re PR tree-optimization/25382 (VRP does not get a range from BIT_AND_EXPR if the second operand is constant)

gcc/
	PR tree-optimization/25382.
	* tree-vrp.c (extract_range_from_binary_expr): Extract a range
	from BIT_AND_EXPR.

gcc/testsuite/
	PR tree-optimization/25382.
	* gcc.dg/tree-ssa/pr25382.c: New.

From-SVN: r108898

4 files changed, 66 insertions, 7 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 2423146..7c34089 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2005-12-21  Kazu Hirata  <kazu@codesourcery.com>
+
+	PR tree-optimization/25382.
+	* tree-vrp.c (extract_range_from_binary_expr): Extract a range
+	from BIT_AND_EXPR.
+
 2005-12-21  Janis Johnson  <janis187@us.ibm.com>
 	    Ben Elliston  <bje@au.ibm.com>
 
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 5b21ca8..090eaf8 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2005-12-21  Kazu Hirata  <kazu@codesourcery.com>
+
+	PR tree-optimization/25382.
+	* gcc.dg/tree-ssa/pr25382.c: New.
+
 2005-12-20  Richard Guenther  <rguenther@suse.de>
 
 	PR middle-end/24306
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr25382.c b/gcc/testsuite/gcc.dg/tree-ssa/pr25382.c
new file mode 100644
index 0000000..72277f9
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr25382.c
@@ -0,0 +1,19 @@
+/* PR tree-optimization/25382
+   VRP used to ignore BIT_AND_EXPRs for the purpose of distilling ranges.
+   Check that VRP now gets ranges from BIT_AND_EXPRs.  */
+
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-vrp" } */
+
+int
+foo (int a)
+{
+  int b = a & 0xff;
+  if (b > 300)
+    return 2;
+  else
+    return 1;
+}
+
+/* { dg-final { scan-tree-dump-times "Folding predicate b_.* > 300 to 0" 1 "vrp" } } */
+/* { dg-final { cleanup-tree-dump "vrp" } } */
diff --git a/gcc/tree-vrp.c b/gcc/tree-vrp.c
index 04353f5a..a9609fa 100644
--- a/gcc/tree-vrp.c
+++ b/gcc/tree-vrp.c
@@ -1184,6 +1184,7 @@ extract_range_from_binary_expr (value_range_t *vr, tree expr)
       && code != ROUND_DIV_EXPR
       && code != MIN_EXPR
       && code != MAX_EXPR
+      && code != BIT_AND_EXPR
       && code != TRUTH_ANDIF_EXPR
       && code != TRUTH_ORIF_EXPR
       && code != TRUTH_AND_EXPR
@@ -1220,13 +1221,16 @@ extract_range_from_binary_expr (value_range_t *vr, tree expr)
     }
 
   /* Refuse to operate on VARYING ranges, ranges of different kinds
-     and symbolic ranges.  TODO, we may be able to derive anti-ranges
-     in some cases.  */
-  if (vr0.type == VR_VARYING
-      || vr1.type == VR_VARYING
-      || vr0.type != vr1.type
-      || symbolic_range_p (&vr0)
-      || symbolic_range_p (&vr1))
+     and symbolic ranges.  As an exception, we allow BIT_AND_EXPR
+     because we may be able to derive a useful range even if one of
+     the operands is VR_VARYING or symbolic range.  TODO, we may be
+     able to derive anti-ranges in some cases.  */
+  if (code != BIT_AND_EXPR
+      && (vr0.type == VR_VARYING
+	  || vr1.type == VR_VARYING
+	  || vr0.type != vr1.type
+	  || symbolic_range_p (&vr0)
+	  || symbolic_range_p (&vr1)))
     {
       set_value_range_to_varying (vr);
       return;
@@ -1406,6 +1410,31 @@ extract_range_from_binary_expr (value_range_t *vr, tree expr)
       min = vrp_int_const_binop (code, vr0.min, vr1.max);
       max = vrp_int_const_binop (code, vr0.max, vr1.min);
     }
+  else if (code == BIT_AND_EXPR)
+    {
+      if (vr0.type == VR_RANGE
+	  && vr0.min == vr0.max
+	  && tree_expr_nonnegative_p (vr0.max)
+	  && TREE_CODE (vr0.max) == INTEGER_CST)
+	{
+	  min = fold_convert (TREE_TYPE (expr), integer_zero_node);
+	  max = vr0.max;
+	}
+      else if (vr1.type == VR_RANGE
+	  && vr1.min == vr1.max
+	  && tree_expr_nonnegative_p (vr1.max)
+	  && TREE_CODE (vr1.max) == INTEGER_CST)
+	{
+	  vr0.type = VR_RANGE;
+	  min = fold_convert (TREE_TYPE (expr), integer_zero_node);
+	  max = vr1.max;
+	}
+      else
+	{
+	  set_value_range_to_varying (vr);
+	  return;
+	}
+    }
   else
     gcc_unreachable ();