[PATCH] Fix VRP register_edge_assert_for_1 (PR tree-optimization/59014)

[Jakub Jelinek]

Hi!

Given:
  _6 = (_Bool) a.1_5;
  _7 = _4 | _6;
  if (_7 != 0)
    goto <bb 5>;
  else
    goto <bb 6>;
where a.1_5 has int type and _6/_4/_7 are _Bool, register_edge_assert_for_1
happily inserts:
  <bb 6>:
  a.1_14 = ASSERT_EXPR <a.1_5, a.1_5 == 0>;
assertion, which is wrong, the fact that _6 is known to be 0 doesn't
imply that a.1_5 is zero, as there is a narrowing conversion.
We can only safely look through integer->integer conversions which
are widening or preserve precision.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

I'll try to create a testcase for 4.8 branch tomorrow.

2013-11-26  Jakub Jelinek  <ja...@redhat.com>

        PR tree-optimization/59014
        * tree-vrp.c (register_edge_assert_for_1): Don't look
        through conversions from non-integral types or through
        narrowing conversions.

        * gcc.c-torture/execute/pr59014.c: New test.

--- gcc/tree-vrp.c.jj   2013-11-22 21:03:03.000000000 +0100
+++ gcc/tree-vrp.c      2013-11-26 18:13:37.227600646 +0100
@@ -5434,9 +5434,13 @@ register_edge_assert_for_1 (tree op, enu
     }
   else if (CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (op_def)))
     {
-      /* Recurse through the type conversion.  */
-      retval |= register_edge_assert_for_1 (gimple_assign_rhs1 (op_def),
-                                           code, e, bsi);
+      /* Recurse through the type conversion, unless it is a narrowing
+        conversion or conversion from non-integral type.  */
+      tree rhs = gimple_assign_rhs1 (op_def);
+      if (INTEGRAL_TYPE_P (TREE_TYPE (rhs))
+         && (TYPE_PRECISION (TREE_TYPE (rhs))
+             <= TYPE_PRECISION (TREE_TYPE (op))))
+       retval |= register_edge_assert_for_1 (rhs, code, e, bsi);
     }
 
   return retval;
--- gcc/testsuite/gcc.c-torture/execute/pr59014.c.jj    2013-11-26 
18:15:06.274152877 +0100
+++ gcc/testsuite/gcc.c-torture/execute/pr59014.c       2013-11-26 
18:14:52.000000000 +0100
@@ -0,0 +1,25 @@
+/* PR tree-optimization/59014 */
+
+int a = 2, b, c, d;
+
+int
+foo ()
+{
+  for (;; c++)
+    if ((b > 0) | (a & 1))
+      ;
+    else
+      {
+       d = a;
+       return 0;
+      }
+}
+
+int
+main ()
+{
+  foo ();
+  if (d != 2)
+    __builtin_abort ();
+  return 0;
+}

        Jakub