RFR: 8328998: Encoding support for Intel APX extended general-purpose registers [v23]

[Vladimir Kozlov]

On Tue, 21 May 2024 16:53:33 GMT, Steve Dohrmann <duke at openjdk.org> wrote:

>> src/hotspot/cpu/x86/assembler_x86.cpp line 2036:
>> 
>>> 2034:   InstructionMark im(this);
>>> 2035:   if (needs_eevex(crc, adr.base(), adr.index())) {
>>> 2036:     assert(UseAPX, "extended gpr use requires UseAPX and UseAVX > 2");
>> 
>> Maybe here the "and" makes sense, but not sure.
>
> Yes, "and" is technically correct.  APX includes instructions that require AVX 3 (evex) encoding for extended gpr use, together with +UseAPX.

You don't need to say "and UseAVX >2" because you switch off `UseAPX` in `vm_version_x86.cpp` when `UseAVX < 3`.

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PR Review Comment: https://git.openjdk.org/jdk/pull/18476#discussion_r1608689933