RFR: 8280476: [macOS] : hotspot arm64 bug exposed by latest clang

[Daniel D.Daugherty]

On Fri, 28 Jan 2022 17:12:34 GMT, Andrew Haley <aph at openjdk.org> wrote:

>> A trivial fix to solve undefined behavior in src/hotspot/cpu/aarch64/immediate_aarch64.cpp:
>> replicate().
>> 
>> I was not able to reproduce the reported failure using:
>> 
>>   Xcode: Version 13.2.1 (13C100) which includes clang Apple LLVM 13.0.0 (clang-1300.0.29.30)
>> 
>> so I'm moving forward with the proposed fix from a code inspection
>> point of view.
>> 
>> I've tested this fix with Mach5 Tier[1-6]. Tier1 and Tier2 have completed with
>> no failures. Tier[3-6] are still running.
>
> Weird. We can't ever have hit it, or chaos would have ensued.
> 
> I'm going to leave it to Andrew Dinn to review this one.

@theRealAph - Thanks for chiming in on the review thread. This is definitely
weird and I have not been able to reproduce the failure mode. The sighting came
indirectly from someone at Apple via @prrace so we haven't been able to
get better version information (yet).

I look forward to getting a review from @adinn.

-------------

PR: https://git.openjdk.java.net/jdk/pull/7270