RFR: 8319973: AArch64: Save and restore FPCR in the call stub

[Andrew Haley]

On Mon, 20 Nov 2023 15:37:59 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

>> On AArch64 we don't save and restore the default floating-point control state when we enter and leave Java code. We really should, because if we're called via the JNI invocation interface with a weird FP control state we'll not be Java compatible.
>
> src/hotspot/cpu/aarch64/stubGenerator_aarch64.cpp line 145:
> 
>> 143:   //      ...
>> 144:   // -29 [ argument word 1      ]
>> 145:   // -28 [ saved Floating-point Control Register ]
> 
> Why the 1-word gap? Alignment?

Yes, exactly. AArch64 stack is 16-aligned, and this is enforced by hardware.

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PR Review Comment: https://git.openjdk.org/jdk/pull/16637#discussion_r1399468749