re PR tree-optimization/21294 (Missed removal of null pointer check)

gcc/
	PR tree-optimization/21294
	* tree-vrp.c (vrp_expr_computes_nonzero): New.
	(extract_range_from_expr): Call vrp_expr_computes_nonzero.

testsuite/
	PR tree-optimization/21294
	* gcc.dg/tree-ssa/pr21294.c: New.

From-SVN: r99111

gcc/ChangeLog

+2005-05-02  Kazu Hirata  <kazu@cs.umass.edu>
+
+	PR tree-optimization/21294
+	* tree-vrp.c (vrp_expr_computes_nonzero): New.
+	(extract_range_from_expr): Call vrp_expr_computes_nonzero.
+
 2005-05-02  Janis Johnson  <janis187@us.ibm.com>
 
 	PR 19985

gcc/testsuite/ChangeLog

+2005-05-02  Kazu Hirata  <kazu@cs.umass.edu>
+
+	PR tree-optimization/21294
+	* gcc.dg/tree-ssa/pr21294.c: New.
+
 2005-05-02  Paolo Bonzini  <bonzini@gnu.org>
 
         * gcc.dg/altivec-3.c (vec_store): Do not use the old

gcc/testsuite/gcc.dg/tree-ssa/pr21294.c

+/* PR tree-optimization/21294
+   VRP did not notice that an address of the form &p->i is nonnull
+   when p is known to be nonnull.  In this testcase, noticing that
+   allows us to eliminate the second "if" statement.  */
+
+/* { dg-do compile } */
+/* { dg-options "-O2 -fno-tree-dominator-opts -fdump-tree-vrp-details" } */
+
+struct f {
+  int i;
+};
+
+int
+foo (struct f *p)
+{
+  if (p != 0)
+    if (&p->i != 0)
+      return 123;
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump-times "Folding predicate" 1 "vrp"} } */
+/* { dg-final { cleanup-tree-dump "vrp" } } */

gcc/tree-vrp.c

@@ -717,6 +717,35 @@ extract_range_from_binary_expr (value_range *vr, tree expr)
 }
 
 
+/* Like expr_computes_nonzero, but this function uses value ranges
+   obtained so far.  */
+
+static bool
+vrp_expr_computes_nonzero (tree expr)
+{
+  if (expr_computes_nonzero (expr))
+    return true;
+
+  /* If we have an expression of the form &X->a, then the expression
+     is nonnull if X is nonnull.  */
+  if (TREE_CODE (expr) == ADDR_EXPR)
+    {
+      tree base = get_base_address (TREE_OPERAND (expr, 0));
+
+      if (base != NULL_TREE
+	  && TREE_CODE (base) == INDIRECT_REF
+	  && TREE_CODE (TREE_OPERAND (base, 0)) == SSA_NAME)
+	{
+	  value_range *vr = get_value_range (TREE_OPERAND (base, 0));
+	  if (range_is_nonnull (vr))
+	    return true;
+	}
+    }
+
+  return false;
+}
+
+
 /* Extract range information from a unary expression EXPR based on
    the range of its operand and the expression code.  */
 
@@ -833,7 +862,7 @@ extract_range_from_expr (value_range *vr, tree expr)
     extract_range_from_binary_expr (vr, expr);
   else if (TREE_CODE_CLASS (code) == tcc_unary)
     extract_range_from_unary_expr (vr, expr);
-  else if (expr_computes_nonzero (expr))
+  else if (vrp_expr_computes_nonzero (expr))
     set_value_range_to_nonnull (vr, TREE_TYPE (expr));
   else if (TREE_CODE (expr) == INTEGER_CST)
     set_value_range (vr, VR_RANGE, expr, expr);