re PR rtl-optimization/68217 (Wrong constant folding)

gcc/ChangeLog:

2016-07-29  Kugan Vivekanandarajah  <kuganv@linaro.org>

	PR middle-end/68217
	* tree-vrp.c (extract_range_from_binary_expr_1): In case of signed
	& sign-bit-CST, generate [-INF, 0] instead of [-INF, INF].


gcc/testsuite/ChangeLog:

2016-07-29  Kugan Vivekanandarajah  <kuganv@linaro.org>

	PR middle-end/68217
	* gcc.dg/pr68217.c: New test.

From-SVN: r238846

gcc/ChangeLog

+2016-07-29  Kugan Vivekanandarajah  <kuganv@linaro.org>
+
+	PR middle-end/68217
+	* tree-vrp.c (extract_range_from_binary_expr_1): In case of signed
+	& sign-bit-CST, generate [-INF, 0] instead of [-INF, INF].
+
 2016-07-28  Michael Meissner  <meissner@linux.vnet.ibm.com>
 
 	* config/rs6000/rs6000-protos.h (rs6000_split_vec_extract_var):

gcc/testsuite/ChangeLog

+2016-07-29  Kugan Vivekanandarajah  <kuganv@linaro.org>
+
+	PR middle-end/68217
+	* gcc.dg/pr68217.c: New test.
+
 2016-07-28  Steven G. Kargl  <kargl@gcc.gnu.org>
 
 	PR fortran/71067

gcc/testsuite/gcc.dg/pr68217.c

+
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-vrp1" } */
+
+int foo (void)
+{
+    volatile int a = -1;
+    long long b = (1LL << (sizeof (b) * 8 - 1)); // LLONG_MIN
+    long long x = (a & b); // x == 0x8000000000000000
+    if (x < 1LL) { ; } else { __builtin_abort(); }
+    return 0;
+}
+
+/* { dg-final { scan-tree-dump "\\\[-INF, 0\\\]" "vrp1" } } */

gcc/tree-vrp.c

@@ -3067,6 +3067,24 @@ extract_range_from_binary_expr_1 (value_range *vr,
 	  if (int_cst_range1 && tree_int_cst_sgn (vr1.min) >= 0)
 	    wmax = wi::min (wmax, vr1.max, TYPE_SIGN (expr_type));
 	  max = wide_int_to_tree (expr_type, wmax);
+	  cmp = compare_values (min, max);
+	  /* PR68217: In case of signed & sign-bit-CST should
+	     result in [-INF, 0] instead of [-INF, INF].  */
+	  if (cmp == -2 || cmp == 1)
+	    {
+	      wide_int sign_bit
+		= wi::set_bit_in_zero (TYPE_PRECISION (expr_type) - 1,
+				       TYPE_PRECISION (expr_type));
+	      if (!TYPE_UNSIGNED (expr_type)
+		  && ((value_range_constant_singleton (&vr0)
+		       && !wi::cmps (vr0.min, sign_bit))
+		      || (value_range_constant_singleton (&vr1)
+			  && !wi::cmps (vr1.min, sign_bit))))
+		{
+		  min = TYPE_MIN_VALUE (expr_type);
+		  max = build_int_cst (expr_type, 0);
+		}
+	    }
 	}
       else if (code == BIT_IOR_EXPR)
 	{