re PR tree-optimization/66894 (wrong code at -Os and above on x86_64-linux-gnu)

2015-07-16  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/66894
	* tree-vrp.c (register_edge_assert_for_2): Fix bad assumption
	about deriving NE_EXPR from truncated values.

	* gcc.dg/torture/pr66894.c: New testcase.

From-SVN: r225870

gcc/ChangeLog

+2015-07-16  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/66894
+	* tree-vrp.c (register_edge_assert_for_2): Fix bad assumption
+	about deriving NE_EXPR from truncated values.
+
 2015-07-16  Martin Liska  <mliska@suse.cz>
 
 	* alloc-pool.h

gcc/testsuite/ChangeLog

 2015-07-16  Richard Biener  <rguenther@suse.de>
 
+	PR tree-optimization/66894
+	* gcc.dg/torture/pr66894.c: New testcase.
+
+2015-07-16  Richard Biener  <rguenther@suse.de>
+
 	* gcc.dg/tree-ssa/pr21031.c: Adjust.
 
 2015-07-16  Uros Bizjak  <ubizjak@gmail.com>

gcc/testsuite/gcc.dg/torture/pr66894.c

+/* { dg-do run } */
+
+short a, b;
+
+int
+main ()
+{
+  for (; a != 1; a += 3)
+    {
+      int c = 0;
+      for (; c < 2; c++)
+	if (a)
+	  {
+	    char d = a;
+	    b = d ? 1 / d : 0; 
+	  }
+	else
+	  break;
+    }
+  return 0;
+}

gcc/tree-vrp.c

@@ -5382,13 +5382,11 @@ register_edge_assert_for_2 (tree name, edge e, gimple_stmt_iterator bsi,
 	    }
 	  else if (CONVERT_EXPR_CODE_P (code))
 	    {
-	      /* For truncating conversions require that the constant
-	         fits in the truncated type if we are going to record
+	      /* For truncating conversions we cannot record
 		 an inequality.  */
 	      if (comp_code == NE_EXPR
 		  && (TYPE_PRECISION (TREE_TYPE (name2))
-		      < TYPE_PRECISION (TREE_TYPE (name)))
-		  && ! int_fits_type_p (val, TREE_TYPE (name2)))
+		      < TYPE_PRECISION (TREE_TYPE (name))))
 		continue;
 	      cst = fold_convert (TREE_TYPE (name2), val);
 	    }