[aarch64-port-dev ] RFR(S) 8248660: AArch64: Use MSVC built-ins where applicable

[Kim Barrett]

> On Jul 14, 2020, at 5:26 PM, Monica Beckwith <Monica.Beckwith at microsoft.com> wrote:
> 
> Hello all,
> 
> We are looking at utilizing MSVC built-ins as applicable. Please review the following:
> 
> JBS: https://bugs.openjdk.java.net/browse/JDK-8248660
> Webrev: http://cr.openjdk.java.net/~mbeckwit/8248660/webrev.00/
> 
> Regards,
> Monica

There is a general preference in HotSpot code toward avoiding
toolchain-specific conditional compilation in shared code. (Obviously
this is not a hard and fast rule.) This is even called out in the
HotSpot Style Guide. Before the Windows/MSVC/aarch64 port the code
being modified by this change is gcc-specific rather than shared, but
with that port it becomes shared.

I think the "normal" way to handle something like this would be to
move the current code to os_cpu/linux_aarch64 and have the new
MSVC/aarch64 port provide similar functionality in it's own
os_cpu/windows_aarch64 file.

I would be okay with moving the existing code as a preperatory
"cleanup", rather than having it be part of the windows_aarch64
porting changeset. Others might have a different opinion about that.