RFR: JDK-8246751 Mac OS build settings should use -O3

[Erik Joelsson]

Looks good.

/Erik

On 2020-06-08 08:55, Magnus Ihse Bursie wrote:
> From Jim's bug report:
>
> "Mac OS X should use -O3 optimization level to be consistent with 
> other platforms and benefit Mac OS X java with the same performance 
> levels as other platforms.
>
> Mac OS X has used -Os level optimization since management of the 
> platform JDK was handed over from Apple. This level of optimization 
> was Apple's policy, not OpenJDK's. The policy was established in a 
> time when memory was tight (I was there at the time.) Since then other 
> platforms have moved on, making the decision to target speed over disk 
> space. Specifically, using -O3 level optimization.
>
> I've personally seen 20-30% improvement in performance in C/C++ 
> applications using -O3 over -Os. But, of course, the performance team 
> should verify the affect on the JDK.
>
> A 11% real time improvement can be seen with a rough HelloWord 
> compile/run."
>
> I discussed this with Claes, our performance guru, and he agreed that 
> it is low risk enough that we can push this for JDK 15.
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8246751
> WebRev: 
> http://cr.openjdk.java.net/~ihse/JDK-8246751-macos-optimize-O3/webrev.01
>
> /Magnus