re PR tree-optimization/82291 (wrong code at -O3 on x86_64-linux-gnu)

2017-09-22  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/82291
	* tree-if-conv.c (predicate_mem_writes): Make sure to
	remove writes in blocks predicated with false.

	* gcc.dg/torture/pr82291.c: New testcase.

From-SVN: r253093

gcc/ChangeLog

 2017-09-22  Richard Biener  <rguenther@suse.de>
 
+	PR tree-optimization/82291
+	* tree-if-conv.c (predicate_mem_writes): Make sure to
+	remove writes in blocks predicated with false.
+
+2017-09-22  Richard Biener  <rguenther@suse.de>
+
 	* sese.c: Include cfganal.h.
 	(if_region_set_false_region): Remove.
 	(create_if_region_on_edge): Likewise.

gcc/testsuite/ChangeLog

+2017-09-22  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/82291
+	* gcc.dg/torture/pr82291.c: New testcase.
+
 2017-09-22  Sergey Shalnov  <sergey.shalnov@intel.com>
 
         * gcc.target/i386/avx512f-constant-set.c: New test.

gcc/testsuite/gcc.dg/torture/pr82291.c

+/* { dg-do run } */
+
+int a, c, d, *h;
+unsigned b;
+
+int *fn1 ()
+{ 
+  int *f[3], g = 0;
+  for (; g < 3; g++)
+    f[g] = &a;
+  if (--b > a)
+    { 
+      if (a > b)
+	d++;
+      return f[0];
+    }
+}
+
+void fn2 ()
+{ 
+  for (; c >= 0; --c)
+    { 
+      int j[] = { 0, 0, 0, 0, 0 };
+      int *k = fn1 ();
+      if (!k)
+	__builtin_abort ();
+      h = &j[4];
+    }
+}
+
+int main ()
+{ 
+  fn2 ();
+  if (d != 0)
+    __builtin_abort ();
+  return 0;
+}

gcc/tree-if-conv.c

@@ -2197,7 +2197,7 @@ predicate_mem_writes (loop_p loop)
       gimple *stmt;
       int index;
 
-      if (is_true_predicate (cond) || is_false_predicate (cond))
+      if (is_true_predicate (cond))
 	continue;
 
       swap = false;
@@ -2210,9 +2210,17 @@ predicate_mem_writes (loop_p loop)
       vect_sizes.truncate (0);
       vect_masks.truncate (0);
 
-      for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
+      for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi);)
+	{
 	  if (!gimple_assign_single_p (stmt = gsi_stmt (gsi)))
+	    ;
+	  else if (is_false_predicate (cond))
+	    {
+	      unlink_stmt_vdef (stmt);
+	      gsi_remove (&gsi, true);
+	      release_defs (stmt);
 	      continue;
+	    }
 	  else if (gimple_plf (stmt, GF_PLF_2))
 	    {
 	      tree lhs = gimple_assign_lhs (stmt);
@@ -2301,6 +2309,8 @@ predicate_mem_writes (loop_p loop)
 	      gimple_assign_set_rhs1 (stmt, ifc_temp_var (type, rhs, &gsi));
 	      update_stmt (stmt);
 	    }
+	  gsi_next (&gsi);
+	}
     }
 }