[LLVMdev] -O4 -fvisibility=hidden

[Chris Lattner]

On Jan 30, 2009, at 7:42 PM, Jack Howarth wrote:

> Tk/Python driven software appears very friendly to - 
> fvisibility=hidden.

Nice!

> Are there any particular optimization options that one should use  
> besides
> -O4 -fvisibility=hidden to enable all of the possible llvm Link Time  
> Optimizations?

Nope, that should be enough.  "-O4" is effectively -O3 + -flto.  You  
might also try -O2 -flto explicitly if you care about code size.

> Also, I assume that one only needs to compile the object files with
> -O4 -fvisibility=hidden and that the actual linkage doesn't need those
> flags to enable full LTO, correct?

Right.

Is there a significant code size or perf difference with lto?

-Chris