re PR c/51730 (autoconf 2.60 through 2.67 stdbool.h check fails with GCC 4.7)

2012-01-03  Richard Guenther  <rguenther@suse.de>

	PR middle-end/51730
	* fold-const.c (fold_comparison): Properly canonicalize
	tree offset and HOST_WIDE_INT bit position.

	* gcc.dg/fold-compare-6.c: New testcase.

From-SVN: r182830

gcc/ChangeLog

+2012-01-03  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/51730
+	* fold-const.c (fold_comparison): Properly canonicalize
+	tree offset and HOST_WIDE_INT bit position.
+
 2012-01-02  Uros Bizjak  <ubizjak@gmail.com>
 
 	* config/ia64/ia64.c (expand_vec_perm_broadcast): Use correct

gcc/fold-const.c

@@ -8886,6 +8886,14 @@ fold_comparison (location_t loc, enum tree_code code, tree type,
 	      indirect_base0 = true;
 	    }
 	  offset0 = TREE_OPERAND (arg0, 1);
+	  if (host_integerp (offset0, 0)
+	      && ((HOST_WIDE_INT) (TREE_INT_CST_LOW (offset0) * BITS_PER_UNIT)
+		  / BITS_PER_UNIT
+		  == (HOST_WIDE_INT) TREE_INT_CST_LOW (offset0)))
+	    {
+	      bitpos0 = TREE_INT_CST_LOW (offset0) * BITS_PER_UNIT;
+	      offset0 = NULL_TREE;
+	    }
 	}
 
       base1 = arg1;
@@ -8909,6 +8917,14 @@ fold_comparison (location_t loc, enum tree_code code, tree type,
 	      indirect_base1 = true;
 	    }
 	  offset1 = TREE_OPERAND (arg1, 1);
+	  if (host_integerp (offset1, 0)
+	      && ((HOST_WIDE_INT) (TREE_INT_CST_LOW (offset1) * BITS_PER_UNIT)
+		  / BITS_PER_UNIT
+		  == (HOST_WIDE_INT) TREE_INT_CST_LOW (offset1)))
+	    {
+	      bitpos1 = TREE_INT_CST_LOW (offset1) * BITS_PER_UNIT;
+	      offset1 = NULL_TREE;
+	    }
 	}
 
       /* A local variable can never be pointed to by

gcc/testsuite/ChangeLog

+2012-01-03  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/51730
+	* gcc.dg/fold-compare-6.c: New testcase.
+
 2012-01-03  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c++/51669

gcc/testsuite/gcc.dg/fold-compare-6.c

+/* { dg-do compile } */
+/* { dg-options "-fdump-tree-original" } */
+
+char digs[] = "0123456789";
+int foo (void)
+{
+  int xlcbug = 1 / (&(digs + 5)[-2 + (_Bool) 1] == &digs[4] ? 1 : -1);
+  return xlcbug;
+}
+
+/* { dg-final { scan-tree-dump "xlcbug = 1;" "original" } } */
+/* { dg-final { cleanup-tree-dump "original" } } */