RFR: 8300253: Introduce AArch64 nzcv accessors

[Andrew Haley]

On Tue, 17 Jan 2023 13:47:26 GMT, Erik Österlund <eosterlund at openjdk.org> wrote:

> Some code, such as verification code, might want to run without changing the state of the system. To do that, it's useful to be able to get and set the nzcv flags. This enhancement aims at adding accessors for that.

src/hotspot/cpu/aarch64/macroAssembler_aarch64.hpp line 591:

> 589:     msr(0b011, 0b0100, 0b0010, 0b000, reg);
> 590:   }
> 591: 

We've tried never to to add such things speculatively, as much as anything else because it's impossible to test.

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PR: https://git.openjdk.org/jdk/pull/12038