-fprofile-arcs changes the structure of basic blocks

[Zdenek Dvorak]

Hello,

> 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.
> 
> I use -fprofile-arcs. 

this does not make much sense to me.  If you cannot run the compiled
program, adding instrumentation with -fprofile-arcs is useless.  In this
case, you may just use the guessed frequencies (that you get by default
without any flags).

Zdenek

> And I can see the frequency value when I debug
> cc1. But I happen to realize that when I add -fprofile-arcs, it change
> the the whole structure of basic block. I compared the vcg output
> files with and without the -fprofile-arcs. I found they're totally
> different.
> 
> 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.
> 
> Where do I go wrong here? Which option is the suitable in this case?
> The gcc version is 3.3.3. Thanks.
> 
> 
> Regards,
> Timothy