Fix profile_count::apply_probability

[Jan Hubicka <hubicka@ucw.cz>]

Hi,
profile_count::apply_probability misses check for uninitialized
probability which leads to completely random results on applying
uninitialized probability to initialized scale.  This can make
difference when i.e. inlining -fno-guess-branch-probability function to
-fguess-branch-probability one.

Boootstrapped/regtested x86_64-linux, commited.
gcc/ChangeLog:

	* profile-count.h (profile_count::apply_probability): Fix
	handling of uninitialized probabilities, optimize scaling
	by probability 1.

diff --git a/gcc/profile-count.h b/gcc/profile-count.h
index bf1136782a3..e860c5db540 100644
--- a/gcc/profile-count.h
+++ b/gcc/profile-count.h
@@ -1129,11 +1132,11 @@ public:
   /* Scale counter according to PROB.  */
   profile_count apply_probability (profile_probability prob) const
     {
-      if (*this == zero ())
+      if (*this == zero () || prob == profile_probability::always ())
 	return *this;
       if (prob == profile_probability::never ())
 	return zero ();
-      if (!initialized_p ())
+      if (!initialized_p () || !prob.initialized_p ())
 	return uninitialized ();
       profile_count ret;
       uint64_t tmp;