I'm aware of the limitations on SPEC editing. However, "If someone managed to make an optimization that could suddenly make GCC 2x faster without humans editi

I'm aware of the limitations on SPEC editing. However, "If someone managed to make an optimization that could suddenly make GCC 2x faster without humans editing GCC's source, that would be a major CS breakthrough :) " No, it really wouldn't. For example, if you optimize the line-ending and tokenization finding in GCC's parser to use SIMD, you would become significantly faster. Not 2x, but significantly. These are entirely doable by compilers. " But you don't ever get to re-write the benchmark itself, you can't replace a 2^N path with an N^3 path or anything like that." Except, you can, by hoisting calls out of loops, etc. There are also dynamic memoization optimziations that can be applied, etc. "If someone managed to make an optimization " This is a common fallacy that it's ever really one optimization. It's usually combinations of optimizations, each buying you N%. I will state outright, having worked on pretty much all of the slow parts of gcc (according to spec profiles), and having a team of 80+ people working on compilers, 2x on gcc through compiler optimization is more than within the realm of possibility.