patch for estimate_probability instability

[Jan Hubicka]

> Jan Hubicka <jh@suse.cz> writes:
> 
> > Hi,
> > I've installed attached patch to cfg-brach to avoid estimate-branches
> > instability and bootstrap misscomparisons.
> > 
> > I am not quite sure if such a sollution can be acceptable for Mainline.
> 
> I think this is just papering over some other problem.  Floating-point
> is not a random number generator, so given the same input it should
> produce the same output.  What is being compiled differently to cause
> the comparison failure?
i386 fp is ranom number generator. If you store value to memory it
gets truncated from 80bits. When optimizing value is not stored, when
not optimizing it is stored causing different roudoff error in two runs.

Honza