How to build an executable with profiling?

[Roman Divacky]

On Tue, Jan 18, 2011 at 04:43:13PM +0200, Kostik Belousov wrote:
> On Tue, Jan 18, 2011 at 03:32:05PM +0100, Roman Divacky wrote:
> > On Mon, Jan 17, 2011 at 10:44:11AM -0800, Steve Kargl wrote:
> > > How does one build an executable for profiling with clang?
> >  
> > LLVM (and thus clang) does not support GPROF profiling. 
> > 
> > > clang -o testf -O2 -march=native -pipe -static -pg -I/usr/local/include -I../mp testf.c -L/usr/local/lib -L../mp -lsgk -lmpfr -lgmp -L/usr/home/kargl/work/lib -lm_clang_p
> > > clang: warning: the clang compiler does not support '-pg'
> > > 
> > > I suppose it will be pointless to ask, but shouldn't clang
> > > support one of the most basic gcc compiler options if clang
> > > is to replace gcc as the base system compiler?
> > 
> > is GPROF really needed at this point? we have HWPMC, isnt
> > it sufficient?
> Hwpmc requires additional work for each new CPU model. Also,
> hwpmc is not supported even on all Intel or AMD CPUs, esp. older
> models, and e.g. VIA cores.
> 
> Not to mention !x86 architectures.

yes. I agree. HWPMC is not 100% solution.

for those interested in profiling in LLVM in detail:

        http://llvm.org/pubs/2010-04-NeustifterProfiling.html

summary: LLVM supports inserting profiling probes (but the selection
         of places where to put them is very naive) but there's no
         "GPROF writer".

I mailed the author of the thesis yesterday and it looks like his work may
get committed to upstream LLVM.

roman