I thought clang was slower than gcc because clang doesn't support thread local variables (in some form we need) and therefore GC performance suffered a lot on clang.
On Sat, Jul 12, 2014 at 9:27 PM, Mark Lentczner <[email protected]> wrote: > In building the OS X bindist for 7.8.3, I had to choose which of several > ways to build it. In particular, I could build it with a newere Xcode, > which uses clang, or an older Xcode which uses gcc. I decided to nofib > benchmark the variations and see before I released. Here is what I found... > > I compared two candidate builds: > > - x86_64 architecture > - targeted at OS X 10.7 and later > - one built with Xcode 5.1 on 10.9, which uses clang > - one built with Xcode 4.5 on 10.8, which uses gcc > > I installed both bindists, side-by-side on the same machine: a 10.9 > machine, with Xcode 5.1, which uses clang. The machine is a MacMini, 2.5GHz > Intel Core i5 (dual core, reports as 4 cpus). > > Summary: > > - clang build was always faster > - non-threaded was -3.2% run-time > - threaded was -7.3% run-time > - clang's improvement in GC run-time was better than -10% > - clang builds were significantly bigger > > You can find the details here: > > - analysis-Silver-10.9-gcc-vs-clang.html > > <http://www.ozonehouse.com/mark/platform/analysis-Silver-10.9-gcc-vs-clang.html> > - analysis-Silver-10.9-gcc-vs-clang-threaded.html > > <http://www.ozonehouse.com/mark/platform/analysis-Silver-10.9-gcc-vs-clang-threaded.html> > > The only concern is that the binary sizes were significantly bigger: +230% > - I haven't investigated more, but I'm wondering if nofib doesn't strip the > binaries before measuring, and perhaps clang's debugging info is much > greater? > > Next up... we are evaluating a bindist built with the HPC Mac OS X gcc > compiler (based on gcc 4.9)... and preliminary results are looking even > better! Stay tuned... > > - Mark > > > _______________________________________________ > ghc-devs mailing list > [email protected] > http://www.haskell.org/mailman/listinfo/ghc-devs > >
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