Re: link-time optimization error using llvm 3.0
Re: link-time optimization error using llvm 3.0
- Subject: Re: link-time optimization error using llvm 3.0
- From: Andreas Grosam <email@hidden>
- Date: Wed, 07 Dec 2011 09:32:03 +0100
On Dec 6, 2011, at 5:36 PM, tobias ford wrote:
> Yeah... That was the equivalent answer to sweeping this issue under the carpet :)
>
> If I use llvm gcc, are the link-time optimizations to the same or somewhat similar extents as when using llvm 3.0?
LLVM GCC 4.2 supports Link-Time optimizations.
You may read in the release notes <http://developer.apple.com/library/mac/#releasenotes/DeveloperTools/RN-llvm-gcc/_index.html> for further details.
From my experience with LTO using clang/LLVM (and I don't have any for GCC 4.2), I wouldn't recommend it to enable this flag in production code *yet*, unless you tested your code *thoroughly*. It seems, there are still bugs in the linker and possibly elsewhere, too.
The typical Objective-C code wouldn't benefit much anyway (hardly noticeable difference in performance, during my tests). But sometimes, that is not always, I experienced a dramatical improvement in code which has inlined C-functions, especially C++ templates and code which includes "header only libraries": about 30% improvements for small codes in synthetic benchmarks.
Regards
Andreas _______________________________________________
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