Re: RFC: How to handle function tracing, frame pointers and -mfentry?

[Andi Kleen <andi@firstfloor.org>]

> 1) Have kconfig detect if -mfentry is supported with the current
> compiler. If it is, then enable a "auto" config called
> CONFIG_CC_HAS_FENTRY, and allow function tracer be able to select
> FRAME_POINTER if that's not defined.
> 
> I actually got this to work, but it only works if the host compiler is
> the same as the compiler building the kernel. Which in lots of cases is
> not (my default setup does not have this).

Kconfig just needs to learn how to run the target compiler

I think that's the right direction. Right now our main
Makefiles get polluted more and more with "test compiles", each
of which makes a "null make" slower and slower. 

I just measured and a null compile (nothing changes) of a current
tree calls "gcc" 141 times.

All this stuff should be cached in the Kconfig instead.

It may break some obscure setups (that can be probably fixed without
too much effort), but the development turnaround improvement
for everyone else would be worth it.

-Andi
-- 
ak@linux.intel.com -- Speaking for myself only.