From: Filip Kastl <filip.kastl@gmail.com>
Date: Wed, 5 Jul 2023 15:36:02 +0000 (+0200)
Subject: value-prof.cc: Correct edge prob calculation.
X-Git-Tag: basepoints/gcc-15~7813
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1ee710027d8aa16145dab623815d9f9921cf9633;p=thirdparty%2Fgcc.git

value-prof.cc: Correct edge prob calculation.

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

Signed-off-by: Filip Kastl <filip.kastl@gmail.com>

gcc/ChangeLog:

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

diff --git a/gcc/value-prof.cc b/gcc/value-prof.cc
index f40e58ac4f24..5033a6f6aec3 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
     {