Support build in gcc 9

[joeyleeeeeee97]

Some features or performance optimizations in JVM may need a higher version of GCC.

Maybe we could add gcc9 build config in a separate docker image.

[M-Davies]

Related #451.

We don't have gcc 9 installed on the machines so this is likely an openjdk-infrastructure first and then openjdk-build issue to get it configured. @karianna Can you move this over to inf?

[sxa]

@M-Davies I wold suggest that unless there's a decision on this (which would require openjdk-build adjustments) this is the correct home for it, with a separate issue if we choose to install it)

@joeyleeeeeee97 We build most of them on gcc 7.5 now. Is there a specific thing that you are aware of which is advantageous when build with gcc 9 - I presume there's something you're aware of since you haven't picked gcc 10 :-)

[aahlenst]

I can do issue transfers the whole day 😂

[joeyleeeeeee97]

@M-Davies I wold suggest that unless there's a decision on this (which would require openjdk-build adjustments) this is the correct home for it, with a separate issue if we choose to install it)

@joeyleeeeeee97 We build most of them on gcc 7.5 now. Is there a specific thing that you are aware of which is advantageous when build with gcc 9 - I presume there's something you're aware of since you haven't picked gcc 10 :-)

Yes. We find higher version of gcc brings significant benefits on some microbenchmarks. The reason we chose gcc9 is mostly that gcc 10 haven't be widely used in Alibaba. :)

[sxa]

Yes. We find higher version of gcc brings significant benefits on some microbenchmarks. The reason we chose gcc9 is mostly that gcc 10 haven't be widely used in Alibaba. :)

Thanks for the info. In that case I think we should certainly look at setting up Linux/x64 with gcc-9 for the Dragonwell builds only initially :-)

[sxa]

@joeyleeeeeee97 Are the microbenchmarks that show up the improvements available in the open?

[joeyleeeeeee97]

@joeyleeeeeee97 Are the microbenchmarks that show up the improvements available in the open?

Spec tests(specjbb2015) performance is better, for a specific number and cases we could do this once we got a gcc9 dragonwell to compare with its gcc7 version. :)

[sxa]

FYI We are in the process of installing GCC10.3 for JDK17u onto the build systems, so if we choose to use that version instead of GCC9 we can switch up (and stop installing 9)