Intel publish a very thick optimization manual, which is a good help. Compilers aren't great at using the real parameters of the chip (i.e. LLVM knows how wide

Intel publish a very thick optimization manual, which is a good help. Compilers aren't great at using the real parameters of the chip (i.e. LLVM knows how wide the reader buffer is but I'm not sure if it actually can use the information), but knowing latencies for ISel and things like that is very helpful. To get those details you do need to rely on people like (the god amongst men) agner fog.