Re: -fprofile-arcs changes the structure of basic blocks

[Liu Haibin <liu dot haibin at gmail dot com>]

Then I think I shouldn't use -fprofile-arcs. The reason why I used
-fprofile-arcs is when I debugged a program without any flags, I saw
the frequency was zero. When I added this flag, I saw frequency with
values.

I checked the frequency after life_analysis and before
combine_instructions. I used

FOR_EACH_BB(bb) {
             // some code
}

and checked the bb->frequency.

So now the question is how I can see the frequency without any flags.
The following was the small program I used to check the frequency.

int foo(int i)
{
	if (i < 2)
		return 2;
	else
		return 0;
}
int main()
{
	int i;

	i = 0;
	if (i < 100)
		i = 3;
	else
		i = foo(i);

	return 0;
}




On 6/24/05, Daniel Berlin <dberlin@dberlin.org> wrote:
> On Thu, 23 Jun 2005, Liu Haibin wrote:
> 
> > Hi,
> >
> > I want to use profiling information. I know there're two relevent
> > fields in each basic block, count and frequency. I want to use
> > frequency because the compiled program is for another architecture so
> > it cannot run on the host.
> 
> Besides the fact that, as Zdenek hsa pointed out, this is not a useful
> situation for -fprofile-arcs, ...
> >
> > My question is why it is so? I want to know the profiling info, but if
> > profiling info I get is for another different structure of basic
> > block, it's useless to me.
> >
> 
> This is because it's inserting profiling code.
> 
> This isn't magic, it's inserting code to do the profiling, which
> necessarily changes the basic blocks.
> The profiling info you get is for the original set of basic blocks.
> 
>