cap frequency in make_forwarder_block PR64326
diff mbox

Message ID 1423579883-7904-1-git-send-email-tbsaunde+gcc@tbsaunde.org
State New
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Commit Message

tbsaunde+gcc@tbsaunde.org Feb. 10, 2015, 2:51 p.m. UTC
From: tbsaunde <tbsaunde@138bc75d-0d04-0410-961f-82ee72b054a4>

In the testcase the block with problematic frequency has to incoming
edges.  Each edge has probability 1.  The first edge's source bb has
frequency 873/10000, and the second has a frequency of 9409/10000.  So
at least one of those is slightly high probably from some sort of rounding
issue related to fixed point, but in any case make_forwarder_block
should not create basic blocks with frequency greater than BB_FREQ_MAX.

bootstrapped + regtested x86_64-linux-gnu, checked test only passes with patch.
pre approved by Honza on irc so committed.

Trev

Patch
diff mbox

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 72fbdd7..50fa380 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@ 
+2015-02-10  Trevor Saunders  <tsaunders@mozilla.com>
+
+	PR tree-optimization/64326
+	* cfghooks.c (make_forwarder_block): Cap frequency of created block.
+
 2015-02-10  Rainer Emrich  <rainer@emrich-ebersheim.de>
 
 	PR gcov-profile/61889
diff --git a/gcc/cfghooks.c b/gcc/cfghooks.c
index 4b57280..abeab8c 100644
--- a/gcc/cfghooks.c
+++ b/gcc/cfghooks.c
@@ -863,6 +863,9 @@  make_forwarder_block (basic_block bb, bool (*redirect_edge_p) (edge),
       if (redirect_edge_p (e))
 	{
 	  dummy->frequency += EDGE_FREQUENCY (e);
+	  if (dummy->frequency > BB_FREQ_MAX)
+	    dummy->frequency = BB_FREQ_MAX;
+
 	  dummy->count += e->count;
 	  fallthru->count += e->count;
 	  ei_next (&ei);
diff --git a/gcc/testsuite/gcc.dg/torture/pr64326.c b/gcc/testsuite/gcc.dg/torture/pr64326.c
new file mode 100644
index 0000000..88ebf35
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr64326.c
@@ -0,0 +1,30 @@ 
+/* { dg-do compile } */
+
+int a, b, c, d, e, f[5][2];
+char g;
+
+int
+fn1 ()
+{
+	  return d && c ? 0 : 1;
+}
+
+int
+fn2 ()
+{
+	  int h;
+	    for (;;)
+		        for (; e;)
+				      {
+					              int i, j;
+						              h = a ? 1 : b;
+							              if (h || fn1 () ^ g - 682)
+									                {
+												            for (i = 0; i < 5; i++)
+														                  for (j = 0; j < 2; j++)
+																	                  f[i][j] = 0;
+													                return 0;
+															          }
+								            }
+}
+