8275643: C2's unaryOp vector intrinsic does not properly handle LongVector.neg

[TobiHartmann]

Code in LongVector::lanewiseTemplate currently implements the NEG operation as a SUB and has a corresponding FIXME comment:

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

Lines 534 to 541 in e9934e1

	} else if (op == NEG) {
	// FIXME: Support this in the JIT.
	return broadcast(0).lanewise(SUB, this);
	}
	}
	int opc = opCode(op);
	return VectorSupport.unaryOp(
	opc, getClass(), null, long.class, length(),

The implicit assumption is that since we will never pass NEG to VectorSupport.unaryOp in line 540, the corresponding C2 intrinsic does not need to handle that case. That's not guaranteed though because C2 might still compile that path when not being able to prove that it's unreachable at parse time. As a result, we then assert in the intrinsic because the negation operation on a long vector is currently not supported (i.e. there is no Op_NegVL). I propose to simply handle this case in VectorSupport::vop2ideal. We will then bail out from intrinsification with operation not supported: opc=NegL bt=long because VectorNode::opcode returns 0:

jdk/src/hotspot/share/opto/vectorIntrinsics.cpp

Lines 390 to 394 in e9934e1

	int opc = VectorSupport::vop2ideal(opr->get_con(), elem_bt);
	int sopc = VectorNode::opcode(opc, elem_bt);
	if ((opc != Op_CallLeafVector) && (sopc == 0)) {
	if (C->print_intrinsics()) {
	tty->print_cr(" ** operation not supported: opc=%s bt=%s", NodeClassNames[opc], type2name(elem_bt));

Question to the Vector API experts: There are other FIXME: Support this in the JIT comments in the code. Do these code paths suffer from similar issues? Is there a tracking RFE/bug?

Thanks,
Tobias

---

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Issue

• JDK-8275643: C2's unaryOp vector intrinsic does not properly handle LongVector.neg

Reviewers

• Christian Hagedorn (@chhagedorn - Reviewer)
• Sandhya Viswanathan (@sviswa7 - Reviewer)

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[mlbridge]

Webrevs

• 00: Full (c45cdc1c)

[chhagedorn]

That looks good to me!

[openjdk]

@TobiHartmann 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:

8275643: C2's unaryOp vector intrinsic does not properly handle LongVector.neg

Reviewed-by: chagedorn, sviswanathan

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At the time when this comment was updated there had been 13 new commits pushed to the master branch:

• 29e552c: 8272358: Some tests may fail when executed with other locales than the US
• ce4471f: 8277346: ProblemList 7 serviceability/sa tests on macosx-x64
• 45a60db: 8277045: G1: Remove unnecessary set_concurrency call in G1ConcurrentMark::weak_refs_work
• 6bb0462: 8277224: sun.security.pkcs.PKCS9Attributes.toString() throws NPE
• d8c0280: 8277316: ciReplay: dump_replay_data is not thread-safe
• 007ad7c: 8277303: Terminology mismatch between JLS17-3.9 and SE17's javax.lang.model.SourceVersion method specs
• 8881f29: 8277310: ciReplay: @CPI MethodHandle references not resolved
• 262d070: 8277246: Check for NonRepudiation as well when validating a TSA certificate
• a907b2b: 8276177: nsk/jvmti/RedefineClasses/StressRedefineWithoutBytecodeCorruption failed with "assert(def_ik->is_being_redefined()) failed: should be being redefined to get here"
• b687664: 8277159: Fix java/nio/file/FileStore/Basic.java test by ignoring /run/user/* mount points
• ... and 3 more: https://git.openjdk.java.net/jdk/compare/e9934e1243929514e147ecdd3cefa74168ed0500...master

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[TobiHartmann]

Thanks for the review, Christian!

[sviswa7]

Looks good to me.

[TobiHartmann]

Thanks for the review, Sandhya!

[PaulSandoz]

@sviswa7 @jatin-bhateja any thoughts on the other related FIXMEs brought up by Tobias? e.g.

            if (op == AND_NOT) {
                // FIXME: Support this in the JIT.
                that = that.lanewise(NOT);
                op = AND;

[sviswa7]

@PaulSandoz Those fixme notes are from John, pointing to us where further optimizations are possible and not related to correctness. I also looked at the vop2ideal, it now handles all the opcodes for the relevant data types (inegral/fp).

[PaulSandoz]

@PaulSandoz Those fixme notes are from John, pointing to us where further optimizations are possible and not related to correctness. I also looked at the vop2ideal, it now handles all the opcodes for the relevant data types (inegral/fp).

Thanks, i also looked at vop2ideal and concluded the same.

[TobiHartmann]

Thanks for checking!

[TobiHartmann]

/integrate

[openjdk]

Going to push as commit 47564ca.
Since your change was applied there have been 38 commits pushed to the master branch:

• 2f0bde1: 8277102: Dubious PrintCompilation output
• 839033b: 8276976: Rename LIR_OprDesc to LIR_Opr
• 89b125f: 8275527: Refactor forward pointer access
• 36bd4a3: 8277404: Test VMDeprecatedOptions.java failing with Unable to create shared archive file
• 57eb864: 8276927: [PPC64] Port shenandoahgc to linux on ppc64le
• 8db0c36: 8277414: ProblemList runtime/CommandLine/VMDeprecatedOptions.java on windows-x64
• 03473b4: 8270874: JFrame paint artifacts when dragged from standard monitor to HiDPI monitor
• ce0f00f: 8276093: Improve naming in closures to iterate over card sets
• 5d249c4: 8275071: [macos] A11y cursor gets stuck when combobox is closed
• 354a34e: 8277336: Improve CollectedHeap::safepoint_workers comments
• ... and 28 more: https://git.openjdk.java.net/jdk/compare/e9934e1243929514e147ecdd3cefa74168ed0500...master

Your commit was automatically rebased without conflicts.

[openjdk]

@TobiHartmann Pushed as commit 47564ca.

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