re PR tree-optimization/81627 (ICE on valid code at -O3: in…

re PR tree-optimization/81627 (ICE on valid code at -O3: in check_loop_closed_ssa_use, at tree-ssa-loop-manip.c:707)

	PR tree-optimization/81627
	* tree-predcom.c (prepare_finalizers): Always rewrite into loop
	closed ssa form for store-store chain.

	gcc/testsuite
	* gcc.dg/tree-ssa/pr81627.c: New.

From-SVN: r250764

gcc/ChangeLog

 2017-08-01  Bin Cheng  <bin.cheng@arm.com>
 
+	PR tree-optimization/81627
+	* tree-predcom.c (prepare_finalizers): Always rewrite into loop
+	closed ssa form for store-store chain.
+
+2017-08-01  Bin Cheng  <bin.cheng@arm.com>
+
 	PR tree-optimization/81620
 	* tree-predcom.c (add_ref_to_chain): Don't set has_max_use_after
 	for store-store chain.

gcc/testsuite/ChangeLog

 2017-08-01  Bin Cheng  <bin.cheng@arm.com>
 
+	PR tree-optimization/81627
+	* gcc.dg/tree-ssa/pr81627.c: New.
+
+2017-08-01  Bin Cheng  <bin.cheng@arm.com>
+
 	PR tree-optimization/81620
 	* gcc.dg/tree-ssa/pr81620-1.c: New.
 	* gcc.dg/tree-ssa/pr81620-2.c: New.

gcc/testsuite/gcc.dg/tree-ssa/pr81627.c

+/* { dg-do run } */
+/* { dg-options "-O3 -fno-tree-loop-vectorize -fdump-tree-pcom-details" } */
+
+int a, b, c, d[6], e = 3, f;
+
+void abort (void);
+void fn1 ()
+{
+  for (b = 1; b < 5; b++)
+    {
+      for (c = 0; c < 5; c++)
+        d[b] = e;
+      if (a)
+        f++;
+      d[b + 1] = 1;
+    }
+}
+
+int main ()
+{
+  fn1 ();
+  if (d[0] != 0 || d[1] != 3 || d[2] != 3
+      || d[3] != 3 || d[4] != 3 || d[5] != 1)
+    abort ();
+
+  return 0;
+}
+/* { dg-final { scan-tree-dump-times "Store-stores chain" 1 "pcom" } } */

gcc/tree-predcom.c

@@ -2983,11 +2983,11 @@ prepare_finalizers (struct loop *loop, vec<chain_p> chains)
       if (prepare_finalizers_chain (loop, chain))
 	{
 	  i++;
-	  /* We don't corrupt loop closed ssa form for store elimination
-	     chain if eliminated stores only store loop invariant values
-	     into memory.  */
-	  if (!chain->inv_store_elimination)
-	    loop_closed_ssa |= (!chain->inv_store_elimination);
+	  /* Be conservative, assume loop closed ssa form is corrupted
+	     by store-store chain.  Though it's not always the case if
+	     eliminated stores only store loop invariant values into
+	     memory.  */
+	  loop_closed_ssa = true;
 	}
       else
 	{