Re: building llvm optimizations for libobjc2

[David Chisnall]

On 8 Dec 2011, at 14:48, Sebastian Reitenbach wrote:

> So, now I have a lib/libGNUObjCRuntime.so file installed, but wonder a bit, 
> how to make use of it ;)

The closest thing to documentation for it currently is this blog post:

http://etoileos.com/news/archive/2011/05/14/1829/

It shouldn't need any documentation.  Eventually it will be used by front ends 
automagically if it's installed.

> The README states:
> Running GNU make will then create GNUObjCRuntime.so.  This library can be
> passed to opt to run optimisations on bitcode generated with clang or
> LanguageKit.

LanguageKit will use it automatically if it's present.  Clang can be told to 
use it with -Xclang -load -Xclang /path/to/libGNURuntime.so

GNU people can probably invoke it from gold for link-time optimisation as well, 
but I've never tried.

> but unfortunately, this doesn't tells me much :(
> 
> man opt tells me, its the llvm optimizer, 
> reading further, I should do 
> opt -load=libGNUObjCRuntime.so -gnu-nonfragile-ivar -gnu-objc-type-feedback 
> <inputfile>

You can do that too, although if it's built against LLVM 3 or later it will 
automatically add the optimisations in sensible points at the default places 
for 

> but what is the inputfile, would it be libgnustep-base.so.X.X ??
> Shall I need to do this for libraries, binaries, or both?
> Can gnustep-make do this for me "automagically" when I give an environment 
> variable?

Well, you can set OBJCFLAGS="-Xclang -load -Xclang /path/to/libGNURuntime.so" 
and it should Just Work™.  It's nowhere near as well tested as the rest of the 
runtime or compiler though, so I'm a bit hesitant about enabling it by default. 
 I've compiled all of -base with it and run the tests though, so more testing 
is definitely appreciated (as are bug reports with - ideally, reduced - test 
cases).

> Or, where do I find the RTFM on that topic? 

Currently in my brain.  In the LLVM 3.1 timeframe I plan on improving the UI 
for this, and once it's a bit less ugly I'll document it properly.

David

-- Sent from my Difference Engine