[hubicka]

I would be interested to know what cache aware code layout optimizations are available in LLVM. I personally know of none. GCC is bit simplistic in this sense (it does reorder functions based on profile feedback and execution time) and I plan to change that for next stage 1 (i.e. GCC 10)

[DannyBee]

Hey Jan, Long time ;)

LLVM will do the same kind of reordering.

(Both are interestingly well behind what commercial compilers do, and this is one of the very few areas where that is true. My suspicion is that it does not matter as much in practice as we want it to. Most forms of layout optimization are also very hard to perform on the C++ code you want to optimize due to inability to prove safety)

[hubicka]

Hehe, nice to see you :)

Yep, I have code layout pass in my tree for a while, but because I was never really able to measure off-noise improvements it is not in the tree, yet. I hope to make more sense of it with help of CPU counters which improved over the time.

[mhh__]

I'm not familiar enough with LLVM to really say, so I was just speculating: I vaguely remembered some kind of talk about cache optimisation and LLVM, so it's possible it was talking about the LLVM codebase rather than the passes available in LLVM.