building libjvm with -Os for space optimization - was : RE: RFR: 8234525: enable link-time section-gc for linux s390x to remove unused code

[August Nagro]

Its been a while since I tried, but if I remember correctly I had to delete
the code that tested the compiler name / version in one of the sh files. I
set the compiler to icc via the environment variables.

The build ran for a while but then stopped with an error message. I
remember it not being very helpful.

I would think you'll have better luck on Linux + gcc than me on Mac,
although icc claims compatible with llvm too.
Let me know if you succeed!

On Thu, Jan 30, 2020, 9:37 AM Magnus Ihse Bursie <
magnus.ihse.bursie at oracle.com> wrote:

>
>
> On 2019-12-18 00:05, August Nagro wrote:
>
> I published some benchmarks of OpenJDK on Mac with Ofast and O3 [1]. Some microbenchmarks like Netty’s HttpObjectEncoder experienced >100% speedup with O3, and the more real-world Dacapo suite was ~15% improvement over O2 (which is exactly the same as Os). I did include a few other flags, however the speedup was primarily due to optimization level.
>
> Building with Os is the old wisdom. It used to be the case that many programs would be faster with the smaller binary size, but this is almost never the case nowadays.
>
> - August
>
> [1]: http://august.nagro.us/optimized-openjdk.html
>
> Nice. :)
>
> I noticed this on your blog post:
>
> I also tried building with Intel’s Compiler
> <https://software.intel.com/en-us/c-compilers>, and patched the configure
> scripts to allow it. However, the build failed cryptically. I’d also be
> interested to see Linux results.
>
>
> How did you patch configure, and what errors did you run into? In general,
> it's not a small task to get OpenJDK to compile with a new compiler, but
> Intel claims a high level of compatibility with gcc [1] and that increases
> chances that it should be possible to achieve with not too much effort. I'm
> slightly tempted to looking into it. :)
>
> /Magnus
>
> [1]
> https://software.intel.com/en-us/cpp-compiler-developer-guide-and-reference-gcc-compatibility-and-interoperability
>
>
>
>