Re: PATCH: Speed up libgcj build

[Alexandre Oliva <aoliva at redhat dot com>]

On Oct 13, 2000, Jeff Sturm <jeff.sturm@appnet.com> wrote:

> Bryce McKinlay wrote:
>> This patch speeds up the .java->object file stage of the libgcj build
>> quite a lot. It appears that passing the -I flag to gcj forced it to
>> only parse .java source files and not use the already-built .class files
>> for its dependencies (which is much faster). With this, the time to
>> build java/lang/String.java, for example, goes from about 1.5 seconds to
>> 90ms for me.

> I think Alex said the -I flag was for inlining methods across
> classes.

Not only that.  I'm pretty sure there was something that broke without
it, but I'd have to build from scratch to remember what it was :-(

>> 1. Running "sh ./libtool --mode=compile" for every single .java file is
>> now actually far slower than running the compiler itself. I really wish
>> we could avoid it.

> You should see libtool run on a show shell (e.g. bash under Cygwin).

> I really, really wish libtool ran in perl, or something with a
> little speed...

There are plans on moving to C (with a shell-script as a fallback,
when no CC_FOR_BUILD is available).  Bruce Korb is the one to blame :-)
Stay tuned in libtool@gnu.org :-)

>> 2. Can someone remind me why the .java->.class stage was changed to run
>> gcj separately for every file?

To avoid limits on command-line size.

>> This is now the slowest part of the compile by far.

Wasn't it already?

>> -GCJCOMPILE = $(LIBTOOL) --mode=compile $(GCJ) -fassume-compiled -fclasspath=$(here) -L$(here) $(JC1FLAGS) -c
>> +GCJCOMPILE = $(LIBTOOL) --tag=GCJ --mode=compile $(GCJ) -fassume-compiled -fclasspath=$(here) -L$(here) $(JC1FLAGS) -c

> What is --tag=GCJ for?

It tells the multi-language libtool that the configuration for GCJ is
to be used.  Without it, libtool uses the first non-libtool arguments
in the command line (namely, $(GCJ)) to decide what configuration to
use.

-- 
Alexandre Oliva   Enjoy Guarana', see http://www.ic.unicamp.br/~oliva/
Red Hat GCC Developer                  aoliva@{cygnus.com, redhat.com}
CS PhD student at IC-Unicamp        oliva@{lsd.ic.unicamp.br, gnu.org}
Free Software Evangelist    *Please* write to mailing lists, not to me