[RFC] Replace Java with Go in default languages

[Jeff Law]

On 11/09/13 04:12, Eric Botcazou wrote:
>> Right now Go does not build on a range of targets, notably including
>> Windows, MacOS, AIX, and most embedded systems.  We would have to
>> disable it by default on targets that are not supported, which is
>> straightforward (we already have rules to disable java on targets it
>> does not support).  But to the extent that there are options like
>> -fnon-call-exceptions that are tested primarily by Java and Go, we
>> would get less coverage of those options, since we would not test them
>> on systems that Java supports but Go does not.
>
> Let me make the case for Ada here: it's a general purpose, highly portable
> language, which is regularly built and tested on a significant range of
> platforms (I personally test it on x86/Linux, x86-64/Linux, PowerPC/Linux,
> IA-64/Linux, SPARC/Solaris and SPARC64/Solaris).  It exercices some features
> of the compiler that aren't exercised by other languages and stretches some
> common features much more than the other languages.  It turns out that it also
> enables -fnon-call-exceptions by default.  It seamlessly works with LTO.
>
> While the fact that a big part of the front-end is written in Ada could be
> seen as an annoyance (although GNAT has been largely available for about a
> decade on many systems), it can also be seen a boon; for example, a LTO
> bootstrap with Ada enabled really exercises cross-language optimizations.
>
> Bootstrapping with Ada is marginally slower than with Go (a few percents) and
> the testsuite is small (4-way parallelizable, testing time of 6 minutes on a
> fast machine).
 From what I can see, bootstrapping with Ada is slower than bootstapping 
with Java, by around 15%.  Again this is on one of my slower boxes, but 
the results clearly show building Ada & its runtime takes a considerable 
amount of time:

default languages:    67 minutes
default - java:       51 minutes
default - java + go:  56 minutes
default - java + ada: 77 minutes

Some of this might be building Ada and its runtime during all three 
stages.  Contrast to Java which builds the front-end during 
stage2/stage3 and the runtime just in stage3.

Hard to justify switching from Java to Ada given those results if one of 
the key goals is to reduce waiting time.

jeff