies<E> vspecies, IntFunction<T> implSupplier) {
+        if (LIBRARY.isSupported(op, vspecies)) {
+            String symbol = LIBRARY.symbolName(op, vspecies);
+            MemorySegment addr = LOOKUP.find(symbol)


It is better to use LOOKUP.findOrThrow() because it does not require lambda creation.

Thanks, changed as you suggested. I introduced a try-catch block instead.

vnkozlov

Few questions?

vnkozlov · 2025-04-07T17:01:19Z

src/jdk.incubator.vector/share/classes/jdk/incubator/vector/CPUFeatures.java

+        return features.contains(feature.toLowerCase());
+    }
+
+    public static class X64 {


Should we create src/jdk.incubator.vector/cpu/ for CPU specific information? As separate refactoring.

To clarify: are you suggesting to move platform-specific classes into a separate package or platform-specific location?

It does make sense to separate platform-specific parts into their own classes once amount of code grows over some limit. For now it doesn't look too attractive since amount of code is very small.

vnkozlov · 2025-04-07T17:03:17Z

src/jdk.incubator.vector/share/classes/jdk/incubator/vector/VectorMathLibrary.java

+    }
+
+    /**
+     * Naming convention in SVML vector math library.


Does this library has code for all AVX configurations?

Yes, there are 4 configurations (-XX:UseAVX=[0..3]) in total covered by SVML library.

src/jdk.incubator.vector/share/classes/jdk/incubator/vector/CPUFeatures.java

iwanowww · 2025-04-07T23:25:23Z

In addition to addressing review feedback, there are 2 updates:

SVML: I overlooked that 64-bit vectors are covered by original implementation; fixed now;
JVM: features_string to cpu_info_string renaming uniformly across all platforms

iwanowww added 12 commits April 4, 2025 15:40

Remove vector math intrinsics

50210bd

Vector math library

57487c8

VM intrinsics

a92a2a8

VectorMathLib: Migrate to lambdas

714e4d0

cleanup

02802d0

SLEEF improvements

0734e25

fixes

def3434

Update templates

2efdac9

SVML fixes

c74739e

TODO list

2a7006b

Cleanup

70cdd15

CPU features support

0a1bba8

openjdk bot added core-libs [email protected] hotspot-compiler [email protected] labels Apr 4, 2025

Misc fixes and cleanups

fc27aee

iwanowww force-pushed the vector.math.01.java branch from 03c5a8c to fc27aee Compare April 5, 2025 01:30

iwanowww changed the title ~~XXXXXXX: ???~~ 8353786: Migrate Vector API math library support to FFM API Apr 5, 2025

openjdk bot added the hotspot [email protected] label Apr 5, 2025

iwanowww marked this pull request as ready for review April 5, 2025 02:38

openjdk bot added the rfr Pull request is ready for review label Apr 5, 2025

minborg reviewed Apr 7, 2025

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vnkozlov reviewed Apr 7, 2025

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liach reviewed Apr 7, 2025

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src/jdk.incubator.vector/share/classes/jdk/incubator/vector/CPUFeatures.java Outdated Show resolved Hide resolved

iwanowww added 2 commits April 7, 2025 14:31

Reviews and Float64Vector-related fix

368b943

features_string -> cpu_info_string

9a8f620

Fix windows-aarch64 build failure

bb1a11d

Provide feedback

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8353786: Migrate Vector API math library support to FFM API #24462

8353786: Migrate Vector API math library support to FFM API #24462

iwanowww commented Apr 4, 2025 •

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iwanowww commented Apr 7, 2025

8353786: Migrate Vector API math library support to FFM API #24462

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8353786: Migrate Vector API math library support to FFM API #24462

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iwanowww commented Apr 4, 2025 • edited by openjdk bot Loading

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