OSNews: http://www.osnews.com/story/20517/LLVM_2_4_Released Exploring the Future of Computing en-us Copyright 2001-2009, David Adams adam+nospam@osnews.com Mon, 09 Nov 2009 10:11:15 GMT http://www.osnews.com/images/osnews.gif OSNews.com http://www.osnews.com Is it really useable? http://osnews.com/thread?336976 http://osnews.com/thread?336976 I've tried the llvm-gcc bundled with XCode 3.1.1. So far there doesn't seem to be much practical use for it. The compiler bombs when attempting to compile Qt4.4.3.

Anybody had any better luck? There has been claims that llvm-gcc produces code faster than vanilla gcc. Tue, 11 Nov 2008 16:59:00 GMT donotreply@osnews.com (adkilla) Comments RE: Is it really useable? http://osnews.com/thread?336981 http://osnews.com/thread?336981 The llvm-gcc component is the most recent one and indeed it is known that it is good for medium sized project, while QT is quite a big one.

The great advantage of llvm is for creation and optimization of specialized languages, or in the various conditions in which glue code between components needs to be optimized. Tue, 11 Nov 2008 17:42:00 GMT donotreply@osnews.com (sankazim) Comments RE: Is it really useable? http://osnews.com/thread?337019 http://osnews.com/thread?337019 adkilla wrote:
-"Anybody had any better luck? There has been claims that llvm-gcc produces code faster than vanilla gcc."

AFAIK llvm-gcc just uses gcc as a front end, the code optimization is all done by llvm. And yes, I've seen claims of better optimized code generation but I've yet to confirm it for myself (actually if anyone has some benchmarks or some such it would be very interesting). IIRC one of the authors of llvm claimed an overall 5%-10% speed increase in the generated code when compiling using llvm (which I personally think sounds almost too good) as compared to gcc. Of course both compilers are in heavy development and any such statements can be obsolete from day to day, but given that llvm is a relatively new project it's likely alot easier to implement new modern optimization techniques into it's codebase than into the much older and larger gcc toolchain which also has to make sure it doesn't break since basically the entire oss world depends on it.

I can't vouch for it's overall useability as I've yet to try it out, but given that it consists of many components I suppose some are more mature than others. For instance I believe the jit compiler is being used in OSX's opengl stack. Tue, 11 Nov 2008 23:20:00 GMT donotreply@osnews.com (Valhalla) Comments RE: Is it really useable? http://osnews.com/thread?337021 http://osnews.com/thread?337021
I've tried the llvm-gcc bundled with XCode 3.1.1. So far there doesn't seem to be much practical use for it. The compiler bombs when attempting to compile Qt4.4.3.

Anybody had any better luck? There has been claims that llvm-gcc produces code faster than vanilla gcc.


What's the minimum gcc compiler allowed to compile Qt4.4.3? Wed, 12 Nov 2008 00:17:00 GMT donotreply@osnews.com (tyrione) Comments CLang C++ Status http://osnews.com/thread?337032 http://osnews.com/thread?337032 This probably answers your question about the current viability of LLVM and it's CLang project with Qt's C++ Toolkit.

http://clang.llvm.org/cxx_status.html Wed, 12 Nov 2008 02:49:00 GMT donotreply@osnews.com (tyrione) Comments RE[2]: Is it really useable? http://osnews.com/thread?337099 http://osnews.com/thread?337099 The minimums are available here:
http://trolltech.com/developer/supported-platforms

Looks like gcc 3.4 and above should work. Wed, 12 Nov 2008 18:14:00 GMT donotreply@osnews.com (adkilla) Comments RE: CLang C++ Status http://osnews.com/thread?337100 http://osnews.com/thread?337100 clang is not llvm-gcc. Look at this comparison at the llvm site:
http://clang.llvm.org/performance.html

How could there be performance differences between clang and llvm-gcc if they are the same compiler? Wed, 12 Nov 2008 18:16:00 GMT donotreply@osnews.com (adkilla) Comments RE[2]: Is it really useable? http://osnews.com/thread?337101 http://osnews.com/thread?337101 From the LLVM 2.4 release notes:

Known problems with the llvm-gcc C++ front-end
The C++ front-end is considered to be fully tested and works for a number of non-trivial programs, including LLVM itself, Qt, Mozilla, etc.

Exception handling works well on the X86 and PowerPC targets. Currently only Linux and Darwin targets are supported (both 32 and 64 bit).


By the way llvm-gcc is a supported compiler in Qt4 mkspecs.Edited 2008-11-12 18:21 UTC Wed, 12 Nov 2008 18:20:00 GMT donotreply@osnews.com (adkilla) Comments RE[2]: CLang C++ Status http://osnews.com/thread?337115 http://osnews.com/thread?337115 Those performance figures are *compile* time not runtime. Wed, 12 Nov 2008 19:24:00 GMT donotreply@osnews.com (kusami) Comments RE[3]: CLang C++ Status http://osnews.com/thread?337181 http://osnews.com/thread?337181 Yes, that is what I was referring to. If the compilers are the same why are the comparisons between them show significant difference between them? Thu, 13 Nov 2008 06:30:00 GMT donotreply@osnews.com (adkilla) Comments