[8u] RFR: 8210352: [hotspot] --with-extra-cxx-flags should not lower optimization

[Erik Joelsson]

Hello,

I understand your problem, but I'm really not sure I like this solution. 
What I mostly question is your desire for adding optimization to the 
libraries nobody has bothered adding optimizations on by default since 
forever. If this is important to you, then provide a patch adding opt 
flags to the specific libraries. In general, the OpenJDK build is very 
conscious about what optimization levels are used wherever it matters, 
so tinkering with them is likely not a good idea.

That said, I think a better fix would be to reorder the arguments so 
that the OPT flags are added after any extra flags variable.

/Erik


On 2018-09-04 08:36, Severin Gehwolf wrote:
> Hi,
>
> Could I please get reviews of this JDK 8-only change?
>
> The issue at hand is that the JDK 8 build seems to be inconsistent with
> later JDK builds (9+). When somebody passes
> --with-extra-c{,xx}-flags="-O2" to the OpenJDK build on JDK 9+ the JVM
> will get compiled with -O3 for a release type build. Not so on JDK 8.
> It gets compiled with -O2. The reason we are passing extra C flags via
> configure is to: a) get distro-wide optimization done b) allow for
> hardened builds. Without the --with-extra-c{,xx}-flags="-O2" flag,
> libjsig, libsaproc will get compiled with no optimization. That's what
> I'd like to fix. The proposed patch allows one to force -O2 for the JVM
> via OPT_EXTRAS make variable if so desired. Omitting OPT_EXTRAS=-O2
> allows one to get hotspot libraries optimized with -O2 and better.
> Thoughts?
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8210352
> webrev: http://cr.openjdk.java.net/~sgehwolf/webrevs/JDK-8210352/webrev.01/
>
> Thanks,
> Severin
>