RFR: 8241502: C2: Migrate x86_64.ad to MacroAssembler [v8]

[Vladimir Kozlov]

On Thu, 22 Apr 2021 22:31:24 GMT, John Tortugo <github.com+2249648+JohnTortugo at openjdk.org> wrote:

>> The operand encoding of SETNE r/m8 is just 0b11.000.000 AFAIU, and not 0b11.100.000 as in the previous code. I found this difference while comparing the bytes emitted by instructions encoded using "opcode(...)" with instructions emitted by MacroAssembler.
>
> I.e., I basically patched the MacroAssembler routine to emit an instruction that matched this: https://github.com/openjdk/jdk/blob/b84f6901275aedfeb59438898846b6e69ced316d/src/hotspot/cpu/x86/x86_64.ad#L2750

Got it. I submitted new testing.

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PR: https://git.openjdk.java.net/jdk/pull/2420