GCC-4.5.0 and LLVM-2.7 were released recently. To understand where we stand after releasing GCC-4.5.0 I benchmarked it on SPEC2000 for x86/x86-64 and posted the comparison of it with the previous GCC releases and LLVM-2.7.
Even benchmarking SPEC2000 takes a lot of time on the fastest machine I have. So I don't plan to use SPEC2006 for this in near future. You can find the comparison on http://vmakarov.fedorapeople.org/spec/ (please just click links at the bottom of the left frame starting with link "GCC release comparison"). If you need exact numbers, please use the tables (the links to them are also given) which were used to generate the corresponding bar graphs. In general GCC-4.5.0 became faster (upto 10%) in -O2 mode. This is first considerable compilation speed improvement since GCC-4.2. GCC-4.5.0 generates a better (1-2% in average upto 4% for x86-64 SPECFP2000 in -O2 mode) code too in comparison with the previous release. That is not including LTO and Graphite which can gives even more (especially LTO) in many cases. GCC-4.5.0 has new big optimizations LTO and Graphite (more accurately graphite was introduced in the previous release). Therefore I ran additional benchmarks to test them. LTO is a promising technology especially for integer benchmarks for which it results in smaller and faster code. But it might result in degradations too on SPECFP2000 mainly because of big degradations on a few benchmarks like wupwise or facerec. Another annoying thing about LTO, it considerably slows down the compiler. Currently Graphite gives small improvements on x86 (one exception is 2% for peak x86 SPECFP2000) and mostly degradation on x86_64 (with maximum one more than 10% for SPECFP2000 because of big degradations on mgrid and swim). So further work is needed on the project because it seems not mature yet. As for LLVM, LLVM became slower (e.g. in comparison with llvm-2.5 on 15%-50% for x86-64). So the gap between compilation speed of GCC and LLVM decreased and sometimes achieves 4% on x86_64 and 8% on x86 (both for SPECInt2000 in -O2 mode). May be I am wrong but I don't think CLANG will improve this situation significantly (in -O2 and -O3 mode) because optimizations still take most of time of any serious optimizing compiler. LLVM did a progress in code performance especially for floating point benchmarks. But the gap between LLVM-2.7 and GCC-4.5 in peak performance (not including GCC LTO and Graphite) still 6-7% on SPECInt200 and 13-17% on SPECFP2000. In general, IMHO GCC-4.5.0 is a good and promising release.
