Firefox 64 built with GCC and Clang
I realize it's not the focus of his test, but as someone who thinks often about how to take advantage of advanced vectorization techniques on modern processors, I was surprised by statements like this:Moreover GCC -O2 defaults are (in my opinion unfortunately) still not enabling vectorization and unrolling which may have noticeable effects on benchmarks.This led to enabling AVX and since the global constructor now gets some code auto-vectorized the binary crashed on invalid instruction during the build (my testing machine has no AVX).No AVX? He wants to better take advantage of vectorization, but he's doing the testing on a processor that is 3 generations behind in vectorization support.   AVX (128-bit) come out in 2011, and has been followed by AVX2 (256-bit) and (still limited release) AVX-512.Clock speeds have been fairly flat, and most of the improvements to recent processors have been microarchitectural.  A lot of the optimization done by compilers ends up being architecture specific.  Seeing which brand-new compiler best targets old hardware seems like it might produce misleading results.I realize that not everyone has (or can have) the most recent hardware, but this seems like a case where it would be strongly in AMD and Intel's interest to make sure that people like Jan have better access to the improvements made in the last few years.