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

[Daniel Berlin <dberlin at dberlin dot org>]

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.