[aarch64-port-dev ] Possible aarch64 bug with RoundFPResults

[Andrew Haley]

On 04/05/2018 07:54 PM, White, Derek wrote:

> I'm looking over "RFR: 8145665: Make UseSSE an x86 specific option and cleanup its usage in shared code", and saw an odd thing:
> 
> AARCH64 defines RoundFPResults=true, like x86 does, not like PPC, arm, s390, etc.
> 
> This flag controls (along with UseSSE) cases where CPUs need to explicitly round to 64-bit FP. Which we should never have to do on AARCH64?
> 
> Is this a real issue or am I imagining it?
> 
> This is becoming more urgent because  JDK-8145665 is removing UseSSE from non-x86 code, which would result in more use of rounding.

It's only used by C1, and even there it has a small effect on efficiency.  We'd
be slightly faster without it set, but I don't think it would affect any results.

-- 
Andrew Haley
Java Platform Lead Engineer
Red Hat UK Ltd. <https://www.redhat.com>
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