RFR: 8328998: Encoding support for Intel APX extended general-purpose registers [v15]

[Jatin Bhateja]

On Wed, 8 May 2024 20:27:29 GMT, Steve Dohrmann <duke at openjdk.org> wrote:

> UseAPX

Yes, attaching a test depicting incorrectness with UseAVX=2 for SHLX which is a legacy map 2 instruction promotable to extended EVEX with EGPR operands.
[shift_left_APX.txt](https://github.com/openjdk/jdk/files/15261495/shift_left_APX.txt)

It will not be appropriate to modify VM_Version::supports_evex for APX feature since its used for constraining dynamic register classes associated with vector operands.

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PR Review Comment: https://git.openjdk.org/jdk/pull/18476#discussion_r1595320541