On Mon, Mar 03, 2014 at 10:20:10AM +0800, lin zuojian wrote: > I saw > > http://www.phoronix.com/scan.php?page=article&item=llvm34_gcc49_compilers&num=1 > And LLVM/clang beaten gcc in serval tests.But I ran that > tests,e.g.SciMark,it didn't appear to be like this on my i7 machine.Was > that > article written by Apple?
See my comment there and various others, the phoronix "benchmarks" are usually microbenchmarks where the results vary a lot from one run to another one, I've very rarely have been actually able to reproduce anything close to the numbers Michael posts, and even when e.g. in this January I've improved predcom on one of the microbenchmarks a lot in GCC, no changes have been visible in Michael's numbers afterwards. I find his articles very LLVM/clang biased and numbers untrustworthy. Of course it makes sense to us to look even at those microbenchmarks from time to time and try to improve things if possible, often it is primarily about badly chosen compiler options on the Phoronix side (say benchmarks needing -ffast-math for vectorization and it not being supplied, so it is never vectorized by any compiler). SPEC is of course far more trustworthy benchmark. Jakub