8305324: C2: Wrong execution of vectorizing Interger.reverseBytes

[quadhier]

This patch should fix JDK-8305324.

SuperWord::compute_vector_element_type() propagates backward a narrower integer type when the upper bits of the value are not needed. However, Integer.reverseBytes() depends on higher order bits of an integer and should be prevented from being vectorized like Math.abs()( which is Op_AbsI in the following code).

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

Lines 3935 to 3945 in 0243da2

	if (same_type) {
	// In any Java arithmetic operation, operands of small integer types
	// (boolean, byte, char & short) should be promoted to int first. As
	// vector elements of small types don't have upper bits of int, for
	// RShiftI or AbsI operations, the compiler has to know the precise
	// signedness info of the 1st operand. These operations shouldn't be
	// vectorized if the signedness info is imprecise.
	const Type* vt = vtn;
	int op = in->Opcode();
	if (VectorNode::is_shift_opcode(op) || op == Op_AbsI) {
	Node* load = in->in(1);

I have tested this patch for tier 1-3 on x86-64.

---

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Issue

• JDK-8305324: C2: Wrong execution of vectorizing Interger.reverseBytes

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[bridgekeeper]

👋 Welcome back quadhier! 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]

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[mlbridge]

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[quadhier]

Sorry, I forgot to enable the pre-submit test. I will close this PR and create a new one.

[quadhier]

Please refer to the new PR #13406. Thanks.