RFR: 8294588: Auto vectorize half precision floating point conversion APIs [v7]

[Vladimir Kozlov]

On Thu, 8 Dec 2022 00:27:42 GMT, Sandhya Viswanathan <sviswanathan at openjdk.org> wrote:

>>> @vnkozlov I have updated the test case to work with AVX=1.
>> 
>> Can you explain what was wrong with AVX1 and what change fixed the issue?
>> I see you renamed classes and addressed @fg1417 comment about `opcode`. It is not clear to me what fixed AVX1 issue.
>
> @vnkozlov The test was failing earlier with -XX:UseAVX=1 because the right implemented() check was not happening as Fei Gao explained. In vectornode.cpp, method VectorCastNode::implemented() was not getting the right vopc (VectorCastF2X, VectorCastS2X instead of VectorCastF2HF and VectorCastHF2F) after call to VectorCastNode::opcode() and so the Matcher::match_rule_supported_superword() was called with wrong vopc. This is now fixed as Smita has fixed the VectorCastNode::opcode() and VectorCastNode::implemented().

Thank you @sviswa7 for explanation! Good.

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PR: https://git.openjdk.org/jdk/pull/11471