PR tree-optimization/69489

	* tree-if-conv.c (phi_convertible_by_degenerating_args): New.
	(if_convertible_phi_p): Call phi_convertible_by_degenerating_args.
	Revise dump message.
	(if_convertible_bb_p): Remove check on edge count of basic block's
	predecessors.

	gcc/testsuite/ChangeLog
	PR tree-optimization/69489
	* gcc.dg/tree-ssa/ifc-pr69489-2.c: New test.



git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@235292 138bc75d-0d04-0410-961f-82ee72b054a4

4 files changed, 93 insertions, 6 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 1f3d66b24de..55d9708336b 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,14 @@
 2016-04-20  Bin Cheng  <bin.cheng@arm.com>
 
+	PR tree-optimization/69489
+	* tree-if-conv.c (phi_convertible_by_degenerating_args): New.
+	(if_convertible_phi_p): Call phi_convertible_by_degenerating_args.
+	Revise dump message.
+	(if_convertible_bb_p): Remove check on edge count of basic block's
+	predecessors.
+
+2016-04-20  Bin Cheng  <bin.cheng@arm.com>
+
 	PR tree-optimization/56625
 	PR tree-optimization/69489
 	* tree-data-ref.h (DR_INNERMOST): New macro.
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index bf59b9b1802..57f5bb4a8e3 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2016-04-20  Bin Cheng  <bin.cheng@arm.com>
+
+	PR tree-optimization/69489
+	* gcc.dg/tree-ssa/ifc-pr69489-2.c: New test.
+
 2016-04-20  Ilya Verbin  <ilya.verbin@intel.com>
 
 	PR c++/69363
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ifc-pr69489-2.c b/gcc/testsuite/gcc.dg/tree-ssa/ifc-pr69489-2.c
new file mode 100644
index 00000000000..6661f1a6c1b
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/ifc-pr69489-2.c
@@ -0,0 +1,17 @@
+/* { dg-do compile } */
+/* { dg-options "-S -O2 -ftree-vectorize -fdump-tree-ifcvt-stats" { target *-*-* } } */
+
+double
+foo (const char *u, const char *v, long n)
+{
+  long i, n1 = 0, n2 = 0;
+
+  for (i = 0; i < n; i++)
+    {
+      n2 += (u[i] && !v[i]);
+      n1 += (!u[i] && v[i]);
+    }
+  return (2.0 * n2 * n1);
+}
+
+/* { dg-final { scan-tree-dump-times "Applying if-conversion" 1 "ifcvt" } } */
diff --git a/gcc/tree-if-conv.c b/gcc/tree-if-conv.c
index 691811322f7..04a1d3e536d 100644
--- a/gcc/tree-if-conv.c
+++ b/gcc/tree-if-conv.c
@@ -575,6 +575,65 @@ bb_with_exit_edge_p (struct loop *loop, basic_block bb)
   return false;
 }
 
+/* Given PHI which has more than two arguments, this function checks if
+   it's if-convertible by degenerating its arguments.  Specifically, if
+   below two conditions are satisfied:
+
+     1) Number of PHI arguments with different values equals to 2 and one
+	argument has the only occurrence.
+     2) The edge corresponding to the unique argument isn't critical edge.
+
+   Such PHI can be handled as PHIs have only two arguments.  For example,
+   below PHI:
+
+     res = PHI <A_1(e1), A_1(e2), A_2(e3)>;
+
+   can be transformed into:
+
+     res = (predicate of e3) ? A_2 : A_1;
+
+   Return TRUE if it is the case, FALSE otherwise.  */
+
+static bool
+phi_convertible_by_degenerating_args (gphi *phi)
+{
+  edge e;
+  tree arg, t1 = NULL, t2 = NULL;
+  unsigned int i, i1 = 0, i2 = 0, n1 = 0, n2 = 0;
+  unsigned int num_args = gimple_phi_num_args (phi);
+
+  gcc_assert (num_args > 2);
+
+  for (i = 0; i < num_args; i++)
+    {
+      arg = gimple_phi_arg_def (phi, i);
+      if (t1 == NULL || operand_equal_p (t1, arg, 0))
+	{
+	  n1++;
+	  i1 = i;
+	  t1 = arg;
+	}
+      else if (t2 == NULL || operand_equal_p (t2, arg, 0))
+	{
+	  n2++;
+	  i2 = i;
+	  t2 = arg;
+	}
+      else
+	return false;
+    }
+
+  if (n1 != 1 && n2 != 1)
+    return false;
+
+  /* Check if the edge corresponding to the unique arg is critical.  */
+  e = gimple_phi_arg_edge (phi, (n1 == 1) ? i1 : i2);
+  if (EDGE_COUNT (e->src->succs) > 1)
+    return false;
+
+  return true;
+}
+
 /* Return true when PHI is if-convertible.  PHI is part of loop LOOP
    and it belongs to basic block BB.
 
@@ -601,10 +660,11 @@ if_convertible_phi_p (struct loop *loop, basic_block bb, gphi *phi,
   if (bb != loop->header)
     {
       if (gimple_phi_num_args (phi) != 2
-	  && !aggressive_if_conv)
+	  && !aggressive_if_conv
+	  && !phi_convertible_by_degenerating_args (phi))
 	{
 	  if (dump_file && (dump_flags & TDF_DETAILS))
-	    fprintf (dump_file, "More than two phi node args.\n");
+	    fprintf (dump_file, "Phi can't be predicated by single cond.\n");
 	  return false;
         }
     }
@@ -1003,10 +1063,6 @@ if_convertible_bb_p (struct loop *loop, basic_block bb, basic_block exit_bb)
   if (EDGE_COUNT (bb->succs) > 2)
     return false;
 
-  if (EDGE_COUNT (bb->preds) > 2
-      && !aggressive_if_conv)
-    return false;
-
   if (exit_bb)
     {
       if (bb != loop->latch)