8297549: RISC-V: Add support for Vector API vector load const operation

[DingliZhang]

The instruction which is matched VectorLoadConst will create index starting from 0 and incremented by 1. In detail, the instruction populates the destination vector by setting the first element to 0 and monotonically incrementing the value by 1 for each subsequent element.

We can add support of VectorLoadConst for RISC-V by vid.v . It was implemented by referring to RVV v1.0 [1].

We can use the JMH test from #10332. Tests are performed on qemu with parameter -cpu rv64,v=true,vlen=256,vext_spec=v1.0. By adding the -XX:+PrintAssembly, the compilation log of floatIndexVector is as follows:

120     vloadcon V2	# generate iota indices
12c     vfmul.vv V1, V2, V1	#@vmulF
134     vfmv.v.f  V2, F8	#@replicateF
13c     vfadd.vv V1, V2, V1	#@vaddF

The above nodes match the logic of Compute indexes with "vec + iota * scale" in #10332, which is the operation corresponding to addIndex in benchmark:

jdk/test/micro/org/openjdk/bench/jdk/incubator/vector/IndexVectorBenchmark.java

Lines 92 to 97 in d610211

	@Benchmark
	public void floatIndexVector() {
	for (int i = 0; i < size; i += fspecies.length()) {
	((FloatVector) fspecies.broadcast(0).addIndex(i % 5)).intoArray(fa, i);
	}
	}

At the same time, the following assembly code will be generated when running the floatIndexVector case, there will be one more instruction than intIndexVector:

 0x000000401443cc9c:   .4byte	0x10072d7
 0x000000401443cca0:   .4byte	0x5208a157
 0x000000401443cca4:   .4byte	0x4a219157

0x10072d7/0x5208a157 is the machine code for vsetvli/vid.v and 0x4a219157 is the additional machine code for vfcvt.f.x.v, which are the opcodes generated by is_floating_point_type(bt):

    if (is_floating_point_type(bt)) {
      __ vfcvt_f_x_v(as_VectorRegister($dst$$reg), as_VectorRegister($dst$$reg));
    }

After we implement these nodes, by using -XX:+UseRVV, the number of assembly instructions is reduced by about ~50% because of the different execution paths with the number of loops, similar to AddTest [3].

[1] https://github.com/riscv/riscv-v-spec/blob/v1.0/v-spec.adoc
[2] https://github.com/openjdk/jdk/blob/857b0f9b05bc711f3282a0da85fcff131fffab91/test/micro/org/openjdk/bench/jdk/incubator/vector/IndexVectorBenchmark.java
[3] https://github.com/zifeihan/vector-api-test-rvv/blob/master/vector-api-rvv-performance.md

Please take a look and have some reviews. Thanks a lot.

Testing:

• hotspot and jdk tier1 without new failures (release with UseRVV on QEMU)
• hotspot, jdk and langtools tier2 without new failures (release with UseRVV on QEMU)
• test/jdk/jdk/incubator/vector/* (fastdebug/release with UseRVV on QEMU)

---

Progress

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Issue

• JDK-8297549: RISC-V: Add support for Vector API vector load const operation

Reviewers

• Fei Yang (@RealFYang - Reviewer)
• Gui Cao (@zifeihan - Author)

Reviewing

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Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk pull/11344/head:pull/11344
$ git checkout pull/11344

Update a local copy of the PR:
$ git checkout pull/11344
$ git pull https://git.openjdk.org/jdk pull/11344/head

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Checkout this PR locally:
$ git pr checkout 11344

View PR using the GUI difftool:
$ git pr show -t 11344

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Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/11344.diff

[bridgekeeper]

👋 Welcome back dzhang! 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]

@DingliZhang The following label will be automatically applied to this pull request:

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[mlbridge]

Webrevs

• 00: Full (77f76070)

[VladimirKempik]

Can you also run whole tier2 please ?

[DingliZhang]

Can you also run whole tier2 please ?

Thank you for your suggestion, of course! I will add the results of whole tier2 later.

[openjdk]

@DingliZhang This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8297549: RISC-V: Add support for Vector API vector load const operation

Reviewed-by: fyang, gcao

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 136 new commits pushed to the master branch:

• 9bbcb54: 8297784: Optimize @stable field for Method.isCallerSensitive
• 11ba759: 8297992: Tests fail after JDK-8297215 due to lack of @enablePreview
• b035056: 8297455: Use the official ToolProvider API to call javac
• 257aa15: 8297444: Refactor the javacserver build tool
• e846b04: 8297875: jar should not compress the manifest directory entry
• 82031d3: 8297294: compiler/c2/irTests/TestMulNodeIdealization.java failed compilation
• 337ca10: 8297978: Exclude vmTestbase/nsk/stress/except/except012.java until 8297977 is fixed
• 770ff5a: 8297215: Update libs tests to use @enablePreview
• c69aa42: 8297968: Crash in PrintOptoAssembly
• 5a5ced3: 8297830: aarch64: Make Address a discriminated union internally
• ... and 126 more: https://git.openjdk.org/jdk/compare/09ac9eb5638400c840c3c31f022d4737b41761b1...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

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➡️ To flag this PR as ready for integration with the above commit message, type /integrate in a new comment. (Afterwards, your sponsor types /sponsor in a new comment to perform the integration).

[DingliZhang]

Can you also run whole tier2 please ?

Hi @VladimirKempik I've run tier2 and updated the test status at the top of the page.

[zifeihan]

LGTM, thanks

[DingliZhang]

@VladimirKempik @RealFYang @zifeihan Thanks for the review!
/integrate

[openjdk]

@DingliZhang
Your change (at version 77f7607) is now ready to be sponsored by a Committer.

[RealFYang]

/sponsor

[openjdk]

Going to push as commit 687fd71.
Since your change was applied there have been 137 commits pushed to the master branch:

• d50015a: 8297715: RISC-V: C2: Use single-bit instructions from the Zbs extension
• 9bbcb54: 8297784: Optimize @stable field for Method.isCallerSensitive
• 11ba759: 8297992: Tests fail after JDK-8297215 due to lack of @enablePreview
• b035056: 8297455: Use the official ToolProvider API to call javac
• 257aa15: 8297444: Refactor the javacserver build tool
• e846b04: 8297875: jar should not compress the manifest directory entry
• 82031d3: 8297294: compiler/c2/irTests/TestMulNodeIdealization.java failed compilation
• 337ca10: 8297978: Exclude vmTestbase/nsk/stress/except/except012.java until 8297977 is fixed
• 770ff5a: 8297215: Update libs tests to use @enablePreview
• c69aa42: 8297968: Crash in PrintOptoAssembly
• ... and 127 more: https://git.openjdk.org/jdk/compare/09ac9eb5638400c840c3c31f022d4737b41761b1...master

Your commit was automatically rebased without conflicts.

[openjdk]

@RealFYang @DingliZhang Pushed as commit 687fd71.

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