[PATCH] value-prof.cc: Correct edge prob calculation.

[Filip Kastl via Gcc-patches]

The mod-subtract optimization with ncounts==1 produced incorrect edge
probabilities due to incorrect conditional probability calculation. This
patch fixes the calculation.

gcc/ChangeLog:

        * value-prof.cc (gimple_mod_subtract_transform): Correct edge
          prob calculation.

Signed-off-by: Filip Kastl <filip.ka...@gmail.com>
---
 gcc/value-prof.cc | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/gcc/value-prof.cc b/gcc/value-prof.cc
index f40e58ac4f2..580d6dd648d 100644
--- a/gcc/value-prof.cc
+++ b/gcc/value-prof.cc
@@ -1186,7 +1186,11 @@ gimple_mod_subtract_transform (gimple_stmt_iterator *si)
   if (all > 0)
     {
       prob1 = profile_probability::probability_in_gcov_type (count1, all);
-      prob2 = profile_probability::probability_in_gcov_type (count2, all);
+      if (all == count1)
+       prob2 = profile_probability::even ();
+      else
+       prob2 = profile_probability::probability_in_gcov_type (count2, all -
+                                                              count1);
     }
   else
     {
-- 
2.40.1